Manipulating microbes potential alternative to weight loss surgery

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Changes in mucosal and fecal microbiomes reflected on gut metabolism after surgery corresponded to persistent changes in fecal fermentation and bile acid metabolism, both of which are associated with improved metabolic outcomes, according to new research published in the journal Biofilms and Microbiomes.

Already considered a global epidemic, human obesity continues to be on the rise. According to the Centers for Disease Control, more than 40 percent of the U.S. population is considered obese.

The adverse health effects associated with obesity are broad, including type 2 diabetes, coronary artery disease, stroke, sleep apnea and certain forms of cancer. Patients often suffer depression, loss of mobility, social isolation and inability to work. With costs approaching $316 billion dollars annually in the U.S., understanding how to quell obesity will result not only in a healthier population, but could also help reduce runaway medical costs, the researchers said.

Despite the looming need to address obesity, the causes are not well understood. Researchers generally agree that genetic and gut microbiome composition and activity are important factors in determining obesity. As interest and understanding of the human microbiome increases, researchers are increasingly looking to the gut for answers that can lead to new, more effective diagnostics and therapies.

The trillions of microbes in the human gut perform a vast range of critical functions in the body and have even been implicated in mood and behavior. Among microbes' critical responsibilities are the micro-management of nutrients in the food we digest, one of the reasons for their central role in the regulation of body weight.

In the study, researchers from the Mayo Clinic and Pacific Northwest National Laboratory found that in addition to the expected weight reduction and improvement in obesity-related comorbidities after gastric bypass surgery, the researchers observed that the impact of surgery is not limited to fecal communities; mucosal communities are altered as well. Changes in the microbiome were linked to increased concentrations of branched-chain fatty acids and an overall decrease in primary and secondary bile acid concentrations in fecal samples. Bile is an alkaline fluid that aids digestion.

Bariatric surgery is an operation that causes people to lose weight by making changes to the digestive system. These changes are physiological and chemical and include gastric restriction, malabsorption, bile acid metabolism, and chemical signaling.

Although gastric bypass surgery has been successful for many patients suffering from morbid obesity, it is a serious, invasive procedure that is not without risk and expense. In addition, some patients regain the weight they have lost, perhaps because they lack the favorable microbes necessary for permanent weight loss.

In the longitudinal study, subjects provided fecal samples and rectal mucosal samples. The rectal mucosal samples were collected via un-sedated flexible sigmoidoscopy at baseline, and again at 12 months post-gastric bypass surgery. Researchers analyzed microbial DNA that was extracted from the fecal and mucosal samples. Fecal metabolites were analyzed using high-throughput metabolomics approaches.

A tell-tale indicator of pathology in obese patients has been found in the gut, where a markedly lower diversity of microbial communities is observed. A high diversity of gut microbes is essential to good health. The researchers said future studies will look to quantify the contribution of the microbiome to the host energy balance.