Hill Cian J.,Lynch Denise B.,Murphy Kiera,Ulaszewska Marynka,Jeffery Ian B.,O’Shea Carol Anne,Watkins Claire,Dempsey Eugene,Mattivi Fulvio,Tuohy Kieran,Ross R. Paul,Ryan C. Anthony,O’ Toole Paul W.,Stanton Catherine
Background The gut is the most extensively studied niche of the human microbiome. The aim of this study was to characterise the initial gut microbiota development of a cohort of breastfed infants ( n = 192) from 1 to 24 weeks of age. Methods V4-V5 region 16S rRNA amplicon Illumina sequencing and, in parallel, bacteriological culture. The metabolomic profile of infant urine at 4 weeks of age was also examined by LC-MS. Results Full-term (FT), spontaneous vaginally delivered (SVD) infants’ microbiota remained stable at both phylum and genus levels during the 24-week period examined. FT Caesarean section (CS) infants displayed an increased faecal abundance of Firmicutes ( p < 0.01) and lower abundance of Actinobacteria ( p < 0.001) after the first week of life compared to FT-SVD infants. FT-CS infants gradually progressed to harbouring a microbiota closely resembling FT-SVD (which remained stable) by week 8 of life, which was maintained at week 24. The gut microbiota of preterm (PT) infants displayed a significantly greater abundance of Proteobacteria compared to FT infants ( p < 0.001) at week 1. Metabolomic analysis of urine at week 4 indicated PT-CS infants have a functionally different metabolite profile than FT (both CS and SVD) infants. Co-inertia analysis showed co-variation between the urine metabolome and the faecal microbiota of the infants. Tryptophan and tyrosine metabolic pathways, as well as fatty acid and bile acid metabolism, were found to be affected by delivery mode and gestational age. Conclusions These findings confirm that mode of delivery and gestational age both have significant effects on early neonatal microbiota composition. There is also a significant difference between the metabolite profile of FT and PT infants. Prolonged breastfeeding was shown to have a significant effect on the microbiota composition of FT-CS infants at 24 weeks of age, but interestingly not on that of FT-SVD infants. Twins had more similar microbiota to one another than between two random infants, reflecting the influence of similarities in both host genetics and the environment on the microbiota.
Xinyue Dai,Tinglan Yuan,Xinghe Zhang,Qin Zhou,Huiya Bi,Renqiang Yu,Wei Wei,Xingguo Wang
This study aimed to quantify the short-chain fatty acids (SCFAs) and medium-chain fatty acids (MCFAs) in human milk triacylglycerols (TAGs) and investigate their concentrations in human milk consumed during lactation by infants born at different gestational ages. One hundred and eighty milk samples from the mothers of 30 full-term, 10 early-preterm (≤32 weeks), 10 mild-preterm (32–34 weeks), and 10 near-term (34–37 weeks) infants were collected from the colostrum, transitional, and mature milk. The human milk TAGs were transferred into fatty-acid methyl esters via potassium methoxide in methanol and determined using gas chromatography (GC). The total SCFA (4:0) and MCFA concentrations (6:0 and 8:0) were highest in the mature milk (1.47 ± 0.66 mg g−1 fat from full-term infant milk), approximately 42.18% higher than those in transitional milk. Significantly higher SCFA and MCFA concentrations were found in full-term milk than in preterm milk (p = 0.001). The milk TAGs were analyzed using ultra-high-performance supercritical fluid chromatography with quadrupole-time-of-flight mass spectrometry (UHPSFC-Q-TOF-MS), which showed that the SCFAs and MCFAs were mainly esterified with long-chain fatty-acid groups (16:0, 18:1 n-9, and 18:2 n-6) at the glycerol backbone. The infants’ daily SCFA intake from human milk was estimated; this was highest from mature milk for full-term infants (∼14 mg d−1) which was significantly different from that of preterm infants from colostrum and transitional milk (p < 0.001). The correlation between dietary SCFAs and MCFAs in human milk and nutrition in newborns, especially in the gut microbiotas of preterm infants, requires further study.
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