Non-insulin-dependent diabetes mellitus (NIDDM) is associated with elevated very-low-density lipoprotein (VLDL) triglyceride concentrations and abnormalities of low-density lipoprotein (LDL) composition. Because fish oil supplementation may favorably affect lipid and lipoprotein concentrations in nondiabetic subjects, we determined the effect of fish oil concentrate on plasma lipids and lipoprotein composition in patients with NIDDM. Dietary-supplementation 1-mo periods of 4.0 and 7.5 g of omega-3 fatty acids in fish oil were compared with a placebo of 12 g safflower oil by use of a single-blind crossover design. Medications, including antidiabetic therapy, were continued through the study. Compared with safflower oil treatment, fish oil supplementation resulted in a significant reduction of total plasma triglycerides of 24% at the 4-g doseand a larger reduction of 39% at the 7.5-g dose. These decreases were due to similar reductions in VLDL triglycerides. LDL cholesterol levels were mildly elevated, but a larger 20% increase in LDL apolipoprotein B (apoB) concentration was observed. During supplementation with the fish oil concentrate, the LDL cholesterol-to-apoB ratio was significantly reduced when compared with pretreatment values, but not when compared with safflower oil treatment. Highdensity lipoprotein (HDL) cholesterol and plasma apoA1 levels were not significantly changed during fish oil treatment. At the 7.5-g dose, fasting glucose and glycohemoglobin levels increased by 20 and 12%, respectively, but were unchanged at the lower level of supplementation. Thus, in NIDDM patients, dietary supplementation with omega-3 fatty acids induces a reduction in total plasma and VLDL triglyceride levels. However, the observed increase in LDL apoB levels, and the deterioration in glycemic control, indicate thatfurther study will be required to establish whether fish oil has a role in the treatment of NIDDM.

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