Beschreibung:
Since several years, the gut microbiota is not considered as just a mass of bacteria anymore. Instead, it is now considered as an organ", influencing the host. Even though the presence or absence of specific bacteria has been associated with some homeostasis or diseases, the monumental number of different bacteria makes it difficult to reduce the role of the microbiota to those few bacteria. Hence, to understand how the microbiota interacts with the host is a key to explain its influence. One of the ways is the production of metabolites. The main metabolites produced by different bacteria are the Short-Chain Fatty Acids (SCFA), derived from microbial fermentation of dietary fibers. Those SCFA are known to modulate immune responses of the host, both locally and systemically. Furthermore, it is known that the immune system has a tight relationship with the bone, directly affecting it. For example, via the Tregs, the immune system can inhibit the differentiation of osteoclasts, decreasing the bone destruction. Therefore the question of the effect of SCFA on the bone rose. It appeared that the SCFA act directly as regulators of osteoclast metabolism, either in vitro and in vivo, without affecting the osteoblasts. Because of that, SCFA treatment or a diet rich in fibers, increasing the production of SCFA by the gut microbiota, are increasing the bone mass of mice. Contrarily, an increased presence of Prevotella copri in the gut decreases the production of SCFA by the microbiota, leading to a decrease of the bone mass. The SCFA also prevents pathological bone loss, either post-menopausal or due to inflammatory arthritis. Mechanistically, propionate and butyrate induce metabolic reprogramming of osteoclasts resulting in enhanced glycolysis at the expense of oxidative phosphorylation, thereby downregulating essential osteoclastic genes and inhibiting osteoclastogenesis. In summary, these data identify SCFA as potent regulators of osteoclast metabolism and bone homeostasis. As consequence, a therapeutic supplementation ..."