Indole-3-Acetic Acid Alleviates Nonalcoholic Fatty Liver Disease in Mice via Attenuation of Hepatic Lipogenesis, and Oxidative and Inflammatory Stress

Advances in the acting mechanism and treatment of gut microbiota in metabolic dysfunction-associated steatotic liver disease

Metabolic Dysfunction-Associated Steatotic Liver Disease(MASLD) is increasing in prevalence worldwide and has become the greatest potential risk for cirrhosis and hepatocellular liver cancer. Currently, the role of gut microbiota in the development of MASLD has become a research hotspot. The development of MASLD can affect the homeostasis of gut microbiota, and significant changes in the composition or abundance of gut microbiota and its metabolite abnormalities can influence disease progression. The regulation of gut microbiota is an important strategy and novel target for the treatment of MASLD with good prospects. In this paper, we summarize the role of gut microbiota and its metabolites in the pathogenesis of MASLD, and describe the potential preventive and therapeutic efficacy of gut microbiota as a noninvasive marker to regulate the pathogenesis of MASLD based on the "gut-hepatic axis", which will provide new therapeutic ideas for the clinic.

Gut microbial enzymes and metabolic dysfunction-associated steatohepatitis: Function, mechanism, and therapeutic prospects

Metabolic dysfunction-associated steatotic liver disease (MASLD) is the most prevalent liver disease worldwide. The liver communicates with the intestine, in large part through the gut microbiota. Microbial enzymes are key mediators that affect the progression of MASLD and the more severe metabolic dysfunction-associated steatohepatitis (MASH). These enzymes contribute to the metabolism or biosynthesis of steroids, fatty acids, amino acids, ethanol, choline, and intestinal hormones that contribute to disease progression. Additionally, dysbiosis and functional alterations in the microbiota compromise the intestinal barrier, increasing its permeability to bacterial metabolites and liver exposure to microbial-associated molecular patterns (MAMPs), thereby exacerbating liver inflammation and fibrosis. Furthermore, functional alterations in the gut microbiota can modulate intestinal signaling pathways through metabolites or gut hormones, subsequently affecting hepatic metabolism. A deeper understanding of the roles of the gut microbiota and microbial enzymes in MASH will facilitate the development of personalized treatments targeting specific gut microbes or functional enzymes.

Bifidobacterium bifidum 1007478 derived indole-3-lactic acid alleviates NASH via an aromatic hydrocarbon receptor-dependent pathway in zebrafish

AIMS

This study investigates the potential of Bifidobacterium bifidum 1007478 (BB478) and its metabolite indole-3-lactic acid (ILA) in alleviating non-alcoholic steatohepatitis (NASH) induced by a high-fat diet (HFD) and fructose exposure.

MATERIALS AND METHODS

A zebrafish model of NASH was established by exposure to HFD and fructose. BB478 was administered, and the effects on liver lipid accumulation, oxidative stress, and inflammation were assessed. ILA production by BB478 was confirmed, and its impact on hepatic lipogenesis and inflammatory pathways was evaluated. The involvement of the aromatic hydrocarbon receptor (AhR) was also examined using an AhR inhibitor.

KEY FINDINGS

BB478 supplementation inhibited lipid accumulation in the liver, reduced triglycerides (TG) and total cholesterol (TC), and mitigated oxidative stress, as evidenced by lower levels of reactive oxygen species (ROS) and malondialdehyde (MDA). ILA, produced by BB478, could alleviate the hepatic damage and fat deposition in liver. Mechanistically, it suppressed hepatic lipogenesis by downregulating lipogenesis-related genes, including sterol response element binding protein 1 (SREBP1) and fatty acid synthase (FASN). ILA also inhibited the expression of pro-inflammatory cytokines to suppress inflammation. The therapeutic effects of ILA were reversed by the AhR inhibitor, indicating that ILA's actions are AhR-dependent.

SIGNIFICANCE

These findings reveal the potential of ILA, produced by Bifidobacterium bifidum, as a therapeutic agent for NASH. The mechanistic insights into AhR-mediated effects provide a foundation for further exploration of ILA as a novel approach for managing liver diseases.

Tryptophan Indole Derivatives: Key Players in Type 2 Diabetes Mellitus

Type 2 diabetes mellitus (T2DM) is a complex clinical syndrome characterized by insulin resistance and associated with abnormal amino acid metabolism. Tryptophan is an aromatic dietary amino acid that affects T2DM by regulating glycolipid metabolism and insulin resistance. When tryptophan reaches the intestine, it is converted by gut microbiota and tryptophanase into indole derivatives such as indoleacetic acid, indolepropionic acid, and indolealdehyde. These indole derivatives may enhance insulin sensitivity, stimulate insulin secretion, and exert functions such as lowering blood glucose, regulating hepatic oxidative stress, reducing intestinal inflammation, and improving islet cell morphology by acting on the aryl hydrocarbon receptor (AHR) or Pregnane X receptor (PXR). In summary, this review aims to examine the interactions between tryptophan indole derivatives and T2DM thoroughly, elucidate potential therapeutic approaches, and pinpoint areas for further research.

Identification of tryptophan metabolism-related biomarkers for nonalcoholic fatty liver disease through network analysis

Background

Increasing evidence demonstrates that tryptophan metabolism is closely related to the development of nonalcoholic fatty liver disease (NAFLD). This study aimed to identify specific biomarkers of NAFLD associated with tryptophan metabolism and research its functional mechanism.

Methods

We downloaded NAFLD RNA-sequencing data from GSE89632 and GSE24807, and obtained tryptophan metabolism-related genes (TMRGs) from the MsigDB database. The R package limma and WGCNA were used to identify TMRGs-DEGs, and GO, KEGG and Cytoscape were used to analyze and visualize the data. Immune cell infiltration analysis was used to explore the immune mechanism of NAFLD and the biomarkers. We also validated extended levels of biomarkers.

Results

We identified 375 NAFLD differentially expressed genes (DEGs) and 85 TMRGs-DEGs. GO/KEGG analysis revealed that TMRGs-DEGs were mainly enriched in triglyceride and cholesterol metabolism. ROC curves identified CCL20 (AUC = 0.917), CD160 (AUC = 0.933) and CYP7A1 (AUC = 1) as biomarkers of NAFLD. Immune infiltration analysis showed significant differences in ten immune cells, and the activation of dendritic cells and mast cells were highly positively correlated with NAFLD. CCL20, CD160 and CYP7A1 were highly correlated with M2 macrophage, neutrophil and mast cells activation, respectively. Twenty-seven TMRGs correlated with hub genes, and gene set enrichment analysis demonstrated their function in tryptophan- and lysine-containing metabolic process. We identified 41 therapeutic drug matches which corresponded to two hub genes and four drugs which co-targeted CCL20 and CYP7A1. Finally, three hub genes were validated in our mouse model.

Conclusions

CCL20, CD160 and CYP7A1 are tryptophan metabolism-related biomarkers of NAFLD, related to glycerol ester and cholesterol metabolism. We screened four compounds which co-target CCL29 and CYP7A1 to provide potential experimental drugs for NAFLD.

Multi-omics profiling of dairy cattle oxidative stress identifies hindgut-derived Phascolarctobacterium succinatutens exhibiting antioxidant activity

An imbalance between oxidative and antioxidant processes in the host can lead to excessive oxidation, a condition known as oxidative stress (OS). Although changes in the hindgut microbiota have been frequently linked to OS, the specific microbial and metabolic underpinnings of this association remain unclear. In this study, we enrolled 81 postpartum Holstein cows and stratified them into high oxidative stress (HOS, n = 9) and low oxidative stress (LOS, n = 9) groups based on the oxidative stress index (OSi). Using a multi-omics approach, we performed 16S rRNA gene sequencing to evaluate microbial diversity, conducted metagenomic analysis to identify functional bacteria, and utilized untargeted metabolomics to profile serum metabolites. Our analyses revealed elevated levels of kynurenine, formyl-5-hydroxykynurenamine, and 5-hydroxyindole-3-acetic acid in LOS dairy cows. Additionally, the LOS cows had a higher abundance of short-chain fatty acids (SCFAs)-producing bacteria, including Bacteroidetes bacterium, Paludibacter propionicigenes, and Phascolarctobacterium succinatutens (P. succinatutens), which were negatively correlated with OSi. To explore the potential role of these bacteria in mitigating OS, we administered P. succinatutens (108 cfu/day for 14 days) to C57BL/6 J mice (n = 10). Oral administration of P. succinatutens significantly increased serum total antioxidant capacity, decreased total oxidants, and reduced OSi in mice. Moreover, this treatment promoted activation of the Nrf2-Keap1 antioxidant pathway, significantly enhancing the enzymatic activities of GSH-Px and SOD, as well as the concentrations of acetate and propionate in the colon. In conclusion, our findings suggest that systemic tryptophan metabolism and disordered SCFAs production are concurrent factors influenced by hindgut microbiota and associated with OS development. Modulating the hindgut microbiota, particularly by introducing specific SCFAs-producing bacteria, could be a promising strategy for combating OS.

