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. 2024 Nov 23;24:493. doi: 10.1186/s12866-024-03647-0

Effects of Saccharomyces boulardii on microbiota composition and metabolite levels in the small intestine of constipated mice

Shuai Tang 1,2,#, Jia Li 3,#, Yi Li 4, Haitao Du 2, Wenya Zhu 5, Ru Zhang 2,✉, Jun Wan 2,✉
PMCID: PMC11585213  PMID: 39578737

Abstract

Saccharomyces boulardii (S. boulardii) is a fungal probiotic used to treat digestive disorders. However, the mechanism(s) by which S. boulardii affects the small intestine remains unclear. Here, we aimed to explore the effects of S. boulardii on the small intestine and the underlying mechanisms in mice with loperamide-induced constipation. While S. boulardii administration did not fully reverse the alterations in loperamide-induced defecation parameters, it altered the small intestinal floral composition toward a community conducive to alleviate constipation. Moreover, S. boulardii up-regulated the expression of tyrosine-protein kinase Kit (c-Kit), aquaporin 3 (AQP3), interleukin (IL)-10, myosin light chain kinase (MLCK), and phosphorylated myosin light chain 20 (P-MLC20), while concurrently down-regulating the expression levels of inducible nitric oxide synthase (iNOS), p65, and IL-17 A. These alterations indicate a discernible effect of small intestinal water reabsorption, inflammatory factor levels, and smooth muscle contraction. Saccharomyces boulardii also positively regulated small intestinal metabolite levels, such as fructose 6-phosphate, dihomo-alpha-linolenic acid, and 3-(4-hydroxyphenyl) lactate, and participated in metabolic pathways such as arginine biosynthesis, linoleic acid metabolism, and protein digestion and absorption. While not fully reversing defecation changes, Saccharomyces boulardii alters intestinal flora, up-regulates key proteins affecting water reabsorption and inflammation, and positively influences metabolic pathways. Our study provides serves as a basis for further studies on the application of S. boulardii in the treatment of intestinal disorders.

Keywords: Saccharomyces boulardii, Constipation, Loperamide, Metabolite, KEGG pathway

Introduction

Constipation, characterised by prolonged intestinal transit times, hard faeces, difficulty in defecation, and decreased stool frequency, considerably affects the quality of life [1, 2]. This condition is associated with an increased risk of harmful microorganism proliferation in the intestine, impairing intestinal peristalsis [3]. Additionally, long-term accumulation of toxic substances can contribute to the development of other intestinal diseases [4]. Regarding the pathogenesis of constipation, previous studies have primarily focused on alterations in interstitial cells of Cajal (ICCs), recognised as gastrointestinal pacemaker cells [5]. Notably, patients with slow-transit constipation (STC) exhibit a reduced count of ICCs in resected colon [6]. Additionally, various pathophysiological abnormalities such as myenteric plexus degeneration, abnormal smooth muscle cell protein expression, and altered neurotransmitter levels in the enteric nervous system have been linked to the development of constipation. Functional constipation, excluding irritable bowel syndrome (IBS), is associated with enteric nervous system dysfunction and intestinal motor irregularities without an organic aetiology, structural abnormalities, or metabolic disorders.

Saccharomyces boulardii (S. boulardii), a non-pathogenic yeast known for its immune-regulatory and composition-modulating properties, is used in clinical settings [7]. It regulates short-chain fatty acid (SCFA) levels, and preserves normal intestinal functions [8]. Moreover, S. boulardii can synthesise and release polyamines, enhance intestinal digestive enzyme activities, and upregulate nutrient transport system activity [9]. Furthermore, S. boulardii can modulate the expression of inflammatory factors, preserve the integrity of gastrointestinal mucosal barrier by promoting tight junction protein secretion, and directly bind to pathogens, inhibiting their interactions with intestinal epithelial cells [10]. Saccharomyces boulardii ameliorates intestinal dysmotility caused by herpes simplex virus type 1 (HSV-1), decreases the production of HSV-1-related pro-inflammatory cytokines (tumour necrosis factor-α and interleukin (IL)-1β), and increases the levels of anti-inflammatory factors (IL-4 and IL-10) [11].

Most of the available treatments for constipation are not suitable for long-term application, and the abuse of laxative drugs is common. We are trying to identify beneficial microorganisms that are effective against constipation. The precise mechanism by which S. boulardii regulates intestinal motility remains unclear. The role of S. boulardii in regulating inflammation and the microbiological structure in the intestinal tract inspired this study.

Loperamide hydrochloride is a synthetic drug whose pharmacological properties simulate clinical constipation. Bifidobacteria maintain the intestinal environment stable, inhibit inflammation, and affect the microflora and metabolite levels. The antibacterial spectrum of metronidazole includes anaerobes, which may improve constipation by inhibiting the growth of methanogens. Our study mainly focused on the changes in small intestinal movement and protein and inflammation levels, and explored the differences in small intestinal flora under different interventions. Therefore, we aimed to elucidate the effects of bifidobacteria, S. boulardii, and metronidazole on the small intestine of loperamide-induced constipated mice and monitor the associated alterations in intestinal flora, key protein expression, and inflammatory factors.

Materials and methods

Animals

Thirty healthy male C57BL/6 mice aged 6 weeks were obtained from SPF Biotechnology Co., Ltd. (Beijing, China). All mice were housed in cages maintained under standard animal housing conditions with accessible food and water ad libitum. After a 7-day-acclimatisation period at 25 °C ± 2 °C under a 12-:12-h light–dark cycle, the mice were randomly divided into five groups: normal control (NC), model control (MC), bifidobacteria (BB), S. boulardii (SB), and metronidazole (MN) groups (n = 6/group). Mice in the NC group received 0.1 mL/10 g body weight (BW) of 0.9% normal saline per day and those in the other groups were orally administered 10 mg/kg BW of loperamide solution (1 mg/mL) at 10 am daily. After an hour, the BB group mice were administered 24 mg/kg BW bifidobacterial solution, the SB group mice were administered 384 mg/kg BW S. boulardii solution [12], and the MN group mice were administered 60 mg/kg BW metronidazole solution. All solutions were administered intragastrically using gavage needles, and the process was repeated for 14 successive days (Fig. 1A). The mice were anesthetized with sodium pentobarbital and killed via cervical dislocation on day 15 for intestinal dissection, and their small intestine contents and tissues were collected and stored at − 80 °C. The small intestine contents were analysed for microbiota using 16 S ribosomal RNA gene sequencing. The tissues were used for protein analysis using western blotting and metabolite analysis using untargeted metabolomic techniques. The animal experimental protocols were approved by the Animal Ethics Committee of People’s Liberation Army General Hospital, Beijing, China (2022-X18-71).

