A Membrane-Bound Diacylglycerol Species Induces PKCϵ-Mediated Hepatic Insulin Resistance

• Published in: Cell metabolism 2020-10, Vol.32 (4), p.654-664.e5
• Main Authors: Lyu, Kun, Zhang, Ye, Zhang, Dongyan, Kahn, Mario, ter Horst, Kasper W., Rodrigues, Marcos R.S., Gaspar, Rafael C., Hirabara, Sandro M., Luukkonen, Panu K., Lee, Seohyuk, Bhanot, Sanjay, Rinehart, Jesse, Blume, Niels, Rasch, Morten Grønbech, Serlie, Mireille J., Bogan, Jonathan S., Cline, Gary W., Samuel, Varman T., Shulman, Gerald I.
• Format: Article
• Language: English
• Subjects: ceramides; dicylglycerols; hepatic glucose production; hepatic glycogen synthesis; hepatic insulin resistance; insulin receptor phosphorylation; liquid chromatography-tandem mass spectrometry; nonalcoholic fatty liver disease; protein kinase C-epsilon; type 2 diabetes
• ISSN: 1550-4131; 1932-7420
• DOI: 10.1016/j.cmet.2020.08.001

Nonalcoholic fatty liver disease is strongly associated with hepatic insulin resistance (HIR); however, the key lipid species and molecular mechanisms linking these conditions are widely debated. We developed a subcellular fractionation method to quantify diacylglycerol (DAG) stereoisomers and ceramides in the endoplasmic reticulum (ER), mitochondria, plasma membrane (PM), lipid droplets, and cytosol. Acute knockdown (KD) of diacylglycerol acyltransferase-2 in liver induced HIR in rats. This was due to PM sn-1,2-DAG accumulation, which promoted PKCϵ activation and insulin receptor kinase (IRK)-T1160 phosphorylation, resulting in decreased IRK-Y1162 phosphorylation. Liver PM sn-1,2-DAG content and IRK-T1160 phosphorylation were also higher in humans with HIR. In rats, liver-specific PKCϵ KD ameliorated high-fat diet-induced HIR by lowering IRK-T1160 phosphorylation, while liver-specific overexpression of constitutively active PKCϵ-induced HIR by promoting IRK-T1160 phosphorylation. These data identify PM sn-1,2-DAGs as the key pool of lipids that activate PKCϵ and that hepatic PKCϵ is both necessary and sufficient in mediating HIR. [Display omitted] •Plasma membrane-bound sn-1,2-diacylglycerols cause hepatic insulin resistance•PKCϵ is necessary and sufficient for mediating lipid-induced hepatic insulin resistance•PKCϵ promotes hepatic insulin resistance via phosphorylating insulin receptor Thr1160•Ceramides do not consistently track with hepatic insulin resistance Lipid-induced hepatic insulin resistance is mediated by plasma membrane-bound sn-1,2-diacylglycerols, which promote PKCϵ translocation to the plasma membrane. PKCϵ is both necessary and sufficient for mediating lipid-induced hepatic insulin resistance through phosphorylation of insulin receptor at Thr1160.