Gut Microbiota Metabolites and Chronic Diseases: Interactions, Mechanisms, and Therapeutic Strategies

The gut microbiota, shaped by factors such as diet, lifestyle, and genetics, plays a pivotal role in regulating host metabolism, immune function, and overall health. The diversity and balance of the gut microbiota are closely linked to the onset and progression of various chronic diseases. A growing body of evidence has demonstrated that alterations in the composition, function, and metabolites of the gut microbiota are significantly associated with cardiovascular diseases, including hypertension, atherosclerosis, and heart failure; metabolic disorders such as obesity, type 2 diabetes, and metabolic dysfunction-associated steatotic liver disease; and gastrointestinal conditions like inflammatory bowel disease and colorectal cancer. Despite substantial advances in microbiome research, challenges remain in fully elucidating the causal relationships between the gut microbiota and disease, as well as in translating these insights into clinical applications. This review aims to investigate the regulatory pathways via which the gut microbiota affects cardiovascular health, metabolic function, and gastrointestinal disease. Additionally, it highlights emerging strategies for the prevention and treatment of these chronic conditions, focusing on microbiota-targeted therapies and personalized dietary interventions as promising approaches for improving health outcomes.

L-Tryptophan-Rich Diet Alleviates High-Intensity-Exercise-Induced Liver Dysfunction via the Metabolite Indole-3-Acetic Acid and AhR Activation

High-intensity exercise (HIE) induces liver dysfunction and is detrimental to exercise performance. The underlying mechanism and preventive strategy urgently need to be explored. We increased the amount of tryptophan appropriately in the diet and explored the effect of an L-tryptophan-rich diet on the alleviation of HIE-induced liver dysfunction and the underlying mechanism. In this work, by establishing a C57BL/6 mouse model of high-intensity swimming exercise, the results demonstrated an L-tryptophan-rich diet significantly attenuated HIE-induced liver dysfunction, which was associated with increased levels of the tryptophan metabolite indole-3-acetic acid (IAA). Furthermore, IAA indeed exerted a protective effect against HIE-induced liver dysfunction in vivo and LPS-induced hepatocyte dysfunction in vitro. In conclusion, an L-tryptophan-rich diet may be a promising strategy to prevent HIE-induced liver dysfunction and metabolic disturbance via the metabolite indole-3-acetic acid and AhR activation.

The current findings on the gut-liver axis and the molecular basis of NAFLD/NASH associated with gut microbiome dysbiosis

Recent research has highlighted the complex relationship between gut microbiota, metabolic pathways, and nonalcoholic fatty liver disease (NAFLD) progression. Gut dysbiosis, commonly observed in NAFLD patients, impairs intestinal permeability, leading to the translocation of bacterial products like lipopolysaccharides, short-chain fatty acids, and ethanol to the liver. These microbiome-associated mechanisms contribute to intestinal and hepatic inflammation, potentially advancing NAFLD to NASH. Dietary habits, particularly those rich in saturated fats and fructose, can modify the microbiome composition, leading to dysbiosis and fatty liver development. Metabolomic approaches have identified unique profiles in NASH patients, with specific metabolites like ethanol linked to disease progression. While bariatric surgery has shown promise in preventing NAFLD progression, the role of gut microbiome and metabolites in this improvement remains to be proven. Understanding these microbiome-related pathways may provide new diagnostic and therapeutic targets for NAFLD and NASH. A comprehensive review of current literature was conducted using multiple medical research databases, including PubMed, Scopus, Web of Science, Embase, Cochrane Library, ClinicalTrials.gov, ScienceDirect, Medline, ProQuest, and Google Scholar. The review focused on studies that examine the relationship between gut microbiota composition, metabolic pathways, and NAFLD progression. Key areas of interest included microbial dysbiosis, endotoxin production, and the influence of diet on gut microbiota. The analysis revealed that gut dysbiosis contributes to NAFLD through several mechanisms, diet significantly influences gut microbiota composition, which in turn affects liver function through the gut-liver axis. High-fat diets can lead to dysbiosis, altering microbial metabolic activities and promoting liver inflammation. Specifically, gut microbiota-mediated generation of saturated fatty acids, such as palmitic acid, can activate liver macrophages and increase TNF-α expression, contributing to NASH development. Different dietary components, including cholesterol, fiber, fat, and carbohydrates, can modulate the gut microbiome and influence NAFLD progression. This gut-liver axis plays a crucial role in maintaining immune homeostasis, with the liver responding to gut-derived bacteria by activating innate and adaptive immune responses. Microbial metabolites, such as bile acids, tryptophan catabolites, and branched-chain amino acids, regulate adipose tissue and intestinal homeostasis, contributing to NASH pathogenesis. Additionally, the microbiome of NASH patients shows an elevated capacity for alcohol production, suggesting similarities between alcoholic steatohepatitis and NASH. These findings indicate that targeting the gut microbiota may be a promising approach for NASH treatment and prevention. Recent research highlights the potential of targeting gut microbiota for managing nonalcoholic fatty liver disease (NAFLD). The gut-liver axis plays a crucial role in NAFLD pathophysiology, with dysbiosis contributing to disease progression. Various therapeutic approaches aimed at modulating gut microbiota have shown promise, including probiotics, prebiotics, synbiotics, fecal microbiota transplantation, and dietary interventions. Probiotics have demonstrated efficacy in human randomized controlled trials, while other interventions require further investigation in clinical settings. These microbiota-targeted therapies may improve NAFLD outcomes through multiple mechanisms, such as reducing inflammation and enhancing metabolic function. Although lifestyle modifications remain the primary recommendation for NAFLD management, microbiota-focused interventions offer a promising alternative for patients struggling to achieve weight loss targets.

Protective effects of atorvastatin on testicular dysfunction and reduced sperm quality induced by high-fat diet in mice: The inhibitory mechanism of oxidative stress

Obesity significantly impairs various organs through the exacerbation of oxidative stress. Atorvastatin, a lipid-lowering agent, has shown potential in treating obesity-related metabolic disorders. This study aimed to assess the impact of obesity on male testicular development and sperm quality, and to evaluate the protective role of atorvastatin. Male C57BL/6 mice were fed a high-fat diet (HFD) containing 60% fat for 8 weeks to induce obesity. Atorvastatin was administered at doses of 3, 6, or 12 mg/kg/d. The results showed that compared to the control group, HFD-fed mice exhibited significantly increased body weight, serum cholesterol, and triglyceride levels. Additionally, they showed abnormal testicular morphology, increased sperm deformity rates, and reduced sperm count and motility. HFD reduced serum testosterone levels and the expression of key steroid synthase StAR in testes, along with decreased expression of tight junction proteins Occludin and ZO-1 at the blood-testis barrier. HFD also upregulated BAX expression and downregulated BCL2 expression, with concomitant reductions in antioxidant enzyme activities (SOD, GSH-px) and increased oxidative stress, as reflected by elevated serum MDA levels. Atorvastatin treatment restored testicular and sperm health in a dose-dependent manner, enhancing testosterone synthesis, improving blood-testis barrier integrity, and mitigating apoptosis and oxidative stress. In conclusion, HFD negatively affects male reproductive health, while atorvastatin, particularly at higher doses, offers significant protection through the inhibition of oxidative stress, underscoring its potential clinical utility.

Indole-3-acetic acid and chenodeoxycholic acid attenuate TLR4/NF-κB signaling and endoplasmic reticulum stress in valproic acid-induced neurotoxicity

Valproic acid (VA) is a commonly prescribed medication for epilepsy and other neurological conditions. Although effective, VA use can lead to neurotoxicity, especially with chronic use. This study aimed to investigate the potential neuroprotective properties of indole-3-acetic acid (IAA) and chenodeoxycholic acid (CDCA) in an animal model of VA-induced brain injury. Rats received intraperitoneal injections of VA at a dose of 500 mg/kg/day for 3 weeks. Concurrently, they were orally treated with IAA (40 mg/kg/day) and/or CDCA (90 mg/kg/day). The results showed significantly increased oxidative stress and inflammation markers in the VA-exposed group indicated by the reduced levels of glutathione (GSH, P < 0.0001) and superoxide dismutase (SOD, P < 0.01) and the elevated inflammatory cytokines Interleukin-6 (IL-6, P < 0.0001) and tumor necrosis factor-alpha (TNFα, P < 0.01). VA also induced nuclear factor kappa B (NF-κB, P < 0.01), toll-like receptor 4 (TLR4, P < 0.05), and endoplasmic reticulum (ER) stress markers, as evidenced by increased immunoreactivity of GRP78 (glucose-regulated protein 78, P < 0.0001), transcription factor 6 (ATF-6, P < 0.05) and CHOP (C/EBP homologous protein, P < 0.0001). Treatment with IAA or CDCA attenuated VA-induced neurotoxicity, to a variable extent, by improving oxidative, inflammatory, and ER stress markers. This study demonstrates that IAA and CDCA exert protective effects against VA-induced neurotoxicity by mitigating oxidative stress, inflammation, and ER stress. Further investigations are recommended to validate these findings in other neurotoxicity models.

The Microbiome and Metabolic Dysfunction-Associated Steatotic Liver Disease

Metabolic dysfunction-associated steatotic liver disease (MASLD) is a condition wherein excessive fat accumulates in the liver, leading to inflammation and potential liver damage. In this narrative review, we evaluate the tissue microbiota, how they arise and their constituent microbes, and the role of the intestinal and hepatic microbiota in MASLD. The history of bacteriophages (phages) and their occurrence in the microbiota, their part in the potential causation of MASLD, and conversely, "phage therapy" for antibiotic resistance, obesity, and MASLD, are all described. The microbiota metabolism of bile acids and dietary tryptophan and histidine is defined, together with the impacts of their individual metabolites on MASLD pathogenesis. Both periodontitis and intestinal microbiota dysbiosis may cause MASLD, and how individual microorganisms and their metabolites are involved in these processes is discussed. Novel treatment opportunities for MASLD involving the microbiota exist and include fecal microbiota transplantation, probiotics, prebiotics, synbiotics, tryptophan dietary supplements, intermittent fasting, and phages or their holins and endolysins. Although FDA is yet to approve phage therapy in clinical use, there are multiple FDA-approved clinical trials, and this may represent a new horizon for the future treatment of MASLD.

