Regulation of the metabolism of polyunsaturated fatty acids.

The object of the present work has been to assess some aspects of the control of the metabolism of polyunsaturated fatty acids. In these studies we have used isolated cells; hepatocytes and cardiac myocytes from rat, and lymphocytes and fibroblasts from humans. Attention has focused on the importance of dietary and hormonal factors which can exert an effect shortly after activation of fatty acid, and thus may determine whether the fatty acid will be desaturated, chain-elongated, directly esterified or oxidized. Both the short-term and long-term regulation excerted by dietary fat have been studied in both rat and human. Profound sex-differences exist in fatty acid esterification, oxidation and fatty acid composition in lipoproteins. It is suggested that these differences, at least in part are due to a different content of intracellular fatty acid binding proteins in female and male liver. The peroxisomal retroconversion of C22-unsaturated fatty acids to their C20-homologues is probably involved in the regulation of fatty acid composition in membrane phospholipids, being a sort of "overflow valve". In several somewhat different diseases the patients have no peroxisomes or their peroxisomes are defective. In these peroxisomal diseases the beta-oxidation of very long-chain fatty acids is deficient. In this present work we show that fibroblast from patients with the peroxisomal diseases, Zellweger disease, X-linked adrenoleukodystrophy and neonatal adrenoleukodystrophy differ in their ability to shorten C22-fatty acids.