Tracer kinetic studies on a methionine-supplemented soy-based infant formula using 1-13C- and 15N-methionine as tracers.
A tracer-kinetic study using 1-13C- and 15N-labeled L-methionine was conducted in order to measure the retention rate of free methionine added to commercially-produced soy-based infant formulas. Twelve male infants, fed on a soy formula, received a single-pulse labeling by oral administration of L-1-13C-methionine (5 mg/kg) and L-15N-methionine (10 mg/kg). The abundance of expired 13C-labeled CO2 was measured up to 7 h after administration at 15-, 30-, and 60-min intervals. Additionally, enrichment of total 15N and 15N in urinary ammonia were determined up to 48 h after administration. Retention rates of the labeled carboxyl group amounted to an average of 91.2% (SD 4.1) of the intake. A similar retention rate was measured for the 15N-label of methionine (90.0%, SD 4.3). The data point at the efficacy of methionine supplementation of soy-based infant formulas.
D000641:Ammonia / Q000652:urine; D001944:Breath Tests; D002245:Carbon Dioxide / Q000032:analysis; D002247:Carbon Isotopes; D006801:Humans; D007223:Infant; D007225:Infant Food; D007231:Infant, Newborn; D007700:Kinetics; D008297:Male; D008715:Methionine / Q000008:administration & dosage* / Q000378:metabolism*; D009587:Nitrogen Isotopes; D014674:Plant Proteins, Dietary; D030262:Soybean Proteins
D002247:Carbon Isotopes; D009587:Nitrogen Isotopes; D014674:Plant Proteins, Dietary; D030262:Soybean Proteins; D002245:Carbon Dioxide; D000641:Ammonia; D008715:Methionine