Xiwen Xiong1, Gaihong Wang1, Rongya Tao1, Pengfei Wu2, Tatsuyoshi Kono3, Kevin Li4, Wen-Xing Ding4, Xin Tong3,5, Sarah A Tersey6, Robert A Harris1,2, Raghavendra G Mirmira6, Carmella Evans-Molina2,3,5, X Charlie Dong7. 1. Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, 635 Barnhill Drive, MS1021D, Indianapolis, IN, 46202, USA. 2. Richard Roudebush Veterans Affairs Medical Center, Indianapolis, IN, USA. 3. Department of Medicine, Indiana University School of Medicine, Indianapolis, IN, USA. 4. Department of Pharmacology, Toxicology and Therapeutics, University of Kansas Medical Center, Kansas City, KS, USA. 5. Department of Cellular and Integrative Physiology, Indiana University School of Medicine, Indianapolis, IN, USA. 6. Department of Pediatrics, Indiana University School of Medicine, Indianapolis, IN, USA. 7. Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, 635 Barnhill Drive, MS1021D, Indianapolis, IN, 46202, USA. xcdong@iu.edu.
Abstract
AIMS/HYPOTHESIS: Sirtuin 6 (SIRT6) has been implicated in ageing, DNA repair and metabolism; however, its function in pancreatic beta cells is unclear. The aim of this study is to elucidate the role of SIRT6 in pancreatic beta cells. METHODS: To investigate the function of SIRT6 in pancreatic beta cells, we performed Sirt6 gene knockdown in MIN6 cells and generated pancreatic- and beta cell-specific Sirt6 knockout mice. Islet morphology and glucose-stimulated insulin secretion (GSIS) were analysed. Glycolysis and oxygen consumption rates in SIRT6-deficient beta cells were measured. Cytosolic calcium was monitored using the Fura-2-AM fluorescent probe (Invitrogen, Grand Island, NY, USA). Mitochondria were analysed by immunoblots and electron microscopy. RESULTS: Sirt6 knockdown in MIN6 beta cells led to a significant decrease in GSIS. Pancreatic beta cell Sirt6 knockout mice showed a ~50% decrease in GSIS. The knockout mouse islets had lower ATP levels compared with the wild-type controls. Mitochondrial oxygen consumption rates were significantly decreased in the SIRT6-deficient beta cells. Cytosolic calcium dynamics in response to glucose or potassium chloride were attenuated in the Sirt6 knockout islets. Numbers of damaged mitochondria were increased and mitochondrial complex levels were decreased in the SIRT6-deficient islets. CONCLUSIONS/ INTERPRETATION: These data suggest that SIRT6 is important for GSIS from pancreatic beta cells and activation of SIRT6 may be useful to improve insulin secretion in diabetes.
AIMS/HYPOTHESIS: Sirtuin 6 (SIRT6) has been implicated in ageing, DNA repair and metabolism; however, its function in pancreatic beta cells is unclear. The aim of this study is to elucidate the role of SIRT6 in pancreatic beta cells. METHODS: To investigate the function of SIRT6 in pancreatic beta cells, we performed Sirt6 gene knockdown in MIN6 cells and generated pancreatic- and beta cell-specific Sirt6 knockout mice. Islet morphology and glucose-stimulated insulin secretion (GSIS) were analysed. Glycolysis and oxygen consumption rates in SIRT6-deficient beta cells were measured. Cytosolic calcium was monitored using the Fura-2-AM fluorescent probe (Invitrogen, Grand Island, NY, USA). Mitochondria were analysed by immunoblots and electron microscopy. RESULTS:Sirt6 knockdown in MIN6 beta cells led to a significant decrease in GSIS. Pancreatic beta cell Sirt6 knockout mice showed a ~50% decrease in GSIS. The knockout mouse islets had lower ATP levels compared with the wild-type controls. Mitochondrial oxygen consumption rates were significantly decreased in the SIRT6-deficient beta cells. Cytosolic calcium dynamics in response to glucose or potassium chloride were attenuated in the Sirt6 knockout islets. Numbers of damaged mitochondria were increased and mitochondrial complex levels were decreased in the SIRT6-deficient islets. CONCLUSIONS/ INTERPRETATION: These data suggest that SIRT6 is important for GSIS from pancreatic beta cells and activation of SIRT6 may be useful to improve insulin secretion in diabetes.
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