Effect of preeclampsia in the mother on the leucine metabolism in the newborn infant

The leucine turnover in newborn infants is influenced by factors such as nutritional state and corticosteroid treatment. Little is known about maternal factors influencing the leucine turnover in the newborn. In order to approach the effect of preeclampsia in the mother on neonatal protein turnover, we studied the leucine turnover in preterm infants soon after birth and again after 7 days. Ten infants from preeclamptic mothers (birth weight 1,280 +/- 240 g, gestational age 31 +/- 2 weeks) and 15 control patients (birth weight 1,320 +/- 210 g, gestational age 30 +/- 2 weeks) were enrolled. The leucine turnover was measured using a primed constant 5-hour intravenous infusion of [1-(13)C]leucine within the first 24 h after delivery and again on day 7 of life. The turnover (leucine flux; micromol.kg(-1).h(-1)) was calculated from the enrichment in alpha-ketoisocaproic acid in plasma. The leucine turnover on day 1 was 300 +/- 65 in the preeclampsia group and 358 +/- 70 in the controls (ANOVA, p < 0.05). The values on day 7 were 474 +/- 73 in the preeclampsia group and 485 +/- 80 in the control group (n.s.). To conclude, the leucine turnover on day 1 is lower in infants of preeclamptic mothers as compared with controls. This difference has disappeared on day 7 of life after receiving the same protein and energy intake

Cysteine: a conditionally essential amino acid in low-birth-weight preterm infants?

Cyst(e)ine can be synthesized de novo from methionine and serine and is, therefore, a nonessential amino acid in human adults. Several studies have suggested that cyst(e)ine might be a conditionally essential amino acid in preterm infants because of biochemical immaturity. No data are available on cyst(e)ine requirements in low-birth-weight (LBW) preterm infants. The aim was to determine cyst(e)ine requirements in LBW infants with gestational ages from 32 to 34 wk, measured 1 mo after birth with the use of the indicator amino acid oxidation technique. LBW infants were randomly assigned to 1 or 2 of the 5 formulas containing graded cystine concentrations (11, 22, 32, 43, or 65 mg cyst(e)ine/100 mL) and generous amounts of methionine. After 24-h adaptation, cyst(e)ine requirement was determined by (13)CO(2) release from [1-(13)C]phenylalanine in expired breath. (13)CO(2) enrichment was measured by isotopic ratio mass spectrometry. Cyst(e)ine requirement was determined in 25 LBW infants with a mean (+/-SD) gestational age of 33 +/- 1 wk and birth weight of 1.78 +/- 0.32 kg. Fractional oxidation of [1-(13)C]phenylalanine did not differ between the 5 groups. There is no evidence for limited endogenous cyst(e)ine synthesis in 4-wk-old LBW preterm infants born at gestational ages from 32 to 34 wk. It is safe to conclude that the cyst(e)ine requirement is <18 mg kg(-1) d(-1) providing generous amounts of methionine and that cyst(e)ine is probably not a conditionally essential amino acid in fully enterally fed LBW preterm infants born at 32-34 w