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Showing posts with label DAO. Show all posts
Showing posts with label DAO. Show all posts

Monday 5 March 2018

Autism and Non-Antibiotic Properties of Common Beta-lactam Antibiotics


If you are looking for personalized medicine, you or your doctor need to be a good detective. Not to mention you need some clues.
If you are treating a condition like autism and certain things cause a marked change in the severity of the condition, these are pretty good places to start.
In the case of our reader in Delhi, it is Beta-lactam antibiotics (penicillin, amoxicillin etc), that consistently seem to improve her son’s autism. Improvement during treatment with antibiotics is reported quite often in autism, but with all kinds of different antibiotic.  Nothing is simple.
For non-medical readers, there are several categories of antibiotics; common types including:-
·        Beta-lactams (e.g. Penicillins)

·        Macrolides (e.g. Erythromycin, Azithromycin)

·        Fluoroquinolones (e.g. Ciprofloxacin) 

·        Tetracyclines (e.g. Minocycline) 

Macrolides have already had a dedicated post about their immunomodulatory effects, which did also cover some history about Poland from Monty's homework.

Macrolide Antibiotics for Some Autism? Or better still, Azithromycin analogue CSY0073, or just Nystatin?



Beta Lactam Antibiotics
In earlier posts we came across something called glutamate transporter GLT1 (also known as EAAT2).
Glutamate is the major excitatory neurotransmitter, and is inactivated by uptake via GLT-1 (EAAT2) and GLAST (EAAT1) transporters.
Many people given the observational diagnosis of autism appear to have an underlying imbalance between excitatory and inhibitory neurotransmitters (E/I imbalance). By correcting the specific type of E/I imbalance, even profound symptoms of autism including MR/ID and epilepsy can be moderated. If you have autism and/or epilepsy tuning your E/I imbalance is likely the most important step you can take.
Some drugs increase the expression of GLT-1 and so reduce the amount of glutamate. Macrolide antibiotics are one of these drugs.
So if a person has too much glutamate and this causes/contributes to their E/I imbalance then improved behaviour while taking penicillin antibiotics, who have a simple explanation.
Since you would not want to take penicillin forever you would then look for a non antibiotic drug that also increases the uptake of Glutamate. Once such drug, Riluzole, does exist and has already been trialed on children with OCD. 
But beta-lactams have other effects, so it is not certain that GLT-1 accounts for the beneficial effect sometimes found in autism. Fortunately some researchers have assembled most previous research into a single review paper. This paper does not mention autism and does miss some things out.


There are seven categories:-
·        Antibiotic

·        Epileptogenic

·        Neuroprotective

·        Analgesic

·        Immunomodulatory

·        Anxiolytic

·        Antineoplastic



Antibiotic Effect
We all know something about bacteria. If you have a bacterial infection like an ear infection your doctor might prescribe you an antibiotic.

As well as inflaming your ear, the bacteria may well affect gene expression. We saw in a previous post that bacteria and viruses change the expression of many genes, but the study of this is in its infancy. In autism we know that many genes are miss-expressed, but this varies from person to person. So a bacteria or virus has the potential to make autism worse (e.g. PANS and PANDAS), but also better. Bacteria are not always bad.
A person whose autism responds to an antibiotic might have bacteria that are worsening his autism. This is simplest of explanation of all.

The question then is where is the bacteria? If it is an intestinal bacterium this could be proven by using an antibiotic that only works there, like Vancomycin.

Epileptogenic effects
In this review they concluded the effects relate to GABA and here we are talking about negative effects. 

penicillin is a potent epileptogenic agent = it is capable of causing an epileptic attack

“This could mean that penicillin is a competitive GABA specific antagonist, which would further explain its epileptogenic properties.”

The paper omits to point out that in some people beta-lactams protect from epileptic seizures. The effect on Glutamate is likely at least sometimes what stops seizures.


The really clever thing in the above case report is that appears that the effect on glutamate may be by an epigenetic mechanism (via GLT1), since the effect is long lasting. Read later in this post about the epigenetic effects of beta-lactams.

