This study investigated whether an ethyl ester preparation of fish oil (ω-3) could normalise raised plasma concentrations of triglycerides, apolipoprotein CIII on apolipoprotein B-containing particles (LP CIII:B) found in patients with recent acute myocardial infarction. We also studied the effect of fish oil on antithrombin III levels. Out of 75 patients with a plasma triglyceride value ≥2.0 mmol/L, 22 normalised their triglycerides during diet and were therefore not randomised. The remaining patients were randomly assigned to 12 weeks’ treatment with a daily dose of 4g ω-3 or placebo. Mean plasma triglyceride concentrations were reduced by 24% from 3.10 ± 1.15 (SD) to 2.53 ± 0.94 mmol/L (p < 0.001) on ω-3 (p < 0.001 vs placebo). The reduction was due to decreases in very low density lipoprotein concentrations. Total apolipoprotein CIII decreased significantly. This was due to reductions in LP CIII:non B concentrations, but the ratio LP CIII:non B/LP CIII:B was unaffected because of a slight insignificant decrease in LP CIII:B. The plasma triglyceride decreasing effect of ω-3 could therefore not be due to redistribution of CIII between lipoproteins. Low density lipoprotein (LDL) cholesterol increased significantly with ω-3 by 7%, and anti-thrombin III increased significantly with fish oil.
In conclusion, ω-3 had a moderate plasma triglyceride lowering effect and increased LDL cholesterol slightly, while antithrombin III increased in patients with hypertriglyceridaemia who had recently experienced a myocardial infarction.