Fig. 1.

Fig. 1

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Effects of Saccharomyces boulardii on loperamide-induced mice. (A) Animal experimental flowchart. (B) Body weight. (C) Fecal weight. (D) Water content. (E) Small intestinal transit rate. (F) Time of first black stool. All data were expressed as mean ± SD (n = 6). ###P<0.001, ##P < 0.01, #P < 0.05, MC vs NC. ***P < 0.001, **P < 0.01, *P < 0.05, BB, SB and MN vs MC

Reagents

Normal saline was obtained from Shijiazhuang No.4 Pharmaceutical Co., Ltd, China. Loperamide hydrochloride (2 mg per capsule) was obtained from Xian Janssen Pharmaceutical Co., Ltd., China. It was prepared at a final concentration of 1 mg/mL following dilution with sterile normal saline. Saccharomyces boulardii (0.25 g; CNCM I-745, BIOCODEX, France) at 1.3 × 109 CFU/g was diluted in sterile distilled water to a final concentration of 5 × 107 CFU/mL. Bifidobacterium (0.35 g; SHBCC D80243, Lizhu Pharmaceutical Factory, Guangdong, China) was diluted to a concentration of 2.4 mg/mL using sterile distilled water. Metronidazole (0.2 g; Yabao Pharmaceutical Group, Shanxi, China) was diluted in sterile distilled water to a concentration of 6 mg/mL. Activated carbon was purchased from Fangzheng Reagent Factory, Tianjin, China. Briefly, 50 g of Arabic gum and 400 mL of water were heated with stirring until a clear liquid was obtained. Next, 25 g of activated carbon was added to the solution, heated, and stirred until the suspension was evenly mixed. The liquid was then cooled to room temperature and made up to a final volume of 500 mL using water. Before use, the solution was mixed. MLCK antibody (21642-1-AP) and MLC20 antibody (10324-1-AP) were obtained from Sanying Biotechnology, Wuhan, China. P-MLC20 antibody (bs-8311R) and AQP3 antibody (bs-1253R) were obtained from Bioss Biotechnology, Beijing, China. INOS antibody (AF0199), C-kit antibody (AF6152), p65 antibody (AF5006), IL-17 A antibody (DF6127), and IL-10 antibody (DF6894) were obtained from Affinity Bioreagents, USA. Beta-actin monoclonal antibody (66009-1-Ig) was used as the loading control (Sanying Biotechnology, Wuhan, China).

Defaecation parameters

Defaecation parameters including faecal weight, dry weight, and water content were measured. Faecal samples were collected weekly. The mice were individually housed and observed for 2 h. Their faeces were collected, weighed (wet weight), and then dried at 37 °C for 24 h. Faecal water content (%) was calculated as follows: [(wet weight − dry weight) / wet weight] ×100%. Each mouse received 0.2 mL of activated carbon solution by gavage 1 day before the last day of the experiment. The time from the administration of activated carbon to the first appearance of black stool was recorded. On day 15. the mice were intragastrically administered activated carbon solution (0.2 mL). Subsequently, they were subjected to anaesthesia and euthanised; their small intestines were dissected to measure the total length and travel distance of the activated carbon solution after 30 min. Small intestinal transit rate (%) was calculated as follows: (transited distance by the activated carbon / total length of the small intestine)× 100%.

SCFA measurement

After homogenising the samples (0.1 g) in a methanol mixture containing 10% 2-ethylbutyric acid, the mixture was centrifuged for 10 min at 12,000 g. An Agilent 6890 N/5975B gas chromatography-mass spectrometry apparatus fitted with an HP-INNOWAXax GC column (Agilent, Santa Clara, CA, USA) was used to analyse the supernatants (1 µL). The carrier gas used was helium (flow rate: 1.0 mL/min, split ratio: 10:1).

Western blotting

Small intestinal tissue lysates were dissolved in radioimmunoprecipitation assay lysis buffer, supplemented with phenylmethylsulphonyl fluoride (P105539; Aladdin Biochemical Technology, Shanghai, China) and phosphatase inhibitors (S1873; Beyotime Biotech, Inc., Shanghai, China). The protein concentration of the lysates was estimated using a bicinchoninic acid (BCA) protein detection kit (P0010; Beyotime Biotech, Shanghai, China). The resulting absorbance was measured using a microplate reader (DG-3022 A). Subsequently, proteins were separated using sodium dodecyl sulphate polyacrylamide gel electrophoresis and transferred onto polyvinylidene difluoride membranes (Millipore, USA) using transfer buffer composed of Tris-base (1115GR500; BioFroxx) and glycine (1275GR500; BioFroxx). The membranes were blocked with 5% skimmed milk in Tris-buffered saline Tween-20 (TBST) for 2 h and incubated with primary antibodies (1:1000) overnight at 4 °C. Subsequently, the membranes were washed with TBST five times and incubated with horseradish peroxidase-conjugated secondary antibodies (1:10000; Boster Biological Technology, Wuhan, China) for 2 h at room temperature. The membranes were washed again with TBST five times. The enhancer solution in ECL reagent (P1050; Beijing Pulilai Gene Technology Co., Ltd.) was mixed with the stable peroxidase solution at a 1:1 ratio, and the working solution was added on the PVDF membranes. After incubation for several minutes and the fluorescent band was obvious, the excess substrate solution was aspirated with filter paper and covered with plastic film. A developer and fixer kit (Hanzhong Photography Materials Factory, Tianjin, China) was used to detect the protein bands and the grey-scale values were analysed using image-pro plus.

