Three Candidate Probiotic Strains Impact Gut Microbiota and Induce Anergy in Mice with Cow's Milk Allergy.

Cow's milk allergy is a worldwide public health issue, especially since there is no effective treatment, apart from milk and dairy product avoidance. The aim of this study was to assess the beneficial role of three probiotic strains previously selected for their prophylactic properties in a mouse model of ß-lactoglobulin allergy. Administration of Lactobacillus rhamnosus LA305, L. salivarius LA307, or Bifidobacterium longum subsp. infantis LA308 for 3 weeks post-sensitization and challenge modified the composition of the gut microbiota, with an increase in the Prevotella NK3B31 group and a decrease in Marvinbryantia, belonging to the Lachnospiraceae family. Although no impact on markers of sensitization was detected, modifications of foxp3, tgfß, and il10 ileal gene expression, as well as plasma metabolomic alterations in the tryptophan pathway, were observed. Moreover, ex vivo studies showed that all probiotic strains induced significant decreases in cytokine production by ß-lactoglobulin-stimulated splenocytes. Taken together, these results suggest that the three probiotic strains tested lead to alterations in immune responses, i.e., induction of a tolerogenic anergy and anti-inflammatory responses. This anergy could be linked to cecal microbiota modifications, although no impact on fecal short-chain fatty acid (SCFA) concentrations was detected. Anergy could also be linked to a direct impact of probiotic strains on dendritic cells, since costimulatory molecule expression was decreased following coincubation of these strains with bone marrow-derived dendritic cells (BMDCs). To conclude, all three candidate probiotic strains induced strain-specific gut microbiota and metabolic changes, which could potentially be beneficial for general health, as well as anergy, which could contribute to oral tolerance acquisition.IMPORTANCE We showed previously that three probiotic strains, i.e., Lactobacillus rhamnosus LA305, L. salivarius LA307, and Bifidobacterium longum subsp. infantis LA308, exerted different preventive effects in a mouse model of cow's milk allergy. In this study, we evaluated their potential benefits in a curative mouse model of cow's milk allergy. When administered for 3 weeks after the sensitization process and a first allergic reaction, none of the strains modified the levels of sensitization and allergic markers. However, all three strains affected gut bacterium communities and modified immune and inflammatory responses, leading to a tolerogenic profile. Interestingly, all three strains exerted a direct effect on dendritic cells, which are known to play a major role in food sensitization through their potentially tolerogenic properties and anergic responses. Taken together, these data indicate a potentially beneficial role of the probiotic strains tested in this model of cow's milk allergy with regard to tolerance acquisition.

Biofilm Formation and Synthesis of Antimicrobial Compounds by the Biocontrol Agent Bacillus velezensis QST713 in an Agaricus bisporus Compost Micromodel.

Bacillus velezensis QST713 is widely used as a biological control agent for crop protection and disease suppression. This strain is used industrially in France for the protection of Agaricus bisporus against Trichoderma aggressivum f. europaeum, which causes green mold disease. The efficacy of this biocontrol process was evaluated in a previous study, yet the mode of its action has not been explored under production conditions. In order to decipher the underlying biocontrol mechanisms for effective biofilm formation by strain QST713 in the compost and for the involvement of antimicrobial compounds, we developed a simplified micromodel for the culture of A. bisporus during its early culture cycle. By using this micromodel system, we studied the transcriptional response of strain QST713 in the presence or absence of A. bisporus and/or T. aggressivum in axenic industrial compost. We report the overexpression of several genes of the biocontrol agent involved in biofilm formation in the compost compared to their expression during growth in broth compost extract either in the exponential growth phase (the epsC, blsA, and tapA genes) or in the stationary growth phase (the tapA gene), while a gene encoding a flagellar protein (hag) was underexpressed. We also report the overexpression of Bacillus velezensis QST713 genes related to surfactin (srfAA) and fengycin (fenA) production in the presence of the fungal pathogen in the compost.IMPORTANCE Biocontrol agents are increasingly used to replace chemical pesticides to prevent crop diseases. In the button mushroom field in France, the use of Bacillus velezensis QST713 as a biocontrol agent against the green mold Trichoderma aggressivum has been shown to be efficient. However, the biocontrol mechanisms effective in the Agaricus bisporus/Trichoderma aggressivum/Bacillus velezensis QST713 pathosystem are still unknown. Our paper focuses on the exploration of the bioprotection mechanisms of the biocontrol agent Bacillus velezensis QST713 during culture of the button mushroom (Agaricus bisporus) in a micromodel culture system to study the specific response of strain QST713 in the presence of T. aggressivum and/or A. bisporus.

