Gut microbiome and nonalcoholic fatty liver diseases

Mechanism of liver x receptor alpha in intestine, liver and adipose tissues in metabolic associated fatty liver disease

Metabolism associated fatty liver disease (MAFLD) has emerged as a growing global health challenge with limited effective treatments. Research on nuclear receptors offers promising new therapeutic avenues for MAFLD. The liver X receptor (LXR) has gained attention for its roles in tumors and metabolic and inflammatory diseases; However, its effects on MAFLD treatment remain a subject of debate. This review explores the therapeutic role of LXRα in MAFLD, focusing on its functions in the intestine, hepatic and adipose tissue, and summarizes recent advancements in LXRα ligands over the past five years. In the intestine, LXRα activation enhances the efflux of non-biliary cholesterol and reduces inflammation in the gut-liver axis by regulating intestinal high-density lipoprotein synthesis and its interaction with lipopolysaccharide. In the liver, LXRα activation facilitates cholesterol transport, influences hepatic lipid synthesis, and exerts anti-inflammatory effects. In adipose tissue, LXRα helps delay MAFLD progression by managing lipid autophagy and insulin resistance. Ligands that modulate LXRα transcriptional activity show considerable promise for MAFLD treatment.

Targeting regulation of lipid metabolism with polysaccharide of traditional Chinese medicine for the treatment of non-alcoholic fatty liver disease: A review

Non-alcoholic fatty liver disease (NAFLD) has become one of the most common chronic diseases in the world, and the effective treatment of NAFLD has been listed as a key problem to be solved urgently in contemporary medicine. Polysaccharides in traditional Chinese medicine (TCM) have a wide range of pharmacological activities. A large number of preclinical studies have confirmed that TCM polysaccharides can interfere with the occurrence and development of NAFLD at multiple interrelated levels, such as improving lipid metabolism and insulin resistance, regulating oxidative stress, alleviating immune inflammatory response, and regulating intestinal microbiota, thus showing great potential as a new anti-NAFLD drug. This paper summarizes the prevention and treatment effect and mechanism of TCM polysaccharides on NAFLD, which provides a basis for the application of TCM polysaccharides in plant medicine and modern medicines, and provides a reference for promoting the development and utilization of TCM polysaccharide resources and the research and development of new drugs for NAFLD.

Gut Microbiota and Bile Acid Metabolism in the Mechanism of Ginsenoside Re Against Nonalcoholic Fatty Liver Disease

Gut microbiota and bile acid metabolism play crucial roles in the progression of nonalcoholic fatty liver disease (NAFLD). Early evidence demonstrates that Ginsenoside Re (Re) possesses pharmacological effects on NAFLD, but its mechanisms of action are not well understood. This study aimed to investigate the hepatic protective effects of Re in NAFLD and elucidate relevant mechanisms. The effects of Re treatments (10, 20, or 40 mg/kg) against high-fat diet-induced NAFLD were initially tested on male C57BL/6 mice. Then, a separate mouse group received Re with or without antibiotics to confirm the regulatory role of microbiota in the effect of Re. Finally, another group of mice received fecal microbiota transplantation (FMT) from the initial experiment of NAFLD mice to further investigate the mechanistic role of gut microbiota. Re significantly improved liver function by reducing hepatic lipid accumulation, injury and hepatocyte steatosis, and inflammation. The liver protection was mediated by the regulation of gut microbiota as evidenced by restored intestinal barrier integrity, normalized Firmicutes/Bacteroidota ratio, enhanced abundances of Adlercreutzia equolifaciens , and reduced Faecalibaculum rodentium. Following that, Re reduced total and primary bile acids and downregulated bile acid synthesis genes and proteins such as farnesoid X receptor and cytochrome P450 family 7 subfamily A member 1. The co-administration of antibiotic cocktail counteracted the effect of Re against NAFLD. Further, the results obtained from the FMT animal study confirmed that Re's liver protective effects were at least partly driven by the regulation of gut microbiota. Re modulated bile salt hydrolase-related microbial genera to alter bile acid synthesis pathways, thereby inhibiting NAFLD progression.

The Role of Gut Microbiota Modification in Nonalcoholic Fatty Liver Disease Treatment Strategies

One of the most common chronic liver diseases is nonalcoholic fatty liver disease (NAFLD), which affects many people around the world. Gut microbiota (GM) dysbiosis seems to be an influential factor in the pathophysiology of NAFLD because changes in GM lead to fundamental changes in host metabolism. Therefore, the study of the effect of dysbiosis on the pathogenicity of NAFLD is important. European clinical guidelines state that the best advice for people with NAFLD is to lose weight and improve their lifestyle, but only 40% of people can achieve this goal. Accordingly, it is necessary to provide new treatment approaches for prevention and treatment. In addition to dietary interventions and lifestyle modifications, GM modification-based therapies are of interest. These therapies include probiotics, synbiotics, fecal microbiota transplantation (FMT), and next-generation probiotics. All of these treatments have had promising results in animal studies, and it can be imagined that acceptable results will be obtained in human studies as well. However, further investigations are required to generalize the outcomes of animal studies to humans.

Akkermansia muciniphila in patients with metabolic dysfunction-associated steatotic liver disease

Akkermansia muciniphila (AM), one of the many microbial species residing in the human gut, has been particularly highlighted for its potential beneficial impacts on host metabolism and gut barrier function. This study evaluated the association between AM concentration and metabolic markers among patients diagnosed with metabolic dysfunction-associated steatotic liver disease (MASL). The study included a cohort of 122 patients with MASLD, monitored between January 1 and June 30, 2024, at the Venus Vascular Center in Oradea, Romania. Enterotype 2 was predominant in the study population, accounting for over 60% of participants. Correlation analysis revealed no statistically significant association between alanine aminotransferase (ALT) or aspartate aminotransferase (AST) levels and AM concentration (ALT: r = -0.147, P = 0.105; AST: r = -0.090, P = 0.325). However, a significant negative linear correlation was determined between gamma-glutamyl transferase (GGT) values and AM concentrations (r = -0.314, P < 0.001) and a moderate, positive correlation between high-density lipoprotein (HDL) values and AM concentration (r = 0.307, P < 0.001). Glycemia showed a weak negative correlation with AM concentration (r = -0.262, P = 0.003). The improvement of liver markers (AST, ALT), even in the absence of correlation with AM concentration, and the negative correlation of GGT, a marker for hepatobiliary diseases and metabolic syndrome, suggest the reduction of oxidative stress in MASLD.

Prebiotics modulate the microbiota-gut-brain axis and ameliorate anxiety and depression-like behavior in HFD-fed mice

