FATTY-ACID TRANSPORT AND UTILIZATION FOR THE DEVELOPING BRAIN

To determine the transport and utilization of dietary saturated, monou nsaturated, and n-6 and n-3 polyunsaturated fatty acids for the develo ping brain and other organs, artificially reared rat pups were fed a r at milk substitute containing the perdeuterated (each 97 atom% deuteri um) fatty acids, i.e., palmitic, stearic, oleic, linoleic, and linolen ic, from day 7 after birth to day 14 as previously described. Fatty ac ids in lipid extracts of the liver, lung, kidney, and brain were analy zed by gas chromatography-mass spectrometry to determine their content of each of the deuterated fatty acids. The uptake and metabolism of p erdeuterated fatty acid lead to the appearance of three distinct group s of isotopomers: the intact perdeuterated, the newly synthesized (wit h recycled deuterium), and the natural unlabeled fatty acid. The quant ification of these isotopomers permits the estimation of uptake and de novo synthesis of these fatty acids. intact perdeuterated palmitic, s tearic, and oleic acids from the diet were found in liver, lung, and k idney, but not in brain, By contrast, perdeuterated linoleic acid was found in all these organs. Isotopomers of fatty acid from de novo synt hesis were observed in palmitic, oleic, and stearic acids in ail tissu es. The highest enrichment of isotopomers with recycled deuterium was found in the brain. The data indicate that, during the brain growth sp urt and the prelude to myelination, the major saturated and monounsatu rated fatty acids in brain lipids are exclusively produced locally by de novo biosynthesis. Consequently, the n-6 and n-3 polyunsaturated fa tty acids must be transported and delivered to the brain by highly spe cific mechanisms.