Food-grade TiO2 is trapped by intestinal mucus in vitro but does not impair mucin O-glycosylation and short-chain fatty acid synthesis in vivo: implications for gut barrier protection.

BACKGROUND: Titanium dioxide (TiO2) particles are commonly used as a food additive (E171 in the EU) for its whitening and opacifying properties. However, the risk of gut barrier disruption is an increasing concern because of the presence of a nano-sized fraction. Food-grade E171 may interact with mucus, a gut barrier protagonist still poorly explored in food nanotoxicology. To test this hypothesis, a comprehensive approach was performed to evaluate in vitro and in vivo interactions between TiO2 and intestinal mucus, by comparing food-grade E171 with NM-105 (Aeroxyde P25) OECD reference nanomaterial. RESULTS: We tested E171-trapping properties of mucus in vitro using HT29-MTX intestinal epithelial cells. Time-lapse confocal laser scanning microscopy was performed without labeling to avoid modification of the particle surface. Near-UV irradiation of E171 TiO2 particles at 364 nm resulted in fluorescence emission in the visible range, with a maximum at 510 nm. The penetration of E171 TiO2 into the mucoid area of HT29-MTX cells was visualized in situ. One hour after exposure, TiO2 particles accumulated inside "patchy" regions 20 µm above the substratum. The structure of mucus produced by HT29-MTX cells was characterized by MUC5AC immunofluorescence staining. The mucus layer was thin and organized into regular "islands" located approximately 20 µm above the substratum. The region-specific trapping of food-grade TiO2 particles was attributed to this mucus patchy structure. We compared TiO2-mediated effects in vivo in rats after acute or sub-chronic oral daily administration of food-grade E171 and NM-105 at relevant exposure levels for humans. Cecal short-chain fatty acid profiles and gut mucin O-glycosylation patterns remained unchanged, irrespective of treatment. CONCLUSIONS: Food-grade TiO2 is trapped by intestinal mucus in vitro but does not affect mucin O-glycosylation and short-chain fatty acid synthesis in vivo, suggesting the absence of a mucus barrier impairment under "healthy gut" conditions.

Chlorpyrifos Exposure During Perinatal Period Affects Intestinal Microbiota Associated With Delay of Maturation of Digestive Tract in Rats.

OBJECTIVES: Pesticide exposure via residues in food may be especially harmful when it takes place in the developing child. The present study was designed to assess the impact of perinatal exposure to chlorpyrifos (CPF, an insecticide known to cross the placental barrier). METHODS: Female rats were exposed to oral CPF (1 or 5 mg kg day vs vehicle controls) from gestation onset up to weaning of the pups that were individually gavaged (CPF or vehicle) thereafter. Two developmental time points were studied: weaning (day 21) and adulthood (day 60). After sacrifice, samples from the intestinal tract and other organs underwent microbiological and histological analyses. RESULTS: Rat pups exposed to 5 mg kg day CPF were both significantly smaller (body length) and lighter than controls. Exposure to CPF was associated with changes in the histological structures (shorter and thinner intestinal villosities), an intestinal microbial dysbiosis, and increased bacterial translocation in the spleen and liver. These significant microbial changes in the gut were associated with impaired epithelium protection (mucin-2) and microbial pattern recognition receptor (Toll-like 2 and 4) gene expression. CONCLUSIONS: Exposure to CPF during gestation and development affected the pups' intestinal development, with morphological alteration of the structures involved in nutrient absorption, intestinal microbial dysbiosis, alteration of mucosal barrier (mucin-2), stimulation of the innate immune system, and increased bacterial translocation. Perinatal exposure to CPF may therefore have short- and long-term impacts on the digestive tract.

