High-cholesterol diet enriched with onion affects endothelium-dependent relaxation and NADPH oxidase activity in mesenteric microvessels from Wistar rats.
BACKGROUND
The aim of the present study was to examine the effects of onion as functional ingredient on the oxidative status, lipoprotein levels (total cholesterol-TC, HDL-C, LDL-C), triacylglycerides (TAG) and vascular reactivity of mesenteric arteries in hypercholesterolemic Wistar rats.


METHODS
Twenty-four animals were fed with three different diets [control, high-cholesterol diet (HC) and high-cholesterol enriched with onion diet (HCO)]. After seven weeks of experimental feeding the rats were euthanized for blood and tissues collection. TC, HDL-C, LDL-C and TAG were measured, and 2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) radical cation (ABTS(•+)) scavenging capacity and ferric reducing antioxidant power (FRAP) were determined in plasma. Superoxide dismutase (SOD) and glutathione peroxidase (GPx) enzyme activities were assayed in erythrocyte lysates. Endothelium-dependent vasodilation to acetylcholine was evaluated in mesenteric arterial segments. NADPH oxidase (NOX) was also measured by lucigenin-derived chemiluminiscence.


RESULTS
The dietary cholesterol content significantly affected plasma lipoprotein levels, increased superoxide generation from NOX, and caused impaired endothelium-dependent vasodilation in the rat mesenteric arteries. Onion ingredient improved antioxidant status in HCO group, as it was evidenced by ABTS(•+) and FRAP values and SOD and GPx enzyme activities compared to the HC-fed group, reduced the increment in NOX activity and reversed endothelial dysfunction promoted by the HC diet. Scavenging of superoxide with TEMPOL or inhibition of NOX with apocynin improved endothelium-dependent vasodilation only in HC-fed rats.


CONCLUSIONS
Enrichment of diet with onion as functional ingredient could be proposed as a complementary approach to prevent or partially modulate vascular dysfunction, reducing some of the risk indexes linked to initial development of atherosclerosis.
Institute of Food Science, Technology and Nutrition (ICTAN), Spanish National Research Council (CSIC), José Antonio Novais 10, ES-28040 Madrid, Spain.
Diana
D
González-Peña
Servicio de Histología-Investigación, Instituto Ramón y Cajal de Investigación Sanitaria (IRYCIS), ES-28034 Madrid, Spain.
Javier
J
Angulo
Departamento de Farmacología, Facultad de Medicina, Universidad Autónoma de Madrid, ES-28029 Madrid, Spain.
Susana
S
Vallejo
Institute of Food Science, Technology and Nutrition (ICTAN), Spanish National Research Council (CSIC), José Antonio Novais 10, ES-28040 Madrid, Spain.
Clara
C
Colina-Coca
Institute of Food Science, Technology and Nutrition (ICTAN), Spanish National Research Council (CSIC), José Antonio Novais 10, ES-28040 Madrid, Spain.
Begoña
B
de Ancos
Departamento de Farmacología, Facultad de Medicina, Universidad Autónoma de Madrid, ES-28029 Madrid, Spain.
Carlos F
CF
Sánchez-Ferrer
Departamento de Farmacología, Facultad de Medicina, Universidad Autónoma de Madrid, ES-28029 Madrid, Spain.
Concepción
C
Peiró
Institute of Food Science, Technology and Nutrition (ICTAN), Spanish National Research Council (CSIC), José Antonio Novais 10, ES-28040 Madrid, Spain.
Concepción
C
Sánchez-Moreno
Dietary cholesterol; Functional foods; Mesenteric microvessels; NADPH oxidase; Onion