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Showing posts with label Mast cells. Show all posts
Showing posts with label Mast cells. Show all posts

Tuesday 16 January 2018

How much Histidine? Dermatitis and FLG mutations


Today’s post is not about autism, it is about allergy and atopic dermatitis in particular.
Many people are affected by atopic dermatitis (AD), also known as eczema; it is particularly common in those with autism. Children who develop asthma have often first developed atopic dermatitis (AD).
Atopic Dermatitis is another of those auto-immune conditions and the sooner you stabilize such conditions the better the prognosis.




Skin therapies from a company
spun-off from Manchester University


Histidine
A while back on this blog I was looking at the various amino acids and came across the observation that histidine, a precursor of histamine, appears to be a mast cell stabilizer. Mast cells are the ones that release histamine and IL-6 into your blood. Histamine then does on the trigger yet more IL-6 to be produced.  IL-6 is a particularly troublesome pro-inflammatory cytokine.
At first sight giving a precursor of histamine to people who want less histamine seems a crazy thing to do, but plenty of people report their allergies improving after taking histidine. As we have discovered, feedback loops are very important in human biology and these can be used sometimes to trick the body into doing what you want it to do. Having a higher level of histidine in your blood might make histamine production easier but it might also be telling the body not to bother, or just to delay mast cells from degranulating.  Whatever the mechanism, it does seem to work for many people. 

How Much Histidine?
Most histidine pills are 0.5g and it appears people use about 1g to minimize their allergy. 1g is the dose Monty, aged 14 with ASD, has been using during the pollen allergy season.
My sister recently highlighted a new "high tech" OTC product for skin conditions, Curapella/Pellamex, its main ingredient is histidine and it is a lot of histidine, 4g.




The company that produces the supplement have teamed up with the Universities of Edinburgh and Manchester to make a clinical trial, which is featured below.
They are considering the interaction between histidine and filaggrine (produced by the FLG gene). 

Mutations in the FLG gene are associated with atopic dermatitis and indeed with asthma, hay fever, food allergies, and, rather bizarrely, skin sensitivity to nickel.
In effect it is suggested that histidine makes filaggrine work better and thus atopic dermatitis and some other skin conditions will improve.  



Atopic dermatitis (AD), also known as eczema, is one of the most common chronic skin conditions worldwide, affecting up to 16% of children and 10% of adults. It is incurable and has significant psychosocial and economic impacts on the affected individuals. AD etiology has been linked to deficiencies in the skin barrier protein, filaggrin. In mammalian skin, l-histidine is rapidly incorporated into filaggrin. Subsequent filaggrin proteolysis releases l-histidine as an important natural moisturizing factor (NMF). In vitro studies were conducted to investigate the influence of l-histidine on filaggrin processing and barrier function in human skin-equivalent models. Our further aim was to examine the effects of daily oral l-histidine supplementation on disease severity in adult AD patients. We conducted a randomized, double-blind, placebo-controlled, crossover, nutritional supplementation pilot study to explore the effects of oral l-histidine in adult AD patients (n=24). In vitro studies demonstrated that l-histidine significantly increased both filaggrin formation and skin barrier function (P<0 .01="" respectively="" span="" style="background: yellow; margin: 0px;">Data from the clinical study indicated that once daily oral l-histidine significantly reduced (P<0 .003="" 34="" 39="" 4="" ad="" after="" and="" assessment="" by="" disease="" eczema="" measure="" of="" oriented="" patient="" physician="" scoringad="" self-assessment="" severity="" span="" the="" tool="" treatment="" using="" weeks="">. No improvement was noted with the placebo (P>0.32). The clinical effect of oral l-histidine in AD was similar to that of mid-potency topical corticosteroids and combined with its safety profile suggests that it may be a safe, nonsteroidal approach suitable for long-term use in skin conditions that are associated with filaggrin deficits such as AD. 
In this paper, we suggest that a simpler, nutritional supplementation of l-histidine may have a beneficial potential in AD.

