Dietary fat saturation distinctly affects apolipoprotein gene expression and high density lipoprotein size distribution in two strains of Golden Syrian hamsters

Abstract

Plasma lipoprotein levels, high density lipoprotein (HDL) particle size distribution and tissue mRNA levels for several apolipoproteins were determined in two strains of Golden Syrian hamsters characterized as high (F1B) or low (LVG) responders to atherogenic diets. Twenty-four male hamsters per strain were fed semipurified diets containing 0.2 g/100 g diet cholesterol and 15 g/100 g diet fat enriched (13 g/100 g) with either coconut oil or soybean oil for 18 weeks. HDL size was analyzed by non-denaturing gradient (4–30%) polyacrylamide gel electrophoresis, and categorized into four HDL subspecies according to Stoke’s diameter. Hepatic and intestinal mRNA apolipoprotein concentrations were measured using solution hybridization/ribonuclease protection assay. Compared to F1B hamsters, the LVG hamsters showed a less atherogenic lipoprotein profile; with lower triglycerides (P < 0.01) and higher HDL cholesterol (P < 0.01) levels. Consumption of a polyunsaturated fatty acid (PUFA) diet induced the decrease in triglyceride levels (42% in LVG, P < 0.05 and 51% in F1B, P < 0.01) and in HDL cholesterol (15% in LVG, P < 0.05 and 28% in F1B, P < 0.01). LVG animals had a greater proportion of larger HDL particles than F1B animals regardless of the diet (P < 0.01). Consumption of the soybean oil diet, compared with coconut oil diet, lowered the proportion of HDL2b and increased the proportion of HDL2a and HDL3 in LVG animals. However, F1B animals consuming the PUFA diet had a decrease in the percentage of HDL2b and HDL2a and a marked increase in HDL3. ApoA-I mRNA levels were higher in F1B animals (P < 0.01), and were not affected by dietary fat saturation in either strain of hamsters. ApoA-II mRNA levels were higher in the LVG strain (P < 0.001), and increased with fat saturation of both strains (P < 0.05). The average ratio of intestinal apoC-II/C-III mRNA was 3.2 times higher in LVG animals (P < 0.05) as compared with F1B animals. This is consistent with a higher lipolytic activity in LVG animals that will result in lower triglyceride concentrations and increased HDL particle size. Dietary induced effects on HDL particle size may be attributed to the higher levels of apoA-II mRNA as well as an increased neutral lipid exchange between HDL and triglyceride-rich lipoproteins due to the elevated triglyceride levels in animals fed on saturated diet.