Intestinal microbiota determines development of non-alcoholic fatty liver disease in mice

Metabolic-associated Fatty Liver Disease as Assessed by the Fatty Liver Index Among Migrant and Non-migrant Ghanaian Populations

BACKGROUND AND AIMS

Metabolic-associated fatty liver disease (MAFLD) is driven by high caloric intake and sedentary lifestyle. Migration towards high income countries may induce these driving factors; yet, the influence of such on the prevalence of MAFLD is clearly understudied. Here, we investigated the Fatty Liver Index (FLI), a proxy of steatosis in MAFLD, after migration of Ghanaian subjects.

METHODS

Cross-sectional data of 5282 rural, urban and migrant participants from the Research on Obesity and Diabetes among African Migrants (also known as RODAM) study were analyzed with logistic regression for geographical differences in FLI and associations with type 2 diabetes mellitus (T2DM), waist-to-hip ratio, and 10-year predicted risk of atherosclerotic cardiovascular disease (ASCVD).

RESULTS

Both FLI and the proportion with an FLI indicative of MAFLD steatosis (FLI ≥60) were higher in migrants compared with non-migrants. Prevalence of elevated FLI (FLI ≥60) in non-migrant males was 4.2% compared to 28.9% in migrants. For females, a similar gradient was observed, from 13.6% to 36.6% respectively. Compared to rural residents, the odds for a FLI ≥60 were higher in migrants living in urban Europe (odds ratio [OR] 9.02, 95% confidence interval [CI]: 5.02-16.20 for men, and 4.00, 95% CI: 3.00-5.34 for women). Compared to controls, the ORs for FLI ≥60 were 2.43 (95% CI: 1.73-3.41) for male T2DM cases and 2.02 (95% CI: 1.52-2.69) for female T2DM cases. One-unit higher FLI was associated with an elevated (≥7.5%) 10-year ASCVD risk (OR: 1.051, 95% CI: 1.041-1.062 for men, and 1.020, 95% CI: 1.015-1.026 for women).

CONCLUSIONS

FLI as a proxy for MAFLD increased stepwise in Ghanaians from rural areas, through urban areas, to Europe. Our results clearly warrant awareness for MAFLD in migrant population as well as confirmation with imaging modalities.

Effect of Lycium barbarum polysaccharide supplementation in non-alcoholic fatty liver disease patients: study protocol for a randomized controlled trial

BACKGROUND

Non-alcohol fatty liver disease (NAFLD) is the most common chronic liver disease in the world, with a high incidence and no effective treatment. At present, the targeted therapy of intestinal microbes for NAFLD is highly valued. Lycium barbarum polysaccharide (LBP), as the main active ingredient of Lycium barbarum, is considered to be a new type of prebiotic substance, which can improve NAFLD by regulating the gut microbiota. The purpose of this study is to evaluate the safety and efficacy of LBP supplementation in modulating gut microbiota for NAFLD patients.

METHODS

This randomized, double-blind, placebo-control study will be conducted in the physical examination center of the Ningxia Hui Autonomous Region People's Hospital. A total of 50 patients with NAFLD confirmed by abdominal ultrasound, laboratory tests, and questionnaire surveys will be recruited and randomly assigned into the control group (maltodextrin placebo capsules) and the intervention group (LBP supplementation capsules) for 3 months. Neither patients, nor investigators, nor data collectors will know the contents in each capsule and the randomization list. The primary outcome measure is the level of ALT concentration relief after the intervention. Secondary outcomes include gut microbiota abundance and diversity, intestinal permeability, patient's characteristic demographic data and body composition, adverse effects, and compliance from patients.

DISCUSSION

LBPs are potential prebiotics with the property of regulating host gut microbiota. Our previous studies have documented that LBP supplement can improve the liver damage and the gut microflora dysbiosis in NAFLD rats. This treatment would provide a more in-depth understanding of the effect of this LBP supplementation.

TRIAL REGISTRATION

Chinese Clinical Trial Register, ChiCTR2000034740 . Registered on 17 July 2020.

Intestinal dysbiosis in nonalcoholic fatty liver disease (NAFLD): focusing on the gut-liver axis

Nonalcoholic fatty liver disease (NAFLD) is one of the most common chronic liver disorders in humans, partly because it is closely related to metabolic disorders of the liver with increasing prevalence. NAFLD begins with hepatic lipid accumulation, which may cause inflammation and eventually lead to fibrosis in the liver. Numerous studies have demonstrated the close relationship between gut dysfunction (especially the gut microbiota and its metabolites) and the occurrence and progression of NAFLD. The bidirectional communication between the gut and liver, named the gut-liver axis, is mainly mediated by the metabolites derived from both the liver and gut through the biliary tract, portal vein, and systemic circulation. Herein, we review the effects of the gut-liver axis on the pathogenesis of NAFLD. We also comprehensively describe the potential molecular mechanisms from the perspective of the role of liver-derived metabolites and gut-related components in hepatic metabolism and inflammation and gut health, respectively. The study provides insights into the mechanisms underlying current summarizations that support the intricate interactions between a disordered gut and NAFLD and can provide novel strategies to lessen the prevalence and consequence of NAFLD.

Intestinal microbiota participates in nonalcoholic fatty liver disease progression by affecting intestinal homeostasis

Nonalcoholic fatty liver disease (NAFLD) is a chronic liver disease with a pathogenesis that has not been fully elucidated. With the development of the theory of the gut-liver axis and the deepening of related research, the role of the intestinal tract in the pathogenesis of NAFLD has been investigated more. Intestinal microbiota, intestinal metabolites, and intestinal epithelial and immune-based barriers constitute the intestinal environment, which uses crosstalk to maintain the homeostasis of the intestinal environment. This paper reviews the progress in the study of intestinal microbiota, intestinal environment, and NAFLD and suggests that repair of intestinal functional balance may be a new idea for early prevention and intervention of NAFLD.

Brain-gut-liver interactions across the spectrum of insulin resistance in metabolic fatty liver disease

Metabolic associated fatty liver disease (MAFLD), formerly named "nonalcoholic fatty liver disease" occurs in about one-third of the general population of developed countries worldwide and behaves as a major morbidity and mortality risk factor for major causes of death, such as cardiovascular, digestive, metabolic, neoplastic and neuro-degenerative diseases. However, progression of MAFLD and its associated systemic complications occur almost invariably in patients who experience the additional burden of intrahepatic and/or systemic inflammation, which acts as disease accelerator. Our review is focused on the new knowledge about the brain-gut-liver axis in the context of metabolic dysregulations associated with fatty liver, where insulin resistance has been assumed to play an important role. Special emphasis has been given to digital imaging studies and in particular to positron emission tomography, as it represents a unique opportunity for the noninvasive in vivo study of tissue metabolism. An exhaustive revision of targeted animal models is also provided in order to clarify what the available preclinical evidence suggests for the causal interactions between fatty liver, dysregulated endogenous glucose production and insulin resistance.

Porphyran-derived oligosaccharides alleviate NAFLD and related cecal microbiota dysbiosis in mice

Porphyran and its derivatives possess a variety of biological activities, such as ameliorations of oxidative stress, inflammation, hyperlipemia, and immune deficiencies. In this study, we evaluated the potential efficacy of porphyran-derived oligosaccharides from Porphyra yezoensis (PYOs) in alleviating nonalcoholic fatty liver disease (NAFLD) and preliminarily clarified the underlying mechanism. NAFLD was induced by a high-fat diet for six months in C57BL/6J mice, followed by treatment with PYOs (100 or 300 mg/kg/d) for another six weeks. We found that PYOs reduced hepatic oxidative stress in mice with NAFLD, which plays a critical role in the occurrence and development of NAFLD. In addition, PYOs could markedly decrease lipid accumulation in liver by activating the IRS-1/AKT/GSK-3β signaling pathway and the AMPK signaling pathway in mice with NAFLD. PYOs also apparently relieved the hepatic fibrosis induced by oxidative stress via downregulation of TGF-β and its related proteins, so that liver injury was markedly alleviated. Furthermore, PYOs treatment relieved cecal microbiota dysbiosis (such as increasing the relative abundance of Akkermansia, while decreasing the Helicobacter abundance), which could alleviate oxidative stress, inflammation, and lipid metabolism, and protect the liver to a certain degree. In summary, PYOs treatment remarkably improved NAFLD via a specific molecular mechanism and reshaped the cecal microbiota.

