Dynamics of the gut-liver axis in rats with varying fibrosis severity

The classic carbon tetrachloride (CCl₄)-induced liver injury model is widely used to study the pathogenesis of fibrosis and evaluate anti-fibrosis drugs. Here, we investigated the dynamic changes in the gut microbiota, bile acids (BAs) and the gut barrier over different fibrosis severities in a CCl₄-based model. 16S rDNA sequencing demonstrated that the beneficial taxon Lactobacillus was always underrepresented, and pathogens including Escherichia_Shigella, Clostridium_sensu_stricto_1, Colidextribacter, and Lachnospiraceae_UCG_010 were significantly overrepresented across liver fibrosis severities. Gut dysbiosis was more severe at the early stage of liver injury and advanced stage of fibrosis. An ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) analysis revealed that with the progress of fibrosis, unconjugated BAs in faeces were significantly decreased and conjugated BAs in serum were significantly increased. The FXR-SHP signalling pathway in the liver and ileum was statistically repressed in the fibrosis groups. Determination of lipopolysaccharide (LPS) and fluorescein isothiocyanate (FITC)-dextran levels in plasma showed that the intestinal barrier remained relatively intact in the advanced fibrosis stage. The advances in knowledge of the gut-liver axis provided by this study yield new insights for application in research and drug evaluation.     

Amelioration of hyperglycaemia and hyperlipidaemia by adjusting the interplay between gut microbiota and bile acid metabolism: Radix Scutellariae as a case

BackgroundOur previous clinical research showed that the interaction between gut microbiota and bile acids (BAs) in patients with type 2 diabetes mellitus (T2DM) changed significantly. We hypothesized that T2DM could be improved by adjusting this interaction mediated by farnesoid X receptor (FXR). T2DM belongs to the category of “xiaoke” in traditional Chinese medicine. Radix scutellariae has the effects of clearing away heat and eliminating dampness, curing jaundice and quenching thirst and is widely used alone or in combination with other medicines for the treatment of T2DM in China and throughout Asia. Additionally, the interaction between Radix scutellariae and gut microbiota may influence its efficacy in the treatment of T2DM.PurposeThis study chose Radix scutellariae to validate that T2DM could improve by adjusting the interaction between gut microbiota and bile acid metabolism.Study design and methodsRadix scutellariae water extract (WESB) was administered to a T2DM rat model established by a high-fat diet combined with streptozotocin. The body weight and blood glucose and insulin levels were measured. The levels of serum lipids, creatinine, uric acid, albumin and total bile acid were also detected. Changes in the pathology and histology of the pancreas, liver and kidney were observed by haematoxylin-eosin staining. The 16S rRNAs of gut microbiota were sequenced, and the faecal and serum BAs were determined by liquid chromatography tandem mass spectrometry. The expression levels of BA metabolism-associated proteins in the liver and intestine were evaluated by immunoblot analysis.ResultsThe results showed that WESB improved hyperglycaemia, hyperlipaemia, and liver and kidney damage in T2DM rats. In addition, the abundances of key gut microbiota and the concentrations of certain secondary BAs in faeces and serum were restored. Moreover, there was a significant correlation between the restored gut microbiota and BAs, which might be related to the activation of liver cholesterol 7α-hydroxylase (CYP7A1) and the inhibition of FXR expression in the intestine rather than the liver.ConclusionsThis study provided new ideas for the prevention or treatment of clinical diabetes and its complications by adjusting the interaction between gut microbiota and bile acid metabolism.     

Bile acid is a significant host factor shaping the gut microbiome of diet-induced obese mice

Background

Intestinal bacteria are known to regulate bile acid (BA) homeostasis via intestinal biotransformation of BAs and stimulation of the expression of fibroblast growth factor 19 through intestinal nuclear farnesoid X receptor (FXR). On the other hand, BAs directly regulate the gut microbiota with their strong antimicrobial activities. It remains unclear, however, how mammalian BAs cross-talk with gut microbiome and shape microbial composition in a dynamic and interactive way.

