Saturday, 19 February 2011

Gut microflora, urine and autism

OK, first proper posting.

The journal Biomarkers posted a new study today on the detection of p-cresol in urine samples from children with autism. A link to their abstract can be found here. I don't have the full article yet but the abstract is quite descriptive.

Basically they reported findings based on 59 children and matched controls, where analysis for para-cresol was by High-Performance Liquid Chromatography (HPLC) with ultra-violet detection. Levels of p-cresol were elevated in children with autism compared to controls and more specifically in younger and more severely affected children. p-cresol is an interesting compound (more details are available here) in that whilst derived from several environmental agents, it also potentially relates back to specific types of gut bacteria (as per the author report). The authors were able to exclude one environmental agent (exposure to tobacco smoke) as a significant factor relating to their findings by analysis of urinary cotinine.

There are a few comments to make about this. First such metabolites have been examined in relation to autism during previous studies. Yap and colleagues (2010) reported on levels of 4-cresol sulfate in their study of urine samples from people with autism. They found no overall difference in this related metabolite compared with controls and siblings in their samples (their methods were based on a superior analytical system, NMR). Yap and colleagues did however conclude on the basis of various other metabolites analysed during their study, some invovement for gut microbiota in some cases of autism.

Second, there is quite a body of evidence building up to suggest the involvement of gut bacteria in some cases of autism. A few choice links are here and here. It is still an area under investigation; one question that has not been answered is whether the various gastrointestinal co-morbidities reported in some cases of autism show involvement with cases where such bacterial species have been found and whether they are "causative", "resultant" or just coincidental.

Finally, assuming that there is an issue with gut bacteria and autism, what then is there to do about it and what potential effect will it have. On this issue I was reminded what I was told quite a while ago by a pretty eminent researcher on the connection between our gut bacteria, our immune system and good old homeostasis - can we actually change what we have?

There is some limited evidence that in the short-term at least eradication of certain types of gut bacteria could have knock-on effects for autism (see here). Note however the use of the words "short term". This kind of goes back to the whole issue of taking probiotics in an attempt to influence gut bacterial populations as is so evident nowadays and whether we are truly able to influence our bacterial colonies in a long-term and sustainable way to impact on our health. I don't have an answer unfortunately. Still, this study does present another potentially important marker requiring further study.