Previous research has demonstrated that Prebiotics can influence the composition of the gut microbiota, consequently impacting mood regulation. This study aimed to assess the effects of Prebiotics, specifically Fructooligosaccharides (FOS) and Galactooligosaccharides (GOS) on neuroinflammation, depression, and anxiety-like behavior in a mouse model fed a high-fat diet (HFD). Initially, mice were divided into two groups: a control group on a standard diet (n = 15) and a group on an HFD for 18 weeks (n = 45). By the 13th week, the HFD group was further divided into experimental groups: Control (n = 15), HFD (n = 15), HFD receiving Prebiotics (n = 15), and HFD receiving Fluoxetine (n = 15). From the 13th week onward, the HFD + Prebiotics group received both the high-fat diet and a combination of FOS and GOS, while the HFD + Fluoxetine group received Fluoxetine in their drinking water. In the 18th week, all mice underwent tests to evaluate behavior, including the Tail Suspension Test (TST), Forced Swimming Test (FST), Sucrose Preference Test (SPT), and the Plus Maze Test (PMT), after which they were euthanized. Mice on the HFD exhibited increased body weight, abdominal size, blood glucose, triglyceride levels, cholesterol, insulin, HOMA index, and higher serum IL-1β. These obese mice also displayed an increased number of microglia and astrocytes, activation of the TLR4 pathway, and elevated levels of neuroinflammatory markers like TNF-α, IL-1β, and COX-2. Moreover, obese mice showed increased activation of the IDO pathway and decreased levels of NMDA receptors. Additionally, markers of neurogenesis and synaptic plasticity, such as PSD, SAP 102, CREB-p, and BDNF, were lower. Treatment with FOS and GOS reversed symptoms of depression and anxiety in mice subjected to HD. This improvement in behavior resulted from a reduction in dysbiosis with an increase in acetate-producing bacteria (B. acidifaciens and B. dorei) and intestinal permeability, leading to a decrease in chronic peripheral and central inflammation. Furthermore, the modulation of the gut-brain axis by FOS and GOS promoted elevated acetate and GPR43 levels in the brain and a reduction in the levels of pro-inflammatory cytokines, positively impacting signaling pathways of neuronal proliferation and survival in the hippocampus and prefrontal cortex.

Gut microbiome features and metabolites in non-alcoholic fatty liver disease among community-dwelling middle-aged and older adults

BACKGROUND

The specific microbiota and associated metabolites linked to non-alcoholic fatty liver disease (NAFLD) are still controversial. Thus, we aimed to understand how the core gut microbiota and metabolites impact NAFLD.

METHODS

The data for the discovery cohort were collected from the Guangzhou Nutrition and Health Study (GNHS) follow-up conducted between 2014 and 2018. We collected 272 metadata points from 1546 individuals. The metadata were input into four interpretable machine learning models to identify important gut microbiota associated with NAFLD. These models were subsequently applied to two validation cohorts [the internal validation cohort (n = 377), and the prospective validation cohort (n = 749)] to assess generalizability. We constructed an individual microbiome risk score (MRS) based on the identified gut microbiota and conducted animal faecal microbiome transplantation experiment using faecal samples from individuals with different levels of MRS to determine the relationship between MRS and NAFLD. Additionally, we conducted targeted metabolomic sequencing of faecal samples to analyse potential metabolites.

RESULTS

Among the four machine learning models used, the lightGBM algorithm achieved the best performance. A total of 12 taxa-related features of the microbiota were selected by the lightGBM algorithm and further used to calculate the MRS. Increased MRS was positively associated with the presence of NAFLD, with odds ratio (OR) of 1.86 (1.72, 2.02) per 1-unit increase in MRS. An elevated abundance of the faecal microbiota (f__veillonellaceae) was associated with increased NAFLD risk, whereas f__rikenellaceae, f__barnesiellaceae, and s__adolescentis were associated with a decreased presence of NAFLD. Higher levels of specific gut microbiota-derived metabolites of bile acids (taurocholic acid) might be positively associated with both a higher MRS and NAFLD risk. FMT in mice further confirmed a causal association between a higher MRS and the development of NAFLD.

CONCLUSIONS

We confirmed that an alteration in the composition of the core gut microbiota might be biologically relevant to NAFLD development. Our work demonstrated the role of the microbiota in the development of NAFLD.

Fructooligosaccharides Supplementation: A Good Choice for the Prevention and Treatment of Non-Alcoholic Fatty Liver Disease?

Background and objectives: Carbohydrates such as fructooligosaccharides (FOSs) are associated with improved gastrointestinal health and the prevention of excess body fat. We evaluated the long-term effects of high amounts of FOS on metabolic parameters, non-alcoholic fatty liver disease (NAFLD) and short-chain fatty acids (SCFAs). Methods: Sixty C57BL/6 mice received the following diets for four months: control (C), normolipid rich in fiber (F), normolipid supplemented with FOS (FOS), high fat (HL), high fat with high fiber (HLF) and high fat with FOS (HLFOS). We analyzed the animal weight; body composition; food intake; fasting blood glucose; serum and liver lipid profiles; liver and intestinal histologies; malondialdehyde (MDA), hepatic retinol and α-tocopherol; and SCFAs in the feces. Results: Supplementation with FOS in a high-fat diet promoted less body weight gain and reduced liver and retroperitoneal adipose tissue weights compared to HL and HF. FOS prevented NASH and decreased alanine aminotransferase and serum cholesterol levels in experimental animal models of obesity and metabolic syndrome (MS). There were statistical differences found in the dosages of the three main SCFAs in feces (acetic, isobutyric and isovaleric acids). Conclusions: Long-term supplementation with high doses of FOS was effective in reducing weight, adiposity, NAFLD and serum cholesterol in C57BL mice with obesity and MS induced by a high-fat diet.

Effects of plant natural products on metabolic-associated fatty liver disease and the underlying mechanisms: a narrative review with a focus on the modulation of the gut microbiota

Metabolic-associated fatty liver disease (MAFLD) is a chronic liver disease characterized by the excessive accumulation of fat in hepatocytes. However, due to the complex pathogenesis of MAFLD, there are no officially approved drugs for treatment. Therefore, there is an urgent need to find safe and effective anti-MAFLD drugs. Recently, the relationship between the gut microbiota and MAFLD has been widely recognized, and treating MAFLD by regulating the gut microbiota may be a new therapeutic strategy. Natural products, especially plant natural products, have attracted much attention in the treatment of MAFLD due to their multiple targets and pathways and few side effects. Moreover, the structure and function of the gut microbiota can be influenced by exposure to plant natural products. However, the effects of plant natural products on MAFLD through targeting of the gut microbiota and the underlying mechanisms are poorly understood. Based on the above information and to address the potential therapeutic role of plant natural products in MAFLD, we systematically summarize the effects and mechanisms of action of plant natural products in the prevention and treatment of MAFLD through targeting of the gut microbiota. This narrative review provides feasible ideas for further exploration of safer and more effective natural drugs for the prevention and treatment of MAFLD.

Magnesium isoglycyrrhizinate attenuates nonalcoholic fatty liver disease by strengthening intestinal mucosal barrier

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD)/nonalcoholic steatohepatitis (NASH) has recently risen to the top spot among chronic liver diseases in the world. However, there are no recognized treatments for it. Magnesium isoglycyrrhizate (MgIG) has potential as a NAFLD/NASH therapy.

AIMS

To investigate the efficacy of MgIG in improving NAFLD/NASH and the possible pathways and mechanisms.

METHODS

C57bl/6 mice were fed a high-fat diet (HFD) and 1 % dextran sulfate sodium (DSS) for 12 weeks to establish the NAFLD/NASH model. MgIG was administered by gavage during the last 7 weeks. First, the therapeutic effects of MgIG on hepatic steatosis and fibrosis, liver injury, and inflammation in the NAFLD/NASH mice were evaluated. Second, liver oxidative stress and hepatocyte apoptosis were detected. Finally, the effect of MgIG on intestinal permeability and short-chain fatty acid (SCFA) levels in mice's intestinal contents were examined.

RESULTS

MgIG administration attenuated HFD-induced hepatic steatosis and fibrosis, improved serum biochemical and NAFLD/NASH mice, reduced liver oxidative stress and hepatocyte apoptosis, improved intestinal permeability, and increased fecal SCFA levels in NAFLD/NASH mice.

CONCLUSION

MgIG protects against HFD-induced NAFLD/NASH through multiple pathways as well as mechanisms and holds promise as a potentially effective treatment for NAFLD/NASH.

