Friday, 29 June 2012

The BTBR mouse and autism

Danger Mouse (from Wikipedia)
It is slightly overwhelming to see the wide range of investigative and research techniques on offer to the modern day scientist when it comes to researching conditions like autism. Indeed, the variety of disciplines and the tools of their trade involved in looking at autism from almost every conceivable research angle, makes it all the more difficult to understand why, at the time of writing, we continue to know so little about autism - aetiology, underlying pathology, etc. - despite such intensive efforts. I'm not here to answer that question by the way; aside that is from mentioning about heterogeneity, comorbidity, genetics-epigentics-environment and the well-trodden path that is 'if you've met one person with autism, you've met one person with autism'.

As per many other conditions / diseases / states, autism research has more than dabbled in the science of trying to establish suitable animal models for the condition as per this review by Paul Patterson* who runs quite a good blog (here). Without wishing to enter into any moral or ethical arguments with anyone about it, quite a few mice, rats, zebrafish and other creatures have met their Maker over the years in the name of autism research. Suffice to say that many more animals are probably going to join them in future; at least more than those who would have been involved in cosmetic research now the European Cosmetics Directive comes into final force (March 2013).

Animal models survive however because of the perceived comparison they can provide where investigations on human beings would not dare to tread. So, inserting genes, deleting genes, controlled exposure to various chemical and drug residues, and lots of other investigations all figure in autism animal research; studies which would not even be entertained to be involving real human beings. The big question though is: how much do such animal models truly tell us about a complex and heterogeneous condition like autism?

Bearing that question in mind, there is one particular animal model of autism which seems to be part of quite a few studies: the BTBR mouse or to give it the full title: the BTBR T+tf/J inbred mouse strain. I should add that I was brought to doing this entry partly following this post on the SFARI website.

Aside from being described as an 'exceptional breeder'(!), the BTBR mouse is of potential interest to autism research because it 'seems' to share quite a few overt behaviours more usually associated with autism spectrum conditions such those involved in social interaction, repetitive behaviours and impairments in play behaviour (see this paper). Even communication by the BTBR mouse has been suggested to some degree, to mirror that seen in autism (here). Throw in indications of 'high anxiety' and it all makes for an attractive animal model of autism.

So what has been noted about this mouse:

With the weight of this evidence you can perhaps see why the BTBR mouse might find some favour as a model of autism. There seems to be something for every research palate in among the various studies of the BTBR mouse. I'm certainly not going to poo-poo any comparisons but do have a few minor points to make aside from those already mentioned.

I am genuinely interested in what you might use as a comparator in mouse terms to the BTBR model. Most human studies around autism, certainly interventional or parameter-based, tend to use an asymptomatic control group (hopefully age- and sex-matched) or if you are very lucky, a further group of people with conditions like learning disability or a speech and language disorder (without autism) or the equivalent as comparators. I might be missing important details here but what do you compare an 'autistic mouse' with when ascertaining a specific biological or genetic parameter? Is there such a thing as an 'asymptomatic' mouse or a mouse with learning disability for example or is autism a spectrum of presentation in mice too? (no cheap jokes about systemising mice please).

A further point relates to the something that has cropped up on previous posts in terms of lab mice vs. wild mice and in particular the effects of environment on each as per this article by Boysen and colleagues*******. To quote: "These findings indicate a high degree of pre-activation of NK cells of free-living mice, indicating a strong environmental impact on NK cells, which may be highly relevant for interpretation of studies in the mouse model". In other words, lab mice in their nice sterile, clean-living, environment might not be hardened by the cruel outside world and therefore one questions their representativeness to the real world.

Indeed whilst animal models of 'disease' are the backbone of many a genetic or biological study, there are still some questions about whether they are truly delivering what they promised in terms of translating from lab bench to real-life as per the paper by van der Worp and colleagues******** (full-text) from a few years back. If this is the case, where does this leave the BTBR mouse?

[The picture included in this post will be recognisable to quite a few 'older kids' raised on 1980s UK television. For those who have not had the pleasure of watching Danger Mouse and his sidekick Penfold, here's some more information and that theme tune].


* Patterson PH. Modelling autistic features in animals. Pediatric Research. 2011; 69: 34R-40R

** Silverman JL. et al. Repetitive self-grooming behavior in the BTBR mouse model of autism is blocked by the mGluR5 antagonist MPEP. Neuropsychopharmacology. 2010; 35: 976-989.

*** Frye CA. & Llaneza DC. Corticosteroid and neurosteroid dysregulation in an animal model of autism, BTBR mice. Physiology & Behaviour. 2010; 100: 264-267.

**** Mercier F. et al. Meningeal/vascular alterations and loss of extracellular matrix in the neurogenic zone of adult BTBR T+ tf/J mice, animal model for autism. Neuroscience Letters. 2011; 498: 173-178.

***** Heo Y. et al. Aberrant immune responses in a mouse with behavioral disorders. PLoS One. 2011; 6: e20912

****** Corley MJ. et al.Reduced sulfate plasma concentrations in the BTBR T+tf/J mouse model of autism. Physiology & Behaviour. April 2012.

******* Boysen P. et al. Natural killer cells in free-living Mus musculus have a primed phenotype. Molecular Ecology. 2011; 20: 5103-5110.

******** van der Worp HB. et al. Can animal models of disease reliably inform human studies? PLoS Medicine. 2010;  7: e1000245.

Wednesday, 27 June 2012

Will that do NICEly for adults with autism?

A very quick post to bring to readers attention the publication today of the second strand of guidance on autism issued by the UK National Institute for Health & Clinical Excellence (NICE) looking at adults on the autism spectrum (full-text of document available here).

Many people, people with autism, their parents and professionals, will no doubt have already heard about NICE and the guidance being developed to cover the autism spectrum conditions in terms of diagnosis, care and management (see previous post); setting standards to cover what was quite a variable approach to autism throughout the lifespan.

The first strand of guidance examining the issues and best practices on the pathways to diagnosis of autism in children and young adults (see here) has already been published.

The final strand looking at the management of autism in children and young people (here) remains under development with an expected publication date of November 2013.

Metabolomics and Chronic Fatigue Syndrome

There were lots of things I could have blogged about in this post. The recent EEG autism biomarkers study by Duffy and Als* (full-text) which seems to be generating lots and lots of interest, despite the fact that we've kinda been here before (see this post on the Dark Arts); the interesting case study reported by Sildorf and colleagues** on remission without insulin therapy following use of a gluten-free diet in a pediatric case of type-1 diabetes; or even the high prevalence of vitamin D deficiency in psychiatric in-patients reported by Menkes and colleagues*** (full-text). All noteworthy findings and very much within the remit of this blog and its previous posts.