16 S rRNA gene sequencing

Fresh small intestinal contents were preserved at − 80 °C. Microbial DNA was isolated and amplified using polymerase chain reaction (PCR). The following primers targeting the bacterial V3–V4 region of the 16 S rRNA gene were used: 338 F (5ʹ-ACTCCTACGGGAGGCAGCAG-3ʹ) and 806R (5ʹ-GGACTACHVGGGTWTCTAAT-3ʹ). The AxyPrep DNA Gel Extraction Kit (Axygen Biosciences, Union City, CA, USA) was used to purify the recovered products, which were then subjected to 2% agarose gel electrophoresis for further analysis. The concentration of the PCR products was determined using a Quantus™ Fluorometer (Promega, USA). Following the standard protocols of Majorbio Bio-Pharm Technology Co., Ltd. (Shanghai, China), the purified amplicons were subjected to paired-end sequencing using an Illumina MiSeq PE300 platform (Illumina, San Diego, CA, USA). After noise reduction to optimise the data, an amplicon sequence variant (ASV) representing sequence and abundance information was generated. Taxonomic analysis of ASVs was conducted using the Silva 16 S rRNA database (v138). Alpha diversity indices and rarefaction curves were calculated based on the ASV data. Bray–Curtis dissimilarity was used in principal co-ordinate analysis (PCoA) to determine the similarity of microbial communities. Significantly abundant bacterial taxa among various groups were determined using linear discriminant analysis (LDA) effect size (LEfSe).

UPLC-MS/MS analysis of metabolites

A grinding bead was placed in a 2-mL centrifuge tube along with 50 mg of solid sample. Metabolites were extracted using 400 µL of extraction solution containing 0.02 mg/mL of the internal standard L-2-chlorophenylalanine (Shanghai Aladdin Biochemical Technology Co., Ltd., Shanghai, China). The Wonbio-96c frozen tissue grinder (Shanghai Wanbo Biotechnology Co., Ltd.) was used to grind the samples for 6 min (-10 °C, 50 Hz). Thereafter, the samples were extracted for 30 min using low-temperature ultrasonic vibration (5 °C, 40 kHz). The samples were stored at -20 °C for 30 min before being centrifuged at 13,000 g for 15 min at 4 °C. For LC-MS/MS analysis, the supernatant was subsequently transferred into an injection vial. A quality control sample was prepared by extracting and mixing 20 µL of supernatant from each sample. The Thermo UHPLC-Q Exactive HF-X system (Thermo Fisher, USA) equipped with an ACQUITY HSS T3 column (100 mm × 2.1 mm i.d., 1.8 μm; Waters, USA) was used to analyse the samples.

Statistical analysis

IBM SPSS 27.0 (SPSS Institute, USA) and GraphPad Prism 9.51 (San Diego, CA, USA) were used for data analysis and plotting, respectively. Results are expressed as mean ± standard deviation. A one-way analysis of variance was performed using Tukey–Kramer or Dunnett post-hoc test. P < 0.05 indicated statistical significance. Comparison with the NC group is denoted as #, with #P < 0.05, ##P < 0.01, and ###P < 0.001. Comparison with the MC group is denoted as *, with *P < 0.05, **P < 0.01, and ***P < 0.001.

Results

Effect of S. boulardii on body weight, faecal parameters, and small intestinal transit rate

The MC group exhibited lower body weight than the NC group (p < 0.05; Fig. 1B). A declining trend in body weight was observed in the SB and MN groups, whereas the BB group exhibited minimal growth. Loperamide decreased faecal weight (p < 0.05) and water content (p < 0.001) compared with those in the NC group (Fig. 1C, D), and the MN group displayed higher faecal weight (p < 0.05) and water content (p < 0.001) than the MC group. Bifidobacteria and S. boulardii did not significantly affect faecal weight or water content. Loperamide significantly prolonged the time of the first black stool in the MC group compared with that in the NC group (Fig. 1E). Conversely, bifidobacteria and metronidazole shortened the time of the first black stool compared with that in the MC group. After constipation induction, the small intestinal transit rate decreased in the MC group compared with that in the NC group (p < 0.001; Fig. 1F). However, the small intestinal transit rate in the BB group was higher than that in the MC group (p < 0.001).

Protein expression in the small intestinal tissue

In the MC group, the expression of inducible nitric oxide synthase (iNOS), p65, aquaporin 3 (AQP3), and IL-17 A increased significantly, whereas that of c-KIT, IL-10, myosin light chain kinase (MLCK), and phosphorylated myosin light chain 20 (P-MLC20) decreased compared with those in the NC group. Compared with those in the MC group, the levels of c-KIT, IL-10, MLCK, and P-MLC20 increased, and those of iNOS, p65, AQP3 and IL-17 A decreased in the BB and SB groups (p < 0.001; Fig. 2). No significant changes were observed in MLC20 expression.

Fig. 2.

Fig. 2

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The protein levels performed by western blotting. (A) protein expression level of c-kit; (B) protein expression level of AQP3; (C) protein expression level of iNOS; (D) protein expression level of NF-κB; (E) protein expression level of IL-10; (F) protein expression level of IL-17 A; (G) protein expression level of MLCK; (H) protein expression level of p-MLC20; (I) Western Blotting analysis. All data were expressed as mean ± SD (n = 6). ###P < 0.001, ##P < 0.01, #P < 0.05, MC vs NC. ***P < 0.001, **P < 0.01, *P < 0.05, BB, SB and MN vs MC

16 S rRNA sequencing

We performed 16 S rRNA sequencing to explore the diversity, richness, and composition of the intestinal microbial communities. The Sobs index of sample plateau in the rarefaction curve confirmed the validity of the results (Fig. 3A). Community diversity indices (Shannon, Sobs, Chao, and Ace) decreased in the MC group compared with those in the NC group, but the difference was not significant. Furthermore, S. boulardii did not significantly reverse these changes. Metronidazole aggravated the decrease in Ace, Chao, Shannon, and Sobs indices (p < 0.05, Fig. 3B-E). Overall, S. boulardii could not increase the α diversity of microbiota in the small intestine, whereas metronidazole reduced it. PCoA at the ASV level using the Abund–Jaccard method and non-metric multidimensional scaling (NMDS) using the binary Hamming method were performed, and the overall variations in microbial composition are shown in Fig. 3F-G. The PCoA yielded an R value of 0.6607, suggesting effective grouping. Non-metric multidimensional scaling indicated that the five groups were significantly clustered, with stress = 0.186 and R = 0.2643. These results suggest that the patterns of small intestine flora varied significantly among the groups, as evidenced by β-diversity trends, but the structural makeup of the groups was considerably similar (Fig. 3H-I).

Fig. 3.

