Hepatic cytochrome P450 8B1 and cholic acid potentiate intestinal epithelial injury in colitis by suppressing intestinal stem cell renewal

Elucidating the hepatoprotective mechanisms of cholic acid against CCl4-Induced acute liver injury: A transcriptomic and metabolomic study

ETHNOPHARMACOLOGICAL RELEVANCE

Cholic acid (CA) is one of the main active ingredients in Calculus Bovis, a traditional Chinese medicine, which helps to regulate the heart and liver meridians, clearing the heart, opening the mouth, cooling the liver and calming the wind. However, the molecular mechanism of its liver protective effect is still unclear.

AIM OF THE STUDY

Growing attention has been directed towards traditional Chinese medicine (TCM), particularly Calculus Bovis, as a potential solution for liver protection. Despite this interest, a comprehensive understanding of its hepatoprotective mechanisms remains lacking. This research seeks to explore the potential protective properties of cholic acid (CA) against CCl4-induced acute liver injury (ALI) in mice, while also examining the mechanisms involved.

MATERIALS AND METHODS

In the experiment, a mouse model was employed to ALI using CCl4, and the potential therapeutic effects of orally administered CA at varying doses (15, 30, and 60 mg/kg) were assessed. The study employed a multi-faceted approach, integrating liver transcriptomics with serum metabolomics, and conducting thorough analyses of serum biochemical markers and liver histopathological sections.

RESULTS

Oral CA administration markedly reduced the organ indices of the liver, spleen, and thymus in comparison with the model group. It also elevated the expression of superoxide dismutase (SOD) in serum while diminishing the concentrations of ALT, AST, MDA, IL-6, and TNF-α. Moreover, CA ameliorated the pathological damage induced by CCl4. Integrated metabolomic and transcriptomic analyses indicated that the hepatoprotective action of CA on ALI is mediated through the modulation of lipid metabolic pathways-specifically, metabolisms of glycerophospholipid, arachidonic acid, as well as linoleic acid-and by altering the expression of genes such as Ptgr1, PLpp1, Tbxas1, and Cyp2c37.

CONCLUSIONS

The current investigation offers insights into the hepatoprotective mechanisms by which CA mitigates ALI caused by CCl4 exposure, thus supporting the further evaluation and development of CA-based therapeutics for ALI.

Enterococcus-derived tyramine hijacks α2A-adrenergic receptor in intestinal stem cells to exacerbate colitis

Inflammatory bowel disease (IBD) is characterized by dysbiosis of the gut microbiota and dysfunction of intestinal stem cells (ISCs). However, the direct interactions between IBD microbial factors and ISCs are undescribed. Here, we identify α2A-adrenergic receptor (ADRA2A) as a highly expressed GPCR in ISCs. Through PRESTO-Tango screening, we demonstrate that tyramine, primarily produced by Enterococcus via tyrosine decarboxylase (tyrDC), serves as a microbial ligand for ADRA2A. Using an engineered tyrDC-deficient Enterococcus faecalis strain and intestinal epithelial cell-specific Adra2a knockout mice, we show that Enterococcus-derived tyramine suppresses ISC proliferation, thereby impairing epithelial regeneration and exacerbating DSS-induced colitis through ADRA2A. Importantly, blocking the axis with an ADRA2A antagonist, yohimbine, disrupts tyramine-mediated suppression on ISCs and alleviates colitis. Our findings highlight a microbial ligand-GPCR pair in ISCs, revealing a causal link between microbial regulation of ISCs and colitis exacerbation and yielding a targeted therapeutic approach to restore ISC function in colitis.

Nutrient metabolism in regulating intestinal stem cell homeostasis

Intestinal stem cells (ISCs) are known for their remarkable proliferative capacity, making them one of the most active cell populations in the body. However, a high turnover rate of intestinal epithelium raises the likelihood of dysregulated homeostasis, which is known to cause various diseases, including cancer. Maintaining precise control over the homeostasis of ISCs is crucial to preserve the intestinal epithelium's integrity during homeostasis or stressed conditions. Recent research has indicated that nutrients and metabolic pathways can extensively modulate the fate of ISCs. This review will explore recent findings concerning the influence of various nutrients, including lipids, carbohydrates, and vitamin D, on the delicate balance between ISC proliferation and differentiation.

Gut-liver axis: Recent concepts in pathophysiology in alcohol-associated liver disease

The growing recognition of the role of the gut microbiome's impact on alcohol-associated diseases, especially in alcohol-associated liver disease, emphasizes the need to understand molecular mechanisms involved in governing organ-organ communication to identify novel avenues to combat alcohol-associated diseases. The gut-liver axis refers to the bidirectional communication and interaction between the gut and the liver. Intestinal microbiota plays a pivotal role in maintaining homeostasis within the gut-liver axis, and this axis plays a significant role in alcohol-associated liver disease. The intricate communication between intestine and liver involves communication between multiple cellular components in each organ that enable them to carry out their physiological functions. In this review, we focus on novel approaches to understanding how chronic alcohol exposure impacts the microbiome and individual cells within the liver and intestine, as well as the impact of ethanol on the molecular machinery required for intraorgan and interorgan communication.