But instead, I'm turning my attention to another paper by Armstrong and colleagues**** and their application of a field close to my research heart, turning the scientific eye of metabolomics to Chronic Fatigue Syndrome (CFS).

Aside from a metabolomics link and the use of some quite powerful analytical technology, NMR, which has been previously applied to both autism (here) and schizophrenia research (here), this study also caught my eye because of what they reported finding.

A very brief summary:

  • Blood samples from a small patient group (n=11) diagnosed with CFS were analysed and compared with a small asymptomatic control group (n=10) via NMR. These participant groups are quite small but bear in mind the task ahead of the researchers given the number of potential compounds present in a blood sample (see this paper by Psychogios and colleagues***** on how many they found in human serum). I hasten to add that even in our lab we have found considerably more compounds to be present in other mediums like urine.
  • Significant reductions in the amino acids glutamine and ornithine were detected in the CFS group compared with controls. These findings also correlated with other metabolites linked to glucogenic amino acids and metabolites of the urea cycle.
  • I believe this to be only one of a handful of papers (that I can find) that discusses the application of techniques like NMR to CFS. On other occasions some interesting bacterial findings have been reported as per this paper by Sheedy and colleagues****** who I think might have been part of the same group (including Dr Henry Butt and the whole CFSUM1 and CFSUM2 episode).

My attention was immediately drawn to the reductions in glutamine which were present in this small participant group. Drawn because of the previously discussed 'possibility' of gut hyperpermeability in cases of CFS and the various suggestions that glutamine might play a role in intestinal permeability, or at least as an aid to improving such permeability in both animals (here) and humans (here). I might also add that lower levels of plasma glutamine have also cropped up in autism research too, bearing in mind that no direct connection between the conditions is intended. 

The literature on glutamine and CFS is still a little sparse. Aside from this paper looking at glutamine levels being related to something called 'overtraining syndrome' there's really not that much more to compare with. I note that exercise can induce changes to intestinal permeability (here) but wouldn't like to speculate on the mechanisms of this effect and any role for glutamine. I am on purpose also excluding the findings on glutamine related to ancillary conditions like fibromyalgia such as a raised glutamate/glutamine ratio (now where have I seen that before?)

I'm going to stop there with this interesting area of research which requires replication with much greater numbers. I've not really discussed the ornithine findings reported, simply because (a) there is even less research on this with CFS in mind, and (b) ornithine in relation to the urea cycle gets really, really complicated and my head is starting to hurt. Suffice to say that amino acid chemistry once again reveals itself as a possible correlate to another one of our heterogeneous medical syndromes without clues to causation. The question is: is the link with glutamine causation, association or just epiphenomenal?


* Duffy FH. & Als H. A stable pattern of EEG spectral coherence distinguishes children with autism from neuro-typical controls - a large case control study. BMC Medicine. June 2012.

** Sildorf SM. et al. Remission without insulin therapy on gluten-free diet in a 6-year old boy with type 1 diabetes mellitus. BMJ Case Reports. June 2012

*** Menkes DB. et al. Vitamin D status of psychiatric inpatients in New Zealand's Waikato region. BMC Psychiatry. June 2012.

**** Armstrong CW. et al. NMR metabolic profiling of serum identifies amino acid disturbances in Chronic Fatigue Syndrome. Clinica Chimica Acta. June 2012.

***** Psychgios N. et al. The human serum metabolome. PLoS ONE. 2011; 6: e16957.

****** Sheedy JR. et al. Increased d-lactic Acid intestinal bacteria in patients with chronic fatigue syndrome. In Vivo. 2009; 23: 621-628.

Monday, 25 June 2012

What's with 5-hydroxytryptophan (5-HTP)?

I might have said it before so please do excuse the repetition, but the aromatic amino acid tryptophan has been of some interest to me down the years. Like most people who have heard or know about tryptophan, the connection with serotonin (5-hydroxytryptamine or 5-HT) seems to be the big attraction when it comes to this very important amino acid and its pretty important effects on biology and daily life.

Putting serotonin slightly to one side for this post, I instead want to talk about another player along the tryptophan - serotonin pathway, 5-hydroxytryptophan (5-HTP) and various lines of study to this important intermediary compound in what is admittedly, a slightly disjointed post.

I was brought to this post by two factors:

  • An interesting comment in a LinkedIn discussion about how issues with the production of melatonin observed in some cases of autism might tie into other findings in autism in relation to issues with tetrahydrobiopterin (BH4) for example. Without trying to make connections where there may not be any, it got me thinking about the whole tryptophan - serotonin - melatonin pathway in a little more detail.
  • A curious paper which I stumbled upon a while back by Emanuele and colleagues* suggesting that the symptoms of romantic stress defined as "... a recent romantic break-up or reported recent romantic problems" might benefit from a brief dose of 5-HTP both behaviourally and biologically. Curious I know, and not necessarily relevant to this blog; but nevertheless it brought me back to 5-HTP.

Before your eyes start to glaze over and you reach for the 'click away' button, it is probably best if I start at the beginning and briefly show you how things usually go with regards to tryptophan, serotonin and melatonin. So in my very best handwriting (yes, you can perhaps see why I didn't ace certain school exams) and with no expense spared... see figure 1.
Figure 1: Bless you tryptophan.

In short:

L-Tryptophan is converted to 5-HTP via the enzyme tryptophan hydroxylase, TPH which relies on the cofactors of iron and BH4 for optimal functioning. Keep this cofactor thing in mind.

5-HTP is then converted to serotonin (5-HT) and onwards to various other compounds including 5-hydroxyindoleaceticacid (5-HIAA).

The conversion of 5-HT to melatonin is via the intermediate compound, N-Acetlyserotonin (NAS).

Just before anyone mentions, I have only included the TPH enzyme in my schematic and not the other enzymes involved in the various other reactions so as to keep it simple.

Hopefully you can see from my scribbles the central role tryptophan plays in this important metabolic process and how little issues with components in the pathway can potentially have knock-on effects for downstream metabolites.

So to the title of this post: "What's with 5-hydroxytryptophan?". Well, potentially quite a bit.