Neuroprotective properties
“These results suggest that the neuroprotective effect induced by beta-lactam antibiotics is due to their capacity to stimulate GLT1 expression and thus regulate the concentration of glutamate in the synaptic cleft. GLT1 is a glutamate transporter inducing its reuptake by astrocytes preventing excessive glutamate concentration in the synaptic cleft
It was subsequently shown that the neuroprotective effect of BLMs was due not only to glutamate down regulation, but also to a diminished glutamate-induced intracellular Ca2+ concentration and an increased uptake of glutamate
Another probable mechanism of neuroprotection induced by BLMs is down-regulation of oxidative stress and modulation of apoptotic pathways shown in rat spinal cord when CFX was administered for 7 days prior to induction of constrictive neuropathy. This effect was apparently mediated by both a reduction in proapoptotic proteins Bax, and an increment in the antiapoptotic protein Bcl2.
CFX (Ceftiaxone) may induce neuroprotection by other mechanisms besides GLT1 overexpression. Yamada and Jinno [51] reported that the antibiotic reversed axotomy-induced up regulation of GFAP, a neuronal damage marker, and increased neuronal survival; apparently not only through glutamatergic regulation, but also by direct reduction of glial hypereactivity. Supplementary to this is the finding of an attenuation of microglial activation induced IL-1 expression in an ischemic injury model when CFX was administered as a pre-treatment [52]. This result may indicate a direct action on glial cells since partial reduction of astrocytes and microglia was observed.”

Analgesic (pain killing) Properties
“Interestingly, despite the widespread clinical use of BLMs (beta-lactams), some of their known non-antibiotic effects have been either disregarded or misinterpreted as resulting from bacterial microbiome regulation. For example, Caperton, Heim-Duthoy [54] hypothesized that chronic inflammatory arthritis could have a bacterial component and that therefore the clinical course of a patient could be affected by administration of CFX (Ceftriaxone).
Both the anti-inflammatory and neuromodulating effects exerted by BLMs either peripherally or centrally may be related to their analgesic properties in some pathologies that are difficult to treat such as the complex regional pain syndrome [65] or to the analgesic effect of a single preoperative dose of CFX in a clinical protocol [66].

Immunomodulatory Properties 
Not many people seem to have read this paper. They did not flesh out immunomodulation, so I draw on a different paper. People who write about immunomodulation usually say that beta-lactams do not have this effect, but that appears to be incorrect. 

Recent work has suggested that beta-lactam antibiotics might directly affect eukaryotic cellular functions. Here, we studied the effects of commonly used beta-lactam antibiotics on rodent and human T cells in vitro and in vivo on T-cell–mediated experimental autoimmune diseases. We now report that experimental autoimmune encephalomyelitis and adjuvant arthritis were significantly more severe in rats treated with cefuroxime and other beta-lactams. T cells appeared to mediate the effect: an anti-myelin basic protein T-cell line treated with cefuroxime or penicillin was more encephalitogenic in adoptive transfer experiments. The beta-lactam ampicillin, in contrast to cefuroxime and penicillin, did not enhance encephalomyelitis, but did inhibit the autoimmune diabetes developing spontaneously in non-obese diabetic mice. Gene expression analysis of human peripheral blood T cells showed that numerous genes associated with T helper 2 (Th2) and T regulatory (Treg) differentiation were down-regulated in T cells stimulated in the presence of cefuroxime; these genes were up-regulated in the presence of ampicillin. The T-cell protein that covalently bound beta-lactam antibiotics was found to be albumin. Human and rodent T cells expressed albumin mRNA and protein, and penicillin-modified albumin was taken up by rat T cells, leading to enhanced encephalitogenicity. Thus, beta-lactam antibiotics in wide clinical use have marked effects on T-cell behavior; beta-lactam antibiotics can function as immunomodulators, apparently through covalent binding to albumin.

