High density lipoprotein cholesteryl ester metabolism in the pony, an animal species without plasma cholesteryl ester transfer protein activity: transfer of high density lipoprotein cholesteryl esters to lower density lipoproteins and the effect of the amount of fat in the diet

The metabolism of high density lipoprotein cholesteryl esters (HDL CE) was studied in the pony, an animal species without plasma cholesteryl ester tra nsfer protein (CETP) activity. Studies were done in ponies fed a low- (1.5% fat, w/w) and a high-fat diet (11.5%, w/w fat). The ponies fed the high-fa t diet had higher plasma HDL CE concentrations (1.08 +/-0.15 vs. 0.84 +/-0. 11 mmol/l, mean +/- S.D., n=6, P<0.01) and plasma lipoprotein lipase (LPL) activities (14.3<plus/minus>4.0 vs. 5.7 +/-3.4 mu mol free fatty acids (FFA )/ml per h, P<0.05) than those on the low-fat diet. Plasma triacylglycerol (TAG) concentrations were lower on the high-fat diets (0.129<plus/minus>0.0 43 vs. 0.180 +/-0.050 mmol/l), but these differences were not statistically significant. There was a negative correlation between the levels of plasma TAG (r=0.598, P<0.05) and VLDL CE (r=0.658, P<0.05) on the one hand and th e HDL CE concentrations on the other hand. The transport rates of HDL CE we re not significantly different between ponies fed high-fat (0.029 +/-0.008 mmol HDL CE/h per 1 plasma) and those fed low-fat diets (0.024 +/-0.004). H DL CE were transferred to low density lipoproteins (LDL) and we calculated that the percentage of LDL CE derived from HDL was 0.69 +/-0.13 in the poni es fed the low-fat diet and 0.53 +/-0.05 in the ponies fed the high-fat die t (P<0.05). The results of these in vivo studies suggest that in ponies, si milarly as reported in rats and pigs, HDL CE can be transferred to LDL desp ite the absence of plasma CETP activity, and that the magnitude of this tra nsfer is related to the levels of HDL CE as induced by the amount of fat in the diet. (C) 2001 Elsevier Science Inc. All rights reserved.