Systematic review: microbial dysbiosis and nonalcoholic fatty liver disease

Role of Microbiota-Derived Metabolites in Alcoholic and Non-Alcoholic Fatty Liver Diseases

Chronic liver disease encompasses diseases that have various causes, such as alcoholic liver disease (ALD) and non-alcoholic fatty liver disease (NAFLD). Gut microbiota dysregulation plays a key role in the pathogenesis of ALD and NAFLD through the gut-liver axis. The gut microbiota consists of various microorganisms that play a role in maintaining the homeostasis of the host and release a wide number of metabolites, including short-chain fatty acids (SCFAs), peptides, and hormones, continually shaping the host's immunity and metabolism. The integrity of the intestinal mucosal and vascular barriers is crucial to protect liver cells from exposure to harmful metabolites and pathogen-associated molecular pattern molecules. Dysbiosis and increased intestinal permeability may allow the liver to be exposed to abundant harmful metabolites that promote liver inflammation and fibrosis. In this review, we introduce the metabolites and components derived from the gut microbiota and discuss their pathologic effect in the liver alongside recent advances in molecular-based therapeutics and novel mechanistic findings associated with the gut-liver axis in ALD and NAFLD.

Metabolic-Associated Fatty Liver Disease (MAFLD), Diabetes, and Cardiovascular Disease: Associations with Fructose Metabolism and Gut Microbiota

Non-alcoholic fatty liver disease (NAFLD) is an increasingly common condition associated with type 2 diabetes (T2DM) and cardiovascular disease (CVD). Since systemic metabolic dysfunction underlies NAFLD, the current nomenclature has been revised, and the term metabolic-associated fatty liver disease (MAFLD) has been proposed. The new definition emphasizes the bidirectional relationships and increases awareness in looking for fatty liver disease among patients with T2DM and CVD or its risk factors, as well as looking for these diseases among patients with NAFLD. The most recommended treatment method of NAFLD is lifestyle changes, including dietary fructose limitation, although other treatment methods of NAFLD have recently emerged and are being studied. Given the focus on the liver-gut axis targeting, bacteria may also be a future aim of NAFLD treatment given the microbiome signatures discriminating healthy individuals from those with NAFLD. In this review article, we will provide an overview of the associations of fructose consumption, gut microbiota, diabetes, and CVD in patients with NAFLD.

Serum trimethylamine-N-oxide and gut microbiome alterations are associated with cholesterol deposition in the liver of laying hens fed with rapeseed meal

Sinapine derived from cruciferous plants could be converted into trimethylamine by intestinal microbiota. Its metabolite, trimethylamine N-oxide (TMAO), is closely linked to increased risk of cardiovascular disease and fat deposition in mammals. Hens fed with rapeseed meal (RSM) suffered from fatty liver hemorrhage syndrome (FLHS). This study was conducted to investigate whether RSM-induced fatty liver is due to TMAO via altering microbiota composition and diversity. At 33 weeks of age, 600 laying hens were randomly divided into 5 treatment groups, namely control and 14% RSM treatment groups (DY5, with 16.2% erucic acid [EA] and 74.66% glucosinolate [Gl] contents; MB1, with 3.50% EA and 43.23% Gl contents; DY6, with 6.7% EA and 22.67% Gl contents; XH3, with 44.60% EA and 132.83% Gl contents) for 8 weeks. Results revealed that 3 hens died due to liver hemorrhage after ingesting 14% RSM diet. The 14% RSM decreased serum low-density lipoprotein cholesterol (LDL-C) content (P < 0.01) while tended to increase serum TMAO content compared to the control group (P = 0.08). The 14% RSM diet increased red oil O optical density (P < 0.01), and increased total cholesterol (TC) and LDL-C content in the liver (P < 0.01, and P < 0.01, respectively). The 14% RSM decreased liver total bile acid (TBA) content compared to the control (P < 0.01). The DY6 had a higher TBA content in the liver than the XH3 (P < 0.01). The 14% RSM decreased mRNA abundance of liver X receptors alpha (LXR-α, P = 0.01), and increased mRNA abundance of sterol response element binding protein 2 (SREBP-2, P = 0.04). Results revealed that the in-feed RSM could alter richness and diversity of cecal microbiota compared to the control (P < 0.05). Liver TC content and serum TMAO showed a negative relationship with Proteobacteria and Actinobacteria (P = 0.04). In conclusion, 14% RSM increased liver TC and induced high liver score of FLHS, which was possibly associated with the altered cecal microbiota composition, increased serum TMAO levels and LXR-α and SREBP-2 expressions.

The Gut-Liver Axis in Chronic Liver Disease: A Macrophage Perspective

Chronic liver disease (CLD) is a growing health concern which accounts for two million deaths per year. Obesity, alcohol overconsumption, and progressive cholestasis are commonly characterized by persistent low-grade inflammation and advancing fibrosis, which form the basis for development of end-stage liver disease complications, including hepatocellular carcinoma. CLD pathophysiology extends to the intestinal tract and is characterized by intestinal dysbiosis, bile acid dysregulation, and gut barrier disruption. In addition, macrophages are key players in CLD progression and intestinal barrier breakdown. Emerging studies are unveiling macrophage heterogeneity and driving factors of their plasticity in health and disease. To date, in-depth investigation of how gut-liver axis disruption impacts the hepatic and intestinal macrophage pool in CLD pathogenesis is scarce. In this review, we give an overview of the role of intestinal and hepatic macrophages in homeostasis and gut-liver axis disruption in progressive stages of CLD.

Periodontal disease-related nonalcoholic fatty liver disease and nonalcoholic steatohepatitis: An emerging concept of oral-liver axis

Periodontal disease, a chronic inflammatory disease of the periodontal tissues, is not only a major cause of tooth loss, but it is also known to exacerbate/be associated with various metabolic disorders, such as obesity, diabetes, dyslipidemia, and cardiovascular disease. Recently, growing evidence has suggested that periodontal disease has adverse effects on the pathophysiology of liver disease. In particular, nonalcoholic fatty liver disease, a hepatic manifestation of metabolic syndrome, has been associated with periodontal disease. Nonalcoholic fatty liver disease is characterized by hepatic fat deposition in the absence of a habitual drinking history, viral infections, or autoimmune diseases. A subset of nonalcoholic fatty liver diseases can develop into more severe and progressive forms, namely nonalcoholic steatohepatitis. The latter can lead to cirrhosis and hepatocellular carcinoma, which are end‐stage liver diseases. Extensive research has provided plausible mechanisms to explain how periodontal disease can negatively affect nonalcoholic fatty liver disease and nonalcoholic steatohepatitis, namely via hematogenous or enteral routes. During periodontitis, the liver is under constant exposure to various pathogenic factors that diffuse systemically from the oral cavity, such as bacteria and their by‐products, inflammatory cytokines, and reactive oxygen species, and these can be involved in disease promotion of nonalcoholic fatty liver disease and nonalcoholic steatohepatitis. Also, gut microbiome dysbiosis induced by enteral translocation of periodontopathic bacteria may impair gut wall barrier function and promote the transfer of hepatotoxins and enterobacteria to the liver through the enterohepatic circulation. Moreover, in a population with metabolic syndrome, the interaction between periodontitis and systemic conditions related to insulin resistance further strengthens the association with nonalcoholic fatty liver disease. However, most of the pathologic links between periodontitis and nonalcoholic fatty liver disease in humans are provided by epidemiologic observational studies, with the causal relationship not yet being established. Several systematic and meta‐analysis studies also show conflicting results. In addition, the effect of periodontal treatment on nonalcoholic fatty liver disease has hardly been studied. Despite these limitations, the global burden of periodontal disease combined with the recent nonalcoholic fatty liver disease epidemic has important clinical and public health implications. Emerging evidence suggests an association between periodontal disease and liver diseases, and thus we propose the term periodontal disease–related nonalcoholic fatty liver disease or periodontal disease–related nonalcoholic steatohepatitis. Continued efforts in this area will pave the way for new diagnostic and therapeutic approaches based on a periodontologic viewpoint to address this life‐threatening liver disease.

