Body mass index and gender influence luminal and mucosa-associated microbiota

The gut microbiota plays a crucial role in the functioning of the digestive tract and in harvesting energy from the diet. The gut microbial population is essential for metabolizing indigestible polysaccharides and in the absorption of short-chain fatty acids produced by bacterial fermentation and also plays a key role in the regulation of intestinal transit, thereby affecting the amount of energy absorbed from the diet. The gut microbiota consists of two separate microbial populations, the lumen-associated microbiota (LAM) and the mucosa-associated microbiota (MAM): a shift in these microbial populations may have more pronounced effects on host immunity and gut homeostasis.LAM and MAM microbial populations can show profound differences in their composition, since fecal microbiota is predominantly comprised of those microbes resident in the lumen (e.g. free-living or associated with undigested food matrices), both obscuring and not accurately reflecting the composition of the mucosal-associated microbiota, and fluctuating with changes in diet and luminal content. On the other hand, the mucosa-associated microbiota is believed to be relatively stable in individuals over the course of a lifetime. Stability is achieved, in part, through the ability of these microbes to attach to the mucosa and to establish a niche through biofilm formation and creation of selection pressures that prevent expansion of other microbial communities. From their intimate and stable association with the host, mucosa-associated microbes are likely to have important influences on host physiology in health and the development of disease.For the present study, 40 subjects, of whom 20 obese (BMI >30) and 20 controls (BMI <25) (10 males and 10 females per group) was recruited.The aims of this study were i) to compare mucosa-associated microbiota, by means of sigmoid brush during colonoscopy, with fecal microbiota using high throughout next generation sequencing (NGS) and ii) to evaluate possible host factors that could influence the microbial biodiversity in the two niches.