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Hyperglycemia-induced pancreatic β-cell apoptosis causes serious health complications in diabetic patients. Recently, studies demonstrated that silk and silk-related materials have anti-diabetic effects. We previously reported that silk fibroin hydrolysate (SFH) has anti-diabetic effects through increased pancreatic β-cell mass in type 2 diabetic animals (C57BL/KsJdb/db). However, it is not known whether SFH has anti-apoptotic effects in hyperglycemic conditions. The present study investigates the anti-apoptotic effects of SFH on high glucose-induced apoptosis using RIN5F cells, a rat pancreatic β-cell line. Hyperglycemic conditions decreased RIN5F cell viability in a concentration-dependent manner. High glucose treatment of 33 mM or higher caused a significant decrease in RIN5F cell viability. However, addition of SFH significantly recovered cell viability in the presence of high glucose. Flow cytometry analysis showed that high glucose treatment significantly increased early stage apoptosis in RIN5F cells. This was inhibited by SFH treatment, which significantly decreased not only early stage apoptosis but also decreased the production of nitrite. Additionally, SFH protected RIN5F cells from oxidative stress-induced apoptosis. These results suggest that SFH has anti-apoptotic effects by protecting pancreatic β-cell from high glucose and/or oxidative stress. Our results supportin vivoanti-diabetic effects of SFH and validation of the traditional use of silkworm and silkworm materials in the treatment of diabetes. [ABSTRACT FROM AUTHOR]