Ketones and Autism Part 1 - Ketones, Epilepsy, GABA and Gut Bacteria

Source: The Gut Microbiota Mediates the Anti-Seizure Effects of the Ketogenic Diet

Today’s post is the first in a short series about ketones, that looks into very specific areas of the science.

There was an earlier post on the Ketogenic Diet (KD).

The Clever Ketogenic Diet for some Autism

We already know, anecdotally, that some people with autism respond well to the Ketogenic Diet (KD) and some to just ketone supplements. We also know from some very small clinical trials that a minority of those with autism benefit from the KD. 

What percentage of people with autism respond to ketones?

This is the important question and the simple answer appears to be a minority, albeit a significant minority. A lot depends on what you mean by autism and what you judge to be a response. From reading up on the subject I would estimate that about 20% respond well, but which 20%?

Why do some people with autism respond to ketones and how do you maximize the effect?

There is quite a lot of useful information in the literature, but it is clear that most people do not respond to ketones, so you really need to know if your case is one of the minority that do respond, before getting too carried away with changing diet. From research on people wanting to lose weight there are plenty of practical tips to maximize ketones, even drinking coffee produces more ketones; increasing the hours you fast each day also helps. 

If you have a healthy, sporty, child with autism you might want more ketones but you do not want to lose weight.

Do you have a responder? 

There does not yet appear to be a way to predict who will respond well to ketones, other than those people who have seizures. 

You can read all about ketones or just try them out. To try them out, a good place to start is with the exogenous ketone supplements mainly sold to people trying to lose weight. It looks like 10ml of C8 oil and 10ml of BHB ester is a good place to start and soon you may produce enough ketones to establish if someone is a responder, then you just have to figure out why they are a responder and then to maximize this effect, which might involve things other than ketone supplements.  

You can measure ketones in urine and so you can see whether you have reached the level found in trials that produces a positive effect in some people. If you can establish that you have indeed produced this level of ketones and you see no effect, then it is time to cross ketones and the ketogenic diet off your to-do list.  

If you are fortunate to find a responder, then you can move forward with trying to maximize the benefit. 

Ketone supplements

Ketone supplements can be extremely expensive when you use the recommended dosage and may contain quite large amounts of things that you might not want (sodium, potassium and calcium for example).  Always read the labels.

It is clear that some of these products are much more effective at producing ketones than others. For a change, you can measure their effectiveness and avoid wasting your money. Ketone testing strips are inexpensive. 

Ketone Posts 

·        Part1 - Ketones, epilepsy, GABA and gut bacteria

·        Ketones as a fuel, Alzheimer’s and GLUT1 deficiency

·        Ketones and microglia

·        Ketones as HDAC inhibitors and epigenetic modifiers

·        Ketones, exercise and BDNF

·        Maximizing ketones through diet, fasting, exercise, coffee and supplementation

Ketones, epilepsy, GABA and gut bacteria

Today’s post just looks at the effect of ketones on the neurotransmitter GABA, which should be inhibitory, but in much autism is actually excitatory. The GABA switch failed to flip just after birth and neurons remain in an immature state, due to too many NKCC1 chloride transporters and too few KCC2 chloride transporters. With too much chloride inside neurons GABA has an excitatory effect on neurons causing them to fire when they should not.

In epilepsy, too much excitation from Glutamate and too little inhibition from GABA may lead to seizures. So, in some types of epilepsy you want to increase GABA and reduce Glutamate, i.e. you want to increase the GABA/Glutamate ratio.

In autism it is not clear that increasing the GABA/Glutamate ratio is going to help, it all depends on the kind of autism. Much of this blog is about changing the effect of GABA (flipping the GABA switch) and not changing the amount of it.

In some people with autism and epilepsy ketones resolve the seizures but do not improve the autism.

In other people with autism and no seizures, ketones improve their autism. This may, or may not, be due to the effect ketones have on GABA.  

Two issues are looked into in this post: -

·        Do ketones affect NKCC1/KCC2 expression and hence the effect of GABA in the brain?

·        Do ketones affect the amount of GABA and Glutamate in key parts of the brain?

The good news is that research into epilepsy shows that ketones do indeed have an effect on GABA, but it is highly disputed whether they modify NKCC1/KCC2 expression and the GABA switch from immature to mature neurons. 

The KD and Epilepsy

The KD has been used to treat epilepsy for almost a century, but until very recently nobody really knew why it worked.

A recent very thoughtful study at UCLA has shown that the KD mediates its anti-seizure effects via changes to the bacteria in the gut. The researchers identified the two bacteria and then showed that, at least in mice, the same anti-seizure effect provided by the KD could be provided just by adding these two bacteria (i.e. no need to follow the ketogenic diet).

Gut bacteria play critical role in anti-seizure effects of ketogenic diet, UCLA scientists report

UCLA scientists have identified specific gut bacteria that play an essential role in the anti-seizure effects of the high-fat, low-carbohydrate ketogenic diet. The study, published today in the journal Cell, is the first to establish a causal link between seizure susceptibility and the gut microbiota — the 100 trillion or so bacteria and other microbes that reside in the human body’s intestines.

The ketogenic diet has numerous health benefits, including fewer seizures for children with epilepsy who do not respond to anti-epileptic medications, said Elaine Hsiao, UCLA assistant professor of integrative biology and physiology in the UCLA College, and senior author of the study. However, there has been no clear explanation for exactly how the diet aids children with epilepsy.

Researchers in Hsiao’s laboratory hypothesized that the gut microbiota is altered through the ketogenic diet and is important for the diet’s anti-seizure effects. Hsiao’s research team conducted a comprehensive investigation into whether the microbiota influences the ability of the diet to protect against seizures and if so, how the microbiota achieves these effects.

In a study of mice as a model to more thoroughly understand epilepsy, the researchers found that the diet substantially altered the gut microbiota in fewer than four days, and mice on the diet had significantly fewer seizures.

To test whether the microbiota is important for protection against seizures, the researchers analyzed the effects of the ketogenic diet on two types of mice: those reared as germ-free in a sterile laboratory environment and mice treated with antibiotics to deplete gut microbes.

“In both cases, we found the ketogenic diet was no longer effective in protecting against seizures,” said lead author Christine Olson, a UCLA graduate student in Hsiao’s laboratory. “This suggests that the gut microbiota is required for the diet to effectively reduce seizures.”

The biologists identified the precise order of organic molecules known as nucleotides from the DNA of gut microbiota to determine which bacteria were present and at what levels after the diet was administered. They identified two types of bacteria that were elevated by the diet and play a key role in providing this protection: Akkermansia muciniphila and Parabacteroides species.

With this new knowledge, they studied germ-free mice that were given these bacteria.

