The initial growth and quality of nutrition were significantly associated with absolute FFM accretion during a hospital stay in preterm infants. This trial was registered at clinicaltrials.gov as NCT01450436.

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Background and AimsHuman breast milk is an extremely dynamic fluid containing many biologically-active components which change throughout the feeding period and throughout the day. We designed a miRNA assay on minimized amounts of raw milk obtained from mothers of preterm infants. We investigated changes in miRNA expression within month 2 of lactation and then over the course of 24 hours.Materials and MethodsAnalyses were performed on pooled breast milk, made by combining samples collected at different clock times from the same mother donor, along with time series collected over 24 hours from four unsynchronized mothers. Whole milk, lipids or skim milk fractions were processed and analyzed by qPCR. We measured hsa-miR-16-5p, hsa-miR-21-5p, hsa-miR-146-5p, and hsa-let-7a, d and g (all -5p). Stability of miRNA endogenous controls was evaluated using RefFinder, a web tool integrating geNorm, Normfinder, BestKeeper and the comparative ΔΔCt method.ResultsMiR-21 and miR-16 were stably expressed in whole milk collected within month 2 of lactation from four mothers. Analysis of lipids and skim milk revealed that miR-146b and let-7d were better references in both fractions. Time series (5H-23H) allowed the identification of a set of three endogenous reference genes (hsa-let-7d, hsa-let-7g and miR-146b) to normalize raw quantification cycle (Cq) data. We identified a daily oscillation of miR-16-5p.PerspectivesOur assay allows exploring miRNA levels of breast milk from mother with preterm baby collected in time series over 48–72 hours.

To determine the effects of length of gestation and sex on infant body composition, air displacement plethysmography was performed in forty-six full-term neonates at 3 d of life and during the week prior to hospital discharge in 180 preterm neonates. Fat mass, as a percentage of body weight, was higher in preterm than in term infants (13·4 (SD 4·2) v. 10·1 (SD 3·7) %, respectively; P¼ 0·001). The absolute amount of fat mass did not differ between preterm and full-term newborns (323 (SD 126) v. 335 (SD 138) g; P¼ 0·58), whereas lean body mass was lower in preterm than in term infants (2055 (SD 280) v. 2937 (SD 259) g, respectively; P,0·001). Among full-term infants, fat mass was higher in females than in males (11·1 (SD 3·7) v. 9·0 (SD 3·3) %, respectively; P¼0·047), whereas we did not observe any sex difference in preterm infants (13·5 (SD 4·1) v. 13·4 (SD 4·3) %; P¼ 0·89). Our data suggest that by the time they are discharged from hospital: (1) preterm infants have a higher percentage of body fat than term neonates and (2) this is presumably due to a lesser accretion in lean body mass in the first few weeks of extra-uterine life, particularly in boys.