Studies of women eating diets with different fatty acid composition. III. Fatty acids and prostaglandin synthesis by platelets and cultured human endothelial cells.

The aim of this study was to determine how plasma fatty acids (FA) of subjects eating either a diet designed to match the US diet consumed in 1974 in fat content and composition in accord with the HANES I survey (US74) or a diet modified to meet the US Dietary Goal Recommendations (MOD) are altered, and how the changes affect platelet thromboxane (TXB2) synthesis, and prostacyclin (PGI2) and prostaglandin E2 (PGE2) synthesis by cultured human endothelial cells. Following a period of recorded self-selected diets, 10 women ate the US74 diet for 4 weeks, changing to the MOD diet for the next 4 weeks (sequence 1), and 10 ate the MOD diet followed by the US74 diet (sequence 2). Plasma triglycerides, free FA, platelet FA composition, and red blood cell phospholipids responded to the change from self-selected to controlled diets, but differences in responses were not seen between US74 and MOD diets. Red blood cell total FA did not respond to dietary changes. Under collagen but not thrombin stimulation, platelet TXB2 synthesis was correlated with platelet arachidonate concentration but not serum cholesterol. Endothelial cells were isolated from umbilical cord veins and incubated for 72 hours with a 20% medium of the women's plasma. In sequence 1 (high saturated FA to high polyunsaturated fatty acids), but not in 2 (reverse order), plasma from subjects eating the MOD diet decreased (p less than 0.05) basal and thrombin-stimulated PGI2 and PGE2 synthesis by the cells. These cells had a higher content of linoleic acid than cells from subjects eating the US74 diet. Thus, our study suggests that an increase in the intake of linoleic acid from 4.8 to 7.6 en% decreases PGI2 and PGE2 synthesis by human endothelial cells, and supplementation of the diet with linoleic acid has a longer period of effectiveness than its decrease in the diet.