Primocolonization is associated with colonic epithelial maturation during conventionalization.

Interaction between the gut microbiota and the host starts immediately after birth with the progressive colonization of the sterile intestine. Our aim was to investigate the interactions taking place in the colonic epithelium after the first exposure to gut microbiota. Germ-free (GF) rats were inoculated with two different microbiotas: the first, obtained from suckling rats, was rich in primocolonizing bacteria and the second, obtained from adult rats, was representative of a mature microbiota. Once transferred into GF rats, these two microbiotas evolved such that they converged, and recapitulated the primocolonization pattern, mimicking the chronological scheme of implantation following birth. The two microbiotas induced common responses in the colonic epithelium: a transitory proliferative phase followed by a compensatory phase characterized by increases in the abundance of p21(Cip1) and p27(Kip1) and in the number of goblet cells. The effects of the two microbiotas diverged only through their effects on colonic transporters. Analyses of solute carriers and aquaporins revealed that functional maturation was more pronounced following exposure to adult microbiota than suckling microbiota. The colon matured in parallel with the evolution of the microbiota composition, and we therefore suggest a link between intestinal events regulating homeostasis of the colon and modulation of microbial composition.

Fecal microbiota transplantation in a rodent model of short bowel syndrome: A therapeutic approach?

Extensive intestinal resection leads to Short Bowel Syndrome (SBS), the main cause of chronic intestinal failure. Colon preservation is crucial for spontaneous adaptation, to improve absorption and reduce parenteral nutrition dependence. Fecal microbiota transplantation (FMT), a promising approach in pathologies with dysbiosis as the one observed in SBS patients, was assessed in SBS rats with jejuno-colonic anastomosis. The evolution of weight and food intake, the lenght of intestinal villi and crypts and the composition of fecal microbiota of Sham and SBS rats, transplanted or not with high fat diet rat microbiota, were analyzed. All SBS rats lost weight, increased their food intake and exhibited jejunal and colonic hyperplasia. Microbiota composition of SBS rats, transplanted or not, was largely enriched with Lactobacillaceae, and α- and ß-diversity were significantly different from Sham. The FMT altered microbiota composition and α- and ß-diversity in Sham but not SBS rats. FMT from high fat diet rats was successfully engrafted in Sham, but failed to take hold in SBS rats, probably because of the specific luminal environment in colon of SBS subjects favoring aero-tolerant over anaerobic bacteria. Finally, the level of food intake in SBS rats was positively correlated with their Lactobacillaceae abundance. Microbiota transfer must be optimized and adapted to this specific SBS environment.

Lacticaseibacillus casei CNCM I-5663 supplementation maintained muscle mass in a model of frail rodents.

