Western diet-induced increase in colonic bile acids compromises epithelial barrier in nonalcoholic steatohepatitis

Bovine milk osteopontin improved intestinal health of pregnant rats fed a high-fat diet through improving bile acid metabolism

The main purpose of the current study was to investigate the ameliorative effects of bovine milk osteopontin (bmOPN) on the gut dysfunction of pregnant rats fed a high-fat diet (HFD). Bovine milk osteopontin was supplemented at a dose of 6 mg/kg body weight. Bovine milk osteopontin supplementation during pregnancy reduced colonic inflammation of HFD dams, and it also increased the colonic expression of ZO-1 and claudin-4 of HFD dams. Bovine milk osteopontin significantly enriched the relative abundance of Bacteroidetes, whereas it decreased Proteobacteria, Helicobacteraceae, and Desulfovibrionaceae in feces of HFD dams. The levels of isobutyric acid and pentanoic acid in the HFD + bmOPN group were higher than that of the HFD group. Functional predication analysis of microbial genomes revealed that bmOPN supplementation to HFD pregnancies changed 4 Kyoto Encyclopedia of Genes and Genomes pathways including bile acid biosynthesis. Further, bmOPN enriched hepatic taurochenodeoxycholic acid and tauroursodeoxycholic acid plus taurohyodeoxycholic acid in the gut of HFD maternal rats. Our findings suggested that bmOPN improved the gut health of HFD pregnant rats partially through modulating bile acid biosynthesis.

Physical exercise plays a role in rebalancing the bile acids of enterohepatic axis in non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) is considered as one of the most common diseases of lipid metabolism disorders, which is closely related to bile acids disorders and gut microbiota disorders. Bile acids are synthesized from cholesterol in the liver, and processed by gut microbiota in intestinal tract, and participate in metabolic regulation through the enterohepatic circulation. Bile acids not only promote the consumption and absorption of intestinal fat but also play an important role in biological metabolic signaling network, affecting fat metabolism and glucose metabolism. Studies have demonstrated that exercise plays an important role in regulating the composition and function of bile acid pool in enterohepatic axis, which maintains the homeostasis of the enterohepatic circulation and the health of the host gut microbiota. Exercise has been recommended by several health guidelines as the first-line intervention for patients with NAFLD. Can exercise alter bile acids through the microbiota in the enterohepatic axis? If so, regulating bile acids through exercise may be a promising treatment strategy for NAFLD. However, the specific mechanisms underlying this potential connection are largely unknown. Therefore, in this review, we tried to review the relationship among NAFLD, physical exercise, bile acids, and gut microbiota through the existing data and literature, highlighting the role of physical exercise in rebalancing bile acid and microbial dysbiosis.

GW9662 ameliorates nonalcoholic steatohepatitis by inhibiting the PPARγ/CD36 pathway and altering the gut microbiota

BACKGROUND & AIMS

Peroxisome proliferator-activated receptors (PPARs) are currently among the most focused-on therapeutic targets for non-alcoholic steatohepatitis (NASH), although no clinical transformation has been achieved to date. In this study, we aimed to evaluate the effects of GW9662 on choline-deficient, L-amino acid-defined high-fat diet (CDAA-HFD)-induced NASH mice and reveal the mechanism underlying this effect.

METHODS

GW9662 (1 mg/kg) was administered in CDAA-HFD mouse model of NASH. The effect of GW9662 on hepatic lipid metabolism was investigated using liver RNA-seq and HepG2 cells induced by oleic acid and palmitic acid. In addition, 16S rRNA gene sequencing was performed to analyze the effects of GW9662 on the composition and function of the fecal microbiota.

RESULTS

GW9662 improved the CDAA-HFD caused elevation in the levels of ALT, AST, hepatic free fatty acids and triglycerides. The liver pathological analysis indicated that GW9662 alleviated the hepatic steatosis and fibrosis. The NAFLD activity score and RNA-Seq revealed that GW9662 mainly regulated the fatty acids transport and lipid synthesis by inhibiting PPARγ, CD36, FABP1, FASN, and SCD1, and through the up-regulation of PPARα. Moreover, GW9662 reduced the epididymal fat weight. GW9662 reversed the gut microbiota disorder by increasing the abundance of the beneficial bacteria Dubosiella and Lactobacillus and decreasing the abundance of harmful bacteria Lachnospiraceae_NK4A136_group, Helicobacteraceae, Desulfovibriaceae, and Rickenaceae.

CONCLUSIONS

GW9662 ameliorated lipid metabolism by inhibiting the PPARγ/CD36 pathway and altering the composition of the gut microbiota in NASH mice. Therefore, the PPARγ antagonist GW9662 deserves more attention as a potential therapeutic agent for NASH.

