Metformin Modulates GLP-1- and GIP-Mediated Intracellular Signaling under Normoglycemic Conditions


GLP-1 and GIP promote insulin secretion from pancreatic β-cells by inducing intracellular signals such as Ca2+ and cAMP. Metformin primarily acts by inhibiting glucogenesis in the liver and promoting glucose metabolism in the muscle. It is used as a concomitant drug with the incretin in the treatment of T2D. We focused on intracellular signals under various glucose concentrations and assessed the effects of metformin on incretin signaling in MIN6 β-cells. Metformin inhibited incretin-induced [Ca2+]i in the presence of 5.5 mM glucose but not 16.7 mM glucose. In accordance with low [Ca2+]i, insulin secretion from MIN6 cells declined, despite enhanced incretin-induced cAMP production. Abundant expressions of Adcy 6 and 9, which are negatively controlled by Ca2+ signals, were detected in MIN6 cells. Thus, increasing cAMP production was associated with the inhibition of Ca2+ mobilization by metformin. However, we show that metformin controls insulin secretion by inhibiting incretin-mediated [Ca2+]i under normoglycemic conditions.

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K. Shinmura, T. Negoro, S. Shimizu, G. Roncador, T. Hirano and Y. Nakano, "Metformin Modulates GLP-1- and GIP-Mediated Intracellular Signaling under Normoglycemic Conditions," Open Journal of Endocrine and Metabolic Diseases, Vol. 3 No. 7, 2013, pp. 263-270. doi: 10.4236/ojemd.2013.37036.

Conflicts of Interest

The authors declare no conflicts of interest.


