Proof of principle study replicating microbial clusters in connection to birth mode and diet in the early life intestine.

The human gut ecosystem starts developing at birth and is influenced by many factors during early life. In this study we make use of a Belgian cohort of 64 children, followed until the age of 6 years, to analyze different phases of microbiota development. We analyzed fecal samples taken before weaning (age 1 month), shortly after weaning (age 6 months), when milk feeding has been discontinued completely (age 1 year), and at the age of 6 years. We performed 16S rRNA gene amplicon sequencing on the collected fecal samples and analyzed the compositional data in relation to dietary metadata and birth mode. Human and formula milk feeding promotes a microbiota dominated by either Bacteroides or Bifidobacterium, respectively. Into later life stages, the microbiota composition follows distinct microbiota clusters, related to abundance dynamics of certain bacterial groups. Furthermore, it becomes apparent that a formula diet leads to early maturation of the infant gut microbiota. Despite other clinical variables within the infant cohort, they did not significantly contribute to the microbiota patterns we observed. Our data provide a proof of principle study of the importance of diet to the development of the microbiota in early life that replicates earlier findings in other cohorts.

Breast milk urea as a nitrogen source for urease positive Bifidobacterium infantis.

Human milk stimulates a health-promoting gut microbiome in infants. However, it is unclear how the microbiota salvages and processes its required nitrogen from breast milk. Human milk nitrogen sources such as urea could contribute to the composition of this early life microbiome. Urea is abundant in human milk, representing a large part of the non-protein nitrogen (NPN). We found that B. longum subsp. infantis (ATCC17930) can use urea as a main source of nitrogen for growth in synthetic medium and enzyme activity was induced by the presence of urea in the medium. We furthermore confirmed the expression of both urease protein subunits and accessory proteins of B. longum subsp. infantis through proteomics. To the same end, metagenome data were mined for urease-related genes. It was found that the breastfed infant's microbiome possessed more urease-related genes than formula fed infants (51.4:22.1; 2.3-fold increase). Bifidobacteria provided a total of 106 of urease subunit alpha alignments, found only in breastfed infants. These experiments show how an important gut commensal that colonizes the infant intestine can metabolize urea. The results presented herein further indicate how dietary nitrogen can determine bacterial metabolism in the neonate gut and shape the overall microbiome.

Dietary pectin-derived acidic oligosaccharides improve the pulmonary bacterial clearance of Pseudomonas aeruginosa lung infection in mice by modulating intestinal microbiota and immunity.

BACKGROUND: A predominantly T-helper type 2 (Th2) immune response is critical in the prognosis of pulmonary Pseudomonas aeruginosa infection. But the mucosal and systemic immune responses can be influenced by the intestinal microbiota. METHODS: We assessed the effect of microbiota compositional changes induced by a diet enriched in 5% acidic oligosaccharides derived from pectin (pAOS) on the immune response and outcome of chronic pulmonary P. aeruginosa infection in mice. RESULTS: pAOS promoted Th1 polarization by increasing interferon γ release, upregulating t-bet gene expression, decreasing interleukin 4 secretion, and downregulating gata3 gene expression. pAOS also sustained the release of keratinocyte chemoattractant, recruited polynuclear leukocytes and macrophages, stimulated M1 macrophage activation and interleukin 10 release, and decreased tumor necrosis factor α release in the lung. These effects led to increased bacterial clearance after the first and second P. aeruginosa infections. pAOS modified the intestinal microbiota by stimulating the growth of species involved in immunity development, such as Bifidobacterium species, Sutturella wadsworthia, and Clostridium cluster XIVa organisms, and at the same time increased the production of butyrate and propionate. CONCLUSION: These results suggest that pAOS may have beneficial effects by limiting the number and severity of pulmonary exacerbations in patients chronically infected with P. aeruginosa, such as individuals with cystic fibrosis.

ß-Glucans are involved in immune-modulation of THP-1 macrophages.

SCOPE: We aimed to examine different immunological aspects of ß-glucans derived from different food sources (oat, barley and shiitake) on phorbol myristate acetate (PMA)-differentiated THP-1 macrophages. Commercially purified barley ß-glucan (commercial BG) and lentinan were included to compare ß-glucans from the same origin but different degree of purity and processing. METHODS AND RESULTS: Chemical composition and molecular weight distribution of ß-glucan samples were determined. Inflammation-related gene expression kinetics (IL-1ß, IL-8, nuclear factor kappa B [NF-κB] and IL-10) after 3, 6 and 24 h of stimulation with 100 µg/mL ß-glucan were investigated. All tested ß-glucans mildly upregulated the observed inflammation-related genes with differential gene expression patterns. Similar gene expression kinetics, but different fold induction values, was found for the crude ß-glucan extracts and their corresponding commercial forms. Pre-incubation of THP-1 macrophages with ß-glucans prior to lipopolysaccharide (LPS) exposure decreased the induction of inflammation-related genes compared to LPS treatment. No production of nitric oxide (NO) and hydrogen peroxide (H2O2) was detected in ß-glucan stimulated THP-1 macrophages. Phagocytic activity was not different after stimulation by ß-glucan samples. CONCLUSION: Based on these in vitro analyses, it can be concluded that the analysed ß-glucans have varying levels of immunomodulating properties, which are likely related to structure, molecular weight and compositional characteristic of ß-glucan.