Human milk oligosaccharides

Editor/ Takane Katayama, Tadasu Urashima


The galectin-lattice: a decoder of bio-equivalent glycans

Tadasu Urashima

last updated 2021/10/01 (Glycoforum. 2021 Vol.24 (5), A14)  

Human milk contains 7% of carbohydrate, 80% of which consists of lactose (Galβ1-4Glc), while 20% consists of oligosaccharides. The concentrations of milk oligosaccharides are 12 ~ 13 g/L in mature milk and 22 ~ 24 g/L in colostrum; these are the third largest solid component after lactose and lipid. Their concentrations are surprisingly high. Most of the human milk oligosaccharides (HMOs), with few exceptions, contain a lactose unit at their reducing ends, to which monosaccharides residues including N-acetylglucosamine (GlcNAc), galactose (Gal), fucose (Fuc), and N-acetylneuraminic acid (Neu5Ac) are attached. To date about 250 HMOs have been separated, of which about 170 structures have been characterized. When breast-fed infants consume their mothers’ milk, the lactose is hydrolyzed to Glc and Gal by small intestinal lactase, to be absorbed, whereas most HMOs remain intact within the small intestine and thus reach the colon, where they have significant physiological functions other than nutritional effects. Based on the experimental evidence, the following functions have been proposed: stimulation of the growth of beneficial colonic bacteria such as bifidobacterium, anti-infection against pathogenic bacteria and viruses, immune modulation including anti-inflammation, prevention of necrotizing enterocolitis and reinforcement of the colonic barrier function, and activation of brain-nerve functions. In this series of Glycoforum, some of the exciting discoveries will be described, focusing on the metabolic pathways of HMOs by bifidobacteria, the functions of HMOs relating to the cross talk between colonic bacteria and host epithelial cells, and the industrial production of HMOs. In this series the history of studies in this field, with future aspects, will be dynamically expanded by first-class researchers. In the beginning of this series, international studies clarifying the biological functions of HMOs will be introduced. ...and more