[1] J. B. Clifford, M. R. C. Path and R. C. Turner, “Metformin,” New England Journal of Medicine, Vol. 334, No. 9, 1996, pp. 574-579.
[2] B. Viollet, B. Guigas, J. Leclerc, S. Hebrard, L. Lantier, R. Mounier, F. Andreelli and M. Foretz, “AMP-Activated Protein Kinase in the Regulation of Hepatic Energy Metabolism: From Physiology to Therapeutic Perspectives,” Acta Physiologica, Vol. 196, No. 1, 2009, pp. 81-98.
[3] D. G. Hardie, “Neither LKB1 nor AMPK Are the Direct Targets of Metformin,” Gastroenterology, Vol. 131, No. 3, 2006, p. 973.
[4] X. G. Da Silva, I. Leclerc, A. Varadi, T. Tsuboi, K. Moule and G. A. Rutter, “Role of AMP-Activated Protein Kinase in Glucose-Stimulated Insulin Secretion and Preproinsulin Gene Expression,” Biochemical Journal, Vol. 371, No. 3, 2003, pp. 761-774.
[5] L. L. Baggio and D. J. Drucker, “Biology of Incretins: GLP-1 and GIP,” Gastroenterology, Vol. 132, No. 6, 2007, pp. 2131-2157.
[6] B. Thorens, “Expression Cloning of the Pancreatic Cell Receptor for the Gluco-Incretin Hormone Glucagon-Like Peptide 1,” Proceeding of National Academy of Sciences USA, Vol. 89, No. 18, 1992, pp. 8641-8645.
[7] T. B. Usdin, E. Mezey, D. C. Button, M. J. Brownstein and T. I. Bonner, “Gastric Inhibitory Polypeptide Receptor, a Member of the Secretin-Vasoactive Intestinal Peptide Receptor Family, Is Widely Distributed in Peripheral Organs and the Brain,” Endocrinology, Vol. 133, No. 6, 1993, pp. 2861-2870.
[8] G. G. Holz, C. A. Leech, R. S. Heller, M. Castonguay and J. F. Habener, “cAMP-Dependent Mobilization of Intracellular Ca2+ Stores by Activation of Ryanodine Receptors in Pancreatic Beta-Cells,” Journal of Biological Chemistry, Vol. 274, No. 20, 1999, pp. 14147-14156.
[9] O. Dyachok and E. Gylfe, “Ca2+-Induced Ca2+ Release via Inositol 1,4,5-Trisphosphate Receptors Is Amplified by Protein Kinase A and Triggers Exocytosis in Pancreatic Beta-Cells,” Journal of Biological Chemistry, Vol. 279, No. 44, 2004, pp. 45455-45461.
[10] R. A. Miller, Q. Chu, J. Xie, M. Foretz, B. Viollet and M. J. Birnbaum, “Biguanides Suppress Hepatic Glucagon Signalling by Decreasing Production of Cyclic AMP,” Nature, Vol. 494, No. 7436, 2013, pp. 256-260.
[11] B. Hu, H. Nakata, C. Gu, T. DeBeer and D. M. Cooper, “A Critical Interplay between Ca2+ Inhibition and Activation by Mg2+ of AC5 Revealed by Mutants and Chimeric Constructs,” Journal of Biological Chemistry, Vol. 277, No. 36, 2002, pp. 33139-33147.
[12] J. L. Guillou, H. Nakata and D. M. Cooper, “Inhibition by Calcium of Mammalian Adenylyl Cyclases,” Journal of Biological Chemistry, Vol. 274, No. 50, 1999, pp. 35539-35545.
[13] N. Masada, A. Ciruela, D. A. Macdougall and D. M. Cooper, “Distinct Mechanisms of Regulation by Ca2+/ Calmodulin of Type 1 and 8 Adenylyl Cyclases Support Their Different Physiological Roles,” Journal of Biological Chemistry, Vol. 284, No. 7, 2009, pp. 4451-4463.
[14] C. Gu and D. M. Cooper, “Calmodulin-Binding Sites on Adenylyl Cyclase Type 8,” Journal of Biological Chemistry, Vol. 274, No. 12, 1999, pp. 8012-8021.
[15] G. Kang, O. G. Chepurny, M. J. Rindler, L. Collis, Z. Chepurny, W.-H. Li, M. Harbeck, M. W. Roe and G. G. Holz, “A cAMP and Ca2+ Coincidence Detector in Support of Ca2+-Induced Ca2+ Release in Mouse Pancreatic b Cells,” Journal of Physiology, Vol. 566, No. 1, 2005, pp. 173-188.
[16] N. Ozaki, T. Shibasaki, Y. Kashima, T. Miki, K. Takahashi, H. Ueno, Y. Sunaga, H. Yano, Y. Matsuura, T. Iwanaga, Y. Takai and S. Seino, “cAMP-GEF2 Is a Direct Target of cAMP in Regulated Exocytosis,” Nature Cell Biology, Vol. 2, No. 11, 2000, pp. 805-811.
[17] G. Kang, O. G. Chepurny and G. G. Holtz, “cAMP-Re-gulated Guanine Nucleotide Exchange Factor 2 (Epac2) Mediates Ca2+-Induced Ca2+ Release in INS-1 Pancreatic Cells,” Journal of Physiology, Vol. 536, No. 2, 2001, pp. 375-385.
[18] J. Miyazaki, K. Araki, E. Yamato, H. Ikegami, T. Asano, Y. Shibasaki, Y. Oka and K. Yamamura, “Establishment of a Pancreatic b Cell Line that Retains Glucose Inducible Insulin Secretion,” Endocrinology, Vol. 127, No. 1, 1990, pp. 126-132.
[19] T. Hiroi, T. Wajima, T. Negoro, M. Ishii, Y. Nakano, Y. Kiuchi, Y. Mori and S. Shimizu, “Neutrophil TRPM2 Channels Are Implicated in the Exacerbation of Myocardial Ischemia/Reperfusion Injury,” Cardiovascular Research, Vol. 97, No. 2, 2013, pp. 271-281.
[20] M. H. Sherman, A. I. Kuraishy, C. Deshpande, J. S. Hong, N. A. Cacalano, R. A. Gatti, J. P. Manis, M. A. Damore, M. Pelleqrini and M. A. Teitell, “AID-Induced Genotoxic Stress Promotes B Cell Differentiation in the Germinal Center via ATM and LKB1 Signaling,” Molecular Cell, Vol. 39, No. 6, 2010, pp. 873-885.
[21] J. Lu, J. Ji, H. Meng, D. Wang, B. Jiang, L. Liu, E. Randell, K. Adeli and Q. H. Meng, “The Protective Effect and Underlyin Mechanism of Metformin on Neointima Formation in Fructose-Induced Insulin Resistant Rats,” Cardiovascular Diabetology, Vol. 12, 2013, p. 58.
[22] Y. Ishibashi, T. Matsui, M. Takeuchi and S. Yamagishi, “Metformin Inhibits Advanced Glycation End Products (AGEs)-Induced Growth and VEGF Expression in MCF-7 Breast Cancer Cells by Suppressing AGEs Receptor Expression via AMP-Activated Protein Kinase,” Hormone and Metabolic Research, Vol. 45, No. 5, 2013, pp. 387-390.
[23] A. Maida, B. J. Lamont and C. D. Drucker, “Metformin Regulates the Incretin Receptor Axis via a Pathway Dependent on Peroxisome Proliferator-Activated Receptor in Mice,” Diabetologia, Vol. 54, No. 2, 2011, pp. 339-349.
[24] J. Selway, R. Rigatti, N. Storey, J. Lu, G. B. Willars and T. P. Herbert, “Evidence that Ca2+ within the Microdomain of the L-Typer Voltage Gated Ca2+ Channel Activates ERK in MIN6 Cells in Response to Glucagon-Like Peptide-1,” PLoS One, Vol. 7, No. 3, 2012, p. e33004.
[25] F. A. Antoni, A. A. Sosunov, A. Haunso, J. M. Paterson and J. Simpson, “Short-Term Plasticity of Cyclic Adenosine 3',5'-Monophosphate Signaling in Anterior Pituitary Corticotrope Cells: The Role of Adenylyl Cyclase Isotypes,” Molecular Endocrinology, Vol. 17, No. 4, 2003, pp. 692-703.
[26] T. Kitaguchi, O. Manami, Y. Wada, T. Tsuboi and A. Miyawaki, “Extracellular Calcium Influx Activates Adenylate Cyclase 1 and Insulin Secretion in MIN6 Cells,” Biochemical Journal, Vol. 450, No. 2, 2013, pp. 365-373.

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