Tuesday, 24 April 2012

Glutathione and autism reloaded

I hope that I don't seem to be treading on old ground with this post on glutathione (GSH) and autism. I have covered some research on a possible link between glutathione and autism spectrum conditions previously (see here) following some interesting suggestions on the potential value of measuring GSH levels as a kind of biomarker for autism. The caveat being that despite an initial AUC=1 much more investigation is required.

This post is slightly different in that I wish to bring to your attention a review paper by Main and colleagues* (full-text) which highlights pretty much what we know, or think we know, about GSH and autism so far. Before progressing I think I should reiterate my caveat of not providing medical or other advice and strongly recommending that a medical physician be involved in all decision making aspects impacting health.

Aside from the content of the paper which I will run through shortly, a familiar name on the authorship list pulled me into this post. Dr Manya Angley, a Pharmacist from the University of South Australia, who has been involved in some really interesting work in autism research (here and here) was part of the team. Avid readers of this blog (if there are any!) might remember my first ever blog post on a paper with some pretty nifty techniques and results based on gut bacterial metabolites turning up in the urine of a group of children with autism. Well, Dr Angley was part of that authorship team also with some impressive company.

The current review carries a few interesting details:

  • It pretty much highlights all the work that has been done on measuring glutathione levels in autism up to November 2011. As anyone who has done a systematic review will tell you, this is no mean feat and perfect for answering an undergraduate exam paper such as 'Glutathione and autism: describe and critically discuss'.
  • Lower levels of GSH and alterations to chemical relations in cases of autism are a pretty consistent feature of the research carried out so far.
  • Serum cysteine levels also seem to be reduced and potentially associated with the severity of presented autistic symptoms. One has to wonder how this might fit into the sulphation issues previously highlighted in cases of autism and whether indeed as in some cases of schizophrenia also, cysteine in the form of NAC might be an area requiring much more serious investigation.
  • Serum homocysteine levels in cases of autism don't seem to show significant differences with control values. I was slightly shocked by this finding given previous research. Indeed a more recent paper not included in the current review suggested that hyperhomocysteinemia might be a useful biomarker for autism itself.
  • A significant increase in plasma vitamin B6 - pyridoxal-5′-phosphate - was noted in several studies potentially relating to issues with the bioavailability of the vitamin. Perhaps one reason why B6 never lived up to its potential

There is quite a lot of other information included in this review which should keep any interested parties content for a few hours. I would hasten to add that in this post I am not uniformly suggesting that everyone with autism has issues with glutathione, cysteine or homocysteine as per my mantra of heterogeneity and comorbidity.

One would however hope that with the continuing development of the third and final NICE guidance for autism in children and young people here in the UK, reviews like this one will figure strongly in informing the panel about potential areas of importance. If anything else this paper should invigorate some real interest into how amino acid and antioxidant chemistry in autism is not just alternative "biomedical" mumbo-jumbo.

To finish, the Carpenters and 'Top of the world'. Have a great day!

* Main PAE. et al. The potential role of the antioxidant and detoxification properties of glutathione in autism spectrum disorders: a systematic review and meta-analysis. Nutrition & Metabolism. April 2012.
DOI: 10.1186/1743-7075-9-35