Pterostilbene for Neuromodulation – worth a look?

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A common criticism of this blog is that it is mainly about prescription drugs rather than OTC supplements.

Today’s post is about a supplement that is highly regarded by our reader Ling.

Pterostilbene is like a super potent version of resveratrol.  

Resveratrol is quite well known and has long been put forward as having some potentially highly beneficial health effects, but in practise it is just too poorly absorbed to have much effect in humans.

Pterostilbene is found in blueberries.  Also found in blueberries is Anthocyanin, which is worth a mention in this post, it is what gives blueberries their colour; very often it is the colour in a food that underlies part of its health benefit. This is why eating a mixed colour diet is a wise idea.

Aronia is extremely rich in anthocyanins and Aronia juice is very common where I live. We even have a bottle of the dark coloured juice in the kitchen.

The purple colour in beetroot is betanin, a so-called betacyanin and may well have anti-Alzheimer’s effects, inhibiting plaque formation.

Anthocyanin is put forward as one reason certain Japanese who eat large amounts of purple sweet potato do not suffer much cancer or dementia and live a very long time.

The Okinawan Diet and Anthocyanin

Today we are mainly looking at pterostilbene, but if you want Anthocyanins, to avoid dementia, just eat blue and purple coloured fruit and vegetables on a very regular basis.

Ling has proposed pterostilbene as a PDE4 inhibitor, but as is often the case, it has numerous other effects, so it would be hard to know which is the main reason it might be therapeutic.  

Known biological effects of Pterostilbene                                                                                   

Here is an excellent graphic that highlights many of the effects of Pterostilbene, other than on PDE4.

The regular readers of this blog will note that the great majority of the above signalling molecules are implicated in autism.

The proposed effects on the brain are highlighted in the next graphic

The source paper is here: -  

Effects of pterostilbene and resveratrol on brain and behavior

           

Based on the evidence presented, PTE (Pterostilbene) is more bioavailable and better at evoking molecular and functional events than RES (Resveratrol) in vivo. 

Although clinical trials are underway to assess the effects of RES in diseases such as dementia and AD, pre-clinical and clinical studies on PTE have yet to be conducted. Furthermore, the biological effects of many of the structural analogues of RES and PTE are unknown, and no studies have identified the metabolites of RES or PTE in brain tissues. There is a need for future studies to identify means of enhancing the efficacy and bioavailability of these compounds and to analyse the metabolites of these compounds in thebrain. Altogether, the evidence from a variety of studies strongly suggests the potential of RES and PTE as promising bioactive agents to improve brain health and prevent neurodegeneration. 

Most research, but not all, concerns aging and dementia. 

A Review of Pterostilbene Antioxidant Activity and Disease Modification

Pterostilbene (trans-3,5-dimethoxy-4-hydroxystilbene) is a natural dietary compound and the primary antioxidant component of blueberries. It has increased bioavailability in comparison to other stilbene compounds, which may enhance its dietary benefit and possibly contribute to a valuable clinical effect. Multiple studies have demonstrated the antioxidant activity of pterostilbene in both in vitro and in vivo models illustrating both preventative and therapeutic benefits. The antioxidant activity of pterostilbene has been implicated in anticarcinogenesis, modulation of neurological disease, anti-inflammation, attenuation of vascular disease, and amelioration of diabetes. In this review, we explore the antioxidant properties of pterostilbene and its relationship to common disease pathways and give a summary of the clinical potential of pterostilbene in the prevention and treatment of various medical conditions.

Resveratrol, pterostilbene, and dementia

Resveratrol is a natural phytoestrogen with neuroprotective properties. Polyphenolic compounds including resveratrol exert in vitro antioxidant, anti-inflammatory, and antiamyloid effects. Resveratrol and its derivative pterostilbene are able to cross the blood-brain barrier and to influence brain activity. The present short review summarizes the available evidence regarding the effects of these polyphenols on pathology and cognition in animal models and human subjects with dementia. Numerous investigations in cellular and mammalian models have associated resveratrol and pterostilbene with protection against dementia syndromes such as Alzheimer's disease (AD) and vascular dementia. The neuroprotective activity of resveratrol and pterostilbene demonstrated in in vitro and in vivo studies suggests a promising role for these compounds in the prevention and treatment of dementia. In comparison to resveratrol, pterostilbene appears to be more effective in combatting brain changes associated with aging. This may be attributed to the more lipophilic nature of pterostilbene with its two methoxyl groups compared with the two hydroxyl groups of resveratrol. The findings of available intervention trials of resveratrol in individuals with mild cognitive impairment or AD do not provide evidence of neuroprotective or therapeutic effects. Future clinical trials should be conducted with long-term exposure to preparations of resveratrol and pterostilbene with high bioavailability.