l-histidine is a proteinogenic amino acid that is not synthesized by mammals. In human infants, it is considered “essential” due to low levels of histidine-synthesizing gut microflora and minimal carnosinase activity, which helps in releasing free l-histidine from carnosine.24 Our interest in the use of l-histidine in AD was stimulated by several observations. Firstly, in both infants and adults, a histidine-deficient diet results in an eczematous rash.25 In rodents, 3H-histidine is rapidly (1–2 hours) incorporated into profilaggrin within keratohyalin granules after intraperitoneal or intradermal injection14,26 and within 1–7 days is released as a free NMF amino acid in the upper stratum corneum.14 Furthermore, reduced stratum corneum levels of free NMF amino acids, including histidine and its acidifying metabolite urocanic acid (UCA), are associated with AD disease severity and FLG genotype.27,28

Given this evidence for the dependence of filaggrin processing and NMF formation on suitable levels of l-histidine, we hypothesized that l-histidine would both enhance filaggrin processing in an in vitro, organotypic, human skin model and have beneficial effects as a nutritional supplement in subjects with atopic dermatitis. 

After a 2-week wash-out period in which subjects were asked not to use any medicinal product for their AD, the same measures were repeated and patients were provided with identical sachets containing either 4 g l-histidine (Group A) or 4 g placebo (erythritol); Group B) which was taken once a day, dissolved in a morning fruit drink.  





Conclusion

It looks like 4g of histidine has the same potency as mild topical steroid creams, when treating atopic dermatitis.
The big problem with topical steroids is that you can only use them for a week or two. It you use them for longer, you end up with a bigger problem than the one you were trying to treat.
The 4g a day of histidine is put forward as a safe long term therapy.
Is the mode of action related to mast cells or filaggrin (FLG)? Or perhaps both?
If 1g of histidine does improve your allergies, perhaps you should feel free to try a little more.
You can buy histidine as a bulk powder. Pellamex is quite expensive, particularly if more than one family member is affected, as you would expect to find in a genetic condition.  




Tuesday 13 June 2017

Eosinophilic Esophagitis – another Granulocyte Disorder Associated with Autism  


There are many comorbidities associated with autism.  I have long held the view that these comorbidities hold the key to understanding each particular case of autism.  In many cases this may be far more useful than genetic testing, which only seems to help in a minority of cases.

“Ringed esophagus” aka “Corrugated esophagus”


This then allows you to put people into sub-groups that may well respond to the same therapy.  This may all sound like common sense, but apparently is not.

Eosinophilic esophagitis (EoE) is a relatively new diagnosis and it is applies to a certain type of reflux/GERD/GORD that might be associated with a difficulty in swallowing and may not respond well to the standard stomach acid lowering therapies.

It is likely that most people with Eosinophilic esophagitis have never been correctly diagnosed. Many people have taken several years to get the correct diagnosis.

It is known that Eosinophilic esophagitis is much more common in autism than the general population. One study showed that EoE is four time more likely to be diagnosed in someone with autism. I suspect many people with autism never have their GI problems fully diagnosed.

We now have to add some new science to this blog


Granulocytes

There is a great deal already in this blog about mast cells.  Many readers have children who have allergies, mast cell activation, or even mastocytosis.  Mast cells are the ones (but not the only ones) that release histamine.

Mast cells are just one type of a class of cells called Granulocytes, that are produced in your bone marrow.

Granulocytes are a category of white blood cells characterized by the presence of granules, which release their contents when they degranulate.

The four types of granulocytes are:- 


·        mast cells

These have been well covered in the past. These are what cause problems for people with pollen allergy.


·        eosinophils

Eosinophils play a crucial part in the killing of parasites because their granules contain a unique, toxic basic protein and cationic protein. Eosinophils regulate other immune cell functions (e.g., CD4+ T cells, dendritic cells, B cells, mast cells, neutrophils, and basophils), they are involved in the destruction of tumor cells, and they promote the repair of damaged tissue. Interleukin-5 interacts with eosinophils and causes them to grow and differentiate; IL-5 is produced by basophils.

Note that some people with autism find that the TSO helminth parasites modify their immune system and improve their autism. This may relate to what is contained in the granules of eosinophils.  


·        basophils 

Basophils are similar to mast cells, in that they contain prestored histamine within their granules. Unlike mast cells they circulate in your blood . Basophils are the least common of the granulocytes, representing about 0.5 to 1% of circulating white blood cells. However, they are the largest type of granulocyte. They are responsible for inflammatory reactions during immune response, as well as in the formation of acute and chronic allergic diseases, including anaphylaxis, asthma, atopic dermatitis and hay fever. They can produce histamine and serotonin that induce inflammation, and heparin that prevents blood clotting.

There is research underway to try to develop basophil stabilizers.


