On genes, environment, broccoli and autism (again)

Picture: Carl Warner: http://www.carlwarner.com/

I'm serving up two peer-reviewed papers for your reading delight today which draw attention to the ideas that (a) the 'causes' of autism are likely complex and as heterogeneous as the label itself, (b) gene x environment interactions affecting risk of autism are starting to get some good scientific research airtime and (c) don't 'dis the broccoli [chemical] autism connection just yet...

The first paper by Brandon Pearson and colleagues [1] (open-access) has already found some media interest as per the Guardian headline: 'Agricultural fungicides are 'bad news for neurons', study suggests'. Exposing mouse neurons - "cortical neuron-enriched cultures" - to several hundred chemicals (careful of that word) found in the modern environment, researchers concluded that several compounds "produce transcriptional changes in vitro that are similar to those seen in brain samples from humans with autism, advanced age and neurodegeneration (Alzheimer’s disease and Huntington’s disease)." That is, several types of chemicals quite commonly found in the modern environment seemed to alter gene expression in those mouse neuron enriched cultures that weren't a million miles away from that noted previously in conditions such as autism for example.

Mouse neurons, you might be thinking? Well, obviously one has to be a little cautious about extrapolating from mouse to humans (see here) but researchers did include some comparison analysis looking at "the gene expression profile of our cultures with brain cell-type-specific expression data sets and human brain gene expression data sets." The result: "cortical cultures show strong transcriptional similarities to the human brain."

Clustering chemicals based on "concordant gene expression changes", six groups emerged. Cluster 2 chemicals, containing such pesticides as rotenone, pyridaben and fenpyroximate  and also various compounds under the heading of the strobilurins seemed show some particularly interesting results insofar as they "mimicked the transcriptional changes of two post-mortem ASD [autism spectrum disorder] brain expression data sets in a bidirectional manner." The effects of this cluster of compounds also seemed to unite various conditions with autism including Alzheimer’s disease and Huntington’s disease and the "aging brain". My interest was particularly piqued by that last association in light of other research results (see here).

When it came to the 'effects' of those chemicals in terms of genetic and biological processes, researchers put forward some not unfamiliar potential roles: "These chemicals, most of which inhibit mitochondrial complex I or III, stimulated free radical production and disrupted microtubules." Words like 'oxidative stress' start to emerge as they have done in previous autism research (see here) and yet again, inflammation or inflammatory processes seem also to be indicated. Indeed, the authors also make mention of how effects such as free radical production "can be reduced by pretreating with a microtubule stabilizer, an antioxidant, or with sulforaphane." Yes indeed, sulforaphane - the chemical found in broccoli - might indeed be moving back up the autism research agenda (see here for some previous background).

There is obviously lots more work to do in this area before anyone gets too carried away. The authors note: "While usage and residue levels of cluster 2 chemicals on conventionally grown foods are increasing, in the absence of causality, it is premature to draw correlations with the increased prevalence of ASD and other brain disorders." Lessons could be learned from other blanket suggestions about 'chemicals' and autism (see here) as well as an appreciation for the concept of the the plural autisms (see here). Then there are the practicalities of whether ingesting such compounds on food or in water is the same as direct exposure to cortical neuron-enriched cultures? Or indeed, whether there may be other routes of contact? I might also suggest that further studies should focus on looking for the metabolites of such agents too [2] bearing in mind the concept of statistically significant thresholds...

If you're still here after all that, the second paper I want to talk about is that from Sarah Wong and colleagues [3] that has also received a bit of media attention. The focus this time was on a gene called p53 (see here for some background) and how issues with this gene might be 'over-represented' when it comes to autism following on from other work by some of the same authors [3]. First of all, please don't get too fixated by mention of the words 'cancer gene' when it comes to p53 given it's [protein] tumour suppressing capabilities. As I've discussed before, the risk of cancer does not seem to be elevated any more than the general population risk when it comes to autism (see here). Perhaps of greater relevance to the Wong findings is the idea that p53 has other 'activities' such as that related to oxidative stress (yes, that again) and "DNA repair, bioenergetics and mitochondrial DNA (mtDNA) copy number maintenance."

