Dietary fish oil increases conversion of very low density lipoprotein apoprotein B to low density lipoprotein

Dietary fish oils, which are rich in omega-3 fatty acids, are known to produce a marked lowering of very low density lipoprotein (VLDL) triglyceride concentrations, but they have a less marked effect on low density lipoprotein (LDL) cholesterol. Our previous apolipoprotein (apo) B kinetic studies in miniature pigs demonstrated that conversion of VLDL apo B to LDL apo B accounted for 15% to 20% of total VLDL apo B catabolism. In addition, 75% to 80% of LDL apo B was derived independent of plasma VLDL or intermediate density lipoprotein (IDL) apo B catabolism. The present studies were carried out to determine if fish-oil diets influenced: 1) the conversion of VLDL to LDL, and 2) the pathways of LDL apo B synthesis. Autologous 125I-VLDL and 131I-LDL were injected into four pigs after both a corn-oil (30 g/day for 18 days) and a Maxepa (30 g/day for 18 days) dietary period. Analysis of apo B specific activity curves demonstrated that fish oil reduced the VLDL pool size by 38% (p less than 0.05) due to an increase in fractional catabolic rate (0.83 +/- 0.13 vs. 0.48 +/- 0.03 hr-1), as the synthesis rate was unaffected. However, the proportion of VLDL apo B converted to LDL increased significantly (56 +/- 7% vs. 17 +/- 3%, p less than 0.01) whereas the proportion cleared directly decreased (46 +/- 5% vs. 83 +/- 3%, p less than 0.005). Fish oil reduced total LDL apo B synthesis (0.6 +/- 0.1 vs. 1.1 +/- 0.2 mg/hr/kg, p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)