UA-45667900-1
Showing posts with label microglia. Show all posts
Showing posts with label microglia. Show all posts

Wednesday 19 September 2018

Ketones and Autism Part 5 - BHB, Histone Acetylation Modification, BDNF Expression, PKA, PKB/Akt, Microglial Ramification, Depression and Kabuki Syndrome















Child displaying elongated eyelids typical of Kabuki syndrome
Source: Given by Parents of children pictured with purpose of representing children with kabuki on Wikipedia. 

The syndrome is named after its resemblance to Japanese Kabuki makeup.

As we have discovered in this blog, autism is just a condition where certain genes are over-expressed and other genes are under-expressed. Put like that makes it sound quite simple.

Methylation of histones can either increase or decrease transcription of genes. The subject is highly complex, but we can keep things simple.

The child in the photo above has Kabuki syndrome and is likely to exhibit features of autism.  In most cases this is the result of a lack of expression of the KMT2D/MLL2 gene which encodes a protein called Histone-lysine N-methyltransferase.  Unfortunately, this is quite an important protein, because it promotes the “opening of chromatin”.  It adds a “trimethylation mark to H3K4”, just think of it as a pink post-it on your DNA. 
We get H3K4me3, which is an epigenetic marker (me3, because it is trimethylation). H3K4me3 promotes gene activation and it can cause a relative imbalance between open and closed chromatin states for critical genes. It has been suggested that it may be possible to restore this balance with drugs that promote open chromatin states, such as histone deacetylase inhibitors (HDACi).
What all this means is that people with Kabuki start with under-expression of just one gene, but this leads to the miss-expression of numerous other genes. Because science has figured out what the KMT2D/MLL2 gene does, we can find ways of treating this syndrome.

BHB as an HDAC inhibitor and a treatment for Kabuki syndrome

HDAC inhibitors (HDACi) are also suggested as therapies for other single gene syndromes. We saw in an earlier post that in Pitt Hopkins syndrome people lack Transcription Factor 4 (TCF4). Too little TC4 is not good, but too much TC4 is one feature of schizophrenia.
We saw in the research that we can increase expression of TCF4 using a class 1 HDAC inhibitor and we can also activate the Wnt pathway, which can also be achieved by inhibiting GSK3 (all themes covered in this blog).
So, Pitt Hopkins therapies include: -
·        Wnt activation (covered extensively in this blog) this includes statins and GSK3 inhibitors like Lithium

·        HDAC inhibitors like valproic acid, some cancer drugs, sodium butyrate and indeed the ketone BHB
This also means that people with schizophrenia, and likely too much TCF4, might benefit from the opposite gene expression modification, so a Wnt inhibitor, these include some cheap, safe, drugs used to treat children with parasites (Mebendazole/ Niclosamide etc) and of course GSK3 activators.
It is interesting that after 500 posts of this amateur blog you can start to fit the science together and identify rational therapies for complex disorders and  note that these therapies have much wider application, either to milder conditions or discovering avenues to treat the opposite genetic variation.  The underlying biological themes are all reoccurring in different types of autism/schizophrenia/ bipolar and you do wonder why more has not been done by professionals to apply this knowledge. 500 posts may sound a lot, but for autism researchers this is their paid, full-time job, not just a hobby pastime.

But then again, Simon Baron-Cohen, Head of Cambridge University's Autism Research Centre, recently published an article in which he wrote:

"We at the Autism Research Centre have no desire to cure, prevent or eradicate autism ... As scientists, our agenda is simply to understand the causes of autism." 

Whose team is he playing for?

My conclusion is that perhaps Baron-Cohen has Asperger's himself, because he does not realize that a disorder, severe enough for a medical/psychiatric diagnosis, is a bad thing that should be minimized and ideally prevented, just like any other brain disorder. His cousin the actor Sacha gives a very good impression of someone with bipolar, so perhaps they both need a Wnt activator?

Would a mother with Multiple Sclerosis (MS) want her daughter to also develop MS to share the experience? I think not. If it is just "quirky autism", it does not warrant a medical diagnosis, because it is perfectly okay to be quirky. 

This blog does have many Aspie readers who do want pharmacological therapy and that is their choice; I am fully supportive of them and wish them well.

Back to Kabuki
There is more than one type of HDAC and so there are different types of HDACi.  There are actually 18 HDAC enzymes divided into four classes
The ketone BHB inhibits HDAC class I enzymes called HDAC2 and HDAC3
The good news is that the ketogenic diet, which produces BHB, does indeed show merit as a therapy for Kabuki.

Kabuki syndrome is caused by haploinsufficiency for either of two genes that promote the opening of chromatin. If an imbalance between open and closed chromatin is central to the pathogenesis of Kabuki syndrome, agents that promote chromatin opening might have therapeutic potential. We have characterized a mouse model of Kabuki syndrome with a heterozygous deletion in the gene encoding the lysine-specific methyltransferase 2D (Kmt2d), leading to impairment of methyltransferase function. In vitro reporter alleles demonstrated a reduction in histone 4 acetylation and histone 3 lysine 4 trimethylation (H3K4me3) activity in mouse embryonic fibroblasts from Kmt2d+/βGeo mice. These activities were normalized in response to AR-42, a histone deacetylase inhibitor. In vivo, deficiency of H3K4me3 in the dentate gyrus granule cell layer of Kmt2d+/βGeo mice correlated with reduced neurogenesis and hippocampal memory defects. These abnormalities improved upon postnatal treatment with AR-42. Our work suggests that a reversible deficiency in postnatal neurogenesis underlies intellectual disability in Kabuki syndrome.

Intellectual disability is a common clinical entity with few therapeutic options. Kabuki syndrome is a genetically determined cause of intellectual disability resulting from mutations in either of two components of the histone machinery, both of which play a role in chromatin opening. Previously, in a mouse model, we showed that agents that favor chromatin opening, such as the histone deacetylase inhibitors (HDACis), can rescue aspects of the phenotype. Here we demonstrate rescue of hippocampal memory defects and deficiency of adult neurogenesis in a mouse model of Kabuki syndrome by imposing a ketogenic diet, a strategy that raises the level of the ketone beta-hydroxybutyrate, an endogenous HDACi. This work suggests that dietary manipulation may be a feasible treatment for Kabuki syndrome.
 Although BHB has previously been shown to have HDACi activity (7, 21), the potential for therapeutic application remains speculative. Here, we show that therapeutically relevant levels of BHB are achieved with a KD modeled on protocols that are used and sustainable in humans (22, 23). In addition, we demonstrate a therapeutic rescue of disease markers in a genetic disorder by taking advantage of the BHB elevation that accompanies the KD.
Our findings that exogenous BHB treatment lead to similar effects on neurogenesis as the KD support the hypothesis that BHB contributes significantly to the therapeutic effect. In our previous study (6), the HDACi AR-42 led to improved performance in the probe trial of the MWM for both Kmt2d+/βGeo and Kmt2d+/+ mice (genotype-independent improvement). In contrast, KD treatment only led to improvement in Kmt2d+/βGeo mice (genotype-dependent improvement). This discrepancy may relate to the fact that AR-42 acts as an HDACi but also affects the expression of histone demethylases (24), resulting in increased potency but less specificity. Alternatively, because the levels of BHB appear to be higher in Kmt2d+/βGeo mice on the KD, the physiological levels of BHB might be unable to reach levels in Kmt2d+/+ mice high enough to make drastic changes on chromatin.
In addition to the effects seen on hippocampal function and morphology, we also uncovered a metabolic phenotype in Kmt2d+/βGeo mice, which leads to both increased BHB/AcAc and lactate/pyruvate ratios during ketosis; an increased NADH/NAD+ ratio could explain both observations. This increased NADH/NAD+ ratio may relate to a previously described propensity of Kmt2d+/βGeo mice toward biochemical processes predicted to produce NADH, including beta-oxidation, and a resistance to high-fat-diet–induced obesity (27). If this exaggerated BHB elevation holds true in patients with KS, the KD may be a particularly effective treatment strategy for this patient population; however, this remains to be demonstrated. Alterations of the NADH/NAD+ ratio could also affect chromatin structure through the action of sirtuins, a class of HDACs that are known to be NAD+ dependent (28). Advocates of individualized medicine have predicted therapeutic benefit of targeted dietary interventions, although currently there are few robust examples (2931). This work serves as a proof-of-principle that dietary manipulation may be a feasible strategy for KS and suggests a possible mechanism of action of the previously observed therapeutic benefits of the KD for intractable seizure disorder (22, 23).                   
Kabuki syndrome (KS) (Kabuki make-up syndrome, Niikawa-Kuroki syndrome) is a rare genetic disorder first diagnosed in 1981. Kabuki make-up syndrome (KMS) is a multiple malformation/intellectual disability syndrome that was first described in Japan but is now reported in many other ethnic groups. KMS is characterized by multiple congenital abnormalities: craniofacial, skeletal, and dermatoglyphic abnormalities; intellectual disability; and short stature. Other findings may include: congenital heart defects, genitourinary anomalies, cleft lip and/or palate, gastrointestinal anomalies including anal atresia, ptosis and strabismus, and widely spaced teeth and hypodontia. The KS is associated with mutations in the MLL2 gene in some cases were also observed deletions of KDM6A. This study describes three children with autism spectrum disorders (ASDs) and KS and rehabilitative intervention that must be implemented.

So what?
Unless you know someone with Kabuki syndrome, you might be wondering what does this matter to autism.
What is shows is that BHB/KD is sufficiently potent to be a viable HDAC inhibitor. 
We know that some cancer drug HDAC inhibitors are effective in some mouse models of autism. But these drugs usually have side effects. 

HDAC Inhibitors for which Cancer/Autism? 

BHB is safe endogenous substance, so it is a “natural” HDACi. 

