Dietary trans fatty acids increase hepatic acyl-CoA: Cholesterol acyltransferase activity in hamsters

The objective of this study was to examine the effect of dietary trans fatt y acids (TFA) on cholesterol metabolism. Although TFA are unsaturated fatty acids, their spatial configuration and physical properties are similar to saturated fatty acids (SFA). In this study, a high TFA diet (12%) was given to hamsters for 4 weeks. Hamsters fed diets high in SFA (12%) and polyunsa turated fatty acids (PUFA) (12%) served as controls. Serum lipid profiles a nd the activity of a cholesterol ester synthesis enzyme, hepatic acyl-CoA: cholesterol acyltransferase (ACAT), were analyzed. Total cholesterol levels of TFA-fed and SFA-fed hamsters were 11.7% and 27.4% higher, respectively, than PUFA-fed hamster group (P<0.001). LDL-cholesterol levels of TFA-fed a nd SFA-fed hamsters were 41.0% and 73.9% higher, respectively, than PUFA-fe d hamster group (P<0.023). The activities of ACAT were significantly greate r in the SFA-fed group and TFA-fed group (812.8 and 723.48 pmol.min(-1).mg protein(-1)) compared to the PUFA-fed group (358.76 pmol.min(-1).mg protein (-1)). Findings of this study confirmed the cholesterol-raising effect of T FA, but more importantly, they indicated the possible mechanism of such an effect. Since hepatic ACAT activities were greater among the groups that re ceived diets high in TFA and SFA, this enzyme activity may depend on fatty acid substrate spatial configuration rather than on chain saturation. It is possible that dietary TFA increases hepatic ACAT activity and, thus, raise s serum cholesterol levels. (C) 2000 Elsevier Science Inc.