Roles of Human Gut Microbiota in Liver Cirrhosis Risk: A Two-Sample Mendelian Randomization Study

BACKGROUND

Accumulating evidence suggests that alterations in gut microbiota composition and diversity are associated with liver cirrhosis. But whether gut microbiota promotes or hampers the genesis and development of liver cirrhosis remains vague.

OBJECTIVES

This study aimed to establish a causal relationship between gut microbiota and the development of liver fibrosis and cirrhosis. To achieve this, we employed a 2-sample Mendelian randomization (MR) analysis utilizing genome-wide association study (GWAS) summary statistics. This approach enabled us to assess the potential impact of gut microbiota on liver cirrhosis.

METHODS

The independent genetic instruments of gut microbiota were obtained from the MiBioGen (up to 18,340 participants), which is a large-scale genome-wide genotype and 16S fecal microbiome dataset. Cirrhosis data were derived from the FinnGen biobank analysis, which included 214,403 individuals of European ancestry (811 patients and 213,592 controls). To assess the causal relationship between gut microbiota and cirrhosis, we applied 4 different methods of MR analysis: the inverse-variance weighted method (IVW), the MR-Egger regression, the weighted median analysis (WME), and the weighted mode. Furthermore, sensitivity analyses were conducted to evaluate heterogeneity and horizontal pleiotropy.

RESULTS

Results of MR analyses provided evidence of a causal association between 4 microbiota features and cirrhosis, including 2 family [Lachnosiraceae: odds ratio (OR): 1.82626178; 95% confidence interval (CI): 1.05208209, 3.17012532; P = 0.0323194; Lactobacillaceae : OR: 0.62897502; 95% CI: 0.42513162, 0.93055788; P = 0.02033345] and 2 genus [Butyricicoccus: OR: 0.41432215; 95% CI: 0.22716865, 0.75566257; P = 0.0040564; Lactobacillus: OR: 0.6663767; 95% CI: 0.45679511, 0.97211616; P = 0.03513627].

CONCLUSIONS

Our findings offered compelling evidence of a causal association between gut microbiota and cirrhosis in European population and identified specific bacteria taxa that may regulate the genesis and progression of liver fibrosis and cirrhosis, may offer a new direction for the treatment of cirrhosis.

Altered gut microbiome associated with metabolic-associated fatty liver disease in Chinese children

BACKGROUND & AIM

Limited studies have investigated the association between gut microbiota and metabolic dysfunction-associated fatty liver disease (MAFLD) in children and adolescents. We aimed to identify differences in gut microbiota composition and diversity between children with MAFLD and healthy counterparts.

METHODS

Data were collected from a nested case-control study (October to December, 2021) of the "Huantai Childhood Cardiovascular Health Cohort Study" in Huantai County, Zibo City, China. The study included 52 children aged 5-11 years with new-onset MAFLD and 52 healthy children matched by age and sex. Stool samples were collected and analyzed using 16S rRNA gene sequencing. Shannon index and Chao index were used to assess the α diversity of gut microbiota and Principal coordinates analysis (PCoA) was performed to evaluate β diversity between the two groups. The differences in the relative abundance of gut microbiota between MAFLD group and control group were compared by the Wilcoxon rank-sum test after false discovery rate (FDR) correction. Additionally, the gut-microbial metabolic pathways were identified using the phylogenetic investigation of communities by reconstruction of unobserved states (PICRUSt).

RESULTS

We found that children with MAFLD had significant different gut microbiota composition and reduced α diversity compared with the control group. PCoA showed that the two groups can be significantly distinguished based on the unweighted unifrac distance algorithm. Gut microbiota at the phylum level such as Verrucomicrobia and Desulfobacterial, genus level such as Blautia, Lachnospiraceae_NK4A136_group, Coprococcus, Erysipelotrichaceae_UCG-003, UCG-002 and Akkermansia, and species level such as Bifidobacterium_longum abundances were significantly decreased in children with MAFLD compared with that in children without MAFLD. Notably, the abundance of these bacteria were found to be associated with HDL-C, SBP, DBP, WC, BMI, etc. In addition, our analysis of gut-microbial metabolic pathways identified differences in carbohydrate transport and metabolism, as well as amino acid transport and metabolism between the two groups.

CONCLUSION

Significant differences in gut microbiota composition are observed between children with and without MAFLD, which indicate that gut microbiota may be a potential contributor to the development of MAFLD in childhood.

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.

Chronic jet lag alters gut microbiome and mycobiome and promotes the progression of MAFLD in HFHFD-fed mice

Metabolic dysfunction-associated fatty liver disease (MAFLD) is the most common chronic liver disease worldwide. Circadian disruptors, such as chronic jet lag (CJ), may be new risk factors for MAFLD development. However, the roles of CJ on MAFLD are insufficiently understood, with mechanisms remaining elusive. Studies suggest a link between gut microbiome dysbiosis and MAFLD, but most of the studies are mainly focused on gut bacteria, ignoring other components of gut microbes, such as gut fungi (mycobiome), and few studies have addressed the rhythm of the gut fungi. This study explored the effects of CJ on MAFLD and its related microbiotic and mycobiotic mechanisms in mice fed a high fat and high fructose diet (HFHFD). Forty-eight C57BL6J male mice were divided into four groups: mice on a normal diet exposed to a normal circadian cycle (ND-NC), mice on a normal diet subjected to CJ (ND-CJ), mice on a HFHFD exposed to a normal circadian cycle (HFHFD-NC), and mice on a HFHFD subjected to CJ (HFHFD-CJ). After 16 weeks, the composition and rhythm of microbiota and mycobiome in colon contents were compared among groups. The results showed that CJ exacerbated hepatic steatohepatitis in the HFHFD-fed mice. Compared with HFHFD-NC mice, HFHFD-CJ mice had increases in Aspergillus, Blumeria and lower abundances of Akkermansia, Lactococcus, Prevotella, Clostridium, Bifidobacterium, Wickerhamomyces, and Saccharomycopsis genera. The fungi-bacterial interaction network became more complex after HFHFD and/or CJ interventions. The study revealed that CJ altered the composition and structure of the gut bacteria and fungi, disrupted the rhythmic oscillation of the gut microbiota and mycobiome, affected interactions among the gut microbiome, and promoted the progression of MAFLD in HFHFD mice.

In Vitro Screening for Probiotic Properties of Lactobacillus and Bifidobacterium Strains in Assays Relevant for Non-Alcoholic Fatty Liver Disease Prevention

Non-alcoholic fatty liver disease (NAFLD) is a multifactorial metabolic disorder that poses health challenges worldwide and is expected to continue to rise dramatically. NAFLD is associated with metabolic syndrome, type 2 diabetes mellitus, and impaired gut health. Increased gut permeability, caused by disturbance of tight junction proteins, allows passage of damaging microbial components that, upon reaching the liver, have been proposed to trigger the release of inflammatory cytokines and generate cellular stress. A growing body of research has suggested the utilization of targeted probiotic supplements as a preventive therapy to improve gut barrier function and tight junctions. Furthermore, specific microbial interactions and metabolites induce the secretion of hormones such as GLP-1, resulting in beneficial effects on liver health. To increase the likelihood of finding beneficial probiotic strains, we set up a novel screening platform consisting of multiple in vitro and ex vivo assays for the screening of 42 bacterial strains. Analysis of transepithelial electrical resistance response via co-incubation of the 42 bacterial strains with human colonic cells (Caco-2) revealed improved barrier integrity. Then, strain-individual metabolome profiling was performed revealing species-specific clusters. GLP-1 secretion assay with intestinal secretin tumor cell line (STC-1) found at least seven of the strains tested capable of enhancing GLP-1 secretion in vitro. Gene expression profiling in human biopsy-derived intestinal organoids was performed using next generation sequencing transcriptomics post bacterial co-incubation. Here, different degrees of immunomodulation by the increase in certain cytokine and chemokine transcripts were found. Treatment of mouse primary hepatocytes with selected highly produced bacterial metabolites revealed that indole metabolites robustly inhibited de novo lipogenesis. Collectively, through our comprehensive bacterial screening pipeline, not previously ascribed strains from both Lactobacillus and Bifidobacterium genera were proposed as potential probiotics based on their ability to increase epithelial barrier integrity and immunity, promote GLP-1 secretion, and produce metabolites relevant to liver health.