Poria cocos-Derived Exosome-like Nanovesicles Alleviate Metabolic Dysfunction-Associated Fatty Liver Disease by Promoting Mitophagy and Inhibiting NLRP3 Inflammasome Activation

Metabolic dysfunction-associated fatty liver disease (MAFLD) affects approximately one-quarter of the world's adult population, and no effective therapeutic drugs are available. Poria cocos is a fungus used as a herb and food nutrient for centuries as well as for MAFLD treatment. Exosome-like nanovesicles have many pharmacological activities; however, studies on the effects of Poria cocos-derived exosome-like nanovesicles (PCELNs) on MAFLD are lacking. Therefore, our study aimed at identifying the effects and mechanism of action of PCELNs on MAFLD. PCELNs were isolated by ultracentrifugation and their morphology was characterized, such as particle size, zeta potential, protein distributions, as well as lipid and miRNA compositions. Then, the absorption and distribution of PCELNs were observed in vivo and in vitro. Finally, L02 cell steatosis model induced by fat emulsion and MAFLD mouse model induced by high-fat diet (HFD) were used to evaluate the effect and mechanism of PCELNs on MAFLD. PCELNs were membrane structured vesicles, with a particle size of 161.4 ± 1.7 nm, a zeta potential of -3.20 ± 0.37 mV, and contained a range of proteins, lipids, and miRNAs. PCELNs were absorbed by L02 cells and targeted the liver and spleen after intraperitoneal injection. PCELNs inhibited body weight gain and improved the index of heart, liver, spleen, and various fats, as well as decreased lipid accumulation and lipid level. They also protected mitochondrial ultrastructure and regulated oxidative stress and energy metabolism disorder. Furthermore, PCELNs increased PTEN induced kinase 1 (PINK1), E3 ubiquitin ligase (Parkin) and microtubule associated protein light chain-3 (LC3) protein expression in the liver, reduced oxidized mitochondrial DNA (Ox-mtDNA) content in mitochondria and cytoplasm of the liver, reduced nucleotide binding oligomerization domain-like receptor protein 3 (NLRP3), pro-cysteinyl aspartate specific proteinase-1 (caspase-1), cleared-caspase-1, and mature-interleukin-1β (IL-1β) protein expression in the liver, and reduced the levels of tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), IL-1β, and interleukin-18 (IL-18) in serum and liver. In conclusion, we demonstrated that PCELNs may alleviate HFD-induced MAFLD by promoting mitochondrial autophagy and inhibiting NLRP3 inflammasome activation.

Bifidobacterium longum CECT 30763 improves depressive- and anxiety-like behavior in a social defeat mouse model through the immune and dopaminergic systems

Adolescence is a crucial period marked by profound changes in the brain. Exposure to psychological stressors such as bullying, abuse or maltreatment during this developmental period may increase the risk of developing depression, anxiety and comorbid cardiometabolic conditions. Chronic psychological stress is associated with behavioral changes and disruption of the hypothalamic-pituitary-adrenal axis, leading to corticosterone overproduction in rodents and changes in both the immune system and the gut microbiome. Here, we demonstrate the ability of Bifidobacterium longum CECT 30763 (B. longum) to ameliorate adolescent depressive and anxiety-like behaviors in a chronic social defeat (CSD) mouse model. The mechanisms underlying this beneficial effect are related to the ability of B. longum to attenuate the inflammation and immune cell changes induced by CSD after the initial stress exposure through the induction of T regulatory cells with enduring effects that may prevent and mitigate the adverse consequences of repeated stress exposure on mental and cardiometabolic health. B. longum administration also normalized dopamine release, metabolism and signaling at the end of the intervention, which may secondarily contribute to the reversal of behavioral changes. The anti-inflammatory effects of B. longum could also explain its cardioprotective effects, which were reflected in an amelioration of the oxidative stress-induced damage in the heart and improved lipid metabolism in the liver. Overall, our findings suggest that B. longum regulates the links between the immune and dopaminergic systems from the gut to the brain, potentially underpinning its beneficial psychobiotic and physiological effects in CSD.

Pharmacological treatment for metabolic dysfunction-associated steatotic liver disease and related disorders: Current and emerging therapeutic options

Metabolic dysfunction-associated steatotic liver disease (MASLD; formerly known as nonalcoholic fatty liver disease) is a chronic liver disease affecting over a billion individuals worldwide. MASLD can gradually develop into more severe liver pathologies, including metabolic dysfunction-associated steatohepatitis (MASH), cirrhosis, and liver malignancy. Notably, although being a global health problem, there are very limited therapeutic options against MASLD and its related diseases. While a thyroid hormone receptor agonist (resmetirom) is recently approved for MASH treatment, other efforts to control these diseases remain unsatisfactory. Given the projected rise in MASLD and MASH incidence, it is urgent to develop novel and effective therapeutic strategies against these prevalent liver diseases. In this article, the pathogenic mechanisms of MASLD and MASH, including insulin resistance, dysregulated nuclear receptor signaling, and genetic risk factors (eg, patatin-like phospholipase domain-containing 3 and hydroxysteroid 17-β dehydrogenase-13), are introduced. Various therapeutic interventions against MASH are then explored, including approved medication (resmetirom), drugs that are currently in clinical trials (eg, glucagon-like peptide 1 receptor agonist, fibroblast growth factor 21 analog, and PPAR agonist), and those failed in previous trials (eg, obeticholic acid and stearoyl-CoA desaturase 1 antagonist). Moreover, given that the role of gut microbes in MASLD is increasingly acknowledged, alterations in the gut microbiota and microbial mechanisms in MASLD development are elucidated. Therapeutic approaches that target the gut microbiota (eg, dietary intervention and probiotics) against MASLD and related diseases are further explored. With better understanding of the multifaceted pathogenic mechanisms, the development of innovative therapeutics that target the root causes of MASLD and MASH is greatly facilitated. The possibility of alleviating MASH and achieving better patient outcomes is within reach. SIGNIFICANCE STATEMENT: Metabolic dysfunction-associated steatotic liver disease (MASLD) is the most common chronic liver disease worldwide, and it can progress to more severe pathologies, including steatohepatitis, cirrhosis, and liver cancer. Better understanding of the pathogenic mechanisms of these diseases has facilitated the development of innovative therapeutic strategies. Moreover, increasing evidence has illustrated the crucial role of gut microbiota in the pathogenesis of MASLD and related diseases. It may be clinically feasible to target gut microbes to alleviate MASLD in the future.

Spatial mapping of dextran sodium sulphate-induced intestinal inflammation and its systemic effects

Inflammatory bowel disease (IBD) is a multifactorial disease, and patients frequently experience extraintestinal manifestations affecting multiple sites. Causes of systemic inflammation remain poorly understood, but molecules originating from the intestine likely play a role, with microbial and host small molecules polarizing host immune cells towards a pro- or anti-inflammatory phenotype. Using the dextran sodium sulfate (DSS) mouse model, which mimics the disrupted barrier function, microbial dysbiosis, and immune cell dysregulation of IBD, we investigated metabolomic and phenotypic changes at intestinal and systemic sites. Using spatial biology approaches, we mapped the distribution and relative abundance of molecules and cell types across a range of tissues, revealing significant changes in DSS-treated mice. Molecules identified as contributing to the statistical separation of treated from control mice were spatially localized within organs to determine their effects on cellular phenotypes through imaging mass cytometry. This spatial approach identified both intestinal and systemic molecular drivers of inflammation, including several not previously implicated in inflammation linked to IBD or the systemic effects of intestinal inflammation. Metabolic and inflammatory pathway interplay underpins systemic disease, and determining drivers at the molecular level may aid the development of new targeted therapies.

Influence of gut microbial metabolites on tumor immunotherapy: mechanisms and potential natural products

In recent years, tumor immunotherapy has made significant breakthroughs in the treatment of malignant tumors. However, individual differences in efficacy have been observed in clinical practice. There is increasing evidence that gut microbial metabolites influence the efficacy of distal tumor immunotherapy via the gut-liver axis, the gut-brain axis and the gut-breast axis, a process that may involve modulating the expression of immune cells and cytokines in the tumor microenvironment (TME). In this review, we systematically explore the relationship between gut microbial metabolites and tumor immunotherapy, and examine the corresponding natural products and their mechanisms of action. The in-depth exploration of this research area will provide new ideas and strategies to enhance the efficacy of tumor immunotherapy and mitigate adverse effects.

Genetic mapping of serum metabolome to chronic diseases among Han Chinese

Serum metabolites are potential regulators for chronic diseases. To explore the genetic regulation of metabolites and their roles in chronic diseases, we quantified 2,759 serum metabolites and performed genome-wide association studies (GWASs) among Han Chinese individuals. We identified 184 study-wide significant (p < 1.81 × 10-11) metabolite quantitative trait loci (metaboQTLs), 88.59% (163) of which were novel. Notably, we identified Asian-ancestry-specific metaboQTLs, including the SNP rs2296651 for taurocholic acid and taurochenodesoxycholic acid. Leveraging the GWAS for 37 clinical traits from East Asians, Mendelian randomization analyses identified 906 potential causal relationships between metabolites and clinical traits, including 27 for type 2 diabetes and 38 for coronary artery disease. Integrating genetic regulation of the transcriptome and proteome revealed putative regulators of several metabolites. In summary, we depict a landscape of the genetic architecture of the serum metabolome among Han Chinese and provide insights into the role of serum metabolites in chronic diseases.

