The Role Of Fucosylated And Sialylated Human Milk Oligosaccharides In Infant Nutrition

Human milk oligosaccharides are the third most abundant component of human milk after lactose and lipids, reaching between 5 and 20 g/L in mature human milk..

The HMOs are all based on five monosaccharides; glucose, galactose, N-acetyl-glucosamine, fucose, and sialic acid, also known as N-acetylneuraminic acid [1]. The monosaccharides fucose and sialic acid are also somewhat unusual and interesting. Fucose is structurally different from other 6-carbon monosaccharides present in mammals as it lacks a hydroxyl group on the carbon at the 6-position (C-6) and it has, the L-configuration whereas most other monosaccharides have the D-configuration [2]. Sialic acid is not only a component of HMOs but is also very important in brain development [3]. There are three major types of HMOs: (1) fucosylated HMOs such as 2′-fucosyllactose (2′-FL), (2) sialylated HMOs such as 3’-sialyllactose (3’-SL) and (3) neutral HMOs such as lacto-N-neotetraose (LNnT). The most abundant HMO in breast milk of about 80% of all women is 2′-FL, which constitutes up to 30% of the total HMOs [4]. There are also wide differences in the production of HMOS by individual women. This is due to the presence or absence of the fucosyltransferase 2 (FUT2) secretor gene.