Long-term effects of fish oil on lipoprotein subfractions and low density lipoprotein size in non-insulin-dependent diabetic patients with hypertriglyceridemia

The effects of fish oil on lipoprotein subfractions and low density lipoprotein (LDL) size in non-insulin-dependent diabetes mellitus (NIDDM) patients with hypertriglyceridemia are unknown. To elucidate this, 16 NIDDM hypertriglyceridemic patients (plasma triglyceride 2.25–5.65 mmol/l, plasma cholesterol ≤7.75 mmol/l) were randomly assigned to a 6-month period with either moderate amounts of fish oil (n=8) or placebo (n=8) after 4 weeks of wash-out and 3 weeks of run-in. Diet and hypoglycemic treatment were unchanged throughout the experiment. LDL size were evaluated at baseline and after 6 months. Three VLDL and LDL subfractions were measured at the end of the two periods. The total lipid concentration of all very low density lipoprotein (VLDL) subfractions was lower at the end of fish oil treatment compared with placebo (large VLDL 124.3±19.7 mg/dl vs 156.7±45.5 mg/dl; intermediate VLDL 88.5±9.5 mg/dl vs 113.9±23.2 mg/dl; small VLDL 105.9±9.7 mg/dl vs 128.9±40.7 mg/dl) (mean±SEM), although the difference was not statistically significant. Moreover, at the end of the two treatments, the percentage distribution of VLDL subfractions was very similar (large 37.5±3.3% vs 37.6±2.6%, intermediate 27.6±0.9% vs 31.0±2.4%; small 34.9±3.7% vs 31.4±2.1%). Concerning LDL, no significant change in LDL size was observed after the two treatments (255.4±2.2 Å vs 254.2±1.7 Å, fish oil; 253.7±2.0 Å vs 253.3±1.7 Å, placebo). LDL subfraction distribution was also very similar (large 17±3% vs 17±2%; intermediate 62±3% vs 65±3%; small 21±3% vs 18±2%), at the end of the two periods, confirming the lack of effects on LDL size. In conclusion, our study indicates that in NIDDM patients with hypertriglyceridemia, fish oil does not induce any improvement in LDL distribution and LDL size despite its positive effects on plasma triglycerides.