The effect of HDAC2 and HDAC3 on BDNF 
Brain derived neurotropic factor (BDNF) is like brain fertilizer. In some types of autism, you would like more BDNF.
When you exercise you produce BHB and that goes on to trigger the release of BDNF. This process also involves NF-kB activation

Exercise induces beneficial responses in the brain, which is accompanied by an increase in BDNF, a trophic factor associated with cognitive improvement and the alleviation of depression and anxiety. However, the exact mechanisms whereby physical exercise produces an induction in brain Bdnf gene expression are not well understood. While pharmacological doses of HDAC inhibitors exert positive effects on Bdnf gene transcription, the inhibitors represent small molecules that do not occur in vivo. Here, we report that an endogenous molecule released after exercise is capable of inducing key promoters of the Mus musculus Bdnf gene. The metabolite β-hydroxybutyrate, which increases after prolonged exercise, induces the activities of Bdnf promoters, particularly promoter I, which is activity-dependent. We have discovered that the action of β-hydroxybutyrate is specifically upon HDAC2 and HDAC3, which act upon selective Bdnf promoters. Moreover, the effects upon hippocampal Bdnf expression were observed after direct ventricular application of β-hydroxybutyrate. Electrophysiological measurements indicate that β-hydroxybutyrate causes an increase in neurotransmitter release, which is dependent upon the TrkB receptor. These results reveal an endogenous mechanism to explain how physical exercise leads to the induction of BDNF.

Results: ROS was significantly increased in neurons after 6 hours of ketone incubation. However, after 24 hours, neurons show improved efficiency in ATP productions, upregulated expressions of antioxidant enzyme SOD2, and enhanced resistance to excitotoxicity. These effects were significantly abolished in neurons after treatment with TrkB inhibitor. More interestingly, ROS scavengers or blocking ROS-dependent NF-kB activation significantly decreased ketone-dependent BDNF-upregulation in neurons, suggesting that ROS may have increased BDNF expressions to improve mitochondrial respiration as adaptive responses.
Conclusions: 3OHB initially generates ROS and poses oxidative stress. However, ROS appears to trigger adaptive responses against oxidative stress by upregulating BDNF through NF-kB activation, which can improve mitochondrial oxidative capacity and ultimately enhance neuroprotection
BHB/KD promotes PKA/CREB activation 
Another clever way to change the function/expression of multiple genes in one single step is to use a protein kinase.  Up to 30% of all human proteins may be modified by kinase activity.  
A protein kinase is an enzyme that modifies other proteins by chemically adding phosphate groups to them (phosphorylation). Phosphorylation usually results in a functional change of the target protein.
In the autism research you may well have come across PKA, PKB (Akt) and PKC. They clearly are disturbed in much autism.
The research shows that BHB activates PKA.
If you want good myelination you need PKA.
This might be another reason why BHB/KD is helpful in people with Multiple Sclerosis.
In much autism the myelin coating is found to be abnormally thin. 

BHB, Microglial Ramification and Depression (yes, depression)
I am increasingly impressed by research from China. The paper below by Chao Huang et al is excellent and I think we need a Chinese on the Dean’s List of this blog, it looks like he is the first.
Nantong, China on the Yangtze River and home to Chao Huang and more than 7 million other people 
Source: Wikipedia Dolly 442

The ketone body metabolite β-hydroxybutyrate induces an antidepression-associated ramification of microglia via HDACs inhibition-triggered Akt-small RhoGTPase activation. 


Abstract


Direct induction of macrophage ramification has been shown to promote an alternative (M2) polarization, suggesting that the ramified morphology may determine the function of immune cells. The ketone body metabolite β-hydroxybutyrate (BHB) elevated in conditions including fasting and low-carbohydrate ketogenic diet (KD) can reduce neuroinflammation. However, how exactly BHB impacts microglia remains unclear. We report that BHB as well as its producing stimuli fasting and KD induced obvious ramifications of murine microglia in basal and inflammatory conditions in a reversible manner, and these ramifications were accompanied with microglial profile toward M2 polarization and phagocytosis. The protein kinase B (Akt)-small RhoGTPase axis was found to mediate the effect of BHB on microglial shape change, as (i) BHB activated the microglial small RhoGTPase (Rac1, Cdc42) and Akt; (ii) Akt and Rac1-Cdc42 inhibition abolished the pro-ramification effect of BHB; (iii) Akt inhibition prevented the activation of Rac1-Cdc42 induced by BHB treatment. Incubation of microglia with other classical histone deacetylases (HDACs) inhibitors, but not G protein-coupled receptor 109a (GPR109a) activators, also induced microglial ramification and Akt activation, suggesting that the BHB-induced ramification of microglia may be triggered by HDACs inhibition. Functionally, Akt inhibition was found to abrogate the effects of BHB on microglial polarization and phagocytosis. In neuroinflammatory models induced by lipopolysaccharide (LPS) or chronic unpredictable stress (CUS), BHB prevented the microglial process retraction and depressive-like behaviors, and these effects were abolished by Akt inhibition. Our findings for the first time showed that BHB exerts anti-inflammatory actions via promotion of microglial ramification. 



NOTE:  Ramified Microglia = Resting Microglia


The brain microglia play important roles in sensing even subtle variations of their milieu. Upon moderate activation, they control brain activity via phagocytosis of cell debris and production of pro-inflammatory mediators and reactive oxygen species. However, a persistent activation would make the microglia transfer into a status with an amoeboid morphology tightly associated with neuronal damage and pro-inflammatory cytokine overproduction.

Unlike the activated microglia, the un-stimulated microglia are in a ramified status with extensively branched processes, an contribute to brain homeostasis via regulation of synaptic remodeling and neurotransmission. The ramified microglia has been shown to be associated with the induction of M2 polarization. A study by McWhorter et al. showed that elongation of macrophage by control of cell shape directly increases the expression of M2 markers and reduces the secretion of proinflammatory cytokines, suggesting that induction of microglial ramification may be a mechanism for regulation of microglial function. Methods that trigger microglial ramification may help treat brain disorders associated with neuroinflammation.
In this study, we found that BHB induces a functional ramification of murine microglia in both basal and inflammatory conditions in vitro and in vivo. The pro-ramification effects of BHB are associated with the change in microglial polarization and phagocytosis as well as the antidepressant-like effects of BHB in LPS- or chronic unpredictable stress (CUS)-stimulated mice. The ramified morphology in microglia is also induced by two BHB-producing stimuli fasting and KD, as well as two other HDACs inhibitors valproic acid (VPA) and trichostatin A (TSA). Given that microglial overactivation can mediate the pathogenesis of depression, induction of microglial ramification by BHB may have therapeutic significance in depression. 

These data confirm that BHB has an ability to transform the activated microglia back to their ramified and resting status in inflammatory conditions.

Recall the recent post about BHB and the Niacin Receptor HCA2/GPR109A in Autism:

The Chinese paper continues:

It is HDACs inhibition but not GPR109A activation that mediates the pro-ramification effect of BHB in microglia Akt inhibition abrogates the effects of BHB on microglial ramification, polarization, and phagocytosis
Akt inhibition prevents the antidepressant-like effects of BHB in acute and chronic depression models

Note that Akt is another name for Protein Kinase B (PKB)

One of the major findings in the present study is that the ketone body metabolite BHB as well as its producing stimuli fasting and KD induced reversible ramifications of murine microglia in vitro and in vivo, and these ramifications were not altered by pro-inflammatory stimuli. The ramified morphology induced by BHB seems to be a signal upstream of microglial polarization, and may mediate the antidepressant-like effect of BHB in depression induced by neuroinflammatory stimuli. Since the regulating effect of BHB in disorders associated with neuroinflammation has been well-documented, our findings provide a novel mechanism for the explanation of the neuroprotective effect of BHB in neurodegenerative and neuropsychiatric disorders from the aspect of the feedback regulation of microglial function by microglial ramification.
Induction of microglial ramification, a strategy neglected by most scientists for a long time, may have more important therapeutic significance than that of regulation of microglial polarization alone at the molecular level.

In experiments in vivo, we showed that BHB ameliorated the depressive-like behaviors induced by two neuroinflammatory stimuli LPS and CUS. These results are in accordance with previous reports, which showed that the BHB-producing stimuli, caloric restriction and fasting, produce potential antidepressant-like activities in both animals and humans. Thus, together with the pro-ramification effect of BHB in microglia in vitro, we speculate that the microglial shape change may be an independent signal that determines microglial function.

Our further analysis showed that the BHB-induced microglial ramification was mediated by the Rac1-Cdc42 signal, as BHB markedly increased the activity of Rac1 and Cdc42, and Rac1/Cdc42 inhibition attenuated the pro-ramification effect of BHB. The PI3K-Akt signal has been shown to mediate the activation of Rac1/Cdc42, and once accepting the signal from Akt, the Rac1-Cdc42 will be mobilized to promote lamellipodia/filopodia formation and cell shape change (Huang et al., 2016a). We showed that the BHB-induced microglial ramification was mediated by the Akt signal, as Akt inhibition suppressed the induction of microglial ramification by BHB. As a functional evidence for the involvement of Akt in the pro-ramification effect of BHB, Akt inhibition was found to block the functional changes in BHB-treated microglia in vitro and in vivo, including blockage of the anti-inflammatory and prophagocytic activity of BHB and abrogation of the antidepressant-like effects of BHB. Since the ramified morphology determines the anti-inflammatory phenotype in macrophages (McWhorter et al., 2013), our data suggest that there may exist a causal relationship between the ramified morphology and microglial function after BHB treatment, and this relationship may evidence the clinical significance of our findings, as the microglial process retraction has been shown to mediate the development of neurodegenerative and neuropsychiatric disorders.

Furthermore, considering the serum level of BHB in humans begin to rise to 6 to 8 mM with prolonged fasting (Cahill, 2006), investigation of whether the pro-ramification effect of BHB exists in human individuals should be of great value for the application of BHB in disease therapy. 


