OBJECTIVE The glucoincretin hormone glucagon-like peptide 1 (GLP-1) enhances glucose-stimulated insulin

OBJECTIVE The glucoincretin hormone glucagon-like peptide 1 (GLP-1) enhances glucose-stimulated insulin secretion and stimulates pancreatic -cell mass expansion. ratio and SirT1 expression in INS cells and isolated islets, offering feasible systems simply by which usually XL647 GLP-1 can modulate SirT1 activity thereby. Finally, the actions of GLP-1 on -cell mass development can be removed in both transgenic rodents and cultured -cells with improved dose of SirT1. Results Our research displays for the 1st period that the glucoincretin hormone GLP-1 modulates SirT1 activity and FoxO1 acetylation in -cells. We identify SirT1 as a adverse regulator of KAT3B -cell expansion also. The glucoincretin hormone glucagon-like peptide 1-[7C36]amide (GLP-1) (1C3) can be a powerful restorative agent in the treatment of diabetes (4). GLP-1 boosts insulin release in topics with reduced blood sugar threshold and type 2 diabetes (5). It also stimulates insulin gene appearance and insulin biosynthesis (6), in component via improved activity and appearance of the -cellCspecific transcription element (7,8). Furthermore, GLP-1 offers been demonstrated to promote -cell mass development in both fresh pet versions (8,9) and cultured -cells (7,10C14). Nevertheless, the molecular system by which GLP-1 exerts its actions can be not really completely elucidated. We possess previously demonstrated that GLP-1 transactivates the skin growth factor receptor (12) to subsequently activate phosphatidylinositol-3 kinase and Akt signaling (7,11). Activation of epidermal growth factor receptor/phosphatidylinositol-3 kinase/Akt signaling by GLP-1 stimulates -cell proliferation (7,11) and survival (13,14). Of interest, this signaling pathway has been suggested to play a role in the glucoincretin effect of GLP-1 as well (15). We have also demonstrated that the forkhead transcription factor FoxO1, an important regulator of -cell mass (16C18), is a prominent transcriptional effector of GLP-1 action in -cells (10). Thus, GLP-1 inhibits FoxO1 via Akt-mediated phosphorylation and nuclear exclusion. Inhibition of FoxO1 by GLP-1 increases both Pdx1 and Foxa2 expression and triggers -cell mass expansion (10). FoxO1 activity is regulated in a complex fashion by various posttranslational modifications, including reversible Ser-Thr phosphorylation and Lys acetylation (19). Acetylation at Lys-242, -245, and -262 of FoxO1 attenuates its ability to bind cognate DNA sequence and increases its susceptibility to phosphorylation by Akt (20). Conversely, deacetylation of FoxO1 by the NAD+-dependent protein deacetylase SirT1 increases its transcriptional activity (21C23). We therefore sought to test the possible implication of SirT1 in GLP-1 action. The current study shows that GLP-1 stunts SirT1-mediated FoxO1 deacetylation, thereby relieving a molecular brake on -cell mass expansion. Our work describes a novel mechanism for GLP-1 action. It also identifies SirT1 as a negative regulator of -cell proliferation. RESEARCH DESIGN AND METHODS Reagents. Human GLP-1 fragment 7C36 amide, exendin-4, nicotinamide, and resveratrol were obtained from Sigma (St. Louis, MO). RPMI-1640 medium, FCS, XL647 and other culture media were bought from Invitrogen (Burlington, ON, Canada). Anti-FKHR antibody was bought from Cell Signaling (Beverly, MA). Antiacetyl-lysine and anti-SirT1 antibodies had been acquired from Millipore XL647 (Bedford, MA). AntiCguinea-pig insulin was bought from Sigma. Cell tradition. Inches832/13 cells (24) had been expanded in RPMI-1640 moderate supplemented with 10 mmol/D HEPES, 10% heat-inactivated FCS, 2 mmol/D l-glutamine, 1 mmol/D salt pyruvate, 50 mol/D -mercaptoethanol, 100 IU/mL penicillin, and 100 g/mL streptomycin at 37C in a humidified 5% Company2 atmosphere. Cells at 70% confluence had been cleaned with phosphate-buffered saline and preincubated in serum-free RPMI-1640 moderate supplemented with 3 mmol/D blood sugar and 0.1% BSA (Sigma) for at least 4 h before treatment. This condition mimics calorie limitation and was demonstrated to activate SirT1. Islet remoteness. Rat islets had been separated from male Wistar rodents (250 g) by collagenase digestive function. Islets were purified more than a Histopaque lean and handpicked under a microscope subsequently. Human being islets had been separated from body organ contributor at the Division of Medical procedures, Montreal General Medical center, McGill College or university Wellness Middle, Montreal, Quebec, canada ,, Canada (three distinct contributor were received). Human ethics approval was obtained through the McGill University Health Center ethics committee. Donors were between ages 42 and 65, and none had a history of diabetes or metabolic disorder. Islets were isolated by digestion with Liberase CI (Boehringer Mannheim, Indianapolis, IN) followed by.