Bacteria lie dormant in the human intestine that ensure the development of immune cells – and these in turn prevent the formation of fat cells. But a diet high in sugar can reduce the number of these microbes, as Yoshinaga Kawano from Columbia University in New York and his team describe in a recent study in the journal Cell. With experiments on mice, they have shown how nutrition, the intestinal microbiome and special immune cells are connected and protect against obesity and other metabolic diseases.
Metabolic syndrome encompasses several health conditions, such as high blood sugar or obesity, that combine to increase the risk of cardiovascular disease and diabetes. Kawano and his colleagues have now discovered that certain gut bacteria in mice help reduce risk factors for metabolic syndrome. The microbes ensure an increase in special T helper cells, the so-called TH17 cells. As the researchers discovered, these immune cells cause less fat to be absorbed in the intestine.
When the scientists fed the mice a diet high in fat and sugar, the beneficial bacteria in the gut were killed. However, microbiotic supplements prevented the mice from gaining weight or developing metabolic syndrome despite the high-fat, high-sugar diet. A closer look revealed how the obesity came about beforehand: the high sugar content promoted the growth of bacteria from the Erysipelotrichaceae family, which in turn killed the immune-regulating bacteria. When the mice stopped eating sugar, they stopped developing obesity and metabolic syndrome. However, only if the animals still have bacteria-produced TH17 cells.