The first time I heard about 5-HTP was with reference to the collected data on the potential therapeutic use of the compound in cases of depression as per the Cochrane Review by Shaw and colleagues** (full-text). As per nearly every Cochrane Review I've ever read, the text reads something like, a few trials showing possible effects from [5-HTP] supplementation on depressive symptoms but not enough rigorous study to be able to form a suitable opinion. Don't believe me... well, see the Cochrane Review for GFCF diets for autism (here). Anyway, mention also of the fact that antidepressants already exist to 'treat' depression probably accounts for the drop in research interest in this area in recent years. That and possibly 'peak X' (see here for more details).

Where next?

Sleeping aid. Looking again at the magnificent figure offered to accompany this post, one could perhaps see how sleep could be affected by 5-HTP purely based on melatonin featuring some way down the pathway. The evidence.. well let's just say it needs improving despite some initial attempts (here and here). Additional evidence on any direct effect from 5-HTP administration on melatonin levels is even more scant.

Fibromyalgia. Heading into some pretty interesting territory here with again a dearth of recent investigations on this topic. Caruso and colleagues*** reported some interesting results from a double-blind, placebo-controlled trial of 5-HTP in fibromyalgia (FM) suggestive of positive effects to be had. Other, less controlled trials, also seemed to indicate some improvements in FM symptoms although with side-effects reported. Other than that, reviews and sprinklings of speculation.

Finally autism. Not much more to say aside from the very limited research on 5-HTP supplementation does not (so far) support any resounding changes to presented symptoms as per the paper by Sverd and colleagues****. Evidence has been presented to suggested that 5-HTP administration seemed to do a very good job at raising blood serotonin concentrations in males with autism (here). Whether this finding is (a) transferable to the majority and (b) might relate to issues with the availability of tryptophan as a starting material (in plasma and urine) or indeed the function of TPH (cofactor availability?) are still matters of speculation.

The Red Hot Chili Peppers @ Paul Whiteley
I'm just about done with 5-HTP for now. As per previous posts, the main caveat is that no medical advice or endorsement of anything is given or intended. Hopefully knowing a little bit more about 5-HTP after this post and how we should perhaps not be closing the research door on it just yet, would you be interested to learn that the gut microbiota might very well have an important effect on the serotonergic system*****? Accepting that bacteria and 'the microbiome' is a research area on the rise, one wonders whether 5-HTP might also have a hand in this process.

To finish, the Red Hot Chili Peppers rocked the SoL yesterday evening and so here is one of their finest... Higher Ground. And to the woman sat behind me who told me to sit down... it's a rock concert.


* Emanuele E. et al. An open-label trial of L-5-hydroxytryptophan in subjects with romantic stress.
Neuro Endocrinol Lett. 2010; 31: 663-666.

** Shaw KA. et al. Tryptophan and 5-Hydroxytryptophan for depression. Cochrane Database Syst Rev. 2002: CD003198

*** Caruso I. et al. Double-blind study of 5-hydroxytryptophan versus placebo in the treatment of primary fibromyalgia syndrome. The Journal of International Medical Research. 1990; 18: 201-209.

**** Sverd J. et al. Effects of L-5-hydroxytryptophan in autistic children. J Autism Child Schizophr. 1978;8: 171-180.

***** Clarke G. et al. The microbiome-gut-brain axis during early life regulates the hippocampal serotonergic system in a sex-dependent manne. Molecular Psychiatry. June 2012.
DOI: 10.1038/mp.2012.77

Thursday, 21 June 2012

Serum IgA, humoral immunity and autism

The important contribution of the late Reed Warren to autism research has been discussed previously on this blog. The findings from Warren and his team in relation to the C4B null allele in autism (and other conditions) were interesting and quite influential in opening the door to questions about the genetics of the immune system being implicated in some cases of autism. In light of the focus on epigenetics in recent years, I perhaps do question whether genomic differences might be the only influence on such gene function, but that's beside the point.

Another of Warren's astute observations on autism featured in this paper* from 1997 discussing a subset of people with an autism spectrum condition also presenting with a deficiency in immunoglobulin A (IgA). Indeed bringing things right up to date, another research group have reported similar findings as per this paper by Jolanta Wasilewska and colleagues** (full-text) specifically in relation to a group of children defined with regressive autism. A small additional point before progressing, Dr Wasilewska and other authors are no strangers to autism research as per their involvement with another interesting area related to oxalates and autism (see blog post here).

Let's just back up slightly and define IgA deficiency. A selective deficiency of IgA  represents an immunodeficiency and implies low or absent levels of IgA specifically tied into protection being afforded to various mucus membranes such as the airways or digestive tract. Described as being relatively common, selective IgA deficiency seems to be more apparent in conditions like coeliac (celiac) disease (here) and lupus (here) stressing the connection with autoimmune disease as per this review by Wang and colleagues*** (full-text).

A summary of the findings from Wasilewska et al:

  • The primary objective of their study was to ascertain whether tests of humoral immunity - immunity tied into secreted antibodies - might be able to identify children with autism, particularly those presenting with a regressive aspect to their symptom onset. A secondary objective relates to the examination of gluten-specific IgG antibodies in cases of autism which has been of some interest to this blog already (here).
  • Twenty-four children diagnosed with autism (and regression defined by a loss of previously acquired skills) were compared against 24 asymptomatic controls matched on various factors including age and importantly, gender.
  • Morning blood samples were drawn and collected from participants and serum IgA, IgG and IgM levels measured alongside various other measures including serum C-reactive protein (CRP) levels, lymphocytes and other measures of blood morphology.
  • Results: not too much significant group difference among quite a lot of the measures being looked at including CRP and white blood cell (WBC) counts. Interestingly, IgG anti-gluten antibodies were also not significantly different between the groups. 
  • Serum IgA levels were however significantly lower in autism as a group compared to controls; IgE levels just escaped being significantly elevated in the autism group compared to controls (p=0.08) with one spectacular outlier reported whose IgE levels were over double the amount of the second highest level seen across the groups. Also interestingly, eosinophilia - previously discussed in this post - seemed to be more prevalent in the autism group over controls despite no significant overall difference reported in blood eosinophils (p=0.08). Elevations in CD19 / CD23 - proteins found on the surface of B cells - were also noted in the autism group compared to controls (p=0.0134) confirming a role for humoral immunity (at least in some cases).
  • Some exploratory data on the usefulness of the various immunoglobulins measured were carried out to see how predictive they may be to regressive autism but unfortunately AUC values were not as stunning as other work in other areas.