Effects of acetyl groups on the prebiotic properties of glucomannan extracted from Artemisia sphaerocephala Krasch seeds

This study explores the structural modification of glucomannan extracted from Artemisia sphaerocephala Krasch seeds (60S) to assess the impact of acetyl groups on its prebiotic characteristics. The structural changes were examined, with a focus on the degree of acetyl group substitution (DS). Both deacetylation and acetylation had limited influence on the molecular properties of 60S. Despite these modifications, the apparent viscosity of all samples remained consistently low. In vitro fermentation experiments revealed that Escherichia-Shigella decreased as DS increased, while Bacteroides ovatus was enriched. Acetylation had no significant impact on the utilization rate of 60S but led to a reduction in the production of propionic acid. Furthermore, untargeted metabolomics analysis confirmed the changes in propionic acid levels. Notably, metabolites such as N-acetyl-L-tyrosine, γ-muricholic acid, and taurocholate were upregulated by acetylated derivatives. Overall, acetyl groups are speculated to play a pivotal role in the prebiotic properties of 60S.

Exploring Advanced Therapies for Primary Biliary Cholangitis: Insights from the Gut Microbiota-Bile Acid-Immunity Network

Primary biliary cholangitis (PBC) is a cholestatic liver disease characterized by immune-mediated injury to small bile ducts. Although PBC is an autoimmune disease, the effectiveness of conventional immunosuppressive therapy is disappointing. Nearly 40% of PBC patients do not respond to the first-line drug UDCA. Without appropriate intervention, PBC patients eventually progress to liver cirrhosis and even death. There is an urgent need to develop new therapies. The gut-liver axis emphasizes the interconnection between the gut and the liver, and evidence is increasing that gut microbiota and bile acids play an important role in the pathogenesis of cholestatic diseases. Dysbiosis of gut microbiota, imbalance of bile acids, and immune-mediated bile duct injury constitute the triad of pathophysiology in PBC. Autoimmune cholangitis has the potential to be improved through immune system modulation. Considering the failure of conventional immunotherapies and the involvement of gut microbiota and bile acids in the pathogenesis, targeting immune factors associated with them, such as bile acid receptors, microbial-derived molecules, and related specific immune cells, may offer breakthroughs. Understanding the gut microbiota-bile acid network and related immune dysfunctions in PBC provides a new perspective on therapeutic strategies. Therefore, we summarize the latest advances in research of gut microbiota and bile acids in PBC and, for the first time, explore the possibility of related immune factors as novel immunotherapy targets. This article discusses potential therapeutic approaches focusing on regulating gut microbiota, maintaining bile acid homeostasis, their interactions, and related immune factors.

Discovery and Optimization of Novel Nonbile Acid FXR Agonists as Preclinical Candidates for the Treatment of Inflammatory Bowel Disease

Inflammatory bowel disease (IBD) is a multifactorial chronic inflammation of the intestine and has become a global public health concern. A farnesoid X receptor (FXR) was recently reported to play a key role in hepatic-intestinal circulation, intestinal metabolism, immunity, and microbial regulation, and thus, it becomes a promising therapeutic target for IBD. In this study, we identified a series of nonbile acid FXR agonists, in which 33 novel compounds were designed and synthesized by the structure-based drug design strategy from our previously identified hit compound. Compound 33 exhibited a potent FXR agonistic activity, high intestinal distribution, good anti-inflammatory activity, and the ability to repair the colon epithelium in a DSS-induced acute enteritis model. Based on the results of RNA-seq analysis, we further investigated the therapeutic potential of the combination of compound 33 with 5-ASA. Overall, the results indicated that compound 33 is a promising drug candidate for IBD treatment.

Hypoxic preconditioning accelerates the healing of ischemic intestinal injury by activating HIF-1α/PPARα pathway-mediated fatty acid oxidation

Hypoxic preconditioning (HPC) has been shown to improve organ tolerance to subsequent severe hypoxia or ischemia. However, its impact on intestinal ischemic injury has not been well studied. In this study, we evaluated the effects of HPC on intestinal ischemia in rats. Intestinal rehabilitation, levels of fatty acid oxidation (FAO) by-products, intestinal stem cells (ISCs), levels of hypoxia-inducible factor 1 subunit α (HIF-1α) and its downstream genes such as peroxisome proliferator-activated receptor α (PPARα), and carnitine palmitoyltransferase 1a (CPT1A) were assessed at distinct time intervals following intestinal ischemia with or without the interference of HIF-1α. Our data showed that HPC facilitates the restoration of the intestinal structure and enhances the FAO, by boosting intestinal stem cells. Additionally, HIF-1α, PPARα, and CPT1A mRNA and their protein levels were generally up-regulated in the small intestine of HPC rats as compared to the control group. Our vitro experiment also shows low-oxygen induces highly levels of HIF-1α and its downstream genes, with a concurrent increase in FAO products in IEC-6 cells. Furthermore, the above phenomenon could be reversed by silencing HIF-1α. In conclusion, we hypothesize that HPC can stimulate the activation of intestinal stem cells via HIF-1α/PPARα pathway-mediated FAO, thereby accelerating the healing process post ischemic intestinal injury.

