EFFECTS OF SATURATED FATTY-ACIDS ON N-6 FATTY-ACID METABOLISM IN CULTURED HUMAN MONOCYTE-LIKE CELLS (U937)

Effects of supplementation of saturated fatty acids (16: 0 and 18: 0) on metabolism of the cytotoxic n-6 fatty acids in cultured human monoc yte-like cells (U937) have been examined. U937 cells were incubated in 5% delipidated fetal bovine serum containing 16: 0 and 18: 0. Supplem entation of either 16: 0 or 18: 0 has no significant effect on the upt ake of 18: 2n-6 and 18: 3n-6. However, addition of 16: 0 to the medium increased whereas 18: 0 suppressed the cytotoxic effects of 18: 2n-6 and 18: 3n-6. In addition, 16: 0 supplementation reduced the incorpora tion of n-6 fatty acids in cellular phospholipid fraction, and enhance d the metabolism of n-6 fatty acids, particularly the conversion of 20 : 3n-6 to 20: 4n-6 in U937 cells. Results with microsomes prepared fro m U937 cells also showed that 16: 0 supplementation increased the DELT A5 desaturase activity. This may be related in part to an increase in the availability of 20: 3n-6, since results obtained in a separate stu dy have shown that 16: 0 competed with 20: 3n-6 for incorporaton into the phospholipid molecule at sn-2 position. Increasing the availabilit y and formation of long chain n-6 fatty acids, which are cytotoxic, mi ght also be responsible for increasing cytotoxicity of 16: 0 supplemen tation.