Medical Physiology

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Browsing Medical Physiology by Subject "Afriplex GRT extract"

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    The effect of green rooibos extract on rat hearts in a pre-diabetic model : an evaluation of the function and mechanisms involved
    (Stellenbosch : Stellenbosch University, 2019-03) Smit, Sybrand Engelbrecht; Huisamen, Barbara; Marais, Erna; Johnson, Rabia; Stellenbosch University. Faculty of Medicine and Health Sciences. Dept. of Biomedical Sciences: Medical Physiology.
    ENGLISH ABSTRACT: Background— Cardiovascular diseases (CVD) remains the leading cause of death globally, with a rising prevalence of individual risk factors such as obesity and insulin resistance. Furthermore, diabetic patients are particularly at risk for developing ischemic heart disease and strokes. In patient suffering an ischemic event, most of the myocardial damage incurred happens once blood flow is restored – a phenomena known as reperfusion injury. Mitochondrial ROS production is implicated as one of the major contributors to cell death in the reperfused heart and the importance of mitophagic processes (mitochondrial housekeeping) could be a potential therapeutic target to prevent ischemia/reperfusion injury (I/R-I). Aspalathus linearis (commonly known as rooibos) is an indigenous South African plant grown exclusively in the Western Cape fynbos region. Rooibos is rich in bioactive phenolic compounds, including aspalathin, a C-linked dihydrochalcone glucoside unique to rooibos, known for its hypoglycemic and strong antioxidant potential. Methods— The present study made use of 300 Wistar rats randomly allocated into controls and rats receiving a 16-week high-fat, high-caloric diet (HCD). After 10 weeks on the respective diets, half of each group received 60 mg/kg/day Afriplex green rooibos extract (GRT), containing 12% aspalathin, for 6 weeks. The primary aim was to investigate its therapeutic potential in treating 20 min global ischemia/reperfusion injury (I/R-I) in rats with increased susceptibility for CVD, as well as determine the mitochondrial oxidative phosphorylation (OxPhos) during four stages of I/R-I. The secondary aim was to elucidate GRT’s effect on cardiac signaling and mitophagy with regards to I/R-I. Results— HCD over 16 weeks resulted in daily increased food intake (22.30±1.27 g vs 18.00±0.54 g = ↑24%; p<0.001), decreased daily water intake (19.55±0.58 mL vs 29.74±0.74 mL = ↓34%; p<0.001), leading to increased body weight (403.9±5.1 vs373.6±4.8 g = ↑8%; p<0.001) and increased intraperitoneal fat (23.69±0.89 vs 13.98±0.43 g = ↑69%; p<0.001) compared to age-matched controls. Furthermore, HCD increased fasting blood glucose (5.75±0.16 vs 5.21±0.16 mM = ↑10%; p<0.05), fasting blood insulin (6.20±0.57 vs 4.31±0.54 ng/mL = ↑44%; p<0.05) and insulin resistance through raised HOMA-IR (3.52±0.35 vs 2.30±0.28 = ↑53%; p<0.05) compared to age-matched controls. GRT supplementation for 6 weeks had no significant effect on biometric parameters in either controls or HCD. Pre-ischemia, HCD rats presented with worse functional heart parameters, such as diastolic and systolic pressure, aortic output (AO), cardiac output (CO) and total work (WT) (10.69±0.14 vs 12.6±0.19 mW = ↓15%; p<0.001) compared to controls, while GRT supplementation was able to significantly improve these parameters in both controls (13.91±0.23 mW = ↑10%; p<0.001) and HCD (11.98±0.20 mW = ↑12%; p<0.001). GRT administration also lowered the heart rate during stabilization in both control and HCD by an average 10 bpms (p<0.05). Post-ischemia, HCD hearts were weaker than controls and had a lower WT recovery (55.51±2.28 vs 64.8±2.04% = ↓14%; p<0.01), while GRT restored WT recovery in HCD (63.35±2.49% = ↑14%; p<0.05). HCD rats also had a greater infarct size compared to controls (34.99±11.56 vs 16.42±8.71% = ↑113%; p<0.01) following a 35 min regional ischemia protocol. GRT supplementation led to a remarkable reduction in infarct size (13.22±6.66% = ↓62%; p<0.001), while conferring no added protection to controls (14.58±5.43%). Regarding cardiac and mitochondrial signaling, prior to ischemia HCD heart had a decreased dependence on insulin-dependent AMPK and increased inflammation via upregulated p38, whereas GRT treatment presented with decreased insulindependent PKB and AS160 signaling (together with increased FA OxPhos compared to carbohydrates, however showed more mitochondrial uncoupling, decreasing basal metabolic rate and thereby potentially less ROS production), inhibited GSK3β and conferred an anti-inflammatory effect by significantly reducing p38 activation. HCD also had higher mitophagy rates through Parkin and LC3 signaling. After 20 min ischemia, in HCD, ATM and AMPK were upregulated and insulin-dependent PKB downregulated with GSK3β. Mitophagy signals, such as PINK1 and p62 were elevated, but autophagic flux remained low during ischemia in all groups. GRT supplementation resulted in an opposite profile with AMPK downregulated and showing inhibition of ERK1/2. In early reperfusion, all protective signaling were downregulated in HCD including AMPK, PKB, AS160, GSK3b and ATM. Mitophagy was also activated through Parkin, p62 and LC3 while having increased OxPhos potential in FA compared to carbohydrates. GRT supplementation reduced oxidative stress and inflammation through downregulation of JNK1/2 and p38, and initiated mitophagy through an AMPKdependent mechanism and Parkin. GRT supplementation also inhibited mitochondrial OxPhos after reperfusion culminating in a potentially decreased ROS production. Conclusion— This study showed the cardioprotective effect of Afriplex GRT supplementation by improving functional heart recovery and reducing infarct size post-ischemia in rats with elevated risk for CVD. Another novel find is the reduction in heart rate induced by GRT treatment through inhibition of pacemaking cells. This could have potential therapeutic application in patients suffering from ischemic heart disease. GRT ilicits a cardiotonic effect in I/R-I through anti-inflammatory mechanisms pre- and post-ischemia. In early reperfusion, GRT treatment resulted in decreased oxidative stress, inhibition of mitochondrial OxPhos and enabled AMPKdependent mitophagy. GRT shows promise as a strong antioxidant and anti-inflammatory agent in managing adverse outcomes in patients at risk for CVD.
