Dynamics of Gut Microbiota and Short-Chain Fatty Acids during a Cycling Grand Tour Are Related to Exercise Performance and Modulated by Dietary Intake.

BACKGROUND: Regular exercise has been described to modify both the diversity and the relative abundance of certain bacterial taxa. To our knowledge, the effect of a cycling stage race, which entails extreme physiological and metabolic demands, on the gut microbiota composition and its metabolic activity has not been analysed. OBJECTIVE: The aim of this cohort study was to analyse the dynamics of faecal microbiota composition and short-chain fatty acids (SCFAs) content of professional cyclists over a Grand Tour and their relationship with performance and dietary intake. METHODS: 16 professional cyclists competing in La Vuelta 2019 were recruited. Faecal samples were collected at four time points: the day before the first stage (A); after 9 stages (B); after 15 stages (C); and on the last stage (D). Faecal microbiota populations and SCFA content were analysed using 16S rRNA sequencing and gas chromatography, respectively. A principal component analysis (PCA) followed by Generalised Estimating Equation (GEE) models were carried out to explore the dynamics of microbiota and SCFAs and their relationship with performance. RESULTS: Bifidobacteriaceae, Coriobacteriaceae, Erysipelotrichaceae, and Sutterellaceae dynamics showed a strong final performance predictive value (r = 0.83, ranking, and r = 0.81, accumulated time). Positive correlations were observed between Coriobacteriaceae with acetate (r = 0.530) and isovalerate (r = 0.664) and between Bifidobacteriaceae with isobutyrate (r = 0.682). No relationship was observed between SCFAs and performance. The abundance of Erysipelotrichaceae at the beginning of La Vuelta was directly related to the previous intake of complex-carbohydrate-rich foods (r = 0.956), while during the competition, the abundance of Bifidobacteriaceae was negatively affected by the intake of simple carbohydrates from supplements (r = -0.650). CONCLUSIONS: An ecological perspective represents more realistically the relationship between gut microbiota composition and performance compared to single-taxon approaches. The composition and periodisation of diet and supplementation during a Grand Tour, particularly carbohydrates, could be designed to modulate gut microbiota composition to allow better performance.

Gut microbiota modulation and effects of a diet enriched in apple pomace on inflammation in a DSS-induced colitis mouse model.

Certain types of soluble dietary fibre, such as pectin and pectic oligosaccharides from different sources, have demonstrated protective effects against inflammation in DSS-induced colitis mouse models. In this work, we have evaluated the impact of a diet enriched in apple pomace (AP-diet), an agricultural by-product with a significant content of pectin and that previously demonstrated prebiotic properties in human fecal batch fermentation models, on the gut microbiota composition, intestinal damage and inflammation markers in a DSS-induced colitis model. We found that the apple pomace enriched diet (AP-diet), providing a significant amount of pectin with demonstrated prebiotic properties, was associated with a slower increase in the disease activity index, translating into better clinical symptomatology of the animals. Histological damage scoring confirmed less severe damage in those animals receiving an AP-diet before and during the DSS administration period. Some serum inflammatory markers, such as TNFα, also demonstrated lower levels in the group receiving the AP-diet, compared to the control diet. AP-diet administration is also associated with the modulation of key taxa in the colonic microbiota of animals, such as some Lachnospiraceae genera and Ruminococcus species, including commensal short chain fatty acid producers that could play a role in attenuating inflammation at the intestinal level.

Arabinoxylan and Pectin Metabolism in Crohn's Disease Microbiota: An In Silico Study.

