Renal and metabolic effects of tulbaghia violacea harv. and captopril in fructose-fed streptozotocin induced diabetic rats.

Abstract

Background: Diabetes mellitus has rapidly emerged as a worldwide epidemic resulting in significant morbidity and mortality. The incidence of type 2 diabetes mellitus, induced by a high carbohydrate diet, a sedentary lifestyle as well as obesity, is increasing rapidly. Despite the availability of current conventional drugs, the complications of diabetes mellitus continue to progress. Therefore the search for alternate therapies that are antidiabetic in nature and elicit minimal side effects is essential. This study investigated the effects of the medicinal plant Tulbaghia violacea. Harv and angiotensin converting enzyme inhibitor, Captopril in a fructose-fed streptozotocin induced diabetic rat model. Methods: Thirty-six, male Sprague-Dawley rats (six-week old) were randomly divided into six groups’ namely non-diabetic control, diabetic control, diabetic treated with Tulbaghia violacea Harv. (60 mg/kg bw), diabetic treated with captopril (50 mg/kg bw), diabetic treated with metformin (250 mg/kg bw) and diabetic treated with glibenclamide (10 mg/kg bw). Diabetes was induced by fructose feeding for 1 week followed by a single intraperitoneal injection of 40 mg/kg.bw streptozotocin. Animals with a fasting blood glucose concentration >25mmol/L were considered diabetic and included in the study. Thereafter, respective doses of Tulbaghia violacea and conventional drugs were daily administered to the diabetic groups by oral gavage for seven weeks. At week six, an oral glucose tolerance test was performed. At the end of week 7, the animals were euthanized by halothane overdose. Blood was collected and organs were harvested for further biochemical analyses. Results: Tulbaghia violacea treatment significantly increased plasma insulin and liver glycogen content. Tulbaghia violacea treatment also reduced liver thiobarbituric acid reactive substances levels, increased liver superoxide dismutase concentration and increased plasma nitric oxide levels. Furthermore, Tulbaghia violacea administration reduced serum triglycerides, total cholesterol, VLDL cholesterol, LDL cholesterol and increased HDL cholesterol. The plant treated group showed increased pancreatic islet counts as well as improved glomerular morphology. The angiotensin converting enzyme inhibitor captopril showed a significant increase in angiotensin converting enzymeactivity as well as increased angiotensin type 1 receptor expression compared to the diabetic controls and Tulbaghia violacea. Conclusion: Tulbaghia violacea did not decrease fasting blood glucose levels or improve glucose tolerance. However, in this study, the data obtained demonstrated the ability of Tulbaghia violacea to elicit antioxidant and hypolipidemic effects, augment plasma insulin levels, improve pancreatic and glomerular morphology and positively impact β- cell function in a fructose-fed streptozotocin induced diabetic rat model.