The aim of this study was to identify a probiotic-based strategy for maintaining muscle anabolism in the elderly. In previous research, we found that individuals experiencing short bowel syndrome (SBS) after an intestinal resection displayed beneficial metabolic adjustments that were mediated by their gut microbes. Thus, these bacteria could potentially be used to elicit similar positive effects in elderly people, who often have low food intake and thus develop sarcopenia. Gut bacterial strains from an SBS patient were evaluated for their ability to (1) maintain Caenorhabditis elegans survival and muscle structure and (2) promote protein anabolism in a model of frail rodents (18-month-old rats on a food-restricted diet: 75% of ad libitum consumption). We screened a first set of bacteria in C. elegans and selected two Lacticaseibacillus casei strains (62 and 63) for further testing in the rat model. We had four experimental groups: control rats on an ad libitum diet (AL); non-supplemented rats on the food-restricted diet (R); and two sets of food-restricted rats that received a daily supplement of one of the strains (∼109 CFU; R+62 and R+63). We measured lean mass, protein metabolism, insulin resistance, cecal short-chain fatty acids (SCFAs), and SCFA receptor expression in the gut. Food restriction led to decreased muscle mass [-10% vs. AL (p < 0.05)]. Supplementation with strain 63 tempered this effect [-2% vs. AL (p > 0.1)]. The mechanism appeared to be the stimulation of the insulin-sensitive p-S6/S6 and p-eIF2α/eIF2α ratios, which were similar in the R+63 and AL groups (p > 0.1) but lower in the R group (p < 0.05). We hypothesize that greater SCFA receptor sensitivity in the R+63 group promoted gut-muscle cross talk [GPR41: +40% and GPR43: +47% vs. R (p < 0.05)]. Hence, strain 63 could be used in association with other nutritional strategies and exercise regimes to limit sarcopenia in frail elderly people.

Corrigendum: Lacticaseibacillus casei CNCM I-5663 supplementation maintained muscle mass in a model of frail rodents.

[This corrects the article DOI: 10.3389/fnut.2022.928798.].

Nitric Oxide Impacts Human Gut Microbiota Diversity and Functionalities.

The disruption of gut microbiota homeostasis has been associated with numerous diseases and with a disproportionate inflammatory response, including overproduction of nitric oxide (NO) in the intestinal lumen. However, the influence of NO on the human gut microbiota has not been well characterized yet. We used in vitro fermentation systems inoculated with human fecal samples to monitor the effect of repetitive NO pulses on the gut microbiota. NO exposure increased the redox potential and modified the fermentation profile and gas production. The overall metabolome was modified, reflecting less strict anaerobic conditions and shifts in amino acid and nitrogen metabolism. NO exposure led to a microbial shift in diversity with a decrease in Clostridium leptum group and Faecalibacterium prausnitzii biomass and an increased abundance of the Dialister genus. Escherichia coli, Enterococcus faecalis, and Proteus mirabilis operational taxonomic unit abundance increased, and strains from those species isolated after NO stress showed resistance to high NO concentrations. As a whole, NO quickly changed microbial fermentations, functions, and composition in a pulse- and dose-dependent manner. NO could shift, over time, the trophic chain to conditions that are unfavorable for strict anaerobic microbial processes, implying that a prolonged or uncontrolled inflammation has detrimental and irreversible consequences on the human microbiome. IMPORTANCE Gut microbiota dysbiosis has been associated with inflammatory diseases. The human inflammatory response leads to an overproduction of nitric oxide (NO) in the gut. However, so far, the influence of NO on the human gut microbiota has not been characterized. In this study, we used in vitro fermentation systems with human fecal samples to understand the effect of NO on the microbiota: NO modified the microbial composition and its functionality. High NO concentration depleted the microbiota of beneficial butyrate-producing species and favored potentially deleterious species (E. coli, E. faecalis, and P. mirabilis), which we showed can sustain high NO concentrations. Our work shows that NO may participate in the vicious circle of inflammation, leading to detrimental and irreversible consequences on human health.

Gut microbiota-derived short-chain fatty acids regulate IL-17 production by mouse and human intestinal γδ T cells.

Gut interleukin-17A (IL-17)-producing γδ T cells are tissue-resident cells that are involved in both host defense and regulation of intestinal inflammation. However, factors that regulate their functions are poorly understood. In this study, we find that the gut microbiota represses IL-17 production by cecal γδ T cells. Treatment with vancomycin, a Gram-positive bacterium-targeting antibiotic, leads to decreased production of short-chain fatty acids (SCFAs) by the gut microbiota. Our data reveal that these microbiota-derived metabolites, particularly propionate, reduce IL-17 and IL-22 production by intestinal γδ T cells. Propionate acts directly on γδ T cells to inhibit their production of IL-17 in a histone deacetylase-dependent manner. Moreover, the production of IL-17 by human IL-17-producing γδ T cells from patients with inflammatory bowel disease (IBD) is regulated by propionate. These data contribute to a better understanding of the mechanisms regulating gut γδ T cell functions and offer therapeutic perspectives of these cells.