Bearing in mind the small participant group included as part of this trial and how one defines regression, this is quite a comprehensive paper with some potentially important findings. The area of immunoglobulins in relation to autism is full of contrasting findings probably reflective of the fact that any issues with the immune system are probably not uniform in cases of autism and also focused on its nature according to the environment it works in. The mucus link to IgA is particularly interesting given that both airways and gut have cropped up more than once in autism research circles (here and here). That and the associations that have been made between certain medications - certain antiepileptic pharmacotherapy - inducing IgA deficiency for example, makes for some interesting speculations.

The IgE "nearly" findings take me back to the previous work done in this area and in particular that rather interesting area of research looking at mast cell activation in relation to autism. Of course there could be lots of reasons to account for the nearly findings in this recent trial and one should not perhaps speculate too much. I do however think that the eosinophilia data in the current study is an important finding given the links in other conditions between IgE, mast cells and eosinophilia; also adding to the previous (limited) literature on this topic with autism in mind, including another paper produced by Dr Wasilewska and colleagues.

I should finally comment on the CRP results obtained by Wasilewska and colleagues in light of my recent post on the paper by Khakzad and colleagues. Wasilewska reported no significant difference in CRP levels between the groups (means: autism = 0.1 mg/L vs. controls = 0.05 mg/L). Khakzad and colleagues reported  mean group CRP levels of 540.1 ng/L (autism) vs. 1.3 ng/L (controls). Noting the differences in concentration units (milligrams vs. nanograms), a quick re-calculation (using this handy tool 'cos I was too lazy to just divide by 1000) suggests that Khakzad was reporting CRP levels as quite a lot higher in their participant group (0.5401 mg/L) than in the Wasilewska participant group. Whether this is reflective of the different participant groups, differing ethnicities or geographical locations or other factors remains to be seen.

The growing (and growing) focus on the immune system and autism continues at a pace. Accepting a degree of individuality in how the immune system, different sides of the immune system, are positioned in cases of autism, it strikes me that once again, another set of parameters potentially reveal themselves which have been shown to be ripe for further tantalising endophenotype studies that are already starting to be done with autism in mind.

To finish, 'The Boss' is in town today so get your guitar and flag ready.


* Warren R. et al. Brief report: Immunoglobulin A deficiency in a subset of autistic subjects. JADD. 1997; 27: 187-192.

** Wasilewska J. et al. Low serum IgA and increased expression of CD23 on B lymphocytes in peripheral blood in children with regressive autism aged 3-6 years old. Archives of Medical Science. 2012; 9: 324-331.

*** Wang N. et al. Selective IgA deficiency in autoimmune diseases. Molecular Medicine. 2011; 17: 1383-1396.

Tuesday, 19 June 2012

Just wondering about CM-AT and autism

CM-AT. Ever heard of it? Well, if you haven't before you certainly might be hearing a lot more about it in the near future with autism in mind. I will from the outset stress that I am not writing this entry as some kind of 'advertorial' for CM-AT or anything like that, but rather because I am genuinely interested in this enzyme-replacement preparation developed by Dr Joan Fallon and how it might link in with some other favourite topics included on this blog. I would also refer you to a previous mention for CM-AT by MJ over at Autism Jabberwocky.

The details are still a little but sketchy about CM-AT in terms of exactly what it is and how it is supposed to benefit people with autism, some people with autism, but there are some clues in the literature so far. We know for example, that the formulation is intended as an enzyme-replacement therapy with autism in mind (see this excerpt published in Nature) which is probably designed to act on/supplement one or more enzymes; perhaps enzymes used in protein/peptide/amino acid metabolism? The digestive enzyme chymotrypsin seems to be a fairly big component of CM-AT as per the recent abstract reporting results at IMFAR 2012* and some details about the patent which has been filed (here). We even know that the results of a phase III randomised, placebo-controlled trial of CM-AT have been completed according to the entry.

No doubt there will be other sides to CM-AT - other pancreatic enzymes? - but at the moment I have little or no clue what exactly the preparation is aside from a few patent applications which I assume are related, including the enzyme delivery system (here) and a patent titled 'Methods of treating pervasive developmental disorder' (here). I note that Dr Fallon has previously published quite a speculative article on antibiotics and autism a few years back** but whether this is related to CM-AT or not is not known yet.

Without wishing to seem like I am vying for position as and when the CM-AT splash finally touches the beach, I'd like to think that there is some common sense in looking at things like enzyme function in cases of autism bearing in mind the results produced so far (see Munasinghe and colleagues***) and recent history related to molecules like secretinI'm also thinking back to a post which attempted to look at stomach acid and autism and the potential consequences of hypochlorhydria for both enzyme function and things like gut bacteria. Speculative but potentially interesting (at least to me). 

While we are on the topic of food and enzymes, let us also not forget the important links being forged between carbohydrate metabolism and enzyme function in cases of autism. Once again I am taken back to the Brent Williams paper on autism, carbs and dysbiosis as a central case in point, bearing in mind that the topic of carbohydrates and the various enzymes involved in their digestion is quite a broad area. 

I'll be keeping my eyes and ears open for any further developments on CM-AT and will update accordingly. To finish, and for all the Wannabes out there, some Spice from the 1990s.


* Fallon J. & Heil M. The role of a biomarker in the double blind placebo - controlled study of CM-AT in children with autistic disorder ages 3-8. IMFAR 2012.

** Could one of the most widely prescribed antibiotics amoxicillin/clavulanate "augmentin" be a risk factor for autism? Medical Hypotheses. 2005; 64: 312-315.

*** Munasinghe SA. et al. Digestive enzyme supplementation for autism spectrum disorders: a double-blind randomized controlled trial. JADD. 2010; 40: 1131-1138.

Sunday, 17 June 2012

Takin' a peek at pica

I arrived at this post following a thought-provoking newspaper story recently with the headline: The boy who is eating his own bedroom. There is an obvious degree of journalistic flair attached to the headline but the underlying description of a young boy with autism munching his way through his bedroom is something quite notable and understandably a source of some distress to his parents.

Definition: 'pica is a pattern of eating non-food materials, such as dirt or paper'. So goes the description provided by PubMed Health. Indeed, pica is apparently not such an uncommon issue among young children and women in particular, as partners of pregnant women the world over think back to late night shopping trips for such 'inedibles' as pickled onions or marmite (just kidding).

Seriously though, pica during pregnancy can be a very real occurrence. Likewise, many parents will have probably seen something approximating pica at some point in their child's early years; whether it be that lovely wallpaper border you bought for the little darlings room (that wasn't cheap!) or that elusive missing piece of the jigsaw puzzle (which re-emerges a few days later from a galaxy far, far away in a nappy or toilet basin). I think Piaget called it the 'sensorimotor stage'.

