Gastrointestinal bacteria in obesity and type 2 diabetes : a review of current knowledge

Abstract

The gastrointestinal tract is home to over 10 bacteria that collectively form the intestinal microbiome, and their joint genetic repertoire is larger than the human genome.These symbiotic bacteria establish and maintain the gut immune system, and contribute to the breakdown of complex nondigestible plant-derived polysaccharides. The relatively recent technological advances in genomics have revolutionized the study of the intestinal microbiome. It is now possible to sequence mixed microbial genetic material directly extracted from environmental samples without prior laboratory culture of individual species. This emerging field, known as metagenomics, enables a survey of the different microorganisms present in a specific environment. Several large-scale projects such as the Human Microbiome Initiative have characterized microbial genomes from hundreds of isolated human symbionts and have shed light on the complex interplay between the human host and its microbial populace, and how this changes in health and disease. This article aims to discuss the emerging body of knowledge that links the gut microbiome to the development of obesity and metabolic disease. The growing prevalence of overweight and obesity are easily linked to the sedentary lifestyles and caloriedense diets typical of ‘Westernized’ countries.