The effect of borage oil consumption on the composition of individual phospholipids in human platelets.

The effect of supplementation with borage oil containing gamma-linolenic acid (GLA, 18:3n-6) on the levels and fatty acid compositions of individual human platelet phospholipids was evaluated. For this purpose, male volunteers were given an average daily intake of 5.23 g of GLA (as borage oil) for 42 days, after which the supplement was withdrawn for an additional 42-day period. No significant differences were found in the relative amounts of the choline phospholipids (PC), ethanolamine phospholipids (PE), phosphatidylserine (PS), phosphatidylinositol (PI), and sphingomyelin (SPH) at days 0, 22, 43, 64, and 85. However, marked differences were observed in the fatty acid compositions of all the phospholipids including a marked, and reversible, rise in the level of dihomo-gamma-linolenic acid (DGLA, 20:3n-6), without a significant elevation in arachidonic acid (AA, 20:4n-6) and decreases in n-3 polyunsaturated fatty acids. In the case of PC, a net rise in DGLA of 1.8 mol% was observed by day 22 (from 2.1 to 3.9 mol%). The DGLA/AA ratios at day 43 exhibited considerable variability across phospholipids with PC greater than PS greater than PE = PI; the PC, PE, PS, and PI accounted for 67.6, 16.7, 12.9, and 2.6%, respectively, of the total DGLA in platelet phospholipids. Interestingly, despite the lack of DGLA in SPH, this phospholipid exhibited a marked enrichment in nervonic acid (NA, 24:1n-9) from 16.2 to 24.7 mol% upon borage oil consumption. The observed alterations may represent biochemical strategies for adaptation to dietary fatty acid modifications and the regulation of platelet membrane functioning.