Remote Sensing between Liver and Intestine: Importance of Microbial Metabolites

Maternal PBDE exposure disrupts gut microbiome and promotes hepatic proinflammatory signaling in humanized PXR-transgenic mouse offspring over time

Developmental exposure to the persistent environmental pollutant, polybrominated diphenyl ethers (PBDEs), is associated with increased diabetes prevalence. The microbial tryptophan metabolite, indole-3-propionic acid (IPA), is associated with reduced risk of type 2 diabetes and lower-grade inflammation and is a pregnane X receptor (PXR) activator. To explore the role of IPA in modifying the PBDE developmental toxicity, we orally exposed humanized PXR-transgenic (hPXR-TG) mouse dams to vehicle, 0.1 mg/kg/day DE-71 (an industrial PBDE mixture), DE-71+IPA (20 mg/kg/day), or IPA, from 4 weeks preconception to the end of lactation. Pups were weaned at 21 days of age and IPA supplementation continued in the corresponding treatment groups. Tissues were collected at various ages until 6 months of age (n = 5 per group). In general, the effect of maternal DE-71 exposure on the gut microbiome of pups was amplified over time. The regulation of hepatic cytokines and prototypical xenobiotic-sensing transcription factor target genes by DE-71 and IPA was age- and sex-dependent, where DE-71-mediated mRNA increased selected cytokines (Il10, Il12p40, Il1β [both sexes], and [males]). The hepatic mRNA of the aryl hydrocarbon receptor (AhR) target gene Cyp1a2 was increased by maternal DE-71 and DE-71+IPA exposure at postnatal day 21 but intestinal Cyp1a1 was not altered by any of the exposures and ages. Maternal DE-71 exposure persistently increased serum indole, a known AhR ligand, in age- and sex-dependent manner. In conclusion, maternal DE-71 exposure produced a proinflammatory signature along the gut-liver axis, including gut dysbiosis, dysregulated tryptophan microbial metabolism, attenuated PXR signaling, and elevated AhR signaling in postweaned hPXR-TG pups over time, which was partially corrected by IPA supplementation.

Relevance of Bile Acids in Cholangiocarcinoma Pathogenesis: Critical Revision and Future Directions

Cholangiocarcinoma (CCA), a highly heterogeneous cancer, is the second most common type of primary liver cancer. It is characterized by resistance to therapy and poor prognosis, with a 5-year survival rate lower than 20%. The pathogenesis of CCA is complex and multifactorial, and in recent years, bile acids (BAs) have been implicated in CCA development and prognosis. BAs belong to a category of amphipathic compounds that hold significant importance as signaling molecules and inflammatory agents. They possess the ability to activate transcriptional factors and cellular signaling pathways, thereby governing the regulation of lipid, glucose, and energy metabolism in diverse human disorders. These disorders encompass chronic liver diseases among other conditions. In this review, we provided an update on the current knowledge on the molecular mechanisms involving BAs in cholangiocarcinogenesis. Additionally, we analyzed the role of gut and biliary microbiota in CCA pathogenesis. Future research is required to better understand how to modulate BA activity and, possibly, identify new therapeutic strategies.

Antihypertensive Activity of Milk Fermented by Lactiplantibacillus plantarum SR37-3 and SR61-2 in L-NAME-Induced Hypertensive Rats

Probiotic fermented milk can lower the incidence rate of hypertension and is beneficial to the regulation of the intestinal microecology. However, the underlying molecular mechanism remains elusive. Here, we evaluated the role of the gut microbiota and its metabolites in the antihypertensive effect of milk fermented by the Lactiplantibacillus plantarum strains SR37-3 (PFM-SR37-3) and SR61-2 (PFM-SR61-2) in Ng-nitro-L-arginine methyl ester induced hypertensive rats. The results showed that PFM-SR37-3 and PFM-SR61-2 intervention significantly lowered the blood pressure (BP) of NG-nitro-L-arginine methyl ester induced hypertensive rats and attenuated renal injury. In particular, long-term administration of PFM inhibited a progressive elevation in SBP (170.22 ± 8.40 and 133.28 ± 6.09 by model group and PFM-SR37-3 treated model group, respectively, at the end of the 4 weeks; p < 0.01 PFM-SR37-3 treated model group versus model group) and DBP (133.83 ± 5.91 and 103.00 ± 6.41 by model group and PFM-SR37-3 treated model group, respectively, at the end of the 4 weeks; p < 0.01 PFM-SR37-3 treated model group versus model group). PFM-SR37-3 and PFM-SR61-2 reshaped the gut microbiome and metabolome, and especially regulated the metabolic levels of L-phenylalanine, L-methionine and L-valine in the intestine and blood circulation. The analysis of the target organ’s aortic transcriptome indicated that the protective effects of PFM-SR37-3 and PFM-SR61-2 were accompanied by the modulation of the BP circadian rhythm pathway, which was conducive to cardiovascular function. Vascular transcriptomic analysis showed that circadian rhythm and AMPK might be potential targets of hypertension. In addition, the ACE inhibition rates of Lactiplantibacillus plantarum SR37-3 and Lactiplantibacillus plantarum SR61-2 in vitro were 70.5% and 68.9%, respectively. Our research provides new insights into novel and safe options for hypertension treatment.

Influences of Oral Administration of Probiotics on Posthepatectomy Recovery in Patients in Child-Pugh Grade

Objective

This study is aimed at investigating the influences of oral administration of probiotics on posthepatectomy recovery in patients in Child-Pugh grade.

Methods

100 patients (50 cases in Child-Pugh A grade and 50 cases in Child-Pugh B grade) underwent hepatectomy in our hospital from January 2018 to January 2020 were involved in this study. Subsequently, Child-Pugh A grade and Child-Pugh B grade patients were set as probiotics group (taking Clostridium butyricum, n = 25) and control group (no probiotics, n = 25). The general information, infectious indexes, and liver function indexes on days 1, 3, and 5 after operation were collected.

Results

In Child-Pugh B grade subgroup patients, the procalcitonin, alanine aminotransferase, and prothrombin time of the probiotics group were statistically significantly lower than that of the control group on days 3 (P < 0.05) and 5 (P < 0.05) after surgery. In Child-Pugh A grade subgroup patients, there were no significant differences between probiotics group and control group after operation.

Conclusion

Child-Pugh A grade subgroup patients with hepatectomy could not benefit from oral probiotics. However, Child-Pugh B grade subgroup patients taking probiotics after hepatectomy could reduce postoperative infection and accelerate recovery of liver function.