Gut microbiome-metabolites axis: A friend or foe to colorectal cancer progression

An expanding corpus of research robustly substantiates the complex interrelation between gut microbiota and the onset, progression, and metastasis of colorectal cancer. Investigations in both animal models and human subjects have consistently underscored the role of gut bacteria in a variety of metabolic activities, driven by dietary intake. These activities include amino acid metabolism, carbohydrate fermentation, and the generation and regulation of bile acids. These metabolic derivatives, in turn, have been identified as significant contributors to the progression of colorectal cancer. This thorough review meticulously explores the dynamic interaction between gut bacteria and metabolites derived from the breakdown of amino acids, fatty acid metabolism, and bile acid synthesis. Notably, bile acids have been recognized for their potential carcinogenic properties, which may expedite tumor development. Extensive research has revealed a reciprocal influence of gut microbiota on the intricate spectrum of colorectal cancer pathologies. Furthermore, strategies to modulate gut microbiota, such as dietary modifications or probiotic supplementation, may offer promising avenues for both the prevention and adjunctive treatment of colorectal cancer. Nevertheless, additional research is imperative to corroborate these findings and enhance our comprehension of the underlying mechanisms in colorectal cancer development.

The role of bile acids in human aging

Bile acids are recognized as important signaling molecules that enable fine-tuned inter-communication from the liver, through the intestine, to virtually any organ, thus encouraging their pleiotropic physiological effects. Aging is a complex natural process defined as a progressive decline in cellular and organismal functions. A causal link between bile acids and the aging process is emerging. However, there are gaps in our understanding of the molecular mechanisms and precise targets responsible for the alteration of bile acid profiles and their role in the aging process. Intestinal barrier dysfunction leads to endotoxemia, systemic inflammation, insulin resistance, diabetes, lipid accumulation, obesity and fatty liver diseases, and health decline and death. In fact, intestinal barrier dysfunction is suggested to be an evolutionarily conserved hallmark of aging. Bile acids may modulate the aging process by regulating intestinal barrier integrity.

Characterization of the chemical composition of different parts of Dolichos lablab L. and revelation of its anti-ulcerative colitis effects by modulating the gut microbiota and host metabolism

ETHNOPHARMACOLOGICAL RELEVANCE

Ulcerative colitis (UC) is a non-specific inflammatory disease characterized by long duration and easy relapse. Dolichos lablab L. (DLL) belongs to the family Fabaceae, was listed in a famous Chinese medical classic, Compendium of Materia Medic, and described as possessing features that invigorate the spleen, alleviate dampness, provide diarrhea relief, and other effects. The DLL-dried white mature seeds (DS) and dried flower (DF), which hold significant medicinal value in China, were used in clinical prescriptions to prevent and treat UC. DS and DF have appeared in different editions of the Pharmacopoeia of the People's Republic of China from 1977 to 2020. However, their chemical composition, pharmacological effects, and mechanism of treating UC are unclear.

AIM OF THE STUDY

This study aimed to characterize the chemical composition of different parts of DLL (seeds and flowers), further explore their pharmacological effects, and elaborate its underlying mechanism of treating UC.

METHODS

The chemical composition of DS and DF crude polysaccharides (DSP and DFP) and ethanolic extracts (DSE and DFE) were characterized by high-performance anion-exchange chromatography (HPAEC), ultra-high performance liquid chromatography-mass spectrometry (UHPLC-MS), and gas chromatography-mass spectrometry (GC-MS). Then, based on the acute UC mice model, the pharmacodynamic effects were investigated by Western blotting, ELISA, and other methods. Finally, the 16S rRNA gene sequencing and metabonomic analysis were used to explore the regulatory effects of DS and DF on intestinal microbiota and host metabolism.

RESULTS

DSE and DFE inhibited the oxidative stress response, reducing proinflammatory factor production and maintaining intestinal barrier integrity in UC mice. The 16S rRNA gene sequencing and metabonomic analysis revealed that DS and DF treated UC by regulating the intestinal microbiota structure and reversing the abnormal metabolism of the host.

CONCLUSION

This study suggested that different parts of DLL (flowers and seeds) may be potential medicines for treating UC, which exert their therapeutic effects through various active ingredients and might contribute significantly to reducing the economic pressures and challenges of UC treatment worldwide.

Marine sponge-derived alkaloid ameliorates DSS-induced IBD via inhibiting IL-6 expression through modulating JAK2-STAT3-SOCS3 pathway

Cyanogramide (AC14), a novel alkaloid, isolated from the fermentation broth of the marine-derived Actinoalloteichus cyanogriseus. However, the exact role of AC14 in inflammatory bowel disease (IBD) is poorly understood. Our results demonstrated that AC14 exhibited significant inhibition of IL-6 release in THP-1 cells and a "Caco-2/THP-1" coculture system after stimulation with LPS for 24 h. However, no significant effect on TNF-α production was observed. Furthermore, in 2.5 % DSS-induced colitis mice, AC14 treatment led to improvement in body weight, colon length, and intestine mucosal barrier integrity. AC14 also suppressed serum IL-6 production and modulated dysregulated microbiota in the mice. Mechanistically, AC14 was found to inhibit the phosphorylation of Janus kinase (JAK) 2 and signal transducers and activators of transcription (STAT) 3, while simultaneously elevating the expression of suppressor of cytokine signaling (SOCS) 3, both in vivo and in vitro. These findings suggest that AC14 exerts its suppressive effects on IL-6 production in DSS-induced IBD mice through the JAK2-STAT3-SOCS3 signaling pathway. Our study highlights the potential of AC14 as a therapeutic agent for the treatment of IBD.

