Indirect evidence has suggested that long chain polyunsaturated fatty acids (LCPUFA) synthesis is insufficient for requirements in the newborn infant, and specially in the premature. We studied in vivo the elongation and desaturation of linoleic acid (LA) to arachidonic acid (ARA) and linoleic (LNA) to docosahexanoic acids (DHA). The infants received 50 mg/Kg of AL and ALN labeled with 5 atoms of deuterium during the first days of life before they were fed. The stable isotopes labeled metabolites (D5) released into plasma were detected in a blood sample taken 24, 48 and 96 hours after enteral dose of essential fatty acids. Lipids were extracted from plasma samples by Blight & Dyer methods and methylated by Morrison. The stable isotopes metabolites was determined with gas chromatography/mass spectrometry in a negative chemical ionization mode.

We report in this study 23 premature newborns (birth weight:2033g, gestational age : 32,5w), 8 term newborns (BW: 3557g, GA: 41,1w); 11 intrauterine growth retarded newborns (IUGR) (BW:1834g, EG: 35,6w). Table

Table 1 No caption available.
Full size table

The higher plasmatic levels of D5 essential fatty acids were present within 24 hours of the administration, but D5 ARA and D5DHS were higher at 48 hours in term infants and at 96 hours in preterm and IIGR. Results show a slower LCPUFA production in IUGR infants, compared with preterm and term indants, during the study period term and preterm infants without IUGR presented a higher amounts of D5LCPUFA production at lower gestational age. This can be explain, in part, because of lower amounts of non deuterated essential fatty acids at the basal level and a higher enrichment with deuterated precursors with the administered dose. (Fondecyt 1961001 y Cátedra Presidencial RU).