Interplay between Dysbiosis of Gut Microbiome, Lipid Metabolism, and Tumorigenesis: Can Gut Dysbiosis Stand as a Prognostic Marker in Cancer?

The gut bacterial community is involved in the metabolism of bile acids and short-chain fatty acids (SCFAs). Bile acids are involved in the absorption of fat and the regulation of lipid homeostasis through emulsification and are transformed into unconjugated bile acids by the gut microbiota. The gut microbiota is actively involved in the production of bile acid metabolites, such as deoxycholic acid, lithocholic acid, choline, and SCFAs such as acetate, butyrate, and propionate. Metabolites derived from the gut microbiota or modified gut microbiota metabolites contribute significantly to host pathophysiology. Gut bacterial metabolites, such as deoxycholic acid, contribute to the development of hepatocellular carcinoma and colon cancer by factors such as inflammation and oxidative DNA damage. Butyrate, which is derived from gut bacteria such as Megasphaera, Roseburia, Faecalibacterium, and Clostridium, is associated with the activation of Treg cell differentiation in the intestine through histone acetylation. Butyrate averts the action of class I histone deacetylases (HDAC), such as HDAC1 and HDAC3, which are responsible for the transcription of genes such as p21/Cip1, and cyclin D3 through hyperacetylation of histones, which orchestrates G1 cell cycle arrest. It is essential to identify the interaction between the gut microbiota and bile acid and SCFA metabolism to understand their role in gastrointestinal carcinogenesis including colon, gastric, and liver cancer. Metagenomic approaches with bioinformatic analyses are used to identify the bacterial species in the metabolism of bile acids and SCFAs. This review provides an overview of the current knowledge of gut microbiota-derived bile acid metabolism in tumor development and whether it can stand as a marker for carcinogenesis. Additionally, this review assesses the evidence of gut microbiota-derived short-chain fatty acids including butyric acid in antitumor activity. Future research is required to identify the beneficial commensal gut bacteria and their metabolites which will be considered to be therapeutic targets in inflammation-mediated gastrointestinal cancers.

RNA-Seq unveiled section-specific host response to lack of gut microbiota in mouse intestine

To identify host responses induced by commensal microbiota in intestine, transcriptomes of four sections of the intestine were compared between germ-free (GF) mice and conventional (CV) controls using RNA-Seq. Cuffdiff revealed that jejunum had the highest number of differentially expressed genes (over 2000) between CV and GF mice, followed by large intestine (LI), duodenum, and ileum. Gene set association analysis identified section-specific alterations in pathways associated with the absence of commensal microbiota. For example, in GF mice, cytochrome P450 (Cyp)-mediated xenobiotic metabolism was preferably down-regulated in duodenum and ileum, whereas intermediary metabolism pathways such as protein digestion and amino acid metabolism were preferably up-regulated in duodenum, jejunum, and LI. In GF mice, carboxypeptidase A1 (Cpa1), which is important for protein digestion, was the top most up-regulated gene within the entire transcriptome in duodenum (53-fold) and LI (142-fold). Conversely, fatty acid binding protein 6 (Fabp6/Ibabp), which is important for bile acid intestinal reabsorption, was the top most down-regulated gene in jejunum (358-fold), and the drug-metabolizing enzyme Cyp1a1 was the top most down-regulated gene in ileum (40-fold). Section-specific host transcriptomic response to the absence of intestinal microbiota was also observed for other important physiological pathways such as cell junction, the absorption of small molecules, bile acid homeostasis, and immune response. In conclusion, the present study has revealed section-specific host gene transcriptional alterations in GF mice, highlighting the importance of intestinal microbiota in facilitating the physiological and drug responses of the host intestine.

Alterations in Faecal Metagenomics and Serum Metabolomics Indicate Management Strategies for Patients With Budd-Chiari Syndrome

We investigated the effects of gut microbiota and serum metabolite levels in patients with Budd-Chiari syndrome (B-CS) and their importance for guiding clinical management strategies. In total, 214 B-CS patients (93 untreated and 121 treated) and 41 healthy controls were enrolled. Gut microbiota and serum metabolome were analysed using shotgun metagenomics and liquid chromatography-mass spectrometry. The gut microbiota of the patients showed abundance of Campylobacter and low levels of Saccharomyces, Deinococcus, and Thiomonas (P < 0.05). Thirty metabolites, including taurocholate and (R)-3-hydroxybutyric acid, were identified in the patients (VIP > 1, P < 0.05 and FC > 1.2 or FC < 0.83). Random forest (RF) models showed that serum metabolome could effectively identify B-CS from healthy controls and RF-metabolomics exhibited perfect discrimination (AUC = 100%, 95% CI: 100% – 100%), which was significantly higher than that achieved by RF-metagenomics (AUC = 58.48%, 95% CI: 38.46% – 78.5%). Campylobacter concisus and taurocholate showed significant positive correlation in patients with clinical manifestations (P < 0.05). Actinobacteria levels were significantly higher in untreated patients than in treated patients (P < 0.05). Campylobacter and Veillonella levels were significantly higher in treated patients than in healthy controls (P < 0.05). We identified major alterations in the gut microbiota and serum metabolome of patients with B-CS. Faecal metagenomics- and serum metabolomics-guided management strategies are required for patients with B-CS.

Methionine Deficiency Affects Liver and Kidney Health, Oxidative Stress, and Ileum Mucosal Immunity in Broilers

Methionine (Met) is the first limiting amino acid in broiler diets, but its unclear physiological effects hamper its effective use in the poultry production industry. This study assessed the effect of a Met-deficient (MD) diet on chicken liver and kidney health, exploring the associated mechanisms of antioxidant capacity and ileum mucosal immunity. Seventy-two broilers were administered either the control diet (0.46% Met in starter diet, 0.36% Met in grower diet) or the MD diet (0.22% Met in starter diet, 0.24% Met in grower diet). Liver and kidney samples were collected every 14 days for anatomical, histological, and ultrastructural analyses, accompanied by oxidative stress assessment. Meanwhile, T- and B-lymphocyte abundance and essential cytokine gene expression were measured in the ileum, the center of the gut–liver–kidney axis. Signs of kidney and liver injury were observed morphologically in the MD group at 42 days of age. Furthermore, aspartate aminotransferase, alanine aminotransferase, creatinine, and uric acid levels were decreased in the MD group compared with the control group, accompanied by decreased superoxide dismutase activity, increased malondialdehyde content, decreased numbers of T and B lymphocytes, and decreased cytokine expression in the ileum, such as IL-2, IL-6, LITAF, and IFN-γ. These results suggest that MD can induce kidney and liver injury, and the injury pathway might be related to oxidative stress and intestinal immunosuppression.