Low-dose pterostilbene, but not resveratrol, is apotent neuromodulator in aging and Alzheimer's disease.

Recent studies have implicated resveratrol and pterostilbene, a resveratrol derivative, in the protection against age-related diseases including Alzheimer's disease (AD). However, the mechanism for the favorable effects of resveratrol in the brain remains unclear and information about direct cross-comparisons between these analogs is rare. As such, the purpose of this study was to compare the effectiveness of diet-achievable supplementation of resveratrol to that of pterostilbene at improving functional deficits and AD pathology in the SAMP8 mouse, a model of accelerated aging that is increasingly being validated as a model of sporadic and age-related AD. Furthermore we sought to determine the mechanism of action responsible for functional improvements observed by studying cellular stress, inflammation, and pathology markers known to be altered in AD. Two months of pterostilbene diet but not resveratrol significantly improved radial arm water maze function in SAMP8 compared with control-fed animals. Neither resveratrol nor pterostilbene increased sirtuin 1 (SIRT1) expression or downstream markers of sirtuin 1 activation. Importantly, markers of cellular stress, inflammation, and AD pathology were positively modulated by pterostilbene but not resveratrol and were associated with upregulation of peroxisome proliferator-activated receptor (PPAR) alpha expression. Taken together our findings indicate that at equivalent and diet-achievable doses pterostilbene is a more potent modulator of cognition and cellular stress than resveratrol, likely driven by increased peroxisome proliferator-activated receptor alpha expression and increased lipophilicity due to substitution of hydroxy with methoxy group in pterostilbene                                                                                                        

Effect of resveratrol and pterostilbene on aging and longevity.

Over the past years, several studies have found that foods rich in polyphenols protect against age-related disease, such as atherosclerosis, cardiovascular disease, cancer, arthritis, cataracts, osteoporosis, type 2 diabetes (T2D), hypertension and Alzheimer's disease. Resveratrol and pterostilbene, the polyphenol found in grape and blueberries, have beneficial effects as anti-aging compounds through modulating the hallmarks of aging, including oxidative damage, inflammation, telomere attrition and cell senescence. In this review, we discuss the relationship between resveratrol and pterostilbene and possible aging biomarker, including oxidative stress, inflammation, and high-calorie diets. Moreover, we also discuss the positive effect of resveratrol and pterostilbene on lifespan, aged-related disease, and health maintenance. Furthermore, we summarize a variety of important mechanisms modulated by resveratrol and pterostilbene possibly involved in attenuating age-associated disorders. Overall, we describe resveratrol and pterostilbene potential for prevention or treatment of several age-related diseases by modulating age-related mechanisms.

One area of autism research concerns targeting mTOR signalling. This is covered in the paper below

Reversing autism by targeting downstream mTOR signalling

and was the subject of this blog post from 2015

https://epiphanyasd.blogspot.com/2015/06/mtor-indirect-inhibition-holy-grail-for.html

Targeting the PI3K/Akt/mTOR signaling pathway by pterostilbene attenuates mantle cell lymphoma progression.

Mantle cell lymphoma (MCL) is an aggressive and mostly incurable B-cell malignancy with frequent relapses after an initial response to standard chemotherapy. Therefore, novel therapies are urgently required to improve MCL clinical outcomes. In this study, MCL cell lines were treated with pterostilbene (PTE), a non-toxic natural phenolic compound primarily found in blueberries. The antitumor activity of PTE was examined by using the Cell Counting Kit-8, apoptosis assays, cell cycle analysis, JC-1 mitochondrial membrane potential assay, western blot analysis, and tumor xenograft models. PTE treatment induced a dose-dependent inhibition of cell proliferation, including the induction of cell apoptosis and cell cycle arrest at the G0/G1 phase. Moreover, the PI3K/Akt/mTOR pathway was downregulated after PTE treatment, which might account for the anti-MCL effects of PTE. Synergistic cytotoxicity was also observed, both in MCL cells and in xenograft mouse models, when PTE was administered in combination with bortezomib (BTZ). The antitumor effects of PTE shown in our study provide an innovative option for MCL patients with poor responses to standardized therapy. It is noteworthy that the treatment combining PTE with BTZ warrants clinical investigation, which may offer an alternative and effective MCL treatment in the future.

