IMPACT OF HYDROGENATED FAT CONSUMPTION ON ENDOGENOUS CHOLESTEROL-SYNTHESIS AND SUSCEPTIBILITY OF LOW-DENSITY-LIPOPROTEIN TO OXIDATION IN MODERATELY HYPERCHOLESTEROLEMIC INDIVIDUALS

The effects of replacing corn oil with corn oil margarine in stick for m on endogenous cholesterol synthesis and susceptibility of low densit y lipoprotein (LDL) to oxidation were assessed in 14 middle-aged and e lderly men and women aged 63 +/- 12 years (mean +/- SD) with moderate hypercholesterolemia (mean LDL-cholesterol [LDL-C], 4.24 +/- 0.59 mmol /L at the time of recruitment). Subjects consumed each of two diets fo r 32 day periods, one enriched in corn oil, which contained 30% of ene rgy as fat (7% saturated fatty acid [SFA], 9% monounsaturated fatty ac id [MUFA] [0.4% 18:1n9 trans], and 11% polyunsaturated fatty acid [PUF A]) and 85 mg cholesterol/4.2 MJ, and one enriched in stick corn oil m argarine, which contained 30% fat (8% SFA, 12% MUFA [4.2% 18:1n9 trans ], and 8% PUFA) and 77 mg cholesterol/4.2 MJ. Both diets were isocalor ic and supplied by a metabolic research kitchen. Mean total cholestero l levels were lowest (P = .039) when subjects consumed the corn oil-en riched diet (5.01 +/- 0.51 mmol/L) as compared with the margarine enri ched diet (5.30 +/- 0.58 mmol/L). LDL-C levels were 3.24 +/- 0.51 and 3.50 +/- 0.54 mmol/L when subjects consumed corn oil- and margarine-en riched diets, respectively (P = .058). There were no significant diffe rences in high-density lipoprotein cholesterol (HDL-C) or triglyceride concentrations between the two experimental periods. Consumption of t he margarine enriched diet versus the corn oil-enriched diet tended to result in lower cholesterol fractional synthetic rates ([C-FSRs] 0.04 66 +/- 0.0175 and 0.0668 +/- 0.0298, respectively, P = .080) and chole sterol absolute synthetic rates ([C-ASRs] 1.1761 +/- 0.5375 and 1.6954 +/- 0.8685, respectively, P = .092); however, differences did not rea ch statistical significance. Consumption of the margarine enriched die t versus the corn oil-enriched diet resulted in a significantly higher concentration of alpha-tocopherol in both plasma and LDL (P = .004 an d P = .011, respectively). LDL particle size tended to be smaller afte r subjects consumed the margarine enriched diet versus the corn oil-en riched diet (P = .103). Susceptibility of LDL to oxidation was similar after consumption of the corn oil- and margarine-enriched diets. Thes e data Suggest that an increased rate of endogenous cholesterol synthe sis did not contribute to the higher plasma cholesterol concentrations during the period when subjects consumed the margarine enriched diet. Therefore, the increase in cholesterol concentration resulting from m argarine consumption was likely attributable, at least in part, to a d ecreased catabolic rate of cholesterol. Additionally, susceptibility o f LDL to in vitro oxidation was not altered by consumption of hydrogen ated fat. (C) 1996 by W.B. Saunders Company