Results

We quantitatively profiled small molecule metabolites derived from host-microbial co-metabolism in mice, demonstrating that BAs were the most significant factor correlated with microbial alterations among all types of endogenous metabolites. A high-fat diet (HFD) intervention resulted in a rapid and significant increase in the intestinal BA pool within 12 h, followed by an alteration in microbial composition at 24 h, providing supporting evidence that BAs are major dietary factors regulating gut microbiota. Feeding mice with BAs along with a normal diet induced an obese phenotype and obesity-associated gut microbial composition, similar to HFD-fed mice. Inhibition of hepatic BA biosynthesis under HFD conditions attenuated the HFD-induced gut microbiome alterations. Both inhibition of BAs and direct suppression of microbiota improved obese phenotypes.

Conclusions

Our study highlights a liver–BA–gut microbiome metabolic axis that drives significant modifications of BA and microbiota compositions capable of triggering metabolic disorders, suggesting new therapeutic strategies targeting BA metabolism for metabolic diseases.

     

Impact of Primary and Secondary Bile Acids on Clostridioides Difficile Infection

Primary bile acids (BAs), synthesized from cholesterol in the liver, after their secretion with bile into the intestinal lumen, are transformed by gut microbiota to secondary BAs. As natural detergents, BAs play a key role in the digestion and absorption of lipids and liposoluble vitamins. However, they have also been recognized as important signaling molecules involved in numerous metabolic processes. The close bidirectional interactions between BAs and gut microbiota occur since BAs influence microbiota composition, whereas microbiota determines BA metabolism. In particular, it is well established that BAs modulate Clostridioides difficile life cycle in vivo. C. difficile is a cause of common nosocomial infections that have become a growing concern. The aim of this review is to summarize the current knowledge regarding the impact of BAs on the pathogenesis, prevention, and treatment of C. difficile infection. Open in a separate window     

Turnover of bile acids in liver,serum and caecal content by high-fat diet feeding affects hepatic steatosis in rats

BackgroundBile acids (BAs) participate in lipid absorption and serve as metabolic regulatory factors in gut-liver communication. To date, there are no studies on the systemic patterns of BAs in the serum, liver, and gut in the same non-alcoholic fatty liver disease (NAFLD) model.MethodsA targeted metabolomics approach and 16S rRNA sequencing were used to identify the profile of BAs and connection between BAs and microbiota. The role and mechanism of altered BAs on hepatic steatosis were investigated.FindingsIn the liver, the composition of taurocholic acid (TCA) was increased, but taurohyodeoxycholic acid (THDCA) and ursodeoxycholic acid (UDCA) were decreased. In the gut, the deconjugated form of TCA (cholic acid (CA)) was increased, while the deconjugated forms of THDCA (α-hyodeoxycholic acid (HDCA)) and ω-muricholic acid (ωMCA) were decreased. In the serum, the composition of TCA was increased, while both HDCA and THDCA were decreased. THDCA induced the gene expression of apolipoprotein, bile secretion-related proteins, and cytochrome P450 family but suppressed inflammatory response genes expression in steatotic hepatocytes by RNAseq analysis. THDCA ameliorated neutral lipid accumulation and improved insulin sensitivity in primary rat hepatocytes. The decreased HDCA level correlated with the level of Bacteroidetes, while the level of CA correlated with the levels of Firmicutes and Verrucomicrobia but correlated inversely with Bacteroidetes.ConclusionBAs profiles in the serum, liver and caecal content were altered in a rat NAFLD model, which may affect hepatic lipid accumulation and correlate with gut dysbiosis.     

