Determining the metabolic fate of human milk oligosaccharides: It may just be more complex than you think?

Human milk oligosaccharides (HMOs) are a class of structurally diverse and complex unconjugated glycans present in breast milk, which act as selective substrates for several genera of select microbes and inhibit the colonisation of pathogenic bacteria. Yet, not all infants are breastfed, instead being fed with formula milks which may or may not contain HMOs. Currently, formula milks only possess two HMOs: 2 0 -fucosyllactose (2 ’ FL) and lacto- N -neotetraose (LNnT), which have been suggested to be similarly effective as human breast milk in supporting age-related growth. However, the in vivo evidence regarding their ability to beneficially reduce respiratory infections along with altering the composition of an infant ’ s microbiota is limited at best. Thus, this review will explore the concept of HMOs and their metabolic fate, and summarise previous in vitro and in vivo clinical data regarding HMOs, with specific regard to 2 ’ FL and LNnT. Fuc and sialic acid moiety with B. longum bv. infantis ATCC 15697 of Bifidobacterium tested, B. breve ATCC 1570 only able to achieve intermediate levels of growth with only moderate Fuc usage and B. adolescentis and B. bifidum ATCC 15696 exhibiting no growth on either Fuc or sialic acids. These are similar to those recorded by Garrido et al. (2015), who infant formula (Berger et al., 2020). Results were analysed against a breastfed reference group with changes in microbial community types being analysed at 3 and 12 months via 16S rRNA gene sequencing. The results indicated that, compared with the breastfed reference group, the HMO-containing formula stimulated increases in Bifidobacterium , albeit to a lower degree than the reference breastfed group. Levels of Escherichia were, however, significantly lower in the HMO-containing formula group compared with the control group and were similar to those in the breastfed the Bifidobacteriaceae relative abundance, as well as resulting in higher log ratios of Bacteroidaceae and Bifidobacteriaceae relative to Lachnospiraceae and Ruminococcaceae amplicon sequencing variant P These results help to explain the large variability in the presence and levels of HMOs detected in the faecal samples of infants, even when secretor status is considered, with virtually no HMOs being detected potential The opinions/views contained those of