Abstract
Gut microbiota has been shown to have an important influence on host health. The microbial composition of the human gut microbiota is modulated by diet and other lifestyle habits and it has been reported that microbial diversity is altered in obese people. Obesity is a worldwide health problem that negatively impacts the quality of life. Currently, the widespread treatment for obesity is bariatric surgery. Interestingly, gut microbiota has been shown to be a relevant factor in effective weight loss after bariatric surgery. Since that the human gut microbiota of normal subjects differs between geographic regions, it is possible that rearrangements of the gut microbiota in dysbiosis context are also region-specific. To better understand how gut microbiota contribute to obesity, this study compared the composition of the human gut microbiota of obese and lean people from six different regions and showed that the microbiota compositions in the context of obesity were specific to each studied geographic location. Furthermore, we analyzed the functional patterns using shotgun DNA metagenomic sequencing and compared the results with other obesity-related metagenomic studies, we observed that microbial contribution to functional pathways were country-specific. Nevertheless, our study showed that although microbial composition of obese patients was country-specific, the overall metabolic functions appeared to be the same between countries, indicating that different microbiota components contribute to similar metabolic outcomes to yield functional redundancy. Furthermore, we studied the microbiota functional changes of obese patients after bariatric surgery, by shotgun metagenomics sequencing and observed that changes in functional pathways were specific to the type of obesity treatment. In all, our study provides new insights into the differences and similarities of obese gut microbiota in relation to geographic location and obesity treatments.
Highlights
It has been established that the composition of human gut microbiota greatly influences human health (Carding et al, 2015, reviewed by Hall et al, 2017)
The composition and function of the human gut microbiota represent one of most important factors involved in obesity and its treatment (Ley et al, 2006; Tremaroli and Backhed, 2012; Karlsson et al, 2013; Le Chatelier et al, 2013; DammsMachado et al, 2015; Medina et al, 2017)
It has been previously established that the human gut microbiota displays pronounced differences between individuals residing in distinct geographic locations (Yatsunenko et al, 2012; Fujio-Vejar et al, 2017; Gupta et al, 2017)
Summary
It has been established that the composition of human gut microbiota greatly influences human health (Carding et al, 2015, reviewed by Hall et al, 2017). It has been originally observed that the relative abundance of Firmicutes and Bacteroidetes can be altered in obese patients, where an over-representation of Firmicutes is observed, in contrast to their lean counterparts (Ley et al, 2006; Turnbaugh et al, 2009; Million et al, 2012; Walters et al, 2014; Kasai et al, 2015; Haro et al, 2016) These taxonomic differences between lean and obese subjects may contribute to the development and perpetuation of obesity in several ways, including fat storage, regulation of energy metabolism, energy extraction from short chain fatty acids, increased low-grade inflammation and altered bile acid metabolism (Qin et al, 2012; Karlsson et al, 2013; Khan et al, 2016). Further research is required to unravel the exact role of gut microbiota composition in obesity context, and the factors, including geographical location, that may have an influence on differential microbial abundance and long-term patient outcome
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