Exome sequencing reveals IFT172 variants in patients with non-syndromic cholestatic liver disease

BACKGROUND AND AIM

Gene defects contribute to the aetiology of intrahepatic cholestasis. We aimed to explore the outcome of whole-exome sequencing (WES) in a cohort of 51 patients with this diagnosis.

PATIENTS AND METHODS

Both paediatric (n = 33) and adult (n = 18) patients with cholestatic liver disease of unknown aetiology were eligible. WES was used for reassessment of 34 patients (23 children) without diagnostic genotypes in ABCB11, ATP8B1, ABCB4 or JAG1 demonstrable by previous Sanger sequencing, and for primary assessment of additional 17 patients (10 children). Nasopharyngeal swab mRNA was analysed to address variant pathogenicity in two families.

RESULTS

WES revealed biallelic variation in 3 ciliopathy genes (PKHD1, TMEM67 and IFT172) in 4 clinically unrelated index subjects (3 children and 1 adult), heterozygosity for a known variant in PPOX in one adult index subject, and homozygosity for an unreported splice-site variation in F11R in one child. Whereas phenotypes of the index patients with mutated PKHD1, TMEM67, and PPOX corresponded with those elsewhere reported, how F11R variation underlies liver disease remains unclear. Two unrelated patients harboured different novel biallelic variants in IFT172, a gene implicated in short-rib thoracic dysplasia 10 and Bardet-Biedl syndrome 20. One patient, a homozygote for IFT172 rs780205001 c.167A>C p.(Lys56Thr) born to first cousins, had liver disease, interpreted on biopsy aged 4y as glycogen storage disease, followed by adult-onset nephronophthisis at 25y. The other, a compound heterozygote for novel frameshift variant IFT172 NM_015662.3 c.2070del p.(Met690Ilefs*11) and 2 syntenic missense variants IFT172 rs776310391 c.157T>A p.(Phe53Ile) and rs746462745 c.164C>G p.(Thr55Ser), had a severe 8mo cholestatic episode in early infancy, with persisting hyperbilirubinemia and fibrosis on imaging studies at 17y. No patient had skeletal malformations.

CONCLUSION

Our findings suggest association of IFT172 variants with non-syndromic cholestatic liver disease.

Gut-liver axis in the progression of nonalcoholic fatty liver disease: From the microbial derivatives-centered perspective

Nonalcoholic fatty liver disease (NAFLD) is one of the world's most common chronic liver diseases. However, its pathogenesis remains unclear. With the deepening of research, NAFLD is considered a metabolic syndrome associated with the environment, heredity, and metabolic disorders. Recently, the close relationship between the intestinal microbiome and NAFLD has been discovered, and the theory of the "gut-liver axis" has been proposed. In short, the gut bacteria directly reach the liver via the portal vein through the damaged intestinal wall or indirectly participate in the development of NAFLD through signaling pathways mediated by their components and metabolites. This review focuses on the roles of microbiota-derived lipopolysaccharide, DNA, peptidoglycan, bile acids, short-chain fatty acids, endogenous ethanol, choline and its metabolites, indole and its derivatives, and bilirubin and its metabolites in the progression of NAFLD, which may provide significative insights into the pathogenesis, diagnosis, and treatment for this highly prevalent liver disease.

Research progress of gut microbiota and obesity caused by high-fat diet

Obesity, a chronic metabolic disorder caused by an energy imbalance, has been increasingly prevalent and poses a global health concern. The multifactorial etiology of obesity includes genetics factors, high-fat diet, gut microbiota, and other factors. Among these factors, the implication of gut microbiota in the pathogenesis of obesity has been prominently acknowledged. This study endeavors to investigate the potential contribution of gut microbiota to the development of high-fat diet induced obesity, as well as the current state of probiotic intervention therapy research, in order to provide novel insights for the prevention and management of obesity.

Inhibition of microbial deconjugation of micellar bile acids protects against intestinal permeability and liver injury

Altered host-microbe interactions and increased intestinal permeability have been implicated in disease pathogenesis. However, the mechanisms by which intestinal microbes affect epithelial barrier integrity remain unclear. Here, we investigate the impact of bacterial metabolism of host-produced bile acid (BA) metabolites on epithelial barrier integrity. We observe that rats fed a choline-deficient, l-amino acid-defined, high-fat diet (CDAHFD) exhibit reduced intestinal abundance of host-produced conjugated BAs at early time points, coinciding with increased gut permeability. We show that in vitro, conjugated BAs protect gut epithelial monolayers from damage caused by bacterially produced unconjugated BAs through micelle formation. We then demonstrate that inhibition of bacterial BA deconjugation with a small-molecule inhibitor prevents the development of pathologic intestinal permeability and hepatic inflammation in CDAHFD-fed rats. Our study identifies a signaling-independent, physicochemical mechanism for conjugated BA-mediated protection of epithelial barrier function and suggests that rational manipulation of microbial BA metabolism could be leveraged to regulate gut barrier integrity.