Border Control: The Role of the Microbiome in Regulating Epithelial Barrier Function

The gut mucosal epithelium is one of the largest organs in the body and plays a critical role in regulating the crosstalk between the resident microbiome and the host. To this effect, the tight control of what is permitted through this barrier is of high importance. There should be restricted passage of harmful microorganisms and antigens while at the same time allowing the absorption of nutrients and water. An increased gut permeability, or "leaky gut", has been associated with a variety of diseases ranging from infections, metabolic diseases, and inflammatory and autoimmune diseases to neurological conditions. Several factors can affect gut permeability, including cytokines, dietary components, and the gut microbiome. Here, we discuss how the gut microbiome impacts the permeability of the gut epithelial barrier and how this can be harnessed for therapeutic purposes.

Comparative secretome metabolic dysregulation by six engineered dietary nanoparticles (EDNs) on the simulated gut microbiota

The potential use of engineered dietary nanoparticles (EDNs) in diet has been increasing and poses a risk of exposure. The effect of EDNs on gut bacterial metabolism remains largely unknown. In this study, liquid chromatography-mass spectrometry (LC-MS) based metabolomics was used to reveal significantly altered metabolites and metabolic pathways in the secretome of simulated gut microbiome exposed to six different types of EDNs (Chitosan, cellulose nanocrystals (CNC), cellulose nanofibrils (CNF) and polylactic-co-glycolic acid (PLGA); two inorganic EDNs including TiO2 and SiO2) at two dietary doses. We demonstrated that all six EDNs can alter the composition in the secretome with distinct patterns. Chitosan, followed by PLGA and SiO2, has shown the highest potency in inducing the secretome change with major pathways in tryptophan and indole metabolism, bile acid metabolism, tyrosine and phenol metabolism. Metabolomic alterations with clear dose response were observed in most EDNs. Overall, phenylalanine has been shown as the most sensitive metabolites, followed by bile acids such as chenodeoxycholic acid and cholic acid. Those metabolites might be served as the representative metabolites for the EDNs-gut bacteria interaction. Collectively, our studies have demonstrated the sensitivity and feasibility of using metabolomic signatures to understand and predict EDNs-gut microbiome interaction.

Psychological stress-induced microbial metabolite indole-3-acetate disrupts intestinal cell lineage commitment

The brain and gut are intricately connected and respond to various stimuli. Stress-induced brain-gut communication is implicated in the pathogenesis and relapse of gut disorders. The mechanism that relays psychological stress to the intestinal epithelium, resulting in maladaptation, remains poorly understood. Here, we describe a stress-responsive brain-to-gut metabolic axis that impairs intestinal stem cell (ISC) lineage commitment. Psychological stress-triggered sympathetic output enriches gut commensal Lactobacillus murinus, increasing the production of indole-3-acetate (IAA), which contributes to a transferrable loss of intestinal secretory cells. Bacterial IAA disrupts ISC mitochondrial bioenergetics and thereby prevents secretory lineage commitment in a cell-intrinsic manner. Oral α-ketoglutarate supplementation bolsters ISC differentiation and confers resilience to stress-triggered intestinal epithelial injury. We confirm that fecal IAA is higher in patients with mental distress and is correlated with gut dysfunction. These findings uncover a microbe-mediated brain-gut pathway that could be therapeutically targeted for stress-driven gut-brain comorbidities.

Investigating the shared genetic architecture between primary sclerosing cholangitis and inflammatory bowel diseases: a Mendelian randomization study

BACKGROUND

Several studies have found that primary sclerosing cholangitis (PSC) and inflammatory bowel disease (IBD) are closely associated. However, the direction and causality of their interactions remain unclear. Thus, this study employs Mendelian Randomization to explore whether there are causal associations of genetically predicted PSC with IBD.

METHODS

Genetic variants associated with the genome-wide association study (GWAS) of PSC were used as instrumental variables. The statistics for IBD, including ulcerative colitis (UC), and Crohn's disease (CD) were derived from GWAS. Then, five methods were used to estimate the effects of genetically predicted PSC on IBD, including MR Egger, Weighted median (WM), Inverse variance weighted (IVW), Simple mode, and Weighted mode. Last, we also evaluated the pleiotropic effects, heterogeneity, and a leave-one-out sensitivity analysis that drives causal associations to confirm the validity of the analysis.

RESULTS

Genetically predicted PSC was significantly associated with an increased risk of UC, according to the study (odds ratio [OR] IVW= 1.0014, P<0.05). However, none of the MR methods found significant causal evidence of genetically predicted PSC in CD (All P>0.05). The sensitivity analysis results showed that the causal effect estimations of genetically predicted PSC on IBD were robust, and there was no horizontal pleiotropy or statistical heterogeneity.

