The role of human milk oligosaccharides in preventing necrotising enterocolitis and human immunodeficiency virus transmission

Abstract

The role of human milk oligosaccharides in preventing necrotising enterocolitis and human immunodeficiency virus transmission IntroductionResearch, started over a century ago, on human milk oligosaccharides (HMOs) has focused predominantly on their prebiotic effects. Today it is known that the bifidogenic effects of HMOs are one of the many beneficial effects now being discovered. 1 In addition to providing a substrate for the growth of beneficial bacteria, HMOs also directly inhibit pathogens from adhering to the intestinal epithelia through their antiadhesive properties. 1 Recent data suggest that firstly, a relationship exists between the HMOs and the incidence of necrotising enterocolitis (NEC), 2,3 and secondly, they may have an influence on human immunodeficiency virus (HIV) transmission. 4 This article aims to describe the prebiotic and antiadhesive effects of HMOs, and how they could possibly prevent the development of NEC in the presence of HIV infection. Human milk oligosaccharidesHMOs 5,6 are complex carbohydrates that are highly abundant in breast milk, but not in infant formula. 7 Oligosaccharides are carbohydrates made up of 3-9 monosaccharide units. 5,6 The oligosaccharide concentration of human milk varies with gestational age, lactation duration, and from one mother to another. 6,8 HMOs reach the highest concentration in colostrum (20-25 g/l), and then decrease after roughly two weeks to approximately 5-20 g/l in mature breast milk. 1,6,[8][9][10][11] HMOs consists of five different monosaccharide units:• Glucose.• Galactose.• The sialic acid component, known as N-acetylglucosamine.• Fucose.• N-acteylneuaminic acid. 1,12 With a few exceptions, all HMOs contain lactose at their reducing end. They may be elongated (an enzymatic attachment) by the addition of β1-3-or β1-6-linked lacto-N-biose or N-acetyllacetosamine. The latter can be further extended by one or two disaccharides. Chain branching may occur at the β1-6 linkage. Branched lactose molecules may form both linear (para-HMOs) and branched structures (iso-HMOs). Furthermore, oligosaccharide chains can be fucosylated (also known as neutral oligosaccharides) in the α1-2, α1-3 or α1-4 linkage, or sialylated (also known as acidic oligosaccharides) in the α2-3 or α2-6 linkage. The ABH secretor (Se) status and Lewis (Le) blood group determines the HMO composition of a mother's breast milk. 1 The presence or absence of blood group substances (A, B and H) in the saliva and other body secretions is controlled by a gene on chromosome 19, the fucosyltransferase AbstractThe heavy burden of maternal human immunodeficiency virus (HIV) infection has resulted in a high prevalence of premature births, with an associated increase in the incidence of necrotising enterocolitis (NEC). NEC is a life-threatening inflammatory disease of the gastrointestinal tract that predominantly occurs in preterm infants. Human milk oligosaccharides (HMOs) are carbohydrate compounds which have been shown to have health-promoting effects through their bifidogenic and antiadhesiv...