An 'Omics Approach to Unraveling the Paradoxical Effect of Diet on Perfluorooctanesulfonic Acid (PFOS) and Perfluorononanoic Acid (PFNA)-Induced Hepatic Steatosis

Perfluoroalkyl substances (PFAS) are a family of toxicants universally detected in human serum and known to cause dyslipidemia in animals and humans. Hepatic steatosis, which is defined as lipid deposition in the liver, is known to be a consequence of poor diet. Similarly, PFAS are known to induce hepatic steatosis in animals on a low-fat chow. This study explored diet-PFAS interactions in the liver and their potential to modulate hepatic steatosis. Male C57BL/6J mice were fed with either a low-fat diet (10% kcal from fat, LFD) or a moderately high-fat diet (45% kcal from fat, HFD) with or without perfluorooctanesulfonic acid (3 ppm, PFOS) or perfluorononanoic acid (3 ppm, PFNA) in feed for 12 weeks. Livers were excised for histology and quantification of PFAS and lipids. The PFOS and PFNA coadministration with HFD reduced the hepatic accumulation of lipid and PFAS relative to the LFD treatment groups. Furthermore, transcriptomic analysis revealed that PFAS administration in the presence of an HFD significantly reduces expression of known hepatic PFAS uptake transporters, organic anion transporter proteins. Transcriptomics and proteomics further revealed several pathways related to lipid metabolism, synthesis, transport, and storage that were modulated by PFAS exposure and further impacted by the presence of dietary fat. Both dietary fat content and the chemical functional head group exerted significant influence on hepatic PFAS accumulation and the resulting biochemical signature, suggesting that diet and structure should be considered in the design and interpretation of research on PFAS induced hepatic steatosis.

Gut Microbiome Critically Impacts PCB-induced Changes in Metabolic Fingerprints and the Hepatic Transcriptome in Mice

Polychlorinated biphenyls (PCBs) are ubiquitously detected and have been linked to metabolic diseases. Gut microbiome is recognized as a critical regulator of disease susceptibility; however, little is known how PCBs and gut microbiome interact to modulate hepatic xenobiotic and intermediary metabolism. We hypothesized the gut microbiome regulates PCB-mediated changes in the metabolic fingerprints and hepatic transcriptome. Ninety-day-old female conventional and germ-free mice were orally exposed to the Fox River Mixture (synthetic PCB mixture, 6 or 30 mg/kg) or corn oil (vehicle control, 10 ml/kg), once daily for 3 consecutive days. RNA-seq was conducted in liver, and endogenous metabolites were measured in liver and serum by LC-MS. Prototypical target genes of aryl hydrocarbon receptor, pregnane X receptor, and constitutive androstane receptor were more readily upregulated by PCBs in conventional conditions, indicating PCBs, to the hepatic transcriptome, act partly through the gut microbiome. In a gut microbiome-dependent manner, xenobiotic, and steroid metabolism pathways were upregulated, whereas response to misfolded proteins-related pathways was downregulated by PCBs. At the high PCB dose, NADP, and arginine appear to interact with drug-metabolizing enzymes (ie, Cyp1-3 family), which are highly correlated with Ruminiclostridium and Roseburia, providing a novel explanation of gut-liver interaction from PCB-exposure. Utilizing the Library of Integrated Network-based Cellular Signatures L1000 database, therapeutics targeting anti-inflammatory and endoplasmic reticulum stress pathways are predicted to be remedies that can mitigate PCB toxicity. Our findings demonstrate that habitation of the gut microbiota drives PCB-mediated hepatic responses. Our study adds knowledge of physiological response differences from PCB exposure and considerations for further investigations for gut microbiome-dependent therapeutics.

Effect of Additional Clostridium butyricum on the Intestinal Flora of Chronic Hepatitis B Patients Treated with Entecavir

INTRODUCTION

To explore the influence of intestinal flora on the occurrence, development and antiviral therapy of chronic hepatitis B (CHB), 16S rDNA amplification sequencing was performed to investigate the intestinal flora in CHB patients treated with entecavir (ETV) and Clostridium butyricum (CB).

METHODS

CHB patients were divided into the ETV group (treatment with ETV alone) and ETV + CB group (treatment with ETV and CB). After 8-week treatment, feces samples were collected and processed for 16S rDNA amplicon sequencing; blood samples were collected for the biochemical, immunologic and virologic evaluations, which were compared between groups.

RESULTS

ETV treatment for 8 weeks significantly decreased the serum levels of alanine aminotransferase (ALT), interleukin-6 (IL-6), IL-8, tumor necrosis factor-α (TNF-α) and HBV DNA compared to those before treatment, but there were no marked differences between the ETV group and ETV + CB group. The intestinal flora changed significantly in the CHB patients after ETV + CB treatment: there were marked differences in 13 unique species before treatment and 4 unique species after ETV + CB treatment; at the phylum level, the top five bacteria with significant difference between patients before treatment and ETV + CB patients were Firmicutes, Actinobacteria, Cyanobacteria, Euryarchaeota and Synergistetes. There were significant differences in 25 unique species in the ETV group and 4 unique species in the ETV + CB group; at the phylum level, the top five bacteria with significant difference between ETV patients and ETV + CB patients were Actinobacteria, Fusobacteria, Proteobacteria, Saccharibacteria and Synergistetes.

CONCLUSION

ETV treatment improves the serum biochemical, immunologic and virologic variables, but additional CB fails to further improve these variables. Of note, additional CB affects the intestinal flora in the CHB patients treated with ETV.

Interaction Between the Intestinal Microbial Community and Transcriptome Profile in Common Carp (Cyprinus carpio L.)