Pica in cases of autism and related conditions has been discussed before on this blog in one of my posts on zinc. Indeed the link with zinc in cases of autism (as in, some suggestion of deficiency in quite a few cases) shares some interesting comparisons with regards to zinc deficiency and cases of pica slightly outside of autism as per studies like this one and this one. Zinc is not the only element being linked to pica as per other research on iron deficiency suggestive of a link.

Given this and other data with regards to what happens to pica when such nutritional deficiencies are remedied, one gets the impression that there may be some kind of nutritional search potentially on-going in cases of pica rather than just mindless eating. But that might not be the whole story as per my recent post touching on gustational sensitivity and autism.

Where pica is present, there are a number of potentially important issues that might need to be looked at.

  • Bezoars and other foreign bodies are always going to be a concern depending on what is being eaten and its size. Various case studies litter the research environment with regards to intestinal obstructions in individual cases of autism as per these studies by Serour and colleagues* and Conyers & Efron**. I'm not quite sure about some of the suggestions put forward to stop pica behaviours such as the "minimally obtrusive, secure mask" suggested by Taylor & Walker*** and even less so for the use of aromatic ammonia examined by Rojahn and colleagues****. That's not to say however that behavioural 'training' might not have some effect on pica as per teaching about edible and non-edible items reported by Kern and colleagues*****.
  • Given the material and objects that pica may include (e.g. soil) there is always a risk of either some kind of poisoning or infestation as a result. So blood levels of things like lead have been touched upon in the research literature (here) and indeed quite recently suggested to be something to watch where pica may be an issue****** (full-text). I assume other metals might also require similar monitoring. Insofar as infestation, and in particular, parasitic infestation, the research literature with autism in mind is still sparse. Certainly parasites such as Giardia lamblia causing giardiasis are known to be associated with pica and there may be others too.
  • A final issue to bear in mind relates to the potential functional effect of long-term pica on teeth and dental health. I appreciate that dental health can be a tricky issue in relation to autism for lots of other different reasons not least difficulties in installing a consistent brushing routine and the effects of potential comorbidities such as bruxism (teeth grinding). If one considers that pica may include objects which are not necessarily all soft and fluffy such as stones/rocks, or may have the propensity to lead to frequent vomiting, you could see how teeth and oral health might also suffer. 

Appreciating that pica is not a part of every autistic persons behaviour, there are perhaps a few things that can be learned from pica when present. Regular readers of this blog will (hopefully) know that I am a bit of a believer in endophenotypes when it comes to autism - so subgroups are potentially apparent in the larger constellation that is know as 'autism'. The tie-up between pica and nutritional deficiencies is potentially an important clue to one of those phenotypes and dare I suggest it, a possible marker waiting in the wings?

* Serour F. et al. Intestinal obstruction in an autistic adolescent. Pediatric Emergency Care. 2008; 24: 688-690.

** Conyers R. & Efron D. Agitation and weight loss in an autistic boy. Journal of Pediatrics & Child Health. 2007; 43: 186-187

*** Taylor MB. & Walker RA. A minimally obtrusive, secure mask for prevention of access to the mouth. Clinical Rehabilition. 1997; 11: 77-79

**** Rojahn J. et al. Suppression of pica by water mist and aromatic ammonia. A comparative analysis. Behaviour Modification. 1987; 11: 65-74.

***** Kern L. et al. Reducing pica by teaching children to exchange inedible items for edibles. Behaviour Modification. 2006; 30: 135-158

****** Clark B. et al. Is lead a concern in Canadian autistic children? Pediatrics & Child Health. 2010; 15: 17-22

Thursday, 14 June 2012

C-reactive protein, inflammation and autism

More than a few people have argued that the balance between inflammation and er, not-inflammation, is the single most important battle being waged between health and disease. Such an assertion is made on the back of inflammation being implicated in all manner of conditions including obesitydementia and potentially even epilepsy.

The many faces of inflammation have also been quite a consistent theme across quite a few investigations on autism and related neurodevelopmental conditions. Although not by any means an expert, I have always found this to be a fascinating 'association' given that many people would probably view something like inflammation as being associated with more somatic signs and symptoms as for example, in response to an insect bite or such like. If one however assumes that the core embryonic material used to make skin for example is the same for other organs such as gut or brain, it makes it slightly easier to understand that inflammation is not just an overt process and just because you don't see it, doesn't mean that it's not happening.

Inflammation covers quite a lot of ground with autism in mind; ranging from neuroinflammation as per studies like this one and this one, through to comorbid inflammation of other tissues associated with various bowel findings for example (here), which still fuels some heated discussions in autism research and lay circles. I note that even the recent findings on maternal fever and offspring autism risk have been tied back to inflammation, albeit the suggestion of effects from ".. an acute inflammatory response". Inflammation, rightly or wrongly it seems, has had its card well and truly marked.

In this quite long post I want to discuss some of the very limited findings related to a particular protein called C-reactive protein (CRP) which is intimately linked to inflammation. The recent paper by Khakzad and colleagues* will also figure quite strongly and their reporting of significantly elevated levels of CRP in cases of autism.

A short description of CRP is in order. Apparently a pattern recognition molecule according to this quite detailed review by Black and colleagues** (full-text); levels of CRP increase dramatically following tissue injury or infection as part of a cascade of bodily responses. Interestingly there is a link between CRP and cytokines; in particular one familiar cytokine, IL-6, which has already received quite a bit of interest in autism research circles.

CRP has been mentioned previously on this blog in a couple of post discussing (a) some of the ins-and-outs of HBOT and how some quality time under hyperbaric conditions seemed to have some quite impressive effects on reducing levels of CRP in cases of autism, and (b) elevations in CRP detected in a group of parent carers with children with autism. Inflammation was the name of these games and higher, not lower levels of CRP as a marker of such inflammation seemed to be the important findings although I should stress CRP levels have not been consistently detected as being elevated in every study of autism.