Long-Term Overconsumption of Fat and Sugar Causes a Partially Reversible Pre-inflammatory Bowel Disease State.

Nutrition appears to be an important environmental factor involved in the onset of inflammatory bowel diseases (IBD) through yet poorly understood biological mechanisms. Most studies focused on fat content in high caloric diets, while refined sugars represent up to 40% of caloric intake within industrialized countries and contribute to the growing epidemics of inflammatory diseases. Herein we aim to better understand the impact of a high-fat-high-sucrose diet on intestinal homeostasis in healthy conditions and the subsequent colitis risk. We investigated the early events and the potential reversibility of high caloric diet-induced damage in mice before experimental colitis. C57BL/6 mice were fed with a high-fat or high-fat high-sucrose or control diet before experimental colitis. In healthy mice, a high-fat high-sucrose diet induces a pre-IBD state characterized by gut microbiota dysbiosis with a total depletion of bacteria belonging to Barnesiella that is associated with subclinical endoscopic lesions. An overall down-regulation of the colonic transcriptome converged with broadly decreased immune cell populations in the mesenteric lymph nodes leading to the inability to respond to tissue injury. Such in-vivo effects on microbiome and transcriptome were partially restored when returning to normal chow. Long-term consumption of diet enriched in sucrose and fat predisposes mice to colitis. This enhanced risk is preceded by gut microbiota dysbiosis and transcriptional reprogramming of colonic genes related to IBD. Importantly, diet-induced transcriptome and microbiome disturbances are partially reversible after switching back to normal chow with persistent sequelae that may contribute to IBD predisposition in the general population.

Microbiota matures colonic epithelium through a coordinated induction of cell cycle-related proteins in gnotobiotic rat.

Previous studies have suggested that intestinal microbiota modulates colonic epithelium renewal. The objective of our work was to study the effects of microbiota on colonic epithelium structure and cell cycle-related proteins by using gnotobiotic rats. Colonic crypts and amount of cell cycle-related proteins were compared between germ-free (GF), conventional (CV), and conventionalized rats by histochemistry and Western blot. Ki67 and proliferating cell nuclear antigen (PCNA) were used as surrogates for proliferative cells; p21(cip1) and p27(kip1) were markers of cell cycle arrest; anti- and proapoptotic proteins, Bcl2 and Bax, respectively, were also studied. We observed 40% increase of the crypt proliferative area 2 days after inoculation of GF rats with a complex microbiota. This recruitment of proliferative cells may account for the 30% increase of crypt depth observed between CV and GF rats. The hyperproliferative boost induced by microbiota was compensated by a fourfold increase of p21(cip1) and p27(kip1) involved in cell cycle arrest and a 30% drop of antiapoptotic Bcl2 protein while Bax was unchanged. Inductions of p21(cip1), p27(kip1), and PCNA protein were not paralleled by an increase of the corresponding mRNA. We also showed that p21(cip1) induction by microbiota was partially restored by Bacteroides thetaiotaomicron, Ruminococcus gnavus, and Clostridium paraputrificum. Colonization of the colon by a complex microbiota increases the crypt depth of colon epithelium. This event takes place in conjunction with a multistep process: a hyperproliferative boost accompanied by compensatory events as induction of p21(cip1) and p27(kip1) and decrease of Bcl2.

Freeze-dried fecal samples are biologically active after long-lasting storage and suited to fecal microbiota transplantation in a preclinical murine model of Clostridioides difficile infection.