Recipient factors in faecal microbiota transplantation: one stool does not fit all

Faecal microbiota transplantation (FMT) is a promising therapy for chronic diseases associated with gut microbiota alterations. FMT cures 90% of recurrent Clostridioides difficile infections. However, in complex diseases, such as inflammatory bowel disease, irritable bowel syndrome and metabolic syndrome, its efficacy remains variable. It is accepted that donor selection and sample administration are key determinants of FMT success, yet little is known about the recipient factors that affect it. In this Perspective, we discuss the effects of recipient parameters, such as genetics, immunity, microbiota and lifestyle, on donor microbiota engraftment and clinical efficacy. Emerging evidence supports the possibility that controlling inflammation in the recipient intestine might facilitate engraftment by reducing host immune system pressure on the newly transferred microbiota. Deciphering FMT engraftment rules and developing novel therapeutic strategies are priorities to alleviate the burden of chronic diseases associated with an altered gut microbiota such as inflammatory bowel disease.

Pathogenetic mechanisms of nonalcoholic fatty liver disease and inhibition of the inflammasome as a new therapeutic target

Nonalcoholic fatty liver disease (NAFLD) is the most common chronic liver disease worldwide, and its incidence is increasing. Nonalcoholic steatohepatitis (NASH), the progressive form of the disease, can lead to end-stage liver disease. The pathogenesis of the disease is not fully understood, and there is currently no specific treatment. Therefore, an effective and reliable treatment modality is needed. In recent years, the inflammasome has been shown to play a vital role in many stages of NAFLD pathogenesis. In particular, the detection, by toll-like receptors, of pathogen-associated molecular patterns induced by the gut-liver axis triggers the formation of the NLRP3 (NLR family pyrin domain-containing protein 3) inflammasome. Stimulation of damage-associated molecular patterns also activates the NLRP3 inflammasome. The activated inflammasome has caspase-1 activity, which leads to the release of interleukin (IL)-1 and IL-18 and formation of pores in the cell wall. This process spreads the inflammatory process to the outside of the cell and induces inflammatory cell death (pyroptosis). Subsequent progression of the inflammatory process leads to fibrosis. Recent evidence suggests that the NLRP3 inflammasome may be a potential target for the treatment of NASH. The discovery of specific NLRP3 inflammasome blockers in recent years and evidence of their positive effects in experimental models support this therapeutic approach. In this article, we discuss recent evidence on the pathogenesis of NAFLD, the role of the inflammasome in the pathogenesis of NAFLD, and the potential effects of inhibition of the inflammasome.

Dysbiosis of gut microbiota after cholecystectomy is associated with non-alcoholic fatty liver disease in mice

Increasing evidence suggests that cholecystectomy is an independent risk factor for non‐alcoholic fatty liver disease (NAFLD). However, the underlying mechanisms that lead to hepatic lipid deposition after cholecystectomy are unclear. In this study, adult male C57BL/6J mice that underwent a cholecystectomy or sham operation were fed either a high‐fat diet (HFD) or a chow diet for 56 days. Significantly increased steatohepatitis, liver/body weight ratio, hepatic triglycerides, and glucose intolerance were observed in postcholecystectomy mice fed the HFD. Notable alterations in the composition of gut microbiota after cholecystectomy were observed in both HFD‐ and chow‐diet‐fed mice. Our results indicate that cholecystectomy alters the gut microbiota profile, which might contribute to the development of NAFLD in mice.

Engraftment of Bacteria after Fecal Microbiota Transplantation Is Dependent on Both Frequency of Dosing and Duration of Preparative Antibiotic Regimen

The gut microbiota has emerged as a key mediator of human physiology, and germ-free mice have been essential in demonstrating a role for the microbiome in disease. Preclinical models using conventional mice offer the advantage of working with a mature immune system. However, optimal protocols for fecal microbiota transplant (FMT) engraftment in conventional mice are yet to be established. Conventional BALB/c mice were randomized to receive 3-day (3d) or 3-week (3w) antibiotic (ABX) regimen in their drinking water followed by 1 or 5-daily FMTs from a human donor. Fecal samples were collected longitudinally and characterized using 16S ribosomal RNA (rRNA) sequencing. Semi-targeted metabolomic profiling of fecal samples was also done with liquid chromatography-mass spectrometry (LC-MS). Lastly, we sought to confirm our findings in BKS mice. Recovery of baseline diversity scores were greatest in the 3d groups, driven by re-emergence of mouse commensal microbiota, whereas the most resemblance to donor microbiota was seen in the 3w + 5-FMT group. Amplicon sequence variants (ASVs) that were linked to the input material (human ASVs) engrafted to a significantly greater extent when compared to mouse ASVs in the 3-week groups but not the 3-day groups. Lastly, comparison of metabolomic profiles revealed distinct functional profiles by ABX regimen. These results indicate successful model optimization and emphasize the importance of ABX duration and frequency of FMT dosing; the most stable and reliable colonization by donor ASVs was seen in the 3wk + 5-FMT group.

Recent Progress in Metabolic Syndrome Research and Therapeutics

Metabolic syndrome (MetS) is a well-defined yet difficult-to-manage disease entity. Both the precipitous rise in its incidence due to contemporary lifestyles and the growing heterogeneity among affected populations present unprecedented challenges. Moreover, the predisposed risk for developing severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection in populations with MetS, and the viral impacts on host metabolic parameters, underscores the need to investigate this mechanism thoroughly. Recent investigations of metabolomics and proteomics have revealed not only differentially expressed substances in MetS, but also the consequences of diet consumption and physical activity on energy metabolism. These variations in metabolites, as well as protein products, also influence a wide spectrum of host characteristics, from cellular behavior to phenotype. Research on the dysregulation of gut microbiota and the resultant inflammatory status has also contributed to our understanding of the underlying pathogenic mechanisms. As for state-of-the-art therapies, advancing depictions of the bio-molecular landscape of MetS have emerged and now play a key role in individualized precision medicine. Fecal microbiota transplantation, aiming to restore the host's homeostasis, and targeting of the bile acid signaling pathway are two approaches to combatting MetS. Comprehensive molecular inquiries about MetS by omics measures are mandatory to facilitate the development of novel therapeutic modalities.

Research progress on intervention effect and mechanism of protocatechuic acid on nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) has become a surge burden worldwide due to its high prevalence, with complicated deterioration symptoms such as liver fibrosis and cancer. No effective drugs are available for NALFD so far. The rapid growth of clinical demand has prompted the treatment of NAFLD to become a research hotspot. Protocatechuic acid (PCA) is a natural secondary metabolite commonly found in fruits, vegetables, grains, and herbal medicine. It is also the major internal metabolites of anthocyanins and other polyphenols. In the present manuscript, food sources, metabolic absorption, and efficacy of PCA were summarized while analyzing its role in improving NAFLD, as well as the mechanism involved. The results indicated that PCA could ameliorate NAFLD by regulating glucose and lipid metabolism, oxidative stress and inflammation, gut microbiota and metabolites. It was proposed for the first time that PCA might reduce NAFLD by enhancing the energy consumption of brown adipose tissue (BAT). However, the PCA administration mode and dose for NAFLD remain inconclusive. Fresh insights into the specific molecular mechanisms are required, while clinical trials are essential in the future. This review provides new targets and reasoning for the clinical application of PCA in the prevention and treatment of NAFLD.

Nonalcoholic Fatty Liver Disease (NAFLD) as Model of Gut-Liver Axis Interaction: From Pathophysiology to Potential Target of Treatment for Personalized Therapy

Nonalcoholic fatty liver disease (NAFLD) is the leading cause of liver disease worldwide, affecting both adults and children and will result, in the near future, as the leading cause of end-stage liver disease. Indeed, its prevalence is rapidly increasing, and NAFLD is becoming a major public health concern. For this reason, great efforts are needed to identify its pathogenetic factors and new therapeutic approaches. In the past decade, enormous advances understanding the gut-liver axis-the complex network of cross-talking between the gut, microbiome and liver through the portal circulation-have elucidated its role as one of the main actors in the pathogenesis of NAFLD. Indeed, evidence shows that gut microbiota is involved in the development and progression of liver steatosis, inflammation and fibrosis seen in the context of NAFLD, as well as in the process of hepatocarcinogenesis. As a result, gut microbiota is currently emerging as a non-invasive biomarker for the diagnosis of disease and for the assessment of its severity. Additionally, to its enormous diagnostic potential, gut microbiota is currently studied as a therapeutic target in NAFLD: several different approaches targeting the gut homeostasis such as antibiotics, prebiotics, probiotics, symbiotics, adsorbents, bariatric surgery and fecal microbiota transplantation are emerging as promising therapeutic options.