Outside of these studies, there is the odd mention of CRP but more often than not, it is the cytokines, the balance between pro- and anti-inflammatory cytokines, which seemed to have stolen the show in autism research. It was therefore of interest to see the paper by Khakzad and colleagues appear, and to summarise:

  • Based on the use of a high-sensitivity measure for CRP (hs-CRP), serum levels were measured in 39 participants with autism compared with 30 age-matched asymptomatic controls in a snapshot study. Participants with autism were further divided on the basis of CARS scores into moderate vs. severe presentation - most fell into the former category.
  • Group levels of CRP were significantly (very significantly) elevated in the autism group compared with controls (P<0.0001); mean CRP values in the autism group were 540.1 ng/ml compared with 1.3 ng/ml in the control group. Severity of symptoms based on CARS scores were also related to CRP levels in that those with the most severe presentation of autism tended to show greater serum levels of CRP than those presenting with more moderate symptoms. There was a significant correlation between symptom severity and CRP levels although given the sample size, strength of association and less than impressive scatterplot of the data, I would perhaps chance that this finding requires some further replicative work.
  • To quote the authors: "These findings affirm the role of inflammation in autism". 

Appreciating the small scale nature of the Khakzad paper and other factors relating to the participants they looked at (I assume they were all Iranian although the paper does not actually make this clear) and the snapshot view of CRP levels, there are some interesting comments to make from this research.

First and foremost is that whether you overtly see it or not, inflammation is a facet of at least some cases of autism. There are of course the arguments about which came first - autism or inflammation - and indeed whether the two are linked or whether inflammation is just purely epiphenomenal or a manifestation of comorbidity for example. I can't provide any an opinion either way aside from saying that the authors did collect some questionnaire data on among other things past medical history of participants. Aside from 'family history' being significantly different from controls (?), the presence of comorbid epilepsy was the only statistically significant difference between the groups.

An association between certain types of epilepsy and elevated CRP has been suggested and so one cannot perhaps discount this as being an interfering variable bearing in mind the lack of data on what types of epilepsy were present in the Khakzad study. Indeed given the link between IL-6 and CRP levels, elevations in IL-6 linked to seizure disorders is further evidence for a link and an interference when it comes to assessing association and causality.

The possibility of other comorbidity accounting for elevations in levels of CRP is another source of bias. I say this on the back of quite a lot of research suggesting elevated CRP levels in relation to inflammatory bowel diseases (here), asthma (here) and type-1 diabetes (here) for example; all of which have been mentioned to some extent in relation to autism as a comorbidity. Don't even get me started on the links suggested between depression and CRP (here).

The suggestion of a positive correlation between increasing CRP levels and increasing severity of autism symptoms is an interesting assertion despite the need for further study. I note for example that similar suggestions have been reported in cases of schizophrenia for example as per this article by Fan and colleagues***. Similar suggestions in relation to mania and CRP have also been reported by Faith Dickerson and colleagues**** (a name mentioned before on this blog). Exactly how this might play out from a mechanistic point of view is slightly uncertain but nonetheless an important next research step alongside ascertaining whether specific endophenotypes / subgroups on the autism spectrum may be more prone to elevated CRP levels as a function of things like symptom onset (regression vs. no regression) and other parameters.

As per the opening sentences to this post, inflammation is readily becoming the villain under lots of different scenarios. The data emerging in cases of autism warrant further research attention with regards to inflammation and CRP levels to understand if autism spectrum conditions should be added to the list of possible connections and importantly, if and how inflammation links to presented behavioural symptoms and what can be done about it (no advice intended). From a strictly health point of view, the growing implications of chronic elevations of CRP for cardiovascular health are for example, a worry for any group/person with potential long-term, low grade inflammation established by CRP measurement.

To finish, y'know we can dance if we want to. Who said Morris dancing was boring?


* Khakzad MR. et al. The complementary role of high sensitivity C-reactive protein in the diagnosis and severity assessment of autism. Research in Autism Spectrum Disorders. 2012; 6: 1032-1037
DOI: 10.1016/j.rasd.2011.10.002

** Black S. et al. C-reactive protein. Journal of Biological Chemistry. 2004; 279: 48487-48490

*** Fan X. et al. Elevated serum levels of C-reactive protein are associated with more severe psychopathology in a subgroup of patients with schizophrenia. Psychiatry Research. 2007; 149: 267-271.

**** Dickerson F. et al. Elevated serum levels of C-reactive protein are associated with mania symptoms in outpatients with bipolar disorder. Progress in Neuropsychopharmacology & Biological Psychiatry. 2007; 31: 952-955.

Tuesday, 12 June 2012

mTOR and autism

Now don't be put off by the title of this post or the 'jargon' that follows but I want to talk about something called mTOR. I know, I know, it sounds like Godzilla's cousin but it's not; it might actually be a whole lot more important than that.

mTOR aka the mammalian target of rapamycin has been cropping up quite frequently during my various searches of the research literature. I was intrigued by the name of this ubiquitous protein kinase which apparently is involved in all manner of things including protein synthesis and synaptic plasticity. Some interesting findings in relation to depression and the mTOR signalling pathway have been reported but it might not end there.

I don't want to blind you with science - science which I am barely coming to grips with myself - but important parts of the mTOR story are the complexes: mTOR complex 1 (mTORC1) and complex 2 (mTORC2) whereby mTOR holds hands with other proteins and heads off into slightly different functioning directions. This paper by Laplante & Sabatini* (full-text) is about a good an overview of the different complexes as you are likely to find.

When it comes to autism, mTOR seems to be of increasing interest, having had quite a surprising journey. As far as I can make out, it all started with some interesting work on tuberous sclerosis, a genetic condition defined by the presence of benign, non-cancerous tumours in different parts of the body, but also potentially presenting with autism or autistic-like behaviours. Meikle and colleagues** (full-text) described some preliminary findings based on the inhibition of mTORC1 by rapamycin and an interestingly titled compound called RAD001. These quite potent immuno-suppressive compounds more frequently used to counteract organ rejection after transplant, seemed to have quite an effect on survival rates and a few other areas at least in the mouse model. This work was extended to cover some of the behavioural and learning disabilities, again in the mouse model of tuberous sclerosis*** (full-text).

The more recent research on mTOR seems to be more directed to autism outside of just the tuberous sclerosis and Fragile X syndrome link. The paper by Ehninger & Silva**** (full-text) summed up the potential use of rapamycin in relation to a subset of cases of autism spectrum conditions and the paper by Talos and colleagues***** (full-text) brings us up to date with their suggestion that mTOR might show some link to autism and epilepsy via that most interesting of amino acids, glutamate and onwards glutamingeric transmission. I might add that I am in no way endorsing the use of rapamycin or anything else for autism.

Even this year's IMFAR conference carried mention of mTOR and autism as per these three abstracts: here, here and here. Again I don't profess to be the wise old sage when it comes to these findings but am interested in a few aspects of these works in relation to annexin 1 (and its anti-inflammatory effects) and the whole brain-derived neutrophic factor (BDNF) story which in the case of autism, probably deserves a post of its own at some point.