·        neutrophils

Neutrophils are normally found in the bloodstream. During the beginning phase of inflammation, particularly as a result of bacterial infection, environmental exposure, and some cancers, neutrophils are one of the first-responders of inflammatory cells to migrate towards the site of inflammation.

Neutrophils are recruited to the site of injury within minutes following trauma, and are the hallmark of acute inflammation; however, due to some pathogens being indigestible, they can be unable to resolve certain infections without the assistance of other types of immune cells.

Neutrophils also release an assortment of proteins in three types of granules by a process called degranulation. The contents of these granules have antimicrobial properties, and help combat infection.


An obvious question would be, if you know you have a problem with mast cells are you likely to have an issue with the other types of granulocytes?

One role of eosinophils is to regulate other immune cell functions (e.g., CD4+ T cells, dendritic cells, B cells, mast cells, neutrophils, and basophils).

The subject is highly complex and again not fully understood, but it is clear that granulocytes are all interrelated and so a problem with one may well be associated with a problem with others.

In the case of Eosinophilic esophagitis (EoE), both eosinophils and mast cell are directly involved.

Basophils, like mast cells, release histamine among other things when they degranulate.

Mast cells usually do not circulate in the blood stream, but instead are located in connective tissue.  Circulating granulocytes, like basophils can be recruited out of the blood into a tissue when needed.

So in addition to mast cell stabilizers perhaps, we might benefit from basophil and eosinophil stabilizers.

Surprisingly, the antihistamine cetirizine has Eosinophil-stabilizing properties, as does the asthma drug Montelukast. Both drugs are widely used in children.

Another substance, curine, also inhibits eosinophil influx and activation and is seen as a potential new treatment for asthma.  Interestingly the drug curine, is an alkaloid, that blocks L-type Ca²⁺ channels.

Regular readers may recall that I proposed the L-type calcium channel blocker Verapamil to control my son’s mast cell degranulation. Mast cells degranulate in a very complex fashion that involves the flow of Ca²⁺.

This may or may not be a coincidence. 

Fullerene nanomaterials are being developed as both mast cell and peripheral blood basophil stabilizers.



L-type calcium channels and GI disorders in Autism

There are many types of GI disorder in autism, however I suggest that a large group can be categorized as being broadly Granulocyte Disorders, which may well all respond to L-type calcium channel blockers, to some extent.

Indeed this may be a better solution than the widely used cromolyn sodium.

Perhaps people with autism, and their family members have certain calcium channels that are either overexpressed, or do not close fast enough, leading to a higher level of intracellular calcium.  This of course ties back in with Professor Gargus and his theories about IP3R and the calcium store inside the endoplasmic reticulum”.

This all gets extremely complex.

My rather simple suggestion would be that if you have autism and any GI problem from the esophagus downwards, a three day trial of verapamil just might change your life.  As is almost always the case, there are some people who do not tolerate verapamil.



Interleukin 5

Interleukin 5 (IL-5) is an inflammatory cytokine produced by type-2 T helper cells  (Th2), mast cells, basophils and eosinophils.

IL-5 interacts with eosinophils and causes them to grow and differentiate.

IL-5 has long been associated with the cause of several allergic diseases including allergic rhinitis and asthma, where a large increase in the number of circulating, airway tissue, and induced sputum eosinophils have been observed.

You might expect high levels of IL-5 in people with Eosinophilic esophagitis (EoE)



Anti–IL-5 therapy is associated with marked decreases in peripheral blood and esophageal eosinophilia (including the number of CCR3+ blood cells) in patients with EE and improved clinical outcomes.


Not surprisingly the same anti-IL-5 therapy has been approved to treat severe asthma.


Patients are given mepolizumab by injection every four weeks. It costs £840 per dose.



Mepolizumab for autism?

It is very expensive, so I doubt many people will think of Mepolizumab for autism.  If you have EoE, or severe asthma, you may be able to access this IL-5 therapy, my guess is that it would also reduce the severity of any comorbid autism.


Back to Eosinophilic Esophagitis

I was writing a while ago about food allergy in my book and came across the opinion that food allergy is no more common in autism than in typical people, but what is more common is Eosinophilic Esophagitis.

Eosinophilic esophagitis is a chronic immune system disease. It has been identified only in the past two decades, but is now considered a major cause of digestive system (gastrointestinal) illness.  In many cases it likely remains undiagnosed. If it continues, after a few years swallowing becomes difficult, in part because a “ringed esophagus” develops that impedes the passage of food.

