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    N-glycans from human milk glycoproteins are selectively released by an infant gut symbiont in vivo
    (Elsevier, 2019) Karav, Sercan; Casaburi, Giorgio; Arslan, Aysenur; Kaplan, Merve; Sucu, Berfin; Frese, Steven
    Complex, indigestible free oligosaccharides as well as conjugated glycans are found in milk that shape the gut microbiome of infants. The activity of an endo-beta-N-acetylglucosaminidase from B. longum subsp. infantis (B. infantis) is known to release N-glycans from native milk glycoproteins under physiological conditions. We investigated whether this enzyme is active in vivo in breastfed infants fed B. infantis EVC001. Using mass spectrometry, we found 19 N-glycans related to human milk glycoproteins increased in abundance, similar to previous work using bovine milk glycoproteins, and these 19 N-glycans matched unique specificities of this enzyme. Twenty N-glycans were unique to infants fed B. infantis EVC001. Bifidobacteriaceae were correlated with these glycans, confirming the relationship between B. infantis and released N-glycans. This suggests that this enzyme is active in vivo and releases N-glycans from milk glycoproteins, and may play a role in B. infantis EVC001 colonization of the gut microbiome.
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    Öğe
    Reduced colonic mucin degradation in breastfed infants colonized by Bifidobacteriumlongum subsp. infantis EVC001
    (Wiley, 2018) Karav, Sercan; Casaburi, Giorgio; Frese, Steven A.
    Mucin glycoproteins play an important role in protecting the gut epithelium by keeping gut microbes from direct contact with the gut epithelium while allowing for diffusion of small molecules from the lumen to the epithelium. The mucin glycocalyx can be degraded by gut bacteria such as Bacteroides and Akkermansia, but other bacteria, such as Bifidobacteriumlongum subsp. Infantis, cannot consume mucin glycans. Untargeted mass spectrometry profiles were compared to microbiome profiles to assess how different gut microbiomes affect colonic mucin degradation. Samples obtained from nine infants colonized by Bifidobacteriuminfantis EVC001 and from 10 infants colonized by higher levels of mucolytic taxa (controls), including Bacteroides, were compared. Previously performed untargeted nano-high-performance liquid chromatography-chip/time-of-flight mass spectrometry was used to detect and quantify glycans originating from colonic mucin. Colonic mucin-derived O-glycans from control infants composed 37.68% (+/- 3.14% SD) of the total glycan structure pool, whereas colonic mucin-derived O-glycans made up of only 1.78% (+/- 0.038% SD) of the total in B.infantis EVC001 samples. The relative abundance of these colonic mucin-derived O-glycans in the total glycan pool was higher among control, 26.98% (+/- 8.48% SD), relative to B.infantis-colonized infants, 1.68% (+/- 1.12% SD). Key taxa, such as Bacteroidaceae, were significantly and positively correlated with the abundance of these structures, while Bifidobacteriaceae were significantly and negatively associated with these structures. These results suggest that colonization of infants by B.infantis may diminish colonic glycan degradation and help maintain barrier function in the gastrointestinal tract of infants.