Human Milk Oligosaccharides and Microbiome Homeostasis

Abstract

Human milk oligosaccharides (HMOs) are one of the more abundant components in breast milk. They represent a large family of carbohydrates with high structural diversity. One relevant function they provide is the promotion of beneficial bacteria in the infant gut microbiome. These compounds work as prebiotics guiding gut microbiome assembly and composition, stimulating the growth of certain Bifidobacterium species. Advances in genomics and transcriptomics have allowed a better understanding of microbial HMO consumption, indicating several genomic adaptations of these species to the conditions prevalent in the infant gut. Bifidobacterium species metabolize HMOs into short-chain fatty acids, key molecules that support a balanced gut ecosystem. Thus, the Bifidobacterium species overabundance is important to maintain gut homeostasis and confer protection to the infant, where HMOs play an essential role. Disruptions in the assembly or composition of the infant gut, for example, due to antibiotics, causes shifts in a microbiome dominated by Bifidobacterium. These alterations correlate with an increased incidence of certain metabolic, autoimmune, and allergic diseases. Finally, we are beginning to understand how HMO utilization promotes metabolic interactions between gut microbes, which could share resources by cross-feeding to maximize nutrient consumption. This article discusses current advances regarding the HMO role on infant gut microbiome homeostasis.