There is still a way to go with the mTOR pathway and indeed how pertinent it might be to cases of autism and other conditions as per its cellular growth and proliferation duties. That and its ability to direct immune responses as per the review by Delgoffe & Powell****** (full-text) represents a work in progress.

In the words of the great Ferris Bueller, 'you're still here'. Well if you are, how about some music courtesy of Blondie and possibly their best song... Atomic as memories of Obi-Wan's other acting performances come to mind.

* Laplante M. & Sabatini DM. mTOR signalling at a glance. Journal of Cell Science. 2009; 122: 3589-3594.

** Meikle L. et al. Response of a neuronal model of tuberous sclerosis to mTOR inhibitors. The Journal of Neuroscience. 2008; 28: 5422-5432.

*** Ehninger D. et al. Reversal of learning deficits in a Tsc2+/− mouse model of tuberous sclerosis. Nature Medicine. 2008; 14: 843-848.

**** Ehninger D. & Silva AJ. Rapamycin for treating Tuberous sclerosis and Autism spectrum disorders. Trends in Molecular Medicine. 2011; 17: 78-87.

***** Talos DM. et al. The interaction between early life epilepsy and autistic-like behavioral consequences: a role for the mammalian target of rapamycin (mTOR) pathway. PLoS ONE. 2012; 7: e35885

****** Delgoffe GM. & Powell JD. mTOR: taking cues from the immune microenvironment. Immunology. 2009; 127: 459-465

Saturday, 9 June 2012

Melatonin and autism updated

I've covered some of the research on autism, sleep and melatonin previously on this blog. That post was a gentle introduction to to the topic of melatonin which I've decided to upgrade with this latest offering.

Perhaps an introduction first?

Melatonin is an interesting compound synthesized in the pineal gland from another interesting compound, serotonin (5-HT). The intermediate compound formed, N-acetylserotonin (NAS), is itself something which could really do with a lot more investigation given some suggestion of an anti-depressant effect among other things.

I could tell you all about the sleep-wake cycle connection of melatonin but aside from that there are also some other interesting activities of the compound, for example with regards to antioxidants as per this review by Hardeland & Pandi-Perumal* (full-text) from a few years back. I was particularly interested in the connection between melatonin and that old favourite glutathione but am not going to dwell on it.. OK, but not too much.

So what's the story with regards to autism and melatonin?

Well, quite a bit. Generally speaking(!) levels of circulating melatonin and some of its metabolites are noted to be on the low side in cases of autism as per the meta-analysis by Drs Rossignol and Frye**. Even more recent research*** looking at both daytime and night-time levels of the main metabolites of melatonin, 6-sulphatoxymelatonin, confirmed issues with melatonin production to be present in cases of autism. Interestingly also linking production issues with degree of symptom severity.

Why might melatonin production be aberrant in cases of autism?

The big question and I'm afraid that I don't have a big answer. There are a few possibilities: issues with the pineal gland or suprachiasmatic nucleus (the master clock centre), issues with serotonin or the starting material tryptophan, issues with the various reactions in the metabolism of melatonin (or precursors)... take your pick bearing in mind this list is not exhaustive.

I find it particularly interesting that (a) there might be a sensory-perceptual link to the production of melatonin which might be related to melatonin issues in some cases of autism, and (b) acetylation and methylation are required steps in the metabolism of melatonin. I might be making mountains out of molehills again but it strikes me that some people on the autism spectrum aren't exactly flush when it comes to methylation. Just speculating of course.


Again with the very important caveat about not giving medical advice, melatonin does seem to have quite a good record when it comes to at least some cases of autism spectrum conditions and a few other diagnoses. Sleep and the regulation of sleep is the obvious target of melatonin, which itself can have some pretty important influence on presented behaviour.

Two quite recent trials extended the good news about melatonin: this one from Malow and colleagues**** and this one from Cortesi and colleagues*****. Outside of the CBT data, I was particularly interested in the 'controlled-release' bit of the work by Cortesi and co. given the mechanics of variations in endogenous melatonin production. It strikes me that melatonin is an ideal candidate for some of the newer release technologies being looked at in the world of medicines; such that transdermal patches and the like might have something valuable to offer as per other trials. I might talk about patches and newer methods for medication delivery further at some point in the future.

Having said that, and bearing in mind that lots and lots of different 'medications' have probable biological actions outside of those just intended, melatonin might not be just acting on sleep. I recently read an interesting (and yet again, speculative) review article about melatonin as a molecular 'handyman' by Boga and colleagues****** which does get you thinking about the hows and whys. Even the concept of combination therapy seems to have reached melatonin research.

To finish, something rather sleepy from Mama Cass - 'Dream a little dream of me' (but not literally)... yawn.

* Hardeland R. & Pandi-Perumal SR. Melatonin, a potent agent in antioxidative defense: Actions as a natural food constituent, gastrointestinal factor, drug and prodrug. Nutrition & Metabolism. 2005; 2: 22
DOI: 10.1186/1743-7075-2-22

** Rossignol DA. & Frye RE. Melatonin in autism spectrum disorders: a systematic review and meta-analysis. Developmental Medicine & Child Neurology. 2011; 53: 783-792.

*** Tordjman S. et al. Day and nighttime excretion of 6-sulphatoxymelatonin in adolescents and young adults with autistic disorder. Psychoneuroendocrinology. May 2012.

**** Malow BA. et al. Melatonin for sleep in children with autism: a controlled trial examining dose, tolerability, and outcomes. JADD. December 2011.

***** Cortesi F. et al. Controlled-release melatonin, singly and combined with cognitive behavioural therapy, for persistent insomnia in children with autism spectrum disorders: a randomized placebo-controlled trial. Journal of Sleep Research. May 2012.

****** Boga JA. et al. Beneficial actions of melatonin in the management of viral infections: a new use for this "molecular handyman"? Reviews in Medical Virology. April 2012.

Thursday, 7 June 2012

Autism's environmental exposome: fish and pharmaceuticals

It's late and it's been a long day but I'm somewhat intrigued by the publication of a paper by Thomas & Klaper* (full-text) recently published in PLoS ONE on unmetabolised psychoactive pharmaceuticals, gene expression in fish and autism.

Intrigued not only because the combination of fish, drugs and autism feature heavily in this paper but also because the findings presented in this study offer some interesting proposals about "autism's environmental exposome" which translated means how environment, and various exposure events in the environment, might be linked to autism.