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.

Interaction Between the Microbiota, Epithelia, and Immune Cells in the Intestine

The gastrointestinal tract harbors numerous commensal bacteria, referred to as the microbiota, that benefit host health by digesting dietary components and eliminating pathogens. The intestinal microbiota maintains epithelial barrier integrity and shapes the mucosal immune system, balancing host defense and oral tolerance with microbial metabolites, components, and attachment to host cells. To avoid aberrant immune responses, epithelial cells segregate the intestinal microbiota from immune cells by constructing chemical and physical barriers, leading to the establishment of host-commensal mutualism. Furthermore, intestinal immune cells participate in the maintenance of a healthy microbiota community and reinforce epithelial barrier functions. Perturbations of the microbiota composition are commonly observed in patients with autoimmune diseases and chronic inflammatory disorders. An understanding of the intimate interactions between the intestinal microbiota, epithelial cells, and immune cells that are crucial for the maintenance of intestinal homeostasis might promote advances in diagnostic and therapeutic approaches for various diseases.

Effect of Microbiome on Non-Alcoholic Fatty Liver Disease and the Role of Probiotics, Prebiotics, and Biogenics

Non-alcoholic fatty liver disease (NAFLD) is a leading cause of liver cirrhosis and hepatocellular carcinoma. NAFLD is associated with metabolic disorders such as obesity, insulin resistance, dyslipidemia, steatohepatitis, and liver fibrosis. Liver-resident (Kupffer cells) and recruited macrophages contribute to low-grade chronic inflammation in various tissues by modulating macrophage polarization, which is implicated in the pathogenesis of metabolic diseases. Abnormalities in the intestinal environment, such as the gut microbiota, metabolites, and immune system, are also involved in the pathogenesis and development of NAFLD. Hepatic macrophage activation is induced by the permeation of antigens, endotoxins, and other proinflammatory substances into the bloodstream as a result of increased intestinal permeability. Therefore, it is important to understand the role of the gut–liver axis in influencing macrophage activity, which is central to the pathogenesis of NAFLD and nonalcoholic steatohepatitis (NASH). Not only probiotics but also biogenics (heat-killed lactic acid bacteria) are effective in ameliorating the progression of NASH. Here we review the effect of hepatic macrophages/Kupffer cells, other immune cells, intestinal permeability, and immunity on NAFLD and NASH and the impact of probiotics, prebiotics, and biogenesis on those diseases.

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.

Danggui-Shaoyao-San Improves Gut Microbia Dysbiosis and Hepatic Lipid Homeostasis in Fructose-Fed Rats

Metabolic syndrome (MetS) is a pathological state of many abnormal metabolic sections. These abnormalities are closely related to diabetes, heart pathologies and other vascular diseases. Danggui-Shaoyao-San (DSS) is a traditional Chinese medicine formula that has been used as a therapy for Alzheimer’s disease. DSS has rarely been reported in the application of MetS and its mechanism of how it improves gut microbia dysbiosis and hepatic lipid homeostasis. In this study, three extracts of DSS were obtained using water, 50% methanol in water and methanol as extracting solvents. Their chemical substances were analyzed by ultra-performance liquid chromatography coupled with quadrupole time-of-flight mass (UPLC-Q/TOF-MS). Pharmacodynamic effect of the extracts were evaluated by comparison of biochemical factors, 16S rRNA sequencing test for gut microbiota analysis, as well as metabonomic and transcriptomic assessments on liver tissues from fructose-fed rats. This study aimed at investigating DSS’s mechanism of regulating blood lipid, anti-inflammation and reducing blood glucose. The results showed that the 50% methanol extract (HME) was more effective. It was worth noting that hydroxysteroid 17β-dehydrogenase 13 (HSD17β13) as a critical element of increasing blood lipid biomarker-triglyceride (TG), was decreased markedly by DSS. The influence from upgraded hydroxysteroid 17β-dehydrogenase 7 (HSD17β7) may be stronger than that from downgraded Lactobacillus in the aspect of regulating back blood lipid biomarker-total cholesterol (TC). The differential down-regulation of tumornecrosis factor alpha (TNF-α) and the significant up-regulation of Akkermansia showed the effective effect of anti-inflammation by DSS. The declining glycine and alanine induced the lowering glucose and lactate. It demonstrated that DSS slowed down the reaction of gluconeogenesis to reduce the blood glucose. The results demonstrated that DSS improved pathological symptoms of MetS and some special biochemical factors in three aspects by better regulating intestinal floras and improving hepatic gene expressions and metabolites.

Multi-Omics Analysis Reveals Disturbance of Nanosecond Pulsed Electric Field in the Serum Metabolic Spectrum and Gut Microbiota

Nanosecond pulsed electric field (nsPEF) is a novel ablation technique that is based on high-intensity electric voltage to achieve tumour-killing effect in the target region, and increasingly considered for treating tumours of the liver, kidneys and other organs with rich blood supply. This study aims to observe effect of nsPFE treatment on serum metabolites and gut microbiota. The serum and faecal specimens of the pigs were collected pre- and post-treatment. The gut microbiota of pigs was sequenced by Illumina Miseq platform for analysing the diversity and alterations of gut microbiota. Liquid chromatography-mass spectrometry (LC-MS)-based metabonomic analysis and Pearson coefficient method were also used to construct the interaction system of different metabolites, metabolic pathways and flora. A total of 1,477 differential metabolites from the serum were identified by four cross-comparisons of different post-operative groups with the control group. In addition, an average of 636 OTUs per sample was detected. Correlation analysis also revealed the strong correlation between intestinal bacteria and differential metabolites. The nsPEF ablation of the liver results in a degree of liver damage that affects various metabolic pathways, mainly lipid metabolism, as well as gut microbiota. In conclusion, our study provided a good point for the safety and feasibility of applying nsPEF on liver through the integrated analysis of metabolomics and microbiomes, which is beneficial for the improvement of nsPEF in clinical use.

Eradication of Chronic HCV Infection: Improvement of Dysbiosis Only in Patients Without Liver Cirrhosis

BACKGROUND AND AIMS

It is well accepted that liver diseases and their outcomes are associated with intestinal microbiota, but causality is difficult to establish. The intestinal microbiota are altered in patients with hepatitis C. As chronic HCV infection can now be cured in almost all patients, it is an ideal model to study the influence of liver disease on the microbiota.