Targeted therapeutics and novel signaling pathways in non-alcohol-associated fatty liver/steatohepatitis (NAFL/NASH)

Non-alcohol-associated fatty liver/steatohepatitis (NAFL/NASH) has become the leading cause of liver disease worldwide. NASH, an advanced form of NAFL, can be progressive and more susceptible to developing cirrhosis and hepatocellular carcinoma. Currently, lifestyle interventions are the most essential and effective strategies for preventing and controlling NAFL without the development of fibrosis. While there are still limited appropriate drugs specifically to treat NAFL/NASH, growing progress is being seen in elucidating the pathogenesis and identifying therapeutic targets. In this review, we discussed recent developments in etiology and prospective therapeutic targets, as well as pharmacological candidates in pre/clinical trials and patents, with a focus on diabetes, hepatic lipid metabolism, inflammation, and fibrosis. Importantly, growing evidence elucidates that the disruption of the gut-liver axis and microbe-derived metabolites drive the pathogenesis of NAFL/NASH. Extracellular vesicles (EVs) act as a signaling mediator, resulting in lipid accumulation, macrophage and hepatic stellate cell activation, further promoting inflammation and liver fibrosis progression during the development of NAFL/NASH. Targeting gut microbiota or EVs may serve as new strategies for the treatment of NAFL/NASH. Finally, other mechanisms, such as cell therapy and genetic approaches, also have enormous therapeutic potential. Incorporating drugs with different mechanisms and personalized medicine may improve the efficacy to better benefit patients with NAFL/NASH.

Intestinal Barrier Dysfunction in Fatty Liver Disease: Roles of Microbiota, Mucosal Immune System, and Bile Acids

Nonalcoholic fatty liver disease (NAFLD) describes a spectrum of progressive liver diseases ranging from simple steatosis to steatohepatitis and fibrosis. Globally, NAFLD is the leading cause of morbidity and mortality associated with chronic liver disease, and NAFLD patients are at a higher risk of developing cirrhosis and hepatocellular carcinoma. While there is a consensus that inflammation plays a key role in promoting NAFLD progression, the underlying mechanisms are not well understood. Recent clinical and experimental evidence suggest that increased hepatic translocation of gut microbial antigens, secondary to diet-induced impairment of the intestinal barrier may be important in driving hepatic inflammation in NAFLD. Here, we briefly review various endogenous and exogenous factors influencing the intestinal barrier and present recent advances in our understanding of cellular and molecular mechanisms underlying intestinal barrier dysfunction in NAFLD.

Bile acid detergency: permeability, inflammation, and effects of sulfation

Bile acids are amphipathic, detergent molecules. The detergent effects of di-α-hydroxy-bile acids are relevant to several colonic diseases. The aims were to review the concentrations of bile acids reaching the human colon in health and disease, the molecular structure of bile acids that determine detergent functions and the relationship to human diseases (neuroendocrine tumors, microscopic colitis, active celiac disease, and ulcerative colitis, Crohn's disease and ileal resection), the relationship to bacterial uptake into the mucosa, mucin depletion, and epithelial damage, the role of bile acids in mucosal inflammation and microscopic colitis, and the role of sulfation of bile salts in detoxification or prevention of the detergent effects of bile acids. The concentrations of bile acids reaching the human colon range from 2 to 10 mM; di-α-hydroxy bile acids are the only bile acids with detergent effects that include mucin depletion, mucosal damage, bacterial uptake, and microscopic inflammation that may be manifest in diseases associated with no overt inflammation of the mucosa, such as bile acid diarrhea, ileal diseases such as neuroendocrine tumors, ileal resection, and nonalcoholic steatohepatitis. Sulfation inactivates colonic secretion due to primary bile acids, but it may render secondary bile acids proinflammatory in the colon. Other evidence in preclinical models of inflammatory bowel disease (IBD) suggests reduced sulfation causes barrier dysfunction, inflammation, or carcinogenesis. These advances emphasize relevance and opportunities afforded by greater understanding of the chemistry and metabolism of bile acids, which stands to be further enhanced by research into the metabolic interactions of microbiota with bile acids.

