Review article: emerging role of the gut microbiome in the progression of nonalcoholic fatty liver disease and potential therapeutic implications

Vinpocetine and Lactobacillus improve fatty liver in rats: role of adiponectin and gut microbiome

Therapeutics that interfere with the damage/pathogen-associated molecular patterns (DAMPs/PAMPs) have evolved as promising candidates for hepatic inflammation like that occurring in non-alcoholic fatty liver disease (NAFLD). In the current study, we examined the therapeutic impact of the phosphodiesterase-1 inhibitor vinpocetine (Vinpo), alone or when combined with Lactobacillus, on hepatic abnormalities caused by a 13-week high-fat diet (HFD) and diabetes in rats. The results show that Vinpo (10 and 20 mg/kg/day) dose-dependently curbed HFD-induced elevation of liver injury parameters in serum (ALT, AST) and tissue histopathology. These effects were concordant with Vinpo's potential to ameliorate HFD-induced fibrosis (Histological fibrosis score, hydroxyproline, TGF-β1) and oxidative stress (MDA, NOx) alongside restoring the antioxidant-related parameters (GSH, SOD, Nrf-2, HO-1) in the liver. Mechanistically, Vinpo attenuated the hepatocellular release of DAMPs like high mobility group box (HMGB)1 alongside lowering the overactivation of the pattern recognition receptors including, toll-like receptor (TLR)4 and receptor for advanced glycation end-products (RAGE). Consequently, there was less activation of the transcription factor nuclear factor-kappa B that lowered production of the proinflammatory cytokines TNF-α and IL-6 in Vinpo-treated HFD/diabetes rats. Compared to Vinpo treatment alone, Lactobacillus probiotics as adjunctive therapy with Vinpo significantly improved the disease-associated inflammation and oxidative stress injury, as well as the insulin resistance and lipid profile abnormalities via enhancing the restoration of the symbiotic microbiota. In conclusion, combining Vinpo and Lactobacillus probiotics may be a successful approach for limiting NAFLD in humans.

Distinct Gut Microbial Signature and Host Genetic Variants in Association with Liver Fibrosis Severity in Patients with MASLD

Gut microbiota might affect the severity and progression of metabolic dysfunction-associated steatotic liver disease (MASLD). We aimed to characterize gut dysbiosis and clinical parameters regarding fibrosis stages assessed by magnetic resonance elastography. This study included 156 patients with MASLD, stratified into no/mild fibrosis (F0-F1) and moderate/severe fibrosis (F2-F4). Fecal specimens were sequenced targeting the V4 region of the 16S rRNA gene and analyzed using bioinformatics. The genotyping of PNPLA3, TM6SF2, and HSD17B13 was assessed by allelic discrimination assays. Our data showed that gut microbial profiles between groups significantly differed in beta-diversity but not in alpha-diversity indices. Enriched Fusobacterium and Escherichia_Shigella, and depleted Lachnospira were found in the F2-F4 group versus the F0-F1 group. Compared to F0-F1, the F2-F4 group had elevated plasma surrogate markers of gut epithelial permeability and bacterial translocation. The bacterial genera, PNPLA3 polymorphisms, old age, and diabetes were independently associated with advanced fibrosis in multivariable analyses. Using the Random Forest classifier, the gut microbial signature of three genera could differentiate the groups with high diagnostic accuracy (AUC of 0.93). These results indicated that the imbalance of enriched pathogenic genera and decreased beneficial bacteria, in association with several clinical and genetic factors, were potential contributors to the pathogenesis and progression of MASLD.

Can modulation of gut microbiota affect anthropometric indices in patients with non-alcoholic fatty liver disease? An umbrella meta-analysis of randomized controlled trials

Background and aim

Modulating the gut microbiota population by administration of probiotics, prebiotics, and synbiotics has shown to have a variety of health benefits in different populations, particularly those with metabolic disorders. Although the promising effects of these compounds have been observed in the management of patients with non-alcoholic fatty liver disease (NAFLD), the exact effects and the mechanisms of action are yet to be understood. In the present study, we aimed to evaluate how gut microbiota modulation affects anthropometric indices of NAFLD patients to achieve a comprehensive summary of current evidence-based knowledge.

Methods

Two researchers independently searched international databases, including PubMed, Scopus, and Web of Science, from inception to June 2023. Meta-analysis studies that evaluated the effects of probiotics, prebiotics, and synbiotics on patients with NAFLD were entered into our umbrella review. The data regarding anthropometric indices, including body mass index, weight, waist circumference (WC), and waist-to-hip ratio (WHR), were extracted by the investigators. The authors used random effect model for conducting the meta-analysis. Subgroup analysis and sensitivity analysis were also performed.