As seems to be often the case there are plenty of contradictions in the diagnosis and treatment, as you will find as you read on.

The symptoms are broadly what would normally be diagnosed as reflux/GERD/GORD. This is very often found in people with autism and I expect in their relatives.

It is relevant to autism because it will be yet another comorbidity that when treated should improve autism, but it is also another marker of a particular sub-group of autism.

There are numerous other GI conditions comorbid with autism - colitis, IBD, IBS etc.  In the end I imagine that the molecular basis of some of these diagnoses is actually the same, so you will find the same therapies may be effective.

It looks like that one common factor is the mast cell and, just as in pollen allergy and asthma, stabilizing mast cells yields great benefit. Stabilizing mast cells is complex but involves the flow of calcium ions, Ca2+.  By modifying the flow of Ca2+ you can prevent mast cells degranulating.  This was one of my earlier discoveries, but there is now research showing the L type calcium channels “open” mast cells.  Keeping these channels closed is actually quite simple.

It would seem logical that the same approach could be therapeutic to other conditions that are, at least in part, mediated by mast cells.

According to the Mayo Clinic these are symptoms of eosinophilic-esophagitis


Adults:

·         Difficulty swallowing (dysphagia)

·         Food impaction

·         Chest pain that is often centrally located and does not respond to antacids

·         Persistent heartburn

·         Upper abdominal pain

·         No response to gastroesophageal reflux disease (GERD) medication

·         Backflow of undigested food (regurgitation)


Children:

·         Difficulty feeding

·         Vomiting

·         Abdominal pain

·         Difficulty swallowing (dysphagia)

·         Food impaction

·         No response to GERD medication

·         Failure to thrive (poor growth, malnutrition and weight loss)


The diagnosis of EoE is typically made on the combination of symptoms and findings of diagnostic testing.


Prior to the development of the EE Diagnostic Panel, EoE could only be diagnosed if gastroesophageal reflux did not respond to a six-week trial of twice-a-day high-dose proton-pump inhibitors (PPIs) or if a negative ambulatory pH study ruled out gastroesophageal reflux disease (GERD).

Treatment strategies include dietary modification to exclude food allergens, medical therapy, and mechanical dilatation of the esophagus.

The current recommendation for first line treatment is PPI in lieu of diet as a significant portion of EOE cases respond to this, and it is a low risk, low cost treatment.

The second and third line therapies are an elimination diet of either the 6 or 4 most common triggers, or topical corticosteroids, including both fluticasone, and topical viscous budesonide.

Elimination diets would be followed by re-introduction of foods under supervision if the first diet is successful. Allergy evaluation has not been found to be an effective means to determine what foods to eliminate.

  


MAST CELL STABILIZERS

In a small case series, Cromolyn sodium failed to show any clinical or histologic improvement in EoE patients

LEUKOTRIENE INHIBITORS

Montelukast is an eosinophil stabilizing agent. It improved clinical symptoms in EoE but there was no histological improvement

PROGNOSIS

As mentioned earlier, EoE is a chronic inflammatory disease of the esophagus. The inflammation leads to remodeling, fibrosis and stricture. Fortunately, no case of esophageal malignancy has been reported in EoE. Patients are generally diagnosed after several years of their symptoms. Although symptomatic improvement occurs after treatment, recurrence is common after discontinuation of treatment. So maintenance therapy is needed to prevent recurrences. At the present time there is no head to head study to suggest the best maintenance treatment. Continuation of swallowed corticosteroid and/or dietary therapy should be done in all EoE patients particularly in those with history of food impaction, dysphagia, esophageal stricture, and in those with rapid symptomatic and histologic relapse following initial treatment



Eosinophilic esophagitis and Mast Cells

Eosinophilic esophagitis is called Eosinophilic because it is mediated by Eosinophils, however it has been established that mast cells also play a role. 



Whereas prior studies have primarily focused on the role of eosinophils in disease diagnosis and pathogenesis, this study investigates the involvement of mast cells.

Herein we have identified local mastocytosis and mast cell degranulation in the esophagus of EE patients; identified an esophageal mast cell associated transcriptome that is significantly divergent from the eosinophil-associated transcriptome with CPA3 mRNA levels serving as the best mast cell surrogate marker; and provide evidence for the involvement of KIT ligand in the pathogenesis of EE.


