Blake J Cochran1, Radjesh J Bisoendial1, Liming Hou1, Elias N Glaros1, Jérémie Rossy1, Shane R Thomas1, Philip J Barter1, Kerry-Anne Rye2. 1. From the Lipid Research Group, Centre for Vascular Research (B.J.C., R.J.B., L.H., P.J.B., K.-A.R.) and Redox Cell Signaling Group, School of Medical Sciences (E.N.G., S.R.T.), University of New South Wales, Sydney, Australia; Lipid Research Group, Heart Research Institute, Sydney, Australia (B.J.C., R.J.B., L.H., P.J.B., K.-A.R.); Australian Centre for Nanomedicine, Sydney, Australia (J.R.); Immune Imaging, Centenary Institute, Sydney, Australia (R.J.B.); and Faculty of Medicine, University of Sydney, Sydney, Australia (P.J.B., K.-A.R.). 2. From the Lipid Research Group, Centre for Vascular Research (B.J.C., R.J.B., L.H., P.J.B., K.-A.R.) and Redox Cell Signaling Group, School of Medical Sciences (E.N.G., S.R.T.), University of New South Wales, Sydney, Australia; Lipid Research Group, Heart Research Institute, Sydney, Australia (B.J.C., R.J.B., L.H., P.J.B., K.-A.R.); Australian Centre for Nanomedicine, Sydney, Australia (J.R.); Immune Imaging, Centenary Institute, Sydney, Australia (R.J.B.); and Faculty of Medicine, University of Sydney, Sydney, Australia (P.J.B., K.-A.R.). k.rye@unsw.edu.au karye@ozemail.com.au.
Abstract
OBJECTIVE: Therapeutic interventions that increase plasma levels of high-density lipoproteins and apolipoprotein A-I (apoA-I) A-I, the major high-density lipoprotein apolipoprotein, improve glycemic control in people with type 2 diabetes mellitus. High-density lipoproteins and apoA-I also enhance insulin synthesis and secretion in isolated pancreatic islets and clonal β-cell lines. This study identifies the signaling pathways that mediate these effects. APPROACH AND RESULTS: Incubation with apoA-I increased cAMP accumulation in Ins-1E cells in a concentration-dependent manner. The increase in cAMP levels was inhibited by preincubating the cells with the cell-permeable, transmembrane adenylate cyclase inhibitor, 2'5' dideoxyadenosine, but not with KH7, which inhibits soluble adenylyl cyclases. Incubation of Ins-1E cells with apoA-I resulted in colocalization of ATP-binding cassette transporter A1 with the Gαs subunit of a heterotrimeric G-protein and a Gαs subunit-dependent increase in insulin secretion. Incubation of Ins-1E cells with apoA-I also increased protein kinase A phosphorylation and reduced the nuclear localization of forkhead box protein O1 (FoxO1). Preincubation of Ins-1E cells with the protein kinase A-specific inhibitors, H89 and PKI amide, prevented apoA-I from increasing insulin secretion and mediating the nuclear exclusion of FoxO1. Transfection of Ins-1E cells with a mutated FoxO1 that is restricted to the nucleus confirmed the requirement for FoxO1 nuclear exclusion by blocking insulin secretion in apoA-I-treated Ins-1E cells. ApoA-I also increased Irs1, Irs2, Ins1, Ins2, and Pdx1 mRNA levels. CONCLUSIONS: ApoA-I increases insulin synthesis and secretion via a heterotrimeric G-protein-cAMP-protein kinase A-FoxO1-dependent mechanism that involves transmembrane adenylyl cyclases and increased transcription of key insulin response and β-cell survival genes.
OBJECTIVE: Therapeutic interventions that increase plasma levels of high-density lipoproteins and apolipoprotein A-I (apoA-I) A-I, the major high-density lipoprotein apolipoprotein, improve glycemic control in people with type 2 diabetes mellitus. High-density lipoproteins and apoA-I also enhance insulin synthesis and secretion in isolated pancreatic islets and clonal β-cell lines. This study identifies the signaling pathways that mediate these effects. APPROACH AND RESULTS: Incubation with apoA-I increased cAMP accumulation in Ins-1E cells in a concentration-dependent manner. The increase in cAMP levels was inhibited by preincubating the cells with the cell-permeable, transmembrane adenylate cyclase inhibitor, 2'5' dideoxyadenosine, but not with KH7, which inhibits soluble adenylyl cyclases. Incubation of Ins-1E cells with apoA-I resulted in colocalization of ATP-binding cassette transporter A1 with the Gαs subunit of a heterotrimeric G-protein and a Gαs subunit-dependent increase in insulin secretion. Incubation of Ins-1E cells with apoA-I also increased protein kinase A phosphorylation and reduced the nuclear localization of forkhead box protein O1 (FoxO1). Preincubation of Ins-1E cells with the protein kinase A-specific inhibitors, H89 and PKI amide, prevented apoA-I from increasing insulin secretion and mediating the nuclear exclusion of FoxO1. Transfection of Ins-1E cells with a mutated FoxO1 that is restricted to the nucleus confirmed the requirement for FoxO1 nuclear exclusion by blocking insulin secretion in apoA-I-treated Ins-1E cells. ApoA-I also increased Irs1, Irs2, Ins1, Ins2, and Pdx1 mRNA levels. CONCLUSIONS:ApoA-I increases insulin synthesis and secretion via a heterotrimeric G-protein-cAMP-protein kinase A-FoxO1-dependent mechanism that involves transmembrane adenylyl cyclases and increased transcription of key insulin response and β-cell survival genes.
Authors: Marie-Claude Brulhart-Meynet; Aurélien Thomas; Jonathan Sidibé; Florian Visentin; Rodolphe Dusaulcy; Valérie Schwitzgebel; Zoltan Pataky; Jacques Philippe; Nicolas Vuilleumier; Richard W James; Yvan Gosmain; Miguel A Frias Journal: Physiol Rep Date: 2021-03