 Anxiolytic effects (reduce anxiety)
“CA (Clavulanic acid) has proven effective as an anxiolytic drug, since it was reported that this drug diminished anxiety-like conduct in both rodent and primate models”

Antineoplastic effects (preventing tumors)
“CFX (Ceftriaxone) elicit antitumor activity both in vitro and in vivo models”

Addiction
Addiction did not appear in the chart above, but it gets a mention in the text 
“When tested in an opiate dependence model, both CFX [72] and CA [73] inhibited both physical dependence and withdrawal symptoms. This could mean that the effect shown by CFX is not due to its particular molecular structure, but can be reproduced by other BLMs (several BLMs effects shown on Fig. 3)

Other effects
“CA (Clavulanic acid) has been shown to increase dopamine release”

Epigenetic Effects
These were not mentioned in the paper, but I do think epigenetics is a fundamental part of many diseases, including much autism.
The paper really explains why short term use of beta-lactams can stop a person with epilepsy having seizures for a long time.

Off-Target drug effects resulting in altered gene expression events with epigenetic and"Quasi-Epigenetic" origins.


This review synthesizes examples of pharmacological agents who have off-target effects of an epigenetic nature. We expand upon the paradigm of epigenetics to include "quasi-epigenetic" mechanisms. Quasi-epigenetics includes mechanisms of drugs acting upstream of epigenetic machinery or may themselves impact transcription factor regulation on a more global scale. We explore these avenues with four examples of conventional pharmaceuticals and their unintended, but not necessarily adverse, biological effects. The quasi-epigenetic drugs identified in this review include the use of beta-lactam antibiotics to alter glutamate receptor activity and the action of cyclosporine on multiple transcription factors. In addition, we report on more canonical epigenome changes associated with pharmacological agents such as lithium impacting autophagy of aberrant proteins, and opioid drugs whose chronic use increases the expression of genes associated with addictive phenotypes. By expanding our appreciation of transcriptomic regulation and the effects these drugs have on the epigenome, it is possible to enhance therapeutic applications by exploiting off-target effects and even repurposing established pharmaceuticals. That is, exploration of "pharmacoepigenetic" mechanisms can expand the breadth of the useful activity of a drug beyond the traditional drug targets such as receptors and enzymes.








DAO inhibition
As our reader Agnieszka pointed out in the comments section, one commonly prescribed beta-lactam antibiotic called Augmentin contains a second antibiotic, Clavulanic acid, to boost its effectiveness; by chance is also a very potent DAO inhibitor. Diamine oxidase (DAO), also known as histaminase, is an enzyme in your body that is used to inactivate histamine. Histamine is found in food that you eat as well as being produced in your body and released by your mast cells during an allergic reaction.

DAO neutralizes the histamine in food so it does not enter your bloodstream.
So this particular antibiotic should be avoided by those people who are histamine intolerant and so do not produce enough DAO. This is about 1% of the general population, but might be more common in those with autism although there is no data on this subject.

Some people believe that ADHD is associated with a reduced level of DAO.
Indeed there is a patent to treat ADHD with a combination of DAO and caffeine.



[0087] DAO can also be mixed with caffeine, strengthening the role of prevention and treatment of attention deficit hyperactivity disorder. Thus, also disclosed herein compositions comprising DAO and caffeine. 
[0088] Caffeine, a xanthine alkaloid group having stimulating properties for the treatment of attention deficit hyperactivity disorder. 
[0089] DAO content of the present invention per unit dose 0 · l-50mg, preferably 2-20mg. 
[0090] The present invention is caffeine content per unit dose 1-lOOmg, preferably 5-50mg. 
[0091] for the prevention and treatment of attention deficit hyperactivity disorder DAO or compositions comprising DAO may be before a meal or postprandial meal administration.
[0092] The use of DAO of the invention or compositions comprising DAO directly affect blood histamine levels, thus affecting the symptoms of attention deficit cumulative histamine levels induced hyperactivity disorder.

You can actually buy DAO supplements and of course caffeine.
Perhaps people consuming DAO inhibitors long term, such as NAC and Verapamil, and have chronic allergies or mast cell disorders might benefit from extra DAO. 




Most DAO is actually in your digestive tract, where the dietary histamine is.

You can measure DAO levels in your blood.