One possible explanation for eosinophilic esophagitis:















A potential immunological mechanism involved in the pathogenesis of EoE. An uncontrolled TH2 immune response initiated by an allergic insult results in the transition of the esophagus from a normal (NL) to EoE phenotype through enhanced IL-13 production that induces highly elevated CCL26 (eotaxin-3) expression by esophageal epithelium. Dysregulated TH2 immune response and enhanced CCL26 secretion together promote the infiltration of CD4+TH2 cells, eosinophils, and mast cells, and potentially, type-2 innate lymphoid cells (ILC2) and CD4+TH9 cells; into the esophagus. TGF-β and IL-4 produced by the activated mast cells and CD4+TH2 cells may induce eosinophils, ILC2, and/or CD4+TH9 cells to produce IL-9, which in turn, promotes esophageal mastocytosis that contributes to the development of EoE pathophysiology.



Possible Eosinophil stabilizers


CONCLUSIONS Eosinophil-stabilizing properties and favorable safety profile make cetirizine an attractive add-on therapy for NMO. Thus far it has been well-tolerated in our patient population, with incoming data about efficacy expected over the coming months




·        Curine is a bisbenzylisoquinoline alkaloid from Chondrodendron platyphyllum.

·        Curine inhibits eosinophil influx and activation and airway hyper-responsiveness.

·        Curine mechanisms involve inhibition of Ca2+ influx, and IL-13 and eotaxin secretion.

·        No significant toxicity was observed in mice orally treated with curine for 7 days.

·         Curine has the potential for the development of anti-asthmatic drugs.

  

Conclusion

Non conventional therapies for eosinophilic esophagitis might include:-


·        Cetirizine

·        Verapamil

·        Montelukast

·        Curine

The very expensive therapy is Mepolizumab.

If you have one type granulocyte causing a disorder, is seems almost inevitable that the other types of granulocyte are also involved.

Treating granulocyte disorders should improve autism and left untreated they may mask the effect of otherwise useful autism therapies. 

One reader did previously suggest a bone marrow transplant for autism. A rather radical solution, but if someone with autism was given donor bone marrow as part of another therapy, you might well see their autism improve.










Wednesday 4 January 2017

Histidine for Allergy, but as an effective MTOR inhibitor?



Today’s post is likely to be of interest to those dealing with allergy and mast cell activation, but it may have broader implications for those with excess brain mTOR activity.
In the jargon, we are told that:
enhanced mammalian target of rapamycin (mTOR) signaling in the brain has been implicated in the pathogenesis of autism spectrum disorder”.
I have discussed mTOR and mTOR inhibitors previously on this blog.



Amino acids, not just for body builders?


mTOR plays a key role in aging and many human diseases ranging from cancer, diabetes and obesity to autism and Alzheimer’s.

The greatest interest in mTOR seems to be in cancer care.  Many cancer genes and pathways are also involved in autism, so we can benefit from the cancer research.  Another autism gene that is also a cancer gene is PTEN.  PTEN is a tumor suppressor and in the most common male cancer, prostate cancer (PCa), what happens is that PTEN gets turned off and so the cancer continues to grow.  If you upregulate PTEN you slow the cancer growth and if you upregulated this gene in those people at risk of Pca perhaps they would never develop this cancer in the first place?  PTEN is upregulated by statin-type drugs and people already on this type of drug have better PCa prognoses.   The beneficial of effect of statins on PCa is known, but the mechanism being PTEN upregulation does not seem to have been noticed. No surprise there.

Inhibiting mTOR using cancer drugs is very expensive.

Other substances affecting mTOR include amino acids, growth factors, insulin, and oxidative stress.

The amino acid Leucine is an mTOR activator, we don’t need that.  We actually want the opposite effect and, at least in mice, we can get it from some of the other amino acids. 


          Highlights 

·        Amino acids, his, lys and thr, inhibited mTOR pathway in antigen-activated mast cells



·        Amino acids, his, lys and thr inhibited degranulation and cytokine production of mast cells



·        Amino acid diet reversed mTOR activity in the brain and behavioral deficits in allergic and BTBR mice.



Neuroprotective and anti-inflammatory diet reduced behavioral deficits only in allergic mice.

