Irisin, a Link among Fatty Liver Disease, Physical Inactivity and Insulin Resistance

Nonalcoholic fatty liver disease (NAFLD) is the most common cause of chronic liver disease in industrialized countries. The increasing prevalence of NAFLD mirrors the outbreak of obesity in western countries, highlighting the connection between these two conditions. Nevertheless, there is currently no specific pharmacotherapy for its treatment. Accepted management begins with weight loss and exercise. Moreover, exercise can provide metabolic benefits independently of weight loss. It is known how long-term aerobic training produces improvements in hepatic triglycerides, visceral adipose tissue and free fatty acids, even if there is no weight reduction. A recent study from Boström et al. unravels a potential molecular mechanism that may explain how exercise, independently of weight loss, can potentially improve metabolic parameters through a new messenger system (irisin) linking muscle and fat tissue. Irisin has been proposed to act as a hormone on subcutaneous white fat cells increasing energy expenditure by means of a program of brown-fat-like development. Moreover, it was also shown that irisin plasma concentration was higher in people who exercise, suggesting a molecular mechanism by which exercise may improve metabolism. The present systematic review is based on the possibility that irisin might represent a hypothetical connection between NAFLD pathogenesis and disease progression.