Maternal Human Milk Oligosaccharide Profile Modulates the Impact of an Intervention with Iron and Galacto-Oligosaccharides in Kenyan Infants

There is little data on human milk oligosaccharide (HMO) composition in Sub-Saharan Africa. Iron fortificants adversely affect the infant gut microbiota, while co-provision of prebiotic galacto-oligosaccharides (GOS) mitigates most of the adverse effects. Whether variations in maternal HMO profile can influence the infant response to iron and/or GOS fortificants is unknown. The aim of this study was to determine HMO profiles and the secretor/non-secretor phenotype of lactating Kenyan mothers and investigate their effects on the maternal and infant gut microbiota, and on the infant response to a fortification intervention with 5 mg iron (2.5 mg as sodium iron ethylenediaminetetraacetate and 2.5 mg as ferrous fumarate) and 7.5 g GOS. We studied mother-infant pairs (n = 80) participating in a 4-month intervention trial in which the infants (aged 6.5-9.5 months) received daily a micronutrient powder without iron, with iron or with iron and GOS. We assessed: (1) maternal secretor status and HMO composition; (2) effects of secretor status on the maternal and infant gut microbiota in a cross-sectional analysis at baseline of the intervention trial; and (3) interactions between secretor status and intervention groups during the intervention trial on the infant gut microbiota, gut inflammation, iron status, growth and infectious morbidity. Secretor prevalence was 72% and HMOs differed between secretors and non-secretors and over time of lactation. Secretor status did not predict the baseline composition of the maternal and infant gut microbiota. There was a secretor-status-by-intervention-group interaction on Bifidobacterium (p = 0.021), Z-scores for length-for-age (p = 0.022) and weight-for-age (p = 0.018), and soluble transferrin receptor (p = 0.041). In the no iron group, longitudinal prevalence of diarrhea was higher among infants of non-secretors (23.8%) than of secretors (10.4%) (p = 0.001). In conclusion, HMO profile may modulate the infant gut microbiota response to fortificant iron; compared to infants of secretor mothers, infants of non-secretor mothers may be more vulnerable to the adverse effect of iron but also benefit more from the co-provision of GOS

Effect of iron on the ability of enteric bacteria to induce cell damage.

<p>LDH-release (mean+SD) as a measure of cell damage of Caco-2 cells upon co-incubation with <i>S. typhimurium</i> (St, <i>n</i> = 5), <i>C. freundii</i> (Cf, <i>n</i> = 4), <i>E. coli</i> (Ec, <i>n</i> = 4), <i>E. faecalis</i> (Ef, <i>n</i> = 4), and <i>L. plantarum</i> (Lp, <i>n</i> = 2) pre-incubated with or without ferric citrate. The percentage LDH release compared to the control (no bacteria) was corrected for the number of bacteria in the medium (average between t = 0 and t = 2 h). Means within a group and without a common letter differ significantly, <i>P</i><0.05.</p

Effect of iron on bacterial adhesion to an epithelial monolayer.

<p>Adhesion (mean+SD) of enteric bacteria to a monolayer of Caco-2 cells is given as percentage of the inoculum. <b>A</b>: <i>S. typhimurium</i>, <i>n</i> = 8. <b>B</b>: <i>C. freundii</i>, <i>n</i> = 4. <b>C</b>: <i>E. coli</i>, <i>n</i> = 6. <b>D</b>: <i>E. faecalis</i>, <i>n</i> = 6. <b>E</b>: <i>L. plantarum</i>, <i>n</i> = 5. Means without a common letter differ, <i>P</i><0.05. Notably, adhesion data of <i>S. typhimurium</i> were derived from 4 separate experiments performed at 13, 15, 18 and 21 days post-seeding of Caco-2 cells. The fact that each experiment revealed the same trend is indicative for similar physiochemical properties of the monolayer at these time points.</p

Effect of iron on invasion of <i>S. typhimurium</i> into epithelial cells.

<p>Invasion (mean+SD) of <i>S. typhimurium</i> into Caco-2 cells, <i>n</i> = 2. Invasion after 3.5 h is given as percentage of the inoculum. The inoculum was removed after 2 hours of adhesion time. Means of 0–10 µmol/L ferric citrate were compared by one-way ANOVA.</p

Effect of iron on the ability of <i>S. typhimurium</i> to cross and deteriorate an epithelial monolayer.

<p>Effect of iron on the ability of <i>S. typhimurium</i> to cross an epithelial monolayer of Caco-2 cells and the integrity of this monolayer. <b>A</b>: The translocation is given as percentage of the inoculum (mean+SD), <i>n</i> = 2. Means without a common letter differ, <i>P</i><0.07. <b>B</b>: The integrity of the Caco-2 monolayer during <i>S. typhimurium</i> (St) and <i>L. plantarum</i> (Lp) translocation, monitored by TEER measurements.</p

Mothers’ Breast Milk Composition and Their Respective Infant’s Gut Microbiota Differ between Five Distinct Rural and Urban Regions in Vietnam

Microbiota colonization and development in early life is impacted by various host intrinsic (genetic) factors, but also diet, lifestyle, as well as environmental and residential factors upon and after birth. To characterize the impact of maternal nutrition and environmental factors on vaginally born infant gut microbiota composition, we performed an observational study in five distinct geographical areas in Vietnam. Fecal samples of infants (around 39 days old) and fecal and breast milk samples of their mothers (around 28 years) were collected. The microbiota composition of all samples was analyzed by 16S rRNA gene Illumina sequencing and a bioinformatics workflow based on QIIME. In addition, various breast milk components were determined. Strong associations between the geographically determined maternal diet and breast milk composition as well as infant fecal microbiota were revealed. Most notable was the association of urban Ha Noi with relatively high abundances of taxa considered pathobionts, such as Klebsiella and Citrobacter, at the expense of Bifidobacterium. Breast milk composition was most distinct in rural Ha Long Bay, characterized by higher concentrations of, e.g., docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA), selenium, and vitamin B12, while it was characterized by, e.g., iron, zinc, and α-linolenic acid (ALA) in Ha Noi. Breast milk iron levels were positively associated with infant fecal Klebsiella and negatively with Bifidobacterium, while the EPA and DHA levels were positively associated with Bifidobacterium. In conclusion, differences between five regions in Vietnam with respect to both maternal breast milk and infant gut microbiota composition were revealed, most likely in part due to maternal nutrition. Thus, there could be opportunities to beneficially steer infant microbiota development in a more desired (rural instead of urban) direction through the mother’s diet