Browsing by Author "Mahlangu, Dawn Nomusa"
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- ItemInvestigating the Modulating effects of Fermented Rooibos (Aspalathus linearis) and Fermented Honeybush (Cyclopia intermedia) on aortic endothelial function and antioxidant status in Streptozotocin (STZ) – induced diabetic Wistar rats(Stellenbosch : Stellenbosch University, 2020-03) Mahlangu, Dawn Nomusa; Windvogel, Shantal; Marais, Erna; Smit-Van Schalkwyk, Michelle; Stellenbosch University. Faculty of Medical Sciences. Dept. of Biomedical Sciences: Medical Physiology.ENGLISH ABSTRACT: Introduction: Diabetes mellitus is a metabolic disorder that causes chronic hyperglycaemia due to insulin resistance and deficiency. The implications that chronic hyperglycaemia has on vascular function have established diabetes mellitus as a risk factor for the development of endothelial dysfunction and the associated cardiovascular effects such as hypertension. Aspalathus linearis and the Cyclopia species are medicinal plants that have antioxidant, anti-inflammatory, anti-mutagenic and anti-diabetic properties. However, not enough research has been done to determine the modulating effects of fermented rooibos and fermented honeybush on vascular function, hypertension and antioxidant status in the context of diabetes mellitus. Aim: To investigate the modulating capacity of 2% fermented rooibos (RB) (Aspalathus linearis) and 4% fermented honeybush (HB) (Cyclopia intermedia) on vascular function, hypertension and antioxidant status in streptozotocin-induced diabetic rats. Methods: Adult male Wistar rats were divided into 7 groups and acclimatized to human handling and the blood pressure apparatus for 1 week. Subsequently, diabetic rats treated with 2% RB or 4% HB were acclimatized to the taste of the infusions for 1 week prior to receiving an intraperitoneal injection of 45mg/kg bw streptozotocin. Animals were then treated with 2% RB or 4% HB infusions for 6 weeks. Thereafter biometric measurements; body weight, fluid intake, food intake, blood glucose, relative kidney organ weight and intraperitoneal glucose tolerance test (IPGTT) were performed. Aortic tissue was used to assess the endothelial proteins eNOS and PKB/Akt involved in vascular function and to conduct vascular contraction/relaxation studies. Furthermore, antioxidant status was assessed in the kidney tissue by means of the superoxide dismutase (SOD) and catalase (CAT) antioxidant enzyme assays. Additionally, the TBARS assay was conducted in kidney tissue to assess lipid peroxidation, a biomarker of oxidative stress. Results: At the end of the 6-week treatment period, the diabetic animals developed hyperglycaemia, impaired glucose tolerance, weight loss, increased fluid and food intake and increased kidney weight that was not ameliorated by the 2% RB and 4% HB treatment. Furthermore, the streptozotocin injury model exerted a pro-contractile and an anti-relaxation effect on aortic vascular reactivity. Treatment with 2% RB or 4% HB significantly reduced the vasoconstriction caused by streptozotocin and restored the vasorelaxation response of the aorta, with the RB exhibiting a greater restorative effect than HB. Furthermore, in the aortic tissue, the STZ injury model significantly reduced total and phosphorylated eNOS and iii PKB/Akt expression which was not ameliorated by treatment with 2% RB and 4% HB. Additionally, no significant changes were observed in the blood pressure, antioxidant enzyme and TBARS measurements of all treatment groups. Conclusion: Streptozotocin-induced diabetic animals developed hyperglycaemia, polydipsia, polyphagia, weight loss and impaired glucose tolerance. Furthermore, the fermented RB and fermented HB infusions ameliorated the streptozotocin-induced vascular injury of the aorta, thus improving aortic vascular reactivity and endothelial function. Furthermore, treatment with RB and HB did not alleviate hyperglycaemia or affect blood pressure and the antioxidant status of the diabetic rats as measured in the kidney in the 6week treatment duration.