 Exposure to hypobaric hypoxia causes neuron cell damage, resulting in impaired cognitive function. Effective interventions to antagonize hypobaric hypoxia-induced memory impairment are in urgent need. Ketogenic diet (KD) has been successfully used to treat drug-resistant epilepsy and improves cognitive behaviors in epilepsy patients and other pathophysiological animal models. In the present study, we aimed to explore the potential beneficial effects of a KD on memory impairment caused by hypobaric hypoxia and the underlying possible mechanisms. We showed that the KD recipe used was ketogenic and increased plasma levels of ketone bodies, especially β-hydroxybutyrate. The results of the behavior tests showed that the KD did not affect general locomotor activity but obviously promoted spatial learning. Moreover, the KD significantly improved the spatial memory impairment caused by hypobaric hypoxia (simulated altitude of 6000 m, 24 h). In addition, the improving-effect of KD was mimicked by intraperitoneal injection of BHB. The western blot and immunohistochemistry results showed that KD treatment not only increased the acetylated levels of histone H3 and histone H4 compared to that of the control group but also antagonized the decrease in the acetylated histone H3 and H4 when exposed to hypobaric hypoxia. Furthermore, KD-hypoxia treatment also promoted PKA/CREB activation and BDNF protein expression compared to the effects of hypoxia alone. These results demonstrated that KD is a promising strategy to improve spatial memory impairment caused by hypobaric hypoxia, in which increased modification of histone acetylation plays an important role

Exogenous BHB prevents spatial memory impairment induced by hypobaric hypoxia

To further verify whether ketone body, a product of KD, has direct improving effect, we chose the most stable physiologic ketone body, BHB, for the subsequent experiment. In order to mimic the effect of KD as above described, the rats were pre-treated with BHB (at a dose of 200mg/kg/day) for 2 weeks and then submitted to Morris water maze test. Since intraperitoneal injection would allow substances to be absorbed at a slower rate and intraperitoneal injection would produce marginal effect during behavioral tests [16], we used the intraperitoneal injection of BHB, which has been applied in published reports [17, 18]. Although the rats in the control and BHB groups learned to find the platform with the same pattern during 5 days of acquisition training (Fig 4B), BHB could significantly improve the memory impairment induced by hypobaric hypoxia, represented by more crossing number, more time in the target quadrant, and decreased latency to first entry to platform compared to hypobaric hypoxia treatment alone (Fig 4C–4F). These results demonstrated that BHB has a direct memory-improving effect and served as the main executor of KD beneficial effects.

KD increases histone acetylation modification in the hippocampus

A previous study found that BHB is an endogenous HDAC inhibitor, and the KD recipe in our study substantially increased plasma levels of BHB. Then, we detected the effect of KD on histone acetylation in the hippocampus, which is responsible for learning and memory. As shown in Fig 5, the acetylated histone H3 (K9/K14), acetylated histone H3 (K14), and acetylated histone H4 (K12), were all increased in the hippocampus of the KD rats. Although the histone acetylation modifications listed above are decreased in hypoxia-treated rats, KD treatment could reverse the decreased levels of histone acetylation. The same pattern was displayed in the immunohistochemical staining, in which the hypoxia-induced decrease in acetylated histone H3 and acetylated histone H4 in the CA1 region of the hippocampus was reversed by KD treatment  

KD activates PKA/CREB signaling in the hippocampus

To explore a possible underlying mechanism of the beneficial effect of KD treatment on cognition, the activity of the PKA/CREB pathway in the four groups was also evaluated by western blot (Fig 7A). KD treatment was shown to not only increase the levels of PKA substrates and p-CREB (KD vs STD) but also reverse the decline in PKA substrates, p-CREB and CREB (KD-Hy vs STD-Hy). Although KD pre-treatment produced a partial restoration of PKA activity, p-CREB is nearly completely restore to its basic levels, which is may be account for its other upstream kinases, like calmodulin-dependent kinases [19]. Interestingly, the hypoxia-induced down-regulation of BDNF, a well-known neurotrophic factor involved in learning and memory formation processes, was also up-reregulated by KD treatment. These results demonstrated that KD treatment promoted PKA/CREB activation and BDNF protein expression. In order to detect whether KD promoted BDNF expression at mRNA levels, qRT-PCR assays were performed using BDNF specific primers. We found that KD-pretreatment significantly increased mRNA levels compared with that in hypobaric hypoxia group (Fig 7B). Next, we used ChIP-PCR to test if there might be increased enrichment of acetylated histones on the promoter of BDNF gene. We focused on the promoter I of BDNF gene, which response to neuronal activity [20). ]. The results showed that there is increased binding of acetylated histone H3 to the promoter I of BDNF gene (Fig 7C   

Concentrations of acetyl–coenzyme A and nicotinamide adenine dinucleotide (NAD+) affect histone acetylation and thereby couple cellular metabolic status and transcriptional regulation. We report that the ketone body d-β-hydroxybutyrate (βOHB) is an endogenous and specific inhibitor of class I histone deacetylases (HDACs). Administration of exogenous βOHB, or fasting or calorie restriction, two conditions associated with increased βOHB abundance, all increased global histone acetylation in mouse tissues. Inhibition of HDAC by βOHB was correlated with global changes in transcription, including that of the genes encoding oxidative stress resistance factors FOXO3A and MT2. Treatment of cells with βOHB increased histone acetylation at the Foxo3a and Mt2 promoters, and both genes were activated by selective depletion of HDAC1 and HDAC2. Consistent with increased FOXO3A and MT2 activity, treatment of mice with βOHB conferred substantial protection against oxidative stress. 
Abnormalities in mitochondrial function and epigenetic regulation are thought to be instrumental in Huntington's disease (HD), a fatal genetic disorder caused by an expanded polyglutamine track in the protein huntingtin. Given the lack of effective therapies for HD, we sought to assess the neuroprotective properties of the mitochondrial energizing ketone body, D-β-hydroxybutyrate (DβHB), in the 3-nitropropionic acid (3-NP) toxic and the R6/2 genetic model of HD. In mice treated with 3-NP, a complex II inhibitor, infusion of DβHB attenuates motor deficits, striatal lesions, and microgliosis in this model of toxin induced-striatal neurodegeneration. In transgenic R6/2 mice, infusion of DβHB extends life span, attenuates motor deficits, and prevents striatal histone deacetylation. In PC12 cells with inducible expression of mutant huntingtin protein, we further demonstrate that DβHB prevents histone deacetylation via a mechanism independent of its mitochondrial effects and independent of histone deacetylase inhibition. These pre-clinical findings suggest that by simultaneously targeting the mitochondrial and the epigenetic abnormalities associated with mutant huntingtin, DβHB may be a valuable therapeutic agent for HD.  

Conclusion
At the end of this fifth post on ketones and autism, I think we have established beyond any doubt that ketones can do some amazing things for numerous dysfunctions and diseases.
The question remains how much you need to achieve the various possible benefits. 
The next question, already put to me by one parent, is how do you measure such a benefit.  Some people’s idea of treating autism is just to eradicate disturbing behaviours like SIB and ensure a placid, cooperative child when out in public.  Other people notice small cognitive and speech changes, because they spend hours a day teaching their child. Small but significant cognitive improvement may not show up on autism rating scales.
You would expect a dose dependent response, so the more ketones the bigger the response, which suggests that the full Ketogenic Diet (KD) is the ultimate option.
A lot does seem to be possible just with BHB and C8 (caprylic acid) as supplements to a regular diet.
Adults with Alzheimer’s, or Huntington’s, or Multiple Sclerosis (MS) all stand to potentially benefit from ketone supplements.
Children/adults with certain single-gene autisms, not limited to Kabuki and Pitt Hopkins potentially should benefit from ketone supplements.
Interestingly, another benefit of BHB is on mood; it seems to make some people just feel much better, apparently all due to the effect on microglia. So perhaps autism parents who take antidepressants should try BHB instead.







Friday 30 March 2018

Autism and Aspartic Acid - N-acetylaspartate (NAA), AGC1, CREB and EAAT1/2



Aspartic acid is a metabolite of the sweetener Aspartame; not a surprise when you taste it

Today’s post is about the amino acid aspartic acid, which our reader Tyler has been supplementing. The short version of this post would answer the question should we all follow Tyler and supplement L-Aspartic acid? I guess the answer is that it is well worth a trial.
There is a great deal of complex science showing that aspartic acid is dysfunctional in autism, but we cannot prove that supplemental aspartic acid corrects these dysfunctions. Supplemental aspartic acid will have other effects and it may be these that are beneficial in Tyler’s case and possibly yours.
Correcting the core dysfunctions relating to Aspartic acid would be very helpful, if it were possible.  You could write an entire book just about the contents of today’s post, so for most people understanding all of it will take quite some time.

You can read Tyler’s many comments on this subject by entering the following into google.

       aspartate "site:epiphanyasd.blogspot.com"

This gives you a list of those posts, where he left comments on aspartate.
Then press the “crtl” key and the “f” key and this will find the mentions of “aspartate” in that post and its comments

Here are some comments.





Malate-Aspartate Shuttle
I wonder if the reason supplemental aspartic acid may help some people comes from something called the Malate-Aspartate Shuttle.  Now this does get complicated, but is links together many things we already know:-
·        Disturbed calcium channel signaling and excess physical calcium in autistic brains

·        Abnormal myelination

·        Oxidative stress

·        Mitochondrial abnormalities

·        Microglial activation

·        Disturbed BDNF, VEGF, CRH etc.

There is also a very interesting potential protective genetic variation (SLC25A12) that appears to protect some siblings from developing autism.
It appears that the excessive level of (cytosolic) Ca2+ increases the expression of AGC1 (the mitochondrial aspartate/ glutamate carrier number 1) via CREB (cAMP response element-binding protein).
CREB is a cellular transcription factor that regulates numerous genes including c-fos, BDNF, tyrosine hydroxylase, numerous neuropeptides (somatostatin, enkephalin, VGF, corticotropin-releasing hormone CRH, etc.), and genes involved in the circadian clock (PER1, PER2). 

For instance, multiple stimuli induce the phosphorylation of the cyclic AMP-responsive element-binding protein (CREB) at Ser-133, which recruits the CREB-binding protein (CBP) to gene promoters. CBP catalyses the acetylation of histones, leading to changes in chromatin structure that facilitate the recruitment of RNA polymerase II and the activation of gene-transcription programs that promote synapse development12,15.
In addition to stimulating CREB-dependent gene transcription, neuronal activity-dependent calcium influx into neurons triggers the dephosphorylation of the transcription factor myocyte enhancer factor 2 (MEF2) by calcineurin, disrupting the association of MEF2 with histone deacetylases and leading to the recruitment of CBP and the stimulation of gene transcription26. 


Neuronal activity that functions through CREB, MEF2 and multiple other activity-regulated transcription factors — including SRF, Fos27 and NPAS428 — induces the transcription of the genes encoding proteins that function directly at synapses, including Bdnf, Arc and Ube3A12,15.
For example, activity-regulated MEF2 by activating Arc suppresses the number of excitatory synapses26,29, whereas CREB and NPAS4, by activating Bdnf transcription, control the number of inhibitory synapses that form on excitatory neurons28,30.