APPROACH AND RESULTS

We aimed to prospectively analyze the changes in the gut microbiome in patients who received direct-acting antivirals (DAA) and achieved sustained virological response (SVR). Amplicon sequencing of the V1-V2 region in the 16S ribosomal RNA gene was performed in stool samples of patients with chronic hepatitis C. Patients in the treatment group received DAA (n = 65), whereas in the control group, no DAA were given (n = 33). Only patients achieving SVR were included. The alpha diversity increased numerically but not significantly from baseline to SVR at week 24 or 48 (SVR24/48; 2.784 ± 0.248 vs. 2.846 ± 0.224; P = 0.057). When stratifying for the presence of liver cirrhosis, a significant increase in diversity was only seen in patients without cirrhosis. Differences in the microbial community structure induced by the achievement of SVR were only observed in patients without liver cirrhosis. In patients with liver cirrhosis and in the control group, no significant differences were observed.

CONCLUSIONS

In conclusion, the achievement of SVR24/48 in patients with chronic HCV was associated with changes in the intestinal microbiota. However, these changes were only seen in patients without liver cirrhosis. A major role of liver remodeling on the intestinal microbiota is indicated by the dynamics of the intestinal microbial community structure depending on the stage of fibrosis in patients resolving chronic hepatitis C.

Gut Microbiota And Inflammatory Disorders

The gut has been colonized with bacteria, fungi, viruses, archaea, eukarya. The human and bacterial cells are found in a 1:1 ratio, while the variance in the diversity of gut microbiota may result in Dysbiosis. Gut dysbiosis may result in various pathological manifestations. Beneficial gut microbiota may synthesize short-chain fatty acids like acetate, butyrate, propionate, while -gram-negative organisms are the primary source of LPS, a potent pro-inflammatory mediator. Both gut microbiota and microbial products may be involved in immunomodulation as well as inflammation. Prebiotics and probiotics are being explored as therapeutic agents against various inflammatory and autoimmune disorders. Here we discuss the molecular mechanisms involved in gut bacteria-mediated modulation of various inflammatory and autoimmune disorders.

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.

Emulating the gut-liver axis: Dissecting the microbiome's effect on drug metabolism using multiorgan-on-chip models

The homeostatic relationship between the gut, its microbiome, and the liver is crucial for the regulation of drug metabolism processes. Gut microbes are known to influence human health and disease by enhancing food metabolism and providing a first line of defense against pathogens. In addition to this, the gut microbiome also plays a key role in the processing of exogenous pharmaceutical compounds. Modeling the highly variable luminal gut environment and understanding how gut microbes can modulate drug availability or induce liver toxicity remains a challenge. However, microfluidics-based technologies such as organ-on-chips could overcome current challenges in drug toxicity assessment assays because these technologies are able to better recapitulate complex human responses. Efforts are being made to create in vitro multiorgan platforms, tailored for an individual patient's microbial background. These platforms could be used as a tool to predict the effect of the gut microbiome on pharmacokinetics in a personalized way.

Lactobacillus casei YRL577 combined with plant extracts reduce markers of non-alcoholic fatty liver disease in mice

Probiotics and plant extracts are considered to prevent the development of non-alcoholic fatty liver disease (NAFLD). The present study explores the effects of using both probiotics and plant extracts on NAFLD. The present study evaluated the effects of plant extracts on lipid droplet accumulation and the growth of probiotics in vitro. A C57BL/6 mouse model was used to examine the effects of probiotics and plant extracts on NAFLD. Body weight and food intake were measured. The levels of serum lipids, oxidative stress and the liver injury index were determined using commercial kits. Haematoxylin and eosin staining, GC and real-time PCR were also used for analysis. The results revealed that administration of Lactobacillus casei YRL577 and L. paracasei X11 with resveratrol (RES) or tea polyphenols (TP) significantly reduced the levels of total cholesterol, TAG and LDL-cholesterol and increased the level of the HDL-cholesterol. The groups of L. casei YRL577 with RES and TP also regulated the liver structure, oxidative stress and injury. Furthermore, L. casei YRL577 with TP exhibited a more positive effect towards improving the NAFLD and increased the concentrations of the butyric acid than other three combined groups. L. casei YRL577 with TP up-regulated the mRNA levels of the farnesoid X receptor and fibroblast growth factor 15 and decreased the mRNA levels of the apical Na-dependent bile acid transporter. These findings showed that L. casei YRL577 + TP-modified genes in the intestinal bile acid pathway improved markers of NAFLD.

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.

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.

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.

Bacterial and eukaryotic extracellular vesicles and nonalcoholic fatty liver disease: new players in the gut-liver axis?

The liver and intestine communicate in a bidirectional way through the biliary tract, portal vein, and other components of the gut-liver axis. The gut microbiota is one of the major contributors to the production of several proteins and bile acids. Imbalance in the gut bacterial community, called dysbiosis, participates in the development and progression of several chronic liver diseases, such as nonalcoholic fatty liver disease (NAFLD). NAFLD is currently considered the main chronic liver disease worldwide. Dysbiosis contributes to NAFLD development and progression, notably by a greater translocation of pathogen-associated molecular patterns (PAMPs) in the blood. Lipopolysaccharide (LPS) is a PAMP that activates Toll-like receptor 4 (TLR4), induces liver inflammation, and participates in the development of fibrogenesis. LPS can be transported by bacterial extracellular vesicles (EVs). EVs are spherical structures produced by eukaryotic and prokaryotic cells that transfer information to distant cells and may represent new players in NAFLD development and progression. The present review summarizes the role of eukaryotic EVs, either circulating or tissue-derived, in NAFLD features, such as liver inflammation, angiogenesis, and fibrosis. Circulating EV levels are dynamic and correlate with disease stage and severity. However, scarce information is available concerning the involvement of bacterial EVs in liver disease. The present review highlights a potential role of bacterial EVs in insulin resistance and liver inflammation, although the mechanism involved has not been elucidated. In addition, because of their distinct signatures, eukaryotic and prokaryotic EVs may also represent a promising NAFLD diagnostic tool as a "liquid biopsy" in the future.

Sacran, a sulfated polysaccharide, suppresses the absorption of lipids and modulates the intestinal flora in non-alcoholic steatohepatitis model rats

AIMS

The objective of this study was to investigate the effects of administering sacran, a sulfated polysaccharide, on liver biology, gut microbiota, oxidative stress, and inflammation on stroke-prone spontaneously hypertensive (SHRSP5/Dmcr) rats that develop fibrotic steatohepatitis with histological similarities to that of non-alcoholic steatohepatitis (NASH).

MAIN METHODS

Four groups of 8-week-old SHRSP5/Dmcr rats were fed a high fat-cholesterol (HFC) diet for 4 and 8 weeks and administered either sacran (80 mg/kg/day) or a non-treatment, respectively. Liver function was evaluated by biochemical and histopathological analyses. Hepatic inflammatory markers were measured using mRNA expression. Fecal microbial profiles were determined via 16S rRNA sequencing. A triglyceride (TG) absorption test was administered to the 8-week-old Sprague-Dawley (SD) rats.

KEY FINDING

Sacran administration was observed to decrease the extent of oxidative stress and hepatic biochemical parameters in serum and hepatic injury with the levels of transforming growth factor-beta (TGF-β1) and tumor necrosis factor-alpha (TNF-α), being increased compared to those of the non-treatment group. At the genus level, sacran administration caused a significant decrease in the harmful Prevotella genus, and a significant increase in the useful Blautia genus was observed. Sacran administration also decreased the serum TG increase that was induced by administering corn oil to the SD rats.

SIGNIFICANCE

We conclude that sacran administration has the potential to reduce the absorption of lipids into blood and to improve several gut microbiotas, in the gastrointestinal tract, thereby inhibiting the subsequent development of oxidative stress and hepatic markers in the systematic circulation on NASH.