Nobiletin Ameliorates Nonalcoholic Fatty Liver Disease by Regulating Gut Microbiota and Myristoleic Acid Metabolism

Disturbance of the gut microbiota plays a critical role in the development of nonalcoholic fatty liver disease (NAFLD). Increasing evidence supports that natural products may serve as prebiotics to regulate the gut microbiota in the treatment of NAFLD. In the present study, the effect of nobiletin, a naturally occurring polymethoxyflavone, on NAFLD was evaluated, and metabolomics, 16S rRNA gene sequencing, and transcriptomics analysis were performed to determine the underlying mechanism of nobiletin, and the key bacteria and metabolites screened were confirmed by in vivo experiment. Nobiletin treatment could significantly reduce lipid accumulation in high-fat/high-sucrose diet-fed mice. 16S rRNA analysis demonstrated that nobiletin could reverse the dysbiosis of gut microbiota in NAFLD mice and nobiletin could regulate myristoleic acid metabolism, as revealed by untargeted metabolomics analysis. Treatment with the bacteria Allobaculum stercoricanis, Lactobacillus casei, or the metabolite myristoleic acid displayed a protective effect on liver lipid accumulation under metabolic stress. These results indicated that nobiletin might target gut microbiota and myristoleic acid metabolism to ameliorate NAFLD.

Role of Akkermansia in Human Diseases: From Causation to Therapeutic Properties

The gut microbiota plays a critical role in the modulation of host metabolism and immune response, and its impairment has been implicated in many gastrointestinal and extraintestinal diseases. Current evidence shows the well-documented role of A. muciniphila in maintaining the integrity of the intestinal barrier, modulating the host immune response, and improving several metabolic pathways, making it a key element in the pathogenesis of several human diseases. In this scenario, A. muciniphila is the most promising next-generation probiotic and one of the first microbial species suitable for specific clinical use when compared with traditional probiotics. Further studies are needed to provide more accurate insight into its mechanisms of action and to better elucidate its properties in several major areas, paving the way for a more integrated and personalized therapeutic approach that finally makes the most of our knowledge of the gut microbiota.

Two-week repair alleviates hexavalent chromium-induced hepatotoxicity, hepatic metabolic and gut microbial changes: A dynamic inhalation exposure model in male mice

Hexavalent chromium [Cr(VI)] has been identified as a "Group I human carcinogen" with multisystem and multiorgan toxicity. A dynamic inhalation exposure model in male mice, coupled with the hepatic metabolome and gut microbiome, was used to explore hepatotoxicity, and hepatic metabolic and gut microbial changes under the exposure scenarios in the workspace and general environment. The present study set up an exposure group (EXP) that inhaled 150 μg Cr/m³ for 13 weeks, a control group (CONT) that inhaled purified air, as well as a two-week repair group (REXP) after 13 weeks of exposure and the corresponding control group (RCONT). Cr(VI) induced elevation of hepatic Cr accumulation, the ratio of ALT and AST, and folate in serum. Inflammatory infiltration in the liver and abnormal mitochondria in hepatocytes were also induced by Cr(VI). Glutathione, ascorbate, folic acid, pantetheine, 3'-dephospho-CoA and citraconic acid were the key metabolites affected by Cr(VI) that were associated with significant pathways such as pantothenate and CoA biosynthesis, hypoxia-inducible factor-1 signaling pathway, antifolate resistance, alpha-linolenic acid metabolism and one carbon pool by folate. g_Allobaculum was identified as a sensitive biomarker of Cr(VI) exposure because g_Allobaculum decreased under Cr(VI) exposure but increased after repair. The gut microbiota might be involved in the compensation of hepatotoxicity by increasing short-chain fatty acid-producing bacteria, including g_Lachnospiraceae_NK4A136_group, g_Blautia, and f_Muribaculaceae. After the two-week repair, the differential metabolites between the exposed and control groups were reduced from 73 to 29, and the KEGG enrichment pathways and differential microbiota also decreased. The mechanism for repair was associated with reversion of lipid peroxidation and energy metabolism, as well as activation of protective metabolic pathways, such as the AMPK signaling pathway, longevity regulating pathway, and oxidative phosphorylation. These findings might have theoretical and practical implications for better health risk assessment and management.

Targeting keystone species helps restore the dysbiosis of butyrate-producing bacteria in nonalcoholic fatty liver disease

The dysbiosis of the gut microbiome is one of the pathogenic factors of nonalcoholic fatty liver disease (NAFLD) and also affects the treatment and intervention of NAFLD. Among gut microbiomes, keystone species that regulate the integrity and stability of an ecological community have become the potential intervention targets for NAFLD. Here, we collected stool samples from 22 patients with nonalcoholic steatohepatitis (NASH), 25 obese patients, and 16 healthy individuals from New York for 16S rRNA gene sequencing. An algorithm was implemented to identify keystone species based on causal inference theories and dynamic intervention simulation. External validation was performed in an independent cohort from California. Eight keystone species in the gut of NAFLD, represented by Porphyromonas loveana, Alistipes indistinctus, and Dialister pneumosintes, were identified, which could efficiently restore the microbial composition of the NAFLD toward a normal gut microbiome with 92.3% recovery. These keystone species regulate intestinal amino acid metabolism and acid-base environment to promote the growth of the butyrate-producing Lachnospiraceae and Ruminococcaceae species that are significantly reduced in NAFLD patients. Our findings demonstrate the importance of keystone species in restoring the microbial composition toward a normal gut microbiome, suggesting a novel potential microbial treatment for NAFLD.

The effects of fasting diets on nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is the most common liver disease in the world. There is no confirmed treatment for NAFLD as yet. Recently, fasting regimens and their relationship to NAFLD have drawn a great deal of attention in the literature. We review the current evidence that supports fasting diets as an adjunctive therapeutic strategy for patients with NAFLD and address potential action mechanisms. We reason that the fasting diets might be a promising approach for modulating hepatic steatosis, fibroblast growth factors 19 and 21 signaling, lipophagy, and the metabolic profile.

Structural characteristics of polysaccharide from Zingiber striolatum and its effects on gut microbiota composition in obese mice

To investigate a polysaccharide from Zingiber striolatum favorably modulates gut microbiota in mice fed a high-fat diet. Z. striolatum was utilized to extract the crude polysaccharide CZSP, which was subsequently refined using DEAE-52 cellulose and Sephadex G-150 to yield the novel polysaccharide Zingiber strioatum pure polysaccharide-1 (ZSPP-1). ZSPP-1 was an acidic heteroglycan made up of galactose, mannose, glucose, xylose, arabinose, glucuronic acid, and galacturonic acid with an average molecular weight of 1.57 × 106 Da. The structure of ZSPP-1 was investigated by FT-IR, methylation and NMR analysis, and the results denoted that the linkage structure types include T-Manp-linked, β-Xylp-(1,2)-linked, β-Galp-(1,4)-linked, α-GlcpA-(1,6)-linked, β-Arap-(1,4)-linked, α-Glcp-(1,3,4,6)-linked, α-Glcp-(1,2)-linked, and β-T-Xylp-linked, in which β-Galp-(1,4)-linked and α-GalpA-(1,4)-linked might be the main linkage. The results of the intervention experiments showed that ZSPP-1 changed the intestinal flora structure of the Firmicutes and Bacteroidetes in obese mice, and promoted the growth of beneficial bacteria such as Akkermansia, Lactobacillus, and Bacteroides in the intestine. It also restored the imbalanced flora structure due to high-fat diet to normal. It also restored the imbalanced flora structure due to high-fat diet to normal. Z. striolatum polysaccharides presented a considerable advantage in alleviating high-fat diet induced obesity, which indicates that it can be further exploited as a natural functional food resource.