CREB is down regulated in Alzheimer’s.
CREB proteins are activated by phosphorylation from various kinases, including PKA.
A number of existing drugs can raise or lower PKA levels in the body. 
You would want to raise PKA in Alzheimer’s and some autism.
If AGC1 is over-activated this could be corrected using a PKA inhibitor, but this is easier said than done.  PKA does very many different things.
PDE4 inhibitors used to treat asthma and COPD (Ibudilast and Daxas) raise PKA.
PDE4 inhibitors also reduce microglial activation. See the reference to gliosis below.
As our reader Nat knows, Ca2+ ions are the source of numerous problems in autism.  The route problem seems to be too much calcium released from the stores within each cell (endoplasmic reticulum) and/or faulty voltage gated calcium channels allowing Ca2+ to enter from outside the cell.
The malate-aspartate shuttle “functions to move reducing equivalents into the mitochondrial matrix in the form of malate, whereas the major mitochondrial output through this complex is aspartate”. Specifically, AGC1 moves cytoplasmic glutamate into mitochondria, while moving mitochondrially synthesized aspartate out. Without AGC1, brain mitochondrial glutamate import and aspartate export are crippled. Studies with AGC1 knockout mice showed a dramatic drop in brain aspartate levels, with a concomitant reduction in NAA (N-acetylaspartate) synthesis.
AGC1 activation increases mitochondrial metabolism and oxidative stress
Reduction in N-acetylaspartate (NAA) synthesis causes hypomyelination.
N-acetylaspartate (NAA) is synthesized from acetyl CoA and aspartate. NAA is very important in the brain; too little NAA causes reduced myelination (hypomyelination) which is a feature of autism. Studies show that NAA is reduced in the brains of young people with autism, but interestingly not in older people with autism.
In autism we expect to see activated AGC1 and reduced NAA
It does look like NAA is something you do not want to be deficient in, but you also do not want too much. NAA is synthesized from acetyl CoA and aspartate and without going into details you might just say, why not just add some extra aspartate, which you can buy as an OTC powder. 
There is a very more complex explanation, which comes back to aberrant calcium signaling being the demon of most autism. That would suggest:-
“Pharmacological treatments able to modulate extracellular Ca2+ entry, intracellular Ca2+ release from the endoplasmic reticulum or putative upstream immune mechanisms affecting either or both the pathways are, at least in principle, already available”

Overexpression of mitochondrial aspartate/glutamate carrier AGC1/ aralar1 (annoyingly, some research use the term  Aralar1 while others use AGC1) encoded by encoded by the SLC25A12, caused by excess calcium Ca2+ either from intracellular release from stores in the endoplasmic reticulum or extracellular Ca2+. Recall the post about Gargus’ theory that a key nexus in autism is the IPR3 receptor,  in the Endoplasmic Reticulum within each cell. He believes this is core defect in much autism.

Canavan disease is a rare condition caused by far too much NAA, a genetic error prevents the normal breakdown of NAA and this disrupts myelination leading to death in childhood.

Also part of the malate-aspartate shuttle we have GLutamate ASpartate Transporter (GLAST) or Excitatory Amino Acid Transporter 1 (EAAT1). We know that both glutamate transporters EAAT1 and EAAT2 are over-expressed in the cerebellum of post-mortem tissue from autism patients.  Because EAAT expression is controlled in part by the extracellular concentration of glutamate, it is possible that the EAAT overexpression is due to the increased glutamate concentration seen in plasma and spectroscopic studies.

Glutamate & Glutamine
Since I have mentioned glutamate, note that numerous studies show high levels of glutamate but low levels of its precursor glutamine in autism. Gliosis is one possible explanation. This connects with those activated microglia which are another recurring feature of autism:-


“An increase in gliosis, which is characterized by enhanced activation of astrocytes and microglia, has been observed in the brains of individuals with autism. Interestingly, Ortinski et al. have reported that activated astrocytes downregulate the expression of glutamine synthetase, whereby glutamate is converted into glutamine, which in turn results in reduced glutamine coupled with elevated glutamate. In addition, glutaminase, another enzyme related to glutamate/glutamine metabolism via its conversion of glutamine into glutamate, has been shown to be upregulated in activated microglia. Thus, it is tempting to assume that the process of gliosis generation may be related to the etiology of autism, as mediated by activated astrocytes and/or activated microglia, which may disturb the regulation of certain types of enzymes and thereby alter the metabolism of glutamate/glutamine. Taken together with previous findings, our results demonstrating glutamate/glutamine abnormalities in the plasma of individuals with autism may be indicative of a gliosis process in the autistic brain.

Amino Acids and the BBB
Amino acids are present inside the brain but some do not cross easily across the BBB. If they do not cross the BBB then taking a supplement is not going to help much.
This point is quite relevant because one study showed that arginine deprivation plays a key role in Alzheimer’s, but the mass media pointed out that taking arginine supplements is not going to help. Had they read this blog they would have known that if you want to increase arginine in the brain, you want to take citrulline. So citrulline for Alzheimer’s?  well worth investigating.  
The amino acid transporters that control the level in the brain are themselves disturbed in autism. So it may be that the level of many amino acids in autistic brains is disturbed, regardless of diet and what the blood/urine levels indicate.

Amino acid gradients between brain and plasma





Amino acid concentrations in plasma and brain. The plasma and CSF concentrations were grouped and the CSF-to-plasma ratio expressed as percent of the plasma. CSF concentrations are assumed to approximate brain ECF (54,102). With the exception of glutamine, the concentrations of all AAs in the ECF are much lower than the concentrations of AAs in plasma.


The concentrations of all naturally occurring AAs in the cerebral spinal fluid (CSF) (presumably similar to the extracellular fluid (ECF) of the brain), with the exception of glutamine, are 10% or less than the plasma concentrations (Fig. 4) (54). This situation cannot be explained by the consumption of AAs by brain because the arteriovenous differences across brain of most AAs are imperceptible (55–57), as are the arteriovenous differences of ammonia (NH4+), a byproduct of AA catabolism (58). These observations indicate that AAs leave the brain against a concentration gradient. From this it may be concluded that active (e.g., Na+-dependent) systems on the abluminal membrane have an important role in maintaining both homeostasis of brain AA content as well as the lower concentration in the extracellular fluid. Based on similar observations Bradbury wrote “there is a strong indirect argument in favor of the hypothesis that most AA must be moved against a concentration gradient from interstitial fluid to blood” (34).



The present view of the BBB is that cerebral endothelial cells participate actively in regulating the composition of brain extracellular fluid and the AA content of the brain. The luminal and abluminal membranes work in a complementary fashion with the Na+-dependent transport of AAs occurring at the abluminal membrane, and with facilitative transport at the luminal membrane, or, in the case of LNAAs, at both membranes (97).

Although the BBB determines the availability and therefore the brain content of essential AAs, astrocytes and neurons participate in maintaining the extracellular concentrations. Astrocytes and neurons have Na+-dependent transport systems capable of transporting NAAs and acidic AAs (98–100). These systems are actively involved in regulating AA concentrations in ECF and are especially important in the maintenance of low concentrations of neurotransmitter AAs such as glutamate, aspartate, and glycine. On the other hand, it now seems clear that the BBB also participates in the active regulation of brain ECF composition, and the abluminal membrane is especially important in this role.

Characteristics of L-citrulline transport through blood-brain barrier in the brain capillary endothelial cellline (TR-BBB cells)


Background

L-Citrulline is a neutral amino acid and a major precursor of L-arginine in the nitric oxide (NO) cycle. Recently it has been reported that L-citrulline prevents neuronal cell death and protects cerebrovascular injury, therefore, L-citrulline may have a neuroprotective effect to improve cerebrovascular dysfunction. Therefore, we aimed to clarify the brain transport mechanism of L-citrulline through blood-brain barrier (BBB) using the conditionally immortalized rat brain capillary endothelial cell line (TR-BBB cells), as an in vitro model of the BBB. 

Conclusions

Our results suggest that transport of L-citrulline is mainly mediated by LAT1 in TR-BBB cells. Delivery strategy for LAT1-mediated transport and supply of L-citrulline to the brain may serve as therapeutic approaches to improve its neuroprotective effect in patients with cerebrovascular disease.
Our results demonstrated that L-citrulline transport might be mainly mediated by LAT1 in TR-BBB cells. Understanding the transport characteristics of L-citrulline to the brain through BBB might contribute to the transport strategy for L-citrulline as a potential therapeutic agent for cerebrovascular diseases such as brain ischemia. 



Disturbed amino acid transporters and levels in blood/urine      

Since we know that the amino acid transporters that carry amino acids across the blood brain barrier are disturbed in autism what is the relevance of blood/urine tests and standard reference levels? Unless you lest amino acid levels in spinal fluid (i.e. within the central nervous system) do lab tests really help? You certainly need to be aware of their limitations.
So as you can see even the summary is highly complicated.
Very many things associated with aspartate are messed up in autism and Tyler finds his son benefits from L-aspartate supplementation.
We saw in an earlier post that NT girls had three times the level of excreted aspartic acid than NT boys and that people with autism had very low levels of excreted aspartic acid.
If you could fix the underlying problem with elevated Ca2+ as proposed by Gargus, you would solve the AGC1/NAA problem. It may be that by supplementing L-aspartate you do have an effect on the  malate-aspartate shuttle, even though there is no solid understanding of exactly how this occurs.







IP3R controls the release of calcium from the ER (Endoplasmic Reticulum inside each cell). In the brain, calcium is used to communicate information within and between neurons, and it activates a host of other cell functions, including ones regulating learning and memory, neuronal excitability and neurotransmitter release – areas known to be dysfunctional in ASD. It also causes the release of Protein Kinase C which then acts to change the function of numerous proteins (via phosphorylation) and trigger a series of signaling cascades.

