Vitamin B6 Inhibits High Glucose-Induced Islet β Cell Apoptosis by Upregulating Autophagy

Abstract

Vitamin B6 may alleviate diabetes by regulating insulin secretion and increasing insulin sensitivity, but its mechanism remains to be explored. In this study, vitamin B6-mediated autophagy and high glucose-induced apoptosis were tested to investigate the mechanism by which vitamin B6 regulates insulin release. The results showed that 20 mM glucose increased the apoptosis rate from 10.39% to 22.44%. Vitamin B6 reduced the apoptosis rate of RIN-m5F cells from 22.44% to 11.31%. Our data also showed that the vitamin B6 content in processed eggs was decreased and that the hydrothermal process did not affect the bioactivity of vitamin B6. Vitamin B6 increased the number of autophagosomes and the ratio of autophagosome marker protein microtubule associated protein 1 light chain 3 beta to microtubule associated protein 1 light chain 3 alpha (LC3-II/LC3-I). It also decreased the amount of sequetosome 1 (SQSTM1/p62) and inhibited the phosphorylation of p70 ribosomal protein S6 kinase (p70S6K) under normal and high glucose stress. Another study showed that vitamin B6 inhibited the apoptosis rate, whereas the autophagy inhibitor 3-methyladenine (3-MA) blocked the protective effect of vitamin B6 against apoptosis induced by high glucose. The hydrothermal process decreased the vitamin B6 content in eggs but had no effect on the cytoprotective function of vitamin B6 in RIN-m5f cells. In conclusion, we demonstrated that vitamin B6-mediated autophagy protected RIN-m5f cells from high glucose-induced apoptosis might via the mTOR-dependent pathway. Our data also suggest that low temperatures and short-term hydrothermal processes are beneficial for dietary eggs.