Hibiscus sabdariffa Linn. calyx extraction and Gallic acid improving cardiac diastolic dysfunction in high fat diet-STZ-induced type 2 diabetic rats

摘要

Objective: Cardiovascular disease one of the serious complications of chronic diabetes. We previously reported on the ability of roselle (Hibiscus sabdariffa Linn.) water extract (HS-WE) to improve vascular response in rats suffering from chronic diabetes. The objective of this study was to investigate the effects of HS-WE and gallic acid on ventricular function in high fat diet?streptozotocin (HFD-STZ)-induced Type 2 diabetic rats. Material and Methods: Male Sprague-Dawley rats were used. The normal control group was fed normal rat chow. Diabetic groups were fed a HFD for four weeks, followed by intraperitoneal injections of STZ 30 mg/kg. The diabetic rats were divided into five groups that were orally administered daily with distilled water, 50% propylene glycol, HS-WE (500?mg/kg), gallic acid (50 mg/kg), and metformin (200 mg/kg) for a further eight weeks. At the end of all treatments, the levels of fasting blood glucose (FBG), serum insulin, Homeostatic Model Assessment-Insulin Resistance (HOMA-IR), plasma and heart malondialdehyde (MDA), heart superoxide production and left ventricular function were determined. Results: Diabetic control rats showed significant increases in levels of FBG, HOMA-IR, MDA and superoxide production. In the left ventricular function examination, an increase in diastolic ventricular pressure (DVP) and a decrease in (-)dP/dt (p<0.05) were observed. Interestingly HS-WE and gallic acid treated groups had significant decreases in FBG, HOMA-IR, plasma MDA, heart MDA and heart superoxide production as well as a decrease in DVP and an increase in (-)dP/dt when compared to the diabetic control group (p<0.05). Conclusion: These results indicated that HS-WE and gallic acid improved diabetic induced diastolic dysfunction and this effect may have been mediated via their antioxidant activities.