The purpose of this study was to investigate the protective properties and mechanisms of wax apple (Syzygium samarangense (Blume)) against streptozotocin (STZ)-induced pancreatic ß-cell apoptosis in diabetic rats. Diabetes was induced by STZ (65 mg/kg; i.p.) injection and wax apple (100 mg/kg) was orally administered to diabetic rats for a period of 30 days. During this time, fasting blood glucose (FBG) and body weight were measured weekly. At the end of the experiment, serum insulin, HOMA-B, and pancreatic insulin expression were assessed. The expression of apoptosis-related proteins along with the nitrotyrosine level, antioxidant activities, and pro-inflammatory cytokine TNF-α in the pancreas were also determined. STZ-induced diabetic rats exhibited an increase in FBG, and a decrease in body weight, serum and pancreatic insulin, as well as HOMA-B. Pancreatic apoptosis was noted in diabetic rats and indicated by enhancing the expression of cleaved caspase-3 and Bax proteins and downregulating the expression of Bcl-2 and Bcl-xl proteins. The activities of antioxidant CAT and SOD in the pancreas of the diabetic rats was also reduced. Importantly, wax apple treatment resulted in a significant reduction of FBG and increased body weight in diabetic rats. Wax apple also improved pancreatic ß-cell function, this was clearly evidenced by increased HOMA-B and pancreatic and serum insulin levels in diabetic rats. Moreover, pancreatic ß-cell apoptosis was alleviated with significantly down-regulated cleaved caspase-3 and Bax protein expression, and upregulated Bcl-2 and Bcl-xl protein expression in wax apple treated diabetic rats. These were related to the induction of CAT and SOD activities, and reduction of nitrotyrosine and TNF-α levels in wax apple administration. Overall, these results provide evidence that wax apple protects against STZ-induced pancreatic β-apoptosis and dysfunction in diabetic rats, possibly through inhibiting oxidative stress and pro-inflammatory cytokine, and activating anti-apoptotic proteins.

Worarat Rojanaverawong, Navinee Wongmanee, and Wanthanee Hanchang. Prev Nutr Food Sci 2023;28:30-42. https://doi.org/10.3746/pnf.2023.28.1.30

The purpose of the study was to investigate the anti-hyperglycemic effect of extra virgin sacha inchi oil (EVSIO) and its possible mechanisms and actions against pancreatic β-cell death and dysfunction in type 2 diabetic (T2D) rats. T2D rats were induced with a high-fat diet and low-dose of streptozotocin. The rats were then treated for 5 weeks with EVSIO (0.5, 1, and 2 ml/kg), or pioglitazone. Biochemical and histopathological studies, oxidative and inflammatory markers, and expression of apoptotic-related proteins were then evaluated. EVSIO treatment exhibited a dose-dependent reduction of fasting blood glucose, area under the curve of glucose, total cholesterol, and triglyceride levels in the diabetic rats, while improved pancreatic β-function was demonstrated by increasing pancreatic and serum insulin levels. EVSIO treatment effectively lowered atrophic pancreatic islets and reduced the level of serum and pancreatic MDA in the diabetic rats. In addition to serum and pancreatic GPx activities in the diabetic rats, EVSIO also augmented serum SOD. Increased levels of NF-κB, TNF-α and IL-6 present in the diabetic rats were greatly reduced by EVSIO treatment. Furthermore, EVSIO revealed an anti-apoptotic effect on the diabetic rat pancreas by upregulating Bcl-2, and downregulating Bax and cleaved caspase-3 protein expression. The overall study results demonstrated the potential anti-hyperglycemic effect of EVSIO in the diabetic rats. The beneficial effects of EVSIO may be attributed to its ability to improve pancreatic β-cell function and ameliorate β-cell apoptosis by inhibiting oxidative stress and inflammatory cytokines.