Nonalcoholic fatty liver disease (NAFLD) and steatohepatitis (NASH) are liver manifestations of the metabolic syndrome and can progress to hepatocellular carcinoma (HCC). Loss of growth hormone (GH) signaling is reported to predispose to NAFLD and NASH through direct actions on the liver. Here, we report that aged mice lacking hepatocyte Jak2 (JAK2L), an obligate transducer of GH signaling, spontaneously develop the full spectrum of phenotypes found in patients with metabolic liver disease, beginning with insulin resistance and lipodystrophy and manifesting as NAFLD, NASH, and even HCC, independent of dietary intervention. Remarkably, insulin resistance, metabolic liver disease, and carcinogenesis are prevented in JAK2L mice via concomitant deletion of adipocyte Jak2. Further, we demonstrate that GH increases hepatic lipid burden but does so indirectly via signaling through adipocyte JAK2. Collectively, these data establish adipocytes as the mediator of GH-induced metabolic liver disease and carcinogenesis. In addition, we report what we believe to be a new spontaneous model of NAFLD, NASH, and HCC that recapitulates the natural sequelae of human insulin resistance–associated disease progression. The work presented here suggests that attention be paid to inhibition of adipocyte GH signaling as a therapeutic target of metabolic liver disease.
Kevin C. Corbit, Camella G. Wilson, Dylan Lowe, Jennifer L. Tran, Nicholas B. Vera, Michelle Clasquin, Aras N. Mattis, Ethan J. Weiss