In a previous study, we found that the growth performance of the new strain of Huanghe carp is related to gene expression and bacterial community in the gut. In order to better understand the relationship between the gene expression level and bacterial abundance in the gut, we studied the growth performance, gut bacterial structure, and transcriptome profile in the 4th generation of the new carp strain (selection group) at harvesting time, and compared them with the control line (traditional Huanghe carp). Body weight, depth, width, and length increased 14.58, 7.14, 5.04, and 5.07%, respectively. The gut microbiome of the selection group also exhibited significantly higher species diversity parameters (Shannon, Simpson, and chao1). Both PCA and phylogenetic analyses divided all gut samples into two parts: control and selection group. Aeromonas was the dominant taxon in the control group, followed by Firmicutes and Roseomonas; in the selection group, Roseomonas was the dominant taxon, followed by Firmicutes and then Aeromonas. Among the 249 significantly differentially expressed genes, 194 were downregulated and 55 were upregulated. Functional GO annotation produced 13 terms in the biological process, 8 in the cellular component, and 7 in the molecular function categories. KEGG annotation indicated that most of these genes were associated with the immune-related pathways. A total of 2,892 pairs of genes (245) and baceterial genera (256) were analyzed using Pearson's correlation analysis. Most of the identified associations were mapped to the immune system, bacterial community, and cell differentiation categories. The top-10 bacterial genera identified by these analyses were Methylocystis, Ohtaekwangia, Roseomonas, Shewanella, Lutispora, GpVI, Desulfovibrio, Candidatus_Berkiella, Bordetella, and Azorhizobium. Genes paired with bacteria flora were divided into four functional categories: immune, growth, adipocyte differentiation, and nerve regulation. These genes may be related to the comparatively fast growth and high muscle polyunsaturated fatty acid content of the Huanghe carp new strain. Meanwhile, nerve regulation-related genes may be a reflection of the microbiota-gut-brain axis. These results illustrate that gut bacterial community structure is associated with the growth performance and gene expression in the Huanghe carp new strain.

Examining the gut-liver axis in liver cancer using organoid models

The World Health Organization predicts that by 2030 liver cancer will cause 1 million deaths annually, thus becoming the third most lethal cancer worldwide. Hepatocellular carcinoma and cholangiocarcinoma are the two major primary cancer subtypes involving the liver. Both are often diagnosed late, and hence response to treatment and survival are poor. It is therefore of utmost importance to understand the mechanisms by which liver cancers initiate and progress. The causes of primary liver cancer are diverse, resulting primarily from obesity, chronic alcohol abuse or viral hepatitis. Importantly, both alcohol and high fat diet can promote intestinal permeability, enabling microbial translocation from the gut into the liver. As a result, these microbial antigens and metabolites exacerbate hepatic inflammation and fibrosis, increasing the risk of primary liver cancer. Organoids are primary, three-dimensional, stem cell derived liver models that can recapitulate many of the disease phenotypes observed in vivo. This review aims to summarize the advantages of organoid culture to examine the gut-liver axis with respect to cancer initiation and progression. In particular, the use of gut and liver organoid mono- and co-cultures together and with immune cell populations to best recapitulate disease mechanisms and develop therapeutic interventions.

Modeling Pharmacokinetic Natural Product-Drug Interactions for Decision-Making: A NaPDI Center Recommended Approach

The popularity of botanical and other purported medicinal natural products (NPs) continues to grow, especially among patients with chronic illnesses and patients managed on complex prescription drug regimens. With few exceptions, the risk of a given NP to precipitate a clinically significant pharmacokinetic NP-drug interaction (NPDI) remains understudied or unknown. Application of static or dynamic mathematical models to predict and/or simulate NPDIs can provide critical information about the potential clinical significance of these complex interactions. However, methods used to conduct such predictions or simulations are highly variable. Additionally, published reports using mathematical models to interrogate NPDIs are not always sufficiently detailed to ensure reproducibility. Consequently, guidelines are needed to inform the conduct and reporting of these modeling efforts. This recommended approach from the Center of Excellence for Natural Product Drug Interaction Research describes a systematic method for using mathematical models to interpret the interaction risk of NPs as precipitants of potential clinically significant pharmacokinetic NPDIs. A framework for developing and applying pharmacokinetic NPDI models is presented with the aim of promoting accuracy, reproducibility, and generalizability in the literature. SIGNIFICANCE STATEMENT: Many natural products (NPs) contain phytoconstituents that can increase or decrease systemic or tissue exposure to, and potentially the efficacy of, a pharmaceutical drug; however, no regulatory agency guidelines exist to assist in predicting the risk of these complex interactions. This recommended approach from a multi-institutional consortium designated by National Institutes of Health as the Center of Excellence for Natural Product Drug Interaction Research provides a framework for modeling pharmacokinetic NP-drug interactions.

The diversity of gut microbiota in type 2 diabetes with or without cognitive impairment

BACKGROUND

Diabetes is associated with a high risk of developing cognitive impairment, but the underlying mechanism remains unclear. Recent studies have found that gut microbiota may be involved in the progression of diabetes-associated cognitive impairment.

AIMS

To analyze the diversity of gut microbiota in type 2 diabetes with or without cognitive impairment METHODS: 16S rRNA sequencing was used to detect the gut microbiota composition in 154 type 2 diabetes (T2DM) subjects RESULTS: Among 154 elderly T2DM participants included in our study, 73 with normal and 81 with impaired cognition. Lower levels of hemoglobin and HDL were observed in subjects with cognitive impairment. Patients with cognitive impairment had a lower abundance of Tenericutes. Comparison at the genus level revealed that T2DM patients with cognitive impairment had a decreased abundance of Bifidobacterium and unranked-RF39 and an increased abundance of Peptococcus and unranked-Leuconostocaceae. Additionally, the relative abundance of Veillonella and Pediococcus were decreased in subjects with cognitive impairment. Furthermore, the relative abundance of 7 sub-functions was significantly changed in the group with cognitive impairment. Calcium signaling pathways and the Renin-angiotensin system were upregulated in the cognitive impairment group while GnRH signaling, Fc gamma R-mediated phagocytosis, endocytosis, isoflavonoid biosynthesis, and cytochrome P450 were deregulated.

CONCLUSION

Bifidobacterium may be associated with cognition in T2DM. Calcium signaling and renin-angiotensin system were shown to be associated with diabetes-associated cognitive impairment through gut microbiota.

Effect of Entecavir on the Intestinal Microflora in Patients with Chronic Hepatitis B: A Controlled Cross-Sectional and Longitudinal Real-World Study

Introduction

This study aimed to analyze the diversity of intestinal flora in patients with chronic hepatitis B (CHB) and investigate the effect of entecavir on the intestinal flora in these patients.

Methods

Thirty patients with CHB and 30 healthy controls were recruited from the Department of Infectious Diseases and Department of Gastroenterology of Shanghai Tongji Hospital between January 2017 and December 2018. Stool samples were collected for the detection of intestinal flora by high-throughput sequencing. Patients with CHB received antivirus therapy with entecavir for 8 weeks. The biochemical and virological responses were assessed and the intestinal flora were compared.