Polydatin alleviates bleomycin-induced pulmonary fibrosis and alters the gut microbiota in a mouse model

To investigate the effect and mechanism of polydatin on bleomycin (BLM)-induced pulmonary fibrosis in a mouse model. The lung fibrosis model was induced by BLM. The contents of TNF-α, LPS, IL-6 and IL-1β in lung tissue, intestine and serum were detected by ELISA. Gut microbiota diversity was detected by 16S rDNA sequencing; R language was used to analyse species composition, α-diversity, β-diversity, species differences and marker species. Mice were fed drinking water mixed with four antibiotics (ampicillin, neomycin, metronidazole, vancomycin; antibiotics, ABx) to build a mouse model of ABx-induced bacterial depletion; and faecal microbiota from different groups were transplanted into BLM-treated or untreated ABx mice. The histopathological changes and collagen I and α-SMA expression were determined. Polydatin effectively reduced the degree of fibrosis in a BLM-induced pulmonary fibrosis mouse model; BLM and/or polydatin affected the abundance of the dominant gut microbiota in mice. Moreover, faecal microbiota transplantation (FMT) from polydatin-treated BLM mice effectively alleviated lung fibrosis in BLM-treated ABx mice compared with FMT from BLM mice. Polydatin can reduce fibrosis and inflammation in a BLM-induced mouse pulmonary fibrosis model. The alteration of gut microbiota by polydatin may be involved in the therapeutic effect.     

Antibiotic pretreatment attenuates liver ischemia–reperfusion injury by Farnesoid X receptor activation

Prophylactic antibiotics (Abx) are used before liver surgery, and the influence of antibiotic pretreatment on hepatic ischemia–reperfusion injury (IRI) remains unclear. Hence, we explored the impact of Abx pretreatment on hepatic IRI in the present work. The gut microbiota has an essential role in hepatic bile acid (BA) metabolism, and we assumed that depletion of the gut microbiota could affect the composition of hepatic BAs and affect liver IRI. The IRI model demonstrated that Abx pretreatment attenuated liver IRI by alleviating cell apoptosis, reducing the inflammatory response, and decreasing the recruitment of CCR2+ monocytes. Mechanistically, Abx pretreatment reshaped the gut microbiota, especially decreasing the relative abundance of Firmicutes and increasing the relative abundance of Clostridium, which were related to the transformation of BAs and were consistent with the altered bile acid species (unconjugated BAs, especially UDCA). These altered BAs are known FXR agonists and lead to the activation of the farnesoid X receptor (FXR), which can directly bind to the FXR response element (FXRE) harbored in the TLR4 promoter and further suppress downstream mitogen-activated protein kinase (MAPK) and nuclear kappa B (NF-κB) pathways. Meanwhile, the CCL2–CCR2 axis was also involved in the process of FXR activation, as we confirmed both in vivo and in vitro. Importantly, we proved the importance of FXR in mice and clinical occlusion samples, which were inversely correlated with liver injury. Taken together, our study identified that Abx pretreatment before liver resection was a beneficial event by activating FXR, which might become a potential therapeutic target in treating liver injury.Subject terms: Biochemistry, Molecular biology     

The clinical and mechanistic roles of bile acids in depression,Alzheimer's disease,and stroke

The burden of neurological and neuropsychiatric disorders continues to grow with significant impacts on human health and social economy worldwide. Increasing clinical and preclinical evidences have implicated that bile acids (BAs) are involved in the onset and progression of neurological and neuropsychiatric diseases. Here, we summarized recent studies of BAs in three types of highly prevalent brain disorders, depression, Alzheimer's disease, and stroke. The shared and specific BA profiles were explored and potential markers associated with disease development and progression were summarized. The mechanistic roles of BAs were reviewed with focuses on inflammation, gut–brain–microbiota axis, cellular apoptosis. We also discussed future perspectives for the prevention and treatment of neurological and neuropsychiatric disorders by targeting BAs and related molecules and gut microbiota. Our understanding of BAs and their roles in brain disorders is still evolving. A large number of questions still need to be addressed on the emerging crosstalk among central, peripheral, intestine, and their contribution to brain and mental health.     

