Utilization of polyunsaturated fatty acids by human diploid cells aging in vitro.

Abstract

AbstractCultures of human diploid cell strain IMR‐90 were supplemented with γ‐linolenic acid, 18∶3ω6, by constant infusion over 72 hr. Cell growth was twice that observed when the same amount of fatty acid was supplied as a single dose at the start of a 72‐hr incubation. Using the infusion method, growth of cells receiving monoenoic or polyenoic fatty acids was compared. The age of these cells in vitro was measured in terms of the culture mean population doubling level (PDL). Population doubling level refers to the mean number of doublings elapsed since establishment of a primary culture. At PDL from 24–53, the growth of cells from cultures supplemented with oleic acid was similar to that of noninfused cultures. Gamma linolenic acid, 18∶3ω6, and to greater extent arachidonic acid, 20∶4ω6, however, caused suppression of cell multiplication at PDL≤32, but not at PDL≥44. The polyunsaturated fatty acid (PUFA) levels in cell phospholipids were reduced by exogenous oleic acid to half that of nonsupplemented cells at all PDL tested. Conversely, the PUFA levels in phospholipids were elevated by a factor of 1.6 at all PDL when cultures were infused with 18∶3ω6. Triglyceride levels at the end of 72 hr were similar, but much higher than the controls, regardless of the fatty acid supplied. Growth inhibition, modification of phospholipid acyl group content and triglyceride levels were not appreciably affected when the amount of monoenoic or polyenoic fatty acid infused into the cultures was doubled. The elongation of 18∶3, as well as the distribution of 18∶3 and its elongation products, between triglyceride and phospholipid, was dependent on whether the 18∶3 was of the ω3 or ω6 family.