New Drugs on the Block-Emerging Treatments for Nonalcoholic Steatohepatitis

Patients with nonalcoholic steatohepatitis (NASH) are at higher risk of progression to advanced stages of fibrosis, cirrhosis, hepatocellular carcinoma and other end-stage liver disease complications. When addressing treatment of NASH, we have limited approved options, and the mainstay of therapy is lifestyle intervention. Extensive research and revelation in the field of pathogenesis of NASH has offered new possibilities of treatment and emerging new drugs that are being tested currently in numerous preclinical and clinical trials. These drugs target almost all steps in the pathogenesis of NASH to improve insulin sensitivity, glucose and lipid metabolism, to inhibit de novo lipogenesis and delivery of lipids to the liver, and to influence apoptosis, inflammation and fibrogenesis. Although NASH is a multifactorial disease, in the future we could identify the predominating pathological mechanism and, by choosing the most appropriate specific medication, tailor the treatment for every patient individually.

Hepatic steatosis relates to gastrointestinal microbiota changes in obese girls with polycystic ovary syndrome

Objective

Hepatic steatosis (HS) is common in adolescents with obesity and polycystic ovary syndrome (PCOS). Gut microbiota are altered in adults with obesity, HS, and PCOS, which may worsen metabolic outcomes, but similar data is lacking in youth.

Methods

Thirty-four adolescents with PCOS and obesity underwent stool and fasting blood collection, oral glucose tolerance testing, and MRI for hepatic fat fraction (HFF). Fecal bacteria were profiled by high-throughput 16S rRNA gene sequencing.

Results

50% had HS (N = 17, age 16.2±1.5 years, BMI 38±7 kg/m², HFF 9.8[6.5, 20.7]%) and 50% did not (N = 17, age 15.8±2.2 years, BMI 35±4 kg/m², HFF 3.8[2.6, 4.4]%). The groups showed no difference in bacterial α-diversity (richness p = 0.202; evenness p = 0.087; and diversity p = 0.069) or global difference in microbiota (β-diversity). Those with HS had lower % relative abundance (%RA) of Bacteroidetes (p = 0.013), Bacteroidaceae (p = 0.009), Porphyromonadaceae (p = 0.011), and Ruminococcaceae (p = 0.008), and higher Firmicutes:Bacteroidetes (F:B) ratio (47.8% vs. 4.3%, p = 0.018) and Streptococcaceae (p = 0.034). Bacterial taxa including phyla F:B ratio, Bacteroidetes, and family Bacteroidaceae, Ruminococcaceae and Porphyromonadaceae correlated with metabolic markers.

Conclusions

Obese adolescents with PCOS and HS have differences in composition of gut microbiota, which correlate with metabolic markers, suggesting a modifying role of gut microbiota in HS and PCOS.

Interaction Mechanisms Between Major Depressive Disorder and Non-alcoholic Fatty Liver Disease

Major depressive disorder (MDD), which is highly associated with non-alcoholic fatty liver disease (NAFLD), has complex pathogenic mechanisms. However, a limited number of studies have evaluated the mutual pathomechanisms involved in MDD and NAFLD development. Chronic stress-mediated elevations in glucocorticoid (GC) levels play an important role in the development of MDD-related NAFLD. Elevated GC levels can induce the release of inflammatory factors and changes in gut permeability. Elevated levels of inflammatory factors activate the hypothalamic-pituitary-adrenal (HPA) axis, which further increases the release of GC. At the same time, changes in gut permeability promote the release of inflammatory factors, which results in a vicious circle among the three, causing disease outbreaks. Even though the specific role of the thyroid hormone (TH) in this pathogenesis has not been fully established, it is highly correlated with MDD and NAFLD. Therefore, changing lifestyles and reducing psychological stress levels are necessary measures for preventing MDD-related NAFLD. Among them, GC inhibitors and receptor antagonists may be key in the alleviation of early and mid-term disease progression. However, combination medications may be important in late-stage diseases, but they are associated with various side effects. Traditional Chinese medicines have been shown to be potential therapeutic alternatives for such complex diseases.

Endotoxins and Non-Alcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) is the most common chronic liver disease worldwide. It occurs with a prevalence of up to 25%, of which 10-20% cases progress to nonalcoholic steatohepatitis (NASH), cirrhosis, and liver cancer. The histopathology of NASH is characterized by neutrophilic infiltration, and endotoxins from gram-negative rods have been postulated as a contributing factor. Elevations in endotoxin levels in the blood can be classified as intestinal and hepatic factors. In recent years, leaky gut syndrome, which is characterized by impaired intestinal barrier function, has become a significant issue. A leaky gut may prompt intestinal bacteria dysbiosis and increase the amount of endotoxin that enters the liver from the portal vein. These contribute to persistent chronic inflammation and progressive liver damage. In addition, hepatic factors suggest that liver damage can be induced by low-dose endotoxins, which does not occur in healthy individuals. In particular, increased expression of CD14, an endotoxin co-receptor in the liver, may result in leptin-induced endotoxin hyper-responsiveness in obese individuals. Thus, elevated blood endotoxin levels contribute to the progression of NASH. The current therapeutic targets for NASH treat steatosis and liver inflammation and fibrosis. While many clinical trials are underway, no studies have been performed on therapeutic agents that target the intestinal barrier. Recently, a randomized placebo-controlled trial examined the role of the intestinal barrier in patients with NAFLD. To our knowledge, this study was the first of its kind and study suggested that the intestinal barrier may be a novel target in the future treatment of NAFLD.

Emerging Roles of Liver Sinusoidal Endothelial Cells in Nonalcoholic Steatohepatitis

Simple Summary

Nonalcoholic fatty liver disease (NAFLD) is a hepatic manifestation of the metabolic syndrome. With the prevalence of obesity and type 2 diabetes, NAFLD is becoming the most common liver disorder worldwide. More than 10% of NAFLD patients progress to an inflammatory and fibrotic form called nonalcoholic steatohepatitis (NASH), which can lead to end-stage liver disease. Liver sinusoidal endothelial cells (LSEC) are highly specialized cells located at the interface between the flowing blood in the liver and the other liver cells. The current review highlights the recent knowledge of the role of LSEC in the development of NASH, and how LSEC change their structure and function during NAFLD progression. Moreover, the review discusses the pathogenic role of nanometer-sized particles called extracellular vesicles that mediate intercellular communication in the NASH liver. The current manuscript has a special emphasis on the role of adhesion molecules expressed on the LSEC surface in the recruitment of circulating leukocytes to the liver, a critical step in liver inflammation in NASH. Furthermore, the review shed some lights on LSEC-targeted potential therapeutic strategies in NASH.

Abstract

Nonalcoholic steatohepatitis (NASH) has become a growing public health problem worldwide, yet its pathophysiology remains unclear. Liver sinusoidal endothelial cells (LSEC) have unique morphology and function, and play a critical role in liver homeostasis. Emerging literature implicates LSEC in many pathological processes in the liver, including metabolic dysregulation, inflammation, angiogenesis, and carcinogenesis. In this review, we highlight the current knowledge of the role of LSEC in each of the progressive phases of NASH pathophysiology (steatosis, inflammation, fibrosis, and the development of hepatocellular carcinoma). We discuss processes that have important roles in NASH progression including the detrimental transformation of LSEC called “capillarization”, production of inflammatory and profibrogenic mediators by LSEC as well as LSEC-mediated angiogenesis. The current review has a special emphasis on LSEC adhesion molecules, and their key role in the inflammatory response in NASH. Moreover, we discuss the pathogenic role of extracellular vesicles and their bioactive cargos in liver intercellular communication, inflammation, and fibrosis. Finally, we highlight LSEC-adhesion molecules and derived bioactive product as potential therapeutic targets for human NASH.

