Autophagy plays beneficial effect on diabetic encephalopathy in type 2 diabetes: studies in vivo and in vitro.

OBJECTIVES: The hypothalamus regulates metabolism and feeding behavior by perceiving the levels of peripheral insulin. However, little is known about the hypothalamic changes after aberrant metabolism. In this study, we investigated the changes of insulin and autophagy relevant signals of hypothalamus under diabetes mellitus.

METHODS: C57B/L mice were injected with low-dose streptozotocin (STZ) and fed with high-fat diet to induce type 2 diabetes mellitus. In vitro, PC12 cells were treated with oleic acid to mimic lipotoxicity.

RESULTS: Results showed that the cholesterol level in the hypothalamus of the diabetic mice was higher than that of the normal mice. The expression of insulin receptors and insulin receptor substrate-1 were downregulated and the number of Fluoro-Jade C positive cells significantly increased in the hypothalamic arcuate nucleus of the diabetic mice. Furthermore, Upregulation of mammalian target of rapamycin (mTOR) and downregulation of LC 3II were obvious in the hypothalamus of the diabetic mice. In vitro, results showed that high-lipid caused PC12 cell damage and upregulated LC3 II expression. Pretreatment of cells with 3-methyladenine evidently downregulated LC3 II expression and aggravated PC12 cell death under high lipid conditions. By contrast, pretreatment of cells with rapamycin upregulated LC3 II expression and ameliorated PC12 cell death caused by lipotoxicity.

CONCLUSION: These results demonstrate that autophagy activation confers protection to neurons under aberrant metabolism and that autophagy dysfunction in the hypothalamus occurs in the chronic metabolic disorder such as T2DM.