胆汁酸功能及其与肠道细菌相互关系

胆汁酸具有多种重要生理功能. 近年研究发现,胆汁酸可作为信号分子与褐色脂肪细胞表面受体TGR5结合,可激活法尼酯衍生物X受体（nuclear receptor farnesoid X receptor, FXR）的表达. 通过激活这些不同的信号传导途径,胆汁酸可以分别起到调节体内能量代谢平衡、控制肥胖以及抑制肠道细菌过度增殖的作用. 胆汁酸与人及动物肠道细菌具有复杂的相互关系：肠道细菌对于胆汁酸的转化很重要,除了在胆汁酸的转化中发挥重要作用外,肠道微生物菌群还可以十分有效地水解已被胆汁酸清除的生物体内结合寄生物或异源物质,促进这些物质的活化或肠肝循环. 宿主拥有一些抑制细菌过度增殖的机制,这些机制包括快速转运以及利用抗菌肽、蛋白水解肽和胆汁酸等进行抑菌;而有些肠道细菌在进化中形成一些抗性机制可避免胆汁酸胁迫. 本文主要就胆汁酸控制肥胖以及抑制细菌过度增殖的机制和胆汁酸与肠道细菌相互关系进行了综述.     

Prevotella copri ameliorates cholestasis and liver fibrosis in primary sclerosing cholangitis by enhancing the FXR signalling pathway

Primary sclerosing cholangitis (PSC) is a chronic cholestatic liver disease characterized by bile duct inflammation, fibrosis, bile acid (BA) metabolism disorders and gut microbiota dysbiosis. At present, the aetiology and pathogenesis of PSC are not clear, and there is no specific or effective treatment available. Therefore, new research perspectives are needed to explore effective methods to treat PSC and improve symptoms. The intestinal microbiota of patients with PSC is known to be significantly different from that of healthy people. By comparing differentially abundant bacterial genera in PSC patients, it was found that the abundance of Prevotella copri (P. copri) was significantly decreased, suggesting that this species may have a protective effect against PSC disease. Therefore, comprehensively exploring the role and possible function of P. copri in the disease process is worthwhile. In this study, a PSC mouse model was established by feeding mice a customized diet supplemented with 0.1% (w/w) 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC) for one week, and the abundance of P. copri was confirmed to be decreased in this model. Previous studies in patients and animal models have demonstrated that gut microbiota intervention is an acceptable treatment for some diseases. We found that intervention with P. copri could significantly improve cholestasis and liver fibrosis by enhancing the FXR-related signalling pathway in PSC mice. Together, through the overall effect of P. copri on intestinal microbiota structure and its association with BAs, we speculate that P. copri intervention might be as potential biological treatment of PSC.     

慢性乙型肝炎患者肠道菌群与肝脏生化指标的相关性

乙型肝炎病毒感染引起的慢性乙型肝炎(Chronic hepatitis B,CHB)是一种全球性流行疾病,严重时可引起肝功能衰竭,甚至发展成肝硬化和肝癌.也已发现CHB的发生和发展与肠道菌群的组成和结构的变化密切相关.为进一步探究肠道菌群结构与肝脏生化指标之间的联系,文中随机纳入14名CHB患者和11名健康对照者(Co...     

Traditional Chinese Medicine Ganshuang Granules Attenuate CCl4-Induced Hepatic Fibrosis by Modulating Gut Microbiota

Gut dysbiosis contributes to hepatic fibrosis. Emerging evidence revealed the major role of traditional Chinese medicine (TCM) in gut microbiota homeostasis. Here, we aimed to investigate the anti-fibrotic activity and underlying mechanism of ganshuang granules (GS), particularly regarding gut microbiota homeostasis. CCl₄-induced hepatic fibrosis models were allocated into 4 groups receiving normal saline (model), 1.0, 2.0, or 4.0 g/kg GS for 5 weeks. As result, GS treatment alleviated liver injury in CCl₄-induced hepatic fibrosis, presenting as decreases of the liver index, alanine aminotransferase, and aspartate transaminase. Histological staining and expression revealed that the enhanced oxidative stress, inflammatory and hepatic fibrosis in CCl₄-induced models were attenuated by GS. Immunohistochemical staining showed that tight junction-associated proteins in intestinal mucosa were up-regulated by GS. 16S rRNA sequencing showed that GS rebalanced the gut dysbiosis manifested as improving alpha and beta diversity of gut microbiota, reducing the ratio of Firmicutes to Bacteroidetes, and regulating the relative abundance of various bacteria. In summary, GS decreased the intestinal permeability and rebalanced the gut microbiota to reduce the oxidative stress and inflammation, eventually attenuating CCl₄-induced hepatic fibrosis.     

