Gut microbiota and nonalcoholic fatty liver disease.

Recent evidence has linked obesity and the metabolic syndrome with gut dysbiota. The precise mechanisms underlying that association are not entirely understood; however, microbiota can enhance the extraction of energy from diet and regulate whole-body metabolism towards increased fatty acids uptake from adipose tissue and shift lipids metabolism from oxidation to de novo production. Obesity and high fat diet relate to a specific gut microbiota, which is enriched in Firmicutes and with less Bacterioidetes. Microbiota can also play a role in the development of hepatic steatosis, necroinflammation and fibrosis. In fact, some studies have shown an association between small intestinal bacterial overgrowth, increased intestinal permeability and nonalcoholic steatohepatitis (NASH). That association is, in part, due to increased endotoxinaemia and activation of the Toll-like receptor-4 signaling cascade. Preliminary data on probiotics suggest a potential role in NASH treatment, however randomized controlled clinical trials are still lacking.