Gut microbiota-derived metabolites as central regulators in metabolic disorders

Metabolic disorders represent a growing worldwide health challenge due to their dramatically increasing prevalence. The gut microbiota is a crucial actor that can interact with the host by the production of a diverse reservoir of metabolites, from exogenous dietary substrates or endogenous host compounds. Metabolic disorders are associated with alterations in the composition and function of the gut microbiota. Specific classes of microbiota-derived metabolites, notably bile acids, short-chain fatty acids, branched-chain amino acids, trimethylamine N-oxide, tryptophan and indole derivatives, have been implicated in the pathogenesis of metabolic disorders. This review aims to define the key classes of microbiota-derived metabolites that are altered in metabolic diseases and their role in pathogenesis. They represent potential biomarkers for early diagnosis and prognosis as well as promising targets for the development of novel therapeutic tools for metabolic disorders.

Contribution of gut microbiota to nonalcoholic fatty liver disease: Pathways of mechanisms

BACKGROUND & AIMS

Non-alcoholic fatty liver disease (NAFLD) is a common, multifactorial liver disease with rapidly increasing prevalence. During the past decade, several lines of evidence have suggested that gut microbiota dysbiosis represents a major factor contributing to NAFLD occurrence and its progression.

METHOD

We have performed a review of the published data on the relationship between gut microbiota and risk factors for NAFLD and the role that gut-liver axis plays in the pathogenesis of NAFLD.

RESULTS

Accumulated evidence has indicated that dysfunction of the gut-liver axis, including increased intestinal permeability, small intestinal bacterial overgrowth, microbiota-derived mediators, and intestinal dysbiosis contribute to the progression and development of NAFLD.

CONCLUSIONS

The findings of this review suggest that lifestyle modification and manipulation of gut microbiota can be considered as a therapeutic target for NAFLD management. However, important documents supporting the role of gut microbiota in NAFLD come from animal studies; therefore, information from studies on humans could lead to novel therapeutics for this highly common disorder.

Treating the Metabolic Syndrome by Fecal Transplantation-Current Status

The intestinal microbiome (IM) is important for normal gastrointestinal (GI) and other organ systems' functioning. An alteration in the normal IM, dysbiosis, and changes in intestinal motility result in microorganisms' overgrowth and an alteration in intestinal permeability. The gut-brain axis is also of importance in the irritable bowel syndrome (IBS) and associated bowel overgrowth. Secondary to the epidemic of obesity, the metabolic syndrome has become a major health problem. Disturbances in the fecal microbiome are associated with the metabolic syndrome. Metabolic-associated fatty liver disease (MAFLD) is now the current terminology for non-alcoholic fatty liver disease. IM alteration by fecal transplantation is an approved treatment method for recurrent Clostridioides difficile infection. Initially performed by either duodenal infusion or colonoscopy, it is now easily performed by the administration of capsules containing stools. We discuss the intestinal microbiome-its composition, as well as the qualitative changes of microbiome composition leading to inflammation. In addition, we discuss the evidence of the effect of fecal transplantation on the metabolic syndrome and MAFLD, as well as its clinical indications.

Pediatric nonalcoholic fatty liver disease and the microbiome: Mechanisms contributing to pathogenesis and progression

Nonalcoholic fatty liver disease (NAFLD) is the most common form of pediatric liver disease in the United States, and often associated with obesity and metabolic syndrome. NAFLD comprises a broad spectrum of liver diseases, from hepatic steatosis to steatohepatitis, fibrosis and cirrhosis. Disease progression is considered a multi-modal process of liver injury. The intestinal microbiome has been implicated in several aspects of NAFLD pathophysiology. Pediatric studies associating the intestinal microbiome with NAFLD have been limited in number and complicated by inconsistencies in study design and approach. Nevertheless, they provide support for involvement of the intestinal microbiome in NAFLD development and progression and point to common mechanisms shared by microbiome-associated inflammatory diseases with potential to inform future therapeutic intervention.

Partially hydrolyzed guar gum attenuates non-alcoholic fatty liver disease in mice through the gut-liver axis

BACKGROUND

The gut-liver axis has attracted much interest in the context of chronic liver disease pathogenesis. Prebiotics such as dietary fibers were shown to attenuate non-alcoholic fatty liver disease (NAFLD) by modulating gut microbiota. Partially hydrolyzed guar gum (PHGG), a water-soluble dietary fiber, has been reported to alleviate the symptoms of various intestinal diseases and metabolic syndromes. However, its effects on NAFLD remain to be fully elucidated.

AIM

To determine whether treatment with PHGG attenuates NAFLD development in mice through the gut-liver axis.

METHODS

Seven-week-old male C57BL/6J mice with increased intestinal permeability were fed a control or atherogenic (Ath) diet (a mouse model of NAFLD) for 8 wk, with or without 5% PHGG. Increased intestinal permeability was induced through chronic intermittent administration of low-dose dextran sulfate sodium. Body weight, liver weight, macroscopic findings in the liver, blood biochemistry [aspartate aminotransferase (AST) and alanine aminotransferase (ALT), total cholesterol, triglyceride, free fatty acids, and glucose levels], liver histology, myeloperoxidase activity in liver tissue, mRNA expression in the liver and intestine, serum endotoxin levels in the portal vein, intestinal permeability, and microbiota and short-chain fatty acid (SCFA) profiles in the cecal samples were investigated.

RESULTS

Mice with increased intestinal permeability subjected to the Ath diet showed significantly increased serum AST and ALT levels, liver fat accumulation, liver inflammatory (tumor necrosis factor-α and monocyte chemotactic protein-1) and fibrogenic (collagen 1a1 and α smooth muscle actin) marker levels, and liver myeloperoxidase activity, which were significantly attenuated by PHGG treatment. Furthermore, the Ath diet combined with increased intestinal permeability resulted in elevated portal endotoxin levels and activated toll-like receptor (TLR) 4 and TLR9 expression, confirming that intestinal permeability was significantly elevated, as observed by evaluating the lumen-to-blood clearance of fluorescein isothiocyanate-conjugated dextran. PHGG treatment did not affect fatty acid metabolism in the liver. However, it decreased lipopolysaccharide signaling through the gut-liver axis. In addition, it significantly increased the abundance of cecal Bacteroides and Clostridium subcluster XIVa. Treatment with PHGG markedly increased the levels of SCFAs, particularly, butyric acid, acetic acid, propionic acid, and formic acid, in the cecal samples.

CONCLUSION

PHGG partially prevented NAFLD development in mice through the gut-liver axis by modulating microbiota and downstream SCFA profiles.

Non-Alcoholic Fatty Liver Disease: Metabolic, Genetic, Epigenetic and Environmental Risk Factors

Non-alcoholic fatty liver disease (NAFLD) is one of the most frequent causes of chronic liver disease in the Western world, probably due to the growing prevalence of obesity, metabolic diseases, and exposure to some environmental agents. In certain patients, simple hepatic steatosis can progress to non-alcoholic steatohepatitis (NASH), which can sometimes lead to liver cirrhosis and its complications including hepatocellular carcinoma. Understanding the mechanisms that cause the progression of NAFLD to NASH is crucial to be able to control the advancement of the disease. The main hypothesis considers that it is due to multiple factors that act together on genetically predisposed subjects to suffer from NAFLD including insulin resistance, nutritional factors, gut microbiota, and genetic and epigenetic factors. In this article, we will discuss the epidemiology of NAFLD, and we overview several topics that influence the development of the disease from simple steatosis to liver cirrhosis and its possible complications.

Human Gut Microbiome and Liver Diseases: From Correlation to Causation

The important role of human gut microbiota in liver diseases has long been recognized as dysbiosis and the translocation of certain microbes from the gut to liver. With the development of high-throughput DNA sequencing, the complexity and integrity of the gut microbiome in the whole spectrum of liver diseases is emerging. Specific patterns of gut microbiota have been identified in liver diseases with different causes, including alcoholic, non-alcoholic, and virus induced liver diseases, or even at different stages, ranging from steatohepatitis, fibrosis, cirrhosis, to hepatocellular carcinoma. At the same time, the mechanism of how microbiota contributes to liver diseases goes beyond the traditional function of the gut-liver axis which could lead to liver injury and inflammation. With the application of proteomics, metabolomics, and modern molecular technologies, more microbial metabolites and the complicated interaction of microbiota with host immunity come into our understanding in the liver pathogenesis. Germ-free animal models serve as a workhorse to test the function of microbiota and their derivatives in liver disease models. Here, we review the current evidence on the relationship between gut microbiota and liver diseases, and the mechanisms underlying this phenotype. In addition to original liver diseases, gut microbiota might also affect liver injury in systemic disorders involving multiple organs, as in the case of COVID-19 at a severe state. A better understanding of the gut microbial contribution to liver diseases might help us better benefit from this guest-host relationship and pave the way for novel therapies.