We can conclude that determination of DAO activity in serum is a useful diagnostic tool, together with detailed history to differentiate between food allergy and histamine intolerance.
We found that DAO activity was significantly lower in patients than in healthy control subjects.

Conclusion
I think there is plenty of food for thought here for parents of children whose autism and/or epilepsy improves when taking a beta-lactam antibiotic.  Hopefully some people will figure out which effect is the beneficial one and find something else to replicate it.

There is a lot previously written in this blog about upregulating GLT1, other than by a beta-lactam. My favoured option was Riluzole, but Bromocriptine will also do this, among its other actions. Riluzole is a drug for ALS, that has been trialed in children with OCD, without side effects.    

People technically without histamine intolerance (normal levels of DAO) who incidentally take large amounts of DAO inhibitors, may end up exacerbating an existing mast cell related problem. One potential solution for that small group might be taking an OTC DAO supplement.







Tuesday 3 February 2015

Autism & Schizophrenia - Histamine degradation via HMT (requiring SAMe) and via DAO

Today’s post is a little complicated because it links together various issues ranging from food allergies to severe headaches, brain inflammation to arthritis.

The common link here is histamine, which has been covered at length on this blog.  You may recall that the H1 histamine receptor is the one associated with hay fever, H2 is expressed in the intestines and is involved in regulating acidity levels, H3 is mainly found in the central nervous system (CNS).

The Histamine H4 receptor has been shown to be involved in mediating eosinophil shape change and mast cell chemotaxis.

Here is the full paper, for those interested in mast cells:-


In addition to all these receptors, histamine causes an increase in the pro-inflammatory cytokine IL-6.  IL-6 is elevated in autism and many other inflammatory conditions ranging from arthritis to traumatic brain injury (TBI). 

One of interesting interventions in this post is SAMe (S-Adenosyl methionine )and its precursor L-methionine.  We will see why a deficit of SAMe causes a problem when the body tries to degrade/deactivate histamine.

We will also see in a later post that the level of SAMe in the body modulates the release anti-inflammatory cytokines like IL-10 and IL-35.  Here is one link, for now.


5. Higher expression of IL-35 could be induced by higher hypomethylation status in tissues

Previous reports showed that epigenetic mechanisms, including methylation and demethylation, control T helper cell differentiation and cytokine generation [41]. As we discussed in our recent review [42], the ratio of cellular methylation donor S-adenosylmethionine (SAM) levels over S-adenosylhomocysteine (SAH) levels is an important metabolic indicator of cellular methylation status [43], [44]. A higher SAM/SAH ratio suggests a higher methylation status than normal (hypermethylation) whereas a lower SAM/SAH ratio indicates a lower methylation status than normal (hypomethylation).  A previous report showed that feeding rats with SAM, a methyl donor, inhibits the expression of TGF-βR1 and TGF-βR2 [45], suggesting that intracellular global methylation status regulates anti-inflammatory cytokine signaling.  … Cont/


Interestingly, I found that for decades SAMe  has been a mainstream drug therapy used in Italy to treat arthritis.
    

Histamine degradation

In mammals, histamine is metabolized by two major pathways: N(tau)-methylation via histamine N-methyltransferase (HMT) and oxidative deamination via diamine oxidase (DAO).

HMT and uses S-adenosyl-L-methionine (SAMe) as the methyl donor.  If SAMe is lacking HMT cannot degrade histamine.

In the brain, the neurotransmitter activity of histamine is controlled by N(tau)-methylation.  It is disputed whether diamine oxidase is found in the central nervous system.  Some sources say it is not, but other studies specifically measure DAO levels in the brain, finding them elevated in schizophrenia.

A common genetic polymorphism affects the activity levels of HMT in red blood cells.  This can be tested for.

People with low levels of DAO will not be able to degrade histamine in their body nor, it appears to me, in the brain.

People with low levels of SAMe will not be able to degrade histamine as they should, that has crossed the BBB (blood brain barrier).  Those same low levels of SAMe will have raised the inflammatory cytokines and reduced the anti-inflammatory cytokines.