Fig. 3

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S. boulardii alters the loperamide-induced gut microbial community structural and compositional shift. (A) The rarefaction curve of the Sobs index of each sample plateau. (B-E) Alpha diversity estimated by the ace, chao, shannon and sobs index. (F-G) Beta diversity estimated by PCoA (principal coordinate analysis) plot and NMDS (non-metric multidimensional scaling). (H-I) The microflora structural makeup of each group. H: family level; I: genus level. All data were expressed as mean ± SD (n = 6). *P < 0.05, **P < 0.01,***P < 0.001, BB, SB and MN vs MC

At the phylum level, the MC group showed a decrease in Verrucomicrobiota abundance but an increase in Patescibacteria abundance compared with the NC group. Saccharomyces boulardii treatment increased Firmicutes, Desulfobacterota, and Verrucomicrobiota abundance, but decreased Bacteroidota abundance compared to MC. Bifidobacteria treatment increased Verrucomicrobiota abundance compared with that in the MC group. Metronidazole treatment increased Verrucomicrobiota abundance but decreased Proteobacteria, Patescibacteria, and Cyanobacteria abundance compared with those in the MC group (Fig. 4A-C).

Fig. 4.

Fig. 4

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(A-F) Relative abundance of gut microbiota at different levels. (G) A heatmap of the top 50 microbial community members. (H) Linear discriminant analysis effect size (LEfSe) analyses (LDA score of > 4.0). All data were expressed as mean ± SD (n = 6). *P < 0.05, **P < 0.01,***P < 0.001

At the family level, loperamide significantly reduced Akkermansiaceae and Bifidobacteriaceae abundance but increased Saccharimonadaceae, Bacteroidaceae, Erysipelatoclostridiaceae, Atopobiaceae, norank_o_Rhodospirillales, and Peptostreptococcaceae abundance. Saccharomyces boulardii treatment significantly reduced Muribaculaceae, Bacteroidaceae, Erysipelatoclostridiaceae, Atopobiaceae, and Peptostreptococcaceae abundance but increased Desulfovibrionaceae, Bifidobacteriaceae, and Akkermansiaceae abundance in constipated mice. Furthermore, compared to the MC group, the BB group showed an increase in Bacillaceae, Akkermansiaceae, and unclassified_c_Bacilli abundance (p < 0.05) and a decrease in Sutterellaceae, Erysipelatoclostridiaceae, Bacteroidaceae, and Atopobiaceae abundance (p < 0.05, Fig. 4D-F). The top 50 microbial community members were used to construct a heatmap of the results of pattern comparisons (Fig. 4G).

The dominant microbiota in each group was determined using LEfSe. Different groups of bacteria with an LDA > 4 are presented in Fig. 4H. In the BB group, Bacillales Bacillaceae Bacillus, Dubosiella, Akkermansiaceae-Akkermansia, and Verrucomicrobiales-Verrucomicrobiae-Verrucomicrobiota were primarily detected. The abundance of Allobaculum, Desulfobacterota-Desulfovibrionaceae-Desulfovibrionales-Desulfovibrionia-Desulfovibrio, and Faecalibaculum increased in the SB group.

SCFA Concentration

The total SCFA and acetic acid concentrations were higher in the SB group than those in the MC group (p < 0.05; Fig. 5A-B).The valeric acid concentration in the small intestine significantly decreased after constipation induction (p < 0.001; Fig. 5C). Other SCFA showed no statistical significance among the groups.

Fig. 5.

Fig. 5

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The SCFA content of each group(µg/mg).(A) total SCFA content; (B) acetic acid content; (C) valeric acid content. All data were expressed as mean ± SD (n = 6). #P < 0.05, ##P < 0.01,###P < 0.001,MC vs. NC; *P < 0.05, **P < 0.01,***P < 0.001,BB, SB and MN vs. MC

Metabolite changes

Principal component analysis (PCA) was employed to analyse the metabolic profiles of small intestinal content samples. The PCA analysis of these samples showed a partial overlap of the confidence circles, indicating no distinct separation in the PCA score plot data among the groups. This finding suggested that the metabolites were similar regardless of the intervention, as depicted in Fig. 6A.

Fig. 6.

Fig. 6

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(A) PCA score plots based on the LC-MS/MS data of small intestine content samples from NC, MC and SB groups. (B) Heatmap analysis of the differential metabolites in five groups (top 30, n = 6) (row: biomarkers; column: groups. Color key indicates the contents of metabolites (blue: lowest; red: highest). (C-D) Volcano plots indicate up-regulated and down-regulated differential metabolites of MC vs NC group and SB vs MC group

Metabolite identification and comparison

Following filtering and denoising, 7,636 peaks (POS) and 6,513 peaks (NEG) were present. Primary and secondary MS datasets revealed 1,314 (POS) and 1,011 (NEG) compounds. The variable importance plot (VIP) value and P value were used to identify metabolic differences among the groups. The thresholds for significance were VIP ≥ 1 and P < 0.05. The majority of the temporal distribution of metabolites comprised up-regulated and down-regulated entities. After standardising all metabolite data, cluster analysis was carried out and a heatmap was generated (Fig. 6B). In the constipation model, the expression of 12 metabolites was significantly up-regulated and that of 5 was down-regulated in the MC group compared with those in the NC group. We also found 122 differentially expressed metabolites between the MC and SB groups, with three (fructose 6-phosphate, dihomo-alpha-linolenic acid, and 3-(4-hydroxyphenyl) lactate) being notably distinct among the NC, MC, and SB groups. The expression of these three metabolites was significantly down-regulated after constipation induction and up-regulated after S. boulardii treatment. They might be considered as biomarkers of constipation onset. We also speculate that they play a role in the course of S. boulardii treatment. However, their potential has not been proven in clinical practice. The expression of these metabolites was down-regulated after the modelling process but significantly recovered after S. boulardii administration. Collectively, the screened metabolites demonstrated the continuous influence of S. boulardii on the levels of small molecule metabolites in the mouse small intestine. Figure 6C-D depicts the differentially expressed metabolites using volcano maps.