CONCLUSIONS

Our study corroborated a causal association between genetically predicted PSC and UC but did not between genetically predicted PSC and CD. Then, we identification of shared SNPs for PSC and UC, including rs3184504, rs9858213, rs725613, rs10909839, and rs4147359. More animal experiments and clinical observational studies are required to further clarify the underlying mechanisms of PSC and IBD.

A gut microbiota-bile acid axis promotes intestinal homeostasis upon aspirin-mediated damage

Aspirin-related gastrointestinal damage is of growing concern. Aspirin use modulates the gut microbiota and associated metabolites, such as bile acids (BAs), but how this impacts intestinal homeostasis remains unclear. Herein, using clinical cohorts and aspirin-treated mice, we identified an intestinal microbe, Parabacteroides goldsteinii, whose growth is suppressed by aspirin. Mice supplemented with P. goldsteinii or its BA metabolite, 7-keto-lithocholic acid (7-keto-LCA), showed reduced aspirin-mediated damage of the intestinal niche and gut barrier, effects that were lost with a P. goldsteinii hdhA mutant unable to generate 7-keto-LCA. Specifically, 7-keto-LCA promotes repair of the intestinal epithelium by suppressing signaling by the intestinal BA receptor, farnesoid X receptor (FXR). 7-Keto-LCA was confirmed to be an FXR antagonist that facilitates Wnt signaling and thus self-renewal of intestinal stem cells. These results reveal the impact of oral aspirin on the gut microbiota and intestinal BA metabolism that in turn modulates gastrointestinal homeostasis.

Recovering intestinal redox homeostasis to resolve systemic inflammation for preventing remote myocardial injury by oral fullerenes

The unbalanced immune state is the dominant feature of myocardial injury. However, the complicated pathology of cardiovascular diseases and the unique structure of cardiac tissue lead to challenges for effective immunoregulation therapy. Here, we exploited oral fullerene nanoscavenger (OFNS) to maintain intestinal redox homeostasis to resolve systemic inflammation for effectively preventing distal myocardial injury through bidirectional communication along the heart-gut immune axis. Observably, OFNS regulated redox microenvironment to repair cellular injury and reduce inflammation in vitro. Subsequently, OFNS prevented myocardial injury by regulating intestinal redox homeostasis and recovering epithelium barrier integrity in vivo. Based on the profiles of transcriptomics and proteomics, we demonstrated that OFNS balanced intestinal and systemic immune homeostasis for remote cardioprotection. Of note, we applied this principle to intervene myocardial infarction in mice and mini-pigs. These findings highlight that locally addressing intestinal redox to inhibit systemic inflammation could be a potent strategy for resolving remote tissue injury.

Acid-base transformative HADLA micelles alleviate colitis by restoring adaptive immunity and gut microbiome

Inflammatory bowel disease (IBD) is a worldwide public health issue with an increasing number of patients annually. However, there is no curative drug for IBD, and the present medication for IBD generally focuses on suppressing hyperactive immune responses, which can only delay disease progression but inevitably induce off-target side effects, including infections and cancers. Herein, late-model orally administered nanotherapeutic micelles (HADLA) were developed based on a conjugate of hyaluronic acid (HA) and dehydrolithocholic acid (DLA), which was simple to achieve and obtained satisfactory therapeutic efficacy in a murine colitis model with a full safety profile. HADLA is capable of targeting inflammatory colon tissues, restoring intestinal barrier function and reducing intestinal epithelial cell death. Moreover, it modulates the adaptive immune system by inhibiting the activation of pathogenic T helper 17 (Th17) cells, and it exhibits more remarkable effects in preventing colitis than DLA alone. Finally, HADLA exhibits a remarkable ability to modulate dysregulated gut microbiomes by increasing beneficial probiotics and decreasing pathogenic bacteria, such as Turicibacter. Compared with the current systemic or subcutaneous administration of biologics, this study opens new avenues in the oral delivery of immune-modulating nanomedicine and introduces DLA as a new medication for IBD treatment.

Microbial sensing in the intestine

The gut microbiota plays a key role in host health and disease, particularly through their interactions with the immune system. Intestinal homeostasis is dependent on the symbiotic relationships between the host and the diverse gut microbiota, which is influenced by the highly co-evolved immune-microbiota interactions. The first step of the interaction between the host and the gut microbiota is the sensing of the gut microbes by the host immune system. In this review, we describe the cells of the host immune system and the proteins that sense the components and metabolites of the gut microbes. We further highlight the essential roles of pattern recognition receptors (PRRs), the G protein-coupled receptors (GPCRs), aryl hydrocarbon receptor (AHR) and the nuclear receptors expressed in the intestinal epithelial cells (IECs) and the intestine-resident immune cells. We also discuss the mechanisms by which the disruption of microbial sensing because of genetic or environmental factors causes human diseases such as the inflammatory bowel disease (IBD).

