Gut bacteria, pesticides and obesity

Although my interest in this blog centres on all things gut-related, within this huge area of research I am particularly interested in how our genetic makeup interacts with our environment and vice-versa. I suppose gastrointestinal (GI) conditions are ideally suited to this complex 'nature-nutrure' relationship as evidenced by conditions like coeliac (celiac) disease, the archetypal gene-environment condition.

An interesting paper has appeared by Hae-Sook Lee and colleagues* suggestive of an interesting 'threesome' between a species of methane gas producing microbe, organochlorine pesticides and obesity. The paper is open-access. A summary of the details:

• Fecal and blood samples from 83 Korean women were analysed alongside anthropometric (body mass index) measurements.
• Fecal levels of Methanobacteriales were quantified via qPCR and serum / fecal levels of various organochlorine pesticides (OCPs) were assayed via GC-MS among a selection of participants with detected or non-detected levels of Methanobacteriales.
• The results: Methanobacteriales were present in about a third of patient stool samples (27/83). Higher Methanobacteriales levels were present in women with a waist circumference above 83cm than below and showed some connection with elevated BMI also. Higher fecal levels of Methanobacteriales were also associated with higher serum levels of the OCPs.

We do need to take a step back from these findings before making too many associations. The sample population is quite small and the numbers of people included for analysis of OCPs for example is even smaller. Bear in mind that just looking at three primary variables is not necessarily grounds for a relationship.

I am however struck by the 'suggestion' that gut bacterial content and obesity might either increase the risk of greater take-up of compounds such as OCPs or that gut bacteria might interact with our chemical environment to potentially predispose to conditions such as obesity. This latter hypothesis: OCP levels determining Methanobacteriales levels which in turn leads to increases in anthropometric measures is the author's preferred interpretation.

The authors discuss the properties of OCPs as being central to the finding i.e. lipophilic (fat or oil loving) and also note that Methanobacteriales are quite often used to biodegrade hydrocarbons such as petroleum. I have to say I have never really thought about industrial waste management being applied to the human model but perhaps should not be so surprised given the current interest in things like industrial biodigestion.

What this study does more than anything is to reaffirm the complexity of conditions such as obesity as well as providing some new targets, environmental and biochemical, which we should perhaps be exploring with a little more assiduity.

* Hae-Sook Lee et al. Associations among organochlorine pesticides, Methanobacteriales, and obesity in Korean women. PLoS ONE. November 2011.