Breastmilk-promoted bifidobacteria produce aromatic amino acids in the infant gut

Abstract

26Breastfeeding profoundly shapes the infant gut microbiota, which is critical for early life immune 27 development. However, few breastmilk-dependent microbial metabolites mediating host-microbiota 28 interactions are currently known. We here demonstrate that breastmilk-promoted Bifidobacterium 29 species convert aromatic amino acids (tryptophan, phenylalanine and tyrosine) into their respective 30 aromatic lactic acids (indolelactate, phenyllactate and 4-hydroxyphenyllactate) via a previously 31 unrecognised aromatic lactate dehydrogenase. By longitudinal profiling of the gut microbiota 32 composition and metabolome of stool samples of infants obtained from birth until 6 months of age, 33 we show that stool concentrations of aromatic lactic acids is determined by the abundance of human 34 milk oligosaccharide degrading Bifidobacterium species containing the aromatic lactate 35 dehydrogenase. Finally, we demonstrate that stool concentrations of Bifidobacterium-derived 36 indolelactate are associated with the capacity of infant stool samples to activate the aryl 37 hydrocarbon receptor, a receptor important for maintenance of intestinal homeostasis and immune 38 system development. These findings open up new directions towards understanding the role of 39 breastmilk-promoted Bifidobacterium in mediating host-microbiota interactions in early life. 40 INTRODUCTION 41Human breastmilk is a perfectly adapted nutritional supply for the infant 1 . Breastfeeding provides 42 children with important short-term protection against infections, and may also provide long-term 43 metabolic benefits 1,2 . These benefits may partly be mediated through the gut microbiota, since 44 breastfeeding is the strongest determinant of gut microbiota composition and function during 45 infancy 3-5 . Human breastmilk contains human milk oligosaccharides (HMOs), which are complex, 46 highly abundant sugars serving as substrates for specific microbes including certain species of 47 Bifidobacterium 6 . This co-evolution between bifidobacteria and the host, mediated by HMOs, to a 48 large extent directs the colonization of the gut in early life, which has critical impact on the immune 49 system 7 . Depletion of specific microbes, including Bifidobacterium, in early life has been associated 50 with increased risk of allergy and asthma development in childhood 8,9 , and is suggested to 51 compromise immune function and lead to increased susceptibility to infectious disease 10,11 . Despite 52 Bifidobacterium dominating the gut of breastfed infants and being widely acknowledged as 53 beneficial, mechanistic insights on the contribution of these bacteria and their metabolites to 54 immune development during infancy remain limited. Recent studies show that microbial aromatic 55 amino acid metabolites including tryptophan-derived indoles 12 , via activation of the aryl 56 hydrocarbon receptor (AhR), can fortify the intestinal barrier 13,14 , protect against pathogenic 57 infections 15,16 and influence host metabolism 13,17,18 , which makes this...

Enzymatic Adaptation of Bifidobacterium bifidum to Host Glycans, Viewed from Glycoside Hydrolyases and Carbohydrate-Binding Modules

“…Apart from the microbe to microbe interactions, recent studies have revealed that B. bifidum has immunomodulatory activity by inducing regulatory T-cells by microbe-host interaction with its cell-surface polysaccharides [98]. The production of indole lactic acid, an AhR ligand, by infant gut-associated Bifidobacterium species, including B. bifidum, was also recently reported [8,99]. Further investigation is needed to understand the physiology of this species in the gut ecosystem and its role in host interactions.…”

“…These "first colonizers" are believed to confer various beneficial effects on human health, including protection against pathogen infection [2,3], nutritional supplementation [4], reduced inflammation [5,6], and the development of the immune system [7]. Notably, a recent research revealed that bifidus-flora formation is associated with the increased fecal concentration of indole lactic acid, a ligand of arylhydrocarbon receptor (AhR) [8]. In the Bifidobacterium genus, four species, i.e., Bifidobacterium bifidum, Bifidobacterium breve, Bifidobacterium longum ssp.…”

Untargeted metabolomic study of autism in newborn screening samples: a pilot study

“…Microbial metabolites would necessarily need to travel in the blood (or lymph) and through the blood-brain barrier to interact with the brain. In our study, some detected metabolites could partly derive from gut microbiota activity such as DL-Indole-3-lactic acid (ID3461, [99,100] Lastly, we found that month of birth explains a significant variation in metabolomic profiles of newborns (Figure 3b, Figure 4). Whether there is a yearly cyclic pattern or whether our findings are specific to 2005 remains to be determined.…”

Impact of Probiotic B. Infantis EVC001 Feeding in Premature Infants on the Gut Microbiome, Nosocomially Acquired Antibiotic Resistance, and Enteric Inflammation

“…Alternatively, the absolute abundance of B. infantis EVC001, independent of microbiome composition, correlated with decreased proinflammatory cytokine profiles, which indicates a benefit in feeding B. infantis EVC001 and may support the hypothesis that B. infantis-derived bacterial metabolites, produced through the utilization of HMOs, induce mucosal immune tolerance in the gut [49,58]. Notably, Bifidobacterium-derived acetate has previously been shown to mitigate the pathogenesis of Enterobacteriaceae infection in an animal model [57], and B. infantis-derived indole-3-lactic acid production reduced pathogen-induced inflammation in enterocytes in vitro [49,58] through activation of the aryl hydrocarbon receptor [49,59]. Recently, differences in B. infantis HMO utilization loci have been identified [60], and strains missing key genes involved in HMO utilization are unlikely to confer the same benefits to infants as we observed here, as the conversion of indigestible HMOs to infant accessible short chain fatty acids and indole-3-lactic acid are key functions of a healthy gut microbiome, whether in term or preterm infants [23].…”