Gut-Liver Axis in Nonalcoholic Fatty Liver Disease: the Impact of the Metagenome, End Products, and the Epithelial and Vascular Barriers

Nonalcoholic fatty liver disease (NAFLD) is a systemic, dynamic, heterogeneous, and multiaxis entity, the pathogenesis of which is still uncertain. The gut-liver axis is regulated and stabilized by a complex network encompassing a metabolic, immune, and neuroendocrine cross-talk between the gut, the microbiota, and the liver. Changes in the gut-liver axis affect the metabolism of lipids and carbohydrates in the hepatocytes, and they impact the balance of inflammatory mediators and cause metabolic deregulation, promoting NAFLD and its progression to nonalcoholic steatohepatitis. Moreover, the microbiota and its metabolites can play direct and indirect roles in gut barrier function and fibrosis development. In this review, we will highlight findings from the recent literature focusing on the gut-liver axis and its relation to NAFLD. Finally, we will discuss the impact of technical issues, design bias, and other limitations on current knowledge of the gut microbiota in the context of NAFLD.

Targeting the gut-liver-immune axis to treat cirrhosis

Cirrhotic portal hypertension is characterised by development of the decompensating events of ascites, encephalopathy, portal hypertensive bleeding and hepatorenal syndrome, which arise in a setting of cirrhosis-associated immune dysfunction (CAID) and define morbidity and prognosis. CAID describes the dichotomous observations that systemic immune cells are primed and display an inflammatory phenotype, while failing to mount robust responses to pathogen challenge. Bacterial infections including spontaneous bacterial peritonitis are common complications of advanced chronic liver disease and can precipitate variceal haemorrhage, hepatorenal syndrome and acute-on-chronic liver failure; they frequently arise from gut-derived organisms and are closely linked with dysbiosis of the commensal intestinal microbiota in advanced chronic liver disease.Here, we review the links between cirrhotic dysbiosis, intestinal barrier dysfunction and deficits of host-microbiome compartmentalisation and mucosal immune homoeostasis that occur in settings of advanced chronic liver disease. We discuss established and emerging therapeutic strategies targeted at restoring intestinal eubiosis, augmenting gut barrier function and ameliorating the mucosal and systemic immune deficits that characterise and define the course of decompensated cirrhosis.

The interaction between the gut microbiota and dietary carbohydrates in nonalcoholic fatty liver disease

Imbalance between fat production and consumption causes various metabolic disorders. Nonalcoholic fatty liver disease (NAFLD), one such pathology, is characterized by abnormally increased fat synthesis and subsequent fat accumulation in hepatocytes1,2. While often comorbid with obesity and insulin resistance, this disease can also be found in lean individuals, suggesting specific metabolic dysfunction2. NAFLD has become one of the most prevalent liver diseases in adults worldwide, but its incidence in both children and adolescents has also markedly increased in developed nations3,4. Progression of this disease into nonalcoholic steatohepatitis (NASH), cirrhosis, liver failure, and hepatocellular carcinoma in combination with its widespread incidence thus makes NAFLD and its related pathologies a significant public health concern. Here, we review our understanding of the roles of dietary carbohydrates (glucose, fructose, and fibers) and the gut microbiota, which provides essential carbon sources for hepatic fat synthesis during the development of NAFLD.

Ochratoxin A: its impact on poultry gut health and microbiota, an overview

Ochratoxin A (OTA) is a widespread mycotoxin, that has strong thermal stability, and is difficult to remove from feed. OTA is nephrotoxic, hepatotoxic, teratogenic, immunotoxic, and enterotoxic to several species of animals. The gut is the first defense barrier against various types of mycotoxins present in feed that enter the body, and it is closely connected to other tissues through enterohepatic circulation. Compared with mammals, poultry is more sensitive to OTA and has a lower absorption rate. Therefore, the gut is an important target tissue for OTA in poultry. This review comprehensively discusses the role of OTA in gut health and the gut microbiota of poultry, focusing on the effect of OTA on digestive and absorptive processes, intestinal barrier integrity, intestinal histomorphology, gut immunity, and gut microbiota. According to the studies described to date, OTA can affect gut dysbiosis, including increasing gut permeability, immunity, and bacterial translocation, and can eventually lead to gut and other organ injury. Although there are many studies investigating the effects of OTA on the gut health of poultry, further studies are needed to better characterize the underlying mechanisms of action and develop preventative or therapeutic interventions for mycotoxicosis in poultry.

Proton pump inhibitors use and the risk of fatty liver disease: A nationwide cohort study

BACKGROUND AND AIM

Proton pump inhibitor (PPI)-induced hypochondria can change the composition of the gut microbiota, inducing overgrowth of small bowel bacteria, which has been suggested to promote the development of fatty liver disease through the gut-liver axis. In this study, we aimed to investigate the association between PPI use and the risk of fatty liver disease.

METHODS

A retrospective cohort study was conducted using the Korean National Health Insurance Service-National Sample Cohort, a nationwide population-based representative sample, from January 1, 2002, to December 31, 2015. PPI use was identified from treatment claims and considered as a time-varying variable.

RESULTS

During 1 463 556 person-years of follow-up, 75 727 patients had at least one PPI prescription, and 3735 patients developed fatty liver disease. The hazard ratio for fatty liver disease comparing PPI users with non-PPI users was 1.68 (95% confidence interval, 1.61-1.75). When adjusted for multiple confounders, including age, sex, body mass index, smoking, alcohol intake, exercise, income level, and comorbidities, the association was still significant (hazard ratio, 1.50; 95% confidence interval, 1.44-1.57). After considering the amounts of PPIs stratified by cumulative defined daily dose, the dose-response effect was observed until 180 days. Subgroup analysis also revealed that PPI use was correlated to an increased risk of fatty liver disease.

CONCLUSIONS

This current national wide cohort study suggests that PPI use was associated with an increased risk of fatty liver disease compared with non-use of PPIs. Clinicians should consider fatty liver as a potential risk when prescribing PPI.

Oral-Gut Microbiome Axis in Gastrointestinal Disease and Cancer

It is well-known that microbiota dysbiosis is closely associated with numerous diseases in the human body. The oral cavity and gut are the two largest microbial habitats, playing a major role in microbiome-associated diseases. Even though the oral cavity and gut are continuous regions connected through the gastrointestinal tract, the oral and gut microbiome profiles are well-segregated due to the oral-gut barrier. However, the oral microbiota can translocate to the intestinal mucosa in conditions of the oral-gut barrier dysfunction. Inversely, the gut-to-oral microbial transmission occurs as well in inter- and intrapersonal manners. Recently, it has been reported that oral and gut microbiomes interdependently regulate physiological functions and pathological processes. Oral-to-gut and gut-to-oral microbial transmissions can shape and/or reshape the microbial ecosystem in both habitats, eventually modulating pathogenesis of disease. However, the oral-gut microbial interaction in pathogenesis has been underappreciated to date. Here, we will highlight the oral-gut microbiome crosstalk and its implications in the pathogenesis of the gastrointestinal disease and cancer. Better understanding the role of the oral-gut microbiome axis in pathogenesis will be advantageous for precise diagnosis/prognosis and effective treatment.

Overview of Non-Alcoholic Fatty Liver Disease (NAFLD) and the Role of Sugary Food Consumption and Other Dietary Components in Its Development

NAFLD is the world's most common chronic liver disease, and its increasing prevalence parallels the global rise in diabetes and obesity. It is characterised by fat accumulation in the liver evolving to non-alcoholic steatohepatitis (NASH), an inflammatory subtype that can lead to liver fibrosis and cirrhosis. Currently, there is no effective pharmacotherapeutic treatment for NAFLD. Treatment is therefore based on lifestyle modifications including changes to diet and exercise, although it is unclear what the most effective form of intervention is. The aim of this review, then, is to discuss the role of specific nutrients and the effects of different dietary interventions on NAFLD. It is well established that an unhealthy diet rich in calories, sugars, and saturated fats and low in polyunsaturated fatty acids, fibre, and micronutrients plays a critical role in the development and progression of this disease. However, few clinical trials have evaluated the effects of nutrition interventions on NAFLD. We, therefore, summarise what is currently known about the effects of macronutrients, foods, and dietary patterns on NAFLD prevention and treatment. Most current guidelines recommend low-calorie, plant-based diets, such as the Mediterranean diet, as the most effective dietary pattern to treat NAFLD. More clinical trials are required, however, to identify the best evidence-based dietary treatment approach.