Targeting the alternative bile acid synthetic pathway for metabolic diseases

The gut microbiota is profoundly involved in glucose and lipid metabolism,in part by regulating bile acid(BA)metabolism and affecting multiple BA-receptor signaling pathways.BAs are synthesized in the liver by multi-step reactions catalyzed via two distinct routes,the classical pathway(producing the 12α-hy-droxylated primary BA,cholic acid),and the alternative pathway(producing the non-12α-hydroxylated primary BA,chenodeoxycholic acid).BA synthesis and excre-tion is a major pathway of cholesterol and lipid cata-bolism,and thus,is implicated in a variety of metabolic diseases including obesity,insulin resis-tance,and nonalcoholic fatty liver disease.Addition-ally,both oxysterols and BAs function as signaling molecules that activate multiple nuclear and mem-brane receptor-mediated signaling pathways in various tissues,regulating glucose,lipid homeostasis,inflam-mation,and energy expenditure.Modulating BA syn-thesis and composition to regulate BA signaling is an interesting and novel direction for developing thera-pies for metabolic disease.In this review,we sum-marize the most recent findings on the role of BA synthetic pathways,with a focus on the role of the alternative pathway,which has been under-investi-gated,in treating hyperglycemia and fatty liver dis-ease.We also discuss future perspectives to develop promising pharmacological strategies targeting the alternative BA synthetic pathway for the treatment of metabolic diseases.     

High‐fat diet‐induced dysbiosis mediates MCP‐1/CCR2 axis‐dependent M2 macrophage polarization and promotes intestinal adenoma‐adenocarcinoma sequence

High‐fat diet (HFD) is a well‐known risk factor for gut microbiota dysbiosis and colorectal cancer (CRC). However, evidence relating HFD, gut microbiota and carcinogenesis is limited. Our study aimed to demonstrate that HFD‐induced gut dysbiosis promoted intestinal adenoma‐adenocarcinoma sequence. In clinical study, we found that HFD increased the incidence of advanced colorectal neoplasia (AN). The expression of monocyte chemoattractant protein 1 (MCP‐1), CC chemokine receptor 2 (CCR2) and CD163 in CRC patients with HFD was significantly higher than that in CRC patients with normal diet. When it comes to the Apc^min/+ mice, HFD consumption could induce gut dysbiosis and promote intestinal carcinogenesis, accompanying with activation of MCP‐1/CCR2 axis that recruited and polarized M2 tumour‐associated macrophages. Interestingly, transfer of faecal microbiota from HFD‐fed mice to another batch of Apc^min/+ mice in the absence of HFD could also enhance carcinogenesis without significant body weight gain and induced MCP‐1/CCR2 axis activation. HFD‐induced dysbiosis could also be transmitted. Meanwhile, antibiotics cocktail treatment was sufficient to inhibit HFD‐induced carcinogenesis, indicating the vital role of dysbiosis in cancer development. Conclusively, these data indicated that HFD‐induced dysbiosis accelerated intestinal adenoma‐adenocarcinoma sequence through activation of MCP‐1/CCR2 axis, which would provide new insight into better understanding of the mechanisms and prevention for HFD‐related CRC.     

Gut microbiota–bile acid–skeletal muscle axis

The gut microbiota represents a ‘metabolic organ’ that can regulate human metabolism. Intact gut microbiota contributes to host homeostasis, whereas compositional perturbations, termed dysbiosis, are associated with a wide range of diseases. Recent evidence demonstrates that dysbiosis, and the accompanying loss of microbiota-derived metabolites, results in a substantial alteration of skeletal muscle metabolism. As an example, bile acids, produced in the liver and further metabolized by intestinal microbiota, are of considerable interest since they regulate several host metabolic pathways by activating nuclear receptors, including the farnesoid X receptor (FXR). Indeed, alteration of gut microbiota may lead to skeletal muscle atrophy via a bile acid–FXR pathway. This Review aims to suggest a new pathway that connects different mechanisms, involving the gut–muscle axis, that are often seen as unrelated, and, starting from preclinical studies, we hypothesize new strategies aimed at optimizing skeletal muscle functionality.     

