Xiaokeping-induced autophagy protects pancreatic ß-cells against apoptosis under high glucose stress.

Xiaokeping (XKP), a prescribed Traditional Chinese Medicine (TCM), has been used to treat patients with type Ⅱ diabetes mellitus for many years; however, the molecular mechanism of its effects is unknown. As the only insulin producer, the pancreatic ß cell plays an important role in diabetes. Whether XKP influences the viability of pancreatic ß cells remains to be substantiated. In the present study, autophagy/apoptosis analyses were used to evaluate the therapeutic effect of XKP on pancreatic ß-cells induced by high glucose levels and to investigate a potential causal molecular mechanism of XKP effect on the cells. The pancreatic ß-cell lines MIN-6 were divided into four groups: control, high glucose (33.3 mmol/L), high glucose with XKP, high glucose with XKP and 3-Methyladenine (3-MA). Immunofluorescence assay was employed to determine autophagosome formation and flow cytometry was used to determine apoptotic rates of the ß cells by the detecting expression of autophagy- and apoptosis-related proteins. High glucose increased the apoptotic rate of ß-cells from 5.37% to 23.24%; however addition of XKP mitigated the rate at 10.92%. Data indicate that autophagy of ß-cells was induced by XKP via the mammalian target of rapamycin (mTOR) pathway. Where the autophagy inhibitor 3-MA was added, the apoptotic rate was 23.94%, similar to the high glucose group rate. The results suggest a potential cytoprotective effect of XKP from high glucose toxicity by its induction of autophagy which may be linked to mTOR-mediated autophagy.