Faecal microbial metabolites of proteolytic and saccharolytic fermentation in relation to degree of insulin resistance in adult individuals

The gut microbiota may affect host metabolic health through microbial metabolites. The balance between the production of microbial metabolites by saccharolytic and proteolytic fermentation may be an important determinant of metabolic health. Amongst the best-studied saccharolytic microbial metabolites are the short-chain fatty acids acetate, propionate and butyrate. However, human data on the role of other microbial fermentation by-products in metabolic health are greatly lacking. Therefore, we compared in a cross-sectional study the faecal microbial metabolites (caproate, lactate, valerate, succinate, and the branched-chain fatty acids (BCFA) (isobutyrate, isovalerate)) between insulin sensitive (homeostatic model assessment of insulin resistance (HOMA-IR), HOMA-IR<1.85, IS) and insulin resistant (HOMA-IR>1.85, IR) individuals. Additionally, we assessed the relationships between faecal metabolites and markers of metabolic health including fasting glucose, insulin, free fatty acids, insulin resistance (HOMA-IR) and fasting substrate oxidation in 86 individuals with a wide range of body mass index. Faecal metabolite concentrations did not significantly differ between IS and IR. Furthermore, there were no associations between microbial metabolites and metabolic health markers, except for a slight positive association of isovalerate with carbohydrate oxidation (E%, std β 0.194, P=0.011) and fat oxidation (E%, std β -0.075, P=0.047), also after adjustment for age, sex and BMI. In summary, faecal caproate, lactate, valerate, succinate, and BCFA (isobutyrate, isovalerate) were not different between IR and IS individuals, nor was there any association between these faecal metabolites and parameters of metabolic health. Further human intervention studies are warranted to investigate the role of these microbially-derived fermentation products and their kinetics in metabolic health and insulin sensitivity.

Dietary Strategies for Management of Metabolic Syndrome: Role of Gut Microbiota Metabolites

Metabolic syndrome (MetS) is a complex pathophysiological state with incidence similar to that of a global epidemic and represents a risk factor for the onset of chronic non-communicable degenerative diseases (NCDDs), including cardiovascular disease (CVD), type 2 diabetes mellitus, chronic kidney disease, and some types of cancer. A plethora of literature data suggest the potential role of gut microbiota in interfering with the host metabolism, thus influencing several MetS risk factors. Perturbation of the gut microbiota’s composition and activity, a condition known as dysbiosis, is involved in the etiopathogenesis of multiple chronic diseases. Recent studies have shown that some micro-organism-derived metabolites (including trimethylamine N-oxide (TMAO), lipopolysaccharide (LPS) of Gram-negative bacteria, indoxyl sulfate and p-cresol sulfate) induce subclinical inflammatory processes involved in MetS. Gut microbiota’s taxonomic species or abundance are modified by many factors, including diet, lifestyle and medications. The main purpose of this review is to highlight the correlation between different dietary strategies and changes in gut microbiota metabolites. We mainly focus on the validity/inadequacy of specific dietary patterns to reduce inflammatory processes, including leaky gut and subsequent endotoxemia. We also describe the chance of probiotic supplementation to interact with the immune system and limit negative consequences associated with MetS.

The pregnane X receptor drives sexually dimorphic hepatic changes in lipid and xenobiotic metabolism in response to gut microbiota in mice

BACKGROUND

The gut microbiota-intestine-liver relationship is emerging as an important factor in multiple hepatic pathologies, but the hepatic sensors and effectors of microbial signals are not well defined.

RESULTS

By comparing publicly available liver transcriptomics data from conventional vs. germ-free mice, we identified pregnane X receptor (PXR, NR1I2) transcriptional activity as strongly affected by the absence of gut microbes. Microbiota depletion using antibiotics in Pxr^+/+ vs Pxr^-/- C57BL/6J littermate mice followed by hepatic transcriptomics revealed that most microbiota-sensitive genes were PXR-dependent in the liver in males, but not in females. Pathway enrichment analysis suggested that microbiota-PXR interaction controlled fatty acid and xenobiotic metabolism. We confirmed that antibiotic treatment reduced liver triglyceride content and hampered xenobiotic metabolism in the liver from Pxr^+/+ but not Pxr^-/- male mice.

CONCLUSIONS

These findings identify PXR as a hepatic effector of microbiota-derived signals that regulate the host's sexually dimorphic lipid and xenobiotic metabolisms in the liver. Thus, our results reveal a potential new mechanism for unexpected drug-drug or food-drug interactions. Video abstract.

The Role of the Gut-Liver Axis in Metabolic Dysfunction-Associated Fatty Liver Disease

The complex interplay between the gut microbiota, the intestinal barrier, the immune system and the liver is strongly influenced by environmental and genetic factors that can disrupt the homeostasis leading to disease. Among the modulable factors, diet has been identified as a key regulator of microbiota composition in patients with metabolic syndrome and related diseases, including the metabolic dysfunction-associated fatty liver disease (MAFLD). The altered microbiota disrupts the intestinal barrier at different levels inducing functional and structural changes at the mucus lining, the intercellular junctions on the epithelial layer, or at the recently characterized vascular barrier. Barrier disruption leads to an increased gut permeability to bacteria and derived products which challenge the immune system and promote inflammation. All these alterations contribute to the pathogenesis of MAFLD, and thus, therapeutic approaches targeting the gut-liver-axis are increasingly being explored. In addition, the specific changes induced in the intestinal flora may allow to characterize distinctive microbial signatures for non-invasive diagnosis, severity stratification and disease monitoring.

Non-Alcoholic Fatty Liver Disease in Obese Youth With Insulin Resistance and Type 2 Diabetes

Currently, Non-Alcoholic Fatty Liver Disease (NAFLD) is the most prevalent form of chronic liver disease in children and adolescents worldwide. Simultaneously to the epidemic spreading of childhood obesity, the rate of affected young has dramatically increased in the last decades with an estimated prevalence of NAFLD of 3%-10% in pediatric subjects in the world. The continuous improvement in NAFLD knowledge has significantly defined several risk factors associated to the natural history of this complex liver alteration. Among them, Insulin Resistance (IR) is certainly one of the main features. As well, not surprisingly, abnormal glucose tolerance (prediabetes and diabetes) is highly prevalent among children/adolescents with biopsy-proven NAFLD. In addition, other factors such as genetic, ethnicity, gender, age, puberty and lifestyle might affect the development and progression of hepatic alterations. However, available data are still lacking to confirm whether IR is a risk factor or a consequence of hepatic steatosis. There is also evidence that NAFLD is the hepatic manifestation of Metabolic Syndrome (MetS). In fact, NAFLD often coexist with central obesity, impaired glucose tolerance, dyslipidemia, and hypertension, which represent the main features of MetS. In this Review, main aspects of the natural history and risk factors of the disease are summarized in children and adolescents. In addition, the most relevant scientific evidence about the association between NAFLD and metabolic dysregulation, focusing on clinical, pathogenetic, and histological implication will be provided with some focuses on the main treatment options.

Oral–Gut Microbiome Axis in Gastrointestinal Disease and Cancer

It is well-known that microbiota dysbiosis is closely associated with numerous diseases in the human body. The oral cavity and gut are the two largest microbial habitats, playing a major role in microbiome-associated diseases. Even though the oral cavity and gut are continuous regions connected through the gastrointestinal tract, the oral and gut microbiome profiles are well-segregated due to the oral–gut barrier. However, the oral microbiota can translocate to the intestinal mucosa in conditions of the oral–gut barrier dysfunction. Inversely, the gut-to-oral microbial transmission occurs as well in inter- and intrapersonal manners. Recently, it has been reported that oral and gut microbiomes interdependently regulate physiological functions and pathological processes. Oral-to-gut and gut-to-oral microbial transmissions can shape and/or reshape the microbial ecosystem in both habitats, eventually modulating pathogenesis of disease. However, the oral–gut microbial interaction in pathogenesis has been underappreciated to date. Here, we will highlight the oral–gut microbiome crosstalk and its implications in the pathogenesis of the gastrointestinal disease and cancer. Better understanding the role of the oral–gut microbiome axis in pathogenesis will be advantageous for precise diagnosis/prognosis and effective treatment.

