Neonatal polyunsaturated fatty acid metabolism

The importance of n-6 and n-3 polyunsaturated fatty acids (PUFA) in neonata l development, particularly with respect to the developing brain and retina , is well known. This review combines recent information from basic science and clinical studies to highlight recent advances in knowledge on PUFA met abolism and areas where research is still needed on infant n-6 and n-3 fatt y acid requirements. Animal, cell culture, and infant studies are consisten t in demonstrating that synthesis of 22:6n-3 involves C24 PUFA and that the amounts of 18:2n-6 and 18:3n-3 influence PUFA metabolism. Studies to show that addition of n-6 fatty acids beyond Delta 6-desaturase alters n-6 fatty acid metabolism with no marked increase in tissue 20:4n-6 illustrate the l imitations of analyses of tissue fatty acid compositions as an approach to study the effects of diet on fatty acid metabolism. New information to show highly selective pathways for n-6 and n-3 fatty acid uptake in brain, and efficient pathways for conservation of 22:6n-3 in retina emphasizes the dif ferences in PUFA metabolism among different tissues and the unique features which allow the brain and retina to accumulate and maintain high concentra tions of n-3 fatty acids. Further elucidation of the Delta 6-desaturases in volved in 24:5n-6 and 22:6n-3 synthesis; the regulation of fatty acid movem ent between the endoplasmic reticulum and peroxisomes; partitioning to acyl ation, desaturation ana oxidation; and the effects of dietary and hormonal factors on these pathways is needed for greater understanding of neonatal P UFA metabolism.