Compartmental analyses of plasma 13C- and 2H-labeled n-6 fatty acids arising from oral administrations of 13C-U-18:2n-6 and 2H5-20:3n-6 in newborn infants.
Efficacy of (13)C-U-18:2n-6 and (2)H(5)-20:3n-6 toward synthesis of labeled-20:4n-6 was studied in newborn infants utilizing compartmental models of plasma labeled n-6 fatty acids (FA). Ten infants received oral doses of (13)C-U-18:2n-6 and (2)H(5)-20:3n-6 ethyl esters (100 and 2 mg/kg, respectively). Rate constant coefficients and half-lives (t((1/2))) of n-6 FA were determined from the time-course concentrations of labeled-FA. Plasma n-6 FA values approximated steady state concentrations. Synthetic and utilization rates were calculated. Eight percent (range, 2-21%) of plasma (13)C-U-18:2n-6 was used for synthesis of (13)C-18:3n-6, -20:2n-6, and -20:3n-6. Seventy percent of (13)C-20:3n-6 (mean, CV: 0.26) was available for synthesis of (13)C-20:4n-6. The percentage of (2)H(5)-20:3n-6 converted to (2)H(5)-20:4n-6 was lower (mean: 26%, p < 0.02) than the (13)C-labeled analogue. Turnover of 18:2n-6 in subjects and of 20:4n-6 in plasma was 4.2 g/kg/d (CV: 0.58) and 4.3 mg/kg/d (CV: 0.81), respectively. Intake of 18:2n-6 and 20:4n-6 were estimated to be 3.0 g/kg/d (+/-1.7) and 2.8 mg/kg/d (+/- 2.2), respectively. Infants required additional 18:2n-6 and 20:4n-6 (mean: 1.2 g and 1.5 mg/kg/d) above predicted intake amounts to maintain plasma concentrations of 18:2n-6 and 20:4n-6, in order to spare FA from fat stores.
Pawlosky
Robert J
RJ
Laboratory of Metabolic Control, National Institutes on Alcohol Abuse & Alcoholism, National Institutes of Health, Bethesda, MD 20892, USA. bpawl@mail.nih.gov
Lin
Yu Hong
YH
Llanos
Adolfo
A
Mena
Patricia
P
Uauy
Ricardo
R
Salem
Norman
N
D015126:8,11,14-Eicosatrienoic Acid / Q000378:metabolism*; D002247:Carbon Isotopes; D003903:Deuterium; D004042:Dietary Fats, Unsaturated / Q000378:metabolism*; D043371:Fatty Acids, Omega-6 / Q000097:blood*; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D008297:Male
D002247:Carbon Isotopes; D004042:Dietary Fats, Unsaturated; D043371:Fatty Acids, Omega-6; D003903:Deuterium; D015126:8,11,14-Eicosatrienoic Acid