Gynostemma pentaphyllum polysaccharides ameliorate non-alcoholic steatohepatitis in mice associated with gut microbiota and the TLR2/NLRP3 pathway

Recent studies have revealed the pivotal role of gut microbiota in the progress of liver diseases including non-alcoholic steatohepatitis (NASH). Many natural herbs, such as Gynostemma pentaphyllum (GP), have been extensively applied in the prevention of NASH, while the bioactive components and underlying mechanism remain unclear. The aim of this study was to investigate whether the polysaccharides of GP (GPP) have a protective effect on NASH and to explore the potential mechanism underlying these effects. C57BL/6 male mice were fed with a methionine-choline-deficient (MCD) diet for 4 weeks to induce NASH and administered daily oral gavage of sodium carboxymethylcellulose (CMC-Na), low dose of GPP (LGPP), high dose of GPP (HGPP), and polyene phosphatidylcholine capsules (PPC), compared with the methionine-choline-sufficient (MCS) group. Our results showed that the symptoms of hepatic steatosis, hepatocyte ballooning, liver fibrosis, and oxidative stress could be partially recovered through the intervention of GPP with a dose-dependent effect. Furthermore, gut microbiome sequencing revealed that HGPP altered the composition of gut microbiota, mainly characterized by the enrichment of genera including Akkermansia, Lactobacillus, and A2. Moreover, hepatic transcriptome analysis indicated that the anti-inflammatory effect of HGPP might be associated with toll-like receptor (TLR) and nod-like receptor (NLR) signaling pathways. HGPP could inhibit the expression of TLR2 and downregulate the expression of the NLRP3 inflammasome, as well as the pro-inflammatory cytokine tumor necrosis factor (TNF)-α and interleukin (IL)-1β. In summary, GPP could ameliorate NASH possibly mediated via the modulation of gut microbiota and the TLR2/NLRP3 signaling pathway, indicating that GPP could be tested as a prebiotic agent in the prevention of NASH.

The Changes in Microbiotic Composition of Different Intestinal Tracts and the Effects of Supplemented Lactobacillus During the Formation of Goose Fatty Liver

Intestinal bacteria play an important role in the formation of fatty liver in animals by participating in the digestion and degradation of nutrients, producing various metabolites, and altering the barrier effect of the intestine. However, changes in the gut microbiota during the formation of goose fatty liver are unclear. In this study, 80 healthy Landes geese with similar body weights at 70 days of age were randomly divided into two groups: the control group (n = 48; fed ad libitum) and the overfeeding group (n = 32; overfed). The intestinal contents were collected at 0, 12, and 24 days of overfeeding. The 16S rRNA and metagenomic sequencing analyses showed that the dominant phyla were Firmicutes, Proteobacteria, Bacteroidetes, and Actinobacteria. At the genus level, Phyllobacterium, Bacteroides, Helicobacter, Lactobacillus, Enterococcus, and Romboutsia were the dominant genera in the goose intestine, and most of them were probiotics. In the control group, the relative abundance of Firmicutes in the jejunum and ileum gradually decreased with time, while that of Proteobacteria increased, whereas in the overfeeding group, the relative abundance of Firmicutes in the jejunum and ileum decreased and then increased with time, while that of Proteobacteria showed an opposite trend. In addition, supplementing Lactobacillus to the diet reduced body weight and fatty liver weight in overfed geese, but increased the weight of abdominal fat, suggesting that Lactobacillus supplementation might affect the transport of nascent fat from the liver to abdominal fat. In conclusion, the species of intestinal-dominant bacteria in the geese are relatively stable, but their relative abundance and function are affected by a number of factors. Overfeeding promotes the metabolism of nutrients in the jejunum and ileum and increases bacterial adaptability to environmental changes by enhancing their ability to process environmental and genetic information more efficiently. These findings suggest that the effect of overfeeding on the composition of intestinal microbiota may indirectly influence the formation of goose fatty liver through the gut/liver axis.

Gut Microbiota Structure and Metabolites, Before and After Treatment in Early Rheumatoid Arthritis Patients: A Pilot Study

Rheumatoid Arthritis (RA) is a chronic systemic autoimmune disease. Modifications of gut microbiota seem to be associated with the disease, but the impact of gut microbiota on therapies’ outcome remains unclear. A role of T cells in RA pathogenesis has been addressed, particularly on the Th17/Treg cells balance. Our study aimed to evaluate in early RA (ERA) patients compared to a control group, fecal gut microbiota composition, short-chain fatty acids concentrations, and the levels of circulating Th17/Treg and their own cytokines, before and after 3 months of standard treatment (Methotrexate (MTX) plus glucocorticoids). Fecal microbiota characterization was carried out on 19 ERA patients and 20 controls matched for sex and age. Significant decreased biodiversity levels, and a partition on the base of the microbiota composition, between the ERA patients at baseline compared to controls, were observed. The co-occurrent analysis of interactions revealed a characteristic clustered structure of the microbial network in controls that is lost in ERA patients where an altered connection between microbes and clinical parameters/metabolites has been reported. Microbial markers such as Acetanaerobacterium elongatum, Cristiansella massiliensis, and Gracilibacter thermotolerans resulted significantly enriched in control group while the species Blautia gnavus emerged to be more abundant in ERA patients. Our results showed an alteration in Th17/Treg balance with higher Th17 levels and lower Treg levels in ERA group respect to control at baseline, those data improved after therapy. Treatment administration and the achievement of a low disease activity/remission appear to exert a positive pressure on the structure of intestinal microbiota with the consequent restoration of biodiversity, of the structure of microbial network, and of the abundance of taxa that became closer to those presented by the subject without the disease. We also found an association between Blautia gnavus and ERA patients characterized by a significant reduction of propionic acid level. Furthermore significant differences highlighted at baseline among controls and ERA patients are no more evident after treatment. These data corroborate the role played by gut microbiota in the disease and suggest that therapy aimed to restore gut microbiota would improve treatment outcome.

Endothelial‐immune crosstalk contributes to vasculopathy in nonalcoholic fatty liver disease

The top cause of mortality in patients with nonalcoholic fatty liver disease (NAFLD) is cardiovascular complications. However, mechanisms of NAFLD‐associated vasculopathy remain understudied. Here, we show that blood outgrowth endothelial cells (BOECs) from NAFLD subjects exhibit global transcriptional upregulation of chemokines and human leukocyte antigens. In mouse models of diet‐induced NAFLD, we confirm heightened endothelial expressions of CXCL12 in the aortas and the liver vasculatures, and increased retention of infiltrated leukocytes within the vessel walls. To elucidate endothelial‐immune crosstalk, we performed immunoprofiling by single‐cell analysis, uncovering T cell intensification in NAFLD patients. Functionally, treatment with a CXCL12‐neutralizing antibody is effective at moderating the enhanced chemotactic effect of NAFLD BOECs in recruiting CD8⁺ T lymphocytes. Interference with the CXCL12‐CXCR4 axis using a CXCR4 antagonist also averts the impact of immune cell transendothelial migration and restores endothelial barrier integrity. Clinically, we detect threefold more circulating damaged endothelial cells in NAFLD patients than in healthy controls. Our work provides insight into the modulation of interactions with effector immune cells to mitigate endothelial injury in NAFLD.