Polygoni Multiflori Radix Praeparata Ethanol Extract Exerts a Protective Effect Against High-Fat Diet Induced Non-Alcoholic Fatty Liver Disease in Mice by Remodeling Intestinal Microbial Structure and Maintaining Metabolic Homeostasis of Bile Acids

In the prescription of Traditional Chinese Medicine for lipid metabolism, Polygoni Multiflori Radix Preparata (ZhiHeShouWu, RPMP) was widely used. In recent years, RPMP ethanol extract has been reported for the treatment of non-alcoholic fatty liver disease (NAFLD). However, the role of RPMP ethanol extract in the treatment of NAFLD has not been fully elucidated. Therefore, we examined the optimal therapeutic dose of RPMP ethanol extracts. Afterward, a mouse model of non-alcoholic fatty liver induced by a high-fat diet (HFD) was treated with RPMP ethanol extract to further evaluate the mechanism of action of RPMP ethanol extract treatment. And the serum lipid metabolism indexes and liver function indexes showed that the RPMP ethanol extract in the 1.35 g/kg dose group exhibited better therapeutic effects than the 2.70 g/kg dose group. Meanwhile, RPMP ethanol extract can regulate the biochemical indicators of serum and liver to normal levels, and effectively reduce liver steatosis and lipid deposition. RPMP ethanol extract treatment restored HFD-induced disruption of the compositional structure of the intestinal microbial (IM) and bile acids (BAs) pools. And restore the reduced expression of intestinal barrier-related genes caused by HFD administration, which also effectively regulates the expression of genes related to the metabolism of BAs in mice. Thus, RPMP ethanol extract can effectively improve the abnormal lipid metabolism and hepatic lipid accumulation caused by HFD, which may be related to the regulation of IM composition, maintenance of intestinal barrier function, and normal cholesterol metabolism in the body.

Lactobacillus lactis and Pediococcus pentosaceus-driven reprogramming of gut microbiome and metabolome ameliorates the progression of non-alcoholic fatty liver disease

BACKGROUND

Although microbioa-based therapies have shown putative effects on the treatment of non-alcoholic fatty liver disease (NAFLD), it is not clear how microbiota-derived metabolites contribute to the prevention of NAFLD. We explored the metabolomic signature of Lactobacillus lactis and Pediococcus pentosaceus in NAFLD mice and its association in NAFLD patients.

METHODS

We used Western diet-induced NAFLD mice, and L. lactis and P. pentosaceus were administered to animals in the drinking water at a concentration of 109 CFU/g for 8 weeks. NAFLD severity was determined based on liver/body weight, pathology and biochemistry markers. Caecal samples were collected for the metagenomics by 16S rRNA sequencing. Metabolite profiles were obtained from caecum, liver and serum. Human stool samples (healthy control [n = 22] and NAFLD patients [n = 23]) were collected to investigate clinical reproducibility for microbiota-derived metabolites signature and metabolomics biomarker.

RESULTS

L. lactis and P. pentosaceus supplementation effectively normalized weight ratio, NAFLD activity score, biochemical markers, cytokines and gut-tight junction. While faecal microbiota varied according to the different treatments, key metabolic features including short chain fatty acids (SCFAs), bile acids (BAs) and tryptophan metabolites were analogously restored by both probiotic supplementations. The protective effects of indole compounds were validated with in vitro and in vivo models, including anti-inflammatory effects. The metabolomic signatures were replicated in NAFLD patients, accompanied by the comparable levels of Firmicutes/Bacteroidetes ratio, which was significantly higher (4.3) compared with control (0.6). Besides, the consequent biomarker panel with six stool metabolites (indole, BAs, and SCFAs) showed 0.922 (area under the curve) in the diagnosis of NAFLD.

CONCLUSIONS

NAFLD progression was robustly associated with metabolic dys-regulations in the SCFAs, bile acid and indole compounds, and NAFLD can be accurately diagnosed using the metabolites. L. lactis and P. pentosaceus ameliorate NAFLD progression by modulating gut metagenomic and metabolic environment, particularly tryptophan pathway, of the gut-liver axis.

Gualou Xiebai Decoction ameliorates increased Caco-2 monolayer permeability induced by bile acids via tight junction regulation, oxidative stress suppression and apoptosis reduction