Methionine metabolism


I am always very wary when I see charts like the one below.  Often they are used to justify all kinds of strange ideas.  So the following methionine description is just a cut and paste from Wikipedia.

If anything goes wrong in this metabolism, you might indeed expect strange things to happen.  The ratio of SAMe/SAH is measurable  and tends to be markedly low in people with ASD.  This why DAN doctors use vitamin B12 injections, other B vitamins and other exotic sounding “supplements”.

Metabolic biomarkers of increased oxidative stress and impairedmethylation capacity in children with autism




Methionine is an essential amino acid that must be provided by dietary intake of proteins or methyl donors (choline and betaine found in beef, eggs and some vegetables). Assimilated methionine is transformed in S-adenosyl methionine (SAM) which is a key metabolite for polyamine synthesis, e.g. spermidine, and cysteine formation (see the figure on the right). Methionine breakdown products are also recycled back into methionine by homocysteine remethylation and methylthioadenosine (MTA) conversion (see the figure on the right). Vitamins B6, B12, folic acid and choline are essential cofactors for these reactions. SAM is the substrate for methylation reactions catalyzed by DNA, RNA and protein methyltransferases.

The products of these reactions are methylated DNA, RNA or proteins and S-adenosylhomocysteine (SAH). SAH has a negative feedback on its own production as an inhibitor of methyltransferase enzymes. Therefore SAM:SAH ratio directly regulates cellular methylation, whereas levels of vitamins B6, B12, folic acid and choline regulates indirectly the methylation state via the methionine metabolism cycle.[44][45] A near ubiquitous feature of cancer is a maladaption of the methionine metabolic pathway in response to genetic or environmental conditions resulting in depletion of SAM and/or SAM-dependent methylation. Whether it is deficiency in enzymes such as methylthioadenosine phosphorylase, methionine-dependency of cancer cells, high levels of polyamine synthesis in cancer, or induction of cancer through a diet deprived of extrinsic methyl donors or enhanced in methylation inhibitors, tumor formation is strongly correlated with a decrease in levels of SAM in mice, rats and humans.[46][47]







Low levels of SAMe do seem to cause problems in some people and it is straightforward to increase it.  You can either give extra SAMe, which is expensive, or L-methionine, which is cheap.

Interestingly, L-methionine is used at Johns Hopkins to treat autism and apparently is particularly effective at increasing speech.

If L-methionine was effective it could be for reasons including:-

·        cellular methylation was dysfunction
·        histamine in the brain had been elevated
·        the level of pro/anti-inflammatory cytokines had been out of balance 

Here are some examples of the use of SAMe (methionine)




In its native form, SAMe is labile and degrades rapidly. However, several patents for stable salts of SAMe have been granted. Among them, toluenedisulfonate and 1,4-butanedisulfonate forms have been chosen for pharmaceutical development, and as a result, preclinical and clinical studies have been performed. Numerous studies over the past 2 decades have shown that SAMe is effective in the treatment of depression (46), osteoarthritis (78), and liver disease (911). Moreover, SAMe has a very favorable side-effect profile, comparable with that of placebos. Thus, SAMe offers considerable advantages as an alternative to standard medications.