The Role of Gut Microbiota in Duodenal-Jejunal Bypass Surgery-Induced Improvement of Hepatic Steatosis in HFD-Fed Rats

Bariatric surgery including duodenal-jejunal bypass surgery (DJB) improves insulin sensitivity and reduces obesity-associated inflammation. However, the underlying mechanism for such an improvement is still incompletely understood. Our objective was to investigate the role of the gut microbiota in DJB-associated improvement of hepatic steatosis in high fat diet (HFD)-fed rats. To study this, hepatic steatosis was induced in male adult Sprague-Dawley rats by feeding them with a 60% HFD. At 8 weeks after HFD feeding, the rats were subjected to either DJB or sham operation. HFD was resumed 1 week after the surgery for 3 more weeks. In additional groups of animals, feces were collected from HFD-DJB rats at 2 weeks after DJB. These feces were then transplanted to HFD-fed rats without DJB at 8 weeks after HFD feeding. Hepatic steatosis and fecal microbiota were analyzed at 4 weeks after surgery or fecal transplantation. Our results showed that DJB alleviated hepatic steatosis in HFD-fed rats. Fecal microbiota analysis showed that HFD-fed and standard diet-fed rats clustered differently. DJB induced substantial compositional changes in the gut microbiota. The fecal microbiota of HFD-fed rats received fecal transplant from DJB rats overlapped with that of HFD-DJB rats. Treatment of rats with HFD-induced liver lesions by fecal transplant from DJB-operated HFD-fed rats also attenuated hepatic steatosis. Thus, alterations in the gut microbiota after DJB surgery are sufficient to attenuate hepatic steatosis in HFD-fed rats. Targeting the gut microbiota could be a promising approach for preventing or treating human NAFLD.

Purple grumixama anthocyanins (Eugenia brasiliensis Lam.) attenuate obesity and insulin resistance in high-fat diet mice

Some polyphenols have been reported to modulate the expression of several genes related to lipid metabolism and insulin signaling, ameliorating metabolic disorders. We investigated the potential for the polyphenols of two varieties of grumixama, the purple fruit rich in anthocyanins and the yellow fruit, both also rich in ellagitannins, to attenuate obesity-associated metabolic disorders. Mice were fed a high fat and high sucrose diet, supplemented daily with yellow and purple extracts (200 mg per kg of body weight) for eight weeks. Purple grumixama supplementation was found to decrease body weight gain, improve insulin sensitivity and glucose-induced hyperinsulinemia, and reduce hepatic triglyceride accumulation. A decrease in intrahepatic lipids in mice treated with the purple grumixama extract was associated with lipid metabolism modulation by the PPAR signaling pathway. LPL, ApoE, and LDLr were found to be down-regulated, while Acox1 and ApoB were found to be upregulated. Some of these genes were also modulated by the yellow extract. In addition, both extracts decreased oGTT and plasma LPS. The results were associated with the presence of phenolic acids and urolithins. In conclusion, most likely the anthocyanins from the purple grumixama phenolic extract is responsible for reducing obesity and insulin resistance.

Crosstalk between PPARs and gut microbiota in NAFLD

Nonalcoholic fatty liver disease (NAFLD) has become the most common liver disorder in both China and worldwide. It ranges from simple steatosis and progresses over time to nonalcoholic steatohepatitis (NASH), advanced liver fibrosis, cirrhosis, or hepatocellular carcinoma(HCC). Furthermore, NAFLD and its complications impose a huge health burden to society. The microbiota is widely connected and plays an active role in human physiology and pathology, and it is a hidden 'organ' in determining the state of the host, in terms of homeostasis, or disease. Peroxisome proliferator-activated receptors (PPARs) are members of the nuclear receptorsuperfamily and can regulate multiple pathways involved in metabolism, and serve as effective targets forthe treatment of many types of metabolic syndromes, including NAFLD. The purpose of this review is to integrate related articles on gut microbiota, PPARs and NAFLD, and present a balanced overview on how the microbiota can possibly influence the development of NAFLD through PPARs.

Metabolic-associated fatty liver disease (MAFLD) in coeliac disease

BACKGROUND AND AIMS

Coeliac disease (CD) is considered a high-risk condition for developing non-alcoholic fatty liver disease (NAFLD) and other related metabolic disorders, particularly after commencing gluten-free diet (GFD). Recently, a new concept of metabolic-associated fatty liver disease (MAFLD) has been proposed to overcome the limitations of NAFLD definition. This study aimed at exploring the prevalence of NAFLD and MAFLD in CD patients at the time of CD diagnosis and after 2 years of GFD. Furthermore, we evaluated the role of PNPLA3 rs738409 in the development of NAFLD and MAFLD in the same population.

METHODS

We retrospectively enrolled all newly diagnosed CD patients who underwent clinical, laboratory and ultrasonography investigations both at diagnosis and after 2 years of follow-up. Moreover, a PNPLA3 rs738409 genotyping assay was performed.

RESULTS

Of 221 newly diagnosed CD patients, 65 (29.4%) presented NAFLD at CD diagnosis, while 32 (14.5%) met the criteria for MAFLD (k = 0.57). There were no significant differences between NAFLD and MAFLD, except for the higher rate of insulin resistance (IR) of MAFLD patients (75% vs 33.8%, P < .001). At 2 years of follow-up, 46.6% of patients developed NAFLD while 32.6% had MAFLD (k = 0.71). MAFLD subjects had higher transaminases (P = .03), LDL-cholesterol (P = .04), BMI and waist circumference and higher IR than NAFLD patients. MAFLD patients showed higher non-invasive liver fibrosis scores than NAFLD subjects (APRI = 1.43 ± 0.56 vs 0.91 ± 0.62, P < .001; NFS=-1.72 ± 1.31 vs -2.18 ± 1.41, P = .03; FIB-4 = 1.27 ± 0.77 vs 1.04 ± 0.74, P = .04). About PNPLA3 polymorphisms, at 2 years follow-up, NAFLD subjects presented a higher rate of heterozygosis (40.8%) and homozygosis (18.4%) polymorphisms than non-NAFLD (26.3% and 7.6%, respectively, P = .03 and 0.02), while no correlation between PNPLA3 polymorphisms and MAFLD was seen.

CONCLUSIONS

The new MAFLD definition better reflects the metabolic alterations following GFD in CD population. This new classification could be able to identify patients at higher risk of worse metabolic outcome, who need a close multidisciplinary approach for their multisystemic disease.

Dirty mice join the immunologist's toolkit

The microbiota is a driving force that influences host physiological functions. In this review, we discuss some of the methods that have been used in the pursuit of relevant host-microbiota interactions that control immune fitness and disease susceptibility, with a focus on dirty mice which have been recently incorporated in the immunologist's toolkit.

Leaky Gut Driven by Dysbiosis Augments Activation and Accumulation of Liver Macrophages via RIP3 Signaling Pathway in Autoimmune Hepatitis

The gut–liver axis has been increasingly recognized as a major autoimmunity modulator. However, the implications of intestinal barrier in the pathogenesis of autoimmune hepatitis (AIH) remain elusive. Here, we investigated the functional role of gut barrier and intestinal microbiota for hepatic innate immune response in AIH patients and murine models. In this study, we found that AIH patients displayed increased intestinal permeability and pronounced RIP3 activation of liver macrophages. In mice models, intestinal barrier dysfunction increased intestinal bacterial translocation, thus amplifying the hepatic RIP3-mediated innate immune response. Furthermore, GSK872 dampened RIP3 activation and ameliorated the activation and accumulation of liver macrophages in vitro and in vivo experiments. Strikingly, broad-spectrum antibiotic ablation significantly alleviated RIP3 activation and liver injury, highlighting the causal role of intestinal microbiota for disease progression. Our results provided a potentially novel mechanism of immune tolerance breakage in the liver via the gut-liver axis. In addition, we also explored the therapeutic and research potentials of regulating the intestinal microbiota for the therapy of AIH.

