Imeglimin, a tetrahydrotriazine anti-hyperglycemic agent, is thought to have effects on mitochondrial function of the liver, skeletal muscle, and pancreatic β-cells. However, the molecular mechanisms of imeglimin action have been still unclear. Treatment of mouse islets with 1.0 mM imeglimin significantly increased insulin release in response to glucose (2.1-fold, p<0.01 at 11.1 mM glucose; 1.9-fold, p<0.05 at 16.7 mM glucose, compared to 3.9 mM glucose). Treatment with a combination of liraglutide (100 nM) and imeglimin did not show an additional increase in insulin secretion compared to the treatment with liraglutide alone. Liraglutide and imeglimin significantly increased EdU-incorporated proliferating β-cells in the islets under 11.1 mM glucose (1.02% in vehicle control; 2.21% in liraglutide, p<0.01 vs. vehicle; 1.46% in 1.0 mM imeglimin, p<0.01 vs. vehicle). Imeglimin prevented β-cell apoptosis induced by high glucose (32% of control in imeglimin, p<0.01; 57% of control in liraglutide, p=0.068). We conducted gene expression microarray analysis of islets treated with imeglimin under high glucose and some ER stress-related gene expression were altered by imeglimin. Then, we examined the effects of imeglimin on ER stress-induced β-cell apoptosis in mouse islets. Imeglimin significantly reduced β-cell apoptosis induced by thapsigargin at 5.6 mM glucose (29% of thapsigargin, p<0.01). Imeglimin further upregulated the expression of C/EBP homologous protein (CHOP) under thapsigargin treatment and tended to decrease phosphorylation of eIF2-α. We also confirmed that imeglimin improved β-cell apoptosis induced by high glucose or thapsigargin in human islets. Collectively, imeglimin prevented β-cell apoptosis induced by high glucose or thapsigargin, in addition to increase in insulin secretion and β-cell proliferation. Imeglimin seemed to regulate CHOP/GADD34-mediated dephosphorylation of eIF2-α to recover from translational inhibition.

Disclosure

J. Li: None. J. Shirakawa: None. Y. Togashi: None. Y. Terauchi: Advisory Panel; Self; AstraZeneca, Daiichi Sankyo Company, Limited, Eli Lilly and Company, Merck Sharp & Dohme Corp., Mitsubishi Tanabe Pharma Corporation, Novo Nordisk A/S, Sanofi. Research Support; Self; Daiichi Sankyo Company, Limited, Eli Lilly and Company, Merck Sharp & Dohme Corp., Novartis Pharmaceuticals Corporation, Novo Nordisk A/S, Ono Pharmaceutical Co., Ltd., Sanofi, Shionogi & Co., Ltd., Sumitomo Dainippon Pharma Co., Ltd. Speaker's Bureau; Self; Astellas Pharma Inc., AstraZeneca, Bayer Yakuhin, Ltd., Daiichi Sankyo Company, Limited, Eli Lilly and Company, Merck Sharp & Dohme Corp., Mitsubishi Tanabe Pharma Corporation, Novartis Pharmaceuticals Corporation, Novo Nordisk A/S, Ono Pharmaceutical Co., Ltd., Sanofi, Sanwa Kagaku Kenkyusho, Shionogi & Co., Ltd., Sumitomo Dainippon Pharma Co., Ltd.

Readers may use this article as long as the work is properly cited, the use is educational and not for profit, and the work is not altered. More information is available at http://www.diabetesjournals.org/content/license.