And finally, PDE4

Inhibiting PDE4 has some very useful anti-inflammatory benefits. It may also improve myelination and indeed cognition.  PDE4 inhibitors are currently used to treat severe asthma and in clinical trials for Multiple Sclerosis (MS) and cognitive enhancement.

There are different sub-types of PDE4.

Inhibiting one of the subtypes has the tendency to make you want to vomit.  This is currently the drawback that limits the use of PDE4 inhibiting drugs.

A selective PDE4 inhibitor is required.

As Ling has found, research does indeed show that pterostilbene is a PDE4 inhibitor.

The molecular basis for the inhibition of phosphodiesterase-4D by three natural resveratrol analogs. Isolation, molecular docking, molecular dynamics simulations, binding free energy, and bioassay.

The phosphodiesterase-4 (PDE4) enzyme is a promising therapeutic target for several diseases. Our previous studies found resveratrol and moracin M to be natural PDE4 inhibitors. In the present study, three natural resveratrol analogs [pterostilbene, (E)-2',3,5',5-tetrahydroxystilbene (THSB), and oxyresveratrol] are structurally related to resveratrol and moracin M, but their inhibition and mechanism against PDE4 are still unclear. A combined method consisting of molecular docking, molecular dynamics (MD) simulations, binding free energy, and bioassay was performed to better understand their inhibitory mechanism. The binding pattern of pterostilbene demonstrates that it involves hydrophobic/aromatic interactions with Phe340 and Phe372, and forms hydrogen bond(s) with His160 and Gln369 in the active site pocket. The present work also reveals that oxyresveratrol and THSB can bind to PDE4D and exhibits less negative predicted binding free energies than pterostilbene, which was qualitatively validated by bioassay (IC50=96.6, 36.1, and 27.0μM, respectively). Additionally, a linear correlation (R(2)=0.953) is achieved for five PDE4D/ligand complexes between the predicted binding free energies and the experimental counterparts approximately estimated from their IC50 values (≈RT ln IC50). Our results imply that hydrophobic/aromatic forces are the primary factors in explaining the mechanism of inhibition by the three products. Results of the study help to understand the inhibitory mechanism of the three natural products, and thus help the discovery of novel PDE4 inhibitors from resveratrol, moracin M, and other natural products.

Conclusion

Based on Ling’s recommendation, I have ordered some Pterostilbene and I am curious to see its effects. It is another substance that might be helpful for older adults, if not for your case of autism.

It is clear that in most cases resveratrol is a substance whose effect is limited to the test tube rather than humans. As a “super-resveratrol” we should take a closer look at Pterostilbene.

Eating large amounts of fruits, vegetables and berries with anthocyanins and betacyanins is going to do you no harm and does look a way to possibly secure a long healthy future, like those Japanese centenarians in Okinawa.

Amino Acids in Autism

Amino Acids (AAs) are very important to health and it is important that all 20 are within the reference ranges, or there can be serious consequences.  Inborn errors of amino acid metabolism do exist and there are metabolic disorders which impair either the synthesis and/or degradation of amino acids.

It has been suggested that a lack of certain amino acids might underlie some people’s autism. This seems to be the basis of one new autism drug, CM-AT, being developed in the US, but this idea remains somewhat controversial.

In those people who have normal levels of amino acids, potential does exist to modify their level for some therapeutic effect. 

Examples include:-

·        Using histidine to inhibit mast cells de-granulating and so reducing symptoms of allergy

·       Using the 3 branch chained AAs to reduce the level of the AA, phenylanine, which can drive movement disorders/tics

·       Methionine seems to promote speech in regressive autism, but for no known reason.

·        Some AAs, such as leucine, activate mTOR. It is suggested that others (histidine, lysine and threonine) can inhibit it, which might have a therapeutic benefit in those with too much mTOR signaling.

·        D-Serine, synthesized in the brain by from L-serine, serves as a neuromodulator by co-activating NMDA receptors.  D-serine has been suggested for the treatment of negative symptoms of schizophrenia

·        Aspartic acid is an NMDA agonist

·       Threonine is being studied as a possible therapy for Inflammatory Bowel Disease (IBD), because it may increase intestinal mucin synthesis.

