title: Identification of Oligosaccharides in Feces of Breast-fed Infants and Their Correlation with the Gut Microbial Community.
abstract: Glycans in breast milk are abundant and found as either free oligosaccharides or conjugated to proteins and lipids. Free human milk oligosaccharides (HMOs) function as prebiotics by stimulating the growth of beneficial bacteria while preventing the binding of harmful bacteria to intestinal epithelial cells. Bacteria have adapted to the glycan-rich environment of the gut by developing enzymes that catabolize glycans. The decrease in HMOs and the increase in glycan digestion products give indications of the active enzymes in the microbial population. In this study, we quantitated the disappearance of intact HMOs and characterized the glycan digestion products in the gut that are produced by the action of microbial enzymes on HMOs and glycoconjugates from breast milk. Oligosaccharides from fecal samples of exclusively breast-fed infants were extracted and profiled using nanoLC-MS. Intact HMOs were found in the fecal samples, additionally, other oligosaccharides were found corresponding to degraded HMOs and non-HMO based compounds. The latter compounds were fragments of N-glycans released through the cleavage of the linkage to the asparagine residue and through cleavage of the chitobiose core of the N-glycan. Marker gene sequencing of the fecal samples revealed bifidobacteria as the dominant inhabitants of the infant gastrointestinal tracts. A glycosidase from Bifidobacterium longum subsp. longum was then expressed to digest HMOs in vitro, which showed that the digested oligosaccharides in feces corresponded to the action of glycosidases on HMOs. Similar expression of endoglycosidases also showed that N-glycans were released by bacterial enzymes. Although bifidobacteria may dominate the gut, it is possible that specific minority species are also responsible for the major products observed in feces. Nonetheless, the enzymatic activity correlated well with the known glycosidases in the respective bacteria, suggesting a direct relationship between microbial abundances and catabolic activity.
authors.affiliation: From the ‡Department of Chemistry, University of California, Davis, California 95616; §Foods for Health Institute, University of California, Davis, California 95616;
authors.forename: Jasmine C C
authors.initials: JC
authors.lastname: Davis
authors.affiliation: From the ‡Department of Chemistry, University of California, Davis, California 95616; §Foods for Health Institute, University of California, Davis, California 95616;
authors.forename: Sarah M
authors.initials: SM
authors.lastname: Totten
authors.affiliation: From the ‡Department of Chemistry, University of California, Davis, California 95616;
authors.forename: Julie O
authors.initials: JO
authors.lastname: Huang
authors.affiliation: From the ‡Department of Chemistry, University of California, Davis, California 95616;
authors.forename: Sadaf
authors.initials: S
authors.lastname: Nagshbandi
authors.affiliation: §Foods for Health Institute, University of California, Davis, California 95616; ¶Department of Food Science and Technology, University of California, Davis, California 95616;
authors.forename: Nina
authors.initials: N
authors.lastname: Kirmiz
authors.affiliation: §Foods for Health Institute, University of California, Davis, California 95616; ‖Department of Viticulture and Enology, University of California, Davis, California 95616.
authors.forename: Daniel A
authors.initials: DA
authors.lastname: Garrido
authors.affiliation: §Foods for Health Institute, University of California, Davis, California 95616; ¶Department of Food Science and Technology, University of California, Davis, California 95616;
authors.forename: Zachery T
authors.initials: ZT
authors.lastname: Lewis
authors.affiliation: From the ‡Department of Chemistry, University of California, Davis, California 95616; §Foods for Health Institute, University of California, Davis, California 95616;
authors.forename: Lauren D
authors.initials: LD
authors.lastname: Wu
authors.affiliation: §Foods for Health Institute, University of California, Davis, California 95616; ¶Department of Food Science and Technology, University of California, Davis, California 95616;
authors.forename: Jennifer T
authors.initials: JT
authors.lastname: Smilowitz
authors.affiliation: §Foods for Health Institute, University of California, Davis, California 95616; ¶Department of Food Science and Technology, University of California, Davis, California 95616;
authors.forename: J Bruce
authors.initials: JB
authors.lastname: German
authors.affiliation: §Foods for Health Institute, University of California, Davis, California 95616; ¶Department of Food Science and Technology, University of California, Davis, California 95616; ‖Department of Viticulture and Enology, University of California, Davis, California 95616.
authors.forename: David A
authors.initials: DA
authors.lastname: Mills
authors.affiliation: From the ‡Department of Chemistry, University of California, Davis, California 95616; §Foods for Health Institute, University of California, Davis, California 95616; cblebrilla@ucdavis.edu.
authors.forename: Carlito B
authors.initials: CB
authors.lastname: Lebrilla
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism; D001644:Bifidobacterium / Q000201:enzymology / Q000235:genetics / Q000302:isolation & purification; D002853:Chromatography, Liquid; D005243:Feces / Q000737:chemistry* / Q000382:microbiology; D000069196:Gastrointestinal Microbiome; D006026:Glycoside Hydrolases / Q000378:metabolism*; D006801:Humans; D007223:Infant; D013058:Mass Spectrometry; D008895:Milk, Human / Q000737:chemistry*; D009844:Oligosaccharides / Q000302:isolation & purification*
chemical_list: D001426:Bacterial Proteins; D009844:Oligosaccharides; D006026:Glycoside Hydrolases