Retinol-Binding Protein 4 and New Adipocytokines in Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) is one of the most prevalent causes of hepatic dysfunction and is highly correlated with components of the metabolic syndrome such as obesity, insulin resistance and type 2 diabetes. Among others, nutritional factors, physical inactivity, genetic variants and visceral obesity have been identified as risk parameters for NAFLD. The complex pathophysiology of fatty liver degeneration, however, and especially the interaction between hepatocytes and adipose tissue has not been completely elucidated. Furthermore, it is not entirely understood whether insulin resistance generates fatty liver disease or vice versa. Nevertheless, adipocytokines are likely to be involved in the pathogenesis of NAFLD since they are secreted not only from adipose tissue but also from the liver. For several adipocytokines such as leptin, adiponectin, tumor necrosis factor-alpha, retinol binding protein 4 (RBP4) or fetuin-A a crucial role in the development and progression of fatty liver disease has been suggested. It has been accepted that obesity is an independent risk factor for NAFLD. Dysregulation of adipocytokines may represent an important mechanism linking increased fat mass in obesity with the development of fatty liver disease. Here, we discuss the association of RBP4 and other recently discovered adipocytokines and their relation with NAFLD.