PGC1A regulates the IRS1 IRS2 ratio during fasting to influence hepatic metabolism downstream of insulin

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 116; no. 10; pp. 4285 - 4290
• Main Authors: Besse-Patin, Aurèle, Jeromson, Stewart, Levesque-Damphousse, Philipa, Secco, Blandine, Laplante, Mathieu, Estall, Jennifer L.
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 05.03.2019
• Subjects: AKT protein; Animal models; Animals; Biological Sciences; Cyclic AMP Response Element-Binding Protein - metabolism; Diabetes; Diabetes mellitus; Diabetes mellitus (non-insulin dependent); Diabetes Mellitus, Type 2 - metabolism; Fasting; Fatty liver; Female; Gene expression; Gene Expression Regulation; Glucagon; Glucagon - metabolism; Gluconeogenesis; Glucose; Glucose - metabolism; Hepatocytes; Hepatocytes - metabolism; Homeostasis; Humans; Insulin; Insulin - metabolism; Insulin receptor substrate 1; Insulin Receptor Substrate Proteins - genetics; Insulin Receptor Substrate Proteins - metabolism; Insulin Resistance; Kinases; Liver; Liver - metabolism; Liver diseases; Liver Diseases - metabolism; Male; Metabolism; Mice; Models, Animal; Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha - genetics; Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha - metabolism; Proteins; Proto-Oncogene Proteins c-akt - metabolism; Signal Transduction; Signaling; Substrates; Transcription; PGC-1; Ppargc1a; fasting; liver; gluconeogenesis
• ISSN: 0027-8424; 1091-6490; 1091-6490
• DOI: 10.1073/pnas.1815150116

Precise modulation of hepatic glucose metabolism is crucial during the fasting and feeding cycle and is controlled by the actions of circulating insulin and glucagon. The insulin-signaling pathway requires insulin receptor substrate 1 (IRS1) and IRS2, which are found to be dysregulated in diabetes and obesity. The peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC1A) is a fasting-induced transcriptional coactivator. In nonalcoholic fatty liver disease and in patients with type 2 diabetes, low hepatic PGC1A levels are associated with insulin resistance. However, how PGC1A activity impacts the hepatic insulin-signaling pathway is still unclear. We used gain- and loss-of-function models in mouse primary hepatocytes and measured hepatocyte insulin response by gene and protein expression and ex vivo glucose production. We found that the PGC1A level determines the relative ratio of IRS1 and IRS2 in hepatocytes, impacting insulin receptor signaling via protein kinase B/AKT (AKT). PGC1A drove the expression of IRS2 downstream of glucagon signaling while simultaneously reducing IRS1 expression. We illustrate that glucagon- or PGC1A-induced IRS2 expression was dependent on cAMP Response Element Binding Protein activity and that this was essential for suppression of hepatocyte gluconeogenesis in response to insulin in vitro. We also show that increased hepatic PGC1A improves glucose homeostasis in vivo, revealing a counterregulatory role for PGC1A in repressing uncontrolled glucose production in response to insulin signaling. These data highlight a mechanism by which PGC1A plays dual roles in the control of gluconeogenesis during the fasting-to-fed transition through regulated balance between IRS1 and IRS2 expression.