Early prediction of incident liver disease using conventional risk factors and gut-microbiome-augmented gradient boosting

The gut microbiome has shown promise as a predictive biomarker for various diseases. However, the potential of gut microbiota for prospective risk prediction of liver disease has not been assessed. Here, we utilized shallow shotgun metagenomic sequencing of a large population-based cohort (N > 7,000) with ∼15 years of follow-up in combination with machine learning to investigate the predictive capacity of gut microbial predictors individually and in conjunction with conventional risk factors for incident liver disease. Separately, conventional and microbial factors showed comparable predictive capacity. However, microbiome augmentation of conventional risk factors using machine learning significantly improved the performance. Similarly, disease-free survival analysis showed significantly improved stratification using microbiome-augmented models. Investigation of predictive microbial signatures revealed previously unknown taxa for liver disease, as well as those previously associated with hepatic function and disease. This study supports the potential clinical validity of gut metagenomic sequencing to complement conventional risk factors for prediction of liver diseases.

Development, Characterization, and Investigation of In Vivo Targeted Delivery Efficacy of Luteolin-Loaded, Eudragit S100-Coated mPEG-PLGA Nanoparticles

Luteolin (Lu) is a kind of flavonoid that has been proved to treat non-alcoholic fatty liver disease by alleviating intestinal microbiota disorder. In this study, luteolin was coated with methoxy poly(ethylene glycol)-poly(dl-lactide-co-glycolic acid) (mPEG-PLGA) using an emulsion solvent evaporation method, and the optimum preparation process was determined by a single-factor experiment combined with response surface methodology (RSM). Methacrylic acid-methyl methacrylate (1:2) copolymer (Eudragit S100) was then used to coat the surface of Lu/mPEG-PLGA nanoparticles. The physical parameters of Eudragit S100-coated Lu/mPEG-PLGA nanoparticles (Lu-NPs), such as appearance, particle size, potential, particle size distribution and drug release, and stability in vitro, were evaluated. In addition, its cytotoxicity in vitro, pharmacokinetics, tissue distribution, and toxicity in vivo were also studied. The results showed that the prepared Lu-NPs had uniform particle size distribution, high encapsulation efficiency, and good stability. Normal colonic epithelial cells showed good tolerance to Lu-NPs. After oral administration, the blood concentration of luteolin peaked at 8 h, and the main tissue distribution was within the colon, confirming its colon-targeted profile. Safety assessments also indicated that no significant changes were observed in main organs after administration of Lu-NPs. The use of Eudragit S100-coated Lu/mPEG-PLGA nanoparticles is a new strategy for colon-targeted delivery of luteolin that encourages luteolin to fulfill its role in the colon.

Tremella fuciformis Crude Polysaccharides Attenuates Steatosis and Suppresses Inflammation in Diet-Induced NAFLD Mice

Nonalcoholic fatty liver disease (NAFLD) is a chronic liver disorder characterized by an enhanced accumulation of lipids, which affects around 40% of the world's population. The T. fuciformis fungus possesses immunomodulatory activity and other beneficial properties that may alleviate steatosis through a different mechanism. The present study was designed to evaluate the effect T. fuciformis crude polysaccharides (TFCP) on inflammatory and lipid metabolism gene expression, oxidative stress, and lipid profile. Mice were divided into groups receiving (a) a normal chow diet (NCD), (b) a methionine-choline-deficient (MCD) diet, and (c) a MCD diet with TFCP. Liver histopathology was performed, and the hepatic gene expression levels were estimated using qRT-PCR. The lipid profiles, ALT, AST, and efficient oxidative enzymes were analyzed using ELISA. The TFCP administration in the MCD-fed mice suppressed hepatic lipid accumulation, lipid metabolism-associated genes (HMGCR, FABP, SREBP, ACC, and FAS), and inflammation-associated genes (IL-1β, TLR4, TNF-α, and IL-6) whilst enhancing the expression of HNF4α genes. TFCP mitigated against oxidative stress and normalized healthy lipid profiles. These results highlighted that TFCP prevents NAFLD through the inhibition of oxidative stress and inflammation, suggesting TFCP would potentially be an effective therapeutic agent against NAFLD progression.

Pivotal Dominant Bacteria Ratio and Metabolites Related to Healthy Body Index Revealed by Intestinal Microbiome and Metabolomics

Various body indexes, especially body fat percentage (BFP), are widely used as effective indicators to measure our health. BFP is used in medicine to assess obesity, which is a body fat mass disorder accompanied with changes of the gut microbiota. However, the relationship between BFP and the gut microbiota has not been studied so far. To address this problem, we examined how gut microbiota and metabolome associated with body indices in healthy people. Microbial and metabolomics data based on 16S rDNA sequencing and LC-MS were obtained from stool samples of 20 healthy adults. Bioinformatics analysis was performed to explore the correlations between the body indices and gut microbial characteristics. Significantly different microbes were further validated via qPCR. Differential characteristics were filtered by building machine learning models to predict body status. Our data showed that abundance of Prevotella and the Prevotella/Bacteroides (P/B) ratio in the gut were markedly higher in high-BFP individuals than in low-BFP individuals. Microbial and metabolomics data consistently suggested significant differences in fatty acid metabolism in stool samples from the two groups. The P/B ratio and fatty acids are discriminative for people with different index levels by cross validation tests with machine learning models. These results suggest using Prevotella and fecal fatty acids as predictors may offer an alternative method for evaluating health status or weight loss.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s12088-021-00989-5.

Oxidative Stress in Non-Alcoholic Fatty Liver Disease

Non-alcoholic fatty liver disease (NAFLD) is a challenging disease caused by multiple factors, which may partly explain why it still remains an orphan of adequate therapies. This review highlights the interaction between oxidative stress (OS) and disturbed lipid metabolism. Several reactive oxygen species generators, including those produced in the gastrointestinal tract, contribute to the lipotoxic hepatic (and extrahepatic) damage by fatty acids and a great variety of their biologically active metabolites in a “multiple parallel-hit model”. This leads to inflammation and fibrogenesis and contributes to NAFLD progression. The alterations of the oxidant/antioxidant balance affect also metabolism-related organelles, leading to lipid peroxidation, mitochondrial dysfunction, and endoplasmic reticulum stress. This OS-induced damage is at least partially counteracted by the physiological antioxidant response. Therefore, modulation of this defense system emerges as an interesting target to prevent NAFLD development and progression. For instance, probiotics, prebiotics, diet, and fecal microbiota transplantation represent new therapeutic approaches targeting the gut microbiota dysbiosis. The OS and its counter-regulation are under the influence of individual genetic and epigenetic factors as well. In the near future, precision medicine taking into consideration genetic or environmental epigenetic risk factors, coupled with new OS biomarkers, will likely assist in noninvasive diagnosis and monitoring of NAFLD progression and in further personalizing treatments.

