HYPERLIPIDEMIC EFFECTS OF TRANS-FATTY-ACIDS ARE ACCENTUATED BY DIETARY-CHOLESTEROL IN GERBILS

Trans isomers of dietary fatty acids, generated during the commercial hydrogenation of unsaturated fats, may contribute to coronary heart di sease (CHD) in humans by interfering with lipid metabolism. To examine this possibility in a fat-sensitive model, the Mongolian gerbil (Meri ones unguiculatus) was used to compare the cholesterolemic and triglyc eridemic potential of modest increments of trans fatty acids from part ially hydrogenated soybean oil with other saturated fatty acids in the presence and absence of dietary cholesterol. Age-, dose-, and time-de pendent effects were examined in weanling, 6-month-old, and 1-year-old gerbils. Although lipoprotein metabolism in weanling gerbils was init ially refractory to trans fat, even as perturbations by saturated fatt y acids were demonstrable, these gerbils eventually (after 16 weeks) d eveloped a trans-induced hypercholesterolemia that was intermediate be tween the response to 16:0 and 12:0 + 14:0. The hepatic and plasma 18: 1/18:2 cholesteryl ester (CE) ratio was depressed by trans in a manner similar to saturated fatty acids. The 6-month-old gerbils readily dev eloped hypertriglyceridemia but not hypercholesterolemia, again reveal ing a decrease in the plasma 18:1/18:2 CE ratio. The 1-year-old gerbil s revealed a dose-related (0, 5, 10%en as trans) elevation in total ch olesterol (TC), and especially triglycerides (TG), that was accentuate d by 0.04% dietary cholesterol. Increases in plasma lipids were again accompanied by a significant decrease in the mass of hepatic esterifie d cholesterol, particularly 18:1-cholesteryl esters. Thus, dietary tra ns-fatty acids induce age-, time-, and dose-dependent modulations in g erbil plasma lipids associated with decreased 18:1 cholesteryl esters. Further investigation with gerbils may reveal mechanisms by which tra ns fat consumption disturbs lipoprotein metabolism.