Dietary lipids and in vivo antioxidant status in atherosclerosis resistant (rat) and sensitive (quail) animals

Studies were performed in two animal models known to be susceptible to (i) age-dependent hypertension and (ii) atherosclerosis, for the purpose of examining the role of specific dietary fat sources and dietary cholesterol intake in modifying hypertension and atherosclerosis, two well defined risk factors in the development of cardiovascular disease. Despite exhibiting hypertension, the spontaneously hypertensive rat (SHR) had lower (p 0.05) plasma cholesterol and triacyiglyceride concentrations than normotensive Wistar Kyoto (WKY) controls. SHR and WKY animals exhibited tissue- and enzyme-specific strain differences in antioxidant status. Systolic blood pressure (SBP) was positively (r = 0.709, p = 0.049) correlated with RBC superoxide dismutase (SOD) activity and negatively correlated with liver glutathione reductase (GSSG-Red; r = -0.798, p = 0.018). Dietary fat source or the proportion of saturated to unsaturated (n-6 or n-3) fatty acids fed at a moderate level of fat intake (e.g. 22% calories) did not have an effect on plasma lipids, with the exception of menhaden oil which significantly reduced both plasma cholesterol and triacylglyceride levels. There was no effect of dietary fat source or cholesterol on SBP of SHR or WKY animals. Menhaden oil fed to SHR and WKY animals resulted in decreases in RBC, heart and liver glutathione peroxidase (GSH-Px) and SOD activities as well as reduced tissue susceptibility to in vitro lipid peroxidation in these same animals. High levels of dietary cholesterol resulted in reduced (p 0.05) hepatic CAT, SOD and GSH Px activities as well as greater resistance to in vitro lipid peroxidation than in counterparts fed low cholesterol diets. Despite significant effects of dietary cholesterol and fat source on plasma lipids and antioxidant parameters in hypertensive SHR, changes to SBP were not observed in the present study involving relatively young animals. Similar studies examining the effects of dietary cholesterol intake and fat source or level on plasma lipids, antioxidant status and aortic plaque were conducted in the atherosclerosis-susceptible Japanese quail. Diet-induced hypercholesterolemia in quail fed 0.5% cholesterol-O.25% cholic acid diets for 9 weeks was associated with the presence of aortic plaque containing cholesterol and cholesterol oxides. Aortic atherosclerosis was not associated with alterations in the antioxidant status of these quail. Moderate dietary levels (22% calories from fat) of saturated fat (e.g. butter, beef tallow) or unsaturated fat (e.g. soybean) did not alter plasma lipids, or severity of aortic plaque in birds, although activity of GSH-Px in RBCs and heart were increased and decreased, respectively, in soybean oil-fed birds. In the final study, an increase in total calories from saturated fat (e.g. beef tallow) together with different levels of dietary cholesterol were found to have interactive effects on plasma triacylglycerides, and aortic plaque scores of atherosclerosis-susceptible Japanese quail. These dietary treatments did not have any effect on antioxidant enzymes of heart or aortic tissue. Dietary cholesterol and the higher level of saturated fat did, however, influence hepatic CAT and SOD activities, as well as reducing the susceptibility of liver and heart tissues to in vitro lipid oxidation. It was noteworthy that a significant (p 0.05) interaction was observed between dietary cholesterol and fat level for plasma triacylglycerides but not plasma cholesterol. Elevations in plasma cholesterol and triacylglycerides in atherosclerotic quail paralleled the severity of aortic lesions, as determined by plaque score, cholesterol content and presence of cholesterol oxides in aortic tissue from these birds. The presence of plasma hypercholesterolemia and hypertriacylglyceridemia in the atherosclerosis-susceptible Japanese quail appeared to play a greater role in determining susceptibility to the development of aortic plaque than tissue antioxidant status under the experimental conditions employed herein. In summary, specific differences in tissue antioxidant enzymes and susceptibility to lipid peroxidation were more evident in the genetically hypertensive SHR rat model, than in diet-induced atherosclerosis in the atherosclerosis-susceptible Japanese quail.Land and Food Systems, Faculty ofGraduat