Mulberry leaf flavonoids protect against glucotoxicity-induced INS-1 cell apoptosis.

OBJECTIVE

To investigate the effect of mulberry leaf flavonoids (MLF) on apoptosis of pancreatic cells induced by high glucose.

METHODS

Long exposure to high glucose induces apoptosis of pancreatic β cells, which can lead to diabetes. In this study, we used the rat insulinoma cell line, INS-1. High glucose (33.3 mM) was used to establish a glucotoxicity model. The MTT assay was used to evaluate the MLF effect on cell viability. INS-1 cells were treated with various concentrations of MLF (125, 250 and 500 mg/L) for 24 h, and then stimulated with 5.5 or 33.3 mM glucose for 48 h. Then, the cell supernatants were collected for enzyme-linked immunosorbent assay to determine the level of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px), malondialdehyde (MDA), monocyte chemoattractant protein 1 (MCP-1), tumor necrosis factor a (TNF-α) and interleukin 6 (IL-6). Western blotting was used to determine the expression of Bcl-2, Bax, caspase-3 and Caspase-9. Cell apoptosis was measured by Annexin V-FITC/propidium iodide double staining and flow cytometry.

RESULTS

MLF (125-500 mg/L) improved cell viability. Furthermore, MLF (250 and 500 mg/L) inhibited apoptosis induced by high glucose. The anti-apoptosis effect of MLF was associated with increased SOD, CAT and GSH-Px expression, as well as reduced MDA levels in high-glucose-treated INS-1 cells. Moreover, MLF upregulated Bcl-2 expression, downregulated Bax expression, and reduced the expression of caspase-3 and Caspase-9. Finally, MLF decreased the secretion of inflammatory cytokines and insulin in high-glucose-induced INS-1 cells.

CONCLUSION

MLF is a potential therapeutic agent for preventing diabetes and related disorders.