Amino acids, the building blocks for proteins

To make a protein, a cell must put a chain of amino acids together in the right order. It makes a copy of the relevant DNA instruction in the cell nucleus, and takes it into the cytoplasm, where the cell decodes the instruction and makes many copies of the protein, which fold into shape as they are produced.

There are 20 standard or “canonical” amino acids, which can be thought of as protein building blocks.

Humans can produce 10 of the 20 amino acids; the others must be supplied in the food and are called “essential”. The human body does not store excess amino acids for later use, so these amino acids must be in your food every day.

The 10 amino acids that we can produce are alanine, asparagine, aspartic acid, cysteine, glutamic acid, glutamine, glycine, proline, serine and tyrosine. Tyrosine is produced from phenylalanine, so if the diet is deficient in phenylalanine, tyrosine will be required as well.

The essential amino acids (marked * below) are arginine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine.

The three so-called branched-chain amino acids (BCAAs) are leucine, isoleucine and valine

The so-called aromatic amino acids (AAAs) are histidine, phenylanine, tryptophan and tyrosine

When plasma levels of BCAAs increase, this reduces the absorption of aromatic AAs; so the level of tryptophan, tyrosine, and phenylalanine will fall and this directly affects the synthesis and release of serotonin and catecholamines.

Many sportsmen, and indeed soldiers, take BCAA supplements in an attempt to build stronger muscles, but within the brain this will cause a cascade of other effects.

In people with tardive dyskinesia, which is a quite common tic disorder found in schizophrenia and autism, taking phenylalanine may make their tics worse.  It seems that taking BCAA supplements may make their tics reduce, because reducing the level of phenylalanine will impact dopamine (a catecholamine). Most movement disorders ultimately relate to dopamine.

Tardive Dyskinesia Exacerbated after Ingestion of Phenylalanine by Schizophrenic Patients

In effect, BCAA supplements affect the synthesis and release of serotonin and catecholamines.  This might be good for you, or might be bad for you; it all depends where you started from.

   Alanine
   Arginine *
   Asparagine
   Aspartic acid
   Cysteine
   Glutamic acid
   Glutamine
   Glycine
   Histidine * Aromatic
   Isoleucine * BCAA
   Leucine * BCAA
   Lysine *
   Methionine *
   Phenylalanine *  Aromatic
   Proline
   Serine
   Threonine *
   Tryptophan * Aromatic
   Tyrosine  Aromatic
   Valine *  BCAA

Blood levels of the BCAAs are elevated in people with obesity and those with insulin resistance, suggesting the possibility that BCAAs contribute to the pathogenesis of obesity and diabetes.  BCAA-restricted diets improve glucose tolerance and promote leanness in mice.

BRANCHED-CHAIN AMINO ACIDS AND THE BRAIN

In the brain, BCAAs have two important influences on the production of neurotransmitters. As nitrogen donors, they contribute to the synthesis of excitatory glutamate and inhibitory gamma-aminobutyric acid (GABA) They also compete for transport across the blood-brain barrier (BBB) with tryptophan (the precursor to serotonin), as well as tyrosine and phenylalanine (precursors for catecholamines)Ingestion of BCAAs therefore causes rapid elevation of the plasma concentrations and increases uptake of BCAAs to the brain, but diminishes tryptophan, tyrosine, and phenylalanine uptake. The decrease in these aromatic amino acids directly affects the synthesis and release of serotonin and catecholamines. The reader is referred to Fernstrom (2005) for a review of the biochemistry of BCAA transportation to the brain. Oral BCAAs have been examined as treatment for neurological diseases such as mania, motor malfunction, amyotrophic lateral sclerosis, and spinocerebral degeneration. Excitotoxicity as a result of excessive stimulation by neurotransmitters such as glutamate results in cellular damage after traumatic brain injury (TBI). However, because BCAAs also contribute to the synthesis of inhibitory neurotransmitters, it is unclear to what extent the role of BCAAs in synthesis of both excitatory and inhibitory neurotransmitters might contribute to their potential effects in outcomes of TBI.

A list of human studies (years 1990 and beyond) evaluating the effectiveness of BCAAs in providing resilience or treating TBI or related diseases or conditions (i.e., subarachnoid hemorrhage, intracranial aneurysm, stroke, anoxic or hypoxic ischemia, epilepsy) in the acute phase is presented in Table 8-1; this also includes supporting evidence from animal models of TBI. The occurrence or absence of adverse effects in humans is included if reported by the authors.