Rapid progress in our understanding of macrostructural abnormalities in autism spectrum disorders (ASD) has occurred in recent years. However, the relationship between the integrity of neural tissue and neural function has not been previously investigated. Single-voxel proton magnetic resonance spectroscopy and functional magnetic resonance imaging of an executive functioning task was obtained in 13 high functioning adolescents and adults with ASD and 13 age-matched controls. The ASD group showed significant reductions in N-acetyl aspartate (NAA) in all brain regions combined and a specific reduction in left frontal cortex compared to controls. Regression analyses revealed a significant group interaction effect between frontal and cerebellar NAA. In addition, a significant positive semi-partial correlation between left frontal lobe NAA and frontal lobe functional activation was found in the ASD group. These findings suggest that widespread neuronal dysfunction is present in high functioning individuals with ASD. Hypothesized developmental links between frontal and cerebellar vermis neural abnormalities were supported, in that impaired neuronal functioning in the vermis was associated with impaired neuronal functioning in the frontal lobes in the ASD group. Furthermore, this study provided the first direct evidence of the relationship between abnormal functional activation in prefrontal cortex and neuronal dysfunction in ASD.
This study extended prior work in this area by establishing that neural abnormalities, which have been identified using 1H-MRS predominantly in younger and likely lower functioning autistic individuals), may also be present in a higher functioning broadly inclusive ASD sample. None of the individuals in our sample had IQs in the mentally retarded range and the sample included individuals with diagnoses in the less severe end of the autism spectrum; approximately 43% of the sample was diagnosed as PDD-NOS or Asperger’s disorder. 
Recent postmortem studies have identified neuroinflammation as a compelling potential pathological mechanism for reduced levels of NAA in individuals with ASD (Laurence and Fatemi, 2005; Vargas et al., 2005). Vargas and colleagues documented microglial activation in postmortem middle frontal gyrus, anterior cingulate, and cerebellar tissue, and in cerebral spinal fluid (CSF) of children and adults with autism. Laurence and Fatemi found increased glial fibrillary acidic protein in area 9, area 40 and the cerebellum in autism. Ongoing neuroinflammatory processes may produce alterations in brain tissue that would result in reduced NAA (secondary to cell loss or damage), as was observed in the current study. 
We found that high functioning individuals with ASD have reduced levels of NAA compared to age-matched controls. The most consistent area of abnormality was observed in the left middle frontal gyrus. In addition, the relationship between level of NAA in the frontal lobes and NAA in the cerebellar vermis differed between groups. These findings of biochemical alterations in ASD may reflect early brain growth dysregulation and ongoing neuroinflammatory processes. Reduced levels of NAA in ASD were also directly related to neurofunctional abnormalities observed in the FMRI study of executive functioning. This study is the first to directly link functional activation to neuronal integrity in ASD, and provides direct evidence that primary neuronal dysfunction, in addition to hypothesized aberrant neural connectivity leads to neurofunctional impairment in high functioning individuals with autism spectrum disorders. 


Atypical trajectory of brain growth in autism spectrum disorders (ASDs) has been recognized as a potential etiology of an atypical course of behavioral development. Numerous neuroimaging studies have focused on childhood to investigate atypical age-related change of brain structure and function, because it is a period of neuron and synapse maturation. Recent studies, however, have shown that the atypical age-related structural change of autistic brain expands beyond childhood and constitutes neural underpinnings for lifelong difficulty to behavioral adaptation. Thus, we examined effects of aging on neurochemical aspects of brain maturation using 3-T proton magnetic resonance spectroscopy (1H-MRS) with single voxel in the medial prefrontal cortex (PFC) in 24 adult men with non-medicated high-functioning ASDs and 25 age-, IQ- and parental-socioeconomic-background-matched men with typical development (TD). Multivariate analyses of covariance demonstrated significantly high N-acetylaspartate (NAA) level in the ASD subjects compared with the TD subjects (F=4.83, P=0.033). The low NAA level showed a significant positive correlation with advanced age in the TD group (r=−0.618, P=0.001), but was not evident among the ASD individuals (r=0.258, P=0.223). Fisher's r-to-z transformation showed a significant difference in the correlations between the ASD and TD groups (Z=−3.23, P=0.001), which indicated that the age–NAA relationship was significantly specific to people with TD. The current 1H-MRS study provided new evidence that atypical age-related change of neurochemical aspects of brain maturation in ASD individuals expands beyond childhood and persists during adulthood.



In conclusion, the present findings demonstrated an absence of typical age-related medial prefrontal NAA decrement in ASD individuals during adulthood. Such an atypical relationship between age and NAA levels might contribute to a significant NAA increase in the ASD subjects compared with the TD adults. Although future studies should examine potential localization of atypical age-related NAA change and longitudinal course of autistic NAA abnormality, the current study has provided a new suggestion with regard to a role of atypical age-related NAA changes in the pathophysiology of ASD.


An interesting way to increase NAA:-

Supplement 'boosts' brain power
"They were asked to be more active and cut down on unhealthy snacks and fizzy drinks. 

At the same time, they were given two capsules a day of the VegEPA supplement, which contains an omega-3 fatty acid called EPA.

Tests done at the end of the three-month study found the children showed an increase in reading age of well over a year, their handwriting became neater and more accurate and they paid more attention in class.

Brain scans which identified a chemical called N-Acetylaspartate (NAA) which is linked to the growth of nerve fibres in the brain also showed dramatic changes, said Professor Puri.

Although the children were encouraged to change their diet, there was no evidence they did this to any great extent, suggesting the improvements in the children were a result of the supplement.


Brain growth 

"In three months you might expect to see a small NAA increase.

"But we saw as much growth as you would normally see in three years.

"It was as if these were the brains of children three years older. It means you have more connections and greater density of nerve cells, in the same way a tree grows more branches."

The boys in the study showed the most improvement, he added.

Omega-3 fatty acids are found naturally in oily fish such as mackerel, salmon, herring and tuna or seeds such as flax, pumpkin and hemp.

A systematic review of fish oil supplements in children published by the Food Standards Agency last year found there were too many inconsistencies in current evidence to come to any conclusion.

Professor Puri said he believed that it was EPA specifically which conferred the benefits which was why studies of fish oil supplements which also contain a fatty acid called DHA showed confusing results.

He is now planning to carry out a larger placebo-controlled study.

Professor Robert Grimble, professor of nutrition at the University of Southampton said it was vital that larger studies were done to clarify the issue.

"My view is we can't come to any clear conclusion until a proper trial is done.

"These small bits of weak data just confuse the public. The FSA looked at this very carefully and I wouldn't contradict that until we have more evidence." 



N-Acetylaspartate (NAA) is employed as a non-invasive marker for neuronal health using proton magnetic resonance spectroscopy (MRS). This utility is afforded by the fact that NAA is one of the most concentrated brain metabolites and that it produces the largest peak in MRS scans of the healthy human brain. NAA levels in the brain are reduced proportionately to the degree of tissue damage after traumatic brain injury (TBI) and the reductions parallel the reductions in ATP levels. Because NAA is the most concentrated acetylated metabolite in the brain, we have hypothesized that NAA acts in part as an extensive reservoir of acetate for acetyl coenzyme A synthesis. Therefore, the loss of NAA after TBI impairs acetyl coenzyme A dependent functions including energy derivation, lipid synthesis, and protein acetylation reactions in distinct ways in different cell populations. The enzymes involved in synthesizing and metabolizing NAA are predominantly expressed in neurons and oligodendrocytes, respectively, and therefore some proportion of NAA must be transferred between cell types before the acetate can be liberated, converted to acetyl coenzyme A and utilized. Studies have indicated that glucose metabolism in neurons is reduced, but that acetate metabolism in astrocytes is increased following TBI, possibly reflecting an increased role for non-glucose energy sources in response to injury. NAA can provide additional acetate for intercellular metabolite trafficking to maintain acetyl CoA levels after injury. Here we explore changes in NAA, acetate, and acetyl coenzyme A metabolism in response to brain injury
N-acetylaspartate (NAA) is one of the most abundant brain metabolites and is highly concentrated in neurons, but it remains to be determined why neurons synthesize so much of this particular acetylated amino acid. Early research implicated NAA in lipid synthesis in the brain, especially during postnatal myelination.
NAA is synthesized from acetyl CoA and aspartate, and because of the exceptionally high concentration in the human brain (~10 mM) some proportion of acetyl CoA must be utilized to maintain NAA levels 
The primary mitochondrial aspartate-glutamate carrier expressed in brain, heart, skeletal muscle, and several other tissues is known as aralar1 (Del Arco et al., 2002), which is part of a larger complex that comprises the so-called mitochondrial malate-aspartate shuttle. The malate-aspartate shuttle functions to move reducing equivalents into the mitochondrial matrix in the form of malate, whereas the major mitochondrial output through this complex is aspartate. Specifically, aralar1 moves cytoplasmic glutamate into mitochondria, while moving mitochondrially synthesized aspartate out. Without aralar1, brain mitochondrial glutamate import and aspartate export are crippled. Studies with aralar1 knockout mice showed a dramatic drop in brain aspartate levels, with a concomitant reduction in NAA synthesis
The connection between a lack of aralar1 expression and dramatically reduced NAA synthesis has at least two potential explanations. First, as suggested by Jalil et al. (2005) it could be due to the lack of mitochondrial aspartate output, which in turn would limit substrate availability for microsomal Asp-NAT to synthesize NAA. The other possible explanation is that the lack of glutamate uptake into neuronal mitochondria prevents intramitochondrial aspartate synthesis via the aspartate aminotransferase reaction which converts glutamate and oxaloacetate into α-ketoglutarate and aspartate. In this case the lack of intramitochondrial aspartate synthesis would be the limiting factor in NAA synthesis, leading to decreases in NAA levels. It is also possible that both of these mechanisms are responsible for the large drop in NAA levels observed in aralar1-deficient mice. 
One of the more interesting outcomes of aralar1 deficiency in addition to the large decrease in brain NAA levels is hypomyelination (Jalil et al., 2005; Wibom et al., 2009). The hypomyelination is hypothesized to result from the lack of availability of NAA and this conclusion is supported by the fact that galactocerebrosides, one of the myelin lipid classes that are reduced in Canavan disease 

The more NAA the more creative? 

A broadly accepted definition of creativity refers to the production of something both novel and useful within a given social context. Studies of patients with neurological and psychiatric disorders and neuroimaging studies of healthy controls have each drawn attention to frontal and temporal lobe contributions to creativity. Based on previous magnetic resonance (MR) spectroscopy studies demonstrating relationships between cognitive ability and concentrations of N-acetyl-aspartate (NAA), a common neurometabolite, we hypothesized that NAA assessed in gray and white matter (from a supraventricular slab) would relate to laboratory measures of creativity. MR imaging and divergent thinking measures were obtained in a cohort of 56 healthy controls. Independent judges ranked the creative products of each participant, from which a “Composite Creativity Index” (CCI) was created. Different patterns of correlations between NAA and CCI were found in higher verbal ability versus lower verbal ability participants, providing neurobiological support for a critical “threshold” regarding the relationship between intelligence and creativity. To our knowledge, this is the first report assessing the relationship between brain chemistry and creative cognition, as measured with divergent thinking, in a cohort comprised exclusively of normal, healthy participants.
Exactly how does variation in NAA concentration affect brain activity in normals? A rapidly growing literature links NAA to intelligence, working memory, attention, and memory both in health and disease (Ross and Sachdev, 2004), but the mechanisms underlying these relationships remain elusive. In the adult brain, there is substantial evidence that NAA is a marker of mitochondrial functioning, is involved in myelin lipid turnover, participates in axonglial signaling, and may be involved in brain nitrogen balance (Moffett et al., 2007). Substantial basic research has yet to unravel the complex role that NAA plays in higher cognitive functioning, including creativity, beyond mere correlation.

