Hidratos de carbono complejos en la leche materna: los oligosacáridos (Parte 1)

Abstract

Human milk oligosaccharides (HMOs) are a family of some 200 different molecules synthesized by the mammary gland. At the core is a molecule of lactose, which is linked by different enzymes to glucose, galactose, n-acetyl galactosamine, fucose or sialic acid. These linkages and their different spatial orientation generate, besides the possibilities of numerous chemical structures, the potential for different spatial isomers. The concentration of HMOs in human milk depends on pregnancy and breastfeeding duration. They are highest in colostrum (± 25 g/L) and decrease over time to half this initial level. Maternal genetics modifies the concentration and profile of some oligosaccharides. For example, the FUT2 gene codifies the synthesis of fucosyltransferase 2 (FUT2) whose activity generates the secretor status for antigens of the ABO(H) blood group in organic fluids (saliva, milk, tears, semen) among 75-85% of the carriers of the trait. The absence of activity of the FUT2 gene conditions the non-secretor status (15-25% of women). The FUT3 gene regulates the activity of the fucosyltransferase 3 (FUT3) that is associated with the Lewis blood group. Traces of HMOs (1%) are absorbed in the intestinal tract, however, they exert important systemic effects even at low concentrations.