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Metabolism of 13C-Labeled Linoleic Acid in Newborn Infants During the First Week of Life

1999; Springer Nature; Volume: 45; Linguagem: Inglês

10.1203/00006450-199905010-00010

1530-0447

Peter Szitányi, Berthold Koletzko, A Mydlilová, Hans Demmelmair,

Fatty Acid Research and Health

Linoleic acid metabolism was studied during the first week of life in 10 breast-fed, full-term infants. Uniformly 13C-labeled linoleic acid (1 mg/kg body weight) was given orally. The 13C content was determined in expired CO2 over 6 h and in plasma phospholipid fatty acids over 3 d. Total CO2 production determined by indirect calorimetry was 16.7 ± 10.6 mL/min (mean ± SE). Over 6 h 7.4 ± 0.6% of the ingested 13C-labeled linoleic acid was oxidized to CO2. Plasma phospholipid linoleic acid showed maximal 13C enrichment 24 h after tracer application (delta over baseline 178 ± 24%‰). Enrichment of dihomo-γ-linoleic acid increased from d 2 to d 5 of life (p < 0.002), with delta over baseline values of 2.1 ± 0.5%‰ at 24 h, 3.7 ± 10.9%‰ at 48 h, and 4.4 ± 1.0%‰ at 72 h. 13C content of arachidonic acid tended to increase insignificantly. Areas under the curve of plasma tracer concentration over time were calculated for plasma n-6 phospholipid fatty acids. Percentages of total areas under the curve of the investigated n-6 fatty acids were 97.3 ± 0.8% for linoleic acid, 1.5 ± 0.6% for dihomo-γ-linolenic acid, and 1.2 ± 0.6% for arachidonic acid. The proportion of linoleic acid oxidized to CO2 did not correlate with the estimated conversion to long-chain polyunsaturated metabolites. Breast-fed newborn infants synthesize n-6 long-chain polyunsaturated fatty acids already during the first week of life, but the contribution of endogenous synthesis to the total plasma long-chain polyunsaturated pool is small. A major portion of dihomo-γ-linoleic acid is converted to arachidonic acid.