Gualou Xiebai Decoction (GXD), a classic prescription, is widely used to dealing with inflammatory diseases in China for thousands of years. Abnormal metabolic state of bile acids (BAs) is confirmed to cause intestinal epithelial barrier dysfunction. In preliminary work, we observed that GXD could decrease intestinal permeability in hyperlipidemia mice. The present study aimed to explore the protective effect of GXD on intestinal mucosa in vitro. Caco-2 cell monolayer permeability among different groups was determined by measuring the concentrations of FITC-dextran in the lower compartments and transepithelial electrical resistance (TEER). Meanwhile, mRNA and protein expressions of tight junctions (TJs) were investigated. Generation of intracellular reactive oxygen species (ROS) and the ratio of cell apoptosis induced by BAs were assessed by fluorescence probe and flow cytometry. GXD was shown to keep the cell monolayer in low permeable status, increase TEER and mRNA and protein expressions of occludin (Ocln) and zonula occluden 2 (ZO2) remarkably in cells challenged with cholic acid (CA), deoxycholic acid (DCA) and glycocholic acid (GCA). However, no significant effects were uncovered against the pathological effects of taurocholic acid (TCA). Meanwhile, generation of ROS and increased levels of apoptotic cells caused by CA, DCA and GCA were dramatically decreased by GXD, which were not observed on TCA. GXD could significantly attenuate intestinal barrier dysfunction induced by BAs via TJs regulation, oxidative stress suppression and cell apoptosis decrease, but such effects and behind mechanisms differed among different kinds of BAs.

Bile Acid Receptors and the Gut-Liver Axis in Nonalcoholic Fatty Liver Disease

The prevalence of nonalcoholic fatty liver disease (NAFLD) has been significantly increased due to the global epidemic of obesity. The disease progression from simple steatosis (NAFL) to nonalcoholic steatohepatitis (NASH) is closely linked to inflammation, insulin resistance, and dysbiosis. Although extensive efforts have been aimed at elucidating the pathological mechanisms of NAFLD disease progression, current understanding remains incomplete, and no effective therapy is available. Bile acids (BAs) are not only important physiological detergents for the absorption of lipid-soluble nutrients in the intestine but also metabolic regulators. During the last two decades, BAs have been identified as important signaling molecules involved in lipid, glucose, and energy metabolism. Dysregulation of BA homeostasis has been associated with NAFLD disease severity. Identification of nuclear receptors and G-protein-coupled receptors activated by different BAs not only significantly expanded the current understanding of NAFLD/NASH disease progression but also provided the opportunity to develop potential therapeutics for NAFLD/NASH. In this review, we will summarize the recent studies with a focus on BA-mediated signaling pathways in NAFLD/NASH. Furthermore, the therapeutic implications of targeting BA-mediated signaling pathways for NAFLD will also be discussed.

The role of precision nutrition in the modulation of microbial composition and function in people with inflammatory bowel disease

Inflammatory bowel diseases, principally Crohn's disease and ulcerative colitis, are multifactorial chronic conditions. Alterations in gut microbial patterns partly affect disease onset and severity. Moreover, the evolution of dietary patterns, and their effect on gut microbial behaviour, have been shown to play a crucial role in disease processes. This Viewpoint reviews the role of dietary patterns, their influence on the structure and function of the gut microbiome, and their effects on inflammation and immunity in individuals with inflammatory bowel disease. We also discuss innovative dietary intervention strategies, summarise findings that have been used to develop recommendations for clinical practice, and provide suggestions for the design of future studies for development of precision nutrition in patients with inflammatory bowel disease.

Modulation of serotonin in the gut-liver neural axis ameliorates the fatty and fibrotic changes in non-alcoholic fatty liver

The etiology of non-alcoholic fatty liver disease (NAFLD) consists of various factors, including neural signal pathways. However, the molecular mechanisms of the autonomic neural signals influencing NAFLD progression have not been elucidated. Therefore, we examined the involvement of the gut-liver neural axis in NAFLD development and tested the therapeutic effect of modulation of this axis in this study. To test the contribution of the gut-liver neural axis, we examined NAFLD progression with respect to body weight, hepatic steatosis, fibrosis, intestinal tight junction, microbiota and short-chain fatty acids in NAFLD models of choline-deficient defined L-amino-acid and high-fat diet-fed mice with or without blockades of autonomic nerves from the liver. Blockade of the neural signal from the liver to the gut in these NAFLD mice models ameliorated the progression of liver weight, hepatic steatosis and fibrosis by modulating serotonin expression in the small intestine. It was related to the severity of the liver pathology, the tight junction protein expression, microbiota diversity and short-chain fatty acids. These effects were reproduced by administrating serotonin antagonist, which ameliorated the NAFLD progression in the NAFLD mice models. Our study demonstrated that the gut-liver neural axis is involved in the etiologies of NAFLD progression and that serotonin expression through this signaling network is the key factor of this axis. Therefore, modulation of the gut-liver neural axis and serotonin antagonist ameliorates fatty and fibrotic changes in non-alcoholic fatty liver, and can be a potential therapeutic target of NAFLD.This article has an associated First Person interview with the first author of the paper.