Dendropanax morbifera Leaf Extracts Improved Alcohol Liver Injury in Association with Changes in the Gut Microbiota of Rats

This study evaluated the protective effects of Dendropanax morbifera leaf (DML) extracts in the liver due to excessive ethanol consumption. Our results showed that the ethanol extract had better antioxidant activity than the water extract, likely due to the higher levels of total flavonoid and phenolic compounds in the former. We found that the main phenolic acid was chlorogenic acid and the major flavonoid was rutin. Results from the animal model experiment showed concentration-dependent liver protection with the distilled water extract showing better liver protection than the ethanol extract. Gut microbiota dysbiosis induced by alcohol consumption was significantly shifted by DML extracts through increasing mainly Bacteroides and Allobaculum. Moreover, predicted metabolic activities of biosynthesis of beneficial monounsaturated fatty acids such as oleate and palmitoleate were enhanced. Our results suggest that these hepatoprotective effects are likely due to the increased activities of antioxidant enzymes and partially promoted by intestinal microbiota shifts.

Correlation of gut Firmicutes/Bacteroidetes ratio with fibrosis and steatosis stratified by body mass index in patients with non-alcoholic fatty liver disease

We investigated the gut microbiota in patients with non-alcoholic fatty liver disease (NAFLD) and its correlation with fibrosis and steatosis stratified by body mass index, as reflected in the controlled attenuation parameter and transient elastography values. A cross-sectional study was performed on 37 patients with NAFLD at Cipto Mangunkusumo National General Hospital from December 2018 to March 2019. The gut microbiota was investigated in fecal samples with 16S RNA sequencing using the MiSeq next-generation sequencing platform (Illumina). NAFLD was more common in patients with metabolic syndrome. Firmicutes, Bacteroidetes, and Proteobacteria were the predominant phyla. Bacteroides was more dominant than Prevotella, contrary to the results of previous studies on healthy populations in Indonesia. Microbiota dysbiosis was observed in most samples. The gastrointestinal microbiota diversity was significantly decreased in patients with NAFLD, high triglyceride levels, and central obesity. The Firmicutes/Bacteroidetes ratio correlated with steatosis and obesity, whereas some of the other species in lower taxonomy levels were mostly associated with steatosis and obesity without fibrosis. Proteobacteria was the only phylum strongly correlated with fibrosis in patients with an average body mass index. The gut microbiota diversity was decreased in patients with NAFLD, high triglyceride levels, and central obesity, and certain gut microbes were correlated with fibrosis and steatosis.

Tumor necrosis factor alpha receptor 1 deficiency in hepatocytes does not protect from non-alcoholic steatohepatitis, but attenuates insulin resistance in mice

BACKGROUND

End-stage liver disease caused by non-alcoholic steatohepatitis (NASH) is the second leading indication for liver transplantation. To date, only moderately effective pharmacotherapies exist to treat NASH. Understanding the pathogenesis of NASH is therefore crucial for the development of new therapies. The inflammatory cytokine tumor necrosis factor alpha (TNF-α) is important for the progression of liver disease. TNF signaling via TNF receptor 1 (TNFR1) has been hypothesized to be important for the development of NASH and hepatocellular carcinoma in whole-body knockout animal models.

AIM

To investigate the role of TNFR1 signaling in hepatocytes for steatohepatitis development in a mouse model of diet-induced NASH.

METHODS

NASH was induced by a western-style fast-food diet in mice deficient for TNFR1 in hepatocytes (TNFR1^ΔHEP) and their wild-type littermates (TNFR1^fl/fl). Glucose tolerance was assessed after 18 wk and insulin resistance after 19 wk of feeding. After 20 wk mice were assessed for features of NASH and the metabolic syndrome such as liver weight, liver steatosis, liver fibrosis and markers of liver inflammation.

RESULTS

Obesity, liver injury, inflammation, steatosis and fibrosis was not different between TNFR1^ΔHEP and TNFR1^fl/fl mice. However, Tnfr1 deficiency in hepatocytes protected against glucose intolerance and insulin resistance.

CONCLUSION

Our results indicate that deficiency of TNFR1 signaling in hepatocytes does not protect from diet-induced NASH. However, improved insulin resistance in this model strengthens the role of the liver in glucose homeostasis.

Effects of probiotic and prebiotic supplementation on metabolic parameters, liver aminotransferases, and systemic inflammation in nonalcoholic fatty liver disease: A randomized clinical trial

This study aimed to evaluate the clinical efficacy of probiotic and prebiotic supplementation on the metabolic parameters, liver enzymes, and inflammation in patients with nonalcoholic fatty liver disease (NAFLD). In this study, patients with NAFLD were assigned to receive either probiotic capsule + placebo of prebiotic (probiotic group), oligofructose + placebo of probiotic (prebiotic group), or placebo of probiotic + placebo of prebiotic (control group) for 12 weeks. All participants followed a weight loss diet and physical activity recommendation during intervention. Anthropometric measurements decreased in all three groups, but there was no significant difference among groups. Probiotic supplementation was able to decrease triglyceride, alanine aminotransferase (ALT), aspartate aminotransferase (AST), γ-glutamyltransferase (GGT), and alkaline phosphatase compared to control group. The serum levels of triglyceride, total and low-density lipoprotein cholesterol, ALT, AST, and GGT differed significantly in prebiotic group in comparison to the placebo. High-sensitive C-reactive protein significantly decreased within all groups; however, there was no significant difference among groups after intervention. Probiotic and prebiotic may be beneficial in improving liver enzymes and lipid profile in patients with NAFLD.

Aging and the Biological Response to Liver Injury

Interest in understanding the aging process has recently risen in the scientific community. Aging, commonly defined as the functional decline in the function of organs and tissues, is indeed the major risk factor for the development of many chronic diseases, such as cardiovascular diseases, pathologies of nervous system, or cancer. To date, the influence of aging in the pathophysiology of liver and biliary diseases is not fully understood. Although liver cells have a high regenerative capacity, hepatocytes and cholangiocytes undergo extensive molecular changes in response to aging. Following time-dependent damage induced by aging, liver cells initially activate compensatory mechanisms that, if hyperstimulated, may lead to the decline of regenerative capacity and the development of pathologies. A deeper understanding of molecular aging has undoubtedly the potential to improve the clinical management of patients, possibly unveiling new pathways for selective drug treatment.

Maternal sucralose intake alters gut microbiota of offspring and exacerbates hepatic steatosis in adulthood

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) is considered to be associated with diet and gut dysbiosis. Excessive sucralose can induce gut dysbiosis and negatively affect host health. Maternal diet shapes the microbial communities of neonate and this effect continues in later life. We aimed to investigate the effects of maternal sucralose (MS) intake on the susceptibility of offspring to hepatic steatosis in adulthood.

METHODS

C57BL/6 pregnant mice were randomized into MS group (MS during gestation and lactation) and maternal control (MC) group (MC diet). After weaning, all offspring were fed a control diet until 8 weeks of age, and then treated with a high-fat diet (HFD) for 4 weeks. The intestinal development, mucosal barrier function, and gut microbiota were assessed in the 3-week-old offspring. Moreover, the severity of hepatic steatosis, serum biochemistry, lipid metabolism, and gut microbiota was then assessed in the 12th week.