“We found we could restore seizure protection if we gave these particular types of bacteria together,” Olson said. “If we gave either species alone, the bacteria did not protect against seizures; this suggests that these different bacteria perform a unique function when they are together.”

The researchers measured levels of hundreds of biochemicals in the gut, blood and hippocampus, a region of the brain that plays an important role in spreading seizures in the brain. They found that the bacteria that were elevated by the ketogenic diet alter levels of biochemicals in the gut and the blood in ways that affect neurotransmitters in the hippocampus.

How do the bacteria do this? “The bacteria increased brain levels of GABA — a neurotransmitter that silences neurons — relative to brain levels of glutamate, a neurotransmitter that activates neurons to fire,” said co-author Helen Vuong, a postdoctoral scholar in Hsiao’s laboratory.

“This study inspires us to study whether similar roles for gut microbes are seen in people that are on the ketogenic diet,” Vuong said.

“The implications for health and disease are promising, but much more research needs to be done to test whether discoveries in mice also apply to humans,” said Hsiao, who is also an assistant professor of medicine in the David Geffen School of Medicine at UCLA.

On behalf of the Regents of the University of California, the UCLA Technology Development Group has filed a patent on Hsiao’s technology that mimics the ketogenic diet to provide seizure protection. It has exclusively licensed it to a start-up company Hsiao has helped to launch that will examine the potential clinical applications of her laboratory’s findings.

Here is Hsiao’s new start-up:

Bloom Science launches to treat epilepsy with ketogenic diet-associated gut microbes

“We are hacking the ketogenic diet to identify microbes that have therapeutic potential for the treatment of epilepsy,” says Bloom CEO Tony Colasin.

The San Diego-based start-up isn’t announcing how much seed funding it raised, but Colasin plans to move fast and get a product on the market in a mere two to three years. That’s because Bloom will first develop a medical food based on the two kinds of bacteria identified in Hsiao’s study. Bloom also has plans to optimize the bacterial strains for specific kinds of epilepsy to develop a traditional approved drug.

The way the bacteria help control seizures actually appears to be similar to the mechanism of many commercial ant epilepsy drugs. The microbes’ metabolism increases the ratio of inhibitory to excitatory neurotransmitters in the brain—specifically, higher levels of gamma-aminobutyric acid (GABA) relative to levels of glutamate.

Bloom is also considering how the microbiome benefits of the ketogenic diet could be helpful in other neurological conditions, including autism, depression, and Parkinson’s disease. “It is early days, but we are excited about the potential,” Colasin says.

Here is the full paper: -

The Gut Microbiota Mediates the Anti-Seizure Effects of the Ketogenic Diet

The ketogenic diet (KD) is used to treat refractory epilepsy, but the mechanisms underlying its neuroprotective effects remain unclear. Here, we show that the gut microbiota is altered by the KD and required for protection against acute electrically induced seizures and spontaneous tonic-clonic seizures in two mouse models. Mice treated with antibiotics or reared germ free are resistant to KD-mediated seizure protection. Enrichment of, and gnotobiotic co-colonization with, KD-associated Akkermansia and Parabacteroides restores seizure protection. Moreover, transplantation of the KD gut microbiota and treatment with Akkermansia and Parabacteroides each confer seizure protection to mice fed a control diet. Alterations in colonic lumenal, serum, and hippocampal metabolomic profiles correlate with seizure protection, including reductions in systemic gamma-glutamylated amino acids and elevated hippocampal GABA/glutamate levels. Bacterial cross-feeding decreases gamma-glutamyltranspeptidase activity, and inhibiting gamma-glutamylation promotes seizure protection in vivo. Overall, this study reveals that the gut microbiota modulates host metabolism and seizure susceptibility in mice.

Achieving the Gut Bacteria changes of the KD without the diet

Since the ketogenic diet (KD) is very restrictive, it would be much more convenient to achieve the GABA/Glutamate effect in a simpler way. You cannot currently just buy these two bacteria as a supplement.  There would seem to be 2 other obvious options: -

·        Take exogenous ketone supplements and hope this causes the same gut bacterial changes produced by the KD. No evidence exists.

·        Use other known methods to increase to increase Akkermansia muciniphila and Parabacteroides species in a similar way to that likely being developed by Bloom Sciences in San Diego. Bloom are developing a medical food to achieve this, so it will require a prescription and it will be costly. 

Increasing Akkermansia muciniphila can be achieved using fructooligosaccharides (FOS). FOS is included in many types of formula milk for babies and is sold as a supplement.

Metformin, a drug used to treat type 2 diabetes, greatly increases Akkermansia muciniphila. Vancomycin, the antibiotic that stays in the gut, also greatly increases Akkermansia muciniphila, but it is also going to wipe out many bacteria.

The research shows you also need the second bacteria Parabacteroides, of which there are many types. These bacteria are found in high levels in people following a Mediterranean type diet but it can be increased using Resistant Starch Type 4. This type of starch has been chemically modified to resist digestion. This starch is sold as food ingredient to add to bakery products.

http://www.ingredion.us/ingredients/na/versafibe-2470-dietary-fiber-22457b00.html

http://resistantstarchfoundation.com/resistant-starch-type-4/

Strategies to promote abundance of Akkermansia muciniphila, an emerging probiotics in the gut, evidence from dietary intervention studies

Viable A. muciniphila and fructooligosaccharides contently promote A. muciniphila. 

Metformin and vancomycin also significantly promote A. muciniphila.

https://biofoundations.org/increasing-and-maintaining-akkermansia-muciniphila-for-a-healthy-gut-microbiome/

“Akkermansia can also be increased by consuming polyphenol-rich foods, including:

·         pomegranate (attributed to ellagitannins and their metabolites)

·      grape polyphenols (grape seed extract) (proanthocyanidin-rich extracts may increase mucus secretion, therefore creating a favorable environment for Akkermansia to thrive) 

·   cranberries “ 

Two Healthy Diets Modulate Gut Microbial Community Improving Insulin Sensitivity in a Human Obese Population

The abundance of Parabacteroides distasonis (P = .025) and Faecalibacterium prausnitzii (P = .020) increased after long-term consumption of the Med diet and the LFHCC diet, respectively.

Beneficial modulation of the gut microbiota

Resistant starches types 2 and 4 have differential effects on the composition of the fecal microbiota in human subjects.

Abstract

BACKGROUND:

To systematically develop dietary strategies based on resistant starch (RS) that modulate the human gut microbiome, detailed in vivo studies that evaluate the effects of different forms of RS on the community structure and population dynamics of the gut microbiota are necessary. The aim of the present study was to gain a community wide perspective of the effects of RS types 2 (RS2) and 4 (RS4) on the fecal microbiota in human individuals.