Results

After entecavir treatment, the blood levels of alanine aminotransferase (ALT), interleukin-6 (IL-6), IL-8, tumor necrosis factor (TNF), and hepatitis B virus (HBV) DNA reduced significantly in patients with CHB and the species abundance of intestinal flora increased markedly. In patients with CHB, the unique genera included Butyrivibrio, Phaseolus acutifolius, and Prevotellaceae NK3B31 group before treatment and Howardella, Candidatus Stoquefichus, Citrobacter, Dysgonomonas, Faecalicoccus, Methanobrevibacter, Mitsuokella, Mobilitalea, Succinivibrio, Gluconobacter, and Plesiomonas after treatment. The abundance of the following genera increased significantly after entecavir treatment in patients with CHB: Clostridium sensu stricto 1, Erysipelotrichaceae UCG-007, and Intestinibacter. The abundance of Streptococcus, Atopobium, and Murdochiella reduced markedly after entecavir treatment in patients with CHB.

Conclusion

After 8-week entecavir treatment, the blood biochemical, immunological, and virological responses improved significantly, the species abundance of intestinal flora increased markedly, and there were unique genera in patients with CHB before and after treatment.

Electronic supplementary material

The online version of this article (10.1007/s40121-020-00355-w) contains supplementary material, which is available to authorized users.

Bioavailability Based on the Gut Microbiota: a New Perspective

The substantial discrepancy between the strong effects of functional foods and various drugs, especially traditional Chinese medicines (TCMs), and the poor bioavailability of these substances remains a perplexing problem. Understanding the gut microbiota, which acts as an effective bioreactor in the human intestinal tract, provides an opportunity for the redefinition of bioavailability. Here, we discuss four different pathways associated with the role of the gut microbiota in the transformation of parent compounds to beneficial or detrimental small molecules, which can enter the body's circulatory system and be available to target cells, tissues, and organs. We further describe and propose effective strategies for improving bioavailability and alleviating side effects with the help of the gut microbiota. This review also broadens our perspectives for the discovery of new medicinal components.

Pharmacological Activation of PXR and CAR Downregulates Distinct Bile Acid-Metabolizing Intestinal Bacteria and Alters Bile Acid Homeostasis

The gut microbiome regulates important host metabolic pathways including xenobiotic metabolism and intermediary metabolism, such as the conversion of primary bile acids (BAs) into secondary BAs. The nuclear receptors pregnane X receptor (PXR) and constitutive androstane receptor (CAR) are well-known regulators for xenobiotic biotransformation in liver. However, little is known regarding the potential effects of PXR and CAR on the composition and function of the gut microbiome. To test our hypothesis that activation of PXR and CAR regulates gut microbiota and secondary BA synthesis, 9-week-old male conventional and germ-free mice were orally gavaged with corn oil, PXR agonist PCN (75 mg/kg), or CAR agonist TCPOBOP (3 mg/kg) once daily for 4 days. PCN and TCPOBOP decreased two taxa in the Bifidobacterium genus, which corresponded with decreased gene abundance of the BA-deconjugating enzyme bile salt hydrolase. In liver and small intestinal content of germ-free mice, there was a TCPOBOP-mediated increase in total, primary, and conjugated BAs corresponding with increased Cyp7a1 mRNA. Bifidobacterium, Dorea, Peptociccaceae, Anaeroplasma, and Ruminococcus positively correlated with T-UDCA in LIC, but negatively correlated with T-CDCA in serum. In conclusion, PXR and CAR activation downregulates BA-metabolizing bacteria in the intestine and modulates BA homeostasis in a gut microbiota-dependent manner.

Gut Microbiota Modulates Interactions Between Polychlorinated Biphenyls and Bile Acid Homeostasis

The gut microbiome is increasingly recognized as a second genome that contributes to the health and diseases of the host. A major function of the gut microbiota is to convert primary bile acids (BAs) produced from cholesterol in the liver into secondary BAs that activate distinct host receptors to modulate xenobiotic metabolism and energy homeostasis. The goal of this study was to investigate to what extent oral exposure to an environmentally relevant polychlorinated biphenyl (PCBs mixture), namely the Fox River mixture, impacts gut microbiome and BA homeostasis. Ninety-day-old adult female conventional (CV) and germ-free (GF) C57BL/6 mice were orally exposed to corn oil (vehicle), or the Fox River mixture at 6 or 30 mg/kg once daily for 3 consecutive days. The PCB low dose profoundly increased BA metabolism related bacteria Akkermansia (A.) muciniphila, Clostridium (C.) scindens, and Enterococcus in the large intestinal pellet (LIP) of CV mice (16S rRNA sequencing/qPCR). This correlated with a PCB low dose-mediated increase in multiple BAs in serum and small intestinal content (SIP) in a gut microbiota-dependent manner (UPLC-MS/MS). Conversely, at PCB high dose, BA levels remained stable in CV mice correlated with an increase in hepatic efflux transporters and ileal Fgf15. Interestingly, lack of gut microbiota potentiated the PCB-mediated increase in taurine conjugated α and β muricholic acids in liver, SIP, and LIP. Pearson's correlation identified positive correlations between 5 taxa and most secondary BAs. In conclusion, PCBs dose-dependently altered BA homeostasis through a joint effort between host gut-liver axis and intestinal bacteria.

Impact of Vitamin D Deficit on the Rat Gut Microbiome

Inadequate immunologic, metabolic and cardiovascular homeostasis has been related to either an alteration of the gut microbiota or to vitamin D deficiency. We analyzed whether vitamin D deficiency alters rat gut microbiota. Male Wistar rats were fed a standard or a vitamin D-free diet for seven weeks. The microbiome composition was determined in fecal samples by 16S rRNA gene sequencing. The vitamin D-free diet produced mild changes on α- diversity but no effect on β-diversity in the global microbiome. Markers of gut dysbiosis like Firmicutes-to-Bacteroidetes ratio or the short chain fatty acid producing bacterial genera were not significantly affected by vitamin D deficiency. Notably, there was an increase in the relative abundance of the Enterobacteriaceae, with significant rises in its associated genera Escherichia, Candidatus blochmannia and Enterobacter in vitamin D deficient rats. Prevotella and Actinomyces were also increased and Odoribacteraceae and its genus Butyricimonas were decreased in rats with vitamin D-free diet. In conclusion, vitamin D deficit does not induce gut dysbiosis but produces some specific changes in bacterial taxa, which may play a pathophysiological role in the immunologic dysregulation associated with this hypovitaminosis.

