Effects of fish oil on VLDL triglyceride kinetics in humans.

Dietary n-3 fatty acids (FAs) found in fish oils markedly lower plasma triglyceride (TG) and very low density lipoprotein (VLDL) levels in both normal and hypertriglyceridemic subjects. The present study examined the mechanism of this effect. Ten subjects with widely different plasma triglyceride levels (82 to 1002 mg/dl) were fed metabolically controlled diets containing 20% fat. The control diet contained a blend of cocoa butter and peanut oil (P/S = 0.8). The test diet contained fish oil (P/S = 1.1) and provided 10-17 g of n-3 FAs per day (depending on calorie intake). After 3 to 5 weeks of each diet, the kinetics of VLDL-TG were determined over a 48-h period after the injection of [3H]glycerol. The fish oil diet reduced the VLDL-TG synthetic rate from 23 +/- 14.3 (mean +/- SD) to 12.6 +/- 7.5 mg/h per kg ideal weight (P less than 0.005) and increased the fractional catabolic rate (FCR) for VLDL-TG from 0.23 +/- 0.12 to 0.38 +/- 0.16 h -1 (P less than 0.005). At the same time, there was a 66% reduction of plasma triglyceride levels, resulting largely from a 78% decrease in VLDL-TG levels (398 +/- 317 to 87 +/- 77 mg/dl; P less than 0.005). There was a strong correlation (r = 0.83; P less than 0.01) between the change in synthetic rates and pool sizes, but there was no correlation (r = 0.24; NS) between changes in FCRs and pool sizes. The VLDL cholesterol: triglyceride ratio increased during the n-3 diet suggesting that smaller VLDL particles were present. These particles would be expected to leave the VLDL fraction more rapidly than larger particles producing a higher FCR. We conclude that the hypotriglyceridemic effect of fish oil appears to be caused primarily by an inhibition of very low density lipoprotein-triglyceride synthesis, but an additional, independent effect upon VLDL catabolism cannot be ruled out.

Fish oils in hypertriglyceridemia: a dose-response study.

The effects of three supplemental doses of fish oil on plasma lipids, lipoproteins, and bleeding times were studied in ten hypertriglyceridemic patients. After a 3-wk baseline period each patient was given 15, 25, or 40 mL fish oil/d (containing 4.5, 7.5, and 12 g n-3 fatty acids) for three successive 6-wk periods, each separated by a 4-wk period of no supplementation. Plasma cholesterol concentrations decreased from 7.40 mmol/L to 6.35, 6.55, and 6.40 mmol/L with increasing doses of fish oil (p less than 0.01 vs baseline for each). Plasma triglyceride concentrations decreased from 6.10 mmol/L to 2.90, 2.80, and 2.35 mmol/L (p less than 0.01 vs baseline for each). Low-density-lipoprotein cholesterol concentrations increased significantly (by 23% and 28%) with the two higher doses, respectively. Bleeding times increased only with the largest dose. The lowest dose was the most hypolipidemic per gram n-3 fatty acids.

Reduction of plasma lipids, lipoproteins, and apoproteins by dietary fish oils in patients with hypertriglyceridemia.

Dietary fish oils, which are rich in omega-3 fatty acids, have been reported to reduce plasma lipid levels in normolipidemic subjects. We examined the effects of fish oil in 20 hypertriglyceridemic patients: 10 with Type IIb hyperlipidemia and 10 with Type V. These patients were put on three diets differing primarily in fatty acid composition and fat content. The control diet contained a fatty acid mixture typical of a low-fat therapeutic diet (ratio of polyunsaturated to saturated fat, 1.4), the fish-oil diet contained omega-3 fatty acids, and the vegetable-oil diet was rich in the omega-6 fatty acid, linoleic acid. Each diet was followed for four weeks. In the Type IIb group, the fish-oil diet led to decreases in both plasma cholesterol (-27 per cent) and triglyceride (-64 per cent), as compared with the control diet. Very-low-density lipoproteins (VLDLs) were also reduced markedly. The vegetable-oil diet had much less effect. With fish oil, the Type V group had marked decreases in total cholesterol and triglyceride levels (-45 and -79 per cent, respectively). VLDL levels were dramatically lowered, as were apoprotein E levels. The vegetable-oil diet (unlike the fish-oil diet) produced a rapid and significant rise in plasma triglyceride levels. We conclude that fish oils and fish may be useful components of diets for the treatment of hypertriglyceridemia.