Characterisation and functional analysis of key metabolic pathways

Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis was performed to assess metabolic pathways associated with constipation. Pathway enrichment bars indicated the metabolic pathways annotated in all samples (Fig. 7A), including lipid metabolism, amino acid metabolism, carbohydrate metabolism, metabolism of other amino acids, metabolism of cofactors and vitamins, digestive system, nervous system, cancer overview, and membrane transport. The number of metabolites annotated to a certain functional pathway demonstrated the dominance of this pathway. Differential metabolic pathways with significant effects were defined as rich factor > 0.1 and P < 0.05. We identified two differential metabolic pathways (biosynthesis of unsaturated fatty acids and African trypanosomiasis) including three metabolites between the NC and MC groups (Fig. 7B). There were 14 differential metabolic pathways between the MC and SB group such as aminoacyl-tRNA biosynthesis, central carbon metabolism in cancer, and protein digestion and absorption, which included 28 metabolites (Fig. 7C).

Fig. 7.

Fig. 7

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Characterization and functional analysis of key metabolic pathways. A: KEGG pathway annotation of all samples. Metabolic pathway enrichment profile of differential metabolites identified between the groups: B: between the NC and MC group; C: between the MC and SB group. The abscissa represents the name of the pathway, and the ordinate represents the enrichment ratio, which is the ratio of the number of compounds enriched in the pathway and the number of compounds annotated to the pathway. The redder the column color is, the more significant the enrichment of this pathway is. n = 6, * * * for P or FDR < 0.001, * * for P or FDR < 0.01, * for P or FDR < 0.05

Discussion

Constipation results in abdominal distension and appetite loss, which may contribute to the onset of other diseases. The delay in intestinal transit induced by loperamide results from a decrease in the defaecation frequency and an increase in intestinal contractions. Here, loperamide caused weight loss in mice, suggesting that constipation results in growth retardation and malnutrition. The constipated mice also showed a decrease in faecal weight, faecal water content, small intestinal transit rate, and SCFA levels in the small intestine, and associated intestinal dysbiosis. Bifidobacteria increased faecal weight and water content in constipated mice and markedly relieved constipation. However, S. boulardii did not markedly change these parameters. The mechanism underlying the regulation of small intestinal motility and microbiota by S. boulardii is complex.

Multiple factors might be involved in S. boulardii’s effect on intestinal motility. A previous study reported that S. boulardii supernatant up-regulated serotonin transporter (SERT) expression via epidermal growth factor receptor (EGFR) activation and modulated the intestinal microbiota, inhibiting colon motility in normal mice [13]. However, in our study, S. boulardii did not aggravate the constipation symptoms in loperamide-induced constipated mice. The differences of the results may attribute to the superposition effect of loperamide, which requires further controlled studies to prove. S. boulardii can secrete polyamines, enhance intestinal digestive enzyme activities, and up-regulate the expression of genes encoding nutrient transport system components [9]. S. boulardii reportedly regulated the microbiota-gut-brain axis in a humanised IBS mouse model [14]. S. boulardii treatment improved intestinal motility and ameliorated anxiety-like behaviour in mice with anxiety-associated IBS subjected to faecal microbiota transplantation [14]. S. boulardii effectively modulates the balance between pro- and anti-inflammatory cytokines in both blood and upper rectum tissues of patients with IBS [15]. Intestinal inflammation stimulates the intestinal mucosa, affects the stability of the intestinal barrier, and then negatively affects the intestinal movement. Coadministration of lactulose with S. boulardii significantly improved stool number and water content in constipated mice [16]. The GI transit ratio and total SCFA content were more effectively increased by S. boulardii than by lactulose alone [17]. Here, the level of IL-10 increased, whereas that of IL-17 A and NF-κB decreased in the SB group, suggesting that S. boulardii inhibited inflammatory reactions in the small intestine of constipated mice.

Constipation causes intestinal flora disorder and induces the colonisation of a variety of harmful bacteria. The abundance of Bacteroidetes in the colonic mucosal microbiota increases considerably in patients with constipation [18], whereas the abundance of Proteobacteria and butyrate-producing species, such as Roseburia and Streptococcus, decreases [19]. In a previous study, the abundance of Bacteroides spp. was lower in faecal samples from the functional constipation group than in those from healthy individuals [20]; this difference may be related to changes in intestinal motility and secretory function. Chronic constipation causes considerable changes in the relative abundance of some bacteria; however, the results are diverse in different populations, warranting further studies. Saccharomyces boulardii-administered mice reportedly showed decreased abundance of Firmicutes members, increased abundance of Bacteroidetes members, and decreased Firmicutes/Bacteroidetes (F/B) ratio compared to the controls [13]. Here, the abundance of Bacteroidaceae members in the small intestine was significantly higher in constipated mice than in the controls. Saccharomyces boulardii increased the abundance of Bifidobacteriaceae, Desulfovibrionaceae, and Akkermansiaceae members in the small intestine. Bifidobacteria produce SCFAs. The increased abundance of Bifidobacteria members increases the ratio of beneficial bacteria to harmful bacteria in the intestine and promotes the proliferation of beneficial bacteria, thus improving the intestinal flora. An increase in the abundance of Akkermansia species can prevent constipation development [21]. Faecalibacterium species are considered anti-inflammatory bacteria and Erysipelatoclostridium species are considered potentially harmful [22]. Regulating the proportion of these microorganisms in the intestine can improve intestinal function and mobility [23]. Here, S. boulardii increased the abundance of Akkermansia and Faecalibaculum members and reduced the abundance of Erysipelatoclostridiaceae members in the small intestine, improving the small intestinal microbial state of constipated mice.

SCFAs are products of fibre fermentation by the gut microbiota [24]. They stimulate the flow of colonic blood, fluids, and electrolytes, and mucosal proliferation. Furthermore, SCFAs participate in the regulation of intestinal transport [25]. S. boulardii helps maintain the intestinal integrity by synthesising SCFAs and protecting the intestine from damage [26]. Our results indicate that S. boulardii promotes SCFA secretion and increases the total SCFA and acetic acid concentrations. A previous study showed that infusion of butyrate into the colonic lumen partially restored intestinal peristaltic function in germ-free mice [27]. Another study found that the intestinal microbiota of healthy individuals was characterised by high abundance of the butyrate-producing bacterial genus Desulfovibrio, which alleviates the symptoms of constipation by promoting gut hormone secretion and maintaining intestinal barrier integrity [28]. This finding is in line with the results of our study, in which, the SB group demonstrated a higher abundance of butyrate-producing bacteria than the model group at the phylum and family levels. The study also confirmed that the SCFA levels may be important to the intestinal transit time. The mechanism underlying these phenomena may be related to the fact that SCFAs can stimulate colon transport through the luminal release of 5-HT [28].