Microbiome is a functional modifier of P450 drug metabolism

Host cytochrome P450s (P450s) play important roles in the bioactivation and detoxification of numerous therapeutic drugs, environmental toxicants, dietary factors, as well as endogenous compounds. Gut microbiome is increasingly recognized as our "second genome" that contributes to the xenobiotic biotransformation of the host, and the first pass metabolism of many orally exposed chemicals is a joint effort between host drug metabolizing enzymes including P450s and gut microbiome. Gut microbiome contributes to the drug metabolism via two distinct mechanisms: direct mechanism refers to the metabolism of drugs by microbial enzymes, among which reduction and hydrolysis (or deconjugation) are among the most important reactions; whereas indirect mechanism refers to the influence of host receptors and signaling pathways by microbial metabolites. Many types of microbial metabolites, such as secondary bile acids (BAs), short chain fatty acids (SCFAs), and tryptophan metabolites, are known regulators of human diseases through modulating host xenobiotic-sensing receptors. To study the roles of gut microbiome in regulating host drug metabolism including P450s, several models including germ free mice, antibiotics or probiotics treatments, have been widely used. The present review summarized the current information regarding the interactions between microbiome and the host P450s in xenobiotic biotransformation organs such as liver, intestine, and kidney, highlighting the remote sensing mechanisms underlying gut microbiome mediated regulation of host xenobiotic biotransformation. In addition, the roles of bacterial, fungal, and other microbiome kingdom P450s, which is an understudied area of research in pharmacology and toxicology, are discussed.

Gut microbiome: An intermediary to neurotoxicity

There is growing recognition that the gut microbiome is an important regulator for neurological functions. This review provides a summary on the role of gut microbiota in various neurological disorders including neurotoxicity induced by environmental stressors such as drugs, environmental contaminants, and dietary factors. We propose that the gut microbiome remotely senses and regulates CNS signaling through the following mechanisms: 1) intestinal bacteria-mediated biotransformation of neurotoxicants that alters the neuro-reactivity of the parent compounds; 2) altered production of neuro-reactive microbial metabolites following exposure to certain environmental stressors; 3) bi-directional communication within the gut-brain axis to alter the intestinal barrier integrity; and 4) regulation of mucosal immune function. Distinct microbial metabolites may enter systemic circulation and epigenetically reprogram the expression of host genes in the CNS, regulating neuroinflammation, cell survival, or cell death. We will also review the current tools for the study of the gut-brain axis and provide some suggestions to move this field forward in the future.

Liver tumorigenesis is promoted by a high saturated fat diet specifically in male mice and is associated with hepatic expression of the proto-oncogene Agap2 and enrichment of the intestinal microbiome with Coprococcus

Liver cancer results in a high degree of mortality, especially among men. As fatty liver disease is a risk factor for development of hepatocellular carcinoma, we investigated the role of dietary fat type in tumor promotion by high-fat diets in mice after initiation with the chemical carcinogen diethyl nitrosamine. Tumor incidence and multiplicity were significantly greater in males than those in females. In males, fat type had complex effects on tumorigenesis. Preneoplastic foci were most prevalent in mice fed a polyunsaturated fat diet enriched in docosahexaenoic acid, whereas carcinomas and large visible liver tumors were significantly greater in mice fed a saturated fat diet made with cocoa butter relative to mice fed mono- or polyunsaturated fats. Different mechanisms thus seemed involved in early and late tumor promotion. The hepatic transcriptome and gut microbiome were assessed for traits associated with tumorigenesis. Hepatic expression of more than 20% of all genes was affected by sex, whereas fat type affected fewer genes. In males, the saturated fat diet induced expression of the proto-oncogene Agap2 and affected the expression of several cytochrome P450 genes, and genes involved in lipid, bile acid and fatty acid metabolism. The gut microbiome had a higher level of genus Akkermansia and a lower level of Firmicutes in females than in males. Males fed saturated fat had an altered microbiome, including an enrichment of the genus Coprococcus. In conclusion, sex and the dietary fat type affect the gut microbiome, the hepatic transcriptome and ultimately hepatic tumor growth.

Contribution of the gut microbiota to the regulation of host metabolism and energy balance: a focus on the gut–liver axis

This review presents mechanistic studies performed in vitro and in animal models, as well as data obtained in patients that contribute to a better understanding of the impact of nutrients interacting with the gut microbiota on metabolic and behavioural alterations linked to obesity. The gut microbiota composition and function are altered in several pathological conditions including obesity and related diseases i.e. non-alcoholic fatty liver diseases (NAFLD). The gut–liver axis is clearly influenced by alterations of the gut barrier that drives inflammation. In addition, recent papers propose that specific metabolites issued from the metabolic cooperation between the gut microbes and host enzymes, modulate inflammation and gene expression in the liver. This review illustrates how dietary intervention with prebiotics or probiotics influences host energy metabolism and inflammation. Indeed, intervention studies are currently underway in obese and NAFLD patients to unravel the relevance of the changes in gut microbiota composition in the management of metabolic and behavioural disorders by nutrients interacting with the gut microbiota. In conclusion, diet is among the main triggers of NAFLD and the gut microbiota is modified accordingly, underlining the importance of the concomitant study of the nutrients and microbial impact on liver health and metabolism, in order to propose innovative, clinically relevant, therapeutic approaches.

Deciphering the Anti-obesity Benefits of Resveratrol: The "Gut Microbiota-Adipose Tissue" Axis

Excessive white adipose tissue (WAT) accumulation due to an imbalance between caloric intake and energy expenditure (EE) characterizes obesity. However, brown adipose tissue (BAT) is highly specialized for the dissipation of energy. Recent evidence indicated that the activation of BAT and the induction of WAT browning might be promising approaches to combat obesity by increasing EE and regulating glucose and lipid metabolism. Resveratrol, which is a polyphenolic compound, has been widely acknowledged to have protective effects against obesity and related metabolic disorders. The induction of WAT browning has been considered as one of the crucial factors in the metabolic benefits of resveratrol. Nevertheless, the specific mechanism that is involved is largely unclear. As a prebiotic-like polyphenol, resveratrol is able to modulate the composition of gut microbiota. In addition, in recent years, the impact of gut microbiota on the browning of WAT has received increasing attention and has been initially confirmed to play a role. By considering all these factors, this review explores the potential link between dietary resveratrol and the browning of WAT, which may be modulated by gut microbiota and their metabolites and proposes the "gut microbiota- adipose tissue" axis plays a vital role in the anti-obesity effects of resveratrol. This observation might provide novel insights and targets that could be used for fighting against obesity and associated metabolic disorders.