Amelioration Effects and Regulatory Mechanisms of Different Tea Active Ingredients on DSS-Induced Colitis

The potential biological function of tea and its active components on colitis has attracted wide attention. In this study, different tea active ingredients including tea polyphenols (TPPs), tea polysaccharides (TPSs), theabrownin (TB), and theanine (TA) have been compared in the intervention of dextran sulfate sodium (DSS)-induced colitis in mice. Specifically, TPP showed the greatest effect on colitis since it reduced 60.87% of disease activity index (DAI) compared to that of the DSS-induced colitis group, followed by the reduction of 39.13% of TPS and 28.26% of TB on DAI, whereas there was no obvious alleviative effect of TA on colitis. TPP, TPS, and TB could regulate the composition and abundance of gut microbiota to increase the content of short-chain fatty acids (SCFAs) and enhance intestinal barrier function. Further evidence was observed that TPP and TPS regulated the activation of Nrf2/ARE and the TLR4/MyD88/NF-κB P65 pathway to alleviate the colitis. Results of cell experiments demonstrated that TPP showed the greatest antiapoptosis and mitochondrial function protective capability among the tea ingredients via inhibiting the Cytc/Cleaved-caspase-3 signaling pathway. In summary, the superior anticolitis activity of TPP compared to TPS and TB is primarily attributed to its unique upregulation of the abundance of Akkermansia and its ability to regulate the mitochondrial function.

Effect of gut flora mediated-bile acid metabolism on intestinal immune microenvironment

According to reports, gut microbiota and metabolites regulate the intestinal immune microenvironment. In recent years, an increasing number of studies reported that bile acids (BAs) of intestinal flora origin affect T helper cells and regulatory T cells (Treg cells). Th17 cells play a pro-inflammatory role and Treg cells usually act in an immunosuppressive role. In this review, we emphatically summarised the influence and corresponding mechanism of different configurations of lithocholic acid (LCA) and deoxycholic acid (DCA) on intestinal Th17 cells, Treg cells and intestinal immune microenvironment. The regulation of BAs receptors G protein-coupled bile acid receptor 1 (GPBAR1/TGR5) and farnesoid X receptor (FXR) on immune cells and intestinal environment are elaborated. Furthermore, the potential clinical applications above were also concluded in three aspects. The above will help researchers better understand the effects of gut flora on the intestinal immune microenvironment via BAs and contribute to the development of new targeted drugs.

Forsythia suspensa (Thunb.) Vahl extract ameliorates ulcerative colitis via inhibiting NLRP3 inflammasome activation through the TLR4/MyD88/NF-κB pathway

BACKGROUND

Ulcerative colitis (UC), a chronic inflammatory disease, is caused by abnormal immune system reactions resulting in inflammation and ulcers in the large intestine. Phillygenin (PHI) is a natural compound found in Forsythia suspensa (Thunb.) Vahl, which is known for its antipyretic, anti-inflammatory, antiobesity, and other biological activities. However, the therapeutic role and molecular mechanisms of PHI on UC are still insufficiently researched.

METHODS

In this study, dextran sulfate sodium (DSS) and 2.5% 2,4,6-trinitro-Benzenesulfonic acid (TNBS)-induced acute UC were used to investigate the therapeutic effects of PHI. We evaluated the effects of PHI on disease activity index (DAI), body weight, mortality, intestinal mucosal barrier, cytokine secretion, and macrophage infiltration into colon tissue using various techniques such as flow cytometry, immunofluorescence, enzyme-linked immunosorbent assay (ELISA), RT-qPCR, and Western blot analysis.

RESULTS

Our findings revealed that PHI has therapeutic properties in UC treatment. PHI was able to maintain body weight, reduce DAI and mortality, restore the intestinal mucosal barrier, and inhibit cytokine secretion. Flow cytometry assay and immunofluorescence indicated that PHI reduces macrophage infiltration into colon tissue. Mechanistically, PHI may exert anti-inflammatory effects by downregulating the TLR4/MyD88/NF-κB pathway and inhibiting the activation of NLRP3 inflammasome.

CONCLUSION

In conclusion, PHI possesses significant anti-inflammatory properties and is expected to be a potential drug for UC treatment. Our study delves into the underlying mechanisms of PHI therapy and highlights the potential for further research in developing PHI-based treatments for UC.

RING finger protein 13 protects against nonalcoholic steatohepatitis by targeting STING-relayed signaling pathways

Nonalcoholic fatty liver disease (NAFLD) is the most common liver disorder worldwide. Recent studies show that innate immunity-related signaling pathways fuel NAFLD progression. This study aims to identify potent regulators of innate immunity during NAFLD progression. To this end, a phenotype-based high-content screening is performed, and RING finger protein 13 (RNF13) is identified as an effective inhibitor of lipid accumulation in vitro. In vivo gain- and loss-of-function assays are conducted to investigate the role of RNF13 in NAFLD. Transcriptome sequencing and immunoprecipitation-mass spectrometry are performed to explore the underlying mechanisms. We reveal that RNF13 protein is upregulated in the liver of individuals with NASH. Rnf13 knockout in hepatocytes exacerbate insulin resistance, steatosis, inflammation, cell injury and fibrosis in the liver of diet-induced mice, which can be alleviated by Rnf13 overexpression. Mechanically, RNF13 facilitates the proteasomal degradation of stimulator of interferon genes protein (STING) in a ubiquitination-dependent way. This study provides a promising innate immunity-related target for NAFLD treatment.