RESULTS

MS significantly inhibited intestinal development and disrupted barrier function in 3-week-old offspring. MS also induced intestinal low-grade inflammation, significantly changed the compositions and diversity of gut microbiota including reducing butyrate-producing bacteria and cecal butyrate production with down-regulation of GPR43. Mechanically, blocking GPR43 blunted the anti-inflammatory effect of one of the butyrate-producing bacteria, Clostridium butyricum in vitro. After HFD treatment, MS exacerbated hepatic steatosis, and disturbed fatty acid biosynthesis and metabolism, accompanied by inducing gut dysbiosis compared with MC group.

CONCLUSIONS

MS intake inhibits intestinal development, induces gut dysbiosis in offspring through down-regulation of GPR43, and exacerbates HFD-induced hepatic steatosis in adulthood.

Effectiveness of probiotics, prebiotics, and prebiotic-like components in common functional foods

The bioactive ingredients in commonly consumed foods include, but are not limited to, prebiotics, prebiotic-like components, probiotics, and postbiotics. The bioactive ingredients in functional foods have also been associated with beneficial effects on human health. For example, they aid in shaping of gut microflora and promotion of immunity. These functional components also contribute in preventing serious diseases such as cardiovascular malfunction and tumorigenesis. However, the specific mechanisms of these positive influences on human health are still under investigation. In this review, we aim to emphasize the major contents of probiotics, prebiotics, and prebiotic-like components commonly found in consumable functional foods, and we present an overview of direct and indirect benefits they provide on human health. The major contributors are certain families of metabolites, specifically short-chain fatty acids and polyunsaturated fatty acids produced by probiotics, and prebiotics, or prebiotic-like components such as flavonoids, polyphenols, and vitamins that are found in functional foods. These functional ingredients in foods influence the gut microbiota by stimulating the growth of beneficial microbes and the production of beneficial metabolites that, in turn, have direct benefits to the host, while also providing protection from pathogens and maintaining a balanced gut ecosystem. The complex interactions that arise among functional food ingredients, human physiology, the gut microbiota, and their respective metabolic pathways have been found to minimize several factors that contribute to the incidence of chronic disease, such as inflammation oxidative stress.

Impact of short-term overfeeding of saturated or unsaturated fat or sugars on the gut microbiota in relation to liver fat in obese and overweight adults

BACKGROUNDS & AIMS

Intestinal microbiota may be causally involved in the pathogenesis of non-alcoholic fatty liver disease (NAFLD). We aimed to study the effect of short-term overfeeding on human gut microbiota in relation to baseline and overfeeding-induced liver steatosis. We also asked whether the baseline microbiota composition is associated to the overfeeding-induced increase in liver fat.

METHODS

In a randomized trial, 38 overweight and obese subjects were assigned to consume an excess of 1000 kcal/day of diets rich in either saturated fat, unsaturated fat, or simple sugars for 3 weeks. Fasting blood samples and ¹H-MR spectroscopy were used for extensive clinical phenotyping as previously reported (PMID: 29844096). Fecal samples were collected for the analysis of the gut microbiota using 16S rRNA amplicon sequencing, imputed metagenomics and qPCR. Microbiota results were correlated with dietary intakes and clinical measurements before and during overfeeding.

RESULTS

The overall community structure of the microbiota remained highly stable and personalized during overfeeding based on between-sample Bray-Curtis dissimilarity, but the relative abundances of individual taxa were altered in a diet-specific manner: overfeeding saturated fat increased Proteobacteria, while unsaturated fat increased butyrate producers. Sugar overfeeding increased Lactococcus and Escherichia coli. Imputed functions of the gut microbiota were not affected by overfeeding. Several taxa affected by overfeeding significantly correlated with the changes in host metabolic markers. The baseline levels of proteobacterial family Desulfovibrionaceae, and especially genus Bilophila, were significantly associated to overfeeding-induced liver fat increase independently of the diet arm. In general, limited overlap was observed between the overfeeding-induced microbiota changes and the liver fat-associated microbiota features at baseline.

CONCLUSIONS

Our work indicates that the human gut microbiota is resilient to short-term overfeeding on community level, but specific taxa are altered on diet composition-dependent manner. Generalizable microbiota signatures directly associated with liver steatosis could not be identified. Instead, the carriage of Bilophila was identified as a potential novel risk factor for diet-induced liver steatosis in humans. Clinical trial registry number: NCT02133144 listed on NIH website: ClinicalTrials.gov.

Gut microbiota and human NAFLD: disentangling microbial signatures from metabolic disorders

Gut microbiota dysbiosis has been repeatedly observed in obesity and type 2 diabetes mellitus, two metabolic diseases strongly intertwined with non-alcoholic fatty liver disease (NAFLD). Animal studies have demonstrated a potential causal role of gut microbiota in NAFLD. Human studies have started to describe microbiota alterations in NAFLD and have found a few consistent microbiome signatures discriminating healthy individuals from those with NAFLD, non-alcoholic steatohepatitis or cirrhosis. However, patients with NAFLD often present with obesity and/or insulin resistance and type 2 diabetes mellitus, and these metabolic confounding factors for dysbiosis have not always been considered. Patients with different NAFLD severity stages often present with heterogeneous lesions and variable demographic characteristics (including age, sex and ethnicity), which are known to affect the gut microbiome and have been overlooked in most studies. Finally, multiple gut microbiome sequencing tools and NAFLD diagnostic methods have been used across studies that could account for discrepant microbiome signatures. This Review provides a broad insight into microbiome signatures for human NAFLD and explores issues with disentangling these signatures from underlying metabolic disorders. More advanced metagenomics and multi-omics studies using system biology approaches are needed to improve microbiome biomarkers.

Peri-transplant renal dysfunction in patients with non-alcoholic steatohepatitis undergoing liver transplantation

Non-alcoholic fatty liver disease (NAFLD) is currently the most common etiology of chronic liver disease (CLD) caused by an accumulation of fat in the liver and globally is the leading indication of liver transplantation. Emerging data has recognized an increased association of NAFLD with risk of other metabolic liver diseases like type 2 diabetes mellitus, chronic kidney disease (CKD) and cardiovascular diseases. Pathophysiologically, NAFLD patients have a state of low-grade systemic inflammation, insulin resistance and atherogenic dyslipidemia which causes renal dysfunction. Patients with NAFLD cirrhosis awaiting liver transplant (LT) face unique challenges and have a significantly higher requirement of simultaneous-liver-kidney transplant as compared to other etiologies. Further, NAFLD not only recurs but also occurs as a de novo manifestation post-LT. There is also a significantly higher risk of waiting list stagnation and dropouts due to burdensome cardiometabolic disorders in NAFLD patients. The current review aims to understand the prevalence and pathogenetic basis of renal dysfunction in NAFLD. Additionally, the review describes the choice of immunosuppression protocols and use of intraoperative renal replacement therapy in context of intra and post-operative renal dysfunction in NAFLD patients. Prospective controlled trials focusing on NAFLD and development of CKD are needed to assess the existence of a causal and/or a bidirectional relationship between NAFLD and CKD.