ICCs are essential in the transmission of enteric nerve signals [29]. The fundamental mechanism underlying this process is the lack of ICCs lowers the postsynaptic response between ICCs and neurotransmitters, causing the loss of spontaneous rhythm-slowing waves in the ICCs, which in turn, affects intestinal mobility [30, 31]. c-KIT, a marker of ICCs, plays a critical role in ICC proliferation [32]. The ICC number decreases in the colon of patients with STC [33, 34]. The exact mechanisms underlying the function of ICCs remain unclear. Here, loperamide decreased the c-KIT level in the small intestine of mice, whereas S. boulardii and bifidobacteria effectively increased it, which in turn, increased the number of ICCs in the small intestine of constipated mice.

AQPs are mostly expressed in the colonic mucosal epithelial cells, and AQP3 is essential for water reabsorption by colonic surface cells [35]. Morphine causes constipation by increasing the AQP3 level in the intestine and promoting water absorption [36]. Here, S. boulardii decreased AQP3 expression in the small intestine of constipated mice. However, the exact mechanisms underlying the involvement of AQPs remain unclear.

In the MLCK pathway, calcium ions can activate MLCK after binding to calmodulin, and MLCK converts MLC20 to P-MLC20, thus enhancing myosin ATP enzyme activity, leading to smooth muscle contraction. MLC20 phosphorylation positively correlates with gastrointestinal motility and causes altered distribution and expression of TJ proteins and functional opening of the TJ barrier [37]. We found no evident changes in the MLC20 level in our study; however, the levels of MLCK and P-MLC20 decreased in the model group and increased in the SB group. Therefore, we speculate that the mechanism underlying the action of S. boulardii in constipated mice may involve the promotion of MLC20 phosphorylation and up-regulation of P-MLC20 expression in the tissue, and ultimately, the enhancement of smooth muscle contraction.

The NO level is abnormally elevated in the intestinal mucosa owing to constipation, resulting in decreased colonic excitability and motility. The serum and colonic mucosal NO levels considerably increase in patients with constipation [38]. Vascular endothelial cells normally produce NO from endothelial NOS (eNOS) and require a moderate amount of NO to maintain normal physiological functions [39]. Under normal conditions, iNOS is not expressed, but large amounts of iNOS are produced after intestinal damage, resulting in excess NO production. Here, loperamide induced inflammation in the small intestine. Bifidobacteria and S. boulardii attenuated inflammatory factor release by suppressing NF-κB and iNOS expression. Controlling NF-κB and iNOS levels can reduce the NO level and relieve constipation.

Metabolomic techniques are increasingly employed in the research of metabolic markers of diverse aetiologies. Here, untargeted metabolomic techniques were used to identify metabolites whose levels showed significant recovery after S. boulardii administration compared with those in constipated mice. The effects of S. boulardii on constipation were mainly related to alanine, aspartate, glutamate, and tryptophan metabolism. Specific amino acids (including glutamine, glutamate, arginine, glycine, lysine, threonine, and taurine) have potential therapeutic effects in intestinal-related diseases [40]. Studies have reported a close relationship between these amino acid levels and symptom improvement in patients with constipation; gastrointestinal endocrine dysfunction resulting from abnormal 5-HT levels is the cause of gastrointestinal problems. 5-HT synthesis requires tryptophan, and abnormalities in tryptophan metabolism may be linked to numerous intestinal disorders [41, 42]. Our metabolomic studies indicated that S. boulardii increases fructose 6-phosphate and 3-(4-hydroxyphenyl) lactate levels in the gastrointestinal tract of constipated mice. Fructose 6-phosphate, an intermediate in the glycolytic pathway, enables the internal conversion of carbohydrates, lipids, and amino acids through the tricarboxylic acid cycle. Caussy et al. identified an association between the gut microbiota and 3-(4-hydroxyphenyl) lactic acid, which is related to hepatic steatosis and fibrosis. They discovered that 3-(4-hydroxyphenyl) lactic acid is associated with the abundance of Firmicutes, Bacteroidetes, and Proteobacteria members [43]. This finding is consistent with our result, that is, S. boulardii regulates the alterations in the levels of associated metabolites. Our finding further supports the notion that S. boulardii promotes intestinal motility by regulating glycolysis and the citric acid cycle pathway.

In this study, we investigated the effects of S. boulardii on constipation using a mouse model. Notably, we found that it had minimal effect on constipation; however, we found that it considerably affected the microbiota and promoted anti-inflammatory factors. Therefore, this study can be used as a basis for future studies on the use of S. boulardii in the treatment of other intestinal conditions.

Acknowledgements

Not applicable.

Author contributions

ST and JW participated in the study conception and design. RZ supervised the research work. ST and JL performed the laboratory work and drafted the manuscript. YL, HD, WZ, ST did data analysis and data curation. JW and RZ critically reviewed the manuscript. ST revised the manuscript. All authors approved the final manuscript.All authors reviewed the manuscript.

Funding

None.

Data availability

Sequence data that support the findings of this study have been deposited in the NCBI Sequence Read Archive (SRA) repository with the primary accession code PRJNA1089828. https://www.ncbi.nlm.nih.gov/bioproject/PRJNA1089828.

Declarations

Ethics approval and consent to participate

All experimental protocols were approved by the Animal Ethics Committee of People’s Liberation Army General Hospital, Beijing, China (2022-X18-71).

Patient consent for publication

Not applicable.

Competing interests

The authors declare no competing interests.

Footnotes

Publisher’s note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Shuai Tang and Jia Li contributed equally to this work.

Contributor Information

Ru Zhang, Email: 5330248@163.com.

Jun Wan, Email: wanjun301@126.com.