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    Investigating the modulating effects of Afriplex GRT Extract on vascular function and antioxidant status in obese Wistar rat
    (Stellenbosch : Stellenbosch University, 2018-03) Maqeda, Zimvo; Windvogel, Shantal; Huisamen, Barbara; Stellenbosch University. Faculty of Medicine and Health Sciences. Dept. of Biomedical Sciences: Medical Physiology.
    Introduction Obesity is associated with the development of metabolic syndrome, a conglomerate of cardiometabolic risk factors, which synergistically result in cardiovascular diseases (CVDs), the major leading cause of death worldwide. The indigenous South African plant Rooibos (Aspalathus linearis), contains polyphenolic phytochemicals such as aspalathin, which is unique to Rooibos and has been associated with its health promoting properties. These include antidiabetic, anti-inflammatory, antioxidant, anti-obesity and cardiovascular benefits. Not much is known about the health promoting properties of Afriplex GRTTM, an aspalathin-rich Rooibos extract. It is hypothesised that Afriplex GRT™ may ameliorate the development of hypertension, vascular dysfunction and oxidative stress in a model of obese Wistar rats. Aim To investigate the ameliorative effect of Afriplex GRT™ extract on blood pressure, vascular function and oxidative stress in diet-induced obese Wistar rats. Methods Adult male Wistar rats were randomly divided into 5 experimental groups (n=10/group) and fed a Control or high-fat-diet (HFD), to induce obesity over a period of 16 weeks. Rats in the HFD and Control groups received the aspalathin-rich extract supplemented at 60 mg/kg/day from week 10 to 16. A Captopril (50 mg/kg/day) group was included as a positive control. Food and water intake, body weight, blood glucose, blood pressure, intraperitoneal (IP) fat mass, liver weight, leptin levels and vascular reactivity was measured. Western blotting of proteins involved in vascular function such as eNOS, AMPK and PKB were performed in aortic tissue. Antioxidant status and oxidative stress were determined in the liver tissue of experimental groups. This was done by measuring the activities of the primary antioxidant enzymes superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), and performing the thiobarbituric reactive substances (TBARS) assay which measures malondialdehyde as an indicator of lipid peroxidation. Results and Discussion HFD animals presented with increased food intake, leptin levels, body weight, glucose levels, IP fat and liver mass compared to Control animals. Furthermore, HFD animals had decreased fluid intake and increased blood pressure vs the Control animals. Additionally, they presented with a downregulation in total and phosphorylated PKB and AMPK expression. HFD rats also had reduced SOD, CAT and GPx activity, increased malondialdehyde (MDA) levels and phosphorylated eNOS levels vs Control animals. Supplementation with GRT extract significantly decreased body weight, leptin levels, IP fat, liver mass and improved glucose metabolism. Furthermore, it increased vasodilation, total eNOS expression, AMPK phosphorylation according to the AMPK ratio, whereas it decreased blood pressure. Additionally, it upregulated SOD, CAT and GPx activity and decreased MDA levels in the liver. Captopril decreased blood pressure, increased vasodilation and upregulated PKB, AMPK and eNOS expression. Therefore, supplementation with GRT extract alleviated the plethora of cardiovascular risk factors presented by the HFD animals. Conclusion The HFD model demonstrated detrimental effects on cardiovascular health. Treatment with the Afriplex GRTTM extract improved glucose metabolism, vascular function and antioxidant status in the HFD animals. Therefore, Afriplex GRT™ extract may be a potential therapeutic agent against obesity-related vascular dysfunction, impaired glucose homeostasis, elevated blood pressure and oxidative stress.