Gut Bacteria-Derived Tryptamine Ameliorates Diet-Induced Obesity and Insulin Resistance in Mice

Tryptophan is an essential amino acid that is metabolized in the intestine by gut bacteria into indole derivatives, including tryptamine. However, little is known about which bacterial tryptophan metabolites directly influence obesity. In this study, we identified tryptamine as a bacterial metabolite that significantly reduced fat mass following the intraperitoneal injection of five bacterial tryptophan end-products in a diet-induced obese mouse model. Interestingly, tryptamine, a serotonin analog, inhibited both lipogenesis and lipolysis in adipose tissue, which was further confirmed in a 3T3-L1 adipocyte cell culture study. Moreover, oral tryptamine supplementation markedly reduced fat mass and improved insulin sensitivity in a long-term, high-fat-diet, pair-feeding model. These studies demonstrate the therapeutic potential of tryptamine, a bacterial tryptophan metabolite, in ameliorating obesity and insulin resistance by directly regulating lipogenesis and lipolysis in white adipose tissue.

Yinchen lipid-lowering tea attenuates lipid deposition in a fatty liver model by regulating mitochondrial dysfunction through activation of AdipoR1/AMPK/SIRT1 signaling

This study investigated the ameliorative effects of Yinchen lipid-lowering tea (YCLLT) on Non-alcoholic fatty liver disease (NAFLD), the specific mechanism involved was also studied. We modeled hepatocellular steatosis with HepG2 cells and intervened with different concentrations of YCLLT-containing serum. Lipid deposition was assessed by oil red O staining and AdipoR1 expression was analyzed by Western blot. The hepatocyte steatosis model was further treated with YCLLT-containing serum and/or silencing AdipoR1. Lipid deposition was observed by oil red O staining. Flow cytometry was used to detect apoptosis and mitochondrial membrane potential. The levels of TNF-α, IL-6, MDA, 8-OHdG, and ATP were analyzed by ELISA or the corresponding kits. The mitochondrial structure was observed by transmission electron microscopy. The expression of AdipoR1/AMPK/SIRT1 signaling pathway factors was analyzed by Western blot, and co-localization of SIRT1 and immunofluorescence. The results revealed that YCLLT attenuated lipid deposition, inhibited the levels of inflammatory factors TNF-α and IL-6, reduced the levels of MDA and 8-OHdG, up-regulated the ATP content and mitochondrial membrane potential, and promoted the expression of AdipoR1, p-LKB1, p-AMPKα, SIRT1, and PGC-1a in a cellular model of NAFLD. Further, silencing of AdipoR1 inhibited the ameliorative effect of YCLLT in the NAFLD cell model. Altogether, Yinchen lipid-lowering tea attenuates lipid deposition in a fatty liver model by improving mitochondrial function via activating AdipoR1/AMPK/ SIRT1 signaling.

Lactiplantibacillus plantarum improves the growth performance and meat quality of broilers by regulating the cecal microbiota and metabolites

Gut microbiota can digest and ferment feed into metabolites to influence the meat quality. Probiotics are used to regulate the gut microbiota. In this study, a total of 360 broilers were assigned to 4 treatments (10 broilers per cage): control (Con), low dose of Lactiplantibacillus plantarum HW1 (Lp_L), medium dose of Lp (Lp_M) and high dose of Lp (Lp_H) for a 42-day experimental period. Results showed that the Lp treatments improved the growth performance, carcass traits, breast meat quality, and also influenced the fatty acids composition, including the decrease of n-6PUFA/n-3PUFA, and the increase of C18:3n3, ∑n-3PUFA and PUFA/SFA. The lipid metabolism-related gene expressions in the liver showed that Lp treatments increased the expression of AMPK, CPT-1α, PPARα, ATGL and also decreased the expression of PPARγ, SREBP-1c, ACC, FAS, LPL, and SCD. Moreover, the abundances of gut microbiota, such as Synergistaceae and Synergistes were influenced by the Lp treatments. Functional prediction of the gut microbiota indicated that pathways, including pancreatic secretion and spliceosome were enriched by the Lp treatments. Untargeted metabolomics revealed that the Lp treatments altered the content of metabolites, such as 6-ketomyristic acid and indole-3-acetamide. These metabolites were enriched in pathways including fatty acid metabolism. Correlation analyses revealed potential interactions between growth performance and meat quality, as well as gut microbiota (Synergistes, etc.) and metabolites (6-ketomyristic acid, etc.). Overall, our data show that the Lp treatments significantly improved the growth performance, carcass traits and meat quality of broilers by regulating fatty acids, gut microbiota and metabolites.

Chronic prostatitis/chronic pelvic pain syndrome induces metabolomic changes in expressed prostatic secretions and plasma

ABSTRACT

Chronic prostatitis/chronic pelvic pain syndrome (CP/CPPS) is a complex disease that is often accompanied by mental health disorders. However, the potential mechanisms underlying the heterogeneous clinical presentation of CP/CPPS remain uncertain. This study analyzed widely targeted metabolomic data of expressed prostatic secretions (EPS) and plasma to reveal the underlying pathological mechanisms of CP/CPPS. A total of 24 CP/CPPS patients from The Second Nanning People's Hospital (Nanning, China), and 35 asymptomatic control individuals from First Affiliated Hospital of Guangxi Medical University (Nanning, China) were enrolled. The indicators related to CP/CPPS and psychiatric symptoms were recorded. Differential analysis, coexpression network analysis, and correlation analysis were performed to identify metabolites that were specifically altered in patients and associated with various phenotypes of CP/CPPS. The crucial links between EPS and plasma were further investigated. The metabolomic data of EPS from CP/CPPS patients were significantly different from those from control individuals. Pathway analysis revealed dysregulation of amino acid metabolism, lipid metabolism, and the citrate cycle in EPS. The tryptophan metabolic pathway was found to be the most significantly altered pathway associated with distinct CP/CPPS phenotypes. Moreover, the dysregulation of tryptophan and tyrosine metabolism and elevation of oxidative stress-related metabolites in plasma were found to effectively elucidate the development of depression in CP/CPPS. Overall, metabolomic alterations in the EPS and plasma of patients were primarily associated with oxidative damage, energy metabolism abnormalities, neurological impairment, and immune dysregulation. These alterations may be associated with chronic pain, voiding symptoms, reduced fertility, and depression in CP/CPPS. This study provides a local-global perspective for understanding the pathological mechanisms of CP/CPPS and offers potential diagnostic and therapeutic targets.

Dietary Influences on Gut Microbiota and Their Role in Metabolic Dysfunction-Associated Steatotic Liver Disease (MASLD)

Metabolic dysfunction-associated steatotic liver disease (MASLD) is a major contributor to liver-related morbidity, cardiovascular disease, and metabolic complications. Lifestyle interventions, including diet and exercise, are first line in treating MASLD. Dietary approaches such as the low-glycemic-index Mediterranean diet, the ketogenic diet, intermittent fasting, and high fiber diets have demonstrated potential in addressing the metabolic dysfunction underlying this condition. The development and progression of MASLD are closely associated with taxonomic shifts in gut microbial communities, a relationship well-documented in the literature. Given the importance of diet as a primary treatment for MASLD, it is important to understand how gut microbiota and their metabolic byproducts mediate favorable outcomes induced by healthy dietary patterns. Conversely, microbiota changes conferred by unhealthy dietary patterns such as the Western diet may induce dysbiosis and influence steatotic liver disease through promoting hepatic inflammation, up-regulating lipogenesis, dysregulating bile acid metabolism, increasing insulin resistance, and causing oxidative damage in hepatocytes. Although emerging evidence has identified links between diet, microbiota, and development of MASLD, significant gaps remain in understanding specific microbial roles, metabolite pathways, host interactions, and causal relationships. Therefore, this review aims to provide mechanistic insights into the role of microbiota-mediated processes through the analysis of both healthy and unhealthy dietary patterns and their contribution to MASLD pathophysiology. By better elucidating the interplay between dietary nutrients, microbiota-mediated processes, and the onset and progression of steatotic liver disease, this work aims to identify new opportunities for targeted dietary interventions to treat MASLD efficiently.

Role of Nrf2/HO-1 and cytoglobin signaling in the protective effect of indole-3-acetic acid and chenodeoxycholic acid against kidney injury induced by valproate

Background

Purpose: Valproate (VPA) is an antiepileptic drug widely used to treat various psychiatric and neurological disorders. Although its use is generally considered safe, chronic administration may lead to kidney injury. The mechanisms underlying VPA kidney toxicity are not entirely explored. This has prompted our investigation into a novel molecular signaling pathway involved in VPA-induced kidney injury and the exploration of strategies to ameliorate this toxicity using indole-3-acetic acid (IAA) and chenodeoxycholic acid (CDCA).

Methods

Rats were divided as follows: group I (control); group II (VPA group), where rats were administered VPA (500 mg/kg, i.p.) daily to induce kidney injury for 3 weeks; and groups III and IV, where rats were orally treated with either IAA (40 mg/kg) or CDCA (90 mg/kg), respectively, 1h post-VPA dose, for 3 weeks. The effects of these compounds on kidney tissues were evaluated with a focus on their antioxidant and anti-inflammatory properties using biochemical, histopathological, and immunohistochemical analyses.

Results

VPA caused a significant reduction in renal glutathione (GSH) and heme oxygenase-1 (HO-1) levels, and superoxide dismutase (SOD) activity, along with a significant elevation in malondialdehyde (MDA) levels. Similarly, tumor necrosis factor-α (TNF-α), interleukin-1beta (IL-1β), and interleukin-6 (IL-6) levels were significantly increased. Immunohistochemical analysis demonstrated a significant decline in the immunoreactivity of nuclear factor erythroid 2-related factor (Nrf2) and cytoglobin antigens in renal cells. However, administration of either IAA or CDCA significantly ameliorated these altered parameters, including Nrf2/HO-1 and cytoglobin levels.