Depression
Clinical studies performed as early as 1973 indicated that SAMe had antidepressant effects (38). Over the next 2 decades, the efficacy of SAMe in treating depressive disorders was confirmed in > 40 clinical trials. Several review articles that summarize these studies were published in 1988 (4), 1989 (5), 1994 (6), and 2000 (12). In a meta-analysis, Bressa (6) reviewed 25 controlled trials including a total of 791 patients. The outcome of this analysis showed that SAMe had a significantly greater response rate than did placebo and was comparable to tricyclic antidepressants. Brown et al (12) summarized the literature on the use of SAMe in depressive disorders up to the time of publication in 2000; they reported that SAMe had been studied in 16 open, uncontrolled trials (660 patients); 13 randomized, double-blind, placebo-controlled trials (537 patients); and 19 controlled trials comparing SAMe with other antidepressants (1134 patients). Significant antidepressant effects were observed in all 16 open trials. In 18 controlled trials, SAMe was as effective as was impramine, chlorimipramine, nomifensine, and minaprine. An important observation from these studies is that SAMe had far fewer side effects than did standard medications.
Neurologic disorders
Several studies indicate that a CNS methyl group deficiency may play a role in the etiology of Alzheimer disease (AD). Reduced SAMe concentrations were found in CSF (34) and in several different brain regions (51) of patients with AD. In addition, reduced phosphatidylcholine concentrations were found in postmortem brain tissue from AD patients (52), and significant changes in brain phospholipids that are dependent on SAMe metabolism were detected in vivo with 31p magnetic resonance spectroscopy in the early stages of AD (53). Deficiencies of folate and vitamin B-12 are common in the elderly (39, 40) and can lead to decreased CNS SAMe concentrations. Several studies indicate that elevated blood homocysteine concentrations, considered to be a marker for folate deficiency, vitamin B-12 deficiency, and impaired methylation, may be a risk factor for AD (5456). It is therefore important to note that preliminary studies using either SAMe (57) or alternative methyl group donors [such as betaine (58) or folate and vitamin B-12 (59, 60)] can improve measures of cognitive function. These treatments may be able to restore methyl group metabolism and normalize blood homocysteine concentrations. Reduced SAMe concentrations in CSF were also reported in patients with subacute combined degeneration of the spinal cord resulting from folate or vitamin B-12 deficiency (39) and in children with inborn errors of the methyl-transfer pathway who had demyelination (61). In these cases, treatment with methyl-group donors such as SAMe, methyltetrahydrofolate, betaine, and methionine was associated with remyelination and a clinical response (61).

Lancet. 1991 Dec 21-28;338(8782-8783):1550-4.

Association of demyelination with deficiency of cerebrospinal-fluid S-adenosylmethionine in inborn errors of methyl-transfer pathway.

We have shown that demyelination is associated with cerebrospinal-fluid S-adenosylmethionine deficiency and that restoration of S-adenosylmethionine is associated with remyelination.


Remyelination is also interesting.  Damage to the critical myelin layer has been suggested to occur with mitochondrial disease.  Most young people with autism show signs of mitochondrial disease (based on post mortem samples) but not old people with autism.

Demyelination is the loss of the myelin sheath insulating the nerves, and is the hallmark of some neurodegenerative autoimmune diseases, including multiple sclerosis.


Liver disease
The potential benefit of SAMe in treating liver disease stems from several important aspects of SAMe metabolism. In mammals, as much as 80% of the methionine in the liver is converted into SAMe (23). Hepatic glutathione, which is dependent on methionine and SAMe metabolism, is one of the principal antioxidants involved in hepatic detoxification. Studies have shown that abnormal SAMe synthesis is associated with chronic liver disease, regardless of its etiology. Early studies indicated that patients with liver disease are unable to metabolize methionine, resulting in elevated blood concentrations (67). Subsequent studies in patients with liver disease showed that the defect resulted from decreased activity of a liver-specific isoenzyme, MAT I/III; this defect effectively blocks the conversion of methionine to SAMe (68). Several well-designed experimental studies indicated that MAT I/III is regulated by cellular concentrations of both nitric oxide and glutathione. Thus, increased nitric oxide concentrations and decreased glutathione concentrations were shown to inhibit MAT I/III via mechanisms involving increased S-nitrosylation and free radical damage to the enzyme protein (69, 70). Experimental studies and clinical trials showed that parenteral and oral SAMe administration can increase glutathione concentrations in red blood cells (71) and in hepatic tissue (72, 73) and can effectively replenish depleted glutathione pools in patients with liver disease. The literature on the clinical potential of SAMe in the treatment of liver disease (including cholestasis, hepatitis, and cirrhosis) has been the subject of several review articles (911, 74, 75).
  