References

  • 1.Hayeeawaema F, Wichienchot S, Khuituan P. Amelioration of gut dysbiosis and gastrointestinal motility by Konjac oligo-glucomannan on loperamide-induced constipation in mice. Nutrition. 2020;73:110715. [DOI] [PubMed] [Google Scholar]
  • 2.Huang J, Li S, Wang Q, Guan X, Qian L, Li J, Zheng Y, Lin B. Pediococcus pentosaceus B49 from human colostrum ameliorates constipation in mice. Food Funct. 2020;11(6):5607–20. [DOI] [PubMed] [Google Scholar]
  • 3.Zhao X, Yi R, Qian Y, Park KY. Lactobacillus plantarum YS-3 prevents activated Carbon-Induced Constipation in mice. J Med Food. 2018;21(6):575–84. [DOI] [PubMed] [Google Scholar]
  • 4.Zhang J, Chen B, Liu B, Zhou X, Mu J, Wang Q, Zhao X, Yang Z. Preventive effect of Lactobacillus fermentum CQPC03 on activated Carbon-Induced constipation in ICR mice. Med (Kaunas) 54(5) (2018). [DOI] [PMC free article] [PubMed]
  • 5.Horvath VJ, Vittal H, Lorincz A, Chen H, Almeida-Porada G, Redelman D, Ordog T. Reduced stem cell factor links smooth myopathy and loss of interstitial cells of cajal in murine diabetic gastroparesis. Gastroenterology. 2006;130(3):759–70. [DOI] [PubMed] [Google Scholar]
  • 6.Serra J, Pohl D, Azpiroz F, Chiarioni G, Ducrotte P, Gourcerol G, Hungin A, Layer P, Mendive JM, Pfeifer J, Rogler G, Scott SM, Simren M, Whorwell P. European society of neurogastroenterology and motility guidelines on functional constipation in adults. Neurogastroenterol Motil. 2020;32(2):e13762. [DOI] [PubMed] [Google Scholar]
  • 7.Czerucka D, Rampal P. Diversity of Saccharomyces Boulardii CNCM I-745 mechanisms of action against intestinal infections. World J Gastroenterol. 2019;25(18):2188–203. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 8.Buts JP, Dekeyser N, Stilmant C, Delem E, Smets F, Sokal E. Saccharomyces boulardii produces in rat small intestine a novel protein phosphatase that inhibits Escherichia coli endotoxin by dephosphorylation. Pediatr Res. 2006;60(1):24–9. [DOI] [PubMed] [Google Scholar]
  • 9.More MI, Vandenplas Y. Saccharomyces Boulardii CNCM i-745 improves intestinal enzyme function: a trophic effects review. Clin Med Insights Gastroenterol. 2018;11:420551577. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 10.Offei B, Vandecruys P, De Graeve S, Foulquie-Moreno MR, Thevelein JM. Unique genetic basis of the distinct antibiotic potency of high acetic acid production in the probiotic yeast Saccharomyces cerevisiae var. Boulardii Genome Res. 2019;29(9):1478–94. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 11.Brun P, Scarpa M, Marchiori C, Sarasin G, Caputi V, Porzionato A, Giron MC, Palu G, Castagliuolo I. Saccharomyces Boulardii CNCM I-745 supplementation reduces gastrointestinal dysfunction in an animal model of IBS. PLoS ONE. 2017;12(7):e181863. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 12.Ibanez L, Pontier-Bres R, Larbret F, Rekima A, Verhasselt V, Blin-Wakkach C, Czerucka D. Saccharomyces boulardii strain CNCM i-745 modifies the mononuclear phagocytes response in the small intestine of mice following salmonella typhimurium infection. Front Immunol. 2019;10:643. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 13.Gu Y, Wang C, Qin X, Zhou B, Liu X, Liu T, Xie R, Liu J, Wang B, Cao H. Saccharomyces Boulardii, a yeast probiotic, inhibits gut motility through upregulating intestinal serotonin transporter and modulating gut microbiota. Pharmacol Res. 2022;181:106291. [DOI] [PubMed] [Google Scholar]
  • 14.Constante M, De Palma G, Lu J, Jury J, Rondeau L, Caminero A, Collins SM, Verdu EF, Bercik P. Saccharomyces Boulardii CNCM I-745 modulates the microbiota-gut-brain axis in a humanized mouse model of irritable bowel syndrome. Neurogastroenterol Motil. 2021;33(3):e13985. [DOI] [PubMed] [Google Scholar]
  • 15.Abbas Z, Yakoob J, Jafri W, Ahmad Z, Azam Z, Usman MW, Shamim S, Islam M. Cytokine and clinical response to Saccharomyces boulardii therapy in diarrhea-dominant irritable bowel syndrome. Eur J Gastroen Hepat. 2014;26(6):630–9. [DOI] [PubMed] [Google Scholar]
  • 16.Park CW, Lee J, Hong YH, Kim YS, Suh HJ, Ahn Y. Coadministration of lactulose with probiotics ameliorates Loperamide-Induced constipation in mice. Prev Nutr Food Sci. 2023;28(4):427–35. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 17.Zhang X, Zheng J, Jiang N, Sun G, Bao X, Kong M, Cheng X, Lin A, Liu H. Modulation of gut microbiota and intestinal metabolites by lactulose improves loperamide-induced constipation in mice. Eur J Pharm Sci. 2021;158:105676. [DOI] [PubMed] [Google Scholar]
  • 18.Parthasarathy G, Chen J, Chen X, Chia N, O’Connor HM, Wolf PG, Gaskins HR, Bharucha AE. Relationship between microbiota of the colonic mucosa vs feces and symptoms, colonic transit, and methane production in female patients with chronic constipation. Gastroenterology. 2016;150(2):367–79. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 19.Li H, Chen J, Ren X, Yang C, Liu S, Bai X, Shan S, Dong X. Gut microbiota composition changes in constipated women of reproductive age. Front Cell Infect Microbiol. 2020;10:557515. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 20.Kim SE, Choi SC, Park KS, Park MI, Shin JE, Lee TH, Jung KW, Koo HS, Myung SJ. Change of fecal flora and effectiveness of the short-term VSL#3 probiotic treatment in patients with functional constipation. J Neurogastroenterol Motil. 2015;21(1):111–20. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 21.Kuda T, Yokota Y, Shikano A, Takei M, Takahashi H, Kimura B. Dietary and lifestyle disease indices and caecal microbiota in high fat diet, dietary fibre free diet, or DSS induced IBD models in ICR mice. J Funct Foods. 2017;35:605–14. [Google Scholar]
  • 22.Cao PQ, Li XP, Ou-Yang J, Jiang RG, Huang FF, Wen BB, Zhang XN, Huang JA, Liu ZH. The protective effects of yellow tea extract against loperamide-induced constipation in mice. Food Funct. 2021;12(12):5621–36. [DOI] [PubMed] [Google Scholar]
