The fruit extract of Garcinia atroviridis (G. atroviridis) contains hydroxycitric acid and flavonoids, which have been reported to have a hypolipidaemic property. This extract with solvent methanol was used to investigate its effects on serum lipid profiles of guinea pigs fed a high cholesterol diet.
Atherosclerosis impairs endothelium-dependent relaxation of large conduit arteries. Because coronary resistance vessels are spared from the development of overt atherosclerosis, endothelium-dependent responses were examined in these vascular segments. Malaysian cynomolgus monkeys (n = 6) were made atherosclerotic by being fed a 0.7% cholesterol diet for 18 months. Control monkeys (n = 6) were fed a standard diet. Coronary microvessels (122-220 microns) were studied in a pressurized (20 mm Hg), no-flow state using a video-imaging apparatus. Relaxations of microvessels, preconstricted with the thromboxane analogue U46619, were determined in response to acetylcholine, bradykinin, the calcium ionophore A23187, adenosine, and sodium nitroprusside. Microvascular relaxations to bradykinin and A23187 were reduced in atherosclerotic monkeys compared with controls, whereas acetylcholine produced additional contraction in atherosclerotic monkeys. Responses of preconstricted microvessels to adenosine and sodium nitroprusside were identical in atherosclerotic and control animals. Indomethacin did not alter responses in control or atherosclerotic animals. Histologic examination revealed neither intimal thickening nor plaque formation in microvessels of this size class despite marked changes in conduit arteries. Electron microscopy showed minor alterations of endothelial cell morphology in microvessels of atherosclerotic animals. In conclusion, long-term hypercholesterolemia markedly impairs endothelium-dependent vascular relaxation in the coronary microcirculation where overt atherosclerosis does not develop. These changes in endothelial cell function may significantly alter regulation of myocardial perfusion by neurohumoral stimuli.
OBJECTIVE: We previously reported ethnic disparity in adverse outcomes among Asians with type 2 diabetes (T2DM) in Singapore. Central arterial stiffness can aggravate systemic vasculopathy by propagating elevated systolic and pulse pressures forward, thereby accentuating global vascular injury. We aim to study ethnic disparity in central arterial stiffness and its determinants in a multi-ethnic T2DM Asian cohort.
METHODS: Arterial stiffness was estimated by carotid-femoral pulse wave velocity (PWV) and augmentation index (AI) using applanation tonometry method in Chinese (N = 1045), Malays (N = 458) and Indians (N = 468). Linear regression model was used to evaluate predictors of PWV and AI.
RESULTS: PWV was higher in Malays (10.1 ± 3.0 m/s) than Chinese (9.7 ± 2.8 m/s) and Indians (9.6 ± 3.1 m/s) (P = 0.018). AI was higher in Indians (28.1 ± 10.8%) than Malays (25.9 ± 10.1%) and Chinese (26.1 ± 10.7%) (P < 0.001). Malays remain associated with higher PWV (β = 0.299, P = 0.048) post-adjustment for age, gender, duration of diabetes, hemoglobin A1c, body mass index (BMI), systolic blood pressure (SBP), diastolic blood pressure (DBP), soluble receptor for advanced glycation end-products, urinary albumin-to-creatinine ratio, and insulin usage, which were all independent predictors of PWV. Indians remain associated with higher AI (β = 2.776, P < 0.001) post-adjustment for age, gender, BMI, SBP, DBP, and height, which were independent predictors of AI. These variables explained 27.7% and 33.4% of the variance in PWV and AI respectively.
CONCLUSIONS: Malays and Indians with T2DM have higher central arterial stiffness, which may explain their higher risk for adverse outcomes. Modifying traditional major vascular risk factors may partially alleviate their excess cardiovascular risk through modulating arterial stiffness.
KEYWORDS: Arterial stiffness; Augmentation index; Pulse wave velocity; Type 2 diabetes