Coordinate regulation of long non-coding RNAs and protein-coding genes in germ-free mice

BACKGROUND

Long non-coding RNAs (lncRNAs) are increasingly recognized as regulators of tissue-specific cellular functions and have been shown to regulate transcriptional and translational processes, acting as signals, decoys, guides, and scaffolds. It has been suggested that some lncRNAs act in cis to regulate the expression of neighboring protein-coding genes (PCGs) in a mechanism that fine-tunes gene expression. Gut microbiome is increasingly recognized as a regulator of development, inflammation, host metabolic processes, and xenobiotic metabolism. However, there is little known regarding whether the gut microbiome modulates lncRNA gene expression in various host metabolic organs. The goals of this study were to 1) characterize the tissue-specific expression of lncRNAs and 2) identify and annotate lncRNAs differentially regulated in the absence of gut microbiome.

RESULTS

Total RNA was isolated from various tissues (liver, duodenum, jejunum, ileum, colon, brown adipose tissue, white adipose tissue, and skeletal muscle) from adult male conventional and germ-free mice (n = 3 per group). RNA-Seq was conducted and reads were mapped to the mouse reference genome (mm10) using HISAT. Transcript abundance and differential expression was determined with Cufflinks using the reference databases NONCODE 2016 for lncRNAs and UCSC mm10 for PCGs. Although the constitutive expression of lncRNAs was ubiquitous within the enterohepatic (liver and intestine) and the peripheral metabolic tissues (fat and muscle) in conventional mice, differential expression of lncRNAs by lack of gut microbiota was highly tissue specific. Interestingly, the majority of gut microbiota-regulated lncRNAs were in jejunum. Most lncRNAs were co-regulated with neighboring PCGs. STRING analysis showed that differentially expressed PCGs in proximity to lncRNAs form tissue-specific networks, suggesting that lncRNAs may interact with gut microbiota/microbial metabolites to regulate tissue-specific functions.

CONCLUSIONS

This study is among the first to demonstrate that gut microbiota critically regulates the expression of lncRNAs not only locally in intestine but also remotely in other metabolic organs, suggesting that common transcriptional machinery may be shared to transcribe lncRNA-PCG pairs, and lncRNAs may interact with PCGs to regulate tissue-specific pathways.

Dietary Tomato Powder Inhibits High-Fat Diet-Promoted Hepatocellular Carcinoma with Alteration of Gut Microbiota in Mice Lacking Carotenoid Cleavage Enzymes

Both incidence and death rate due to liver cancer have increased in the United States. Higher consumption of lycopene-rich tomato and tomato products is associated with a decreased risk of cancers. β-Carotene-15, 15'-oxygenase (BCO1), and β-carotene-9', 10'-oxygenase (BCO2) cleave lycopene to produce bioactive apo-lycopenoids. Although BCO1/BCO2 polymorphisms affect human and animal lycopene levels, whether dietary tomato consumption can inhibit high-fat diet (HFD)-promoted hepatocellular carcinoma (HCC) development and affect gut microbiota in the absence of BCO1/BCO2 is unclear. BCO1/BCO2 double knockout mice were initiated with a hepatic carcinogen (diethylnitrosamine) at 2 weeks of age. At 6 weeks of age, the mice were randomly assigned to an HFD (60% of energy as fat) with or without tomato powder (TP) feeding for 24 weeks. Results showed that TP feeding significantly decreased HCC development (67%, 83%, and 95% reduction in incidence, multiplicity, and tumor volume, respectively, P < 0.05). Protective effects of TP feeding were associated with (1) decreased hepatic inflammatory foci development and mRNA expression of proinflammatory biomarkers (IL1β, IL6, IL12α, monocyte chemoattractant protein-1, and inducible NO synthase); (2) increased mRNA expression of deacetylase sirtuin 1 and nicotinamide phosphoribosyltransferase involving NAD⁺ production; and (3) increased hepatic circadian clock genes (circadian locomotor output cycles kaput, period 2, and cryptochrome-2, Wee1). Furthermore, TP feeding increased gut microbial richness and diversity, and significantly decreased the relative abundance of the genus Clostridium and Mucispirillum, respectively. The present study demonstrates that dietary tomato feeding independent of carotenoid cleavage enzymes prevents HFD-induced inflammation with potential modulating gut microbiota and inhibits HFD-promoted HCC development.

Gut microbiota modulates drug pharmacokinetics

Gut microbiota, one of the determinants of pharmacokinetics, has long been underestimated. It is now generally accepted that the gut microbiota plays an important role in drug metabolism during enterohepatic circulation either before drug absorption or through various microbial enzymatic reactions in the gut. In addition, some drugs are metabolized by the intestinal microbiota to specific metabolites that cannot be formed in the liver. More importantly, metabolizing drugs through the gut microbiota prior to absorption can alter the systemic bioavailability of certain drugs. Therefore, understanding intestinal flora-mediated drug metabolism is critical to interpreting changes in drug pharmacokinetics. Here, we summarize the effects of gut microbiota on drug pharmacokinetics, and propose that the influence of intestinal flora on pharmacokinetics should be organically related to the therapeutic effects and side effects of drugs. More importantly, we could rationally perform the strategy of intestinal microflora-mediated metabolism to design drugs.

Regulation of protein-coding gene and long noncoding RNA pairs in liver of conventional and germ-free mice following oral PBDE exposure