Cell Signaling

Leucine indirectly activates p70 S6 kinase as well as stimulates assembly of the eIF4F complex, which are essential for mRNA binding in translational initiation. P70 S6 kinase is part of the mammalian target of rapamycin complex (mTOR) signaling pathway.

The actions of exogenous leucine on mTOR signalling and amino acid transporters in human myotubes

The present study provides the first evidence that mTOR signalling is enhanced in response to an acute stimulation with the proteinogenic amino acid, leucine, within cultured human myotubes. While these actions appear transient at the leucine dose utilised, activation of mTOR and p70S6K occurred at physiologically relevant concentrations independently of insulin stimulation. Interestingly, activation of mTOR signalling by leucine occurred in the absence of changes in the expression of genes encoding both the system A and system L carriers, which are responsible for amino acid transport. Thus, additional analyses are required to investigate the molecular mechanisms controlling amino acid transporter expression within skeletal muscle. Of note was the increased protein expression of hVps34, a putative leucine-sensitive kinase which intersects with mTOR. These results demonstrate the need for further clinical analysis to be performed specifically investigating the role of hVps34 as a nutrient sensing protein for mTOR signalling.

Dexamethasone and BCAA Failed to Modulate Muscle Mass and mTOR Signaling in GH-Deficient Rats

Skeletal muscle mass is determined by the balance between the synthesis and degradation of muscle proteins. Several hormones and nutrients, such as branched-chain amino acids (BCAAs), stimulate protein synthesis via the activation of the mammalian target of rapamycin (mTOR).

BCAAs (i.e., leucine, isoleucine, and valine) also exert a protective effect against muscle atrophy. We have previously reported that orally administered BCAA increases the muscle weight and cross-sectional area (CSA) of the muscle in rats

Metabolic and Physiological Roles of Branched-Chain Amino Acids

3.4. BCAAs in Brain Functions

BCAAs may also play important roles in brain function. BCAAs may influence brain protein synthesis and production of energy and may influence synthesis of different neurotransmitters, that is, serotonin, dopamine, norepinephrine, and so forth, directly or indirectly. Major portion of dietary BCAAs is not metabolized by liver and comes into systemic circulation after a meal. BCAAs and aromatic AA, such as tryptophan (Trp), tyrosine (Tyr), and phenylalanine (Phe), share the same transporter protein to transport into brain. Trp is the precursor of neurotransmitter serotonin; Tyr and Phe are precursors of catecholamines (dopamine, norepinephrine, and epinephrine). When plasma concentration of BCAAs increases, the brain absorption of BCAAs also increases with subsequent reduction of aromatic AA absorption. That may lead to decrease in synthesis of these related neurotransmitters [3]. Catecholamines are important in lowering blood pressure. When hypertensive rats were injected with Tyr, their blood pressure dropped markedly and injection with equimolar amount of valine blocks that action [49]. In vigorous working persons, such as in athletes, depletion of muscle and plasma BCAAs is normal. And that depletion of muscle and plasma BCAAs may lead to increase in Trp uptake by brain and release of serotonin. Serotonin on the other hand leads to central fatigue. So, supplementation of BCAAs to vigorously working person may be beneficial for their performance and body maintenance

Example of a treatable Amino Acid variant of Autism

Mutations in BCKD-kinase lead to a potentially treatable form of autism with epilepsy.

Autism Spectrum Disorders (ASD) are a genetically heterogeneous constellation of syndromes characterized by impairments in reciprocal social interaction. Available somatic treatments have limited efficacy. We have identified inactivating mutations in the gene BCKDK (Branched Chain Ketoacid Dehydrogenase Kinase) in consanguineous families with autism, epilepsy and intellectual disability (ID). The encoded protein is responsible for phosphorylation-mediated inactivation of the E1-alpha subunit of branched chain ketoacid dehydrogenase (BCKDH). Patients with homozygous BCKDK mutations display reductions in BCKDK mRNA and protein, E1-alpha phosphorylation and plasma branched chain amino acids (BCAAs). Bckdk knockout mice show abnormal brain amino acid profiles and neurobehavioral deficits that respond to dietary supplementation. Thus, autism presenting with intellectual disability and epilepsy caused by BCKDK mutations represents a potentially treatable syndrome.