Fecal microbiota transplantation is now recommended for treating recurrent forms of Clostridioides difficile infection. Recent studies have reported protocols using capsules of either frozen or freeze-dried stool allowing oral administration in in- and out-patient settings. However, a central question remains the viability, engraftment, and efficacy of the microbiome over time during storage life. This study shows that both the freeze-drying and freezing procedures for fecal samples allowed preserving viability, short-chain fatty acids concentration, and anti-Clostridioides difficile properties of microbiota without significant alteration after storage for 12 months. Fecal transplantation with freeze-dried microbiota allowed engraftment of microbiota leading to clearance of Clostridioides difficile infection in a preclinical murine model with a survival rate of 70% versus 53-60% in mice treated with frozen inocula, and 20% in the untreated group. Moreover, the freeze-dried powder can be used to fill oral hard capsules using a very low amount (0.5%) of glidant excipient, allowing oral formulation. Altogether, this study showed that freeze-dried inocula can be used for the treatment of Clostridioides difficile infection with long-lasting stability of the fecal microbiota. This formulation facilitates biobanking and allows the use of hard capsules, an essential step to simplify patient access to treatment.

Functional and phylogenetic alterations in gut microbiome are linked to graft-versus-host disease severity.

Acute graft-versus-host disease (aGVHD) is the main complication of hematopoietic stem cell transplantation (HSCT). Changes in gut microbiota composition have been associated with subsequent aGVHD, and reconstitution of healthy microbiota is currently being explored as a therapeutic approach. However, the specific actors in the intestinal ecosystem involved in the pathologic process at the time of aGVHD onset are not yet fully known. We prospectively collected stool samples from patients who underwent allogeneic HSCT. Patients sampled at aGVHD onset were compared with non-GVHD patients. To identify phylogenetic and functional signatures of the disease process, we determined fecal short-chain fatty acid (SFCA) profiles and used high-throughput DNA sequencing and real-time quantitative polymerase chain reaction to assess the microbiota composition. Microbiota alterations were highly specific of gastrointestinal (GI) aGVHD severity. Bacterial biomass and α-diversity were lower in severe aGVHD. We identified several bacterial signatures associated with severe aGVHD at disease onset; a negative correlation was observed with anaerobic bacteria of the Lachnospiraceae, especially the Blautia genus, and Ruminococcaceae families. In parallel, in severe aGVHD patients, we showed a dramatic decrease in the levels of the main SFCAs: acetate (75.8%), propionate (95.8%), and butyrate (94.6%). Mild aGVHD patients were characterized by conserved levels of propionate and Blautia propionate producers. Butyrate was significantly decreased in all GI aGVHD stages, representing a potential diagnostic marker of the disease. Specific microbiota and metabolic alterations were thus associated with aGVHD severity and may be useful for diagnostic and pathophysiologic purposes.

Impact and consequences of intensive chemotherapy on intestinal barrier and microbiota in acute myeloid leukemia: the role of mucosal strengthening.

Induction chemotherapy (7 + 3 regimen) remains the gold standard for patients with acute myeloid leukemia (AML) but is responsible for gut damage leading to several complications such as bloodstream infection (BSI). We aimed to investigate the impact of induction chemotherapy on the intestinal barrier of patients with AML and in wild-type mice. Next, we assessed the potential benefit of strengthening the mucosal barrier in transgenic mice releasing a recombinant protein able to reinforce the mucus layer (Tg222). In patients, we observed a decrease of plasma citrulline, which is a marker of the functional enterocyte mass, of short-chain fatty acids and of fecal bacterial load, except for Escherichia coli and Enterococcus spp., which became dominant. Both the α and ß-diversities of fecal microbiota decreased. In wild-type mice, citrulline levels decreased under chemotherapy along with an increase of E. coli and Enterococcus spp load associated with concomitant histologic impairment. By comparison with wild-type mice, Tg222 mice, 3 days after completing chemotherapy, had higher citrulline levels, a faster healing epithelium, and preserved α-diversity of their intestinal microbiota. This was associated with reduced bacterial translocations. Our results highlight the intestinal damage and the dysbiosis induced by the 7 + 3 regimen. As a proof of concept, our transgenic model suggests that strengthening the intestinal barrier is a promising approach to limit BSI and improve AML patients' outcome.