Nutritional Components in Western Diet Versus Mediterranean Diet at the Gut Microbiota-Immune System Interplay. Implications for Health and Disease

The most prevalent diseases of our time, non-communicable diseases (NCDs) (including obesity, type 2 diabetes, cardiovascular diseases and some types of cancer) are rising worldwide. All of them share the condition of an "inflammatory disorder", with impaired immune functions frequently caused or accompanied by alterations in gut microbiota. These multifactorial maladies also have in common malnutrition related to physiopathology. In this context, diet is the greatest modulator of immune system-microbiota crosstalk, and much interest, and new challenges, are arising in the area of precision nutrition as a way towards treatment and prevention. It is a fact that the westernized diet (WD) is partly responsible for the increased prevalence of NCDs, negatively affecting both gut microbiota and the immune system. Conversely, other nutritional approaches, such as Mediterranean diet (MD), positively influence immune system and gut microbiota, and is proposed not only as a potential tool in the clinical management of different disease conditions, but also for prevention and health promotion globally. Thus, the purpose of this review is to determine the regulatory role of nutritional components of WD and MD in the gut microbiota and immune system interplay, in order to understand, and create awareness of, the influence of diet over both key components.

Val-Val-Tyr-Pro protects against non-alcoholic steatohepatitis in mice by modulating the gut microbiota and gut-liver axis activation

Val‐Val‐Tyr‐Pro (VVYP) peptide is one of the main active components of Globin digest (GD). Our previous studies indicated that VVYP could protect against acetaminophen and carbon tetrachloride‐induced acute liver failure in mice and decrease blood lipid level. However, the effects and underlying mechanisms of VVYP in the treatment of non‐alcoholic steatohepatitis (NASH) have not been discovered. Our present study was designed to investigate the preventive effect of VVYP on NASH and its underlying specific mechanisms. We found that VVYP inhibited the cytotoxicity and lipid accumulation in L‐02 cells that were exposed to a mixture of free fatty acid (FFA). VVYP effectively alleviated the liver injury induced by methionine‐choline‐deficient (MCD) diet, demonstrated by reducing the levels of serum alanine aminotransferase (ALT)/aspartate aminotransferase (AST)/triglycerides (TG)/non‐esterified fatty acids (NEFA) and improving liver histology. VVYP decreased expression levels of lipid synthesis‐related genes and reduced levels of the proinflammation cytokines in the liver of mice fed by MCD diet. Moreover, VVYP inhibited the increased level of LPS and reversed the liver mitochondria dysfunction induced by MCD diet. Meanwhile, VVYP significantly increased the abundance of beneficial bacteria such as Eubacteriaceae, coriobacteriacease, Desulfovibrionaceae, S24‐7 and Bacteroidia in high‐fat diet (HFD)‐fed mice, however, VVYP reduced the abundance of Lactobacillus. Moreover, VVYP conferred the protective effect of intestinal barrier via promoting the expression of the mucins and tight junction (TJ)‐associated genes and inhibited subsequent liver inflammatory responses. These results indicated that the protective role of VVYP on NASH is mediated by modulating gut microbiota imbalance and related gut‐liver axis activation. VVYP might be a promising drug candidate for NASH.

Supplemental Choline Modulates Growth Performance and Gut Inflammation by Altering the Gut Microbiota and Lipid Metabolism in Weaned Piglets

BACKGROUND

Whether dietary choline and bile acids affect lipid use via gut microbiota is unclear.

OBJECTIVES

This study aimed to investigate the effect of choline and bile acids on growth performance, lipid use, intestinal immunology, gut microbiota, and bacterial metabolites in weaned piglets.

METHODS

A total of 128 weaned piglets [Duroc × (Landrace × Yorkshire), 21-d-old, 8.21 ± 0.20 kg body weight (BW)] were randomly allocated to 4 treatments (8 replicate pens per treatment, each pen containing 2 males and 2 females; n = 32 per treatment) for 28 d. Piglets were fed a control diet (CON) or the CON diet supplemented with 597 mg choline/kg (C), 500 mg bile acids/kg (BA) or both (C + BA) in a 2 × 2 factorial design. Growth performance, intestinal function, gut microbiota, and metabolites were determined.

