Switch to Anaerobic Glucose Metabolism with NADH Accumulation in the β-Cell Model of Mitochondrial Diabetes

• Published in: The Journal of biological chemistry Vol. 277; no. 44; p. 41817
• Main Authors: Mitsuhiko Noda, Shigeo Yamashita, Noriko Takahashi, Kazuhiro Eto, Lin-Ming Shen, Kazuo Izumi, Samira Daniel, Yoshiharu Tsubamoto, Tomomi Nemoto, Masamitsu Iino, Haruo Kasai, Geoffrey W. G. Sharp, Takashi Kadowaki
• Format: Journal Article
• Language: English
• Published: American Society for Biochemistry and Molecular Biology 01.11.2002
• DOI: 10.1074/jbc.M207690200
• ISSN: 0021-9258

To elucidate the mechanism underlying diabetes caused by mitochondrial gene mutations, we created a model by applying 0.4 μg/ml ethidium bromide (EtBr) to the murine pancreatic β cell line βHC9; in this model, transcription of mitochondrial DNA, but not that of nuclear DNA, was suppressed in association with impairment of glucose-stimulated insulin release (Hayakawa, T., Noda, M., Yasuda, K., Yorifuji, H., Taniguchi, S., Miwa, I., Sakura, H., Terauchi, Y., Hayashi, J.-I., Sharp, G. W. G., Kanazawa, Y., Akanuma, Y., Yazaki, Y., and Kadowaki, T. (1998) J. Biol. Chem. 273, 20300–20307). To elucidate fully the metabolism-secretion coupling in these cells, we measured glucose oxidation, utilization, and lactate production. We also evaluated NADH autofluorescence in βHC9 cells using two-photon excitation laser microscopy. In addition, we recorded the membrane potential and determined the ATP and ADP contents of the cells. The results indicated 22.2 m m glucose oxidation to be severely decreased by EtBr treatment compared with control cells (by 63% on day 4 and by 78% on day 6; both p < 0.01). By contrast, glucose utilization was only marginally decreased. Lactate production under 22.2 m m glucose was increased by 2.9- and 3.5-fold by EtBr treatment on days 4 and 6, respectively (both p < 0.01). Cellular NADH at 2.8 m m glucose was increased by 35 and 43% by EtBr on days 4 and 6 (both p < 0.01). These data suggest that reduced expression of the mitochondrial electron transport system causes NADH accumulation in β cells, thereby halting the tricarboxylic acid cycle on one hand, and on the other hand facilitating anaerobic glucose metabolism. Glucose-induced insulin secretion was lost rapidly along with the EtBr treatment with concomitant losses of membrane potential depolarization and the [Ca 2+ ] i increase, whereas glibenclamide-induced changes persisted. This is the first report to demonstrate the connection between metabolic alteration of electron transport system and that of tricarboxylic acid cycle and its impact on insulin secretion.