Based on data from CHARGE (beincharge!), researchers garnered blood samples from 66 children diagnosed with an autism spectrum disorder (ASD) and "race-, gender-, and age-matched typically neurodeveloping children (n = 46)" (authors words not mine). They analysed for mtDNA copy number and deletions and p53 gene copy ratios and found them to be "more common in children with AU [autism] and their fathers." The authors translate their findings as pointing to "a role for deficient DNA repair capacity not driven by paternal age." They also suggest that environment might intersect with genetics in relation to 'severity' scores of autism obtained for their cohort: "gene x environment interaction seems to play a greater role in children with autism with less severe symptoms."

Taken together the Pearson and Wong findings point to some interesting 'associations' potentially relevant to [some] autism. The idea that certain components of the modern-day environment might increase the risk of autism is nothing new but the way that Pearson et al went about studying the possible relationship is. The results from Wong et al suggesting that there might be issues with the gene 'whose role is to suppress cellular damage from environmental stressors' suggests that exposure patterns might not necessarily be where it's all at when looking at compound/chemical X or Y in relation to autism risk. I'm also inclined to direct you to some previous discussion about the caspases and autism (see here) in light of the involvement of p53 with the process of apoptosis (programmed cell death) in mind. As I've mentioned before, the biological mechanisms for how people deal with various xenobiotics needs a lot more investigation in autism research circles (see here); something that might similarly extend to genetic mechanisms too.

Oh, and just in case you think that I'm pushing the either/or of genetic and environment when it comes to autism, I'm not, as words like epigenetics spring to mind and the idea that genomic instability might, for example, have quite a few different dimensions (see here)...

To close, I'm thinking of branching out... football (soccer) pundit perhaps?

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[1] Pearson BL. et al. Identification of chemicals that mimic transcriptional changes associated with autism, brain aging and neurodegeneration. Nat Commun. 2016 Mar 31;7:11173.

[2] Domingues VF. et al. Pyrethroid Pesticide Metabolite in Urine and Microelements in Hair of Children Affected by Autism Spectrum Disorders: A Preliminary Investigation. Int. J. Environ. Res. Public Health 2016; 13: 388.

[3] Wong S. et al. Role of p53, Mitochondrial DNA Deletions, and Paternal Age in Autism: A Case-Control Study. Pediatrics. 2016. March 31.

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Pearson, B., Simon, J., McCoy, E., Salazar, G., Fragola, G., & Zylka, M. (2016). Identification of chemicals that mimic transcriptional changes associated with autism, brain aging and neurodegeneration Nature Communications, 7 DOI: 10.1038/ncomms11173




Wong, S., Napoli, E., Krakowiak, P., Tassone, F., Hertz-Picciotto, I., & Giulivi, C. (2016). Role of p53, Mitochondrial DNA Deletions, and Paternal Age in Autism: A Case-Control Study PEDIATRICS, 137 (4) DOI: 10.1542/peds.2015-1888

Organic diet and urinary pesticide concentrations

"Eating Organic Lowers Pesticide Levels in Children" went the headline reporting on the small study by Asa Bradman and colleagues [1] (open-access available here). Detailing what happened to urinary pesticides levels following trials of combinations of conventionally grown food consumption vs. organic food consumption over 16 days, researchers reported some potentially interesting findings.

Measuring 23 metabolites "reflecting potential exposure to organophosphorous (OP), pyrethroid, and other pesticides used in homes and agriculture" via everyone's favourite analytical method (LC-MS) and specifically "tandem mass spectrometry", Bradman et al observed that: "An organic diet was significantly associated with reduced urinary concentrations of nonspecific dimethyl OP insecticide metabolites and the herbicide 2,4-D in children." If I had a beef with any part of the Bradman study outside of the fairly small participant group, it would be that the reliance of urinary excretion of pesticide residues might not necessarily show the whole story, as per what data one might get from the use of other biofluids such as blood samples too or even analysis of fat biposies (recognising how invasive these can be).

