Serum lipoproteins of rabbits fed semi-purified diets varying in protein and carbohydrate source

The effect of dietary protein and carbohydrate type on the composition and properties of serum lipoproteins in rabbits was studied. The animals were pair-fed either casein-sucrose and soy protein-sucrose or casein-dextrose and soy protein-dextrose-containing low fat, low cholesterol, semi-purified diets for 84 days. Main effects due to protein and carbohydrate type were observed to be altered lipoprotein class compositions. These effects were due primarily to the presence of casein which resulted in cholesterol-rich, triglyceride-poor lipoproteins among all isolated classes. Increases in serum low and high density lipoprotein cholesterol and protein concentrations, as well as lipoprotein total mass, were also observed with casein feeding. Carbohydrate effects due to dietary sucrose were elevated high density lipoprotein phospholipid and protein concentrations, independent of protein source. When casein was included, sucrose-containing diets resulted in increased intermediate density lipoprotein cholesterol; when soy protein was used, low density lipoprotein cholesterol elevations were observed. Dietary interactions were also found especially between casein and sucrose, resulting in increased intermediate lipoprotein mass and total lipoprotein concentrations. Comparisons of lipoprotein class particle size among rabbits indicated similar particle diameters among animals in all dietary groups. Evidence that casein feeding caused increased lipoprotein particle number in addition to compositional differences was obtained. It was concluded that lipoprotein structure within a given class is maintained in spite of compositional variations due to dietary protein or carbohydrate source.