Effects of barley variety,dietary fiber and β-glucan content on bile acid composition in cecum of rats fed low- and high-fat diets

Diet-induced obesity and insulin resistance have been linked to changes in bile acid (BA) profiles, which in turn are highly dependent on the dietary composition and activity of the gut microbiota. The objective of the present study was to investigate whether the type and level of fiber had an effect on cecal BA composition when included in low- and high-fat diets. Groups of rats were fed two barley varieties, which resulted in three test diets containing three levels of β-glucans and two levels of dietary fiber. BAs were preconcentrated using hollow fiber liquid-phase microextraction and quantified by gas chromatography. The amount of the secondary BAs, lithocholic-, deoxycholic- and hyodexycholic acids was generally higher in groups fed high-fat diets compared with corresponding acids in groups fed low-fat diets (P<.05). In contrast, most of the primary and the secondary BAs, ursodeoxycholic acid and β- and ω-muricholic acids, were two to five times higher (P<.05) in groups fed low-fat diets than in groups fed high-fat diets. This was particularly true for groups fed the highest level of β-glucans and in some cases also the medium level. The BA profile in the gut was strongly dependent on the amount and type of dietary fiber in the diet, which may be useful in the prevention/treatment of diseases associated with changes in BA profiles.     

Alterations in gut microbiota and metabolites associated with altitude-induced cardiac hypertrophy in rats during hypobaric hypoxia challenge

The gut microbiota is involved in host responses to high altitude. However, the dynamics of intestinal microecology and their association with altitude-related illness are poorly understood. Here, we used a rat model of hypobaric hypoxia challenge to mimic plateau exposure and monitored the gut microbiome, short-chain fatty acids (SCFAs), and bile acids (BAs) over 28 d. We identified weight loss, polycythemia, and pathological cardiac hypertrophy in hypoxic rats, accompanied by a large compositional shift in the gut microbiota, which is mainly driven by the bacterial families of Prevotellaceae, Porphyromonadaceae, and Streptococcaceae. The aberrant gut microbiota was characterized by increased abundance of the Parabacteroides, Alistipes, and Lactococcus genera and a larger Bacteroides to Prevotella ratio. Trans-omics analyses showed that the gut microbiome was significantly correlated with the metabolic abnormalities of SCFAs and BAs in feces, suggesting an interaction network remodeling of the microbiome-metabolome after the hypobaric hypoxia challenge. Interestingly, the transplantation of fecal microbiota significantly increased the diversity of the gut microbiota, partially inhibited the increased abundance of the Bacteroides and Alistipes genera, restored the decrease of plasma propionate, and moderately ameliorated cardiac hypertrophy in hypoxic rats. Our results provide an insight into the longitudinal changes in intestinal microecology during the hypobaric hypoxia challenge. Abnormalities in the gut microbiota and microbial metabolites contribute to the development of high-altitude heart disease in rats.

     

Fluorofenidone ameliorates cholestasis and fibrosis by inhibiting hepatic Erk/-Egr-1 signaling and Tgfβ1/Smad pathway in mice