Conclusion

IAA and CDCA alleviated the kidney injury induced by VPA via downregulating the inflammatory response and upregulating the antioxidant capacity in renal tissue.

Indole derivatives and their associated microbial genera are associated with the 1-year changes in cardiometabolic risk markers in Chinese adults

BACKGROUND

Although emerging evidence suggests that indole derivatives, microbial metabolites of tryptophan, may improve cardiometabolic health, the effective metabolites remain unclear. Also, the gut microbiota that involved in producing indole derivatives are less studied. We identified microbial taxa that can predict serum concentrations of the key indole metabolite indole-3-propionic acid (IPA) at population level and investigated the associations of indole derivatives and IPA-predicting microbial genera with cardiometabolic risk markers.

METHODS

In a cohort of 318 community-dwelling adults, serum indole metabolites and fecal microbiota (16S ribosomal RNA) were measured at baseline. Total cholesterol (TC), triglyceride (TG), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), and fasting blood glucose were repeatedly measured at baseline and again after 1 year. Brachial-ankle pulse wave velocity (baPWV) and ankle-brachial index (ABI) were measured after 1 year. The association between indole derivatives and the 1-year changes in blood lipids and glucose, and association of indole derivatives with baPWV and ABI were investigated using linear regression models.

RESULTS

Each 1 µmol/L increase in indole-3-acetic acid (IAA) levels was associated with 5.08% (P = 0.046) decrease in LDL-C. IPA levels were inversely associated with baPWV (percentage difference = -1.32%, P = 0.036). Per 1 µmol/L increase in Indole-3-aldehyde (IAld) levels was associated with 1.91% (P = 0.004) decrease in TC and 0.58% (P = 0.019) increase in ABI, but 1.79% decrease in HDL-C with borderline significance (P = 0.050). We identified 18 bacterial genera whose relative abundance was positively associated with serum IPA concentrations (PFDR < 0.05) and constructed a microbial score to reflect the overall IPA-producing potential. This score was inversely associated with baPWV (percentage difference = -0.48%, P = 0.007).

CONCLUSIONS

Our results suggest that IAA, IPA, IAld, and IPA-predicting microbial score are favorably associated with several cardiometabolic risk markers, although IAld may decrease HDL-C levels.

Indole-3-acetic acid enhances ruminal microbiota for aflatoxin B1 removal in vitro fermentation

Aflatoxin B1 (AFB1) has been recognized as a serious health risk for ruminant animals. From a molecular perspective, indole-3-acid (IAA) possesses the potential to enhance the removal of AFB1 by rumen microbiota. Therefore, this study aims to investigate the impact of different concentrations of IAA on the removal of AFB1 by rumen microbiota using an in vitro technique. Experiment 1: interaction between AFB1 and rumen fermentation. Experiment 2: The study used a randomized design with five IAA levels (0, 15, 150, 1,500, and 7,500 mg/kg) to examine the effect of IAA on AFB1 removal and its impact on rumen fermentation. The results showed: (1) the content of AFB1 gradually decreased, removal rate of up to 75.73% after 24 h. AFB1 exposure altered the rumen fermentation pattern, with significantly decreased in the acetic acid/propionic acid ratio (p < 0.05). It significantly reduced the relative proportions of R. amylophilus, P. ruminicola, and F. succinogenes (p < 0.05). (2) As the content of IAA increased, AFB1 exposure decreased. A total of 15 and 150 mg/kg IAA significantly mitigated the negative impact of AFB1 on key rumen bacteria (R. amylophilus, P. ruminicola and F. succinogenes), increased acetate levels and acetate/propionate ratio (p < 0.05). However, 1,500 mg/kg IAA lowered levels of propionate and isovalerate, adversely affected enzyme activities (pectinase, xylan and Carboxymethyl-cellulase) and relative proportions of microbiota (R. flavefaciens, P. ruminicola and F. succinogenes). In conclusion, IAA significantly removed AFB1, and in the range of 150 mg/kg of IAA reduced the negative effects of AFB1 on in vitro fermentation characteristics and fermentation end-products.

Metabolic disorders, inter-organ crosstalk, and inflammation in the progression of metabolic dysfunction-associated steatotic liver disease

Metabolic dysfunction-associated steatotic liver disease (MASLD) represents a global health concern, affecting over 30 % of adults. It is a principal driver in the development of cirrhosis and hepatocellular carcinoma. The complex pathogenesis of MASLD involves an excessive accumulation of lipids, subsequently disrupting lipid metabolism and prompting inflammation within the liver. This review synthesizes the recent research progress in understanding the mechanisms contributing to MASLD progression, with particular emphasis on metabolic disorders and interorgan crosstalk. We highlight the molecular mechanisms linked to these factors and explore their potential as novel targets for pharmacological intervention. The insights gleaned from this article have important implications for both the prevention and therapeutic management of MASLD.

Exploring tryptophan metabolism: The transition from disturbed balance to diagnostic and therapeutic potential in metabolic diseases

The rapidly rising prevalence of metabolic diseases has turned them into an escalating global health concern. By producing or altering metabolic products, the gut microbiota plays a pivotal role in maintaining human health and influencing disease development. These metabolites originate from the host itself or the external environment. In the system of interactions between microbes and the host, tryptophan (Trp) plays a central role in metabolic processes. As the amino acid in the human body that must be obtained through dietary intake, it is crucial for various physiological functions. Trp can be metabolized in the gut into three main products: The gut microbiota regulates the transformation of 5-hydroxytryptamine (5-HT, serotonin), kynurenine (Kyn), and various indole derivatives. It has been revealed that a substantial correlation exists between alterations in Trp metabolism and the initiation and progression of metabolic disorders, including obesity, diabetes, non-alcoholic fatty liver disease, and atherosclerosis, but Trp metabolites have not been comprehensively reviewed in metabolic diseases. As such, this review summarizes and analyzes the latest research, emphasizing the importance of further studying Trp metabolism within the gut microbiota to understand and treat metabolic diseases. This carries potential significance for improving human health and may introduce new therapeutic strategies.

Improved metabolic stability in iNOS knockout mice with Lactobacillus supplementation

Oxidative and nitrosative stress play pivotal roles in normal physiological processes and the pathogenesis of metabolic disorders. Previous studies from our lab demonstrated insulin resistance (IR), and dyslipidemia in iNOS-/- mice, emphasizing the importance of maintaining optimal redox balance. These mice exhibited altered gut microbiota with decreased Lactobacillus. Therefore, we hypothesized that Lactobacillus supplementation could mitigate metabolic disturbances in iNOS-/- mice. To test this hypothesis, iNOS-/- mice and wild-type (WT) mice were divided into four groups: iNOS-/- with or without Lactobacillus supplementation, WT with or without Lactobacillus supplementation and glucose tolerance, insulin resistance, gluconeogenesis, lipids, gene expression related to glucose and lipid metabolism (qPCR), fecal gut microbiota (16S rRNA sequencing), and serum and caecum metabolomics (LC-MS) were monitored. IR and dyslipidemic iNOS-/- mice exhibited reduced microbial diversity, diminished presence of Lactobacillus, and altered serum metabolites, indicating metabolic dysregulation. Lactobacillus supplementation in iNOS-/- mice effectively reversed glucose intolerance, IR, dyslipidemia, and associated metabolic irregularities compared to WT. These improvements correlated with changes in gene expression related to fatty acid synthesis in liver and adipose tissue, lipid oxidation in liver, and lipid efflux in intestinal tissue as compared to untreated iNOS-/- mice. Despite the positive effects on metabolic markers, Lactobacillus supplementation did not reduce body weight or rectify disrupted energy balance, as evidenced by reduced VCO2 production, heat generation, and metabolic rates in iNOS-/- mice. The results suggest that Lactobacillus supplementation ameliorates metabolic disturbances but did not fully restore disrupted energy balance, highlighting complex interactions between the gut microbiome and metabolism.

Postbiotics as Antiinflammatory and Immune-Modulating Bioactive Compounds in Metabolic Dysfunction-Associated Steatotic Liver Disease

Postbiotics, defined as products or metabolic byproducts secreted by live bacteria or released after bacterial lysis, are emerging as promising therapeutic agents for metabolic dysfunction-associated steatotic liver disease (MASLD). This review explores the antiinflammatory and immunomodulatory properties of various postbiotics, including exopolysaccharides, lipoteichoic acid, short-chain fatty acids, hydrogen sulfide, polyamines, tryptophan derivatives, and polyphenol metabolites. These compounds have demonstrated potential in mitigating steatotic liver infiltration, reducing inflammation, and slowing fibrosis progression in preclinical studies. Notably, postbiotics exert their beneficial effects by modulating gut microbiota composition, enhancing intestinal barrier function, optimizing lipid metabolism, reducing hepatic inflammation and steatosis, and exhibiting hepatoprotective properties. However, translating these findings into clinical practice requires well-designed trials to validate efficacy and safety, standardize production and characterization, and explore personalized approaches and synergistic effects with other therapeutic modalities. Despite challenges, the unique biological properties of postbiotics, such as enhanced safety compared to probiotics, make them attractive candidates for developing novel nutritional interventions targeting the multifactorial pathogenesis of MASLD. Further research is needed to establish their clinical utility and potential to improve liver and systemic outcomes in this increasingly prevalent condition.