These are interesting findings added to other similar research on this topic [2] looking at adults. Not only do they point to the idea that there is persistent low level exposure to pesticide residues in food but also that changes in food consumption patterns may affect such exposure events. That's not to say that food is the only way that pesticide exposure might occur, as per the findings of differences among children living in urban vs. agricultural communities (where those living in more agricultural areas generally had higher levels of some of the more frequently detected pesticide metabolites). But dietary change encompassing an organic diet did seem to lead to reductions in certain pesticide metabolite excretions irrespective of geography.

Accepting the often valuable reasons why pesticides are used in the first place, I don't think many people would argue with the idea that pesticide exposure should be limited, particularly in respect of children and their developing bodies and minds [3]. Allied to the idea that organic food might also confer other benefits in terms of nutritional quality (see here) and lower levels of fairly toxic metals such as cadmium [4], there seems to be common sense in rethinking some aspects of agriculture for certain groups. That the genetics of pesticide metabolism may also play a role [4] as per discussions about PON1 (paraoxonase/arylesterase 1), is also an important point and how childhood relates to PON1 activity among other factors [5]. Indeed, to answer the question posed in another paper [6] yes, there may indeed be some benefits from an organic diet for children...

Music: Adele - Rolling in the Deep.

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[1] Bradman A. et al. Effect of Organic Diet Intervention on Pesticide Exposures in Young Children Living in Low-Income Urban and Agricultural Communities. Environ Health Perspect. 2015 Oct;123(10):1086-93.

[2] Oates L. et al. Reduction in urinary organophosphate pesticide metabolites in adults after a week-long organic diet. Environ Res. 2014 Jul;132:105-11.

[3] Muñoz-Quezada MT. et al. Neurodevelopmental effects in children associated with exposure to organophosphate pesticides: a systematic review. Neurotoxicology. 2013 Dec;39:158-68.

[4] Barański M. et al. Higher antioxidant and lower cadmium concentrations and lower incidence of pesticide residues in organically grown crops: a systematic literature review and meta-analyses. Br J Nutr. 2014 Sep 14;112(5):794-811.

[5] Gonzalez V. et al. Cholinesterase and paraoxonase (PON1) enzyme activities in Mexican-American mothers and children from an agricultural community. J Expo Sci Environ Epidemiol. 2012 Nov;22(6):641-8.

[6] Vania A. et al. Is organic diet really necessary for children? Italian Journal of Pediatrics 2015, 41(Suppl 2):A75

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Bradman, A., Quirós-Alcalá, L., Castorina, R., Schall, R., Camacho, J., Holland, N., Barr, D., & Eskenazi, B. (2015). Effect of Organic Diet Intervention on Pesticide Exposures in Young Children Living in Low-Income Urban and Agricultural Communities Environmental Health Perspectives, 123 (10) DOI: 10.1289/ehp.1408660

What does detox mean?

Ever seen the original TV series 'V'?

I'm not talking about that new-fangled attempt with the fancy CGI effects; no, the 1980s one with the reptilian aliens, or at least the very plastic-mask looking reptilian aliens, wanting to turn humans into food. Even Freddy Krueger was a Visitor! (or the actor Robert Englund at least). Not a pretty thought I know, but if humans were ever to be sold as meat, by modern day standards, I question whether many of us would be fit to appear on the Visitors dinner table.

Sorry for the opening paragraph but what I wanted to suggest is that most people wouldn't disagree with the fact that modern day life, whilst presenting us with lots of comforts and labour-saving devices and technologies including those which have saved and extended our lives, also has it's downside. One downside of our romance with industrialisation is that we live in a very different environment from that only a few hundred years ago in terms of our exposure to lots of different things as a result of globalisation (viruses, bacteria, etc) and particularly our exposure to the various natural and man-made, synthetic chemicals. I kinda hinted at this in my last post on chlorination byproducts in the water.