The data suggest that the neurological phenotype may be treated by dietary supplementation with BCAAs. To test this hypothesis, we studied the effect of a chow diet containing 2% BCAAs or a BCAA-enriched diet, consisting of 7% BCAAs, on the neurological phenotypes of the Bckdk^−/− mice. Mice raised on the BCAA-enriched diet were phenotypically normal. On the 2% BCAA diet, however, Bckdk^−/− mice had clear neurological abnormalities not seen in wild-type mice, such as seizures and hindlimb clasping, that appeared within 4 days of instituting the 2% BCAA diet (Fig. 3B). These neurological deficits were completely abolished within a week of the Bckdk^−/− mice starting the BCAA-enriched diet, which suggests that they have an inducible yet reversible phenotype (Fig. 3C).

Our experiments have identified a Mendelian form of autism with comorbid ID and epilepsy that is associated with low plasma BCAAs. Although the incidence of this disease among patients with autism and epilepsy remains to be determined, it is probably quite a rare cause of this condition. We have shown that murine Bckdk^−/− brain has a disrupted amino acid profile, suggesting a role for the BBB in the pathophysiology of this disorder. The mechanism by which abnormal brain amino acid levels lead to autism, ID, and epilepsy remains to be investigated. We have shown that dietary supplementation with BCAAs reverses some of the neurological phenotypes in mice. Finally, by supplementing the diet of human cases with BCAAs, we have been able to normalize their plasma BCAA levels (table S10), which suggests that it may be possible to treat patients with mutations in BCKDK with BCAA supplementation.

(Look at the three red rows, the BCAAs, all lower than the reference range, before supplementation)

Threonine, Mucin and Akkermansia muciniphila in Autism

Mucins are secreted as principal components of mucus by mucous membranes, like the lining of the intestines.  People with Inflammatory Bowel Disease (IBD) have mucus barrier changes.

The low levels of the mucolytic bacterium Akkermansia muciniphila found in children with autism, apparently suggests mucus barrier changes.

The amino acid Threonine is a component of mucin and Nestle have been researching for some time the idea of a threonine supplement to treat Inflammatory Bowel Disease (IBD), being a serious Swiss company they publish their research.      

Threonine Requirement in IBD Adults and Healthy Adult Controls

Threonine Requirement in Healthy Adult Subjects and in Patients With Crohn's Disease and With Ulcerative Colitis Using the Indicator Amino Acid Oxidation (IAAO) Methodology

Threonine is an essential amino acid which must be obtained from the diet. It is a component of mucin. Mucin, in turn, is a key protein in the mucous membrane that protects the lining of the intestine.

Inflammatory bowel disease (IBD) is a group of inflammatory conditions that affect the colon and small intestine. IBD primarily includes ulcerative colitis (UC) and Crohn's disease (CD). In UC, the inflammation is usually in the colon whereas in CD inflammation may occur anywhere along the digestive tract. Studies in animals have shown that more threonine is used when there is inflammation in the intestine.

The threonine requirement in healthy participants and in IBD patients will be determined using the indicator amino acid oxidation method. The requirement derived in healthy participants will be compared to that derived in patients with IBD.

Each participant will take part in two x 3 day study periods. The first two days are called adaptation days where the subjects will consume a liquid diet specially designed for him. The diet will be consumed at home. It contains all vitamins, minerals, protein and all other nutrients required. On the third day, the participant will come to the Hospital for Sick Children in Toronto. Subjects will consume hourly meals for a total of 8 meals and a stable isotope 13C-phenylalanine. Breath and urine samples will be collected to measure the oxidation of phenylalanine from which the threonine requirement will be determined. 

Dietary Threonine Restriction Specifically Reduces Intestinal Mucin Synthesis in Rats

We determined whether the steady-state levels of intestinal mucins are more sensitive than total proteins to dietary threonine intake. For 14 d, male Sprague-Dawley rats (158 ± 1 g, n = 32) were fed isonitrogenous diets (12.5% protein) containing 30% (group 30), 60% (group 60), 100% (control group), or 150% (group 150) of the theoretical threonine requirement for growth. All groups were pair-fed to the mean intake of group 30. The mucin and mucosal protein fractional synthesis rates (FSR) did not differ from controls in group 60. By contrast, the mucin FSR was significantly lower in the duodenum, ileum, and colon of group 30 compared with group 100, whereas the corresponding mucosal protein FSR did not differ. Because mucin mRNA levels did not differ between these 2 groups, mucin production in group 30 likely was impaired at the translational level. Our results clearly indicate that restriction of dietary threonine significantly and specifically impairs intestinal mucin synthesis. In clinical situations associated with increased threonine utilization, threonine availability may limit intestinal mucin synthesis and consequently reduce gut barrier function.

