Perilipin‐2 promotes obesity and progressive fatty liver disease in mice through mechanistically distinct hepatocyte and extra‐hepatocyte actions

Key Points

Wild type mice as well as mice with hepatocyte‐specific or whole‐body deletions of perilipin‐2 (Plin2) were used to define hepatocyte and extra‐hepatocyte effects of altered cellular lipid storage on obesity and non‐alcoholic fatty liver disease (NAFLD) pathophysiology in a western‐diet (WD) model of these disorders. Extra‐hepatocyte actions of Plin2 are responsible for obesity, adipose inflammation, and glucose clearance abnormalities in WD‐fed mice. Hepatocyte and extra‐hepatic actions of Plin2 mediate fatty liver formation in WD‐fed mice through distinct mechanisms. Hepatocyte‐specific actions of Plin2 are primary mediators of immune cell infiltration and fibrotic injury in livers of obese mice.

Abstract

Non‐alcoholic fatty liver disease (NAFLD) is an obesity and insulin resistance related metabolic disorder with progressive pathology. Perilipin‐2 (Plin2), a ubiquitously expressed cytoplasmic lipid droplet scaffolding protein, is hypothesized to contribute to NAFLD in humans and rodent models through effects on cellular lipid metabolism. In this study, we delineate hepatocyte‐specific and extra‐hepatocyte Plin2 mechanisms regulating the effects of obesity and insulin resistance on NAFLD pathophysiology in mice fed an obesogenic western‐style diet (WD). Total Plin2 deletion (Plin2‐Null) fully protected WD‐fed mice from obesity, insulin resistance, adipose inflammation, steatohepatitis (NASH) and liver fibrosis found in WT animals. Hepatocyte specific Plin2 deletion (Plin2‐HepKO) largely protected against NASH and fibrosis and partially protected from steatosis in WD‐fed animals, but it did not protect against obesity, insulin resistance, or adipose inflammation. Significantly, total or hepatocyte specific Plin2 deletion impaired WD‐induced monocyte recruitment and pro‐inflammatory macrophage polarization found in livers of WT mice. Analyses of the molecular and cellular processes mediating steatosis, inflammation, and fibrosis identified differences in total and hepatocyte‐specific actions of Plin2 on the mechanisms promoting NAFLD pathophysiology. Our results demonstrate that hepatocyte‐specific actions of Plin2 are central to the initiation and pathological progression of NAFLD in obese and insulin resistant mice through effects on immune cell recruitment and fibrogenesis. Conversely, extra‐hepatocyte Plin2 actions promote NAFLD pathophysiology through effects on obesity, inflammation and insulin resistance. Our findings provide new insight into hepatocyte and extra‐hepatocyte mechanisms underlying NAFLD development and progression.

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