Serum Very Low Density Lipoprotein Research Articles

Lipoprotein concentrations in serum and in biopsy samples of arterial intima A quantitative comparison

Lipoprotein concentrations were compared in serum and in samples of arterial intima obtained during cardiovascular surgery. The interval between blood sampling and surgery did not exceed 48 hours. Apolipoproteins B and C, the major proteins of low density lipoprotein (LDL) and very low density lipoprotein (VLDL) respectively, were detectable by immuno-assay in all arterial specimens. Highly significant positive correlations existed between the levels of lipoproteins in the intima and in serum. In patients with elevated serum VLDL levels (Type IV hyperlipoproteinaemia) arterial concentrations of apolipoproteins B and C were increased about two-fold; in those with raised LDL levels in serum (Type II), with or without concomitant elevation of VLDL levels, the concentration of apolipoprotein B was increased almost 5-fold in the arterial intima. The arterial wall therefore contains lipoproteins or their immunologically-similar metabolites at concentrations which are determined in part by serum lipoprotein levels.

The effect of dietary supplementation of cholesterol and its subsequent withdrawal on the liver lipids and serum lipoproteins of chickens.

AbstractTwo groups of male chickens were fed either a control diet (group N) containing a standard poultry ration admixed with 10% corn oil or a cholesterol diet (group C) in which the control diet was supplemented with 1% cholesterol. After 6 weeks on the diets, a negligible amount of very low density lipoprotein (VLDL) was found in the serum from control animals. On the other hand, the serum VLDL from the cholesterol‐fed birds was the predominant lipoprotein and carried 72% of the total serum lipids. Surprisingly this lipoprotein from cholesterol‐fed animals was very low in triglycrides (6%) and high in total cholesterol (77%). While the level of serum low density liporotein was unaffected by the ingestion of cholesterol, the concentration of total lipids and phospholipids in the high density lipoprotein decreased in cholesterol‐fed animals. The greatest change in liver lipids from animals fed cholesterol was found in the cholesterol esters, whereas the unesterified cholesterol, triglyceride and phospholipid varied slightly or remained constant. In normal animals the distribution of cholesterol between the liver and the serum was about equal, whereas in the cholesterol‐fed birds the liver accounted for 80% of the cholesterol found in the liver‐serum pool. In order to determine how the hypercholesterolemic bird responds to the withdrawal of cholesterol from the ration, a diet‐exchange experiment was conducted. In this study the birds that were originally fed the cholesterol diets (group C) for 6 weeks were placed on the control diet (group CN) and the birds fed the control diet (group N) for 6 weeks were given the cholesterol diet (group NC). At periodic intervals, 1, 3, 7 and 14 days following the change of diets, 3–5 animals from each group were sacrificed, and analyses performed on their serum lipoproteins and liver lipids. Within one day after the diet substitution, there was a 31‐fold increase and a 46% decrease, respectively, in the serum VLDL concentration in groups NC and CN as compared with their corresponding steady state values (groups N and group C, respectively). The liver cholesterol increased 4‐fold and decreased 40%, respectively, in the two groups NC and CN as compared with the values obtained before the diet substitution. It is suggested that the concentration of cholesterol in the liver is the principal factor controlling cholesterol metabolism in chickens fed a hypercholesterolemic diet.