METHODS AND FINDINGS:

Ten human subjects consumed crackers for three weeks each containing either RS2, RS4, or native starch in a double-blind, crossover design. Multiplex sequencing of 16S rRNA tags revealed that both types of RS induced several significant compositional alterations in the fecal microbial populations, with differential effects on community structure. RS4 but not RS2 induced phylum-level changes, significantly increasing Actinobacteria and Bacteroidetes while decreasing Firmicutes. At the species level, the changes evoked by RS4 were increases in Bifidobacterium adolescentis and Parabacteroides distasonis, while RS2 significantly raised the proportions of Ruminococcus bromii and Eubacterium rectale when compared to RS4. The population shifts caused by RS4 were numerically substantial for several taxa, leading for example, to a ten-fold increase in bifidobacteria in three of the subjects, enriching them to 18-30% of the fecal microbial community. The responses to RS and their magnitudes varied between individuals, and they were reversible and tightly associated with the consumption of RS.

CONCLUSION:

Our results demonstrate that RS2 and RS4 show functional differences in their effect on human fecal microbiota composition, indicating that the chemical structure of RS determines its accessibility by groups of colonic bacteria. The findings imply that specific bacterial populations could be selectively targeted by well-designed functional carbohydrates, but the inter-subject variations in the response to RS indicates that such strategies might benefit from more personalized approaches.

Ketones and NKCC1/KCC2  

The next part of this post does get complicated and so it will be of interest to a smaller number of readers; the question is whether ketones play a role in the (miss) expression of those two critical chloride transporters NKCC1 and KCC2. If ketones play a role, then they might have therapeutic potential in all those people with autism and Down Syndrome who respond to bumetanide.

Some researchers think ketones play such a role but the bumetanide for autism researchers disagree.

The ongoing disagreement in the research is about the role played by a lack of ketones in why in immature neurons GABA is excitatory. Regular readers will know that in a large group of autism the GABA switch never flips and so neurons remain in the immature state that was only supposed to last weeks after birth. The debate in the research is to what extent ketone bodies play a role.

We know that in much autism and indeed in those with other problems like neuropathic pain, there can be elevated chloride due to over-expression of NKCC1 (through which chloride enters) and under-expression of KCC2 (through which chloride ions exit neurons). 

GABA action in immature neocortical neurons directly depends on the availability of ketone bodies. 

Abstract

In the early postnatal period, energy metabolism in the suckling rodent brain relies to a large extent on metabolic pathways alternate to glucose such as the utilization of ketone bodies (KBs). However, how KBs affect neuronal excitability is not known. Using recordings of single NMDA and GABA-activated channels in neocortical pyramidal cells we studied the effects of KBs on the resting membrane potential (E(m)) and reversal potential of GABA-induced anionic currents (E(GABA)), respectively. We show that during postnatal development (P3-P19) if neocortical brain slices are adequately supplied with KBs, E(m) and E(GABA) are both maintained at negative levels of about -83 and -80 mV, respectively. Conversely, a KB deficiency causes a significant depolarization of both E(m) (>5 mV) and E(GABA) (>15 mV). The KB-mediated shift in E(GABA) is largely determined by the interaction of the NKCC1 cotransporter and Cl(-)/HCO3 transporter(s). Therefore, by inducing a hyperpolarizing shift in E(m) and modulating GABA signaling mode, KBs can efficiently control the excitability of neonatal cortical neurons.

In the early postnatal period, energy metabolism in the suckling rodent brain relies to a large extent on metabolic pathways alternate to glucose such as the utilization of ketone bodies (KBs). However, how KBs affect neuronal excitability is not known. Using recordings of single NMDA and GABA activated channels in neocortical pyramidal cells we studied the effects of KBs on the resting membrane potential (Em) and reversal potential of GABA-induced anionic currents (EGABA), respectively. We show that during postnatal development (P3–P19) if neocortical brain slices are adequately supplied with KBs, Em and EGABA are both maintained at negative

levels of about )83 and )80 mV, respectively. Conversely, a KB deficiency causes a significant depolarization of both Em (>5 mV) and EGABA (>15 mV). The KB-mediated shift in EGABA is largely determined by the interaction of the NKCC1 cotransporter and Cl)/HCO3 transporter(s). Therefore, by inducing a hyperpolarizing shift in Em and modulating GABA signaling mode, KBs can efficiently control the excitability of neonatal cortical neurons. Keywords: cortex, development, energy substrates, GABA, ketone bodies, resting potential.

showed that in the presence of KBs, values of EGABA in neocortical pyramidal neurons were close to Em, and did not change significantly during postnatal development, being maintained at about )80 mV (see Fig. 3). We cannot exclude the possibility that these values may differ in dendritic (Gulledge and Stuart 2003) or axonal (Price and Trussell 2006; Trigo et al. 2007; Khirug et al. 2008) compartments, an issue for future studies. Additionally, in this study we have limited our investigations to pyramidal cells, and the effects of KBs on interneurons remain to be explored. Nevertheless, the present observations suggest that energy substrates in the developing brain are an important issue to consider when studying neonatal neuronal excitability. Indeed, the most straightforward explanation for the difference between the results of the current study and those of previous studies of the development of neonatal GABA signaling lies in the fact that the brain of the suckling rodent relies strongly on KBs (Cremer and Heath 1974; Dombrowski et al. 1989; Hawkins et al. 1971; Lockwood and Bailey 1971; Lust et al. 2003; Page et al. 1971; Pereira de Vasconcelos and Nehlig 1987; Schroeder et al. 1991; Yeh and Zee 1976). Glucose utilization is limited at this age (Dombrowski et al. 1989; Nehlig, 1997; Nehlig et al. 1988; Prins 2008) because of the delayed maturation of the glycolytic enzymatic system (Dombrowski et al. 1989; Land et al. 1977; Leong and Clark 1984; Prins 2008). Use of glucose as the sole energy substrate caused an increase in neonatal neuronal [Cl)]i in our experiments, similar to that observed previously, while the addition of KBs resulted in a hyperpolarizing shift in both Em and EGABA. These results highlighted the need for caution in the interpretation of results obtained from neonatal brain slices superfused with standard ACSF. The cation chloride cotransporters NKCC1 and KCC2have been suggested to be the main regulators of neuronal Cl) homeostasis both during development (Farrant and Kaila 2007; Fiumelli and Woodin 2007) and in pathology (Galanopoulou, 2007; Kahle and Staley, 2008; Kahle et al. 2008).Although the possible contribution of anion exchangers to neuronal Cl) homeostasis has been noted previously (Farrant and Kaila 2007; Hentschke et al. 2006; Hubneret al. 2004; Pfeffer et al. 2009), they have not attracted the same degree of attention. Results from our study demonstrate, however, that the Cl)/HCO)3 transporter system is strongly involved in the KB-mediated regulation of [Cl)]i during postnatal development. Within this family, the Na-dependent Cl)/HCO)3 transporter (NDCBE), is of particular interest as it is expressed in the cortex (Chen et al. 2008) and has a strong dependence on ATP for its action (Chen et al. 2008; Davis et al. 2008; Romero et al. 2004). In addition, the sodium driven chloride bicarbonate exchanger(NCBE),(Giffardet al. 2003; Hubner et al. 2004; Lee et al. 2006) was expressed in the brain early during prenatal development and its expression preceded that of KCC2 (Hubner et al. 2004).