Association of small intestinal bacterial overgrowth with nonalcoholic fatty liver disease in children: A meta-analysis

It has been suggested that small intestinal bacterial overgrowth (SIBO) could cause nonalcoholic fatty liver disease (NAFLD), but this association was not examined in children by meta-analysis. This meta-analysis aimed to determine the association between SIBO and NAFLD in children. The electronic databases PubMed, Embase, and Cochrane Library were searched for studies published before April 22, 2021. The outcome was the association between SIBO and NAFLD. Three studies and 205 children were included. All three studies reported the association between SIBO and NAFLD. Children with SIBO were more likely to have NAFLD (odds ratio = 5.27, 95% confidence interval (CI): 1.66-16.68, P<0.001; I2 = 63.5%, Pheterogeneity = 0.065). When directly pooling the reported relative risks (RR) from two studies, children with NAFLD had an over 2-fold increased relative risk of developing SIBO (RR = 2.17, 05%CI: 1.66-2.82, P<0.001; I2 = 0.0%, Pheterogeneity = 0.837). This meta-analysis reports a possible association between SIBO and NAFLD in children.

Broccoli Florets Supplementation Improves Insulin Sensitivity and Alters Gut Microbiome Population-A Steatosis Mice Model Induced by High-Fat Diet

Nonalcoholic fatty liver disease (NAFLD) is linked to obesity, type 2 diabetes, hyperlipidemia, and gut dysbiosis. Gut microbiota profoundly affects the host energy homeostasis, which, in turn, is affected by a high-fat diet (HFD) through the liver-gut axis, among others. Broccoli contains beneficial bioactive compounds and may protect against several diseases. This study aimed to determine the effects of broccoli supplementation to an HFD on metabolic parameters and gut microbiome in mice. Male (7–8 weeks old) C57BL/J6 mice were divided into four groups: normal diet (ND), high-fat diet (HFD), high-fat diet+10% broccoli florets (HFD + F), and high-fat diet + 10% broccoli stalks (HFD + S). Liver histology and serum biochemical factors were evaluated. Alterations in protein and gene expression of the key players in lipid and carbohydrate metabolism as well as in gut microbiota alterations were also investigated. Broccoli florets addition to the HFD significantly reduced serum insulin levels, HOMA-IR index, and upregulated adiponectin receptor expression. Conversely, no significant difference was found in the group supplemented with broccoli stalks. Both broccoli stalks and florets did not affect fat accumulation, carbohydrate, or lipid metabolism-related parameters. Modifications in diversity and in microbial structure of proteobacteria strains, Akermansia muciniphila and Mucispirillum schaedleri were observed in the broccoli-supplemented HFD-fed mice. The present study suggests that dietary broccoli alters parameters related to insulin sensitivity and modulates the intestinal environment. More studies are needed to confirm the results of this study and to investigate the mechanisms underlying these beneficial effects.

Probiotics and Prebiotics as a Strategy for Non-Alcoholic Fatty Liver Disease, a Narrative Review

Non-alcoholic fatty liver disease (NAFLD) is a chronic non-communicable disease, with a prevalence of 25% worldwide. This pathology is a multifactorial illness, and is associated with different risks factors, including hypertension, hyperglycemia, dyslipidemia, and obesity. Beside these predisposing features, NAFLD has been related to changes in the microbiota, which favor the disease progression. In this context, the modulation of the gut microbiota has emerged as a new therapeutic target for the prophylaxis and treatment of NAFLD. This review describes the changes in the gut microbiota associated with NAFLD and the effect of probiotics, prebiotics, and synbiotics on the gut microbiota, liver damage, anthropometric parameters, blood lipids, inflammation markers and insulin resistance in these patients.

Gut Microbiota in Liver Disease: What Do We Know and What Do We Not Know?

The gut and the liver have a bidirectional communication via the biliary system and the portal vein. The intestinal microbiota and microbial products play an important role for modulating liver diseases such as alcohol-associated liver disease, non-alcoholic fatty liver disease and steatohepatitis, and cholestatic liver diseases. Here, we review the role of the gut microbiota and its products for the pathogenesis and therapy of chronic liver diseases.

Self-Balance of Intestinal Flora in Spouses of Patients With Rheumatoid Arthritis

We sought to characterize and assess differences in compositions of intestinal flora between patients with rheumatoid arthritis (RA) and their respective spouses. Eighty volunteers were recruited, including 30 pairs of RA patients and their spouses, and 20 healthy individuals. Fresh stool samples were collected, processed, and 16S rRNA-sequencing was performed. Data were analyzed using an operational taxonomic units-based method, and community structure assessments were performed. Community composition analysis indicated that there were similar intestinal microbiota structures in RA and in their respective spouses. Gut microbiota in spouses of RA were different from those of the healthy controls group, but these differences were not significant. We found that Blautia spp. and Streptococcus spp. were two most associated species in RA and these taxa were significantly higher in comparison to healthy controls. In contrast, our findings suggested that Roseburia spp. and Lachnoclostridium spp. were significantly lower in the RA in comparison to healthy controls. In conclusion, RA patients shared similar gut microbiota pattern with their spouses which were different from healthy individuals. The findings suggest that disturbance of the balance of gut microbiota may play an important role in the dynamics of pathogenesis of RA.

Toll-Like Receptors Recognize Intestinal Microbes in Liver Cirrhosis

Liver cirrhosis is one major cause of mortality in the clinic, and treatment of this disease is an arduous task. The scenario will be even getting worse with increasing alcohol consumption and obesity in the current lifestyle. To date, we have no medicines to cure cirrhosis. Although many etiologies are associated with cirrhosis, abnormal intestinal microbe flora (termed dysbiosis) is a common feature in cirrhosis regardless of the causes. Toll-like receptors (TLRs), one evolutional conserved family of pattern recognition receptors in the innate immune systems, play a central role in maintaining the homeostasis of intestinal microbiota and inducing immune responses by recognizing both commensal and pathogenic microbes. Remarkably, recent studies found that correction of intestinal flora imbalance could change the progress of liver cirrhosis. Therefore, correction of intestinal dysbiosis and targeting TLRs can provide novel and promising strategies in the treatment of liver cirrhosis. Here we summarize the recent advances in the related topics. Investigating the relationship among innate immunity TLRs, intestinal flora disorders, and liver cirrhosis and exploring the underlying regulatory mechanisms will assuredly have a bright future for both basic and clinical research.

Transcriptional Regulation of Metabolic Pathways via Lipid-Sensing Nuclear Receptors PPARs, FXR, and LXR in NASH

Nonalcoholic fatty liver disease comprises a wide spectrum of liver injuries from simple steatosis to steatohepatitis and cirrhosis. Nonalcoholic steatohepatitis (NASH) is defined when liver steatosis is associated with inflammation, hepatocyte damage, and fibrosis. A genetic predisposition and environmental insults (ie, dietary habits, obesity) are putatively responsible for NASH progression. Here, we present the impact of the lipid-sensing nuclear receptors in the pathogenesis and treatment of NASH. In detail, we discuss the pros and cons of the putative transcriptional action of the fatty acid sensors (peroxisome proliferator-activated receptors), the bile acid sensor (farnesoid X receptor), and the oxysterol sensor (liver X receptors) in the pathogenesis and bona fide treatment of NASH.

Gut Akkermansia muciniphila ameliorates metabolic dysfunction-associated fatty liver disease by regulating the metabolism of L-aspartate via gut-liver axis

The gut bacterium Akkermansia muciniphila has been increasingly recognized for its therapeutic potential in treating metabolic disorders, including obesity, diabetes, and metabolicdysfunction-associated fatty liver disease (MAFLD). However, its underlying mechanism involved in its well-known metabolic actions needs further evaluation. The present study explored the therapeutic effect and mechanism of A. muciniphila in intervening MAFLD by using a high-fat and high-cholesterol (HFC) diet induced obese mice model. Mice treated with A. muciniphila efficiently reversed MAFLD in the liver, such as hepatic steatosis, inflammatory, and liver injury. These therapeutic effects persisted after long-term drug withdrawal and were slightly weakened in the antibiotics-treated obese mice. A. muciniphila treatment efficiently increased mitochondrial oxidation and bile acid metabolism in the gut-liver axis, ameliorated oxidative stress-induced cell apoptosis in gut, leading to the reshaping of the gut microbiota composition. These metabolic improvements occurred with increased L-aspartate levels in the liver that transported from the gut. The administration of L-aspartate in vitro or in mice displayed the similar beneficial metabolic effects mentioned above and efficiently ameliorated MAFLD. Together, these data indicate that the anti-MAFLD activity of A. muciniphila correlated with lipid oxidation and improved gut-liver interactions through regulating the metabolism of L-aspartate. A. muciniphila could be a potential agent for clinical intervention in MAFLD.

