The phosphorylation state of casein and the species-dependency of its hypercholesterolaemic effect.
1. The present study concerns the question whether the hypercholesterolaemic effect of casein, a phosphorylated protein, is modified in species differing both in glycine-taurine conjugation of bile acids and in intestinal alkaline phosphatase (EC 3.1.3.1). 2. Since these two variables are entirely different in rabbits and rats, identical (cholesterol-free) semi-purified diets containing either casein or soya-bean protein were given to both species. 3. In rabbits casein, as compared with soya-bean protein, did not affect calcium absorption but immediately increased phosphate absorption and decreased faecal excretion of bile acids. These effects preceded the accumulation of apo B-cholesterol in serum, which indicates a cause-and-effect relation. 4. In contrast, none of these casein-specific effects were observed in rats. 5. These results suggest that the hypercholesterolaemic potential of casein is expressed mainly in species (like the rabbit) with a low activity of intestinal phosphatase and with a high glycine conjugation of bile acids. This might explain why species (like rat and man) are rather insensitive to dietary casein.
Van der Meer
R
R
Department of Nutrition, Netherlands Institute for Dairy Research, Ede.
De Vries
H T
HT
Van Tintelen
G
G
D000818:Animals; D001647:Bile Acids and Salts / Q000032:analysis; D001835:Body Weight; D002118:Calcium / Q000378:metabolism; D002364:Caseins / Q000009:adverse effects*; D004044:Dietary Proteins / Q000009:adverse effects*; D005243:Feces / Q000032:analysis; D006937:Hypercholesterolemia / Q000209:etiology* / Q000378:metabolism; D008297:Male; D010710:Phosphates / Q000378:metabolism; D010766:Phosphorylation; D011817:Rabbits; D051381:Rats; D011919:Rats, Inbred Strains; D013045:Species Specificity
D001647:Bile Acids and Salts; D002364:Caseins; D004044:Dietary Proteins; D010710:Phosphates; D002118:Calcium