Effects of excess dietary L-cystine on the rat plasma lipoproteins.
The effects of excess dietary cystine on the cholesterol and protein contents of rat plasma lipoproteins are described. 5% L-cystine was added to a semisynthetic diet containing 23% casein and 0.05% cholesterol, to the same diet enriched with 1% cholesterol or containing tristearin instead of lard. Rats were fed the diets during 2 months. The addition of cystine led to an increase in the plasma cholesterol level of the rats fed with the basal diet (from 0.92 to 1.56 mg/ml). But it produced a reduction of this level in cholesterol-fed rats (from 1.71 to 1.49 mg/ml). These different changes in the total plasma cholesterol level are explained by the specific effects of cystine on each lipoprotein: whatever the diet, cystine supplementation reduced the chylomicron and VLDL cholesterol contents and increased that of LDL (especially LDL2: density 1.040-1.063) and HDL. This study allowed us to compare 2 conditions which lead to hypercholesterolemia but which have opposite effects on hepatic cholesterogenesis: the supplementation of the same basal diet with 1% cholesterol or 5% cystine. In cholesterol-fed rats, the major part (49%) of plasma cholesterol was found in the chylomicrons and VLDL while the LDL2 cholesterol content was low (0.07 mg/ml plasma). Conversely, cystine-fed rats had a low chylomicron and VLDL plasma content (both enriched in apoprotein E), whereas up to 33% of the plasma cholesterol were carried by LDL2. Thus the production of LDL2 in cholesterol and cystine-fed rats could be related to hepatic cholesterogenesis.
D000818:Animals; D002784:Cholesterol / Q000097:blood; D002791:Cholesterol, Dietary / Q000008:administration & dosage; D002914:Chylomicrons / Q000378:metabolism; D003553:Cystine / Q000008:administration & dosage*; D004032:Diet; D004044:Dietary Proteins / Q000008:administration & dosage*; D004591:Electrophoresis, Polyacrylamide Gel; D008074:Lipoproteins / Q000097:blood*; D008077:Lipoproteins, LDL / Q000097:blood; D008079:Lipoproteins, VLDL / Q000097:blood; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains
D002791:Cholesterol, Dietary; D002914:Chylomicrons; D004044:Dietary Proteins; D008074:Lipoproteins; D008077:Lipoproteins, LDL; D008079:Lipoproteins, VLDL; D003553:Cystine; D002784:Cholesterol