Role of lipid droplet proteins in liver steatosis.

Five proteins of the perilipin (Plin) family such as Plin1 (perilipin) Plin2 (adipose differentiation-related protein), Plin3 (tail-interacting protein of 47 kDa), Plin4 (S3-12), and Plin5 (myocardial lipid droplet protein) are characterized as lipid droplet (LD) proteins in adipocytes. Recent reports have demonstrated that fat-specific protein 27 (FSP27) and hypoxia-inducible protein 2 (HIG2) are also thought to be novel LD proteins in addition to proteins of the Plin family. Growing evidence have shown that LD proteins play a role in the pathophysiology in the fatty liver disease which is characterized by hepatocytes containing LD with excessive neutral lipid. Studies showed LD proteins such as Plin1, Plin2, Plin3, Plin5, FSP27, and HIG2 are expressed in the liver steatosis. Among them, a high fat diet increases expression of Plin2 and/or FSP27 through activation of peroxisome proliferator-activated receptor γ to develop fatty liver. In this article, recent advances on the role of LD proteins in pathophysiology of fatty liver diseases are summarized.