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Surgery and gut microbiome

Bariatric surgery benefits gut microbiome for a decade

The outcomes could lead to the exploration of probiotics as an alternative to weight-loss surgery

Roux-en-Y gastric bypass and vertical banded gastroplasty result in similar microbiome remodelling changes that are maintained almost a decade later in a group of women, according to a study published in Cell Metabolism. The outcomes show that microbiome changes are specific to the surgery and not just a reflection of altered weight changes (BMI), which paves the way for the exploration of probiotics as an alternative to weight-loss surgery.

Fredrik Bäckhed of the University of Gothenburg in Sweden and his colleagues examined the gut bacteria of 14 women over nine years after they underwent Roux-en-Y gastric bypass or vertical banded gastroplasty. Despite the differences in surgery procedures, the two weight-loss procedures had similar and long-lasting changes on the gut microbiome.

These effects were then shown to be transferable. When "germ-free" mice (which are bred to be free of all gut bacteria) were treated with stool samples from patients who underwent surgery, the animals were able to better metabolize fat via oxidation or breakdown and put on significantly less fat compared to mice colonised with stool from obese individuals.

Women who had undergone gastric bypass surgery had more significant differences in the composition of their gut bacteria than the women with severe obesity who had not had surgery. For example, bacteria belonging to the genuses Escherichia, Klebsiella and Pseudomonas were more abundant in women who had undergone gastric bypass than in those who had not had surgery.

This visual abstract depicts how two types of bariatric surgery, Roux-en-Y gastric bypass and vertical banded gastroplasty, produce long-term alterations of the gut microbiome independently of BMI and that these alterations modulate host metabolism and fat mass deposition. Credit: Tremaroli and Karlsson et al./Cell Metabolism 2015

The women who'd had vertical banded gastroplasty also showed differences in their gut bacteria compared to the women who had not had the surgery, but these differences were not statistically significant, meaning they could have been due to chance, the researchers said.

Although the two surgical procedures might result in different functionality due to different intestinal environmental conditions, the changes in the microbiome were not dependent on BMI or degree of weight and fat mass loss, thus revealing shifts in the gut microbiota that were specific to bariatric surgery.

When the researchers transferred bacteria from the patients into the mice that were specially raised to not have their own gut bacteria, they found that the mice that were given bacteria from the patients who had undergone bariatric surgery had differences in metabolism and put on less fat compared to mice that received gut bacteria from obese patients. The mice that received bacteria from the gastric bypass patients put on 43 percent less body fat, and the mice that received bacteria from vertical banded gastroplasty patients put on 26 percent less body fat, compared with the mice that received bacteria from obese patients who had not had weight-loss surgery.

The results concur with previous research that found changes in gut bacteria following bariatric surgery, but this study is one of the first to look at whether those changes last over the long term, according to the researchers.

However, because the new study was small, the findings should be confirmed with future research. The study's small size may have limited the researchers' ability to detect certain differences between the groups, they said. In addition, the study did not compare the gut bacteria of the same women before and after surgery, which would have provided stronger evidence of a change in gut bacteria.

"Our findings are important in light of the growing epidemic of obesity and associated diseases," Bäckhed says. "Since surgery always confers a risk, it is critical to identify non-surgical strategies. One potential strategy would be to devise novel probiotics based on our findings that can be supplied to obese individuals."

To access this paper, please click here

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