NAFLD as a driver of chronic kidney disease

Non-alcoholic fatty liver disease (NAFLD) and chronic kidney disease (CKD) are worldwide public health problems, affecting up to 25-30% (NAFLD), and up to 10-15% (CKD) of the general population. Recently, it has also been established that there is a strong association between NAFLD and CKD, regardless of the presence of potential confounding diseases such as obesity, hypertension and type 2 diabetes. Since NAFLD and CKD are both common diseases that often occur alongside other metabolic conditions, such as type 2 diabetes or metabolic syndrome, elucidating the relative impact of NAFLD on the risk of incident CKD presents a substantial challenge for investigators working in this research field. A growing body of epidemiological evidence suggests that NAFLD is an independent risk factor for CKD and recent evidence also suggests that associated factors such as metabolic syndrome, dysbiosis, unhealthy diets, platelet activation and processes associated with ageing could also contribute mechanisms linking NAFLD and CKD. This narrative review provides an overview of the literature on: a) the evidence for an association and causal link between NAFLD and CKD and b) the underlying mechanisms by which NAFLD (and factors strongly linked with NAFLD) may increase the risk of developing CKD.

Gut microbiota in non-alcoholic fatty liver disease and alcohol-related liver disease: Current concepts and perspectives

The term, gut-liver axis, is used to highlight the close anatomical and functional relationship between the intestine and the liver. It has been increasingly recognized that the gut-liver axis plays an essential role in the development and progression of liver disease. In particular, in non-alcoholic fatty liver disease and alcohol-related liver disease, the two most common causes of chronic liver disease, a dysbiotic gut microbiota can influence intestinal permeability, allowing some pathogens or bacteria-derived factors from the gut reaching the liver through the enterohepatic circulation contributing to liver injury, steatohepatitis, and fibrosis progression. Pathways involved are multiple, including changes in bile acid metabolism, intestinal ethanol production, generation of short-chain fatty acids, and other by-products. Bile acids act through dedicated bile acid receptors, farnesoid X receptor and TGR5, in both the ileum and the liver, influencing lipid metabolism, inflammation, and fibrogenesis. Currently, both non-alcoholic fatty liver disease and alcohol-related liver disease lack effective therapies, and therapeutic targeting of gut microbiota and bile acids enterohepatic circulation holds promise. In this review, we summarize current knowledge about the role of gut microbiota in the pathogenesis of non-alcoholic fatty liver disease and alcohol-related liver disease, as well as the relevance of microbiota or bile acid-based approaches in the management of those liver diseases.

Abnormal Intestinal Microbiome in Medical Disorders and Potential Reversibility by Fecal Microbiota Transplantation

Reduction in diversity of the intestinal microbiome (dysbiosis) is being identified in many disease states, and studies are showing important biologic contributions of microbiome to health and disease. Fecal microbiota transplantation (FMT) is being evaluated as a way to reverse dysbiosis in diseases and disorders in an attempt to improve health. The published literature was reviewed to determine the value of FMT in the treatment of medical disorders for which clinical trials have recently been conducted. FMT is effective in treating recurrent C. difficile infection in one or two doses, with many healthy donors providing efficacious fecal-derived products. In inflammatory bowel disease (IBD), FMT may lead to remission in approximately one-third of moderate-to-severe illnesses with one study suggesting that more durable FMT responses may be seen when used once medical remissions have been achieved. Donor products differ in their efficacy in treatment of IBD. Combining donor products has been one way to increase the potential value of FMT in treating chronic disorders. FMT is being explored in a variety of clinical settings affecting different organ systems outside CDI, with positive preliminary signals, in treatment of functional constipation, immunotherapy-induced colitis, neurodegenerative disease, as well as prevention of cancer-related disorders like graft versus host disease and decolonization of patients with recurrent urinary tract infection due to antibiotic-resistant bacteria. Currently, intense research is underway to see how the microbiome products like FMT can be harnessed for health benefits.

Bile acid sequestration reverses liver injury and prevents progression of nonalcoholic steatohepatitis in Western diet-fed mice

Nonalcoholic fatty liver disease is a rapidly rising problem in the 21st century and is a leading cause of chronic liver disease that can lead to end-stage liver diseases, including cirrhosis and hepatocellular cancer. Despite this rising epidemic, no pharmacological treatment has yet been established to treat this disease. The rapidly increasing prevalence of nonalcoholic fatty liver disease and its aggressive form, nonalcoholic steatohepatitis (NASH), requires novel therapeutic approaches to prevent disease progression. Alterations in microbiome dynamics and dysbiosis play an important role in liver disease and may represent targetable pathways to treat liver disorders. Improving microbiome properties or restoring normal bile acid metabolism may prevent or slow the progression of liver diseases such as NASH. Importantly, aberrant systemic circulation of bile acids can greatly disrupt metabolic homeostasis. Bile acid sequestrants are orally administered polymers that bind bile acids in the intestine, forming nonabsorbable complexes. Bile acid sequestrants interrupt intestinal reabsorption of bile acids, decreasing their circulating levels. We determined that treatment with the bile acid sequestrant sevelamer reversed the liver injury and prevented the progression of NASH, including steatosis, inflammation, and fibrosis in a Western diet-induced NASH mouse model. Metabolomics and microbiome analysis revealed that this beneficial effect is associated with changes in the microbiota population and bile acid composition, including reversing microbiota complexity in cecum by increasing Lactobacillus and decreased Desulfovibrio The net effect of these changes was improvement in liver function and markers of liver injury and the positive effects of reversal of insulin resistance.

Fatty liver in pregnancy: a narrative review of two distinct conditions

Introduction: Fatty liver is rather common in pregnancy, occurring in two totally different conditions, i.e. nonalcoholic fatty liver disease (NAFLD) in pregnancy and acute fatty liver of pregnancy (AFLP). The former is a common condition, resulting by chance association because of the epidemics of obesity and the older age of many pregnant women in Western countries; the latter is a rare disease whose pathophysiology is still incompletely understood.Areas covered: We reviewed the evidence-based knowledge on fatty liver in/of pregnancy. For NAFLD, a few large retrospective and prospective studies identify immediate and late risks for both the mother and the fetus. For AFLP, only small retrospective studies are available, indicating that prompt delivery and eventual referral to Liver Units for liver support or transplantation are mandatory to avoid maternal and fetal death.Expert opinion: The number of pregnant women with fatty liver is expected to increase in the next years. Pharmacologic treatment of NAFLD might be postponed, even when new drugs are approved by health authorities for the general population. In the case of AFLP, we need to improve our ability to correctly identify and treat the most severe cases not resolving with delivery.

Sarcodon aspratus polysaccharides ameliorated obesity-induced metabolic disorders and modulated gut microbiota dysbiosis in mice fed a high-fat diet

The polysaccharides isolated from the fruit body of S. aspratus (SATPs) might be a potential health supplement or prebiotic in the prevention of obesity and associated metabolic disorders.

Role of gut microbiota in liver disease

The gut microbiome is the natural intestinal inhabitant that has been recognized recently as a major player in the maintenance of human health and the pathophysiology of many diseases. Those commensals produce metabolites that have various effects on host biological functions. Therefore, alterations in the normal composition or diversity of microbiome have been implicated in various diseases, including liver cirrhosis and nonalcoholic fatty liver disease. Moreover, accumulating evidence suggests that progression of dysbiosis can be associated with worsening of liver disease. Here, we review the possible roles for gut microbiota in the development, progression, and complication of liver disease.