NAA is synthesized from acetyl CoA and aspartate, so you would not want to be short of either.





From your high school biology you may recall a process called aerobic respiration which is how you mitochondria convert Glucose (fuel) into ATP (energy).

As you can see one step in this process is the production of Acetyl CoA.

If you are breathing, you must be making Acetyl CoA.  So perhaps a little extra aspartic acid might help produce more NAA.

In extreme cases a lack of the mitochondrial carrier protein Aralar1 will causes very low levels of NAA. 

Canavan disease is a rare condition caused by too much NAA, a genetic error prevents the normal breakdown of NAA and this disrupts myelination leading to death in childhood.

Even after all that, we do not know for sure why supplementing Aspartate works for Tyler. Making more NAA would be a nice explanation but Aspartate does stimulate NMDA receptors.  


Autism is a severe developmental disorder, whose pathogenetic underpinnings are still largely unknown. Temporocortical gray matter from six matched patient-control pairs was used to perform post-mortem biochemical and genetic studies of the mitochondrial aspartate/glutamate carrier (AGC), which participates in the aspartate/malate reduced nicotinamide adenine dinucleotide shuttle and is physiologically activated by calcium Ca2+. AGC transport rates were significantly higher in tissue homogenates from all six patients, including those with no history of seizures and with normal electroencephalograms prior to death. This increase was consistently blunted by the Ca2+ chelator ethylene glycol tetraacetic acid; neocortical Ca2+ levels were significantly higher in all six patients; no difference in AGC transport rates was found in isolated mitochondria from patients and controls following removal of the Ca2+-containing post mitochondrial supernatant. Expression of AGC1, the predominant AGC isoform in brain, and cytochrome c oxidase activity were both increased in autistic patients, indicating an activation of mitochondrial metabolism. Furthermore, oxidized mitochondrial proteins were markedly increased in four of the six patients. Variants of the AGC1-encoding SLC25A12 gene were neither correlated with AGC activation nor associated with autism-spectrum disorders in 309 simplex and 17 multiplex families, whereas some unaffected siblings may carry a protective gene variant. Therefore, excessive Ca2+ levels are responsible for boosting AGC activity, mitochondrial metabolism and, to a more variable degree, oxidative stress in autistic brains. AGC and altered Ca2+ homeostasis play a key interactive role in the cascade of signaling events leading to autism: their modulation could provide new preventive and therapeutic strategies.

Evidence linking altered energy metabolism to autistic disorder has been available for some time, including peripheral markers, such as increased plasma lactate levels, and rare instances of association between respiratory chain disorders and autism.  Interest in assessing the role of mitochondria

in this disorder has been revitalized by the association between autism and variants of the SLC25A12 gene, which encodes the predominant isoform of the mitochondrial aspartate (asp)/glutamate (glu) carrier (AGC) in brain.15,16 AGC belongs to a family of integral proteins that catalyze the transport of metabolites and cofactors across the inner mitochondrial membrane.17 In particular, AGC is important in energy metabolism

by transporting glutamate into mitochondria in exchange for matrix aspartate, a key regulatory step in the malate/aspartate reduced nicotinamide adenine dinucleotide (NADH) shuttle.18,19 Its two

isoforms, AGC1 and AGC2, also named aralar(1) and citrin, are encoded by the SLC25A12 and SLC25A13 genes, located on human chromosomes 2q24 and 7q21.3, respectively.19 AGC1 and AGC2 expression overlaps during early prenatal life, but diverges beginning in late gestation and into adulthood, with AGC1 predominantly expressed in the brain, heart and skeletal muscle, whereas AGC2 is mainly expressed in liver and kidney.20,21 In the CNS, AGC1 is highly expressed in neurons, whereas glial cells express both isoforms at much lower levels.20,21 Importantly, AGC activity is regulated by intracellular calcium (Ca2+) through four ‘EF-hand’ domains22 located at its N-terminus, hanging into the intermembrane

space.18,19 As Ca2+ concentrations in the mitochondrial intermembrane space and cytosol are in equilibrium, cytosolic Ca2+ can rapidly activate AGC transport, thereby increasing the NADH/NAD ratio in the mitochondrial matrix and consequently boosting electron flow through the respiratory

chain and adenosine triphosphate (ATP) generation by oxidative phosphorylation.18,19,23 Through this mechanism, AGC1 is important in the transduction of small Ca2+ signals to neuronal mitochondria.19 An

excessive amplitude and/or duration of Ca2+ spikes leading to AGC activation can, however, contribute to the formation of reactive oxygen species (ROS) and to oxidative stress.24 Genetic and/or environmental

factors could thus interfere with neuronal ATP production and with oxidative stress by affecting the AGC1 carrier, either directly or through Ca2+ homeostasis.



===================

Results

AGC activity is boosted by excessive Ca2+ levels in autistic brains

AGC activity, normalized by CS activity to adjust for differences in absolute mitochondria tissue content, displays a prominent threefold increase in neocortical homogenates from nonsyndromic autistic patients compared to matched controls in all six pairs (Wilcoxon’s test: Z=

2.201, P<0 .05="" 1a="" a="" agc1="" ca="" figure="" increase="" instead="" left="" levels="" modest="" nonsignificant="" only="" protein="" s1="" show="" sup="" upplementary="" very="">2+
chelation by EGTA reduces asp/glu exchange rates to a much larger extent in patients than in controls (2.1- vs 0.35-fold, respectively), reducing case–control differences to only 36.1% (Figure 1a, middle). No difference between patients and controls is anymore detectable upon reconstitution of protein extracts from isolated mitochondria (P=0.17; Figure 1a, right). These results strongly point toward excessive Ca2+ concentrations as most likely responsible for increased asp/glu exchange rates in the brains of autistic patients.



AGC activation increases mitochondrial metabolism and oxidative stress

By increasing the availability of reducing equivalents in the mitochondrial matrix through AGC, enhanced cytosolic Ca2+ can be predicted to steadily boost mitochondrial metabolism and oxidative phosphorylation.18,19,23 Indeed, transcript amounts of the mitochondrial phosphate carrier (PiC), AGC1, and AGC2 (expressed at much lower levels compared to AGC1), are all increased (Supplementary Figure S2). Also COX activity is elevated to a similar extent in all six autistic patients compared to their matched controls (P<0 .05="" 3a="" figure="" span=""> 

No evidence of SLC25A12 gene contributions to autism vulnerability

Sequencing of the AGC1-encoding SLC25A12 cDNA and genomic DNA in these same six case–control pairs does not detect any nonsynonymous coding mutation
Figure 2 Calcium levels measured directly in the post mitochondrial supernatant by fluorimetry. (a) Calcium concentrations are significantly higher in the neocortical tissue of autism-spectrum disorder (ASD) patients compared to matched controls 

A SLC25A12 gene variant may confer protection in unaffected siblings

Single-marker analyses point toward the possible existence of a protective SLC25A12 gene variant preferentially transmitted from heterozygous parents to unaffected siblings of autistic patients.

The allele frequency of this haplotype is estimated at approximately 23–26% (Table 2b), making it a relatively common variant among unaffected siblings.
This study reports increased asp/glu exchange rates and significantly higher Ca2+ concentrations in postmortem neocortical tissue specimens of six nonsyndromic autistic patients compared to age-, sex- and PMI-matched controls. Altogether, our results strongly support excessive Ca2+ levels as primarily responsible for the observed activation of asp/glu exchange rates, whereas genetic contributions appear neither widespread nor necessary, at least in our postmortem and genetic samples.
Most importantly, direct measurements of neocortical Ca2+ concentrations clearly demonstrate a significant elevation of neocortical Ca2+ levels in all autistic patients compared to controls (Figure 2a)
Increased AGC transport rates, COX activities and Ca2+ levels consistently recorded in all six neocortical specimens from ASD patients crossvalidate each other, confirming the reliability and biological significance of these findings
In summary, altered Ca2+ homeostasis is the only factor shared by all autistic cortical tissue samples (Figure 2a), able to boost AGC activity,18,19,23 and previously linked to the pathogenesis of autism per se.
The existence of altered Ca2+ signaling in autism has been suggested in recent years by several lines of research.42 Gain-of-function mutations in the L-type voltage-gated Ca2+ channel Cav1.2 (CACNA1C) cause Timothy syndrome, a multisystem disorder including mental retardation and autism.43 Similarly, mutations in the L-type voltage-gated Ca2+ channel Cav1.4 (CACNA1F) cause the incomplete form of X-linked congenital stationary night blindness (CSNB2): gain-of-function mutations cause CSNB2 frequently accompanied by cognitive impairment and either autism or epilepsy, whereas CSNB2 due to lossof-function mutations is not accompanied by these symptoms.44 All of these gain-of-function mutations prevent voltage-dependent channel inactivation leading to excessive Ca2+ influx. Also mutations indirectly yielding increased cytosolic Ca2+ levels or amplifying intracellular Ca2+ signaling by hampering Ca2+-activated negative feedback mechanisms have been found associated with autism.42,45 The bioelectrical instability resulting from these mutations nicely parallels the high prevalence of seizures and/or EEG abnormalities present among autistic individuals 
We are currently in the process of correlating AGC activity and levels of oxidative stress with markers of immune activation, measured in the same tissue specimens assessed in this study. 
The present results can potentially pave the path to targeted preventive and therapeutic strategies. One important example is represented by thimerosal, an ethyl-mercury compound used as a preservative in vaccines.59,60 Thimerosal has drawn attention following initial anecdotal reports by some parents linking vaccinations to behavioral regression and to the onset of autism in their child within a matter of days or few weeks. Thimerosal is a Ca2+-mobilizing agent, capable of releasing Ca2+ from intracellular stores and increasing Ca2+ entry.61 Despite its short half-life compared to inorganic mercury, it undergoes preferential accumulation in the CNS, affecting the microglia and producing strain-dependent neurotoxic effects in rodents.62,63 This strain dependency, in conjunction with the present data, suggests that thimerosal could contribute to produce an unbalanced Ca2+ homeostasis in genetically vulnerable individuals. Indeed, a postnatal exposure to thimerosal is not reconcilable with the prenatal onset of neurodevelopmental anomalies leading to autism. Also large retrospective epidemiological studies confirm that thimerosal neither causes autism, nor provides large-scale contributions to its pathogenesis.2,60 However, our results suggest that thimerosal could conceivably precipitate an abrupt onset in a subset of children who would have otherwise developed autistic symptoms more insidiously. At the same time, we cannot exclude that thimerosal and other Ca2+-mobilizing environmental factors could also push genetically vulnerable individuals along the autism-spectrum toward more severe forms of the disease. On the basis of the present study, the elimination of thimerosal from vaccines, undertaken in the United States and Canada, is a well-justified safety measure. 