Farnesoid X receptor: From Structure to Function and Its Pharmacology in Liver Fibrosis

The farnesoid X receptor (FXR), a ligand-activated transcription factor, plays a crucial role in regulating bile acid metabolism within the enterohepatic circulation. Beyond its involvement in metabolic disorders and immune imbalances affecting various tissues, FXR is implicated in microbiota modulation, gut- to-brain communication, and liver disease. The liver, as a pivotal metabolic and detoxification organ, is susceptible to damage from factors such as alcohol, viruses, drugs, and high-fat diets. Chronic or recurrent liver injury can culminate in liver fibrosis, which, if left untreated, may progress to cirrhosis and even liver cancer, posing significant health risks. However, therapeutic options for liver fibrosis remain limited in terms of FDA- approved drugs. Recent insights into the structure of FXR, coupled with animal and clinical investigations, have shed light on its potential pharmacological role in hepatic fibrosis. Progress has been achieved in both fundamental research and clinical applications. This review critically examines recent advancements in FXR research, highlighting challenges and potential mechanisms underlying its role in liver fibrosis treatment.

Slowed Intestinal Transit Induced by Less Mucus in Intestinal Goblet Cell Piezo1-Deficient Mice through Impaired Epithelial Homeostasis

Mucus secreted by goblet cells (GCs) may play an important role in intestinal transit function. Our previous study found that Piezo1 protein is essential for GC function; however, the effect of GC Piezo1 on intestinal transit function is unclear. Our study aimed to investigate the effect of Piezo1 in GCs on intestinal transit and the potential mechanism. We compared intestinal mucus, fecal form, intestinal transit time, intestinal epithelial cell composition, and stem cell function in WT and GC-specific Piezo1-deficient (Piezo1ΔGC) mice. Our results revealed a correlation between mucus and intestinal transit: the less mucus there was, the slower the intestinal transit. Piezo1 deficiency in GCs led to decreased mucus synthesis and also disrupted the ecological niche of colon stem cells (CSCs). Through organoid culture, we found that the capacity of proliferation and differentiation in Piezo1ΔGC mouse CSCs was significantly decreased, which also led to a reduced source of GCs. Further studies found that the reduced Wnt and Notch signals in colon crypts might be the potential mechanism. These results indicated the importance of GC Piezo1 in intestinal transit function, which acts by maintaining the homeostasis of intestinal epithelial cells and mucus.

The metabolomic plasma profile of patients with Duchenne muscular dystrophy: providing new evidence for its pathogenesis

BACKGROUND

Duchenne muscular dystrophy (DMD) is a fatal genetic muscle-wasting disease that affects 1 in 5000 male births with no current cure. Despite great progress has been made in the research of DMD, its underlying pathological mechanism based on the metabolomics is still worthy of further study. Therefore, it is necessary to gain a deeper understanding of the mechanisms or pathogenesis underlying DMD, which may reveal potential therapeutic targets and/or biomarkers.

RESULTS

Plasma samples from 42 patients with DMD from a natural history study and 40 age-matched healthy volunteers were subjected to a liquid chromatography-mass spectrometry-based non-targeted metabolomics approach. Acquired metabolic data were evaluated by principal component analysis, partial least squares-discriminant analysis, and metabolic pathway analysis to explore distinctive metabolic patterns in patients with DMD. Differentially expressed metabolites were identified using publicly available and integrated databases. By comparing the DMD and healthy control groups, 25 differential metabolites were detected, including amino acids, unsaturated fatty acids, carnitine, lipids, and metabolites related to the gut microbiota. Correspondingly, linoleic acid metabolism, D-glutamine and D-glutamate metabolism, glycerophospholipid metabolism, and alanine, aspartate, and glutamate metabolism were significantly altered in patients with DMD, compared with those of healthy volunteers.

CONCLUSIONS

Our study demonstrated the abnormal metabolism of amino acids, energy, and lipids in patients with DMD, consistent with pathological features, such as recurrent muscle necrosis and regeneration, interstitial fibrosis, and fat replacement. Additionally, we found that metabolites of intestinal flora were disordered in DMD patients, providing support for treatment of intestinal microbia disturbance in DMD diseases. Our study provides a new research strategy for understanding the pathogenesis of DMD.

Bile acids and their receptors: Potential therapeutic targets in inflammatory bowel disease

Chronic and recurrent inflammatory disorders of the gastrointestinal tract caused by a complex interplay between genetics and intestinal dysbiosis are called inflammatory bowel disease. As a result of the interaction between the liver and the gut microbiota, bile acids are an atypical class of steroids produced in mammals and traditionally known for their function in food absorption. With the development of genomics and metabolomics, more and more data suggest that the pathophysiological mechanisms of inflammatory bowel disease are regulated by bile acids and their receptors. Bile acids operate as signalling molecules by activating a variety of bile acid receptors that impact intestinal flora, epithelial barrier function, and intestinal immunology. Inflammatory bowel disease can be treated in new ways by using these potential molecules. This paper mainly discusses the increasing function of bile acids and their receptors in inflammatory bowel disease and their prospective therapeutic applications. In addition, we explore bile acid metabolism and the interaction of bile acids and the gut microbiota.