In neonatal neocortical neurons the interaction of NKCC1 and the Cl)/HCO3) transporter(s) maintained [Cl)]i, with KCC2 playing a less significant role at this stage. In the absence of KBs, when Cl)/HCO3) transporter(s) were less effective, the role of NKCC1 as a Cl) loader was especially noticeable and resulted in a depolarizing EGABA. During development the contribution of KCC2 to neocortical neuronal Cl) homeostasis is likely to increase (Stein et al. 2004; Zhang et al. 2006), and the balance between the actions of the different Cl) transporters in adults should be studied in the future. In humans, blood levels of KBs increase considerably during fasting, strenuous exercise, stress, or on the high-fat, low-carbohydrate ketogenic diet (KD) (Newburgh and Marsh 1920). A rapidly growing body of evidence indicates that the KD can have numerous neuroprotective effects (Gasior et al. 2006). During treatment with the KD, levels of KBs increase in both blood and brain, and cerebral metabolism adapts to preferentially use KBs as an alternate energy substrate to glucose (Kim do and Rho 2008). In children, the KD has been used as an effective treatment for medically refractory epilepsy (Freeman et al. 2007; Hartman and Vining 2007). However, despite nearly a century of use, the mechanisms underlying its clinical efficacy have proved elusive (Morris 2005; Bough and Rho 2007; Kim do and Rho 2008). Suckling rodents provide a natural model of the KD because of the high ketogenic ratio (Wilder and Winter 1922) of rodent milk (Page et al. 1971; Nehlig 1999). We propose that the KB-induced modulation of GABA-signaling may constitute a mechanism of anticonvulsive actions of the KD.

Now for the opposing views: -

Excitatory action of GABA on immature neurons is not due to absence of ketone bodies metabolites or other energy substrates

Summary

Brain slices incubated with glucose have provided most of our knowledge on cellular, synaptic, and network driven mechanisms. It has been recently suggested that γ‐aminobutyric acid (GABA) excites neonatal neurons in conventional glucose‐perfused slices but not when ketone bodies metabolites, pyruvate, and/or lactate are added, suggesting that the excitatory actions of GABA are due to energy deprivation when glucose is the sole energy source. In this article, we review the vast number of studies that show that slices are not energy deprived in glucose‐containing medium, and that addition of other energy substrates at physiologic concentrations does not alter the excitatory actions of GABA on neonatal neurons. In contrast, lactate, like other weak acids, can produce an intracellular acidification that will cause a reduction of intracellular chloride and a shift of GABA actions. The effects of high concentrations of lactate, and particularly of pyruvate (4–5 mm), as used are relevant primarily to pathologic conditions; these concentrations not being found in the brain in normal “control” conditions. Slices in glucose‐containing medium may not be ideal, but additional energy substrates neither correspond to physiologic conditions nor alter GABA actions. In keeping with extensive observations in a wide range of animal species and brain structures, GABA depolarizes immature neurons and the reduction of the intracellular concentration of chloride ([Cl⁻]_i) is a basic property of brain maturation that has been preserved throughout evolution. In addition, this developmental sequence has important clinical implications, notably concerning the higher incidence of seizures early in life and their long‐lasting deleterious sequels. Immature neurons have difficulties exporting chloride that accumulates during seizures, leading to permanent increase of [Cl⁻]_i that converts the inhibitory actions of GABA to excitatory and hampers the efficacy of GABA‐acting antiepileptic drugs.  

Depolarizing Actions of GABA in Immature Neurons Depend Neither on Ketone Bodies Nor on Pyruvate

GABA depolarizes immature neurons because of a high [Cl⁻]_i and orchestrates giant depolarizing potential (GDP) generation. Zilberter and coworkers (Rheims et al., 2009; Holmgren et al., 2010) showed recently that the ketone body metabolite dl-3-hydroxybutyrate (dl-BHB) (4 mm), lactate (4 mm), or pyruvate (5 mm) shifted GABA actions to hyperpolarizing, suggesting that the depolarizing effects of GABA are attributable to inadequate energy supply when glucose is the sole energy source. We now report that, in rat pups (postnatal days 4–7), plasma d-BHB, lactate, and pyruvate levels are 0.9, 1.5, and 0.12 mm, respectively. Then, we show that dl-BHB (4 mm) and pyruvate (200 μm) do not affect (i) the driving force for GABA_A receptor-mediated currents (DF_GABA) in cell-attached single-channel recordings, (2) the resting membrane potential and reversal potential of synaptic GABA_A receptor-mediated responses in perforated patch recordings, (3) the action potentials triggered by focal GABA applications, or (4) the GDPs determined with electrophysiological recordings and dynamic two-photon calcium imaging. Only very high non physiological concentrations of pyruvate (5 mm) reduced DF_GABA and blocked GDPs. Therefore, dl-BHB does not alter GABA signals even at the high concentrations used by Zilberter and colleagues, whereas pyruvate requires exceedingly high non-physiological concentrations to exert an effect. There is no need to alter conventional glucose enriched artificial CSF to investigate GABA signals in the developing brain.

Very recent research shows that ketones do not affect the expression of NKCC1 or KCC2. This would tend to support the argument of Ben Ari and Tyzio.

Ketogenic diet does not change NKCC1 and KCC2 expression in rat hippocampus

  

Nonetheless it seems that ketone bodies do indeed have an effect on GABA; they appear to change the hippocampal GABA/Glutamate ratio. 

So Tyzio might not be as right as he thought in his rebuttal paper when he said.

“suggesting, contrary to Zilberter and colleagues, that the antiepileptic actions of ketone bodies are not mediated by GABA signalling”

Tyzio is thinking about the resting membrane potential (Em) and reversal potential of GABA-induced anionic currents (EGABA).

At the end of that day a reduction in gamma-glutamylated amino acids, caused by changes in gut microbiota cause an increase in hippocampal GABA/Glutamate ratio. If you happen to have epilepsy this may mean less seizures.  