Pharmacological treatments able to modulate extracellular Ca2+ entry, intracellular Ca2+ release from the endoplasmic reticulum or putative upstream immune mechanisms affecting either or both the pathways are, at least in principle, already available. However, caution should be exercised in translating the present findings into therapeutic interventions prior to at least one replication in an independent cohort of brain samples and to assessments of Ca2+ homeostasis in vivo. 
Pharmacologically reducing Ca2+ entry into cells or blunting the oxidative damage produced by AGC activation seemingly represent more amenable and less dangerous therapeutic strategies. It is nonetheless difficult to predict the actual efficacy of treatments initiated during childhood on pathogenetic mechanisms active since early prenatal development. In this regard, the identification and functional characterization of protective SLC25A12 gene variants, if existent, could provide additional critical information on the contribution of AGC activation and oxidative stress to autism pathogenesis.

=======================

This study reports increased asp/glu exchange rates and significantly higher Ca2+ concentrations in postmortem neocortical tissue specimens of six nonsyndromic autistic patients compared to age-, sex- and PMI-matched controls. Altogether, our results strongly support excessive Ca2+ levels as primarily responsible for the observed activation of asp/glu exchange rates, whereas genetic contributions appear neither widespread nor necessary, at least in our postmortem and genetic samples.

Our results point toward the possible existence of a protective SLC25A12 gene variant in a sizable group of unaffected siblings. This cannot be conclusively demonstrated with our sample size of 104 families including one or more unaffected sibling.

On the other hand, our results would provide further support for key contributions of Ca2+-triggered AGC1 activity to autism pathogenesis. Increased asp/glu exchange rates provide more reducing equivalents (that is, NADH) to the respiratory chain and could foster oxidative stress,24 which was previously found increased measuring peripheral markers in autism.55 Also overexpression of AGC1 in cell culture has been recently found associated with a biphasic response, characterized initially by enhanced neurite outgrowth, which subsequently slows down and ends in early cell death.56 This response is seemingly compatible with an initial overproduction of ATP paralleled by a progressive build up of oxidative stress leading to cell damage. Oxidative stress, in addition to lipid and protein oxidation,55 can also produce genomic instability and stimulate cell cycle progression, pathophysiological events likely to be important in autism pathogenesis9,57,58 In this regard, the interindividual variability in oxidative damage reported in our study is not at all surprising, as the balance between ROS production and antioxidant agents leaves ample room for genetic and environmental influences

The present results can potentially pave the path to targeted preventive and therapeutic strategies. One important example is represented by thimerosal, an ethyl-mercury compound used as a preservative in vaccines.59,60 Thimerosal has drawn attention following initial anecdotal reports by some parents linking vaccinations to behavioral regression and to the onset of autism in their child within a matter of days or few weeks. Thimerosal is a Ca2+-mobilizing agent, capable of releasing Ca2+ from intracellular stores and increasing Ca2+ entry.61 Despite its short half-life compared to inorganic mercury, it undergoes preferential accumulation in the CNS, affecting the microglia and producing strain-dependent neurotoxic effects in rodents.62,63 This strain dependency, in conjunction with the present data, suggests that thimerosal could contribute to produce an unbalanced Ca2+ homeostasis in genetically vulnerable individuals. Indeed, a postnatal exposure to thimerosal is not reconcilable with the prenatal onset of neurodevelopmental anomalies leading to autism.

Also large retrospective epidemiological studies confirm that thimerosal neither causes autism, nor provides large-scale contributions to its pathogenesis. 2,60 However, our results suggest that thimerosal could conceivably precipitate an abrupt onset in a subset of children who would have otherwise developed autistic symptoms more insidiously. At the same time, we cannot exclude that thimerosal and other Ca2+-mobilizing environmental factors could also push genetically vulnerable individuals along the autism-spectrum toward more severe forms of the disease. On the basis of the present study, the elimination of thimerosal from vaccines, undertaken in the United States and Canada, is a well-justified safety measure.

Pharmacological treatments able to modulate extracellular Ca2+ entry, intracellular Ca2+ release from the endoplasmic reticulum or putative upstream immune mechanisms affecting either or both the pathways are, at least in principle, already available. However, caution should be exercised in translating the present findings into therapeutic interventions prior to at least one replication in an independent cohort of brain samples and to assessments of Ca2+ homeostasis in vivo. In particular, our findings in no way support the use of Ca2+ chelation as a therapeutic approach in autism. Ca2+ chelation has not only been purported of benefit in few anecdotal reports and small-sized open trials, but also carries a substantial risk to produce hypocalcemia, resulting in recent deaths of autistic children.64,65 Pharmacologically reducing Ca2+ entry into cells or blunting the oxidative damage produced by AGC activation seemingly represent more amenable and less dangerous therapeutic strategies. It is nonetheless difficult to predict the actual efficacy of treatments initiated during childhood on pathogenetic mechanisms active since early prenatal development. In this regard, the identification and functional characterization of protective SLC25A12 gene variants, if existent, could provide additional critical information on the contribution of AGC activation and oxidative stress to autism pathogenesis.



Solute carrier family 1 (glial high-affinity glutamate transporter), member 3, also known as SLC1A3, is a protein that, in humans, is encoded by the SLC1A3 gene.[5] SLC1A3 is also often called the GLutamate ASpartate Transporter (GLAST) or Amino Acid Transporter 1 (EAAT1) Excitatory.

GLAST is predominantly expressed in the plasma membrane, allowing it to remove glutamate from the extracellular space.[6] It has also been localized in the inner mitochondrial membrane as part of the malate-aspartate shuttle.[7]



VERY thorough but rather complex

N-Acetylaspartate (NAA) is employed as a non-invasive marker for neuronal health using proton magnetic resonance spectroscopy (MRS). This utility is afforded by the fact that NAA is one of the most concentrated brain metabolites and that it produces the largest peak in MRS scans of the healthy human brain. NAA levels in the brain are reduced proportionately to the degree of tissue damage after traumatic brain injury (TBI) and the reductions parallel the reductions in ATP levels. Because NAA is the most concentrated acetylated metabolite in the brain, we have hypothesized that NAA acts in part as an extensive reservoir of acetate for acetyl coenzyme A synthesis. Therefore, the loss of NAA after TBI impairs acetyl coenzyme A dependent functions including energy derivation, lipid synthesis, and protein acetylation reactions in distinct ways in different cell populations. The enzymes involved in synthesizing and metabolizing NAA are predominantly expressed in neurons and oligodendrocytes, respectively, and therefore some proportion of NAA must be transferred between cell types before the acetate can be liberated, converted to acetyl coenzyme A and utilized. Studies have indicated that glucose metabolism in neurons is reduced, but that acetate metabolism in astrocytes is increased following TBI, possibly reflecting an increased role for non-glucose energy sources in response to injury. NAA can provide additional acetate for intercellular metabolite trafficking to maintain acetyl CoA levels after injury. Here we explore changes in NAA, acetate, and acetyl coenzyme A metabolism in response to brain injury.
N-acetylaspartate (NAA) is one of the most abundant brain metabolites and is highly concentrated in neurons, but it remains to be determined why neurons synthesize so much of this particular acetylated amino acid. Early research implicated NAA in lipid synthesis in the brain, especially during postnatal myelination.
Subsequently it was discovered that mutations in the gene for the enzyme that deacetylates NAA, known as aspartoacylase or ASPA, lead to the fatal neurodegenerative disorder known as Canavan disease.
One line of research has focused on the lack of catabolism leading to a toxic buildup of NAA in the brain as the primary etiological component. Another line of research has suggested that the lack of catabolism results in an acetate deficiency in oligodendrocytes during brain development that subsequently limits acetyl coenzyme A (acetyl CoA) availability during this critical period of myelination. There is experimental support for both mechanisms, and it is possible that both are operative.
The loss of NAA after TBI is paralleled by a loss of ATP, acetyl CoA, and other metabolites associated with energy metabolism (Vagnozzi et al., 2007) indicating a substantial impact on neuroenergetics. The connections between NAA and brain energy metabolism are not entirely clear
NAA is synthesized from acetyl CoA and aspartate, and because of the exceptionally high concentration in the human brain (~10 mM) some proportion of acetyl CoA must be utilized to maintain NAA levels, and that proportion may change with brain injury. Signoretti and colleagues have shown that severe brain injury results in a very rapid drop in NAA levels that is paralleled by a similar reduction in ATP levels, suggesting that NAA is utilized rapidly in response to injury

NAA Synthesis and the Mitochondrial Malate-Aspartate Shuttle

The malate-aspartate shuttle functions to move reducing equivalents into the mitochondrial matrix in the form of malate, whereas the major mitochondrial output through this complex is aspartate. Specifically, aralar1 moves cytoplasmic glutamate into mitochondria, while moving mitochondrially synthesized aspartate out. Without aralar1, brain mitochondrial glutamate import and aspartate export are crippled.

The connection between a lack of aralar1 expression and dramatically reduced NAA synthesis has at least two potential explanations. First, as suggested by Jalil et al. (2005) it could be due to the lack of mitochondrial aspartate output, which in turn would limit substrate availability for microsomal Asp-NAT to synthesize NAA. The other possible explanation is that the lack of glutamate uptake into neuronal mitochondria prevents intramitochondrial aspartate synthesis via the aspartate aminotransferase reaction which converts glutamate and oxaloacetate into α-ketoglutarate and aspartate. In this case the lack of intramitochondrial aspartate synthesis would be the limiting factor in NAA synthesis, leading to decreases in NAA levels. It is also possible that both of these mechanisms are responsible for the large drop in NAA levels observed in aralar1-deficient mice. One of the more interesting outcomes of aralar1 deficiency in addition to the large decrease in brain NAA levels is hypomyelination


NAA and Lipid Synthesis 


Neurons provide key metabolites to their ensheathing oligodendrocytes for the purposes of myelination, myelin maintenance, and myelin sheath repair, including choline, palmitate, acetate, phosphate, and ethanolamine (Ledeen, 1984). NAA is among the trophic neuronally derived metabolites that are transferred to oligodendrocytes for use in myelination and myelin repair.

