Non-methylene-interrupted polyunsaturated fatty acids: Effective substitute for arachidonate of phosphatidylinositol

In mammalian tissues and cells, a characteristic of phosphatidylinositol (P I) is a high abundance of arachidonic acid (AA) relative to the other phosp holipids, In this study, we investigated the effects of supplementation of several polyunsaturated fatty acids (PUFAs) on the AA concentration of the PI fraction using a cultured cell system. Neither alpha-linolenic acid nor eicosapentaenoic acid supplement reduced the level of AA in PI of HepG2 cel ls. In contrast to the n-3 series PUFAs, adding podocarpic acid (20:3, Delt a-5,11,14) and pinolenic acid (18:3, Delta-5,9,12) reduced the AA content o f the PI fraction from a control value of 15.9% to 7.0 and 8.7%, respective ly. In the experiments with pinolenic acid, selective and significant accum ulation of 20:3 (Delta-7,11,14), the chain-elongated metabolite of pinoleni c acid, was observed in the PI fraction. On the other hand, adding columbin ic acid (18:3, Delta-5t,9,12) had no effect on AA content of the PI fractio n. Because both podocarpic acid and pinolenic acid are non-methylene-interr upted fatty acids (NMIFAs) that are not converted to AA metabolically, thes e NMIFAs may be interesting experimental tools for research on the function of PI-origin bioactive lipids. (C) 1999 Academic Press.