I could write a whole thesis using the volumes of research done on what we could readily be exposed to on a daily basis from cradle to grave but I won't. Instead, here are a few references (here and here) to strengthen my point. Some of the compounds in question are pretty scary in terms of their potential biological activity and also their persistence in the environment. Asbestos, whilst being a natural product, is perhaps one of the archetypal industrial bad guys. For many compounds we just don't know what the long-term effects might be following either acute or chronic exposure and even worse, how they may interact with each other to potentially produce a more potent effect.

I read what I have written so far and think to myself, I don't live too near an incinerator or a chemical plant, I don't live too close to a busy road, I don't smoke, how would I be exposed? Well, easily. I need to drink, I need to eat, I need to breathe and I need to travel - traces of our industrial society are all around me (and you). In one way or another I will be exposed to many of them over the course of my lifetime. How my body handles them will depend on what the compounds are, the amount I am exposed to (and how frequently) and whether my genes-biology can metabolise them safely.

It is perhaps with all this in mind, that we have witnessed the rise of 'detoxification' as a suggested solution to relieving our chemical burden. I say chemical burden but detoxification has been put forward as an intervention for many different aspects of modern day life including that related to diet, medication and pollution.

Detox (to those in the know) means different things to different people. To some it is a trendy term which is used almost indiscriminately to denote some process of removing harmful compounds via 'natural' means. I remember people like Gillian McKeith using it in almost every second sentence coupled with words like 'superfoods', etc. To others, detoxification has a more 'scientific' meaning as related to things like the important function of the liver and its various enzymes for xenobiotic metabolism. Whatever your translation of the meaning, its use is part and parcel of the modern day dictionary.

A few months back I happened upon a very interesting article by Stephen Genuis. Some people might have heard his name before, particularly his recent work looking at the co-morbidity of coeliac disease in some selected cases of autism (and what happened to autistic symptoms when a gluten-free diet was implemented as part of the coeliac treatment regime). The article in question for this post is here* and is basically a review of what detoxification is and the various ways that is has been suggested to be useful.

I am sorry that I can't post a full-text copy of the paper (copyright y'know) because it is a very, very good review of detox which covers everything from description to the various challenges for toxicology research to summarising the various detox methods and their supporting evidence. I have supplied the reference at the foot of this post for anyone who is interested in popping through to their nearest academic library for a look. Genuis does not mince his words in this article in either his review of the evidence on the size of our chemical toxicity, the need for 'proof of safety not proof of harm', and his support for the budding environmental health sciences.

There is a case study included towards the end of his review paper about a previously healthy woman who developed many of the symptoms of psychosis. She was previously employed at a printing company which itself suggested several things in terms of potential environmental exposure. After various pharmacological treatments including antipsychotics, she was assessed by a separate physician who discovered high levels of bioaccumulated lead. Supervised chelation to bring down her lead levels correlated with an abatement of her psychiatric symptoms. I know this is only one case study and is limited to the findings of this n=1 but it does quite nicely illustrate our whole body relationship with contaminants. I made reference to lead in a previous post on the suggested reasons why the US crime figures are falling. I perhaps need to look at this with a more critical eye in the future.

There are a number of sensible take-home messages from Genuis and his review of other research being conducted in this area including:

• Quite a lot more finance and resources need to be put into investigating the whole area of chemical exposure and detoxification. An interesting study is just starting in the States regarding the possible impact that the Deepwater Horizon fiasco might have had on human health. Whether the financial onus should be on Government or the chemical production sector, I don't know.
• We have a very close, yet very complicated relationship, with our environment (and our genes). Just look at the recent post on genes and environment in the autism research world.
• With particular reference to one of our most sensitive organs, the brain, one should never underestimate how much our behaviour (and mis-behaviour) might be influenced by our natural and synthetic chemical surroundings. I should also point out that studying such a relationship is not easy.
• Detox, a widely used (and abused) term, is a legitimate concept.   

To finish, a song from the Chemical Brothers - "the time has come to... galvanize".

*Genuis SJ. (2011) Elimination of persistent toxicants from the body. Human & Experimental Toxicology. 30: 3-18.