Gut Microbiota and Non-Alcoholic Fatty Liver Disease Severity in Type 2 Diabetes Patients

Introduction: Non-alcoholic fatty liver disease (NAFLD) remains an important health issue worldwide. The increasing prevalence of NAFLD is linked to type 2 diabetes (T2D). The gut microbiota is associated with the development of NAFLD and T2D. However, the relationship between gut microbiota and NAFLD severity has remained unclear in T2D patients. The aim of this study was to evaluate the relationship of gut microbiota with the severity of NAFLD in T2D patients. Methods: This cross-sectional study used transient elastography (FibroScan) to evaluate the severity of hepatic steatosis. We utilized qPCR to measure the abundance of Bacteroidetes, Firmicutes, Faecalibacterium prausnitzii, Clostridium leptum group, Bacteroides, Bifidobacterium, Akkermansia muciniphila, and Escherichia coli. Results: Of 163 T2D patients, 83 with moderate to severe NAFLD had higher abundance of bacteria of the phylum Firmicutes with respect to 80 patients without NAFLD or with mild NAFLD. High abundance of the phylum Firmicutes increased the severity of NAFLD in T2D patients. A positive correlation between NAFLD severity and the phylum Firmicutes was found in T2D male patients with body mass index ≥24 kg/m² and glycated hemoglobin <7.5%. Conclusion: Enrichment of the fecal microbiota with the phylum Firmicutes is significantly and positively associated with NAFLD severity in T2D patients. The gut microbiota is a potential predictor of NAFLD severity in T2D patients.

Effects of Different Ambient Temperatures on Caecal Microbial Composition in Broilers

Short-term or acute temperature stress affect the immune responses and alters the gut microbiota of broilers, but the influences of long-term temperature stress on stress biomarkers and the intestinal microbiota remains largely unknown. Therefore, we examined the effect of three long-term ambient temperatures (high (HC), medium (MC), and low (LC) temperature groups) on the gene expression of broilers’ heat shock proteins (Hsps) and inflammation – related genes, as well as the caecal microbial composition. The results revealed that Hsp70 and Hsp90 levels in HC group significantly increased, and levels of Hsp70, Hsp90, IL-6, TNF-α, and NFKB1 in LC group were significantly higher than in MC group (p < 0.05). In comparison with the MC group, the proportion of Firmicutes increased in HC and LC groups, while that of Bacteroidetes decreased in LC group at phylum level (p < 0.05). At genus level, the proportion of Escherichia/Shigella, Phascolarctobacterium, Parabacteroides,and Enterococcus increased in HC group; the fraction of Faecalibacterium was higher in LC group; and the percentage of Barnesiella and Alistipes decreased in both HC and LC groups (p < 0.05). Functional analysis based on communities’ phylogenetic investigation revealed that the pathways involved in environmental information processing and metabolism were enriched in the HC group. Those involved in cellular processes and signaling, metabolism, and gene regulation were enriched in LC group. Hence, we conclude that the long-term temperature stress can greatly alter the intestinal microbial communities in broilers and may further affect the host’s immunity and health.

Coptis chinensis Franch polysaccharides provide a dynamically regulation on intestinal microenvironment, based on the intestinal flora and mucosal immunity

ETHNOPHARMACOLOGICAL RELEVANCE

Coptis chinensis Franch is one of the most widely used traditional Chinese herbs in China and was firstly recorded in "Shennong's Classic of Materia Medica" in the Han Dynasty. The medical records in past thousands years have fully confirmed the clinical efficacies of Coptis chinensis Franch against intestinal diseases. The polysaccharides in herbal medicines can be digested by the flora and uptaken by the Peyer's patches (PPs) in intestine. It can be reasonably presumed that the polysaccharides in Coptis chinensis Franch (CCP) should be one of the critical element in the regulation of intestinal microenvironment.

AIM OF THE STUDY

This study intended to explore the dynamic regulation of CCP on intestinal microenvironment from the perspective of the intestinal mucosal immunity and the intestinal flora, in order to provide a new research perspective for the pharmacological mechanism of Coptis chinensis Franch.

MATERIALS AND METHODS

The absorption and distribution of CCP in intestinal tissues were observed after the perfusion of FITC labeled CCP. The influences of CCP on intestinal flora were evaluated by the 16sRNA gene illumina-miseq sequencing after gavage. The regulations of CCP on intestinal mucosal immunity were evaluated by the immunohistochemical analysis of the interferon-γ (IFN-γ), interleukin-4 (IL-4), interleukin-17 (IL-17) and transforming growth factor-β (TGF-β) secretion in PPs and intestinal epithelial tissue.

RESULTS

With the self-aggregation into particles morphology, CCP can be up-taken by PPs and promote the IFN-γ, IL-4, IL-17 and TGF-β secretion in PPs in a dose-dependent manner. The CCP can also be utilized by the intestinal flora and dynamically regulate the diversity, composition and distribution of the intestinal flora. The temporal regulations of CCP on IFN-γ, IL-4, IL-17 and TGF-β secretions in intestinal epithelial tissues are consistent with the variation tendency of intestinal flora.

CONCLUSION

CCP can provide effective, dynamical and dose-dependent regulations on intestinal microenvironment, not only the intestinal flora but also the PPs and intestinal epithelium related immune response. These may be involved in the multiple biological activities of Coptis chinensis Franch.

Germ-free mice are not protected against diet-induced obesity and metabolic dysfunction

Aim

Studies in the past 15 years have highlighted the role of the gut microbiota in modulation of host metabolism. The observation that germ‐free (GF) mice are leaner than conventionally raised (CONV) mice and their apparent resistance to diet‐induced obesity (DIO), sparked the interest in dissecting the possible causative role of the gut microbiota in obesity and metabolic diseases. However, discordant results among studies leave such relationship elusive.

In this study, we compared the effects of chronic Western diet (WD) intake on body weight and metabolic function of GF and CONV mice.

Methods

We fed GF and CONV mice a WD for 16 weeks and monitored body weight weekly. At the end of the dietary challenge, the metabolic phenotype of the animals was assessed. Muscle carnitine palmitoyltransferase I (CPT1) and liver AMPK activation were investigated.

Results

Both GF and CONV mice gained weight and developed glucose intolerance when fed a WD. Moreover, WD feeding was associated with increased adipose tissue inflammation, repressed hepatic AMPK activity, fatty liver and elevated hepatic triglycerides in both groups of mice. Enhanced fatty acid oxidation in the GF mouse is one of the proposed mechanisms for their resistance to DIO. The GF mice in this study showed higher CPT1 activity as compared to their CONV counterparts, despite not being protected from obesity.

Conclusions

We provide evidence that the microbiota is not an indispensable factor in the onset of obesity and metabolic dysfunction, suggesting that the relationship between gut bacteria and metabolic diseases needs further exploration.

Microbiomics, Metabolomics, Predicted Metagenomics, and Hepatic Steatosis in a Population-Based Study of 1,355 Adults

BACKGROUND AND AIMS

Previous small studies have appraised the gut microbiome (GM) in steatosis, but large-scale studies are lacking. We studied the association of the GM diversity and composition, plasma metabolites, predicted functional metagenomics, and steatosis.

APPROACH AND RESULTS

This is a cross-sectional analysis of the prospective population-based Rotterdam Study. We used 16S ribosomal RNA gene sequencing and determined taxonomy using the SILVA reference database. Alpha diversity and beta diversity were calculated using the Shannon diversity index and Bray-Curtis dissimilarities. Differences were tested across steatosis using permutational multivariate analysis of variance. Hepatic steatosis was diagnosed by ultrasonography. We subsequently selected genera using regularized regression. The functional metagenome was predicted based on the GM using Kyoto Encyclopedia of Genes and Genomes pathways. Serum metabolomics were assessed using high-throughput proton nuclear magnetic resonance. All analyses were adjusted for age, sex, body mass index, alcohol, diet, and proton-pump inhibitors. We included 1,355 participants, of whom 472 had steatosis. Alpha diversity was lower in steatosis (P = 1.1∙10^-9 ), and beta diversity varied across steatosis strata (P = 0.001). Lasso selected 37 genera of which three remained significantly associated after adjustment (Coprococcus3: β = -65; Ruminococcus Gauvreauiigroup: β = 62; and Ruminococcus Gnavusgroup: β = 45, Q-value = 0.037). Predicted metagenome analyses revealed that pathways of secondary bile-acid synthesis and biotin metabolism were present, and D-alanine metabolism was absent in steatosis. Metabolic profiles showed positive associations for aromatic and branched chain amino acids and glycoprotein acetyls with steatosis and R. Gnavusgroup, whereas these metabolites were inversely associated with alpha diversity and Coprococcus3.

CONCLUSIONS

We confirmed, on a large-scale, the lower microbial diversity and association of Coprococcus and Ruminococcus Gnavus with steatosis. We additionally showed that steatosis and alpha diversity share opposite metabolic profiles.

