Research over the last decade has considered the potential role of gut microbiota in the development of obesity and its related metabolic disorders. Although initial findings in mice showing the relevant contribution of gut microbiota to weight change have not been translated in a straightforward way in humans, scientists hypothesize that gut microbes may help us understand the effectiveness of weight-loss strategies such as diet and bariatric surgery.
Kaplan’s group experiments in mice were among the first to find that changes in gut microbiota composition could account for some of the weight loss that happens after a gastric bypass. Although it seems microbes work by allowing animals to burn more energy, how exactly an altered intestinal microbiota might cause weight loss and metabolic improvements remains to be seen.
New research in obese diabetic women shows that gut microbiota composition before Roux-en-Y gastric bypass is linked to postoperative type 2 diabetes remission.
The authors sought to explore to what extent metabolic benefits after Roux-en-Y gastric bypass (RYGB) are related to gut microbiota profile in obese diabetic women.
Anthropometric and body composition variables improved up until 12 months after surgery. More interestingly, preoperative gut bacteria composition at the genus level differed between patients with and without T2D remission after surgery (57% versus 43%). Total type 2 diabetes remission after RYGB (assessed according to American Diabetes Association criteria) was associated with specific gut microbiota signatures before surgery. Those microbiota changes consisted of lower levels of Asaccharobacter and Atopobium and higher levels of Gemella, Coprococcus, and Desulfovibrio.
Specifically, the preoperative abundance of 10 gut bacteria genera correlated with the type 2 diabetes remission status, showing good sensitivity and specificity.
According to Karina Al Assal, one of the study’s lead authors, “These findings show that we can predict who is going to remit T2D before the surgery using the gut microbiota profile as a biomarker. This signature, if confirmed, may enable the prediction of future remission state of T2DM”.
By contrast, postoperative changes in the relative abundance of gut bacteria and their richness were observed regardless of whether participants showed T2D remission or not.
The authors also reported some correlations between gut microbiota richness (defined as the number of species in fecal samples, without taking into account the abundance of each one) and food intake based on a 7-day record. For instance, before surgery, gut microbiota richness showed a positive correlation with fiber intake and inverse association with lipid intake, with the latter persisting until 12 months after surgery.
Although limited in sample and despite the quasi-experimental design of the study, these findings show that improvements in body and metabolic parameters secondary to RYGB surgery may be partly explained by gut microbiota composition.
Regarding how these findings might impact on clinically managing obesity in the foreseeable future, Karina Al Assal highlighted to GMFH editors via email that the study of gut bacteria signatures at the preoperative period in obese patients might pave the way for using gut microbiota as a marker to help clinicians when deciding on whether to recommend bariatric surgery. Likewise, based on associations found between gut bacteria and food intake, adding fibers and reducing lipid intake might improve the outcome of bariatric surgery.
Al Assal K, Prifti E, Belda E, et al. Gut microbiota profile of obese diabetic women submitted to Roux-en-Y gastric bypass and its association with food intake and postoperative diabetes remission. Nutrients. 2020; 12, 278. doi: 10.3390/nu1202278.