Study of Mammalian gut microbe interactions in obesity

Abstract

Obesity in general can be defined as the condition of abnormal or excessive fat accumulation by the body, to an extent that health may be impaired. World over 1.6 billion adults are overweight and 400 million adults are obese (World Health Organization 2005). Genetic basis of this outbreak is well disputed, as the human genome is substantially unchanged over decades. The recent discovery of association of gut bacteria with fat storage and obesity has been a milestone in the field of human physiology. Obese gut microbiome exhibits an enhanced efficiency to harvest energy from diet; furthermore, this phenomenon is demonstrated to be transmissible. Weight loss program in obese humans induces a comparative increase in bacteria of phylum Bacteroidetes with significant reduction in phylum Firmicutes, although, researchers failed to see such an observation in another community. Bariatric surgery is one of the majorly sought remedies for morbid obesity. SG (Sleeve gastrectomy) and AGB (Adjustable gastric banding) are two forms of restrictive bariatric surgery, which reduce the effective volume of stomach leading to early satiety and reduced caloric intake without affecting absorption of the digested food. However, the effects of SG and AGB on gut microbiota are not well studied and such a comparison could assist to unveil a discrete relationship between obesity and gut bacteria. Furthermore, a comparison of gut microbiota of lean individuals with that of normal, obese, and surgically-treated individuals could substantiate the association of gut microbiota with obesity. In this study, analysis and comparison of 16S rRNA gene libraries based fecal microbiota from lean (n=5), normal (n=5), obese (n=5), and treated-obese (SG and AGB, n=5) individuals is presented. The data (approximately, total 3000 sequences) demonstrates that every individual has a unique and personalized microbiota, dominated by the bacteria of Phyla, Bacteroidetes and Firmicutes. At phylum level, Firmicutes seem to correlate with BMI (P<0.05). Obese individuals exhibit an increased prevalence of bacteria of genus, Bacteroides and domain, archaea, whereas among the treated-obese individuals these are significantly reduced.