Genetics of oxidative stress in obesity

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.

Lipid Peroxidation and Antioxidant Status in Nonobese Type 2 Diabetes Mellitus

The aim of the study was to investigate the association between lipid peroxidation and antioxidant status in nonobese type 2 diabetes mellitus (T2DM) and further to correlate whether their significant association is putatively associated with the pathogenesis of T2DM. A number of 102 nonobese T2DM subjects and 95 nondiabetic subjects as healthy controls were enrolled in this cross-sectional study. Serum samples were collected in cryovials for malondialdehyde (MDA) and thiol assays. Total thiol or sulfhydryl (–SH) groups in peripheral blood mononuclear cells (PBMCs) and sera, as well as level of MDA, a marker for lipid peroxidation in serum, were measured spectrophotometrically. Serum MDA level was found significantly higher whereas serum and PBMC total thiol levels were diminished significantly among nonobese T2DM subjects compared to HC subjects. Moreover, serum MDA level is found to have a significant inverse correlation with serum total thiol and PBMC thiol levels among DM subjects, but no significant correlation was observed in HC individuals. A significant inverse correlation between serum MDA and serum total thiol levels among nonobese T2DM subjects suggests a close association of increased oxidative stress with decreased antioxidant status in nonobese T2DM.