Dietary supplementation with vitamins C and E prevents downregulation of endothelial NOS expression in hypercholesterolemia in vivo and in vitro

Abstract

Impaired endothelium-dependent vasodilation has been associated with decreased NO bioavailability in hypercholesterolemia. This study aimed to determine whether antioxidant vitamins C and E could improve hypercholesterolemia-derived endothelial dysfunction in the porcine model, and whether observed in vivo results could be reproduced in vitro by incubation of coronary endothelial cells (EC) in the presence of native low-density lipoproteins (LDL). Adult mini-pigs were fed standard (C), cholesterol rich (HC) or cholesterol rich diet supplemented with vitamins C and E (HCV). Endothelium-dependent blood flow increase in response to acetylcholine was determined. Endothelial nitric oxide synthase (eNOS) expression was measured in arterial samples and in EC incubated with LDL isolated from porcine plasma. Vasomotor response to acetylcholine in HC was significantly lower (P B/ 0.05) than control and HCV. There was a significant (P B/0.05) decrease in eNOS immunoreactivity in HC, compared with HCV and control. Native LDL from HC, but not from HCV, induced a significant decrease in eNOS expression. Vitamins C and E treatment improved the endothelium-dependent vasomotor capacity and prevented decreased expression of eNOS in hypercholesterolemic pigs. A similar effect could be demonstrated in vitro, by incubation of EC with native LDL, suggesting that the effect of physiologically-modified LDL on eNOS could have a role in recovering vascular function. #

Simultaneous Assessment of Endothelial Function, Nitric Oxide Synthase Activity, Nitric Oxide–Mediated Signaling, and Oxidative Stress in Individuals with and without Hypercholesterolemia

“…Moreover, while numerous mechanisms possibly involved in hypercholesterolemia-related alterations of NO signaling have been identified in vitro and in animal models, it is still very difficult to extrapolate which of these mechanisms are relevant in humans in vivo. Major factors that may alter NO signaling in vivo are a reduced substrate availability (9 ), presence of endogenous NOS inhibitors (10 ), alterations in NOS expression (11 ) or localization (12 ), oxidative stress leading to uncoupling of NOS, and scavenging of NO by free radicals (13 ).…”

Diet and Endothelial Function

“…Human studies also support a beneficial role of antioxidants on endothelial function (18,26). It has been detected that vitamin C, a water soluble antioxidant, vitamin E and probucol, lipid soluble antioxidants, produce beneficial effects on endothelial function by decreasing the down regulation of endothelial NOS expression (27). Moreover, the deleterious effects of postprandial hypertriglyceridemia on endothelial-dependent vasodilation can be counteracted by the simultaneous administration of antioxidants, mainly vitamins C and E (28,29).…”

Vitamins C and E downregulate vascular VEGF and VEGFR-2 expression in apolipoprotein-E-deficient mice

“…Plasma concentration of thiobarbituric acid-reactive substances (TBARS) was measured, as indicator of lipid peroxidation [20]. Aorta was removed, dissected free of interstitial tissue with the help of a surgical microscope (Zeiss OPMI 6CR/S3), immediately frozen and stored at −80 • C. Tocopherol concentration in plasma was measured by high performance liquid chromatography [19].…”

“…To date, there is no clear evidence from clinical trials that antioxidants provided by dietary intake or in the form of vitamin supplements can reduce the risk of atherosclerosis [16,17]. However, a number of studies in different animal models have considered the potential for different dietary antioxidants to help prevent development and progression of atherosclerosis, and most of the experimental evidence helps substantiate this hypothesis [18,19]. Particularly, ␣-tocopherol has been shown to decrease lipid peroxidation and atherosclerosis in apoE−/− [11].…”