The effect of Eurycoma longifolia on cardiovascular related parameters in rats fed on a high-fat diet

Abstract

Cardiovascular (CV) disease, which is characterized by atherosclerosis, is known as the main cause of increased morbidity and mortality worldwide. Hypertension and hyperlipidemia are known risk factors for the development of atherosclerosis. In addition, testosterone deficiency has been associated with atherosclerosis in males. The pathophysiology of atherosclerosis remains incompletely elucidated and hindered by the etiological complexity of the disease. Eurycoma longifolia (EL), a herbal medicinal plant of the tropical region, popularly recognized in Malaysia as ‘Tongkat Ali’ is highly sought after for its aphrodisiac effect. It is also known to have antibacterial, antimalarial, antipyretic, antioxidant, cytotoxic, and anti-osteoporotic effects. There is a lack of scientific evidence regarding its effect on the CV system generally and atherosclerosis specifically. Thus this study has focused on the effects of EL on CV system-related parameters in rats fed high-fat (HF) diet. Twenty-four healthy male Sprague-Dawley rats were randomly divided into four groups: normal diet (ND), normal diet treated with EL (NDEL), high-fat diet (HFD) and high-fat diet treated with EL (HFDEL). EL (15 mg/kg) was administered orally for 12 weeks. The animal’s body weight, blood pressure (BP), testosterone level and lipid profile were measured at week 0, 6 and 12. Histological study and gene expression of NOS3 and VCAM-1 were analyzed at the end of the study period after rats were humanely sacrificed. Data were analyzed using SPSS, version. 22. Data are presented as mean (SD) and p <0.05 is significant. Results: In both treated groups (NDEL and HFDEL), the levels of serum testosterone were significantly increased when compared to that of non-treated groups. In HFD group, the levels of serum total cholesterol (TC) and triglycerides (TG) were significantly enhanced as compared to that of ND group. The levels of serum TG were substantially reduced in HFDEL group compared to that of HFD group. EL administration did not induce significant effects on the HDL-C and LDL-C. EL, furthermore, improved both systolic and diastolic BP of HFDEL compared to HFD. Moreover, EL exhibited an anti-atherosclerotic effect in the aortae of rats by reducing the intimal media thickness and improving the histological features of HFDEL group as compared to the HFD group. Findings of the gene expression did not show a significant effect of EL on the aortae. The main mechanism underlying the activity of EL remains poorly understood. Results of this study showed that EL attenuated the formation of atherosclerotic plaques in the aortae of rats fed the high-fat diet. However, further investigation is needed to explore these potential phytochemicals as anti-atherosclerotic compounds and provide sufficient baseline information for future works.