Human gut microbiota in obesity and after gastric bypass

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 106; no. 7; pp. 2365 - 2370
• Main Authors: Zhang, Husen, DiBaise, John K, Zuccolo, Andrea, Kudrna, Dave, Braidotti, Michele, Yu, Yeisoo, Parameswaran, Prathap, Crowell, Michael D, Wing, Rod, Rittmann, Bruce E, Krajmalnik-Brown, Rosa
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 17.02.2009; National Acad Sciences
• Subjects: Adult; Archaea; Archaea - metabolism; Bacteria; Bacteroidetes; Biological Sciences; Body Mass Index; community ecology; community structure; Digestive system; Female; Firmicutes; Gastric bypass; Gastric Bypass - adverse effects; Gastrointestinal surgery; genes; Genetics; Humans; intestinal microorganisms; intestines; Intestines - metabolism; Intestines - microbiology; large intestine; Male; Methanogens; Microbiota; Middle Aged; Models, Biological; Molecular Sequence Data; Obesity; Obesity - microbiology; Obesity - pathology; Obesity - surgery; polymerase chain reaction; Postoperative Complications; ribosomal RNA; RNA, Ribosomal, 16S - chemistry; rRNA genes; Sequence Analysis, DNA; species diversity; Studies; surgery; Weight loss
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.0812600106

Recent evidence suggests that the microbial community in the human intestine may play an important role in the pathogenesis of obesity. We examined 184,094 sequences of microbial 16S rRNA genes from PCR amplicons by using the 454 pyrosequencing technology to compare the microbial community structures of 9 individuals, 3 in each of the categories of normal weight, morbidly obese, and post-gastric-bypass surgery. Phylogenetic analysis demonstrated that although the Bacteria in the human intestinal community were highly diverse, they fell mainly into 6 bacterial divisions that had distinct differences in the 3 study groups. Specifically, Firmicutes were dominant in normal-weight and obese individuals but significantly decreased in post-gastric-bypass individuals, who had a proportional increase of GAMMAPROTEOBACTERIA: Numbers of the H₂-producing Prevotellaceae were highly enriched in the obese individuals. Unlike the highly diverse Bacteria, the Archaea comprised mainly members of the order Methanobacteriales, which are H₂-oxidizing methanogens. Using real-time PCR, we detected significantly higher numbers of H₂-utilizing methanogenic Archaea in obese individuals than in normal-weight or post-gastric-bypass individuals. The coexistence of H₂-producing bacteria with relatively high numbers of H₂-utilizing methanogenic Archaea in the gastrointestinal tract of obese individuals leads to the hypothesis that interspecies H₂ transfer between bacterial and archaeal species is an important mechanism for increasing energy uptake by the human large intestine in obese persons. The large bacterial population shift seen in the post-gastric-bypass individuals may reflect the double impact of the gut alteration caused by the surgical procedure and the consequent changes in food ingestion and digestion.