Osteoarthritis
The potential benefit of SAMe in treating osteoarthritis was discovered when patients enrolled in clinical trials of SAMe for depression reported marked improvement in their osteoarthritis symptoms (76). Nine clinical trials in Europe (77) and 1 in the United States (7) with a total of > 22 000 participants have confirmed the therapeutic activity of SAMe against osteoarthritis. SAMe has effects similar to those of the nonsteroidal anti-inflammatory drugs, but its tolerability is higher.
  

Back to DAO

I think we have established the one mechanism for histamine degradation has useful pointers for those interested in autism; now it is time to look at the other one.

D-amino acid oxidase (DAAO; also DAO, OXDA, DAMOX) is an enzyme. Its function is to oxidize D-amino acids to the corresponding imino acids, producing ammonia and hydrogen peroxide.

Recently, mammalian D-amino acid oxidase has been connected to the brain D-serine metabolism and to the regulation of the glutamatergic neurotransmission. In a postmortem study, the activity of DAAO was found to be two-fold higher in schizophrenia.
DAAO is a candidate susceptibility gene and may play a role in the glutamatergic mechanisms of schizophrenia.  Risperidone and sodium benzoate are inhibitors of DAAO.


Abstract

We review the role of two susceptibility genes; G72 and DAAO in glutamate neurotransmission and the aetiology of schizophrenia. The gene product of G72 is an activator of DAAO (D-amino acid oxidase), which is the only enzyme oxidising D-serine. D-serine is an important co-agonist for the NMDA glutamate receptor and plays a role in neuronal migration and cell death. Studies of D-serine revealed lower serum levels in schizophrenia patients as compared to healthy controls. Furthermore, administration of D-serine as add-on medication reduced the symptoms of schizophrenia. The underlying mechanism of the involvement of G72 and DAAO in schizophrenia is probably based on decreased levels of D-serine and decreased NMDA receptor functioning in patients. The involvement of this gene is therefore indirect support for the glutamate dysfunction hypothesis in schizophrenia.

Abstract
D-serine has been shown to be a major endogenous coagonist of the N-methyl D-aspartate (NMDA) type of glutamate receptors. Accumulating evidence suggests that NMDA receptor hypofunction contributes to the symptomatic features of schizophrenia. d-serine degradation can be mediated by the enzyme d-amino acid oxidase (DAAO). An involvement of d-serine in the etiology of schizophrenia is suggested by the association of the disease with single nucleotide polymorphisms in the DAAO and its regulator (G72). The present study aims to further elucidate whether the DAAO activity is altered in schizophrenia. Specific DAAO activity was measured in postmortem cortex samples of bipolar disorder, major depression and schizophrenia patients, and normal controls (n=15 per group). The mean DAAO activity was two-fold higher in the schizophrenia patients group compared with the control group. There was no correlation between DAAO activity and age, age of onset, duration of disease, pH of the tissue and tissue storage time and no effect of gender, cause of death and history of alcohol and substance abuse. The group of neuroleptics users (including bipolar disorder patients) showed significantly higher D-amino acid oxidase activity. However, there was no correlation between the cumulative life-time antipsychotic usage and D-amino acid oxidase levels. In mice, either chronic exposure to antipsychotics or acute administration of the NMDA receptor blocker MK-801, did not change d-amino acid oxidase activity. These findings provide indications that D-serine availability in the nervous system may be altered in schizophrenia because of increased D-amino acid degradation by DAAO.


Abstract
We examined the association of autism spectrum disorders (ASD) with polymorphisms in the DAO and DAOA genes. The sample comprised 57 children with ASD, 47 complete trios, and 83 healthy controls in Korea. Although the transmission disequilibrium test showed no association, a population-based case-control study showed significant associations between the rs3918346 and rs3825251 SNPs of the DAO gene and boys with ASD.


