Abstract
Glycoproteins of human milk are multifunctional molecules, and their fucosylated variants are potentially active molecules in immunological events ensuring breastfed infants optimal development and protection against infection diseases. The expression of fucosylated glycotopes may correspond to milk maturation stages. The relative amounts of fucosylated glycotopes of human skim milk glycoproteins over the course of lactation from the 2nd day to the 47th day were analyzed in colostrums, transitional and mature milk samples of 43 healthy mothers by lectin-blotting using α1-2-, α1-6-, and α1-3-fucose specific biotinylated Ulex europaeus (UEA), Lens culinaris (LCA), and Lotus tetragonolobus (LTA) lectins, respectively. The reactivities of UEA and LCA with the milk glycoproteins showed the highest expression of α1-2- and α1-6-fucosylated glycotopes on colostrum glycoproteins. The level of UEA-reactive glycoproteins from the beginning of lactation to the 14th day was high and relatively stable in contrast to LCA-reactive glycoproteins, the level of which significantly decreased from 2–3 to 7–8 days then remained almost unchanged until the 12th–14th days. Next, during the progression of lactation the reactivities with both lectins declined significantly. Eighty percent of α1-2- and/or α1-6-fucosylated glycoproteins showed a high negative correlation with milk maturation. In contrast, most of the analyzed milk glycoproteins were not recognized or weakly recognized by LTA and remained at a low unchanged level over lactation. Only a 30-kDa milk glycoprotein was evidently LTA-reactive, showing a negative correlation with milk maturation. The gradual decline of high expression of α1-2- and α1-6-, but not α1-3-, fucoses on human milk glycoproteins of healthy mothers over lactation was associated with milk maturation.
Highlights
Human milk of a healthy mother supports adequate growth and development of infants, covering nutrient requirements during the first 6 months of life [1,2,3]
The lectin- blotting pattern of human skim milk glycoproteins over the course of lactation showed strong reactivities with
The intensity of bands obtained after silver staining and lectinblotting corresponded to the amount of proteins per band and lectin reactivity with the particular fucosylated glycoproteins of skim milk, respectively
Summary
Human milk of a healthy mother supports adequate growth and development of infants, covering nutrient requirements during the first 6 months of life [1,2,3]. Breast-feeding is connected with neurodevelopmental advantages [1, 2] and reduces the risk of acute and chronic diseases in the developing infant [4,5,6,7] These properties are dependent on bioactive compounds, including fucosylated and sialylated glycoconjugates, which constitute a large part of the human milk and include free oligosaccharides (HMOs), glycoproteins, glycolipids and glycosaminoglycans [8,9,10,11]. Outer arm α1-2- and α1-3-linked fucoses are a part of the Lewis family glycotopes expressed on N- and O-glycans of glycoproteins [15,16,17] and can be recognized and bound by the lectin- receptors of bacteria and/or viruses, and in that way by blocking of lectin- receptors of pathogens prevent their adhesion to the host epithelial cells and prevent colonization and invasion of mucosa [5, 7, 11, 19,20,21]. Fucosylated glycans of milk glycoconjugates can be degraded by bacterial fucosidases produced in particular by Bifidobacterium species, which in this way can gain access to the energetic content of milk and predominance in the intestinal microbiota in the first year of infant life [11, 33]
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