Conclusion

I think we can say with a fair degree of certainty that we now know why the ketogenic diet, and indeed the modified Atkins diet, greatly reduce seizures in many people with epilepsy. The diet changes the gut microbiota by increasing the amount of Akkermansia muciniphila and Parabacteroides species, the end result is an increase in GABA, the inhibitory neurotransmitter, inside the brain. In much epilepsy, more inhibition to neurons firing results is far less seizures.

GABA plays a key role in autism, albeit a complex one.

The ketone driven changes to GABA might explain why some people with autism respond to the KD or just ketone supplements, but ketones have many other effects relevant to autism that will be reviewed in later posts.

Connecting Estradiol with WNK, SPAK and OSR1; plus Taurine

Japan, home to today’s complicated research

Today’s post hopes to give a more complete picture of the various processes involved in shifting the immature neurons often found in autism towards the mature neurons, found in most people.  This stalled process is complex and may only apply to around half of all autism.

The post assumes prior knowledge from previous posts about the GABA switch and the KCC2 and NKCC1 chloride cotransporters.

The best graphic I found is below and includes almost everything. The paper itself is very thorough and I recommend the scientists among you read the paper rather than my post.

What we want to understand is why neurons did not switch from immature to mature, in the process I am calling the “GABA switch”.  We know a great deal about what happens before and after the switch and many processes that can be  involved, but the exact switch itself remains undefined.

In a previous post I highlighted that neuroligin 2 (NL2)/RORa may be the GABA switch, but there is no mention of neuroligins in the research reviewed today. 

Neuroligins, Estradiol and Male Autism

So when you read today’s mainly Japanese research, you should note that one key part is missing, the actual trigger mechanism.

The ideal way to make neurons transition from immature to mature is the way nature intended. That requires an understanding of the GABA switch mechanism.

Source and excellent paper:-

Development and regulation of chloride homeostasis in the central nervous system

 The important things you might not notice:

E is the female hormone estrogen/estradiol

T is testosterone. Testosterone can be converted to estradiol by aromatase.

DHT is another male hormone Dihydrotestosterone. DHT is synthesized from testosterone by the enzyme 5α-reductase. In males, approximately 5% of testosterone undergoes 5α-reduction into DHT. DHT cannot be converted into estrogen.

Relative to testosterone, DHT is considerably more potent as an agonist of the androgen receptor (AR). This may turn out to be very important.

T3 is the active thyroid hormone, triiodothyronine

In earlier posts we saw that in autism there can be a lack of aromatase and that there is reduced expression of estrogen receptor beta.

In the diagram below this leads to reduced estrogen and increased testosterone. If there is elevated DHT this will make the situation worse.  All this down-regulates ROR-alpha.

ROR-alpha affects numerous things and is another nexus which links biological processes that have gone awry in autism. By upregulating ROR-alpha multiple good effects may follow, these include increasing KCC2 and reducing NKCC1.

It is certainly possible that the GABA switch is mediated by RORa-estradiol-Neuoligin-2.  In which case the solution is to upregulate RORa which can be done in many ways (androgen receptor, estrogen receptors etc.)

The schematic illustrates a mechanism through which the observed reduction in RORA in autistic brain may lead to increased testosterone levels through downregulation of aromatase. Through AR, testosterone negatively modulates RORA, whereas estrogen upregulates RORA through ER.

androgen receptor = AR

estrogen receptor = ER

Going back to the complex first chart in this post, we want to increase KCC2 in the immature neuron and reduce NKCC1.

So we want lines with flat end going into NKCC1, for example from OXT (the Oxytocin surge during natural birth).

We want arrows going to KCC2, for example we want more PKC (Protein Kinase C) coming from those  mGluRs, that we have come across many times in this blog.

What we do not want is anything coming from WNK- SPAK- OSR1.

Reduced expression of the thyroid hormone T3 does affect the both KCC2 and NKCC1 expression the brain. One of my earlier posts did suggest central hypothyroidism in autism, this fitted in with the findings of the Polish researcher at Harvard, who I had some correspondence with.

Oxidative Stress, Central Hypothyroidism, Autism and You   

Another transcription factor that has been identified as a potent regulator of KCC2 expression is upstream stimulating factor 1 (USF1) as well as USF2. The USF1 gene has been linked to familial combined hyperlipidemia. 

It is thought that increasing the expression of USF1 with increase KCC2, but it will increase other things as well.

We also know that Egr4 may be an important component in the mechanism for trophic factor-mediated upregulation of KCC2 protein in developing neurons.

Early Growth Response 4 (EGR-4) is a transcription factor that activates numerous other processes.

It is known that the growth factor Neurturin upregulates EGR4, but it does not cross the blood brain barrier. It was considered as a possible therapy for Parkinson’s Disease. In the first chart in this post, NRTN is Neurturin.

Neurturin Evokes MAPK-Dependent Upregulation of Egr4 and KCC2 in Developing Neurons

It turns out that EGR4 is redox sensitive. In other words certain types of oxidative stress should upregulate EGR4.

Recent studies have demonstrated that zinc controls KCC2 activity via a postsynaptic metabotropic zinc receptor/G protein-linked receptor 39 mZnR/GPR39. The levels of both synaptic Zn²⁺ and KCC2 are developmentally upregulated. During the postnatal period, synaptic Zn²⁺ accumulation and KCC2 expression reach levels similar to those in adult brain.  The zinc transporter 1 (ZnT-1), which is present in areas rich in synaptic zinc, is expressed from the first postnatal week in cortex, hippocampus, olfactory bulb. In the cerebellum, the expression of ZnT-1 in purkinje cells is increased during the second postnatal week.

We have seen that in autism there are anomalies with zinc; in effect it is in the wrong place. Perhaps there is a problem with the zinc transporter in some autism. Decreased ZnT-1 is associated with mild cognitive impairment (MCI).

The male/female hormones play a key role in KCC2/NKCC1, but estradiol/estrogen has a very complex role.

Estradiol can have paradoxical effects.  Its effects can also vary depending on whether you are male or female.

“the effects of estradiol on chloride cotransporters or GABA_A signaling may depend upon the direction of GABA_A responses”

In effect this may mean if GABA is working normally we get one effect on KCC2/NKCC1, but if it is working in reverse (bumetanide responders) we may see the opposite effect.

In the above chart estrogen is shown as increasing KCC2 mRNA in males (a good thing) but inhibiting KCC2 mRNA in females. Messenger RNA (mRNA) is one step in the process of producing the protein (KCC2) from its gene. So the more mRNA the better, if you want more of that protein.

Estrogen also has an effect on OSR1. As shown in this Japanese paper, estrogen is having the opposite effect to what we want; it is inhibiting KCC2 and stimulating NKCC1.