DAO as a target for the treatment of schizophrenia

As noted above, both D-serine and D-alanine show some effectiveness as add-on treatment in schizophrenia, in particular for the amelioration of negative and possibly cognitive symptoms. There are also comparable approaches and data regarding glycine augmentation. Since enzymes represent viable drug targets, DAO is receiving attention as a potential alternative therapeutic means to enhance NMDAR function in schizophrenia. The fact that DAO activity appears to be increased in schizophrenia provides another reason to propose that its inhibition might be beneficial. It is also intriguing that the original antipsychotic, chlorpromazine, was shown to be a DAO inhibitor in vitro over fifty years ago,2 confirmed recently and also found to apply to risperidone; whether these observations are relevant clinically are unknown, but they do provide a precedent for the potential therapeutic benefits of selective DAO inhibitors.
To date there have been no clinical trials of DAO inhibitors in schizophrenia, but several preclinical studies which, although findings remain preliminary, show that inactivation of DAO, either in ddY/DAO- mice or after pharmacological DAO inhibition in rats and mice, produces behavioural, electrophysiological and neurochemical effects suggestive of a pro-cognitive profile (Table 4). The Table includes the three DAO inhibitors for which functional data have been published thus far: AS057278,10 CBIO,201,203 and Compound 8.202 Several other small molecule DAO inhibitors have been patented but their behavioural effects have yet to be reported.62,204

Conclusions and future directions

DAO, as the enzyme which degrades the NMDAR co-agonist D-serine, has the potential to modulate NMDAR function and to contribute to NMDAR hypofunction in schizophrenia. Both genetic and biochemical data support an involvement of DAO in the disorder, however the processes involved are difficult to interpret. This is due to the many questions left unanswered concerning the neurobiology of DAO and its physiological roles. Notably there is still much that is unclear as to its localization and activity within the brain, and its spatial and functional relationships with its substrates. In addition, D-serine and thus DAO may have roles other than NMDAR modulation, whilst other DAO substrates, especially D-alanine, may also be relevant to any involvement of DAO in schizophrenia. Similarly, although recent preclinical data hint at potential therapeutic benefits of DAO inhibitors, extensive further study is required to establish their efficacy, tolerability, and mechanism.


Many drugs act as DAO inhibitors to a limited degree, even though this is not their intended mode of action.

We have heard about Sodium benzoate and Risperidone, but there are many others.


           

Results

Chloroquine and clavulanic acid showed greatest inhibition potential on diamine oxidase (> 90%). Cimetidine and verapamil showed inhibition of about 50%.
Moderate influence on DAO was caused by isoniazid and metamizole, acetyl cysteine and amitriptyline
(>20%). Diclofenac, metoclopramide, suxamethonium and thiamine have very low inhibition potential (<20%).  Interestingly cyclophosphamide and ibuprofen displayed no effect on DAO.

Conclusion

Since even levels of about 30% inhibition may be critical, most of the observed substances, can be designated as DAO inhibitors. Other drug components than active ingredients did not affect DAO activity or its interaction with a specific drug.


Note that cimetidine (Tagamet), a histamine H2-receptor antagonist drug used in promoting the healing of active stomach and duodenal ulcers.  Verapamil is in my “Polypill” and is a potent mast cell stabilizer.   Is this link back to histamine a coincidence?  I think not.









Conclusion

The experts are yet to conclude much, but it does seem that SAMe levels are low in autism and brain DAO levels are high schizophrenia (adult onset autism).  In Korea, DAO was shown to be dysfunction in autism.

It seems that, by coincidence, Risperidone happens to be an inhibitor of DAO and this indeed accounts for some its side effects.  Risperidone has actions at several 5-HT (serotonin) receptor subtypes, Dopamine receptors, Alpha α1/2 adrenergic receptors and even H1 histamine receptors.  Risperidone seems to be drug of last resort.

There are no selective DAO inhibitors currently in use.

We did see that two old drugs Tagamet and Verapamil are potent DAO inhibitors in vitro.

This suggest to me that while sodium benzoate has been trialed “successfully” in schizophrenia, perhaps it would be worth comparing the effect of Tagamet and Verapamil.

When it comes to autism/schizophrenia, it would seem that in some people one or more of the following might be helpful:-

·        Sodium benzoate, or cinnamon a precursor
·        Tagamet the H2 antihistamine, already used by some people with mastocytosis
 ·        Verapamil, the calcium channel blocker that actually does much more
·        SAMe, or L-methionine a precursor.