Gut microbiome communicates with the host liver to modify hepatic xenobiotic biotransformation and nutrient homeostasis. Polybrominated diphenyl ethers (PBDEs) are persistent environmental contaminants that are detected in fatty food, household dust, and human breast milk at worrisome levels. Recently, long noncoding RNAs (lncRNAs) have been recognized as novel biomarkers for toxicological responses and may regulate the transcriptional/translational output of protein-coding genes (PCGs). However, very little is known regarding to what extent the interactions between PBDEs and gut microbiome modulate hepatic lncRNAs and PCGs, and what critical signaling pathways are impacted at the transcriptomic scale. In this study, we performed RNA-Seq in livers of nine-week-old male conventional (CV) and germ-free (GF) mice orally exposed to the most prevalent PBDE congeners BDE-47 and BDE-99 (100 μmol/kg once daily for 4-days; vehicle: corn oil, 10 ml/kg), and unveiled key molecular pathways and PCG-lncRNA pairs targeted by PBDE-gut microbiome interactions. Lack of gut microbiome profoundly altered the PBDE-mediated transcriptomic response in liver, with the most prominent effect observed in BDE-99-exposed GF mice. The top pathways up-regulated by PBDEs were related to xenobiotic metabolism, whereas the top pathways down-regulated by PBDEs were in lipid metabolism and protein synthesis in both enterotypes. Genomic annotation of the differentially regulated lncRNAs revealed that majority of these lncRNAs overlapped with introns and 3'-UTRs of PCGs. Lack of gut microbiome profoundly increased the percentage of PBDE-regulated lncRNAs mapped to the 3'-UTRs of PCGs, suggesting the potential involvement of lncRNAs in increasing the translational efficiency of PCGs by preventing miRNA-3'-UTR binding, as a compensatory mechanism following toxic exposure to PBDEs. Pathway analysis of PCGs paired with lncRNAs revealed that in CV mice, BDE-47 regulated nucleic acid and retinol metabolism, as well as circadian rhythm; whereas BDE-99 regulated fatty acid metabolism. In GF mice, BDE-47 differentially regulated 19 lncRNA-PCG pairs that were associated with glutathione conjugation and transcriptional regulation. In contrast, BDE-99 up-regulated the xenobiotic-metabolizing Cyp3a genes, but down-regulated the fatty acid-metabolizing Cyp4 genes. Taken together, the present study reveals common and unique lncRNAs and PCG targets of PBDEs in mouse liver, and is among the first to show that lack of gut microbiome sensitizes the liver to toxic exposure of BDE-99 but not BDE-47. Therefore, lncRNAs may serve as specific biomarkers that differentiate various PBDE congeners as well as environmental chemical-mediated dysbiosis. Coordinate regulation of PCG-lncRNA pairs may serve as a more efficient molecular mechanism to combat against xenobiotic insult, and especially during dysbiosis-induced increase in the internal dose of toxicants.

Pulmonary Arterial Hypertension Affects the Rat Gut Microbiome

We have analysed whether pulmonary arterial hypertension (PAH) alters the rat faecal microbiota. Wistar rats were injected with the VEGF receptor antagonist SU5416 (20 mg/kg s.c.) and followed for 2 weeks kept in hypoxia (10% O₂, PAH) or injected with vehicle and kept in normoxia (controls). Faecal samples were obtained and microbiome composition was determined by 16S rRNA gene sequencing and bioinformatic analysis. No effect of PAH on the global microbiome was found (α- or β-diversity). However, PAH-exposed rats showed gut dysbiosis as indicated by a taxonomy-based analysis. Specifically, PAH rats had a three-fold increase in Firmicutes-to-Bacteroidetes ratio. Within the Firmicutes phylum, there were no large changes in the relative abundance of the bacterial families in PAH. Among Bacteroidetes, all families were less abundant in PAH. A clear separation was observed between the control and PAH clusters based on short chain fatty acid producing bacterial genera. Moreover, acetate was reduced in the serum of PAH rats. In conclusion, faecal microbiota composition is altered as a result of PAH. This misbalanced bacterial ecosystem might in turn play a pathophysiological role in PAH by altering the immunologic, hormonal and metabolic homeostasis.

PBDEs Altered Gut Microbiome and Bile Acid Homeostasis in Male C57BL/6 Mice

Polybrominated diphenyl ethers (PBDEs) are persistent environmental contaminants with well characterized toxicities in host organs. Gut microbiome is increasingly recognized as an important regulator of xenobiotic biotransformation; however, little is known about its interactions with PBDEs. Primary bile acids (BAs) are metabolized by the gut microbiome into more lipophilic secondary BAs that may be absorbed and interact with certain host receptors. The goal of this study was to test our hypothesis that PBDEs cause dysbiosis and aberrant regulation of BA homeostasis. Nine-week-old male C57BL/6 conventional (CV) and germ-free (GF) mice were orally gavaged with corn oil (10 mg/kg), BDE-47 (100 μmol/kg), or BDE-99 (100 μmol/kg) once daily for 4 days (n = 3-5/group). Gut microbiome was characterized using 16S rRNA sequencing of the large intestinal content in CV mice. Both BDE-47 and BDE-99 profoundly decreased the alpha diversity of gut microbiome and differentially regulated 45 bacterial species. Both PBDE congeners increased Akkermansia muciniphila and Erysipelotrichaceae Allobaculum spp., which have been reported to have anti-inflammatory and antiobesity functions. Targeted metabolomics of 56 BAs was conducted in serum, liver, and small and large intestinal content of CV and GF mice. BDE-99 increased many unconjugated BAs in multiple biocompartments in a gut microbiota-dependent manner. This correlated with an increase in microbial 7α-dehydroxylation enzymes for secondary BA synthesis and increased expression of host intestinal transporters for BA absorption. Targeted proteomics showed that PBDEs downregulated host BA-synthesizing enzymes and transporters in livers of CV but not GF mice. In conclusion, there is a novel interaction between PBDEs and the endogenous BA-signaling through modification of the "gut-liver axis".

RNA-Seq Profiling of Intestinal Expression of Xenobiotic Processing Genes in Germ-Free Mice

Intestinal bacteria can affect xenobiotic metabolism through both direct bacterial enzyme-catalyzed modification of the xenobiotics and indirect alterations of the expression of host genes. To determine how intestinal bacteria affect the expression of host xenobiotic-processing genes (XPGs), the mRNA profiles of 303 XPGs were characterized by RNA sequencing in four intestinal sections and compared with that in the liver from adult male conventional (CV) and germ-free (GF) mice. Fifty-four XPGs were not expressed in the intestine of either CV or GF mice. The GF condition altered the expression of 116 XPGs in at least one intestinal section but had no effect on 133 XPGs. Many cytochrome P450 family members such as Cyp1a, Cyp2b10, Cyp2c, and most Cyp3a members, as well as carboxylesterase (Ces) 2a were expressed lower in the intestine of GF than CV mice. In contrast, GF mice had higher intestinal expression of some phase I oxidases (alcohol dehydrogenase 1, aldehyde dehydrogenase a1l1 and 4a1, as well as flavin monooxygenase 5) and phase II conjugation enzymes (UDP-glucuronosyltransferase 1a1, and sulfotransferase 1c2, 1d1, and 2b1). Several transporters in the intestine, such as bile acid transporters (apical sodium-dependent bile acid transporter, organic solute transporter α and β), peptide transporter 1, and multidrug and toxin extrusion protein 1, exhibited higher expression in GF mice. In conclusion, lack of intestinal bacteria alters the expression of a large number of XPGs in the host intestine, some of which are section specific. Cyp3a is downregulated in both the liver and intestine of GF mice, which probably contributes to altered xenobiotic metabolism.