慢性高糖诱导的LDH活性增高引起NIT-1细胞胰岛素分泌缺陷

目的：探讨慢性高糖状态下NIT-1细胞乳酸脱氢酶-A（LDH—A）活性与胰岛素分泌的关系。方法：以高糖单独或与草氨酸钠（LDH-A竞争性抑制剂）、N-乙酰半胱氨酸（NAC）联合作用于NIT-1细胞，测定LDH-A表达与活性、乳酸、反应氧族（ROS）和胰岛素分泌的相关性。结果：慢性高糖作用可提高NIT-1细胞LDH-A表达与活性、乳酸水平，使胰岛素分泌受损；草氨酸钠作用可降低慢性高糖诱导的NIT-1细胞LDH-A活性和促进乳酸水平增高，改善细胞胰岛素分泌；此外，NAC作用引起的NIT-1细胞ROS水平下降伴随LDH-A活性、乳酸水平下降和胰岛素分泌改善。结论：慢性高糖诱导的LDH—A活性增高引起NIT-1细胞胰岛素分泌缺陷；ROS激活LDH—A可能是胰岛D细胞葡萄糖毒性的机制之一。

Increased LDH-A Activity Induced by Chronic Exposure to High Glucose Contributes to Insulin Secretory Defect in NIT-1 Cells

Objective： To investigate the relationship between lactate dehydrogenase-A （LDH-A） activity and insulin secretion under chronic high-glucose conditions in NIT-1 cells. Methods： NIT-1 cells were treated with high glucose in presence/absence of oxamate （a competitive inhibitor of LDH-A） or N-acetylcysteine （NAC）, LDH-A expression, activity, lactate production, reactive oxygen species （ROS）, and insulin secretion were examined. Results： Chronically high glucose levels enhanced LDH-A expression, activity, and lactate production, and impaired insulin secretion in NIT-1 cells. Treatment with oxamate diminished the elevation of LDH-A activity induced by high glucose levels, reduced lactate production, and im- proved the impaired insulin secretion from NIT-1 cells observed in the absence of inhibitor. In addition, the reduction in ROS levels by NAC occurred simultaneously with the inhibition of LDH-A activity, lactate production, and the improvement in insulin secretion of NIT-1 cells. Conclusion： The results of our study indicate that increased LDH-A activity induced by chronic exposure to high glucose contributes to insulin secretory defect in NIT-1 cells. LDH-A activated by ROS may be one of the mechanisms of beta-cell glucotoxicity.