              Abstract

Enhanced mammalian target of rapamycin (mTOR) signaling in the brain has been implicated in the pathogenesis of autism spectrum disorder (ASD). Inhibition of the mTOR pathway improves behavior and neuropathology in mouse models of ASD containing mTOR-associated single gene mutations. The current study demonstrated that the amino acids histidine, lysine, threonine inhibited mTOR signaling and IgE-mediated mast cell activation, while the amino acids leucine, isoleucine, valine had no effect on mTOR signaling in BMMCs. Based on these results, we designed an mTOR-targeting amino acid diet (Active 1 diet) and assessed the effects of dietary interventions with the amino acid diet or a multi-nutrient supplementation diet (Active 2 diet) on autistic-like behavior and mTOR signaling in food allergic mice and in inbred BTBR T + Itpr3tf/J mice. Cow’s milk allergic (CMA) or BTBR male mice were fed a Control, Active 1, or Active 2 diet for 7 consecutive weeks. CMA mice showed reduced social interaction and increased self-grooming behavior. Both diets reversed behavioral impairments and inhibited the mTOR activity in the prefrontal cortex and amygdala of CMA mice. In BTBR mice, only Active 1 diet reduced repetitive self-grooming behavior and attenuated the mTOR activity in the prefrontal and somatosensory cortices. The current results suggest that activated mTOR signaling pathway in the brain may be a convergent pathway in the pathogenesis of ASD bridging genetic background and environmental triggers (food allergy) and that mTOR over-activation could serve as a potential therapeutic target for the treatment of ASD.

  

So in mice a combination of the three amino acids Histidine, Lysine and Threonine reduced brain mTOR activity and improved autism.

I did look at all three of these amino acids and their other effects and I choose Histidine. 
Histidine can be produced in adult humans in very small amounts, but in young children they need to obtain some from other sources, usually dietary.

Histidine is the precursor of histamine.  Histamine has both good and bad effects.

Histidine decarboxylase (HDC) is the enzyme that catalyzes the reaction that produces histamine from histidine with the help of vitamin B6 as follows:



You can treat allergy by inhibiting HDC.

Tritoqualine, is an inhibitor of the enzyme histidine decarboxylase and therefore an atypical antihistamine,

You might think that having extra histidine would result in extra histamine, but this appears not to be the case.  There is a paradoxical reaction where increasing histadine actually seems to reduce the release of histamine from the mast cells that store it.  This may indeed be a case of feedback loops working in our favour.

So it seems that histidine may give two different benefits, it reduces IgE-mediated mast cell activation and it reduces mTOR signalling in the brain.

If the effect on mTOR is sufficient we would then benefit from an increase in autophagy, the cellular garbage disposal service that does not work well in autism.  We might eventually see a benefit from increased synaptic pruning which might be seen in improved cognition.  



Recap on mTOR and Synaptic Pruning

This has been covered in earlier posts.

In autism loss of mTOR-dependent macro-autophagy causes synaptic pruning deficits; this results in too many dendritic spines.









A dendritic spine (or spine) is a small membranous protrusion from a neuron's dendrite that typically receives input from a single axon at the synapse. Dendritic spines serve as a storage site for synaptic strength and help transmit electrical signals to the neuron's cell body. The dendrites of a single neuron can contain hundreds to thousands of spines. In addition to spines providing an anatomical substrate for memory storage and synaptic transmission, they may also serve to increase the number of possible contacts between neurons.

A feature of autism is usually too many, but can be too few, dendritic spines.  In an earlier post we saw how the shape of individual spines affects their function.  The shape is constantly changing and can be influenced by external therapy. Wnt signaling affects dendritic spine morphology and so using this pathway you could fine-tune dendritic spine shape.  We did look at PAK1 inhibitors in connection with this.

Synaptic pruning is an ongoing process well into adolescence.

So it may be possible to improve synapse density and structure well after the onset of autism.

It should be noted that using Rapalogs, the usual mTOR inhibiting drugs, would have a negative effect in the minority of autism that feature hypo-active growth signalling.  That would be people born with small heads and small bodies.  So a child affected by the zika virus, might very likely exhibit autism and ID, but likely has too few dendritic spines and would then need more mTOR, rather than less.

Rapalog drugs like Everolimus are very expensive, but as in this recent paper do show effect in some autism. 



