Fatty acid modification of cells in culture by overexpression of exogenous desaturases

COS-1 cells were transfected transiently with expression vectors encoding stearoyl-acyl-carrier-protein desaturase (SACPD) from castor bean, stearoyl-CoA desaturase (SCD) from mice, and a control vector containing SACPD cDNA in reverse orientation. The hypothesis was that both exogenous desaturases would be active in COS-1 cells, thereby increasing the proportion of monounsaturated fatty acids produced by the cells. Messenger RNA and anti-myc immunoreactive proteins were detected at 12 and 24 hours post-transfection respectively and increased through 48 hours post-transfection. When acetate was used as the fatty acid precursor in cultures for a 24-hour period starting 24 hours post-transfection, the ratio of monounsaturated to saturated fatty acids was increased by 1.8- and 1.6-fold for 16 and 18 carbon acids, respectively, in the cells expressing SCD (P \u3c .05) relative to SACPD-expressing cells and control cells, which did not differ from each other. Increased proportions of specific monounsaturated acids (16:1 and 18:1) were synthesized in cells expressing SCD (P \u3c .05), relative to SACPD-expressing and control cells. Control cells were usually numerically intermediate in total fatty acid desaturase activity compared with SCD- and SACPD-expressing cells. The presence of additional SCD increases the fatty acid desaturase capacity of cells, whereas SACPD is not active in mammalian cells