Inflammatory Mechanisms Underlying Nonalcoholic Steatohepatitis and the Transition to Hepatocellular Carcinoma

Nonalcoholic fatty liver disease (NAFLD) is a rising chronic liver disease and comprises a spectrum from simple steatosis to nonalcoholic steatohepatitis (NASH) to end-stage cirrhosis and risk of hepatocellular carcinoma (HCC). The pathogenesis of NAFLD is multifactorial, but inflammation is considered the key element of disease progression. The liver harbors an abundance of resident immune cells, that in concert with recruited immune cells, orchestrate steatohepatitis. While inflammatory processes drive fibrosis and disease progression in NASH, fueling the ground for HCC development, immunity also exerts antitumor activities. Furthermore, immunotherapy is a promising new treatment of HCC, warranting a more detailed understanding of inflammatory mechanisms underlying the progression of NASH and transition to HCC. Novel methodologies such as single-cell sequencing, genetic fate mapping, and intravital microscopy have unraveled complex mechanisms behind immune-mediated liver injury. In this review, we highlight some of the emerging paradigms, including macrophage heterogeneity, contributions of nonclassical immune cells, the role of the adaptive immune system, interorgan crosstalk with adipose tissue and gut microbiota. Furthermore, we summarize recent advances in preclinical and clinical studies aimed at modulating the inflammatory cascade and discuss how these novel therapeutic avenues may help in preventing or combating NAFLD-associated HCC.

A high-fat diet and high-fat and high-cholesterol diet may affect glucose and lipid metabolism differentially through gut microbiota in mice

This study was conducted to investigate the effects of a high-fat diet (HFD) and high-fat and high-cholesterol diet (HFHCD) on glucose and lipid metabolism and on the intestinal microbiota of the host animal. A total of 30 four-week-old female C57BL/6 mice were randomly divided into three groups (n=10) and fed with a normal diet (ND), HFD, or HFHCD for 12 weeks, respectively. The HFD significantly increased body weight and visceral adipose accumulation and partly lowered oral glucose tolerance compared with the ND and HFHCD. The HFHCD increased liver weight, liver fat infiltration, liver triglycerides, and liver total cholesterol compared with the ND and HFD. Moreover, it increased serum high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, and total cholesterol compared with the ND and HFD and upregulated alanine aminotransferase, aspartate aminotransferase, and alkaline phosphatase significantly. The HFHCD also significantly decreased the α-diversity of the fecal bacteria of the mice, to a greater extent than the HFD. The composition of fecal bacteria among the three groups was apparently different. Compared with the HFHCD-fed mice, the HFD-fed mice had more Oscillospira, Odoribacter, Bacteroides, and [Prevotella], but less [Ruminococcus] and Akkermansia. Cecal short-chain fatty acids were significantly decreased after the mice were fed the HFD or HFHCD for 12 weeks. Our findings indicate that an HFD and HFHCD can alter the glucose and lipid metabolism of the host animal differentially; modifications of intestinal microbiota and their metabolites may be an important underlying mechanism.

Extracellular Vesicles as Inflammatory Drivers in NAFLD

Non-alcoholic fatty liver disease (NAFLD) is a highly prevalent chronic liver disease in most parts of the world affecting one-third of the western population and a growing cause for end-stage liver diseases such as hepatocellular carcinoma (HCC). Majorly driven by obesity and diabetes mellitus, NAFLD is more of a multifactorial disease affected by extra-hepatic organ crosstalk. Non-alcoholic fatty liver (NAFL) progressed to non-alcoholic steatohepatitis (NASH) predisposes multiple complications such as fibrosis, cirrhosis, and HCC. Although the complete pathogenic mechanisms of this disease are not understood, inflammation is considered as a key driver to the onset of NASH. Lipotoxicity, inflammatory cytokines, chemokines, and intestinal dysbiosis trigger both hepatic and systemic inflammatory cascades simultaneously activating immune responses. Over a few years, extracellular vesicles studied extensively concerning the pathobiology of NAFLD indicated it as a key modulator in the setting of immune-mediated inflammation. Exosomes and microvesicles, the two main types of extracellular vesicles are secreted by an array of most mammalian cells, which are involved mainly in cell-cell communication that are unique to cell type. Various bioactive cargoes containing extracellular vesicles derived from both hepatic and extrahepatic milieu showed critical implications in driving steatosis to NASH reaffirming inflammation as the primary contributor to the whole process. In this mini-review, we provide brief insights into the inflammatory mediators of NASH with special emphasis on extracellular vesicles that acts as drivers of inflammation in NAFLD.

The Gut Microbial Endocrine Organ in Type 2 Diabetes

Historically, the focus of type II diabetes mellitus (T2DM) research has been on host metabolism and hormone action. However, emerging evidence suggests that the gut microbiome, commensal microbes that colonize the gastrointestinal tract, also play a significant role in T2DM pathogenesis. Specifically, gut microbes metabolize what is available to them through the host diet to produce small molecule metabolites that can have endocrine-like effects on human cells. In fact, the meta-organismal crosstalk between gut microbe-generated metabolites and host receptor systems may represent an untapped therapeutic target for those at risk for or suffering from T2DM. Recent evidence suggests that gut microbe-derived metabolites can impact host adiposity, insulin resistance, and hormone secretion to collectively impact T2DM progression. Here we review the current evidence that structurally diverse gut microbe-derived metabolites, including short chain fatty acids, secondary bile acids, aromatic metabolites, trimethylamine-N-oxide, polyamines, and N-acyl amides, that can engage with host receptors in an endocrine-like manner to promote host metabolic disturbance associated with T2DM. Although these microbe-host signaling circuits are not as well understood as host hormonal signaling, they hold untapped potential as new druggable targets to improve T2DM complications. Whether drugs that selectively target meta-organismal endocrinology will be safe and efficacious in treating T2DM is a key new question in the field of endocrinology. Here we discuss the opportunities and challenges in targeting the gut microbial endocrine organ for the treatment of diabetes and potentially many other diseases where diet-microbe-host interactions play a contributory role.

The interplay between host cellular and gut microbial metabolism in NAFLD development and prevention

Metabolism regulation centred on insulin resistance is increasingly important in nonalcoholic fatty liver disease (NAFLD). This review focuses on the interactions between the host cellular and gut microbial metabolism during the development of NAFLD. The cellular metabolism of essential nutrients, such as glucose, lipids and amino acids, is reconstructed with inflammation, immune mechanisms and oxidative stress, and these alterations modify the intestinal, hepatic and systemic environments, and regulate the composition and activity of gut microbes. Microbial metabolites, such as short-chain fatty acids, secondary bile acids, protein fermentation products, choline and ethanol and bacterial toxicants, such as lipopolysaccharides, peptidoglycans and bacterial DNA, play vital roles in NAFLD. The microbe-metabolite relationship is crucial for the modulation of intestinal microbial composition and metabolic activity. The intestinal microbiota and their metabolites participate in epithelial cell metabolism via a series of cell receptors and signalling pathways and remodel the metabolism of various cells in the liver via the gut-liver axis. Microbial metabolic manipulation is a promising strategy for NAFLD prevention, but larger-sampled clinical trials are required for future application.

Fecal Microbiota Transplant from Human to Mice Gives Insights into the Role of the Gut Microbiota in Non-Alcoholic Fatty Liver Disease (NAFLD)

Non-alcoholic fatty liver diseases (NAFLD) are associated with changes in the composition and metabolic activities of the gut microbiota. However, the causal role played by the gut microbiota in individual susceptibility to NAFLD and particularly at its early stage is still unclear. In this context, we transplanted the microbiota from a patient with fatty liver (NAFL) and from a healthy individual to two groups of mice. We first showed that the microbiota composition in recipient mice resembled the microbiota composition of their respective human donor. Following administration of a high-fructose, high-fat diet, mice that received the human NAFL microbiota (NAFLR) gained more weight and had a higher liver triglycerides level and higher plasma LDL cholesterol than mice that received the human healthy microbiota (HR). Metabolomic analyses revealed that it was associated with lower and higher plasma levels of glycine and 3-Indolepropionic acid in NAFLR mice, respectively. Moreover, several bacterial genera and OTUs were identified as differently represented in the NAFLR and HR microbiota and therefore potentially responsible for the different phenotypes observed. Altogether, our results confirm that the gut bacteria play a role in obesity and steatosis development and that targeting the gut microbiota may be a preventive or therapeutic strategy in NAFLD management.