Sex-related alterations in antioxidant status and susceptibility to atherosclerosis in Japanese quail

To examine antioxidant enzyme activities in aorta and blood of male and female Japanese quail on control or cholesterol-supplemented diets, given the strong influence of sex and the postulated role of oxidative processes in the pathogenesis of atherosclerosis.

Atherosclerosis-prone Japanese quail (15 of each sex) were either maintained on a control diet or fed a cholesterol-supplemented (1% by weight) diet for nine weeks.

Plasma cholesterol levels in controls were comparable in both sexes, although females showed higher triglyceride levels. Cholesterol supplementation increased plasma cholesterol in both males (8.1-fold) and females (2.5-fold) but triglycerides were significantly elevated (3.4-fold) by cholesterol feeding only in males. Cholesterol supplementation increased aortic cholesterol content to a greater extent in males (2.2-fold) than in females (1.4-fold) and plaque formation was apparent only in males. Cholesterol-fed birds showed small, but significant, sex-related differences in antioxidant enzyme profiles of aorta (glutathione peroxidase activity was higher in males and superoxide dismutase activity was lower in females) and red blood cells (glutathione peroxidase activity was higher in females). Cholesterol feeding was associated with opposing effects on the activity of plasma glutathione peroxidase (increased in males but decreased in females). Evidence was also found for complex sex- and tissue-related differences in patterns of ageing over the nine-week experimental period.

Although sex-related differences in antioxidant enzyme profiles are demonstrable in aortic tissues and blood of Japanese quail fed control or cholesterol-supplemented diets, it seems unlikely that these are of sufficient magnitude to account for the large difference in susceptibility to atherosclerosis between males and females. The complex sex- and tissue-dependent effects of ageing on the activities of antioxidant enzymes observed emphasize the importance of age- and sex-matched controls in experimental studies of antioxidant enzyme alterations in disease processes generally.