There is research specifically focused on the effect of estrogen on NKCC1 and KCC2. It looks like in some circumstances the effect is good, while in others it will be bad.

From the perspective I have from my posts on RORa, I am expecting a positive effect. I expect in bumetanide responders, estrogen/estradiol will increase KCC2 and reduce NKCC1 and so lower the level of chloride in neurons.

You can also easily argue that estrogen should be bad. What is clear is that inhibiting WNK, SPAK and OSR1 should all be good.  That then brings us to taurine and the start of the WNK-SPAK- OSR1 cascade.

As we have seen in previous posts,  TrkB (tyrosine receptor kinase B) a receptor for various growth factors including  brain-derived neurotrophic factor (BDNF), plays a role. In much autism BDNF is found to be elevated.

ERK is also called MAPK.  The MAPK/ERK pathway is best known in relation to (RAS/RAF-dependent) cancers. This RAS/RAF/ERK1/2 pathway is also known to be upregulated in autism.  In today’s case, ERK is just causing an increase in Early Growth Response 4 (EGR4).

Activating PKC looks a good idea.  It also is the mechanism in some other Japanese research I covered in an old post.  You may recall that in autism sometimes the GABA_A receptors get physically dispersed and need to be brought back tightly together, otherwise they do not work properly.  This process required calcium to be released from the via IP3R to increase PKC.

The Excitatory/Inhibitory Imbalance – GABA_A stabilization via IP3R

Studies have indeed shown that PKC is reduced in some autism, which is what you might have expected. 

Finally, the other estradiol/estrogen papers:- 

Kinases SPAK andOSR1 are up regulated by estradiol and activate NKCC1 in the developing hypothalamus

In immature neurons the amino acid neurotransmitter, γ-aminobutyric acid (GABA) provides the dominant mode for neuronal excitation by inducing membrane depolarization due to Cl⁻ efflux through GABA_A receptors (GABA_ARs). The driving force for Cl⁻ is outward because the Na⁺-K⁺-2Cl⁻ cotransporter (NKCC1) elevates the Cl⁻ concentration in these cells. GABA-induced membrane depolarization and the resulting activation of voltage-gated Ca²⁺ channels is fundamental to normal brain development, yet the mechanisms that regulate depolarizing GABA are not well understood. The neurosteroid estradiol potently augments depolarizing GABA action in the immature hypothalamus by enhancing the activity of the NKCC1 cotransporter. Understanding how estradiol controls NKCC1 activity will be essential for a complete understanding of brain development. We now report that estradiol treatment of newborn rat pups significantly increases protein levels of two kinases upstream of the NKCC1 cotransporter, SPAK and OSR1. The estradiol-induced increase is transcription dependent, and its time course parallels that of estradiol-enhanced phosphorylation of NKCC1. Antisense oligonucleotide-mediated knockdown of SPAK, and to a lesser degree of OSR1, precludes estradiol-mediated enhancement of NKCC1 phosphorylation. Functionally, knockdown of SPAK or OSR1 in embryonic hypothalamic cultures diminishes estradiol-enhanced Ca²⁺ influx induced by GABA_AR activation. Our data suggest that SPAK and OSR1 may be critical factors in the regulation of depolarizing GABA-mediated processes in the developing brain. It will be important to examine these kinases with respect to sex differences and developmental brain anomalies in future studies.

The ability of the brain to synthesize estradiol in discrete loci raises the specter of estrogens as widespread endogenous regulators of depolarizing GABA actions that broadly impact on brain development.

Disregulation in developmental excitatory GABAergic signaling has been shown to impair the development of neuronal circuits and may be a contributing factor in neurodevelopmental disorders such as epilepsy, autism spectrum disorders, and schizophrenia (Briggs and Galanopoulou, 2011; Pizzarelli and Cherubini, 2011; Hyde et al, 2011). Sex differences have been widely reported in all of these disorders, implicating a role for estradiol in their etiology. Targeting SPAK or OSR1 may allow for novel therapeutic options for these neural disorders.

  

Sexually dimorphic expression of KCC2 and GABA function 

GABA_A receptors have an age-adapted function in the brain. During early development, they mediate depolarizing effects, which result in activation of calcium-sensitive signaling processes that are important for the differentiation of the brain. In more mature stages of development and in adults, GABA_A receptors acquire their classical hyperpolarizing signaling. The switch from depolarizing to hyperpolarizing GABA_A-ergic signaling is triggered through the developmental shift in the balance of chloride cotransporters that either increase (ie NKCC1) or decrease (ie KCC2) intracellular chloride. The maturation of GABA_A signaling follows sex-specific patterns, which correlate with the developmental expression profiles of chloride cotransporters. This has first been demonstrated in the substantia nigra, where the switch occurs earlier in females than in males. As a result, there are sensitive periods during development when drugs or conditions that activate GABA_A receptors mediate different transcriptional effects in males and females. Furthermore, neurons with depolarizing or hyperpolarizing GABA_A-ergic signaling respond differently to neurotrophic factors like estrogens. Consequently, during sensitive developmental periods, GABA_A receptors may act as broadcasters of sexually differentiating signals, promoting gender-appropriate brain development. This has particular implications in epilepsy, where both the pathophysiology and treatment of epileptic seizures involve GABA_A receptor activation. It is important therefore to study separately the effects of these factors not only on the course of epilepsy but also design new treatments that may not necessarily disturb the gender-appropriate brain development.