  

Mucin glycan foragingin the human gut microbiome

It has been proposed that excessive mucin degradation by intestinal bacteria may contribute to intestinal disorders, as access of luminal antigens to the intestinal immune system is facilitated. However, it is not known whether all mucin-degraders have the same effect. For example A. muciniphila may possess anti-inflammatory properties, as a high proportion of the bacteria has been correlated to protection against inflammation in diseases such as type 1 diabetes mellitus, IBD, atopic dermatitis, autism , type 2 diabetes mellitus, and.

Low Relative Abundances of the Mucolytic Bacterium Akkermansia muciniphila and Bifidobacteriumspp. in Feces of Children with Autism

Gastrointestinal disturbance is frequently reported for individuals with autism. We used quantitative real-time PCR analysis to quantify fecal bacteria that could influence gastrointestinal health in children with and without autism. Lower relative abundances of Bifidobacteria species and the mucolytic bacterium Akkermansia muciniphila were found in children with autism, the latter suggesting mucus barrier changes. 

Previous studies in rats by MacFabe et al. have shown that intraventricular administration of propionate induces behaviors resembling autism (e.g., repetitive dystonic behaviors, retropulsion, seizures, and social avoidance) (12, 13). We have also reported increased fecal propionate concentrations in ASD children compared with that in controls in the same fecal samples (25). However, the abundance of a key propionate-producing bacterium, Prevotella sp., was not significantly different between the study groups. This suggests that other untargeted bacteria, such as those from Clostridium cluster IX, which also includes major propionate producers (24), may be responsible for the observed differences in fecal propionate concentrations. Moreover, it is possible that the activities of the bacteria responsible for producing propionate, rather than bacterial numbers, have been altered. Other factors, such as differences in GI function that change GI transit time in ASD children, should also be considered.

In summary, the current findings of depleted populations of A. muciniphila and Bifidobacterium spp. add to our knowledge of the changes in the GI tracts of ASD children. These findings could potentially guide implementation of dietary/probiotic interventions that impact the gut microbiota and improve GI health in individuals with ASD.

Conclusion

I think that modifying levels of amino acids can have merit for some people, but it looks like another case for personalized medicine, rather than the same mix of powders given to everyone.

Threonine is interesting given the incidence of Inflammatory Bowel Disease (IBD) in autism.  IBD mainly describes ulcerative colitis and Crohn's disease.

The research into Threonine, is being funded by Nestle, the giant Swiss food company, who fortunately do publish their research.

The trial in the US of CM-AT is unusual because no results have ever been published in the literature, so we just have press releases. It likely that CM-AT is a mixture of pancreatic enzymes from pigs and perhaps some added amino acids.

http://www.prweb.com/releases/2017/02/prweb14088362.htm

This 14-week, double-blind, randomized, placebo-controlled Phase 3 study is being conducted to determine if CM-AT may help improve core and non-core symptoms of Autism. CM-AT, which has been granted Fast Track designation by FDA, is designed to enhance protein digestion thereby potentially restoring the pool of essential amino acids. Essential amino acids play a critical role in the expression of several genes important to neurological function and serve as precursors to key neurotransmitters such as serotonin and dopamine.

Based on the study I referred to early this year:-

Dietary interventions that reduce mTOR activity rescue autistic-like behavioral deficits in mice 

·        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.

in my post:

Histidine for Allergy, but as an effective MTOR inhibitor?

I for one will be evaluating both lysine and threonine, having already found a modest dose histidine very beneficial in allergy (stabilizing mast cells).

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. 

Dietary interventions that reduce mTOR activity rescue autistic-like behavioral deficits in mice

          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.

Source: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4159743/figure/F1/

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. 

Everolimus improves neuropsychiatric symptoms in a patient with tuberous sclerosis carrying a novel TSC2 mutation

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.

The role of amino acid-induced mammalian target of rapamycin complex 1(mTORC1) signaling ininsulin resistance

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?

Study of plasma amino acid levels in children with autism: An Egyptian sample

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.