The paper is full-text but here is a brief summary:

  • Based on some very logical assumptions about any potential candidate environmental 'trigger' for autism (plausible mechanism, existing in sufficient quantities in the environment, ability to pass from mother to foetus, historical increase in concentration coincident to the rise in autism cases), the authors set about looking at the possibility that pharmaceutical drug residues persistent in the environment may be linked to idiopathic autism - that is autism not secondary to other conditions such as Rett Syndrome (RTT) or Fragile-X syndrome (FXS).
  • Allowing for the fact that the use of human participants is not all that ethical in looking at such a relationship, the authors tested mixtures of so-called unmetabolised psychoactive pharmaceuticals (UPPs) on a fish model and the ability of UPPs to induce autism-like gene changes modelled from other data. I might add that gene models of other conditions including ADHD, schizophrenia, depression and bipolar disorder were also included in the analytical mix.
  • I can't claim to be an expert on the techniques employed but fish (fathead minnows) were housed in tanks which either contained the UPPs mix made up of a mixture of fluoxetine, venlafaxine and carbamazepine in concentrations described as ".. the highest observed environmental concentrations" compared with control tanks (no pharmaceuticals included). Duration of exposure was over the course of 18 days.
  • The authors conducted a "... gene-class analysis of expression patterns induced by the pharmaceutical treatments"; in other words, examining fish brain tissue from exposed animals to see what happened to gene expression as a result of exposure.
  • Lo and behold, gene enrichment linked to idiopathic autism came out on top following exposure to UPPs. Gene models of a few other conditions also showed some changes following UPPs exposure but not to the extent or consistency as that noted in autism. The importance of idiopathic autism showing gene enrichment over so-called secondary autism (following cases of RTT or FXS) is not be underestimated given the link to genes already noted in cases of RTT and FXS.
  • The authors make the connection between their reported findings and elevated levels of serotonin (5-HT) being implicated in autism spectrum conditions. Further, the proposed connection between maternal SSRI use and elevated offspring autism risk (discussed in this post) also comes into play. The potential added value from this study is that exposure to these classes of medication need not necessarily be voluntary.

I won't lie to you when I say that I am really quite excited by these findings. Accepting important factors such as the focus being on fish not humans, the quite high amount of exposure over a relatively small time period and the assumption that the 'autism genes' are in fact autism genes, I would certainly like to see some independent replication of this study.

I've talked about environment in relation to autism previously (here) and how things just 'aint what they used to be in terms of our interaction with the chemical environment. Without trying to push too hard an environmental agenda for autism, some cases of autism, or misrepresent what the word 'chemical' actually means (see here), there are some really important considerations to take from this study; not least on how we dispose of our pharmaceuticals and the potential risks attached to (unwitting) exposure to them.

If there are any positive points to come from this study, a primary one is the experimental model and methodology used. So whether replacing UPPs with other chemical components such as those speculatively listed in the 'top 10 hit list' recently discussed might produce similar effects, would be a study worth doing. Indeed thinking back to the chlorination by-products and autistic behaviour paper published last year (here), another important experiment waiting to be done using the fish in a pot gene expression model.

* Thomas MA. & Klaper RD. Psychoactive pharmaceuticals induce fish gene expression profiles associated with human idiopathic autism. PLoS ONE. June 2012

Tuesday, 5 June 2012

Autism said NO

Another play on words form the title of this post. Whilst no means no (or even NoMeansNo if you are partial to a little punk rock), NO in this case actually refers to nitric oxide and a few snippets of research potentially relevant to autism and a few other conditions.

A recent paper in bipolar disorder research brought me to this post. The paper by Bielau and colleagues* suggested evidence of issues with NO signalling might be a facet of bipolar disorder. When I read the words "influences the balance of monoaminergic and glutamatergic neurotransmission" I thought to myself that it was about time to look at NO with autism in mind, given the quite interesting links being suggested around glutamate and autism for example.

Indeed, it was perhaps inevitable that I would arrive at NO at some point on this blog given the numerous references to inflammation and oxidative stress seemingly present in some cases of autism spectrum conditions as exemplified by the post on glutathione and autism. The more general connection between NO and inflammation is a complicated one but nevertheless an important one. I might add that I will be coming back to inflammation and autism in future posts.

A brief history of NO and autism.

This paper by Zoroglu and colleagues, whilst built on a small participant group, paved the way for several subsequent studies of NO metabolites in plasma and urine. Zoroglu is a name that comes up quite a bit in NO research. Findings of elevated levels of NO metabolites are pretty consistent in the autism studies so far as evidenced by this paper and this paper. Even research which did not find any group connection between elevated NO and autism, implied that the onward problems following a Clostridial infection in a case of autism might show elevated NO values (Clostridia difficile toxins can do some pretty nasty things to the gut).

More recent publications continue the theme. So this paper by Essa and colleagues** added to the melting pot of research. Based on the analysis of a small group of children with autism living in the Sultanate of Oman, a significant elevation among several markers of oxidative stress were found including plasma levels of NO. An even more recent study published by Tostes and colleagues*** also reported elevations in NO alongside quite a few other issues such as elevations in interferon-gamma (IFN-γ) and some other very interesting peptide findings (e.g. VIP). Again based on quite a small participant group.What this might imply is that elevated NO levels in cases of autism may represent cases of autism with some kind of 'inflammatory' process attached.

Not yet convinced about a possible role for NO in some cases of autism?

Even the father of the minicolumn hypothesis Prof. Manuel Casanova might be swayed by the potential for a link. What to do about NO is altogether another matter and indeed it might not just be a case of trying to reduce levels or somehow reduce the source of the inflammation. A positive effect from NO in relation to cardiac function has been pretty well documented as evidence by papers such as this one. NO might also happen to be quite a good antioxidant; with a little seemingly going a long way.

The question is whether there might be a tipping point; a point where too much of a good thing causes problems and whether what has been seen in cases of autism and in other conditions, represents too much?

* Bielau H. et al. Immunohistochemical evidence for impaired nitric oxide signaling of the locus coeruleus in bipolar disorder. Brain Research. 2012; 1459: 91-99

** Essa MM. et al. Increased markers of oxidative stress in autistic children of the Sultanate of Oman. Biological Trace Element Research. November 2011.

*** Tostes MH. et al. Altered neurotrophin, neuropeptide, cytokines and nitric oxide levels in autism. Pharmacopsychiatry. March 2012.