A High-Fat Diet Attenuates AMPK α1 in Adipocytes to Induce Exosome Shedding and Nonalcoholic Fatty Liver Development In Vivo.

Abstract

Exosomes are important for intercellular communication, but the role of exosomes in the communication between adipose tissue (AT) and the liver remains unknown. The aim of this study is to determine the contribution of AT-derived exosomes in nonalcoholic fatty liver disease (NAFLD). Exosome components, liver fat content, and liver function were monitored in AT in mice fed a high-fat diet (HFD) or treated with metformin or GW4869 and with AMPKα1-floxed <i>(Prkaα1</i> ^fl/fl/wild-type [WT]), <i>Prkaα1</i> ^-/-, liver tissue-specific <i>Prkaα1</i> ^-/-, or AT-specific <i>Prkaα1</i> ^-/- modification. In cultured adipocytes and white AT, the absence of <i>AMPKα1</i> increased exosome release and exosomal proteins by elevating tumor susceptibility gene 101 (<i>TSG101</i>)-mediated exosome biogenesis. In adipocytes treated with palmitic acid, TSG101 facilitated scavenger receptor class B (CD36) sorting into exosomes. CD36-containing exosomes were then endocytosed by hepatocytes to induce lipid accumulation and inflammation. Consistently, an HFD induced more severe lipid accumulation and cell death in <i>Prkaα1</i> ^-/- and AT-specific <i>Prkaα1</i> ^-/- mice than in WT and liver-specific <i>Prkaα1</i> ^-/- mice. AMPK activation by metformin reduced adipocyte-mediated exosome release and mitigated fatty liver development in WT and liver-specific <i>Prkaα1</i> ^-/- mice. Moreover, administration of the exosome inhibitor GW4869 blocked exosome secretion and alleviated HFD-induced fatty livers in <i>Prkaα1</i> ^-/- and adipocyte-specific <i>Prkaα1</i> ^-/- mice. We conclude that HFD-mediated AMPKα1 inhibition promotes NAFLD by increasing numbers of AT CD36-containing exosomes.