'Gut Microbiome' Key to Obesity, Metabolism
Medscape Diabetes & Endocrinology, Karine Clement, MD, PhD, Jul 19, 2013
Good morning. I am Professor Karine Clement. I'm a professor of nutrition at the Institute of Cardiometabolism and Nutrition in Paris. I'm here at the American Diabetes Association (ADA) conference to tell you about gut microbiota, metabolism, and bariatric surgery.
You all know that there has been an increase in the morbid form of obesity worldwide. There is a specific tool to improve these patients' condition: bariatric surgery. Actually, there are different tools. One is purely restrictive, where you have a diminution of food intake, using either a banding ring or a sleeve gastrectomy. But one of the most popular tools in bariatric surgery uses not only a restrictive procedure but also a malabsorptive procedure; it's called gastric bypass, or Roux-en-Y, and it has been well shown to induce major and sustained weight loss. It improves a lot of cardiometabolic risks, and there is also an improvement in systemic and tissue inflammation. This procedure is not only very effective for patients by reducing their risk, but it also has helped us better understand the factors associated with the improvements from bariatric surgery -- not only metabolic factors and inflammatory factors, but other aspects as well.
Indeed, obesity is a very complex condition associated with many environmental factors and with our own biology. There is basically an interaction between multiple environmental factors and individual biology and genes. In fact, we have been surprised in the past year to determine that we have another genome that is based on the genes inside the gut: the gut microbiota, or gut microbiome.[1-3]
Gut microbiota change after bariatric surgery.[4,5] There is kind of a switch in the composition of bacteria as well as in bacterial genes. We followed 30 subjects before and after bariatric surgery and found that some bacterial species are associated with a change in metabolism, change in fat mass, change in leptin, and change in insulin.
Often, bacterial groups are associated with inflammatory factors, but we have demonstrated that only a part of this association depends on changing food intake. There are many factors that could explain this change in gut microbiota -- of course, calorie change per se -- but also the surgical procedure.
The question now, going further, is that if we have a person in a given context --with known environmental factors, his own biology and gut microbiota -- then what is the link between this clinical phenotype, tissue phenotype, and gut microbiome? There are growing data in the literature showing that, indeed, the specific gut microbiota profile could modify the host biology. But we have seen in a rodent model that, if you transfer the gut microbiota of an animal after surgery, you can actually mimic some of the effects found after bariatric surgery, such as an improvement of weight and metabolic conditions.
Now the challenge is to better understand this aspect, to understand how bariatric surgery works to improve metabolic condition. Is gut microbiota important in this context? We need more mechanistic studies to understand how this works. Thank you for your attention.