Anti-apoptotic effects of silk fibroin hydrolysate in RIN5F cell on high glucose condition

Abstract

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 (C 57 BL/KsJ db/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 glucoseinduced 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 support in vivo anti-diabetic effects of SFH and validation of the traditional use of silkworm and silkworm materials in the treatment of diabetes.

A Synergistic Insulinotropic Effect of Green Tea Extract and Pomegranate Extract With Rosiglitazone: Both in Vivo and in Vitro Experiment

“…Streptozotocin-induced diabetic rats [10][11][12] Diabetes was induced by intraperitoneal injection of streptozotocin (Sigma-Aldrich) (65 mg/kg body weight in 0.9% NaCl, pH 4.5) to rats fasted for 16 h. Their diabetic conditions were confirmed by the symptoms of polydipsia, polyuria, and a high fasting blood glucose concentration 72 h after injection of streptozotocin. Rats with a blood glucose level above15.0 mmol/L were considered to be diabetic and used in the experiment 14 days treatment with the 6a and 6b In vitro studies using RIN-5F cells [13][14][15] RIN-5F cells (rat pancreatic beta cell line) were routinely cultured in RPMI 1640 supplemented with 2 mM L-glutamine, 10 mM HEPES, 1 mM sodium pyruvate, 4.5 g/L glucose, 1.5 g/L sodium bicarbonate, and 10% fetal bovine serum. The cells were passaged 2-4 days before each experiment and plated in 24-well Nunclon multiwell plates (NUNC A/S, Denmark) at a density of 0.2 × 10 6 cells/well.…”