RESULTS

Compared with diets without choline, choline supplementation increased BW gain (6.13%), average daily gain (9.45%), gain per feed (8.18%), jejunal lipase activity (60.2%), and duodenal IL10 gene expression (51%), and decreased the mRNA abundance of duodenal TNFA (TNFα) (40.7%) and jejunal toll-like receptor 4 (32.9%) (P < 0.05); additionally, choline increased colonic butyrate (29.1%) and the abundance of Lactobacillus (42.3%), while decreasing the bile acid profile (55.8% to 57.6%) and the abundance of Parabacteroides (75.8%), Bacteroides (80.7%), and unidentified-Ruminococcaceae (32.5%) (P ≤ 0.05). Compared with diets without BA, BA supplementation decreased the mRNA abundance of colonic TNFA (37.4%), NF-κB p65 (42.4%), and myeloid differentiation factor 88 (42.5%) (P ≤ 0.01); BA also increased colonic butyrate (20.9%) and the abundance of Lactobacillus (39.7%) and Faecalibacterium (71.6%) and decreased that of Parabacteroides (67.7%) (P < 0.05).

CONCLUSIONS

Choline supplementation improved growth performance and prevented gut inflammation in weaned piglets by altering gut microbiota and lipid metabolism. BA supplementation suppressed intestinal inflammation with no effect on growth performance, which was associated with changed gut microbiota and metabolites.

Modeling dysbiosis of human NASH in mice: Loss of gut microbiome diversity and overgrowth of Erysipelotrichales

Background & aim

Non-alcoholic steatohepatitis (NASH) is a severe form of non-alcoholic fatty liver disease (NAFLD) that is responsible for a growing fraction of cirrhosis and liver cancer cases worldwide. Changes in the gut microbiome have been implicated in NASH pathogenesis, but the lack of suitable murine models has been a barrier to progress. We have therefore characterized the microbiome in a well-validated murine NASH model to establish its value in modeling human disease.

Methods

The composition of intestinal microbiota was monitored in mice on a 12- or 24-week NASH protocol consisting of high fat, high sugar Western Diet (WD) plus once weekly i.p injection of low-dose CCl₄. Additional mice were subjected to WD-only or CCl₄-only conditions to assess the independent effect of these variables on the microbiome.

Results

There was substantial remodeling of the intestinal microbiome in NASH mice, characterized by declines in both species diversity and bacterial abundance. Based on changes to beta diversity, microbiota from NASH mice clustered separately from controls in principal coordinate analyses. A comparison between WD-only and CCl₄-only controls with the NASH model identified WD as the primary driver of early changes to the microbiome, resulting in loss of diversity within the 1^st week. A NASH signature emerged progressively at weeks 6 and 12, including, most notably, a reproducible bloom of the Firmicute order Erysipelotrichales.

Conclusions

We have established a valuable model to study the role of gut microbes in NASH, enabling us to identify a new NASH gut microbiome signature.

Effect of different bile acids on the intestine through enterohepatic circulation based on FXR

Farnesoid X receptor (FXR) is a nuclear receptor for bile acids (BAs) that is widely expressed in the intestine, liver and kidney. FXR has important regulatory impacts on a wide variety of metabolic pathways (such as glucose, lipid, and sterol metabolism) and has been recognized to ameliorate obesity, liver damage, cholestasis and chronic inflammatory diseases. The types of BAs are complex and diverse. BAs link the intestine with the liver through the enterohepatic circulation. BAs derivatives have entered clinical trials for liver disease. In addition to the liver, the intestine is also targeted by BAs. This article reviews the effects of different BAs on the intestinal tract through the enterohepatic circulation from the perspective of FXR, aiming to elucidate the effects of different BAs on the intestinal tract and lay a foundation for new treatment methods.

Gut microbiome, liver immunology, and liver diseases

The gut microbiota is a complex and plastic consortium of microorganisms that are intricately connected with human physiology. The liver is a central immunological organ that is particularly enriched in innate immune cells and constantly exposed to circulating nutrients and endotoxins derived from the gut microbiota. The delicate interaction between the gut and liver prevents accidental immune activation against otherwise harmless antigens. Work on the interplay between the gut microbiota and liver has assisted in understanding the pathophysiology of various liver diseases. Of immense importance is the step from high-throughput sequencing (correlation) to mechanistic studies (causality) and therapeutic intervention. Here, we review the gut microbiota, liver immunology, and the interaction between the gut and liver. In addition, the impairment in the gut-liver axis found in various liver diseases is reviewed here, with an emphasis on alcohol-associated liver disease (ALD), nonalcoholic fatty liver disease (NAFLD), and autoimmune liver disease (AILD). On the basis of growing evidence from these preclinical studies, we propose that the gut-liver axis paves the way for targeted therapeutic modalities for liver diseases.

