LINOLEATE, ALPHA-LINOLENATE, AND DOCOSAHEXAENOATE RECYCLING INTO SATURATED AND MONOUNSATURATED FATTY-ACIDS IS A MAJOR PATHWAY IN PREGNANT OR LACTATING ADULTS AND FETAL OR INFANT RHESUS-MONKEYS

Carbon recycling and desaturation and elongation of linoleate, alpha-l inolenate and docosahexaenoate in ten fetuses and two nursing infants of chow-fed rhesus monkey mothers were studied in vivo using uniformly labeled tracer molecules and high precision mass spectrometry. Doses of [U-C-13]-18:2n-6, [U-C-13]-18:3n-3 or [U-C-13]-22:6n-3 free fatty a cids were infused intravenously to the adults, and milk, maternal plas ma, fetal plasma and tissues, and infant plasma were analyzed for enri chment in fatty acids of length C-14 to C-22. Conversion of tracer fat ty acids to palmitic, stearic, oleic, and long chain polyunsaturated f atty acids was observed in fetal liver, brain, and retina ca. 5 days a fter dosing, and in milk and infant plasma 1 and 7 days after dosing. Animals dosed with [U-C-13]-22:6n-3 accumulated more label in the feta l organs compared to the animals dosed with [U-C-13]-18:3n-3 or [U-C-1 3]-18:2n-6. The greatest fractions of doses were found in the fetal br ains at levels of 0.21%, 0.24%, and 1.7% for the [U-C-13]-18:2n-6, [U- C-13]-18:3n-3, and [U-C-13]-22:6n-3 dosed mothers, respectively. Label was found in saturated and. monounsaturated fatty acids in Liver, bra in and retina (0.05-1.5 ppm dose/mg lipid) for all doses. These result s demonstrate that 1) recycling of carbon from 18 :2n-6, 18 :3n-3, and 22:6n-3 into saturates and monounsaturates is a major metabolic pathw ay in chow-fed primates in the perinatal period; 2) less than 2% of th e n-3 doses are found in brain fatty acids of developing fetuses from chow-fed mothers; and 3) [C-13]- 22:6n-3 accumulates in retina and bra in at an order of magnitude higher level when provided as preformed [C -13]-22:6 n-3 compared to [C-13]-18: 3n-3.