Cholesterol homeostasis of skin fibroblasts after incubation with postabsorptive and postprandial lipoproteins. The effect of a fatty meal.

To determine if lipoproteins formed after a fatty meal deliver more cholesterol to cultured skin fibroblasts than do lipoproteins in the basal state, very low density lipoproteins and remnants (d less than 1.019), low density lipoproteins (LDL), and high density lipoproteins (HDL) were isolated from plasma obtained before, and 3 and 6 hours after, consumption of a high fat-cholesterol formula by seven normal males. Binding of 125I-LDL to cells and cell cholesterol content were determined after incubation of normal human skin fibroblasts for 48 hours with the lipoprotein fractions at 5% or 15% of plasma concentration. Activity of 3-hydroxy-3-methylglutaryl coenzyme A reductase was also measured after preincubation of cells with HLD for 48 hours. Despite a 40% increase in unesterified cholesterol in the d less than 1.019 fraction at 3 hours compared to the 0-hour fraction, the 3-hour d less than 1.019 fraction did not decrease LDL binding or increase cell cholesterol more than did the 0-hour fraction. Preincubation of cells with LDL, concentrations of which were unchanged by feeding, decreased LDL binding and increased cellular cholesterol. These effects also were not altered by the meal. HDL lipids and apo A-I were decreased at 3 hours, but not at 6 hours. Effects of HDL on LDL binding and cellular cholesterol were not altered by feeding, but the 3-hour and 6-hour fractions increased 3-hydroxy-3-methylglutaryl coenzyme A reductase activity, while the 0-hour fraction had little effect. These data indicate that consumption of a high fat-cholesterol meal as a bolus does not acutely alter the cholesterol delivery capacity of serum lipoproteins of normal male subjects.