Significant utilization of dietary arachidonic acid is for brain adrenic acid in baboon neonates

Dietary arachidonic acid (20:4n-6) utilization in-vivo for carbon recycling into de-novo lipogenesis and conversion to n-6 long chain polyunsaturates was investigated in baboon neonates using [U-(13)C]20:4n-6. Neonates consuming a formula typical of human milk received a single oral dose of [(13)C]arachidonic acid in sn-2 position of either triglyceride or phosphatidylcholine at 18-19 days of postnatal life. Neonate brain, retina, liver, and plasma were obtained 10 days later (28-29 days of life). Low isotopic enrichment (0.27-1.0%Total label) was detected in dihomo-gamma-linolenic acid (20:3n-6) in all tissues, but label incorporation into saturates or monounsaturates was not detected. In neonate brain and retina, 16% and 11% of total label was recovered in 22:4n-6, respectively. The relative contribution of dietary fatty acids to postnatal brain 22:4n-6 accretion can be estimated for dietary 20:4n-6 and preformed 22:4n-6 as 17% and 8%, respectively, corresponding to efficiencies of 0.48% and 0.54% of dietary levels, respectively. These results demonstrate in term baboon neonates that in vivo 1) 20:4n-6 was retroconverted to 20:3n-6, 2) 20:4n-6 did not contribute significantly to de novo lipogenesis of saturates and monounsaturates, and 3) the preformed 20:4n-6 contribution to brain 22:4n-6 accumulation was quantitatively a significant metabolic fate for dietary 20:4n-6.