Gastric bypass surgery and the ever expanding world of GxE interactions

All opinions are my own and do not necessarily reflect those of Novo Nordisk.

An early publication article from the Proceedings of the National Academy of Sciences reports the fascinating finding that children born to mothers before and after gastric bypass surgery show differences in the expression of  genes involved in, among other things, glucose metabolism and immune function.  The study is small, with only 50 children evenly split between cohorts born to moms before and after gastric bypass, but if it replicates, it’s another piece of evidence  showing how the environment influences the way our genes function.

Epigenetics has been a hot topic in genetics research for a while now.  It’s clear that DNA methylation changes over time and within an individual and can affect gene expression.  Studies in a number of institutions such as Washington State University in the lab of Michael Skinner have shown that changes can even persist through multiple generations (in rats, at least).  The PNAS report adds another twist in that the gene by environment interaction arose due to a change in maternal health induced by surgery.

There are a lot of implications to this, including the rather theoretical one of whether this knowledge would induce more potential mothers to undergo gastric bypass surgery, and also practical ones of whether weight loss alone without surgery or via, for example, a lap band, would have the same effect.  But the one I wonder about is what this might imply for drug development.

While many genetic variations are known to affect disease risk and progression, and drug metabolism, there has been considerable debate on how to use such data.  In many cases, such as with the majority of Genome Wide Association Study hits, the relative risk of discovered variants have been statistically significant but small.  However, as we have seen with Amgen’s purchase of DeCode, drug development companies are keen to use genetic information to help inform their drug development efforts, to find an edge.

In this PNAS report, however, I see a flag of caution.  I applaud the efforts of Amgen and other companies taking these risks, but this report of possible epigenetic effects following maternal surgery also points out how much we’re still discovering about basic human biology, how much we still don’t know about the diseases we study.  Understanding Gene by Environment interactions is, I think, one of the key factors we deal with in developing drugs, and not one to ignore.  And yet, it feels currently like one of those “unknown knowns,” the things we willfully decide not to think about, even though we know it’s there.

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