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Aim: This study was designed to evaluate the effects of SGLT2 inhibitor on palmitate-induced lipotoxicity of cardiomyocytes and the underlying mechanism involved with palmitate. Methods: We checked SGLT2 expression in muscle cells, including H9C2. H9C2 cells were palmitate treated with/without SGLT2 inhibitor. Then, insulin resistance was measured, 2-NBDG uptake, and immunoblotting using insulin signaling pathway antibodies. Inflammation and cardiac metabolism were analyzed several related genes. Cardiomyocyte apoptosis was also detected using DNA fragmentations assay and immunoblotting using cleaved caspase 3. Results: Low doses of palmitates evoked lipotoxicity in cardiomyocytes. Treatment of SGLT2 inhibitor dramatically reduced palmitate-induced expression levels of inflammatory cytokines. Immunoblotting analysis showed treatment of cardiomyocytes, with SGLT2 inhibitor, recovered impaired insulin signaling, such as phospho-IR and phospho-AKT, but total IR and AKT did not change. SGLT2 inhibitor also restored insulin-stimulated glucose uptake, which was destroyed by lipotoxicity. Treatment with SGLT2 inhibitor decreased the level of ER stress markers as well as inflammatory signaling markers. In particular, SGLT2 inhibitor stimulated phosphorylation of AMPK and fatty acid beta-oxidation. Cardiomyocyte exposure to high doses of palmitates evoked apoptotic features such as caspase 3 activation and DNA fragmentations. But pretreatment of SGLT2 inhibitor significantly protected palmitate-induced apoptotic features. Conclusions: This data suggests SGLT2 inhibitors protect palmitate-induced cardiomyocytes inflammation, impaired cardiac metabolism, insulin resistance, and cardiomyocyte apoptosis. Therefore, attempts to use treatment of SGLT2 inhibitor might be a useful strategy for preventing diabetes-associated ventricular remodeling and diabetic cardiac complication. Disclosure H. Lee: None. S. Choi: None. Y. Kang: None. T. Kim: None. N. Lee: None. H. Moon: None. S. Han: None. D. Kim: None. K. Lee: None.

Aim/Hypotheses: Iron plays an important role in many physiological processes, including redox balance, inflammation, and mitochondrial respiratory metabolism. Abnormalities in iron metabolism lead to insulin resistance as well as diabetes. However, the abnormal mechanism of iron metabolism in the muscles of insulin resistance animal models is not precisely well known. Therefore, we investigated the molecular mechanism underlying iron dysregulation in high fat diet-induced C57BL/6J mice skeletal muscles. Methods: We measured intracellular iron content in skeletal muscle tissues and iron metabolism related protein levels, such as transferrin receptor1, heavy chain ferritin, light chain ferritin, DMT1, and ferroportin. To investigate the association between iron content and insulin resistance, we treated iron donor or chelator in an animal model and performed insulin tolerance tests and measurement of insulin signaling. Results: Interestingly, intracellular iron levels were increased in high fat diet-induced mice skeletal muscles. We also observed up-regulation of transferrin receptor 1 (TfR1), ferritin, but did not observe a change of DMT1 and ferroportin. Treatment with iron dextran, an iron donor, in C57BL/6J normal mice induced insulin resistance. However, treatment of desferrioxamine, an iron chelator, in high fat diet-induced insulin resistance mice recovered insulin resistance. Iron overload with iron dextran impaired insulin signaling in skeletal muscles, while iron chelation with desferrioxamine recovered high fat-induced dysregulated insulin signaling. Conclusions/interpretation: Therefore, we consider fine-tuning of skeletal muscle iron levels and highly suggest the use for preventing and/or treating insulin resistance and diabetes. Disclosure S. Choi: None. N. Lee: None. H. Moon: None. H. Kim: None. J. Jeon: None. Y. Kang: None. T. Kim: None. K. Lee: None.

Aim: In this study, we investigated the relationship and molecular mechanisms between iron-overload and ER-stress-induced insulin resistance in human skeletal muscle cells. Methods: Intracellular iron was measured using calcein AM. Iron metabolism-related genes were analyzed by immunoblotting and PCR. The study was conducted using iron supplementation, which was achieved by palmitate, FeSO4 and FeCl3 administration, and iron reduction, which occurred by DFO, DS and Bapta AM administration, and knockdown of tfR1 or IRP2 genes, to investigate the effects of iron metabolism on insulin sensitivity in HSMMs. Intracellular calcium was detected using Fluo-3/AM staining. TfR1 internalization regulated by calcium was detected by GFP-labelled transferrin. Results: Endoplasmic reticulum stress by tunicamycin, thapsigargin, or palmitate evoked insulin resistance and simultaneously increased intracellular iron. Iron chelator, DFO, dramatically prevented ER-stress inducer-induced insulin resistance and iron donor impaired insulin sensitivity in vitro and in vivo through activation of JNK. Among several iron metabolism-related genes, tfR1 plays a predominant role for maintaining iron homeostasis in HSMMs. Treatment of ER-stress inducer positively regulated translocation of tfR1 by intracellular calcium, but protein levels of tfR1 did not change. Iron reduction, by adding iron chelator, calcium chelator, or knockdown of tfR1 or IRP2, dramatically prevented ER-stress-induced insulin resistance through the reduction of iron-overload. Conclusions/Interpretation: The current study shows ER-stress inducer evoked insulin resistance through iron overload. Reduction of intracellular iron, by iron chelator, significantly prevents insulin resistance. Therefore, attempts to block iron overload might be a strategy for preventing insulin resistance and diabetes. Disclosure K. Lee: None. R. Cui: None. D. Kim: None. S. Choi: None. W. Lee: None. Y. Kang: None. T. Kim: None. H. Moon: None. J. Jeon: None. S. Han: None. H. Kim: None.

GAD is a pancreatic beta-cell autoantigen in humans and nonobese diabetic (NOD) mice. Modulation of GAD expression in pancreatic beta-cells has been suggested to be associated with the development of autoimmune diabetes. Hormonal changes through environmental stimuli are considered to influence the expression of the disease. We determined whether steroid hormones would modulate the expression of GAD in pancreatic beta-cells. We treated NOD mouse beta-cells (MIN6N8a cells) with various steroids, including testosterone, estradiol, progesterone, and cortisol, and examined the expression of GAD67 mRNA. We found that only cortisol enhanced the expression of GAD67, whereas the other steroid hormones had no effect. When we treated MIN6N8a cells with a synthetic glucocorticoid, dexamethasone, we found that GAD67 mRNA expression was stimulated in a dose- and time-dependent manner. Cells treated with 100 nmol/l dexamethasone for 6 h showed a 10-fold increase in the expression of GAD67 mRNA and an increase in GAD67 protein. The upregulation of GAD67 expression in beta-cells by dexamethasone was found to be due to the transcriptional activation of the GAD67 promoter. We then examined whether dexamethasone would influence the development of diabetes in NOD mice. Injection of dexamethasone into neonatal NOD mice resulted in a significant increase in the expression of GAD67 mRNA in pancreatic beta-cells and the development of insulitis and diabetes. We conclude that glucocorticoid hormones can modulate GAD expression by the transcriptional activation of the GAD promoter and may influence the development of autoimmune diabetes in NOD mice.