Hepatocyte SLC31A1-dependent copper accumulation contributes to hepatic glucose and lipid metabolic disturbances through AMPKα1 inactivation

Abstract

Hepatic insulin resistance and fat accumulation are common features of metabolic syndrome, obesity and type 2 diabetes (T2D). However, whether the copper importer SLC31A1 has a role in diabetes-associated hepatic metabolic disorders remains unknown. Thus, we studied the role of hepatocyte SLC31A1 in HFD/STZ-induced T2D mice and in glucosamine (GlcN)- or oleic acid-treated hepatocytes. Glucose homeostasis and insulin resistance were analysed by determination of blood glucose levels fasting and insulin levels, HOMA insulin resistance (HOMA-IR), intraperitoneal glucose tolerance test (IPGTT) and insulin tolerance test (ITT). Hepatic SLC31A1 expression and accumulation of copper were enhanced in T2D mice with altered expression of cuproptosis-associated genes. Hepatocyte-specific SLC31A1 knockdown improved glucose tolerance and insulin resistance, decrease hepatic gluconeogenesis, restore hepatic glycogen accumulation and attenuate hepatic steatosis, oxidative stress, inflammation and liver injury in mice. Consistently, SLC31A1 knockdown decreased GlcN-mediated gluconeogenesis and glycogen depletion and reduced oleic acid-mediated accumulation of hepatic triglyceride in HepG2 cells. Mechanistically, SLC31A1 knockdown exclusively restored AMPKα1 phosphorylation in metabolically stressed hepatocytes, and genetic AMPKα1 depletion partly rescued the effect of SLC31A1 knockdown on glucose production and TG accumulation. Pharmacological inhibition of AMPK partially abolished the effect of SLC31A1 downregulation in T2D mice. Collectively, hepatocyte SLC31A1 upregulation caused hepatic copper accumulation and contributed to hepatic metabolic dysfunction, at least in part, through inhibition of AMPKα1 signaling.