Bile Acids, Intestinal Barrier Dysfunction, and Related Diseases

The intestinal barrier is a precisely regulated semi-permeable physiological structure that absorbs nutrients and protects the internal environment from infiltration of pathological molecules and microorganisms. Bile acids are small molecules synthesized from cholesterol in the liver, secreted into the duodenum, and transformed to secondary or tertiary bile acids by the gut microbiota. Bile acids interact with bile acid receptors (BARs) or gut microbiota, which plays a key role in maintaining the homeostasis of the intestinal barrier. In this review, we summarize and discuss the recent studies on bile acid disorder associated with intestinal barrier dysfunction and related diseases. We focus on the roles of bile acids, BARs, and gut microbiota in triggering intestinal barrier dysfunction. Insights for the future prevention and treatment of intestinal barrier dysfunction and related diseases are provided.

The Effect of MSTN Mutation on Bile Acid Metabolism and Lipid Metabolism in Cattle

Myostatin (MSTN) is a negative regulator of skeletal muscle genesis during development. MSTN mutation leads to increased lean meat production and reduced fat deposition in livestock. However, the mechanism by which MSTN promotes myogenesis by regulating metabolism is not clear. In this study, we compared the metabolomics of the livers of wild-type (WT) and MSTN mutation cattle (MT), and found changes in the content and proportion of fatty acids and bile acids in MT cattle. The differential metabolites were enriched in sterol synthesis and primary bile acid synthesis. We further analyzed the expression of genes involved in the regulation of lipid and bile acid metabolism, and found that the loss of MSTN may alter lipid synthesis and bile acid metabolism. This study provides new basic data for MSTN mutations in beef cattle breeding.

Comprehensive Analysis of Microbiome, Metabolome, and Transcriptome Revealed the Mechanisms of Intestinal Injury in Rainbow Trout under Heat Stress

Global warming is one of the most common environmental challenges faced by cold-water fish farming. Intestinal barrier function, gut microbiota, and gut microbial metabolites are significantly altered under heat stress, posing serious obstacles to the healthy artificial culture of rainbow trout. However, the molecular mechanisms underlying intestinal injury in rainbow trout under heat stress remain unclear. In the present study, the optimal growth temperature for rainbow trout (16 °C) was used for the control group, and the maximum temperature tolerated by rainbow trout (24 °C) was used for the heat stress group, which was subjected to heat stress for 21 days. The mechanism of intestinal injury in rainbow trout under heat stress was explored by combining animal histology, 16S rRNA gene amplicon sequencing, ultra-high performance liquid chromatography-mass spectrometry, and transcriptome sequencing. The results showed that the antioxidant capacity of rainbow trout was enhanced under heat stress, the levels of stress-related hormones were significantly increased, and the relative expression of genes related to heat stress proteins was significantly increased, indicating that the heat stress model of rainbow trout was successfully established. Secondly, the intestinal tract of rainbow trout showed inflammatory pathological characteristics under heat stress, with increased permeability, activation of the inflammatory factor signaling pathway, and increased relative expression of inflammatory factor genes, suggesting that the intestinal barrier function was impaired. Thirdly, heat stress caused an imbalance of intestinal commensal microbiota and changes in intestinal metabolites in rainbow trout, which participated in the stress response mainly by affecting lipid metabolism and amino acid metabolism. Finally, heat stress promoted intestinal injury in rainbow trout by activating the peroxisome proliferator-activated receptor-α signaling pathway. These results not only expand the understanding of fish stress physiology and regulation mechanisms, but also provide a scientific basis for healthy artificial culture and the reduction of rainbow trout production costs.

Metabolic alterations of the gut-liver axis induced by cholic acid contribute to hepatic steatosis in rats

12α-Hydroxylated (12αOH) bile acids (BAs) selectively increase with high-fat diet intake. Dietary supplementation with cholic acid (CA) in rats is a possible strategy to reveal the causal link between 12αOH BAs and hepatic steatosis. The present study aimed to investigate the metabolic mechanism underlying the effect of 12αOH BAs on hepatic steatosis. Male WKAH rats were fed either a control (Ct) or CA-supplemented diet (0.5 g/kg). After the 12-week intervention, the CA diet elevated the 12αOH BA levels in the gut-liver axis. CA-fed rats showed greater hepatic lipid accumulation than in the Ct group, regardless of the dietary energy balance. Untargeted metabolomics suggested marked differences in the fecal metabolome of rats subjected to the CA diet compared with that of Ct, characterized by the depletion of fatty acids and enrichment of amino acids and amines. Moreover, the liver metabolome differed in the CA diet group, characterized by an alteration in redox-related pathways. The CA diet elevated nicotinamide adenine dinucleotide consumption owing to the activation of poly(ADP-ribose) polymerase 1, resulting in impaired peroxisome proliferator-activated receptor α signaling in the liver. The CA diet increased sedoheptulose 7-phosphate, and enhanced glucose-6-phosphate dehydrogenase activity, suggesting promotion of the pentose phosphate pathway that generates reducing equivalents. Integrated analysis of the gut-liver metabolomic data revealed the role of deoxycholic acid and its liver counterpart in mediating these metabolic alterations. These observations suggest that alterations in metabolites induced by 12αOH BAs in the gut-liver axis contribute to the enhancement of liver lipid accumulation.