Effects of dietary gamma-linolenate supplementation on serum lipids and platelet function in insulin-dependent diabetic patients.

In order to gain insight into the mechanism of platelet dysfunction in insulin-dependent diabetics we studied in 17 patients the influence of a 6-week period with a dietary supplement of gamma-linolenate: 2 g/d (group I, n = 8) or 500 mg/d (group II, n = 9). Serum lipids, plasma beta-thromboglobulin (beta TG), platelet aggregation in vitro, and TxB2 and PGE1 released from platelets during the aggregation process were measured. In group I, serum triglycerides fell from 1.57 +/- 0.28 mmol/l to 0.99 +/- 0.17 mmol/l (P less than 0.01) and cholesterol fell from 5.85 +/- 0.55 mmol/l to 5.08 +/- 0.52 mmol/l (P less than 0.01). In group I plasma beta TG fell from 100.0 +/- 15.7 ng/ml to 73.7 +/- 12.1 ng/ml (P less than 0.025), while the sum of the percentages of the C18:3 omega 6 and its chain elongated (C20:3 omega 6) and desaturated (C20:4 omega 6) metabolites increased in serum triglycerides (P less than 0.05), cholesterol esters (P less than 0.02) and phospholipids (P less than 0.02). No changes were observed on the other parameters in either group. The results show that the lowering effects of gamma-linolenate on serum triglycerides, cholesterol and plasma beta TG occur only with daily intakes of 2 g. The changes in fatty acid composition of serum lipids suggest that the gamma-linolenate intake of 2 g may exert its beneficial effect through an increased incorporation of long-chain polyunsaturated fatty acids, but no firm conclusion can be drawn as membrane platelet fatty acid composition was not evaluated.