  • 23.Zhao Y, Yu YB. Intestinal microbiota and chronic constipation. Springerplus. 2016;5(1):1130. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 24.Wastyk HC, Fragiadakis GK, Perelman D, Dahan D, Merrill BD, Yu FB, Topf M, Gonzalez CG, Van Treuren W, Han S, Robinson JL, Elias JE, Sonnenburg ED, Gardner CD, Sonnenburg JL. Gut-microbiota-targeted diets modulate human immune status. Cell. 2021;184(16):4137–53. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 25.Martin CR, Osadchiy V, Kalani A, Mayer EA. The brain-gut-microbiome axis. Cell Mol Gastroenterol Hepatol. 2018;6(2):133–48. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 26.Pothoulakis C. Review article: anti-inflammatory mechanisms of action of Saccharomyces Boulardii. Aliment Pharmacol Ther. 2009;30(8):826–33. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 27.Vincent AD, Wang XY, Parsons SP, Khan WI, Huizinga JD. Abnormal absorptive colonic motor activity in germ-free mice is rectified by butyrate, an effect possibly mediated by mucosal serotonin. Am J Physiol Gastrointest Liver Physiol. 2018;315(5):G896–907. [DOI] [PubMed] [Google Scholar]
  • 28.Zhuang M, Shang W, Ma Q, Strappe P, Zhou Z. Abundance of probiotics and butyrate-production microbiome manages constipation via Short-Chain fatty acids production and hormones secretion. Mol Nutr Food Res. 2019;63(23):e1801187. [DOI] [PubMed] [Google Scholar]
  • 29.Yin J, Liang Y, Wang D, Yan Z, Yin H, Wu D, Su Q. Naringenin induces laxative effects by upregulating the expression levels of c-Kit and SCF, as well as those of aquaporin 3 in mice with loperamide-induced constipation. Int J Mol Med. 2018;41(2):649–58. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 30.Farrugia G. Interstitial cells of Cajal in health and disease. Neurogastroenterol Motil 20 Suppl 1 (2008) 54–63. [DOI] [PubMed]
  • 31.Xu J, Chen Y, Liu S, Hou X. Electroacupuncture regulates apoptosis/proliferation of intramuscular interstitial cells of cajal and restores colonic motility in diabetic constipation rats. Evid Based Complement Alternat Med. 2013;2013:584179. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 32.Brading AF, Mccloskey KD. Mechanisms of Disease: Specialized interstitial cells of the urinary tract—an assessment of current knowledge. Nat Clin Pract Urol. 2005;2(11):546–54. [DOI] [PubMed] [Google Scholar]
  • 33.Parthasarathy G, Chen J, Chia N, O’Connor HM, Gaskins HR, Bharucha AE. Reproducibility of assessing fecal microbiota in chronic constipation. Neurogastroenterol Motil. 2017;29(10):1–10. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 34.Mostafa RM, Moustafa YM, Hamdy H. Interstitial cells of Cajal, the Maestro in health and disease. World J Gastroenterol. 2010;16(26):3239–48. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 35.Silberstein C, Kierbel A, Amodeo G, Zotta E, Bigi F, Berkowski D, Ibarra C. Functional characterization and localization of AQP3 in the human colon. Braz J Med Biol Res. 1999;32(10):1303–13. [DOI] [PubMed] [Google Scholar]
  • 36.Kon R, Ikarashi N, Hayakawa A, Haga Y, Fueki A, Kusunoki Y, Tajima M, Ochiai W, Machida Y, Sugiyama K. Morphine-Induced constipation develops with increased aquaporin-3 expression in the colon via increased serotonin secretion. Toxicol Sci. 2015;145(2):337–47. [DOI] [PubMed] [Google Scholar]
  • 37.Gatica-Andrades M, Vagenas D, Kling J, Nguyen T, Benham H, Thomas R, Korner H, Venkatesh B, Cohen J, Blumenthal A. WNT ligands contribute to the immune response during septic shock and amplify endotoxemia-driven inflammation in mice. Blood Adv. 2017;1(16):1274–86. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 38.Que RS, Cao LP, Ding GP, Hu JA, Mao KJ, Wang GF. Correlation of nitric oxide and other free radicals with the severity of acute pancreatitis and complicated systemic inflammatory response syndrome. Pancreas. 2010;39(4):536–40. [DOI] [PubMed] [Google Scholar]
  • 39.Jin SW, Choi CY, Hwang YP, Kim HG, Kim SJ, Chung YC, Lee KJ, Jeong TC, Jeong HG. Betulinic acid increases eNOS phosphorylation and NO synthesis via the Calcium-Signaling pathway. J Agric Food Chem. 2016;64(4):785–91. [DOI] [PubMed] [Google Scholar]
  • 40.Shibuya N, Kimura H. Production of hydrogen sulfide from d-cysteine and its therapeutic potential. Front Endocrinol (Lausanne). 2013;4:87. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 41.Lamas B, Richard ML, Leducq V, Pham HP, Michel ML, Da CG, Bridonneau C, Jegou S, Hoffmann TW, Natividad JM, Brot L, Taleb S, Couturier-Maillard A, Nion-Larmurier I, Merabtene F, Seksik P, Bourrier A, Cosnes J, Ryffel B, Beaugerie L, Launay JM, Langella P, Xavier RJ, Sokol H. CARD9 impacts colitis by altering gut microbiota metabolism of tryptophan into aryl hydrocarbon receptor ligands. Nat Med. 2016;22(6):598–605. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 42.Agus A, Planchais J, Sokol H. Gut microbiota regulation of tryptophan metabolism in health and disease. Cell Host Microbe. 2018;23(6):716–24. [DOI] [PubMed] [Google Scholar]
  • 43.Caussy C, Hsu C, Lo MT, Liu A, Bettencourt R, Ajmera VH, Bassirian S, Hooker J, Sy E, Richards L, Schork N, Schnabl B, Brenner DA, Sirlin CB, Chen CH, Loomba R. Link between gut-microbiome derived metabolite and shared gene-effects with hepatic steatosis and fibrosis in NAFLD. Hepatology. 2018;68(3):918–32. [DOI] [PMC free article] [PubMed] [Google Scholar]

Associated Data

This section collects any data citations, data availability statements, or supplementary materials included in this article.

Data Availability Statement

Sequence data that support the findings of this study have been deposited in the NCBI Sequence Read Archive (SRA) repository with the primary accession code PRJNA1089828. https://www.ncbi.nlm.nih.gov/bioproject/PRJNA1089828.

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