Impact of hydrogenated fat on high density lipoprotein subfractions and metabolism

Relative to saturated fatty acids, trans-fatty acids/hydrogenated fat-enric hed diets have been reported to increase low density lipoprotein (LDL) chol esterol levels and either decrease or have no effect on high density lipopr otein (HDL) cholesterol levels. To better understand the effect of trans-fa tty acids/hydrogenated fat on HDL cholesterol levels and metabolism, 36 sub jects (female, n = 18; male, n = 18) were provided with each of three diets containing, as the major sources of fat, vegetable oil-based semiliquid ma rgarine, traditional stick margarine, or butter for 35-day periods. LDL cho lesterol levels were 155 +/- 27, 168 +/- 30, and 177 +/- 32 mg/dl after sub jects followed the semiliquid margarine, stick margarine, and butter-enrich ed diets, respectively. HDL cholesterol levels were 43 +/- 10, 42 +/- 9, an d 45 +/- 10 mg/dl, respectively. Dietary response in apolipoprotein (apo) A -I levels was similar to that in HDL cholesterol levels. HDL2 cholesterol l evels were 12 +/- 7, 11 +/- 6, and 14 +/- 7 mg/dl, respectively. There was virtually no effect of dietary fat on HDL3 cholesterol levels. The dietary perturbations had a larger effect on particles containing apoA-I only (Lp A -I) than apoA-I and A-II (Lp A-I/A-II). Cholesterol ester transfer protein (CETP) activity was 13.28 +/- 5.76, 15.74 +/- 5.41, and 14.35 +/- 4.77 mmol X h(-1) X ml(-1), respectively. Differences in CETP, phospholipid transfer protein activity, or the fractional esterification rate of cholesterol in HDL did not account for the differences observed in HDL cholesterol levels. These data suggest that the saturated fatty acid component, rather than th e trans- or polyunsaturated fatty acid component, of the diets was the puta tive factor in modulating HDL cholesterol response.