Morphological adaptation with preserved proliferation/transporter content in the colon of patients with short bowel syndrome.

In short bowel syndrome (SBS), although a remaining colon improves patient outcome, there is no direct evidence of a mucosal colonic adaptation in humans. This prospective study evaluates morphology, proliferation status, and transporter expression level in the epithelium of the remaining colon of adult patients compared with controls. The targeted transporters were Na+/H+ exchangers (NHE2 and 3) and oligopeptide transporter (PepT1). Twelve adult patients with a jejuno-colonic anastomosis were studied at least 2 yr after the last surgery and compared with 11 healthy controls. The depth of crypts and number of epithelial cells per crypt were quantified. The proliferating and apoptotic cell contents were evaluated by revealing Ki67, PCNA, and caspase-3. NHE2, NHE3, PepT1 mRNAs, and PepT1 protein were quantified by quantitative RT-PCR and Western blot, respectively. In patients with SBS compared with controls, 1) hyperphagia and severe malabsorption were documented, 2) crypt depth and number of cells per crypt were 35% and 22% higher, respectively (P < 0.005), whereas the proliferation and apoptotic levels per crypt were unchanged, and 3) NHE2 mRNA was unmodified; NHE3 mRNA was downregulated near the anastomosis and unmodified distally, and PepT1 mRNA and protein were unmodified. We concluded that, in hyperphagic patients with SBS with severe malabsorption, adaptive colonic changes include an increased absorptive surface with an unchanged proliferative/apoptotic ratio and well-preserved absorptive NHE2, NHE3, and PepT1 transporters. This is the first study showing a controlled nonpharmacological hyperplasia in the colon of patients with SBS.

Modulation of the Caecal Gut Microbiota of Mice by Dietary Supplement Containing Resistant Starch: Impact Is Donor-Dependent.

Alterations in the gut microbiota have been associated with a wide range of pathologies and conditions. Maintaining a well-balanced microbiota is a key factor in sustaining good health. Our aim was to investigate the impact of a resistant starch-containing dietary supplement (SymbioIntest®) on the composition of the human gut microbiota and on intestinal short chain fatty acid (SCFA) concentration. Human microbiota-associated mice were used. Ex-germ-free mice were inoculated with fecal suspensions from four different donors. Three weeks later, the mice were orally gavaged for 1 month with either a daily dose of 10 mg of SymbioIntest® or the vehicle (water) for the negative control group. The composition of the microbiota and SCFA levels were analyzed by 16S rRNA gene sequencing and gas chromatography, respectively. In three groups of mice, SymbioIntest® supplementation increased the concentration of caecal butyrate. This was in conjunction with a remodeling of the gut microbiota. OTUs belonging to the Bacteroidaceae, Porphyromonadaceae, Lachnospiraceae and Ruminococcaceae families were affected. In two groups of mice the greatest changes in OTUs were seen in the Faecalibacterium genus. The supplementation's highest impact was observed in mice inoculated with gut microbiota containing a lower number of Ruminococcaceae and Faecalibacterium and a higher number of Prevotellaceae. SymbioIntest® supplementation elicited a beneficial effect on the healthy adult gut microbiota by increasing caecal butyrate production and health-promoting taxa. We highlight the fact that screening the gut microbiota may be used for predicting individualized responses to dietary interventions and thus developing personalized nutritional strategies.

Transplantation of human microbiota into conventional mice durably reshapes the gut microbiota.

