INTERACTIVE EFFECTS OF INCREASED INTAKE OF SATURATED FAT AND CHOLESTEROL ON ATHEROSCLEROSIS IN THE JAPANESE-QUAIL (COTURNIX JAPONICA)

Increasing the energy value of diets with dietary fat, particularly fa ts rich in saturated fatty acids, can result in the elevation of plasm a total and lipoprotein cholesterol. In the present study, experimenta l diets were designed to examine the effects of increasing the energy content of diets with a saturated fat source and cholesterol in a non- purified diet on hyperlipoproteinaemia and aortic plaque composition i n the atherosclerosis-susceptible Japanese quail (Coturnix japonica) m odel of human atherosclerosis. Commercial poultry diets containing two levels (i.e. 60 or 120 g/kg) of beef tallow as the primary source of saturated fat were balanced for endogenous cholesterol or supplemented with cholesterol (i.e. 0.5 or 5.0 g/kg) and fed to quail for 9 weeks to examine the effects on whole plasma, Lipoprotein and aortic plaque lipid composition in relation to aortic plaque formation. Hypercholest erolaemia (P<0.001) was confirmed in birds fed on high-cholesterol (HC ) diets only. An interaction (P = 0.05) between dietary cholesterol an d fat intake level was observed for plasma triacylglycerols (TG) and w as specific to changes observed in VLDL composition. Diet-induced chan ges in lipoprotein total cholesterol, TG and phospholipid composition were greatest in the portomicron and VLDL fractions in birds fed on at herogenic diets. Hyperlipoproteinaemia induced by the 60 g/kg added be ef tallow-HC diet resulted in significant (P < 0.001) aortic plaque de position, which was further enhanced in birds fed on the 120 g/kg beef tallow-HC diet. Quail fed on 120 g/kg beef tallow-HC diets exhibited the most severe aortic plaque formation, with marked increases in aort ic tissue cholesterol content and quantifiable amounts of several chol esterol oxides (5,6 alpha-epoxy-5 alpha-cholesterol, 7 beta-hydroxycho lesterol, cholestanetriol, 7-ketocholesterol and 25-hydroxycholesterol ). In summary, hyperlipoproteinaemia associated with HC diets with a g reater proportion of energy from saturated fat produced a combined eff ect in altering plasma and lipoprotein lipid composition as well as ao rtic tissue cholesterol and cholesterol oxide content in the Japanese quail.