Inflammatory bowel disease is a chronic disorder including ulcerative colitis and Crohn's disease (CD). Gut dysbiosis is often associated with CD, and metagenomics allows a better understanding of the microbial communities involved. The objective of this study was to reconstruct in silico carbohydrate metabolic capabilities from metagenome-assembled genomes (MAGs) obtained from healthy and CD individuals. This computational method was developed as a mean to aid rationally designed prebiotic interventions to rebalance CD dysbiosis, with a focus on metabolism of emergent prebiotics derived from arabinoxylan and pectin. Up to 1196 and 1577 MAGs were recovered from CD and healthy people, respectively. MAGs of Akkermansia muciniphila, Barnesiella viscericola DSM 18177 and Paraprevotella xylaniphila YIT 11841 showed a wide range of unique and specific enzymes acting on arabinoxylan and pectin. These glycosidases were also found in MAGs recovered from CD patients. Interestingly, these arabinoxylan and pectin degraders are predicted to exhibit metabolic interactions with other gut microbes reduced in CD. Thus, administration of arabinoxylan and pectin may ameliorate dysbiosis in CD by promoting species with key metabolic functions, capable of cross-feeding other beneficial species. These computational methods may be of special interest for the rational design of prebiotic ingredients targeting at CD.

Bifidobacterium adolescentis as a key member of the human gut microbiota in the production of GABA.

Gamma aminobutyric acid (GABA) is the principal inhibitory neurotransmitter playing a key role in anxiety and depression disorders in mammals. Recent studies revealed that members of the gut microbiota are able to produce GABA modulating the gut-brain axis response. Among members of the human gut microbiota, bifidobacteria are well known to establish many metabolic and physiologic interactions with the host. In this study, we performed genome analyses of more than 1,000 bifidobacterial strains publicly available revealing that Bifidobacterium adolescentis taxon might represent a model GABA producer in human gastrointestinal tract. Moreover, the in silico screening of human/animal metagenomic datasets showed an intriguing association/correlation between B. adolescentis load and mental disorders such as depression and anxiety. Interestingly, in vitro screening of 82 B. adolescentis strains allowed identifying two high GABA producers, i.e. B. adolescentis PRL2019 and B. adolescentis HD17T2H, which were employed in an in vivo trial in rats. Feeding Groningen rats with a supplementation of B. adolescentis strains, confirmed the ability of these microorganisms to stimulate the in vivo production of GABA highlighting their potential implication in gut-brain axis interactions.

Microbiota of human precolostrum and its potential role as a source of bacteria to the infant mouth.

Human milk represents a source of bacteria for the initial establishment of the oral (and gut) microbiomes in the breastfed infant, however, the origin of bacteria in human milk remains largely unknown. While some evidence points towards a possible endogenous enteromammary route, other authors have suggested that bacteria in human milk are contaminants from the skin or the breastfed infant mouth. In this work 16S rRNA sequencing and bacterial culturing and isolation was performed to analyze the microbiota on maternal precolostrum samples, collected from pregnant women before delivery, and on oral samples collected from the corresponding infants. The structure of both ecosystems demonstrated a high proportion of taxa consistently shared among ecosystems, Streptococcus spp. and Staphylococcus spp. being the most abundant. Whole genome sequencing on those isolates that, belonging to the same species, were isolated from both the maternal and infant samples in the same mother-infant pair, evidenced that in 8 out of 10 pairs both isolates were >99.9% identical at nucleotide level. The presence of typical oral bacteria in precolostrum before contact with the newborn indicates that they are not a contamination from the infant, and suggests that at least some oral bacteria reach the infant's mouth through breastfeeding.

Evaluation of the ability of Bifidobacterium longum to metabolize human intestinal mucus.

The ability of Bifidobacterium longum to use intestinal mucus as a metabolizable source was characterized. Bifidobacterium longum biotype longum NCIMB8809 was grown in a chemically semi-defined medium supplemented with human intestinal mucus, and the cytoplasmic protein profiles and several glycosyl hydrolase activities were analysed and compared with those obtained from the same bacterium grown in the absence of mucus. We were able to identify 22 different proteins in the cytoplasmic fraction, of which nine displayed a different concentration in the presence of mucus. Among the proteins whose concentrations varied, we found specific enzymes that are involved in the response to different environmental conditions, and also proteins that mediate interaction with mucus in bacteria. Significant changes in some glycoside-hydrolysing activities were also detected. In addition, stable isotope labelling of amino acids in cell culture demonstrated that B. longum incorporates leucine from the glycoprotein matrix of mucin within its proteins. This study provides the first proteomic data regarding the interaction of B. longum with intestinal mucus, and contributes to the understanding of the behaviour of this intestinal species in its natural ecological niche.