Normal Limits

"Chance is the very guide of life"

"In practical medicine the facts are far too few for them to enter into the calculus of probabilities... in applied medicine we are always concerned with the individual" -- S. D. Poisson

November 14, 2005

Sci Am - Bugs and Drugs: Gut bacteria could determine how well medicines work

This Scientific American story refers to this paper in Toxicological Sciences by Lora Robosky et al at Pfizer Global Research.

Robosky et al found that, surprisingly, mice that are genetically identical may metabolize chemicals differently based on variations in their gut microbial flora. The study of bacterial colonizers in the gut is a recent development.
Through genomic sequencing ... Paul Eckburg at the David Relman Lab at Stanford estimates at least 400 species in our gut.

... Scientists have only just begun to elucidate how these mysterious bugs influence health... Two years ago, for example, David G. Binion of the Medical College of Wisconsin showed that the sodium butyrate produced by gut microorganisms could inhibit blood vessel growth in the intestine by blocking COX-2--an enzyme implicated in many inflammatory disorders (and the target of drugs such as Vioxx). Other studies have shown that specific strains of Escherichia coli can metabolize dimethylarsine, a derivative of arsenic, to produce potentially toxic compounds, which may underlie the carcinogenicity of arsenic in the gut... the discovery may partly explain why data from presumably identical animals sometimes conflict.

The is Gene x Environment interaction at its best. Recall this famous experiment in 1999 which was demonstrated the absolute difficulty in controlling and holding constant the effect of the environment on genetically identical mice.

By altering our response to medications and environmental chemicals, gut flora may in fact have non-ignorable effects on our behavior--not unlike "parasitic hairworm charming grasshopper into taking it for a swim".

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