Dietary corn oil versus olive oil enhances HDL protein turnover and lowers HDL cholesterol levels in hamsters

We studied the effect of dietary olive and corn oil on high-density lipoprotein (HDL) metabolism in golden Syrian hamsters. The animals were fed a semipurified diet containing 0.1% cholesterol and 40 energy % in the form of either olive or corn oil for a period of nine weeks. Hamsters fed corn oil had significantly lower very-low density and low-density lipoprotein (VLDL+LDL) cholesterol concentrations than those fed olive oil (0.98±0.24 vs. 1.40±0.34 mmol/l, means±S.D.,n=12), as well as significantly lower HDL cholesterol concentrations (3.31±0.50 vs. 3.91±0.12 mmol/l). The binding capacity of 125I-labelled HDL to liver membranes was 33% higher in the hamsters fed corn oil instead of olive oil (571±29 vs. 429±24 ng HDL protein/mg membrane protein, P<0.05, n=4). HDL protein kinetics were studied with 125I-HDL using a constant infusion technique. Both HDL fractional catabolic rate (0.255±0.058 vs. 0.121±0.023 /h, P<0.01, n=5) and transport rate (2.386±0.753 vs. 1.218±0.101 mg/h, P<0.01, n=5) were about 2-fold higher in the hamsters fed corn oil. The rate of plasma cholesterol esterification by lecithin: cholesterol acyltransferase (LCAT) was essentially the same for the two diets. It is concluded that the low HDL level in the hamsters fed corn oil diets is linked with increased HDL binding and degradation in the liver and possibly other tissues. Due to increased HDL protein turnover, the capacity for reverse cholesterol transport is increased in hamsters fed corn oil despite the relative low HDL concentrations