The synthesis of NAA requires the utilization of existing acetyl CoA and therefore NAA synthesis consumes a portion of brain acetyl CoA stores. Therefore NAA may be acting as a storage and transport form of acetate in the CNS that can be used for subsequent de novo synthesis of acetyl CoA, especially in oligodendrocytes


Inhibit AGC1?


The mitochondrial aspartate-glutamate carrier isoform 1 (AGC1) catalyzes a Ca2+-stimulated export of aspartate to the cytosol in exchange for glutamate, and is a key component of the malate-aspartate shuttle which transfers NADH reducing equivalents from the cytosol to mitochondria. By sustaining the complete glucose oxidation, AGC1 is thought to be important in providing energy for cells, in particular in the CNS and muscle where this protein is mainly expressed. Defects in the AGC1 gene cause AGC1 deficiency, an infantile encephalopathy with delayed myelination and reduced brain N-acetylaspartate (NAA) levels, the precursor of myelin synthesis in the CNS. Here, we show that undifferentiated Neuro2A cells with down-regulated AGC1 display a significant proliferation deficit associated with reduced mitochondrial respiration, and are unable to synthesize NAA properly. In the presence of high glutamine oxidation, cells with reduced AGC1 restore cell proliferation, although oxidative stress increases and NAA synthesis deficit persists. Our data suggest that the cellular energetic deficit due to AGC1 impairment is associated with inappropriate aspartate levels to support neuronal proliferation when glutamine is not used as metabolic substrate, and we propose that delayed myelination in AGC1 deficiency patients could be attributable, at least in part, to neuronal loss combined with lack of NAA synthesis occurring during the nervous system development.




Abstract

Ca2+ signaling in mitochondria is important to tune mitochondrial function to a variety of extracellular stimuli. The main mechanism is Ca2+ entry in mitochondria via the Ca2+ uniporter followed by Ca2+ activation of three dehydrogenases in the mitochondrial matrix. This results in increases in mitochondrial NADH/NAD ratios and ATP levels and increased substrate uptake by mitochondria. We review evidence gathered more than 20 years ago and recent work indicating that substrate uptake, mitochondrial NADH/NAD ratios, and ATP levels may be also activated in response to cytosolic Ca2+ signals via a mechanism that does not require the entry of Ca2+ in mitochondria, a mechanism depending on the activity of Ca2+-dependent mitochondrial carriers (CaMC). CaMCs fall into two groups, the aspartate-glutamate carriers (AGC) and the ATP-Mg/Pi carriers, also named SCaMC (for short CaMC). The two mammalian AGCs, aralar and citrin, are members of the malate-aspartate NADH shuttle, and citrin, the liver AGC, is also a member of the urea cycle. Both types of CaMCs are activated by Ca2+ in the intermembrane space and function together with the Ca2+ uniporter in decoding the Ca2+ signal into a mitochondrial response.


www.uniprot.org/uniprot/Q12482
Calcium-dependent mitochondrial aspartate and glutamate carrier. Transport of glutamate in mitochondria is required for mitochondrial transamination reactions and ornithine synthesis. Plays also a role in malate-aspartate NADH shuttle, which is critical for growth on acetate and fatty acids.

The aspartate/glutamate carrier isoform 1 is an essential mitochondrial transporter that exchanges intramitochondrial aspartate and cytosolic glutamate across the inner mitochondrial membrane. It is expressed in brain, heart and muscle and is involved in important biological processes, including myelination. However, the signals that regulate the expression of this transporter are still largely unknown. In this study we first identify a CREB binding site within the aspartate/glutamate carrier gene promoter that acts as a strong enhancer element in neuronal SH-SY5Y cells. This element is regulated by active, phosphorylated CREB protein and by signal pathways that modify the activity of CREB itself and, most noticeably, by intracellular Ca2+ levels. Specifically, aspartate/glutamate carrier gene expression is induced via CREB by forskolin while it is inhibited by the PKA inhibitor, H89. Furthermore, the CREB-induced activation of gene expression is increased by thapsigargin, which enhances cytosolic Ca2+, while it is inhibited by BAPTA-AM that reduces cytosolic Ca2+ or by STO-609, which inhibits CaMK-IV phosphorylation. We further show that CREB-dependent regulation of aspartate/glutamate carrier gene expression occurs in neuronal cells in response to pathological (inflammation) and physiological (differentiation) conditions. Since this carrier is necessary for neuronal functions and is involved in myelinogenesis, our results highlight that targeting of CREB activity and Ca2+ might be therapeutically exploited to increase aspartate/glutamate carrier gene expression in neurodegenerative diseases.

Studies in animal models have highlighted the relevance of AGC1 in the physiology of neurons. AGC1 knockout mice showed a dramatic drop in brain aspartate levels, with a concomitant reduction in N-acetylaspartate (NAA) synthesis and hypomyelination (Jalil et al., 2005). The connection between lack of AGC1 and drop in NAA synthesis may due to the lack of mitochondrial aspartate output, which in turn would limit availability of NAA-derived acetate needed for lipid biosynthesis resulting in hypomyelination. Numerous studies have indeed demonstrated that acetate moieties of NAA are incorporated into brain lipids during the development of the central nervous system, hence strongly suggesting that AGC1 may be crucially involved in the myelination). In support of this conclusion, children harboring mutations of the SLC25A12 gene display severe developmental delay, epilepsy, hypotonia hallmarked by hypomyelination and decreased NAA in the brain (Wibom et al., 2009; Falk et al., 2014). The chromosomal region containing the gene encoding AGC1 has also been identified as a putative autism susceptibility locus (Ramoz et al., 2004; Turunen et al., 2008; Palmieri et al., 2010). In addition, interest in the involvement of mitochondria in neurodegenerative and neuroinflammamtory disorders, such as Parkinson's and Alzheimer's disease, and multiple sclerosis is emerging (Lin and Beal, 2006)

Despite the well-established role of NAA in myelin biosynthesis, it is still unknown in which subcellular compartment the biosynthesis occurs. Different studies have provided evidence that the aspartate-N-acetyltransferase (Asp-NAT), the enzyme that catalyzes the biosynthesis of NAA, is localized in the mitochondria (Patel and Clark, 1979; Madhavarao et al., 2003; Arun et al., 2009). However, other studies performed in primary neuronal cultures established that Asp-NAT is located in the endoplasmic reticulum as well (Wiame et al., 2009; Tahay et al., 2012). A colocalization was reported by other authors (Lu et al., 2004; Ariyannur et al., 2010).

3.1. AGC1 expression is downregulated by inflammatory cytokines

3.3. The decrease in AGC1 expression in neuroinflammation is most likely caused by the downregulation of CREB

3.4. Cytosolic Ca2+ level affects AGC1 gene expression via CREB
Because Ca2+ is a well-known CREB inducer (Sheng and Greenberg, 1990) and is also known to stimulate AGC1 activity (Palmieri et al., 2001; Lasorsa et al., 2003; Contreras et al., 2007), we investigated whether alterations in the pool of intracellular Ca2 affect AGC1 gene expression. 

Glutamate is the only amino acid extracted by healthy myocardium in net amounts, with uptake further increased during hypoxic or ischemic conditions. Glutamate supplementation provides cardioprotection from hypoxic and reperfusion injury through several metabolic pathways that depend upon adequate transport of glutamate into the mitochondria. Glutamate transport across the inner mitochondrial membrane is a key component of the malate/aspartate shuttle. Glutamate transport in the brain has been well characterized since the discovery of the excitatory amino acid transporter (EAAT) family. 


Increased expression of the glutamate transporters EAAT1 and EAAT2 in the cerebellum of post-mortem tissue from autism patients has also been reported. Because EAAT expression is controlled in part by the extracellular concentration of glutamate, it is possible that the EAAT overexpression is due to the increased glutamate concentration seen in plasma and spectroscopic studies, as reviewed above.







Fig. 2 The malate – aspartate shuttle (MAS) and A TP generation. MAS is the main pathway for the transfer of reducing equivalents in the form of NADH from the cytosol into the mitochondria. Cytoplasmic malate dehydrogenase reduces oxaloacetate to malate while oxidizing 


A reminder of what belongs where in a cell:-




Components of a typical animal cell:

1.      Nucleolus

2.      Nucleus

3.      Ribosome (little dots)

4.      Vesicle


6.      Golgi apparatus (or "Golgi body")

7.      Cytoskeleton

  1. Smooth endoplasmic reticulum 

9.      Mitochondrion

10.  Vacuole

11.  Cytosol (fluid that contains organelles, comprising the cytoplasm)

12.  Lysosome

13.  Centrosome




Conclusion

I hope some people made it to the end of this post. Since it was written on two computers, there may be some duplication.

It appears that most people with autism would benefit from less calcium in their brains, but this is more complex than it sounds. We need to block voltage gated calcium channels that are open, when they should be closed. We need to reduce IP3 to keep calcium locked up in the endoplasmic reticulum.

If we cannot reduce the level of Ca2+, we need to look at CREB which is mediating much of the damage. We can modify CREB via drugs that increase or decrease PKA. The only problem here is that for most people that would mean decreasing PKA, but PKA also does some other good things. At least in Alzheimer’s things do not conflict you want more CREB and more PKA.

The amino acid transporters AGC1, EAAT1 and EAAT2 are likely over activated in much autism. So we should expect lots of problems with glutamate, aspartate and indeed mitochondrial function. 

It looks like most young people with autism would benefit from more NAA. One study showed that the omega 3 oil EPA can increase NAA.  At least that is simple.

More NAA may well help correct impaired myelination.

Ideas that may potentially help in some cases of autism:-

·        L-aspartic acid / L-aspartate

·        High EPA fish oil to increase NAA

·        PDE4 inhibitors (Ibudilast or Daxas)

·        PKA inhibitors (not easy)

·        IP3R blocker (only caffeine seems currently viable and is suboptimal)

         Interactions of antagonists with subtypes of inositol 1,4,5-trisphosphate   (IP3) receptor

·        Verapamil in those with over-active (open) L-type calcium channels 



Does oral L-aspartic acid actually reach the brain? Just try some. It tastes odd, like a homemade sweet/sour flavoring gone wrong and does not dissolve in water.  It should be harmless in moderation.