The mTOR pathway is a central regulator of mammalian metabolism and physiology, with important roles in the function of tissues including liver, muscle, white and brown adipose tissue, and the brain, and is dysregulated in human diseases, such as diabetes, obesity, depression, and certain cancers.

mTOR Complex 1 (mTORC1) is composed of MTOR, regulatory-associated protein of MTOR (Raptor), mammalian lethal with SEC13 protein 8 (MLST8) and the non-core components PRAS40 and DEPTOR. This complex functions as a nutrient/energy/redox sensor and controls protein synthesis. The activity of mTORC1 is regulated by rapamycin, insulin, growth factors, phosphatidic acid, certain amino acids and their derivatives (e.g., L-leucine and β-hydroxy β-methylbutyric acid), mechanical stimuli, and oxidative stress

Rapamycin inhibits mTORC1, and this appears to provide most of the beneficial effects of the drug (including life-span extension in animal studies). Rapamycin has a more complex effect on mTORC2.



How do amino acids affect mTOR?

This is not fully understood by anyone, but here is a relevant paper, for those interested.




Mammalian target of rapamycin (mTOR) controls cell growth and metabolism in response to nutrients, energy, and growth factors. Recent findings have placed the lysosome at the core of mTOR complex 1 (mTORC1) regulation by amino acids. Two parallel pathways, Rag GTPase-Ragulator and Vps34-phospholipase D1 (PLD1), regulate mTOR activation on the lysosome. This review describes the recent advances in understanding amino acid-induced mTOR signaling with a particular focus on the role of mTOR in insulin resistance.

We then discuss how mTORC1 activation by amino acids controls insulin signaling, a key aspect of body metabolism, and how deregulation of mTOR signaling can promote metabolic disease. 

Concluding remarks


Recent findings of new mediators and their regulatory mechanisms have broadened our understanding of amino acid-induced mTOR signaling. In addition to the role of the TSC1-TSC2-Rheb hub in transducing upstream signals from growth factors, stressors and energy to mTOR, the lysosomal regulation of mTOR functions as a platform to connect nutrient signals to the Rheb axis. Furthermore, two parallel pathways of amino acid signaling explain the diverse regulation of mTOR signaling. It is yet to be determined which regulators sense amino acids directly and whether the two pathways require separate amino acid sensing mechanisms. The identification of a direct amino acid sensor will shed light on these uncertainties.

A more integrated understanding of mTOR regulation in amino acid signaling will open the door for new therapeutic approaches for metabolic diseases, especially type 2 diabetes. Already, metformin, an antidiabetic drug, inhibits mTOR in an AMP-activated kinase (AMPK)-independent and Rag-dependent manner,64 providing further support for the idea that the regulation of amino acid sensing could be a therapeutic target for diabetes.



How typical is the level of amino acids in autism?



As regards essential amino acid levels, autistic children had significant lower plasma levels of leucine, isoleucine, phenylalanine, methionine and cystine than controls (P < 0.05),while there was no statistical difference in the level of tryptophan, valine, threonine, arginine, lysine and histidine (P > 0.05). In non-essential amino acid levels, phosphoserine was significantly raised in autistic children than in controls (P < 0.05). Autistic children had lower level of hydroxyproline, serine and tyrosine than controls (P < 0.05). On the other hand there was no significant difference in levels of taurin, asparagine, alanine, citrulline, GABA, glycine, glutamic acid, and ornithine (P > 0.05).

There was no significant difference between cases and controls as regards the levels of urea, ammonia, total proteins, albumin and globulins (alpha 1, alpha 2, beta and gamma) (P > 0.05).



  

Conclusion 

For the more common hyperactive pro growth signaling pathway types of autism, histidine should be a good amino acid, whereas for the hypoactive type, that might feature microcephaly, leucine should be a good choice.

Histidine is already used by some people to treat allergy.

Histidine does have numerous other functions and one relates to zinc, so it is suggested that people who supplement histidine add a little zinc. For this reason German histidine supplements thoughtfully all seem to include zinc.

Histidine also has some direct antioxidant effects and has an effect on Superoxide dismutase (SOD).

It is not clear how much histidine would be needed in humans to achieve the mTOR inhibiting effect found in mice.

The RDA for younger teenagers is histidine  850 mg and leucine 2450 mg.  What the therapeutic dose to affect mTOR in humans remains to be seen.

Histidine is also claimed to help ulcers, which is plausible.

For allergy some people are taking 1,500mg of histidine a day.