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.

The deficit in folate and vitamin B12 triggers liver macrovesicular steatosis and inflammation in rats with dextran sodium sulfate-induced colitis

The risks of nonalcoholic steatohepatitis (NASH) and deficiency in vitamin B12 and folate (methyl donor deficiency, MDD) are increased in inflammatory bowel disease (IBD). We investigated the influence of MDD on NASH in rats with DSS-induced colitis. Two-month-old male Wistar rats were subjected to MDD diet and/or ingestion of DSS and compared to control animals. We studied steatosis, inflammation, fibrosis, plasma levels of metabolic markers, cytokines and lipopolysaccharide, and inflammatory pathways in liver. MDD triggered a severe macrovesicular steatosis with inflammation in DSS animals that was not observed in animals subjected to DSS or MDD only. The macrovesicular steatosis was closely correlated to folate, vitamin B12, homocysteine plasma level and liver S-adenosyl methionine/S-adenosyl homocysteine (SAM/SAH) ratio. Liver inflammation was evidenced by activation of nuclear factor kappa B (NFκB) pathway and nuclear translocation of NFκB phospho-p65. MDD worsened the increase of interleukin 1-beta (IL-1β) and abolished the increase of IL10 produced by DSS colitis. It increased monocyte chemoattractant protein 1 (MCP-1). MDD triggers liver macrovesicular steatosis and inflammation through imbalanced expression of IL-1β vs. IL10 and increase of MCP-1 in DSS colitis. Our results suggest evaluating whether IBD patients with MDD and increase of MCP-1 are at higher risk of NASH.

Metabolic inflammation as an instigator of fibrosis during non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) is characterized by excessive storage of fatty acids in the form of triglycerides in hepatocytes. It is most prevalent in western countries and includes a wide range of clinical and histopathological findings, namely from simple steatosis to steatohepatitis and fibrosis, which may lead to cirrhosis and hepatocellular cancer. The key event for the transition from steatosis to fibrosis is the activation of quiescent hepatic stellate cells (qHSC) and their differentiation to myofibroblasts. Pattern recognition receptors (PRRs), expressed by a plethora of immune cells, serve as essential components of the innate immune system whose function is to stimulate phagocytosis and mediate inflammation upon binding to them of various molecules released from damaged, apoptotic and necrotic cells. The activation of PRRs on hepatocytes, Kupffer cells, the resident macrophages of the liver, and other immune cells results in the production of proinflammatory cytokines and chemokines, as well as profibrotic factors in the liver microenvironment leading to qHSC activation and subsequent fibrogenesis. Thus, elucidation of the inflammatory pathways associated with the pathogenesis and progression of NAFLD may lead to a better understanding of its pathophysiology and new therapeutic approaches.

The Controversial Role of Human Gut Lachnospiraceae

The complex polymicrobial composition of human gut microbiota plays a key role in health and disease. Lachnospiraceae belong to the core of gut microbiota, colonizing the intestinal lumen from birth and increasing, in terms of species richness and their relative abundances during the host's life. Although, members of Lachnospiraceae are among the main producers of short-chain fatty acids, different taxa of Lachnospiraceae are also associated with different intra- and extraintestinal diseases. Their impact on the host physiology is often inconsistent across different studies. Here, we discuss changes in Lachnospiraceae abundances according to health and disease. With the aim of harnessing Lachnospiraceae to promote human health, we also analyze how nutrients from the host diet can influence their growth and how their metabolites can, in turn, influence host physiology.

The Response of the Gut Microbiota to Dietary Changes in the First Two Years of Life

The infant gut microbiota undergoes significant changes in the first two years of life in response to changes in the diet. The discontinuation of the milk-based diet of the first year and the introduction of solid foods in the second year of life results in a decline in bifidobacterium, a shift from infant strains of bifidobacterium to adult strains which preferentially metabolize oligosaccharides derived from plants rather than from milk, a surge in short chain fatty acids such as acetic, propionic and butyric acid from newly acquired commensal clostridium, and the transformation of primary bile acids into secondary bile acids by a limited number of newly acquired and highly specialized Clostridium spp. By 3 years of age, diet and gut microbiota closely resemble those of adults. Gut bacteria required for the production of SCFAs and secondary BAs are potential targets for the intervention of microbiome-related diseases.

Scoparone improves hepatic inflammation and autophagy in mice with nonalcoholic steatohepatitis by regulating the ROS/P38/Nrf2 axis and PI3K/AKT/mTOR pathway in macrophages

BACKGROUND AND AIMS

Scoparone has been shown to ameliorate many forms of liver disease, and several underlying molecular mechanisms involved have been previously revealed. However, the potential role of scoparone in autophagy, which is dysregulated in nonalcoholic fatty liver disease-nonalcoholic steatohepatitis (NAFLD-NASH), has not been evaluated. In the current study, we investigated the effect and potential mechanisms of scoparone in hepatic autophagy in mice with NASH.

METHODS

In vivo, mice were fed a methionine-choline deficient (MCD) diet to establish a NASH model and then subjected to treatment with or without scoparone for 4 weeks. In vitro, scoparone was applied in a hepatocellular lipid overload model in AML12 cells challenged with palmitic acid (PA) and in lipopolysaccharide (LPS)-induced RAW264.7 cells.

RESULTS

Scoparone improved impaired autophagy and several key features of NASH in mice fed an MCD diet. In vitro, scoparone had an effect on the autophagy of macrophages but not hepatocytes. In RAW264.7 cells, scoparone reduced the LPS-induced accumulation of autophagosomes and autophagy substrates, the production of reactive oxygen species (ROS) and the inflammatory response. Scoparone inhibited the upregulation of p62 transcription, which is mediated by the ROS/P38/Nrf2 axis. Chloroquine (CQ), an inhibitor of autophagic flux, significantly inhibited scoparone-mediated protection against inflammation. In addition, scoparone suppressed activation of the PI3K/AKT/mTOR pathway, and MHY1485 (an mTOR activator that inhibits autophagy) inhibited the anti-inflammatory effect of scoparone.

CONCLUSIONS

In LPS-induced macrophages, scoparone regulates autophagy and further suppresses inflammation by inhibiting the ROS/P38/Nrf2 axis and PI3K/AKT/mTOR pathway and enhancing autophagic flux. Scoparone may improve hepatic autophagy and NASH partly through enhancing autophagy in macrophages but not hepatocytes. Scoparone is expected to become a novel therapeutic drug for NASH or diseases associated with dysregulated autophagy in macrophages.

Gut Microbiota and Liver Injury (II): Chronic Liver Injury

Chronic liver injury mainly comprises viral hepatitis, fatty liver disease, autoimmune hepatitis, cirrhosis and liver cancer. It is well established that gut microbiota serves as the key upstream modulator for chronic liver injury progression. Indeed, the term "gut-liver axis" was mostly applied for chronic liver injury. In the current chapter, we will summarize the relationship between gut microbiota and chronic liver injury, including the interaction between them based on latest clinic and basic research.