Alterations in Glutathione Redox Homeostasis in Metabolic Dysfunction-Associated Fatty Liver Disease: A Systematic Review

Low molecular weight (LMW) thiols, particularly glutathione, play pathogenic roles in various multiorgan diseases. The liver is central for the production and systemic distribution of LMW thiols; thus, it is particularly susceptible to the imbalance of redox status that may determine increased oxidative stress and trigger the liver damage observed in metabolic dysfunction-associated steatotic liver disease (MASLD) models and humans. Indeed, increased LMW thiols at the cellular and extracellular levels may be associated with the severity of MASLD. Here, we present a systematic literature review of recent studies assessing the levels of LMW thiols in MASLD in in vivo and in vitro models and human subjects. Based on the PRISMA 2020 criteria, a search was conducted using PubMed and Scopus by applying inclusion/exclusion filters. The initial search returned 1012 documents, from which 165 eligible studies were selected, further described, and qualitatively analysed. Of these studies, most focused on animal and cellular models, while a minority used human fluids. The analysis of these studies revealed heterogeneity in the methods of sample processing and measurement of LMW thiol levels, which hinder cut-off values for diagnostic use. Standardisation of the analysis and measure of LMW thiol is necessary to facilitate future studies.

Predicting the therapeutic role and potential mechanisms of Indole-3-acetic acid in diminished ovarian reserve based on network pharmacology and molecular docking

BACKGROUND

Indole-3-acetic acid (IAA), an indole analog produced by intestinal microorganisms metabolizing tryptophan, has anti-inflammatory and antioxidant properties and thus has potential applications in ovarian protection, although the exact mechanism is unknown. The present study preliminarily investigated the pharmacological mechanism of IAA in alleviating diminished ovarian reserve (DOR) by network pharmacology and molecular docking.

METHODS

Relevant target proteins of IAA were searched in SwissTargetPrediction, PharmMapper, TargetNet, BATMAN-TCM, and SuperPred databases. The potential targets of DOR were obtained from GeneCards, DisGenet, OMIM, and Drugbank databases. Both common targets were then imported into the String website to construct a PPI network, and these targets were analyzed for GO and KEGG enrichment. Finally, we utilized molecular docking to validate the possible binding conformations between IAA and the candidate targets. We used in vitro experiments to preliminarily investigate the effects of IAA on DOR.

RESULTS

We obtained 88 potential targets for IAA and DOR interaction. We received 16 pivotal targets by constructed protein interaction screening. KEGG enrichment analysis mainly included the AGE-RAGE signaling pathway, IL-17 signaling pathway, Chemical carcinogenesis-reactive oxygen species in diabetic complications, etc. GO functional analysis showed that IAA treatment of DOR may involve biological processes such as response to external stimuli, hypoxia, gene expression, and regulation of enzyme activity. Molecular docking and in vitro experiments further revealed the potential effects of IAA on MMP2, TNF-α, AKT1, HSP90AA1, and NF-κ B.

CONCLUSION

We preliminarily revealed the potential protective effects of IAA against DOR through multiple targets and pathways, which provides a new research strategy for the molecular mechanism of IAA to alleviate DOR in the future. However, further studies need to demonstrate whether IAA can be used as a compound to prevent and treat DOR.

Tryptophan Metabolism-Regulating Probiotics Alleviate Hyperuricemia by Protecting the Gut Barrier Integrity and Enhancing Colonic Uric Acid Excretion

The balance of gut microbiota affects uric acid synthesis and excretion, influencing the development of hyperuricemia. This study aimed to investigate the effects and mechanisms of probiotics on hyperuricemia and adenine- and potassium oxonate-induced colonic damage. After two months of gavage at 109 CFU/day, the probiotic strains Lactobacillus rhamnosus UA260 and Lactobacillus plantarum YU28, identified through in vitro screening, significantly reduced serum uric acid levels in hyperuricemia mice from 109.71 ± 56.33 to 38.76 ± 15.06 and 33.22 ± 6.91 μmol/L, respectively. These strains attenuated inflammatory, repaired gut barrier damage, and enhanced colonic uric acid transporter function, thereby promoting uric acid excretion. Furthermore, the probiotics significantly reshaped gut microbiota by increasing the abundance of beneficial bacteria, including Lactobacillus and Coprococcus, while modulating tryptophan, purine, and riboflavin metabolism. Changes in tryptophan metabolites, specifically indole-3-propionic acid and indole-3-acetic acid, were correlated with xanthine oxidase activity, colonic injury, and the expression of the uric acid transporter protein ABCG2 during treatment. Probiotics intervention activated aryl hydrocarbon receptor pathways. These findings suggest that probiotics alleviate hyperuricemia and colonic inflammatory by regulating gut microbiota composition and tryptophan microbial metabolite pathways. Probiotics that modulate tryptophan microbial metabolism may provide a potential strategy for treating or preventing hyperuricemia.

Gardenia jasminoides Ellis. Polysaccharides Alleviated Cholestatic Liver Injury by Increasing the Production of Butyric Acid and FXR Activation

Gardenia jasminoides Ellis. polysaccharide (GPS) can protect against cholestatic liver injury (CLI) by regulating nuclear farnesoid X receptor (FXR).However, the mechanism via which GPS mediates the FXR pathway remains unclear. The aim of this study was to investigate the mechanism. Firstly, an alpha-naphthylisothiocyanate-induced cholestatic mouse model was administered with GPS to evaluate its hepatoprotective effects. The metabolic pathways influenced by GPS in cholestatic mice were detected by serum metabolomics. The effect of GPS on bile acid (BA) homeostasis, FXR expression, and liver inflammation were investigated. Second, the intestinal bacteria metabolites affected by GPS in vivo and in vitro were determined. The activation of FXR by sodium butyrate (NaB) was measured. Finally, the effects of NaB on cholestatic mice were demonstrated. The main pathways influenced by GPS involved BA biosynthesis. GPS upregulated hepatic FXR expression, improved BA homeostasis, reduced F4/80+ and Ly6G+ positive areas in the liver, and inhibited liver inflammation in cholestatic mice. Butyric acid was the most notable intestinal bacterial metabolite following GPS intervention. NaB activated the transcriptional activity of FXR in vitro, upregulated hepatic FXR and its downstream efflux transporter expression, and ameliorated disordered BA homeostasis in CLI mice. NaB inhibited the toll-like receptor 4/nuclear factor (TLR4/NF-κB) pathway and reduced inflammation and CLI in mice. An FXR antagonist suppressed the effects. In conclusion, GPS increased butyric acid production, which can activate hepatic FXR, reverse BA homeostasis disorder, and inhibit the TLR4/NF-κB inflammatory pathway, exerting protective effects against CLI.

Associations of dietary sources of antioxidant intake and NAFLD: NHANES 2017-2020 and Mendelian randomization

Purpose

To determine the association between dietary antioxidant sources and non-alcoholic fatty liver disease (NAFLD).

Methods

In this observational study, we utilized NHANES 2017-2020 data to identify the factors associated with NAFLD in dietary antioxidant sources via weighted multivariate logistic regression models. Then, Mendelian randomization (MR) was applied to investigate the effect of dietary antioxidant sources on NAFLD at the genetic level.

Results

Of the six dietary sources of antioxidants, only vitamin E (Vit E) was significantly associated with NAFLD (OR = 0.98; 95% CI: 0.97-0.99; p = 0.001). Upon adjusting for all covariates, it was determined that the highest quartile of dietary Vit E intake was associated with a decreased NAFLD occurrence compared with the lowest quartile of dietary Vit E intake (p < 0.001). The results of IVW-MR analysis revealed an association between Vit E and NAFLD (OR = 0.028; p = 0.039).

Conclusion

Our research indicates a negative and linear relationship between daily vitamin E intake and NAFLD.

Effect of whole grain and fiber consumption on chronic liver diseases: a systematic review and meta-analysis

Objective: The aim of the present study was to conduct a meta-analysis of observational studies to explore the latest evidence on the influence of whole grain and fiber consumption on total chronic liver diseases. Methods: We searched the PubMed and Web of Science online databases and reference lists of eligible articles up to June, 2024. Results: The odds ratio (OR) between whole grain intake and total chronic liver disease risk was 0.90 (95% confidence interval (CI): 0.81 to 0.99, p < 0.001) and indicated an OR of 0.65 (95% CI: 0.57 to 0.74, p < 0.001) between fiber intake and total chronic liver disease risk when comparing the highest and lowest total intake, both indicating a significant negative correlation. Furthermore, subgroup analysis revealed that the protective effect of whole grains on chronic liver diseases was the most significant in cirrhosis (OR = 0.65; 95% CI: 0.57 to 0.74) and mortality (OR = 0.37; 95% CI: 0.29 to 0.47). Conclusion: Whole grain and fiber intake has a protective effect on the risk of chronic liver diseases.

Deciphering the Gut–Liver Axis: A Comprehensive Scientific Review of Non-Alcoholic Fatty Liver Disease

Non-alcoholic fatty liver disease (NAFLD) has emerged as a significant global health issue. The condition is closely linked to metabolic dysfunctions such as obesity and type 2 diabetes. The gut–liver axis, a bidirectional communication pathway between the liver and the gut, plays a crucial role in the pathogenesis of NAFLD. This review delves into the mechanisms underlying the gut–liver axis, exploring the influence of gut microbiota, intestinal permeability, and inflammatory pathways. This review also explores the potential therapeutic strategies centered on modulating gut microbiota such as fecal microbiota transplantation; phage therapy; and the use of specific probiotics, prebiotics, and postbiotics in managing NAFLD. By understanding these interactions, we can better comprehend the development and advancement of NAFLD and identify potential therapeutic targets.

