Therapeutic Effect of a triterpenic Acid from Protorhus longifolia Against High Fat Diet Fed and Streptozotocin-induced Diabetic Nephropathy in Rats
Diabetic nephropathy (DN) is the major and most frequent complication of diabetes mellitus that contributes to high rate of morbidity and mortality worldwide. Despite the current available treatment regimes, DN still remains the main leading cause of end stage kidney disease. Therefore, more focus is currently placed on the search for alternatively new and effective therapeutic agents, preferably of plant origin. Thus, the present study is aimed at evaluating the therapeutic potential of a plant-derived lanosteryl triterpene (RA5), against high fat diet (HFD) fed and streptozotocin (STZ)- induced diabetic nephropathy in rats. RA5 was isolated from the chloroform extract of Protorhus longifolia stem bark. Chemical structure of RA5 was confirmed based spectral data analysis. The in vitro antioxidant activity of the compound was assessed against DPPH and nitric oxide (NO•) radicals. Its reducing power and metal ion chelating potential were also assessed. The bovine serum albumin (BSA) and haemoglobin fructose assays were used to evaluate theanti- protein glycation activity of RA5. The in vitro inhibitory potential of RA5 against xanthine oxidase (XOD) and angiotensin converting enzyme (ACE) activity was also investigated. The antihyperglycemic potential of RA5 was first established and confirmed in the STZ-induced diabetes rat model. Its therapeutic potential against diabetic nephropathy was then investigated in the HFD and STZ induced diabetic nephropathy in rats. In the STZ (60 mg/kg)-induced diabetes in the rat model, the diabetic animals were treated with RA5 (100 mg/kg) for 14 days and the oral glucose tolerance of the rats was determined. In the HFD fed and STZ induced diabetic nephropathy in rat model, the HFD fed (hyperlipidaemic) rats received an intraperitoneal injection of a low dose of STZ (30 mg/kg) to induce diabetes. The diabetic rats were treated orally with RA5 at 100 mg/kg, daily for 28 days. Metformin (100 mg/kg) and 2% Tween 20 were used as positive and negative controls. All the rats were then euthanized, and blood, liver and kidneys were collected for analysis of important biochemical parameters. The in vitro study revealed the antioxidant potential of the triterpene (RA5) as it effectively scavenged DPPH and NO• radicals. The triterpene also showed reducing power and metal ion chelating properties. The study further showed an anti-protein glycation effect by the inhibition of glycation of BSA and haemoglobin. Significantly, iv an increase in fasting blood glucose (FBG) levels, increased hepatic glucose 6phosphatase activity and decreased glycogen content with impaired oral glucose tolerance were observed in the untreated diabetic rats. However, the diabetic rats that were treated with RA5 for 14 days showed a significant decrease in fasting blood glucose levels, decreased glucose 6-phosphatase activity and increased glycogen content. The RA5 treated rats further showed improved oral glucose tolerance. In the diabetic nephroprotective assessment, kidney hypertrophy elevated FBG, blood lipids, renal function biomarkers such as blood urea nitrogen, creatinine and uric acid, as well as increased XOD and ACE levels were observed in the untreated diabetic rats. However, the levels of all these parameters were reversed after receiving treatment with RA5 for period of 28 days. Increased renal levels of antioxidant status, accompanied by decreased malondialdehyde levels were likewise observed in the RA5 treated rats in comparison to the untreated diabetic control. Furthermore, the results revealed decreased renal levels of inflammatory markers (transforming growth factor beta-1, cycloogenase-2, TNF-α, and IL-6) in the diabetic group treated with RA5 when compared to the untreated diabetic control. The obtained results suggest that the diabetic RA5 possess therapeutic potential against DN.
Diabetic nephropathy (DN), triterpenic Acid, Protorhus longifolia, High Fat Diet
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