Human Milk Oligosaccharides Impact Cellular and Inflammatory Gene Expression and Immune Response

Abstract

Human milk harbors complex carbohydrates, including human milk oligosaccharides (HMOs), the third most abundant component after lactose and lipids. HMOs have been shown to impact intestinal microbiota, modulate the intestinal immune response, and prevent pathogenic bacterial binding by serving as decoy receptors. However, the direct effect of HMOs on intestinal function and immunity remains to be elucidated. To address this knowledge gap, 21-day-old germ-free mice (C57BI/6) were orally gavaged with 15 mg/day of pooled HMOs for 7 or 14 days and euthanized at day 28 or 35. A set of mice was maintained until day 50 to determine the persistent effects of HMOs. Control groups were maintained in the isolators for 28, 35, or 50 days of age. At the respective endpoints, intestinal tissues were subjected to histomorphometric and transcriptomic analyses, while the spleen and mesenteric lymph nodes (MLNs) were subjected to flow cytometric analysis. The small intestine (SI) crypt was reduced after HMO treatment relative to control at days 28 and 35, while the SI villus height and large intestine (LI) gland depth were decreased in the HMO-treated mice relative to the control at day 35. We report significant HMO-induced and location-specific gene expression changes in host intestinal tissues. HMO treatment significantly upregulated genes involved in extracellular matrix, protein ubiquitination, nuclear transport, and mononuclear cell differentiation. CD4+ T cells were increased in both MLNs and the spleen, while CD8+ T cells were increased in the spleen at day 50 in the HMO group in comparison to controls. In MLNs, plasma cells were increased in HMO group at days 28 and 35, while in the spleen, only at day 28 relative to controls. Macrophages/monocytes and neutrophils were lower in the spleen of the HMO group at days 28, 35, and 50, while in MLNs, only neutrophils were lower at day 50 in the 14-day HMO group. In addition, diphtheria toxoid and tetanus toxoid antibody–secreting cells were higher in HMO-supplemented group compared to controls. Our data suggest that HMOs have a direct effect on gastrointestinal tract metabolism and the immune system even in the absence of host microbiota.

Microbiota from human infants consuming secretors or non-secretors mothers’ milk impacts the gut and immune system in mice

“…Similarly, HMOs supplementation increased ileum villus height in SMM + HMOs and NSM + HMOs groups compared to the MFM group though this effect was not seen when the MFM group was fed with HMOs. In contrast to these findings, in our previous study, villus height was decreased in germ-free mice supplemented with HMOs for 14 days ( 7 ). Since there was an absolute absence of microbiota in that study, the increase in villus height observed in the current study implicates microbiota and HMOs interaction effects.…”

“…In germ-free mice, the immune system is not well developed, signifying the importance of microbiota in immune system development ( 51 , 52 ). HMOs can also modulate both innate and adaptive immune cell composition either directly or via modulating microbiota or microbial metabolites ( 5 , 7 , 53 ). In our study, HMOs supplementation elevated CD8+ T cells in the SMM group and Foxp3+ T regulatory cells (Tregs) in the MFM group in the MLN.…”

“…Human milk oligosaccharides (HMOs), the third most abundant component of human milk besides lactose and lipids, are crucial for optimal infant development ( 3 – 5 ). Infants cannot metabolize HMOs though their direct impact on the host immune system and gene expression has been previously shown in a mouse model ( 6 , 7 ). HMOs work as a prebiotic factor because the distal intestinal microbiota uses HMOs as substrates shaping the gut microbiota composition.…”

Specific Human Milk Oligosaccharides Differentially Promote Th1 and Regulatory Responses in a CpG-Activated Epithelial/Immune Cell Coculture

“…These direct effects are difficult to distinguish in in vivo models and clinical studies due to the presence of the microbiome. Furthermore, the large structural variety of HMOS makes identifying structure-function relationships from pooled HMOS challenging, although improved immune maturation has been attributed to the total mixture of HMOS present in human milk [41][42][43][44]. Using an established transwell mucosal immune model combining both IEC and activated PBMC coculture and the presence of a bacterial or allergic trigger, differential immunomodulatory properties of specific HMOS have been identified.…”

Human milk feeding and direct breastfeeding improve outcomes for infants with single ventricle congenital heart disease: Propensity score matched analysis of the NPC-QIC registry

“…In recent years, there has been increased focus on the cellular, molecular, and nutritional composition of HM and on the relationship between HM and the infant gut microbiomeimmune axis. Research has elucidated mechanisms influencing the development of NEC in preterm infants, with HM components such as HM oligosaccharides, [47][48][49][50] exosomes, 51,52 fatty acids and lipids, 53 lactoferrin, 54 immunoglobulins, 54,55 and many other bioactive factors 56 offering tailored protection against NEC and other hospital-associated diseases. Emerging evidence reveals that HM from the infant's own lactating parent (ie, MHM) is associated with epigenetic variation in DNA methylation, 57,58 which may provide protection against oxidative stress that could contribute to NEC.…”