Lack of TRPM2 Impaired Insulin Secretion and Glucose Metabolisms in Mice
- Kunitoshi Uchida1,2,
- Katsuya Dezaki3,
- Boldbaatar Damdindorj3,
- Hitoshi Inada1,
- Tetsuya Shiuchi2,4,
- Yasuo Mori5,
- Toshihiko Yada3,6,
- Yasuhiko Minokoshi2,4 and
- Makoto Tominaga1,2
- 1Division of Cell Signaling, Okazaki Institute for Integrative Bioscience (National Institute for Physiological Sciences), National Institutes of Natural Sciences, Okazaki, Japan;
- 2Department of Physiological Sciences, The Graduate University for Advanced Studies, Okazaki, Japan;
- 3Division of Integrative Physiology, Department of Physiology, Jichi Medical University School of Medicine, Tochigi, Japan;
- 4Division of Endocrinology and Metabolism, National Institute for Physiological Sciences, Okazaki, Japan;
- 5Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Kyoto, Japan;
- 6Department of Developmental Physiology, Division of Adaptation Development, National Institute for Physiological Sciences, Okazaki, Japan.
- Corresponding author: Makoto Tominaga, .
OBJECTIVE TRPM2 is a Ca2+-permeable nonselective cation channel activated by adenosine dinucleotides. We previously demonstrated that TRPM2 is activated by coapplication of heat and intracellular cyclic adenosine 5′-diphosphoribose, which has been suggested to be involved in intracellular Ca2+ increase in immunocytes and pancreatic β-cells. To clarify the involvement of TRPM2 in insulin secretion, we analyzed TRPM2 knockout (TRPM2-KO) mice.
RESEARCH DESIGN AND METHODS Oral and intraperitoneal glucose tolerance tests (OGTT and IPGTT) were performed in TRPM2-KO and wild-type mice. We also measured cytosolic free Ca2+ in single pancreatic cells using fura-2 microfluorometry and insulin secretion from pancreatic islets.
RESULTS Basal blood glucose levels were higher in TRPM2-KO mice than in wild-type mice without any difference in plasma insulin levels. The OGTT and IPGTT demonstrated that blood glucose levels in TRPM2-KO mice were higher than those in wild-type mice, which was associated with an impairment in insulin secretion. In isolated β-cells, smaller intracellular Ca2+ increase was observed in response to high concentrations of glucose and incretin hormone in TRPM2-KO cells than in wild-type cells. Moreover, insulin secretion from the islets of TRPM2-KO mice in response to glucose and incretin hormone treatment was impaired, whereas the response to tolbutamide, an ATP-sensitive potassium channel inhibitor, was not different between the two groups.
CONCLUSIONS These results indicate that TRPM2 is involved in insulin secretion stimulated by glucose and that further potentiated by incretins. Thus, TRPM2 may be a new target for diabetes therapy.
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See accompanying commentary, p. 28.
- Received February 25, 2010.
- Accepted September 24, 2010.
- © 2011 by the American Diabetes Association.
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