Polyenoic acid metabolism in cultured human skin fibroblasts

Abstract

The incorporation of [1-14C]linoleic acid, and [1-14C]linolenic acid into cellular lipids of cultured human skin fibroblasts was studied. Cultured cells took up both labeled fatty acids at nearly the same rate and incorporated them into a variety of lipid classes. At the end of 1 hr incubation with [1-14C]linoleic acid, radioactivity was found in the triacylglycerol (TG) and choline phosphoglyceride (CPG) pools preferentially. Incorporation into the TG fraction decreased rapidly, while the uptake into CPG, serine phosphoglyceride (SPG), and ethanolamine phosphoglyceride (EPG) fractions increased progressively with longer incubation times. Similar results were obtained with [1-14C]linolenic acid as precursor. At the end of 24 hr, desaturation and chain elongation of 18:3 n-3 was more extensive than conversion of 18:2 n-6 to higher polyenoic acids. During pulse-chase experiments with either fatty acid precursor, the incorporated radioactivity was progressively lost from cellular lipids, particularly from the TG and CPG fractions, but continued to increase in the SPG and EPG pools. The similar labeling pattern of cellular phospholipids with linoleic or linolenic acids, and data from pulse-chase studies suggest that a direct transfer of fatty acids from CPG to EPG is a likely pathway in fibroblast cultures. Incorporation into the EPG pool during the pulse-chase experiments paralleled extensive desaturation and elongation of linoleic acid to 20:4 n-6, and 22:4 n-6; and of linolenic acid into 22.5 n-3 and 22:6 n-3.

Activity and mRNA abundance of Δ‐5 and Δ‐6 fatty acid desaturases in two human cell lines

“…The uptake of PUFAs by these two cell lines was consistent with that observed in other mammalian cells in vitro [9,18]. The possibility of a di¡erent metabolic fate for each PUFA in Chang or ZR-75-1 cells due to a di¡erential intracellular fatty acid concentration is unlikely since all the fatty acids tested showed similar uptake in both cell lines.…”

Utilization of arachidonic and linoleic acids by cultured human endothelial cells.

“…These include the L-fibroblast (3), LM cell (3,4,23), HSDM fibrosarcoma (3), and Chang liver cell (4). However, a number of other cultured cells contain this activity, including mouse neuroblastoma (24), human skin fibroblasts (3,5), and human lung fibroblasts (3,4). Therefore, the A6-desaturase deficiency appears to be unrelated to the fact that the endothelial cells were cultured.…”

“…In mammals arachidonic acid is synthesized from linoleic acid, the most abundant polyunsaturated fatty acid usually present in the diet. A number of cultured cells, including human diploid fibroblasts, are able to convert linoleic to arachidonic acid (3)(4)(5). Those cultures that cannot perform this conversion are for the most part transformed rodent cell lines (3,4), and it has been suggested that the deletion of this capacity is somehow associated with malignant transformation (3).…”

Effects of various dietary n-3 / n-6 fatty acid ratios on the performance and body composition of broilers

“…Dietary α-linolenic acid (C18:3n-3) is not readily incorporated into tissue lipids. It is mainly oxidised to CO 2 and water (Aeberhard et al, 1978). Some is converted to EPA (C20:5n-3) and DHA (C22:6n-3), but only a small portion of the α-linolenic acid (C18:3n-3) enters this pathway (De Gomez-Dumm & Brenner, 1975).…”