1.3.2 GABA_A receptor signaling as sex-specific modifier of estradiol effects

To further understand the mechanisms underlying the higher expression of KCC2 in the female SNR, we examined the in vivo regulation of KCC2 mRNA by gonadal hormones. As previously stated, the perinatal surge of testosterone in male rats is required for the masculinization of most studied sexually brain structures. Unlike humans, in rats, this is usually through the estrogenic derivatives of testosterone, produced through aromatization, and less often through the androgenic metabolites, like dihydrotestosterone (DHT) (Cooke et al. 1998). To determine whether KCC2 is regulated by gonadal hormones, the effects of systemic administration of testosterone, 17β-estradiol or DHT on KCC2 mRNA expression in PN15 SNR were studied (Galanopoulou and Moshé 2003). Testosterone and DHT increased KCC2 mRNA expression in both male and female PN15 SNR neurons. In contrast, 17β-estradiol decreased KCC2 mRNA in males but not in females. These effects were seen both after short (4 hours) or long periods (52 hours) of exposure to the hormones. However, they occurred only in neurons in which active GABA_A-mediated depolarizations were operative (naïve male PN15 SNR neurons). Estradiol failed to downregulate KCC2 in neurons in which GABA_A receptors or L-type voltage sensitive calcium channels (L-VSCCs) were blocked (bicuculline or nifedipine pretreated PN15 male rat SNR), and in those that had already hyperpolarizing GABA_A signaling (female PN15 SNR neurons). This indicated that 17β-estradiol-mediated downregulation of certain calcium-regulated genes, like KCC2, shows a requirement for active GABA_A-mediated activation of L-VSCCs (Galanopoulou and Moshé 2003). In agreement with this model, in vivo administration of 17β-estradiol decreased pCREB-ir in male but not in female PN15 SNR neurons (Galanopoulou 2006). The idea that the effects of estradiol on chloride cotransporters or GABA_A signaling may depend upon the direction of GABA_A responses is also reverberated in other publications. In hippocampal pyramidal neurons of adult ovariectomized female rats, where GABA_A signaling is thought to be hyperpolarizing, 17β-estradiol had no effect on KCC2 expression (Nakamura et al. 2004). In contrast, in cultured neonatal hypothalamic neurons that still respond with muscimol-triggered calcium rises, thought to be due to the depolarizing effects of GABA_A receptors, 17β-estradiol delays the period with excitatory GABA_A signaling (Perrot-Sinal et al. 2001). However, a direct involvement of KCC2 in this process has not been demonstrated yet. Such findings indicate that GABA_A signaling can not only augment the existing sex differences through pathways directly regulated by its own receptors, but can also interact indirectly and modify the effects of important neurotrophic and morphogenetic factors, like estradiol, at least in some neuronal types (Galanopoulou 2005; Galanopoulou 2006). It is possible that perinatal exposure to higher levels of the estrogenic metabolites produced by the testosterone surge in male pups could be one factor that maintains KCC2 expression lower in males. In agreement, daily administration of 17β-estradiol in neonatal female rat pups, during the first 5 days of life, reduces KCC2 mRNA at postnatal day 15. This does not occur if 17β-estradiol is given only during the first 3 days of postnatal life (personal unpublished data).

Development and regulation of chloride homeostasis in the central nervous system

γ-Aminobutyric acid (GABA) is the main inhibitory neurotransmitter of the mature central nervous system (CNS). The developmental switch of GABAergic transmission from excitation to inhibition is induced by changes in Cl⁻ gradients, which are generated by cation-Cl⁻ co-transporters. An accumulation of Cl⁻ by the Na⁺-K⁺-2Cl⁻ co-transporter (NKCC1) increases the intracellular Cl⁻ concentration ([Cl⁻]_i) such that GABA depolarizes neuronal precursors and immature neurons. The subsequent ontogenetic switch, i.e., upregulation of the Cl⁻-extruder KCC2, which is a neuron-specific K⁺-Cl⁻ co-transporter, with or without downregulation of NKCC1, results in low [Cl⁻]_i levels and the hyperpolarizing action of GABA in mature neurons. Development of Cl⁻ homeostasis depends on developmental changes in NKCC1 and KCC2 expression. Generally, developmental shifts (decreases) in [Cl⁻]_i parallel the maturation of the nervous system, e.g., early in the spinal cord, hypothalamus and thalamus, followed by the limbic system, and last in the neocortex. There are several regulators of KCC2 and/or NKCC1 expression, including brain-derived neurotrophic factor (BDNF), insulin-like growth factor (IGF), and cystic fibrosis transmembrane conductance regulator (CFTR). Therefore, regionally different expression of these regulators may also contribute to the regional developmental shifts of Cl⁻ homeostasis. KCC2 and NKCC1 functions are also regulated by phosphorylation by enzymes such as PKC, Src-family tyrosine kinases, and WNK1–4 and their downstream effectors STE20/SPS1-related proline/alanine-rich kinase (SPAK)-oxidative stress responsive kinase-1 (OSR1). In addition, activation of these kinases is modulated by humoral factors such as estrogen and taurine. Because these transporters use the electrochemical driving force of Na⁺ and K⁺ ions, topographical interaction with the Na⁺-K⁺ ATPase and its modulators such as creatine kinase (CK) should modulate functions of Cl⁻ transporters. Therefore, regional developmental regulation of these regulators and modulators of Cl⁻ transporters may also play a pivotal role in the development of Cl⁻ homeostasis.

PI3K/Akt Signaling Pathway Activates the WNK-OSR1/SPAK-NCC Phosphorylation Cascade in Hyperinsulinemic db/db Mice

The discovery that the dominant inhibitory neurotransmitter, GABA, is also the major source of excitation in the developing brain was so surprising and unorthodox it required years of converging evidence from multiple laboratories to gain general acceptance (Ben-Ari, 2002) and continues to draw challenges some 20 years after the initial reports (Rheims et al., 2009; Waddell et al., 2011). Fundamental developmental endpoints regulated by depolarizing GABA action include giant depolarizing potentials (Ben-Ari etal, 1989), leading to spontaneous activity patterns (Blankenship & Feller, 2010), activity dependent survival (Sauer and Bartos, 2010), neurite outgrowth (Sernagor et al., 2010), progenitor proliferation (Liu et al., 2005), and hebbian-based synaptic patterning (Wang & Kriegstein, 2008). We previously identified an endogenous regulator of depolarizing GABA action, the gonadal and neurosteroid estradiol, which both amplifies the magnitude and extends the developmental duration of excitatory GABA (Perrot-Sinal et al., 2001). Estradiol is a pervasive signaling molecule that varies in concentration between brain regions, across development and in males versus females, thereby contributing to variability in neuronal maturation. The present studies reveal that this steroid enhances depolarizing GABA effects by increasing levels of the signaling kinases SPAK and OSR1, which are upstream of the NKCC1 cotransporter. Estradiol mediated increases in NKCC1 phosphorylation are precluded by antisense oligonucleotide-mediated knockdown of SPAK, and to a lesser extent OSR1, exhibiting the necessity of these kinases for mediating estradiol’s effects. Furthermore, knockdown of either or both of these kinases significantly attenuated estradiol’s enhancement of intracellular Ca²⁺ influx in response to GABA_A activation.

Estradiol has widespread effects on cellular processes through both rapid, nongenomic actions on cell signaling, and slower more enduring effects by modulating transcriptional activity (McEwen, 1991). The combination of a long time course and a complete ablation of the effectiveness of estradiol by simultaneous administration of blockers of transcription or translation confirm that the cascade of events leading to estradiol enhancement of depolarizing GABA begins with increased gene expression. The ability of the brain to synthesize estradiol in discrete loci raises the specter of estrogens as widespread endogenous regulators of depolarizing GABA actions that broadly impact on brain development.

