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REVIEW OF THE EFFECTS OF OBESITY ON ALTERATIONS IN THE GUT MICROBIOME Shaneeta Johnson, Carolyn Moore*, Samy Bendjemil, Kayellen Umeakunne, Larry Hobson, Omar K. Danner Surgery, Morehouse School of Medicine, Atlanta, GA Obesity is widespread and has been associated with multiple co-morbid and obesity related diseases, including heart disease, diabetes mellitus and cancer3,4. Obesity has been discovered to be a chronic, low-grade inflammatory condition, the cause of which is multifactorial. The role of hormones, genetics, environment and a host of other factors have been evaluated in multiple studies. The purpose of this study is to investigate the effect of changes in obesity on alterations in the gut microbiota. Use of 16S rRNA gene sequencing has shown that the gut microbiota of obese individuals is distinctly different from lean individuals. Studies in lean and obese twins revealed obesity is associated with decreased microbial diversity, increased ratio of phylum level Firmicutes:Bacteriodetes and increased insulin resistance.5,6 Weight loss resulting from a fat or carbohydrate restricted diet causes a reduced Firmicutes:Bacteriodetes ratio in obese persons7. The role of the gut microbiota in obesity associated inflammation has been attributed to increased gut permeability to pathogenic bacteria through loss of mucosal barrier protective Bifidobacterium and resultant dysbiosis. Elevated levels of gram-negative gut bacterial derived lipopolysaccharide (LPS) are associated with inflammation. LPS binds to toll-like receptor 4 (TLR4), leading to responses, including pro-inflammatory molecules that interfere with modulation of glucose and insulin metabolism.8 We reviewed the current literature to determine the effect of obesity on the gut microbiome. A Pubmed search was performed using the keywords of obesity and gut micro biome. Twenty articles were reviewed to determine trends and associations in obesity and gut microbiota. Bariatric surgery has a significant effect on obesity including achieving weight loss in obese patients, reversing metabolic risk factors and improving diabetes through its modulation of gut peptides. Many studies have been conducted, which demonstrate significant changes in gut microbiota following bariatric surgery. Changes in gut microbiota following gastric bypass (RYGB) surgery have shown an increase in Gammaproteobacteria and decreases in Clostridia species. Verrucomicrobia has also been shown to be present in obese individuals but absent following RYGB.9 Comparison of the Bacteroides/Prevotella group pre-surgery and following bariatric surgery showed an increased ratio corresponding to the same level in lean controls. Furthermore, levels of Faecalibacterium prausnitzii in obese individuals increased following RYGB and negatively correlated with serum concentrations of inflammatory markers C-reactive protein and interlukin-6 suggesting an anti-inflammatory role for this bacteria10. These changes suggest that alterations in gut microbiota play an integral role in weight loss and reduced adiposity following RYGB surgery11.
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