Adiponectin: A multitasking player in the field of liver diseases

Adiponectin is the most abundant adipokine synthesized by adipose tissue and has been shown to be a key component in the relationship between adiposity, insulin resistance and inflammation. It circulates in plasma at physiological concentrations that represent 0.05% of all plasma proteins. Adiponectin has trimeric, hexameric and multimeric forms that bind to receptors AdipoR1, AdipoR2 and T-cadherin especially in liver, muscle and endothelial cells. Adiponectin is considered a potent modulator of lipid and glucose metabolism with antidiabetic, antiatherogenic and anti-inflammatory properties, and plays an important role in the pathogenesis of metabolic diseases. The hepatoprotective effects of adiponectin, especially in non-alcoholic fatty liver disease (NAFLD), have been widely investigated, and its antisteatotic, anti-inflammatory and antifibrogenic effects have already been described. Adiponectin levels are reduced in individuals with fatty liver disease independently of body mass index, insulin resistance and other adipokines, and are inversely related to the severity of steatosis and necroinflammation, suggesting an important role in the relationship between adipose tissue, the liver and insulin sensitivity. Adiponectin has also been found to be reduced in cases of hepatitis B and C infection, and in cholestatic and autoimmune diseases, but is increased in patients with cirrhosis of different aetiologies. In addition, an important role for the liver in the regulation of adiponectin secretion by adipocytes, mediated by bile acids, has recently been proposed. The present report describes the importance of adiponectin in hepatic diseases as well as some future perspectives of the role of adiponectin as a biomarker and therapeutic target in liver diseases.