Disregulation in developmental excitatory GABAergic signaling has been shown to impair the development of neuronal circuits and may be a contributing factor in neurodevelopmental disorders such as epilepsy, autism spectrum disorders, and schizophrenia (Briggs and Galanopoulou, 2011; Pizzarelli and Cherubini, 2011; Hyde et al, 2011). Sex differences have been widely reported in all of these disorders, implicating a role for estradiol in their etiology. Targeting SPAK or OSR1 may allow for novel therapeutic options for these neural disorders.

The role of Taurine and TauT

The Japanese paper below suggests that what I have called in this blog, the “GABA switch” is in part mediated by intracellular taurine.

In immature neurons, taurine is taken up into cells through the TauT transporter and activates WNK-SPAK/OSR1 signaling.

TauT is the taurine transporter that lets taurine into cells.

So logically if you blocked the taurine transporter in people with permanently immature neurons, things might improve.

Taurine is present in the embryonic brain by transportation from maternal blood via placental TauT. In addition, fetuses ingest taurine-rich amniotic fluid. Although fetal taurine decreases postnatally, infants receive taurine via breast milk, which contains a high taurine concentration. 

Taurine Inhibits K⁺-Cl⁻ Cotransporter KCC2 to Regulate Embryonic Cl⁻ Homeostasis via With-no-lysine (WNK) Protein Kinase Signaling Pathway

Taurine Inhibits KCC2 Activity via Serine/Threonine Phosphorylation

Because KCC2 is known to be regulated by kinases (15, 17, 54,–,56), phosphorylation-related reagents were used to evaluate the effect on KCC2 activity. The tyrosine kinase inhibitor AG18 and tyrosine phosphatase inhibitor vanadate did not affect E_GABA (supplemental Table 1A). In contrast, the broad spectrum kinase inhibitor staurosporine (Staur) shifted E_GABA toward the negative in 15–20 min in the presence of taurine (control, −45.2 ± 0.3 mV; Staur, −47.6 ± 0.5 mV, n = 5, p = 0.002 (supplemental Fig. 3A and Table 1A). Considering that 1 h of taurine treatment did not have an effect on E_GABA (Fig. 2A), these results suggest that chronic but not acute taurine treatment inhibited KCC2 activity in a serine/threonine phosphorylation-dependent manner. Moreover, staurosporine also shifted KCC2-positive cell E_GABA significantly toward the negative in embryonic brain slices at E18.5 but was less effective in postnatal brain slices at P7 (control, −46.5 ± 0.8 mV; Staur, −51.0 ± 1.1 mV, n = 6, p = 0.007 at E18.5; control, −57.6 ± 1.7 mV; Staur, −59.1 ± 1.6 mV (n = 6, p = 0.06 at P7)) (supplemental Fig. 3B). In contrast, vanadate did not affect E_GABA at either age (supplemental Table 1B).

Hypothetical model of Cl⁻ homeostasis regulated by taurine and WNK-SPAK/OSR1 signaling during perinatal periods. To control the excitatory/inhibitory balance mediated by GABA, [Cl⁻]_i is regulated by activation of the WNK-SPAK/OSR1 signaling pathway via KCC2 inhibition and possibly NKCC1 activation (54, 58, 59). In immature neurons, taurine is taken up into cells through TauT and activates WNK-SPAK/OSR1 signaling (left). Red arrows and T-shaped bars indicate activation and inactivation, respectively. Later (possibly a while after birth), this activation pathway induced by taurine diminishes, resulting in release of KCC/NKCC activity (right), whereas SPAK/OSR1 signaling recovers somewhat upon adulthood. Interestingly, in contrast to kinase signaling leading to KCC2 inhibition, other kinases are also known to facilitate KCC2 activity (see “Discussion”). 

We observed that taurine is implicated in WNK activity. WNK signaling is activated by stimuli, such as osmotic stress; however, the precise pathway leading to activation is unknown (38, 59). Our results indicate that taurine uptake is crucial for WNK activation, and only intracellular taurine activates WNKs, which are also involved in osmoregulation (52). There are no significant osmolarity differences with or without 3 mm taurine (without taurine, 215 ± 2 mosm versus with taurine, 216 ± 4 mosm (n = 4–5, p = 0.41)). In addition, 3 mm GABA did not affect phosphorylation of SPAK/OSR1 (data not shown), which indicates a specific action of taurine. 

KCC2 gene up-regulation is essential for Cl⁻ homeostasis during development, and phosphorylation of KCC2 is another important factor (5, 12, 15, 18, 55, 56). Ser-940 phosphorylation regulates KCC2 function by modulating cell surface KCC2 expression (56). Tyr-1087 phosphorylation affects oligomerization, which plays a pivotal role in KCC2 activity without affecting cell surface expression (20, 55). Rinehart et al. (54) indicated that Thr-906 and Thr-1007 phosphorylation does not affect cell surface KCC2 expression. In our study, oligomerization and plasmalemmal localization were not affected by taurine (data not shown), suggesting that phosphorylation of these sites may provide another mechanism of KCC2 activity modulation. 

A number of neuron types are generated relatively early during embryonic development, such as Cajal-Retzius and subplate cells in the cerebral cortex, which play regulatory roles in migration. Several reports have shown that these early generated neurons in the marginal zone and subplate are activated by GABA and glycine (82,–,85). These early generated neurons can express KCC2 as early as the embryonic and neonatal stages (86). In addition, taurine is enriched in these brain areas (data not shown). Therefore, the present results suggest that KCC2 is not functional due to the distribution of taurine, which affects WNK-SPAK/OSR1 signaling and preserves GABAergic excitation. This signaling cascade may have broader important roles in brain development than previously reported.

Conclusion

I think we have pretty much got to the bottom of the current research on this subject.

There is plenty of ongoing Japanese involvement, which is good news.

You either find the GABA switch and, better late than never, finally activate it, or you modify the downstream processes as a therapy for immature neurons.  

Numerous things affect NKCC1/KCC2; so numerous therapies can potentially treat it.

The really clever solution would be to activate the GABA switch; that part I continue to think about.

Clearly, if you disrupt evolutionary processes like oxytocin and taurine passed from mother to baby there may be unexpected consequences.

Unusual levels of both male and female hormones and expression of estrogen/androgen receptors do play a role in the balance between NKCC1/KCC2 and so the level of chloride and hence how GABA behaves.

Inhibitors of WNK, SPAK and OSR1 are all promising potential therapies and I think these will emerge, since the big money of autism research is already backing this idea.

The TauT transporter is another possible target.

Hormone related options include a selective estrogen receptor beta agonist, an androgen receptor antagonist, and estradiol.  Unfortunately such therapy is quite likely to have unwanted side effects. So-called phytoestrogens like EGCG, from green tea, covered in a recent post are not very potent but if you had enough might show some effect.

For many reasons it looks like many people with autism could do with some more PKC (Protein Kinase C).