[Non - alcoholic fatty liver disease and enteral insufficiency: comorbidity of their development]

The article reflects current literature data on the epidemiology and risk factors of non - alcoholic fatty liver disease. An important aspect is the description of the modern views of combined lesions of the hepatobiliary tract and small intestine. Disorders of the intestinal microbiota play a special role in the development of non - alcoholic fatty liver disease. The value of enterohepatic circulation of bile acids in the development of intestinal and liver diseases was shown. It seems relevant to further study the comorbidity of the development of non - alcoholic fatty liver disease and enteropathy for the development of pathogenetically substantiated therapy.

Non-alcoholic fatty liver diseases: from role of gut microbiota to microbial-based therapies

Non-alcoholic fatty liver disease (NAFLD) is the well-known disease of the liver in adults and children throughout the world. The main manifestations related to NAFLD are an unusual storage of lipid in hepatocytes (hepatic steatosis) and progression of inflammation for non-alcoholic steatohepatitis (NASH). NAFLD is described as a multifactorial complication due to the genetic predisposition, metabolic functions, inflammatory, gut microbiota (GM), and environmental factors. The GM dysregulation among these factors is correlated to NAFLD development. In recent decades, advanced microbial profiling methods are continuing to shed light on the nature of the changes in the GM caused by NASH and NAFLD. In the current review, we aim to perform a literature review in different library databases and electronic searches (Science Direct, PubMed, and Google Scholar) which were randomly obtained. This will be done in order to provide an overview of the relation between GM and NAFLD, and the role of prebiotics, probiotics, and fecal microbiota transplantation (FMT), as potential therapeutic challenges for NAFLD.

Prebiotic and probiotic treatment of nonalcoholic fatty liver disease: a systematic review and meta-analysis

Context

Nonalcoholic fatty liver disease (NAFLD) is a highly prevalent and underdiagnosed comorbidity of many chronic diseases that is associated with altered intestinal bacterial communities. This association has prompted research into alternative treatments aimed at modulating intestinal microbiota. Given the novelty of these treatments, scarce evidence regarding their effectiveness in clinical populations exists.

Objective

This meta-analysis sought to systemically review and quantitatively synthesize evidence on prebiotic, probiotic, and synbiotic therapies for patients with NAFLD in randomized controlled trials.

Data sources

PRISMA guidelines ensured transparent reporting of evidence. PICOS criteria defined the research question for the systematic review. A systematic keyword search in PubMed and EMBASE identified 25 studies: 9 assessed prebiotic, 11 assessed probiotic, and 7 assessed symbiotic therapies for a total of 1309 patients.

Data extraction

Basic population characteristics, the primary variables of aspartate aminotransferase (AST) and alanine aminotransferase (ALT) (utilized for NAFLD diagnosis), and the secondary variables of body mass index (BMI), gamma-glutamyl transferase (γ-GT), tumor necrosis factor alpha (TNF-α), C-reactive protein (CRP), total cholesterol, high-density lipoprotein cholesterol (HDL-c), low-density lipoprotein cholesterol (LDL-c), and triglyceridges (TAG) were extracted. Pooled effect sizes of these variables were calculated by meta-analysis. No publication bias was identified using Begg's and Egger's tests or Cochrane bias assessment tool.

Results

Meta-analysis indicated that microbial therapies significantly reduced BMI (-0.37 kg/m2; 95% confidence interval [CI], -0.46 to -0.28; P < 0.001), hepatic enzymes (ALT, -6.9 U/L [95%CI, -9.4 to -4.3]; AST, -4.6 U/L [95%CI, -6.6 to -2.7]; γ-GT, -7.9 U/L [95%CI, -11.4 to -4.4]; P < 0.001), serum cholesterol (-10.1 mg/dL 95%CI, -13.6 to -6.6; P < 0.001), LDL-c (-4.5 mg/dL; 95%CI, -8.9 to -0.17; P < 0.001), and TAG (-10.1 mg/dL; 95%CI, -18.0 to -2.3; P < 0.001), but not inflammation (TNF-α, -2.0 ng/mL; [95%CI, -4.7 to 0.61]; CRP, -0.74 mg/L [95%CI, -1.9 to 0.37]). Subgroup analysis by treatment category indicated similar effects of prebiotics and probiotics on BMI and liver enzymes but not total cholesterol, HDL-c, and LDL-c.

Conclusion

This meta-analysis supports the potential use of microbial therapies in the treatment of NAFLD and sheds light on their potential mode of action. Further research into these treatments should consider the limitations of biomarkers currently used for the diagnosis and progression of NAFLD, in addition to the inherent challenges of personalized microbial-based therapies.

Relationship between Changes in Microbiota and Liver Steatosis Induced by High-Fat Feeding-A Review of Rodent Models

Several studies have observed that gut microbiota can play a critical role in nonalcoholic fatty liver disease (NAFLD) and nonalcoholic steatohepatitis (NASH) development. The gut microbiota is influenced by different environmental factors, which include diet. The aim of the present review is to summarize the information provided in the literature concerning the impact of changes in gut microbiota on the effects which dietary fat has on liver steatosis in rodent models. Most studies in which high-fat feeding has induced steatosis have reported reduced microbiota diversity, regardless of the percentage of energy provided by fat. At the phylum level, an increase in Firmicutes and a reduction in Bacteroidetes is commonly found, although widely diverging results have been described at class, order, family, and genus levels, likely due to differences in experimental design. Unfortunately, this fact makes it difficult to reach clear conclusions concerning the specific microbiota patterns associated with this feeding pattern. With regard to the relationship between high-fat feeding-induced changes in liver and microbiota composition, although several mechanisms such as alteration of gut integrity and increased permeability, inflammation, and metabolite production have been proposed, more scientific evidence is needed to address this issue and thus further studies are needed.

Review article: can bugs be drugs? The potential of probiotics and prebiotics as treatment for non-alcoholic fatty liver disease

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD) has become the most common chronic liver condition. A major current research effort is ongoing to find potential strategies to treat NAFLD-non-alcoholic steatohepatitis (NASH), with special attention to the gut microbiota. Multiple animal studies and pilot clinical trials are assessing different gut microbiota modulating strategies such as faecal microbiota transplantation, antibiotics, probiotics, prebiotics and synbiotics.

AIM

To review the role of microbiota in NAFLD-NASH and determine whether pro- and prebiotics have potential as treatment METHODS: Information was obtained from critically reviewing literature on PubMed on targeting the gut microbiota in NAFLD. Search terms included NAFLD, NASH, non-alcoholic fatty liver disease, steatohepatitis; combined with microbiome, microbiota, gut bacteria, probiotics and prebiotics.

RESULTS

Animal studies and the first emerging studies in humans show promising results for both the common probiotics Lactobacillus, Bifidobacterium and Streptococci as for short chain fatty acid (SCFA) butyrate-producing bacteria. Also, prebiotics have positive effects on different mechanisms underlying NAFLD-NASH.

CONCLUSIONS

The most promising strategies thus far developed to alter the microbiome in NAFLD-NASH are probiotics and prebiotics. However, pre- and probiotic treatment of NAFLD-NASH is relatively new and still under development. Actual understanding of the involved mechanisms is lacking and changes in the intestinal microbiota composition after treatment are rarely measured. Furthermore, large clinical trials with comparative endpoints are unavailable. Personalised treatment based on metagenomics gut microbiota analysis will probably be part of the future diagnosis and treatment of NAFLD-NASH.