Indole-3-Acetic Acid Protects Against Lipopolysaccharide-induced Endothelial Cell Dysfunction and Lung Injury through the Activation of USP40

Lung microvascular endothelial cell (EC) dysfunction is the pathological hallmark of acute respiratory distress syndrome. Heat shock protein 90 (HSP90) is a key regulator in control of endothelial barrier disruption and inflammation. Our recent study has demonstrated that ubiquitin-specific peptidase 40 (USP40) preserves endothelial integrity by targeting HSP90β for its deubiquitination and inactivation. Indole-3-acetic acid (IAA), a plant hormone of the auxin class, can also be catabolized from dietary tryptophan by the intestinal microbiota. Accumulating evidence suggests that IAA reduces oxidative stress and inflammation and promotes intestinal barrier function. However, little is known about the role of IAA in endothelial cells and acute lung injury. In this study, we investigated the role of IAA in lung endothelial cell function in the context of acute lung injury. IAA exhibited EC barrier protection against LPS-induced reduction in transendothelial electrical resistance and inflammatory responses. The underlying mechanism of IAA on EC protective effects was investigated by examining the influence of IAA on degrees of HSP90 ubiquitination and USP40 activity. We identified that IAA, acting as a potential activator of USP40, reduces HSP90 ubiquitination, thereby protecting against LPS-induced inflammation in human lung microvascular endothelial cells as well as alleviating experimental lung injury. Furthermore, the EC protective effects of IAA against LPS-induced EC dysfunction and lung injury were abolished in USP40-deficient human lung microvascular endothelial cell and lungs of USP40 EC-specific knockout (USP40cdh5-ECKO) mice. Taken together, this study reveals that IAA protects against LPS-induced EC dysfunction and lung injury through the activation of USP40.

Interactions between Gut Microbiota and Natural Bioactive Polysaccharides in Metabolic Diseases: Review

The gut microbiota constitutes a complex ecosystem, comprising trillions of microbes that have co-evolved with their host over hundreds of millions of years. Over the past decade, a growing body of knowledge has underscored the intricate connections among diet, gut microbiota, and human health. Bioactive polysaccharides (BPs) from natural sources like medicinal plants, seaweeds, and fungi have diverse biological functions including antioxidant, immunoregulatory, and metabolic activities. Their effects are closely tied to the gut microbiota, which metabolizes BPs into health-influencing compounds. Understanding how BPs and gut microbiota interact is critical for harnessing their potential health benefits. This review provides an overview of the human gut microbiota, focusing on its role in metabolic diseases like obesity, type II diabetes mellitus, non-alcoholic fatty liver disease, and cardiovascular diseases. It explores the basic characteristics of several BPs and their impact on gut microbiota. Given their significance for human health, we summarize the biological functions of these BPs, particularly in terms of immunoregulatory activities, blood sugar, and hypolipidemic effect, thus providing a valuable reference for understanding the potential benefits of natural BPs in treating metabolic diseases. These properties make BPs promising agents for preventing and treating metabolic diseases. The comprehensive understanding of the mechanisms by which BPs exert their effects through gut microbiota opens new avenues for developing targeted therapies to improve metabolic health.

Gut microbial metabolites in MASLD: Implications of mitochondrial dysfunction in the pathogenesis and treatment

With an increasing prevalence, metabolic dysfunction-associated steatotic liver disease (MASLD) has become a major global health problem. MASLD is well-known as a multifactorial disease. Mitochondrial dysfunction and alterations in the gut bacteria are 2 vital events in MASLD. Recent studies have highlighted the cross-talk between microbiota and mitochondria, and mitochondria are recognized as pivotal targets of the gut microbiota to modulate the host's physiological state. Mitochondrial dysfunction plays a vital role in MASLD and is associated with multiple pathological changes, including hepatocyte steatosis, oxidative stress, inflammation, and fibrosis. Metabolites are crucial mediators of the gut microbiota that influence extraintestinal organs. Additionally, regulation of the composition of gut bacteria may serve as a promising therapeutic strategy for MASLD. This study reviewed the potential roles of several common metabolites in MASLD, emphasizing their impact on mitochondrial function. Finally, we discuss the current treatments for MASLD, including probiotics, prebiotics, antibiotics, and fecal microbiota transplantation. These methods concentrate on restoring the gut microbiota to promote host health.

Gut Microbiota and Sinusoidal Vasoregulation in MASLD: A Portal Perspective

Metabolic dysfunction-associated steatotic liver disease (MASLD) is a common condition with heterogeneous outcomes difficult to predict at the individual level. Feared complications of advanced MASLD are linked to clinically significant portal hypertension and are initiated by functional and mechanical changes in the unique sinusoidal capillary network of the liver. Early sinusoidal vasoregulatory changes in MASLD lead to increased intrahepatic vascular resistance and represent the beginning of portal hypertension. In addition, the composition and function of gut microbiota in MASLD are distinctly different from the healthy state, and multiple lines of evidence demonstrate the association of dysbiosis with these vasoregulatory changes. The gut microbiota is involved in the biotransformation of nutrients, production of de novo metabolites, release of microbial structural components, and impairment of the intestinal barrier with impact on innate immune responses, metabolism, inflammation, fibrosis, and vasoregulation in the liver and beyond. The gut-liver axis is a conceptual framework in which portal circulation is the primary connection between gut microbiota and the liver. Accordingly, biochemical and hemodynamic attributes of portal circulation may hold the key to better understanding and predicting disease progression in MASLD. However, many specific details remain hidden due to limited access to the portal circulation, indicating a major unmet need for the development of innovative diagnostic tools to analyze portal metabolites and explore their effect on health and disease. We also need to safely and reliably monitor portal hemodynamics with the goal of providing preventive and curative interventions in all stages of MASLD. Here, we review recent advances that link portal metabolomics to altered sinusoidal vasoregulation and may allow for new insights into the development of portal hypertension in MASLD.

Indole-3-carboxaldehyde alleviates acetaminophen-induced liver injury via inhibition of oxidative stress and apoptosis

Drug-induced liver injury (DILI) occurs frequently and can be life-threatening. Increasing researches suggest that acetaminophen (APAP) overdose is a leading cause of drug-induced liver injury. Indole-3-carboxaldehyde (I3A) alleviates hepatic inflammation, fibrosis and atherosclerosis, suggesting a potential role in different disease development. However, the question of whether and how I3A protects against acetaminophen-induced liver injury remains unanswered. In this study, we demonstrated that I3A treatment effectively mitigates acetaminophen-induced liver injury. Serum alanine/aspartate aminotransferases (ALT/AST), liver malondialdehyde (MDA) activity, liver glutathione (GSH), and superoxide dismutase (SOD) levels confirmed the protective effect of I3A against APAP-induced liver injury. Liver histological examination provided further evidence of I3A-induced protection. Mechanistically, I3A reduced the expression of apoptosis-related factors and oxidative stress, alleviating disease symptoms. Finally, I3A treatment improved survival in mice receiving a lethal dose of APAP. In conclusion, our study demonstrates that I3A modulates hepatotoxicity and can be used as a potential therapeutic agent for DILI.

The hepatoprotective effect of 4-phenyltetrahydroquinolines on carbon tetrachloride induced hepatotoxicity in rats through autophagy inhibition

BACKGROUND

The liver serves as a metabolic hub within the human body, playing a crucial role in various essential functions, such as detoxification, nutrient metabolism, and hormone regulation. Therefore, protecting the liver against endogenous and exogenous insults has become a primary focus in medical research. Consequently, the potential hepatoprotective properties of multiple 4-phenyltetrahydroquinolines inspired us to thoroughly study the influence of four specially designed and synthesized derivatives on carbon tetrachloride (CCl4)-induced liver injury in rats.

METHODS AND RESULTS

Seventy-seven Wistar albino male rats weighing 140 ± 18 g were divided into eleven groups to investigate both the toxicity profile and the hepatoprotective potential of 4-phenyltetrahydroquinolines. An in-vivo hepatotoxicity model was conducted using CCl4 (1 ml/kg body weight, a 1:1 v/v mixture with corn oil, i.p.) every 72 h for 14 days. The concurrent treatment of rats with our newly synthesized compounds (each at a dose of 25 mg/kg body weight, suspended in 0.5% CMC, p.o.) every 24 h effectively lowered transaminases, preserved liver tissue integrity, and mitigated oxidative stress and inflammation. Moreover, the histopathological examination of liver tissues revealed a significant reduction in liver fibrosis, which was further supported by the immunohistochemical analysis of α-SMA. Additionally, the expression of the apoptotic genes BAX and BCL2 was monitored using real-time PCR, which showed a significant decrease in liver apoptosis. Further investigations unveiled the ability of the compounds to significantly decrease the expression of autophagy-related proteins, Beclin-1 and LC3B, consequently inhibiting autophagy. Finally, our computer-assisted simulation dockingonfirmed the obtained experimental activities.

CONCLUSION

Our findings suggest that derivatives of 4-phenyltetrahydroquinoline demonstrate hepatoprotective properties in CCl4-induced liver damage and fibrosis in rats. The potential mechanism of action may be due to the inhibition of autophagy in liver cells.

