Low Diversity of Human Milk Oligosaccharides is Associated with Necrotising Enterocolitis in Extremely Low Birth Weight Infants

Abstract

Difference in human milk oligosaccharides (HMO) composition in breast milk may be one explanation why some preterm infants develop necrotizing enterocolitis (NEC) despite being fed exclusively with breast milk. The aim of this study was to measure the concentration of 15 dominant HMOs in breast milk during the neonatal period and investigate how their levels correlated to NEC, sepsis, and growth in extremely low birth weight (ELBW; <1000 g) infants who were exclusively fed with breast milk. Milk was collected from 91 mothers to 106 infants at 14 and 28 days and at postmenstrual week 36. The HMOs were analysed with high-performance anion-exchange chromatography with pulsed amperometric detection. The HMOs diversity and the levels of Lacto-N-difucohexaose I were lower in samples from mothers to NEC cases, as compared to non-NEC cases at all sampling time points. Lacto-N-difucohexaose I is only produced by secretor and Lewis positive mothers. There were also significant but inconsistent associations between 3'-sialyllactose and 6'-sialyllactose and culture-proven sepsis and significant, but weak correlations between several HMOs and growth rate. Our results suggest that the variation in HMO composition in breast milk may be an important factor explaining why exclusively breast milk fed ELBW infants develop NEC.

Keywords: breast milk; diversity; growth; necrotizing enterocolitis; neonatal; oligosaccharides; preterm; sepsis.

Figure 1

Non-metric multidemension scaling (NMDS) plot of the HMO composition among the 41 mothers with samples from all three time points. Each mother is indicated by a number from 1 to 41. PMW 36 + 0: postmenstrual week 36 + 0. Stress level: 0.08

Figure 2

Human milk oligosaccharide (HMO) content in the first breast milk sample from mothers of all NEC-cases, stratified according to secretor (Se) and Lewis (Le) status, and median HMO levels in milk samples from day 14 from the non-NEC cases of the respective Se/Le groups

Figure 3

Human milk oligosaccharide (HMO) diversity in breast milk samples and the incidence of NEC (a) and culture proven sepsis (b). Boxes indicate 25^th, 50^th and 75^th percentiles; whiskers indicate min and max values. t-test for independent samples was used to compare means. N indicates the number of patients in each group. PMW=postmenstrual week.

Figure 4

Correlations between concentrations of individual human milk oligosaccharide (HMO) (micromol/litre) in milk samples from day 14 and infant growth (change in z-score from birth to measurement on the 14^th or 28^th day of life or at 36 postmenstrual week (PMW), analysed using Spearman´s rho correlation coefficient. Significant correlations are highlighted with green for positive and red for negative correlations.