Cholestasis is characterized by intrahepatic accumulation of bile acids (BAs), resulting in liver injury, fibrosis, and liver failure. To date, only ursodeoxycholic acid and obeticholic acid have been approved for the treatment of cholestasis. As fluorofenidone (AKF-PD) was previously reported to play significant anti-fibrotic and anti-inflammatory roles in various diseases, we investigated whether AKF-PD ameliorates cholestasis. A mouse model of cholestasis was constructed by administering a 0.1 % 3,5-diethoxycarbonyl-1,4-dihydroxychollidine (DDC) diet for 14 days. Male C57BL/6 J mice were treated with either AKF-PD or pirfenidone (PD) orally in addition to the DDC diet. Serum and liver tissues were subsequently collected and analyzed. We found that AKF-PD significantly reduced the levels of serum alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP) and total bile salts (TBA), as well as hepatic bile acids (BAs) levels. Hepatic histological analyses demonstrated that AKF-PD markedly attenuated hepatic inflammation and fibrosis. Further mechanistic analyses revealed that AKF-PD markedly inhibited expression of Cyp7a1, an enzyme key to BAs synthesis, by increasing Fxr nuclear translocation, and decreased hepatic inflammation by attenuating Erk/-Egr-1-mediated expression of inflammatory cytokines and chemokines Tnfα, Il-1β, Il-6, Ccl2, Ccl5 and Cxcl10. Moreover, AKF-PD was found to substantially reduce liver fibrosis via inhibition of Tgfβ1/Smad pathway in our mouse model. Here, we found that AKF-PD effectively attenuates cholestasis and hepatic fibrosis in the mouse model of DDC-induced cholestasis. As such, AKF-PD warrants further investigation as a candidate drug for treatment of cholestasis.     

Systemic multicompartmental effects of the gut microbiome on mouse metabolic phenotypes

To characterize the impact of gut microbiota on host metabolism, we investigated the multicompartmental metabolic profiles of a conventional mouse strain (C3H/HeJ) (n=5) and its germ‐free (GF) equivalent (n=5). We confirm that the microbiome strongly impacts on the metabolism of bile acids through the enterohepatic cycle and gut metabolism (higher levels of phosphocholine and glycine in GF liver and marked higher levels of bile acids in three gut compartments). Furthermore we demonstrate that (1) well‐defined metabolic differences exist in all examined compartments between the metabotypes of GF and conventional mice: bacterial co‐metabolic products such as hippurate (urine) and 5‐aminovalerate (colon epithelium) were found at reduced concentrations, whereas raffinose was only detected in GF colonic profiles. (2) The microbiome also influences kidney homeostasis with elevated levels of key cell volume regulators (betaine, choline, myo‐inositol and so on) observed in GF kidneys. (3) Gut microbiota modulate metabotype expression at both local (gut) and global (biofluids, kidney, liver) system levels and hence influence the responses to a variety of dietary modulation and drug exposures relevant to personalized health‐care investigations.     

Removal of adult cyathostomins alters faecal microbiota and promotes an inflammatory phenotype in horses

The interactions between parasitic helminths and gut microbiota are considered to be an important, although as yet incompletely understood, factor in the regulation of immunity, inflammation and a range of diseases. Infection with intestinal helminths is ubiquitous in grazing horses, with cyathostomins (about 50 species of which are recorded) predominating. Consequences of infection include both chronic effects, and an acute inflammatory syndrome, acute larval cyathostominosis, which sometimes follows removal of adult helminths by administration of anthelmintic drugs. The presence of cyathostomins as a resident helminth population of the equine gut (the “helminthome”) provides an opportunity to investigate the effect helminth infection, and its perturbation, has on both the immune system and bacterial microbiome of the gut, as well as to determine the specific mechanisms of pathophysiology involved in equine acute larval cyathostominosis. We studied changes in the faecal microbiota of two groups of horses following treatment with anthelmintics (fenbendazole or moxidectin). We found decreases in both alpha diversity and beta diversity of the faecal microbiota at Day 7 post-treatment, which were reversed by Day 14. These changes were accompanied by increases in inflammatory biomarkers. The general pattern of faecal microbiota detected was similar to that seen in the relatively few equine gut microbiome studies reported to date. We conclude that interplay between resident cyathostomin populations and the bacterial microbiota of the equine large intestine is important in maintaining homeostasis and that disturbance of this ecology can lead to gut dysbiosis and play a role in the aetiology of inflammatory conditions in the horse, including acute larval cyathostominosis.