Oxymatrine alleviates high-fat diet/streptozotocin-induced non-alcoholic fatty liver disease in C57BL/6 J mice by modulating oxidative stress, inflammation and fibrosis

Non-alcoholic fatty liver disease (NAFLD) represents a complex complication of type 2 diabetes mellitus (T2DM). Oxymatrine (OMT) is an alkaloid extracted from Sophora flavescens with broad pharmacological effects. However, there is currently a lack of research on OMT in the field of NAFLD. The present study aimed to explore the effects and underlying mechanisms of oxymatrine in treating T2DM with NAFLD. The T2DM mice model was induced by high-fat diet (HFD) combined with streptozotocin (STZ) injection in male C57BL/6 J mice. Animals were randomly divided into four groups (n = 8): Control group, DC group, OMT-L group (45 mg/kg i.g.), and OMT-H group (90 mg/kg, i.g.). The drug was administered once a day for 8 weeks. In addition, HepG2 hepatocytes were incubated with palmitic acid (PA) to establish a fatty liver cell model. Treated with OMT, the body weight and fasting blood glucose (FBG) of DC mice were reduced and the liver organ coefficient was significantly optimized. Meanwhile, OMT markedly enhanced the activities of key antioxidant enzymes, including superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px), and also reduced malondialdehyde (MDA) levels. These biochemical alterations were accompanied by noticeable improvements in liver histopathology. Furthermore, OMT down-regulated the expression of NOD-like receptor protein 3 (NLRP3), interleukin-1β (IL-1β), transforming growth factor-β1 (TGF-β1) and collagen I significantly, highlighting its potential in modulating inflammatory and fibrotic pathways. In conclusion, OMT improved liver impairment effectively in diabetic mice by suppressing oxidative stress, inflammation and fibrosis. These results suggest that OMT may represent a novel therapy for NAFLD with diabetes.

Gut microbiota induced epigenetic modifications in the non-alcoholic fatty liver disease pathogenesis

Non-alcoholic fatty liver disease (NAFLD) represents a growing global health concern that can lead to liver disease and cancer. It is characterized by an excessive accumulation of fat in the liver, unrelated to excessive alcohol consumption. Studies indicate that the gut microbiota-host crosstalk may play a causal role in NAFLD pathogenesis, with epigenetic modification serving as a key mechanism for regulating this interaction. In this review, we explore how the interplay between gut microbiota and the host epigenome impacts the development of NAFLD. Specifically, we discuss how gut microbiota-derived factors, such as lipopolysaccharides (LPS) and short-chain fatty acids (SCFAs), can modulate the DNA methylation and histone acetylation of genes associated with NAFLD, subsequently affecting lipid metabolism and immune homeostasis. Although the current literature suggests a link between gut microbiota and NAFLD development, our understanding of the molecular mechanisms and signaling pathways underlying this crosstalk remains limited. Therefore, more comprehensive epigenomic and multi-omic studies, including broader clinical and animal experiments, are needed to further explore the mechanisms linking the gut microbiota to NAFLD-associated genes. These studies are anticipated to improve microbial markers based on epigenetic strategies and provide novel insights into the pathogenesis of NAFLD, ultimately addressing a significant unmet clinical need.

Caffeic acid combined with arabinoxylan or β-glucan attenuates diet-induced obesity in mice via modulation of gut microbiota and metabolites

Polyphenols and dietary fibers in whole grains are important bioactive compounds to reduce risks for obesity. However, whether the combination of the two components exhibits a stronger anti-obesity effect remains unclear. Caffeic acid is a major phenolic acid in cereals, and arabinoxylan and β-glucan are biological macromolecules with numerous health benefits. Here, we investigated the effect of caffeic acid combined with arabinoxylan or β-glucan on glucose and lipid metabolism, gut microbiota, and metabolites in mice fed a high-fat diet (HFD). Caffeic acid combined with arabinoxylan or β-glucan significantly reduced the body weight, blood glucose, and serum free fatty acid concentrations. Caffeic acid combined with β-glucan effectively decreased serum total cholesterol levels and hepatic lipid accumulation, modulated oxidative and inflammatory stress, and improved gut barrier function. Compared with arabinoxylan, β-glucan, and caffeic acid alone, caffeic acid combined with arabinoxylan or β-glucan exhibited a better capacity to modulate gut microbiota, including increased microbial diversity, reduced Firmicutes/Bacteroidetes ratio, and increased abundance of beneficial bacteria such as Bifidobacterium. Furthermore, caffeic acid combined with β-glucan reversed HFD-induced changes in microbiota-derived metabolites involving tryptophan, purine, and bile acid metabolism. Thus, caffeic acid and β-glucan had a synergistic anti-obesity effect by regulating specific gut microbiota and metabolites.

The gut-liver axis in fatty liver disease: role played by natural products

Fatty liver disease, a condition characterized by fatty degeneration of the liver, mainly classified as non-alcoholic fatty liver disease (NAFLD) and alcoholic liver disease (ALD), has become a leading cause of cirrhosis, liver cancer and death. The gut-liver axis is the bidirectional relationship between the gut and its microbiota and its liver. The liver can communicate with the gut through the bile ducts, while the portal vein transports the products of the gut flora to the liver. The intestinal flora and its metabolites directly and indirectly regulate hepatic gene expression, leading to an imbalance in the gut-liver axis and thus contributing to the development of liver disease. Utilizing natural products for the prevention and treatment of various metabolic diseases is a prevalent practice, and it is anticipated to represent the forthcoming trend in the development of drugs for combating NAFLD/ALD. This paper discusses the mechanism of the enterohepatic axis in fatty liver, summarizes the important role of plant metabolites in natural products in fatty liver treatment by regulating the enterohepatic axis, and provides a theoretical basis for the subsequent development of new drugs and clinical research.

Identifying serum metabolite biomarkers for autoimmune diseases: a two-sample mendelian randomization and meta-analysis

Background

Extensive evidence suggests a link between alterations in serum metabolite composition and various autoimmune diseases (ADs). Nevertheless, the causal relationship underlying these correlations and their potential utility as dependable biomarkers for early AD detection remain uncertain.

Objective

The objective of this study was to employ a two-sample Mendelian randomization (MR) approach to ascertain the causal relationship between serum metabolites and ADs. Additionally, a meta-analysis incorporating data from diverse samples was conducted to enhance the validation of this causal effect.

Materials and methods

A two-sample MR analysis was performed to investigate the association between 486 human serum metabolites and six prevalent autoimmune diseases: systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), inflammatory bowel disease (IBD), dermatomyositis (DM), type 1 diabetes (T1D), and celiac disease (CeD). The inverse variance weighted (IVW) model was employed as the primary analytical technique for the two-sample MR analysis, aiming to identify blood metabolites linked with autoimmune diseases. Independent outcome samples were utilized for further validation of significant blood metabolites. Additional sensitivity analyses, including heterogeneity test, horizontal pleiotropy test, and retention rate analysis, were conducted. The results from these analyses were subsequently meta-integrated. Finally, metabolic pathway analysis was performed using the KEGG and Small Molecule Pathway Databases (SMPD).

Results

Following the discovery and replication phases, eight metabolites were identified as causally associated with various autoimmune diseases, encompassing five lipid metabolism types: 1-oleoylglycerophosphoethanolamine, 1-arachidonoylglycerophosphoethanolamine, 1-myristoylglycerophosphocholine, arachidonate (20:4 n6), and glycerol. The meta-analysis indicated that three out of these eight metabolites exhibited a protective effect, while the remaining five were designated as pathogenic factors. The robustness of these associations was further confirmed through sensitivity analysis. Moreover, an investigation into metabolic pathways revealed a significant correlation between galactose metabolism and autoimmune diseases.

Conclusion

This study revealed a causal relationship between lipid metabolites and ADs, providing novel insights into the mechanism of AD development mediated by serum metabolites and possible biomarkers for early diagnosis.

Microbial Indoles: Key Regulators of Organ Growth and Metabolic Function

Gut microbes supporting body growth are known but the mechanisms are less well documented. Using the microbial tryptophan metabolite indole, known to regulate prokaryotic cell division and metabolic stress conditions, we mono-colonized germ-free (GF) mice with indole-producing wild-type Escherichia coli (E. coli) or tryptophanase-encoding tnaA knockout mutant indole-non-producing E. coli. Indole mutant E. coli mice showed multiorgan growth retardation and lower levels of glycogen, cholesterol, triglycerides, and glucose, resulting in an energy deficiency despite increased food intake. Detailed analysis revealed a malfunctioning intestine, enlarged cecum, and reduced numbers of enterochromaffin cells, correlating with a metabolic phenotype consisting of impaired gut motility, diminished digestion, and lower energy harvest. Furthermore, indole mutant mice displayed reduction in serum levels of tricarboxylic acid (TCA) cycle intermediates and lipids. In stark contrast, a massive increase in serum melatonin was observed-frequently associated with accelerated oxidative stress and mitochondrial dysfunction. This observational report discloses functional roles of microbe-derived indoles regulating multiple organ functions and extends our previous report of indole-linked regulation of adult neurogenesis. Since indoles decline by age, these results imply a correlation with age-linked organ decline and levels of indoles. Interestingly, increased levels of indole-3-acetic acid, a known indole metabolite, have been shown to correlate with younger biological age, further supporting a link between biological age and levels of microbe-derived indole metabolites. The results presented in this resource paper will be useful for the future design of food intervention studies to reduce accelerated age-linked organ decline.

Degron tagging for rapid protein degradation in mice

Degron tagging allows proteins of interest to be rapidly degraded, in a reversible and tuneable manner, in response to a chemical stimulus. This provides numerous opportunities for understanding disease mechanisms, modelling therapeutic interventions and constructing synthetic gene networks. In recent years, many laboratories have applied degron tagging successfully in cultured mammalian cells, spurred by rapid advances in the fields of genome editing and targeted protein degradation. In this At a Glance article, we focus on recent efforts to apply degron tagging in mouse models, discussing the distinct set of challenges and opportunities posed by the in vivo environment.