Human microbiota-associated (HMA) mice are an important model to study the relationship between liver diseases and intestinal microbiota. We describe a new method to humanize conventional mice based on bowel cleansing with polyethylene glycol followed by fecal microbiota transplantation (FMT) from a human donor. Four successive bowel cleansings were sufficient to empty the intestine and decrease the microbiota by 90%. We then compared four different strategies based on the frequency of FMT over four weeks: (1) twice a week; (2) once a week; (3) two FMTs; (4) one FMT. We were able to transfer human bacteria to mice, irrespective of the strategy used. We detected human bacteria after four weeks, even if only one FMT was performed, but there was a shift of the microbiota over time. FMT twice a week for four weeks was too frequent and perturbed the stability of the newly formed ecosystem. FMT once a week appears to be the best compromise as it allowed engraftment of Faecalibacterium, and a higher diversity of bacteria belonging to the Bacteroidales order. Our easy to establish HMA mouse model could be used as an alternative to classical HMA mice to study the relationship between the liver and the microbiota.

Microbiota Is Involved in Post-resection Adaptation in Humans with Short Bowel Syndrome.

Short bowel syndrome (SBS) is characterized by severe intestinal malabsorption following restrictive surgery. The objective of this study was to determine the functional contribution of SBS-microbiota after resection. It is well-known that SBS-microbiota displayed specific features with a prevalence of Lactobacillus, a low amount of some anaerobic microbes (Clostridium leptum) and an accumulation of fecal lactate in some patients. Patients with jejuno-colonic anastomosis were stratified according to the presence of lactate in their feces and, we observe that the lactate-producing bacteria were predominant in the sub-group of patients accumulating fecal lactate. One case of D-encephalopathy crisis occurred when the D-lactate isoform accumulated in the feces and plasma bicarbonate levels decreased. The fecal sample at the time of the encephalopathy was transferred to germ free rats (SBS-H rats). The SBS-H microbiota conserved some characteristics of the SBS donnor, predominated by lactate-producing bacteria (mainly Lactobacillus), a low level of lactate-consuming bacteria and undetectable C. leptum. However, lactate did not accumulate in feces of recipient rats and the D-encephalopathy was not reproduced in SBS-H rats. This suggests that the intact small bowel of the recipient rats protected them from lactate accumulation and that D-lactate encephalopathy can occur only in the absence of small intestine. After fecal transfer, we also show that gnotobiotic rats exhibited high levels of circulating GLP-1 and ghrelin, two hormones that are known to be induced in SBS patients. Therefore, the microbiota of SBS is a reservoir of biological signals involved in post-resection adaptation.

Structure of protein emulsion in food impacts intestinal microbiota, caecal luminal content composition and distal intestine characteristics in rats.

SCOPE: Few studies have evaluated in vivo the impact of food structure on digestion, absorption of nutrients and on microbiota composition and metabolism. In this study we evaluated in rat the impact of two structures of protein emulsion in food on gut microbiota, luminal content composition, and intestinal characteristics. METHODS AND RESULTS: Rats received for 3 weeks two diets of identical composition but based on lipid-protein matrices of liquid fine (LFE) or gelled coarse (GCE) emulsion. LFE diet led to higher abundance, when compared to the GCE, of Lactobacillaceae (Lactobacillus reuteri) in the ileum, higher ß-diversity of the caecum mucus-associated bacteria. In contrast, the LFE diet led to a decrease in Akkermansia municiphila in the caecum. This coincided with heavier caecum content and higher amount of isovalerate in the LFE group. LFE diet induced an increased expression of (i) amino acid transporters in the ileum (ii) glucagon in the caecum, together with an elevated level of GLP-1 in portal plasma. However, these intestinal effects were not associated with modification of food intake or body weight gain. CONCLUSION: Overall, the structure of protein emulsion in food affects the expression of amino acid transporters and gut peptides concomitantly with modification of the gut microbiota composition and activity. Our data suggest that these effects of the emulsion structure are the result of a modification of protein digestion properties.