Inside-Out or Outside-In: Choosing the Right Model of Hepatocellular Cancer

The incidence of hepatocellular cancer (HCC) is gradually rising. HCC occurs as a sequela to various chronic liver diseases and ensuing cirrhosis. There have been many therapies approved for unresectable HCC in the last 5 years, including immune checkpoint inhibitors, and the overall response rates have improved. However, there are many cases that do not respond, and personalized medicine is lacking, making HCC an unmet clinical need. Generation of appropriate animal models have been key to our understanding of HCC. Based on the overall concept of hepatocarcinogenesis, two major categories of animal models are discussed herein that can be useful to address specific questions. One category is described as the outside-in model of HCC and is based on the premise that it takes decades of hepatocyte injury, death, wound healing, and regeneration to eventually lead to DNA damage and mutations in a hepatocyte, which initiates tumorigenesis. Several animal models have been generated, which attempt to recapitulate this complex tissue damage and cellular interplay through genetics, diets, and toxins. The second category is the inside-out model of HCC, where clinically relevant genes can be coexpressed in a small subset of hepatocytes to yield a tumor, which matches HCC subsets in gene expression. This model has been made possible in part by the widely available molecular characterization of HCC, and in part by modalities like sleeping beauty transposon/transposase, Crispr/Cas9, and hydrodynamic tail vein injection. These two categories of HCC have distinct pros and cons, which are discussed in this Thinking Out Loud article.

Phloretin ameliorates hepatic steatosis through regulation of lipogenesis and Sirt1/AMPK signaling in obese mice

Background

Phloretin is isolated from apple trees and could increase lipolysis in 3T3-L1 adipocytes. Previous studies have found that phloretin could prevent obesity in mice. In this study, we investigated whether phloretin ameliorates non-alcoholic fatty liver disease (NAFLD) in high-fat diet (HFD)-induced obese mice, and evaluated the regulation of lipid metabolism in hepatocytes.

Methods

HepG2 cells were treated with 0.5 mM oleic acid to induce lipid accumulation, and then treated with phloretin to evaluate the molecular mechanism of lipogenesis. In another experiment, male C57BL/6 mice were fed normal diet or HFD (60% fat, w/w) for 16 weeks. After the fourth week, mice were treated with or without phloretin by intraperitoneal injection for 12 weeks.

Results

Phloretin significantly reduced excessive lipid accumulation and decreased sterol regulatory element-binding protein 1c, blocking the expression of fatty acid synthase in oleic acid-induced HepG2 cells. Phloretin increased Sirt1, and phosphorylation of AMP activated protein kinase to suppress acetyl-CoA carboxylase expression, reducing fatty acid synthesis in hepatocytes. Phloretin also reduced body weight and fat weight compared to untreated HFD-fed mice. Phloretin also reduced liver weight and liver lipid accumulation and improved hepatocyte steatosis in obese mice. In liver tissue from obese mice, phloretin suppressed transcription factors of lipogenesis and fatty acid synthase, and increased lipolysis and fatty acid β-oxidation. Furthermore, phloretin regulated serum leptin, adiponectin, triglyceride, low-density lipoprotein, and free fatty acid levels in obese mice.

Conclusions

These findings suggest that phloretin improves hepatic steatosis by regulating lipogenesis and the Sirt-1/AMPK pathway in the liver.

Bile Acid Sequestrant, Sevelamer Ameliorates Hepatic Fibrosis with Reduced Overload of Endogenous Lipopolysaccharide in Experimental Nonalcoholic Steatohepatitis

Despite the use of various pharmacotherapeutic strategies, fibrosis due to nonalcoholic steatohepatitis (NASH) remains an unsatisfied clinical issue. We investigated the effect of sevelamer, a hydrophilic bile acid sequestrant, on hepatic fibrosis in a murine NASH model. Male C57BL/6J mice were fed a choline-deficient, L-amino acid-defined, high-fat (CDHF) diet for 12 weeks with or without orally administered sevelamer hydrochloride (2% per diet weight). Histological and biochemical analyses revealed that sevelamer prevented hepatic steatosis, macrophage infiltration, and pericellular fibrosis in CDHF-fed mice. Sevelamer reduced the portal levels of total bile acid and inhibited both hepatic and intestinal farnesoid X receptor activation. Gut microbiome analysis demonstrated that sevelamer improved a lower α-diversity and prevented decreases in Lactobacillaceae and Clostridiaceae as well as increases in Desulfovibrionaceae and Enterobacteriaceae in the CDHF-fed mice. Additionally, sevelamer bound to lipopolysaccharide (LPS) in the intestinal lumen and promoted its fecal excretion. Consequently, the sevelamer treatment restored the tight intestinal junction proteins and reduced the portal LPS levels, leading to the suppression of hepatic toll-like receptor 4 signaling pathway. Furthermore, sevelamer inhibited the LPS-mediated induction of fibrogenic activity in human hepatic stellate cells in vitro. Collectively, sevelamer inhibited the development of murine steatohepatitis by reducing hepatic LPS overload.