Results

A total number of 13 studies were finally included in our study. Based on the final results, BMI was significantly decreased in NAFLD patients by modulation of gut microbiota [effect size (ES): -0.18, 05% CI: -0.25, -0.11, P<0.001]; however, no significant alteration was observed in weight and WC (ES: -1.72, 05% CI: -3.48, 0.03, P=0.055, and ES: -0.24, 05% CI: -0.75, 0.26, P=0.353, respectively). The results of subgroup analysis showed probiotics had the most substantial effect on decreasing BMI (ES: -0.77, 95% CI: -1.16, -0.38, P<0.001) followed by prebiotics (ES: -0.51, 95% CI: -0.76, -0.27, P<0.001) and synbiotics (ES: -0.12, 95% CI: -0.20, -0.04, P=0.001).

Conclusion

In conclusion, the present umbrella meta-analysis showed that although modulation of gut microbiota by administration of probiotics, prebiotics, and synbiotics had promising effects on BMI, no significant change was observed in the WC and weight of the patients. No sufficient data were available for other anthropometric indices including waist-to-hip ratio and waist-to-height ratio and future meta-analyses should be done in this regard.

Vitamin D and Metabolic Dysfunction-Associated Steatotic Liver Disease (MASLD): Novel Mechanistic Insights

Metabolic dysfunction-associated steatotic liver disease (MASLD) is an increasingly prevalent condition characterized by abnormal fat accumulation in the liver, often associated with metabolic disorders. Emerging evidence suggests a potential link between vitamin D deficiency and the development and progression of MASLD. The current review provides a concise overview of recent studies uncovering novel mechanistic insights into the interplay between vitamin D and MASLD. Several epidemiological studies have highlighted a significant association between low vitamin D levels and an increased risk of MASLD. Vitamin D, traditionally known for its role in bone health, has now been recognized as a key player in various physiological processes, including immune regulation and inflammation. Experimental studies using animal models have demonstrated that vitamin D deficiency exacerbates liver steatosis and inflammation, suggesting a potential protective role against MASLD. Mechanistically, vitamin D appears to modulate MASLD through multiple pathways. Firstly, the vitamin D receptor (VDR) is abundantly expressed in liver cells, indicating a direct regulatory role in hepatic function. Activation of the VDR has been shown to suppress hepatic lipid accumulation and inflammation, providing a mechanistic basis for the observed protective effects. Additionally, vitamin D influences insulin sensitivity, a critical factor in MASLD pathogenesis. Improved insulin sensitivity may mitigate the excessive accumulation of fat in the liver, thus attenuating MASLD progression. In parallel, vitamin D exhibits anti-inflammatory properties by inhibiting pro-inflammatory cytokines implicated in MASLD pathophysiology. Experimental evidence suggests that the immunomodulatory effects of vitamin D extend to the liver, reducing inflammation and oxidative stress, key drivers of MASLD, and the likelihood of hepatocyte injury and fibrosis. Understanding the complex interplay between vitamin D and MASLD provides a basis for exploring targeted therapeutic strategies and preventive interventions. As vitamin D deficiency is a modifiable risk factor, addressing this nutritional concern may prove beneficial in mitigating the burden of MASLD and associated metabolic disorders.

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

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

Performance of non-invasive tests for liver fibrosis resolution after bariatric surgery

BACKGROUND & AIMS

The value of non-invasive tests for monitoring the resolution of significant liver fibrosis after treatment is poorly investigated. We compared the performances of six non-invasive tests to predict the resolution of significant fibrosis after bariatric surgery.

METHODS

Participants were individuals with obesity submitted to needle liver biopsy at the time of bariatric surgery, and 12 and/or 60 months after surgery. We calculated the fibrosis-4 index (FIB-4), NAFLD fibrosis score (NFS), AST to platelet ratio index (APRI), Hepatic fibrosis score (HFS), Fibrotic NASH index (FNI), and Liver risk score (LRS) at each time point, and compared their performances for predicting significant fibrosis (F ≥ 2) and its resolution following surgery.

RESULTS

At baseline, 2436 patients had liver biopsy, including 261 (10.7 %) with significant fibrosis. Overall, 672 patients had pre- and post-operative biopsies (564 at M12 and 328 at M60). The fibrosis stage decreased at M12 and M60 (p < 0.001 vs M0). Resolution of significant fibrosis occurred in 58/121 (47.9 %) at M12 and 32/50 (64 %) at M60. The mean value of all tests decreased after surgery, except for FIB-4. Performances for predicting fibrosis resolution was higher at M60 than at M12 for all tests, and maximal at M60 for FNI and LRS: area under the curve 0.843 (95%CI 0.71-0.95) and 0.92 (95%CI 0.84-1.00); positive likelihood ratio 3.75 (95 % CI 1.33-10.59) and 4.58 (95 % CI 1.65-12.70), respectively.

CONCLUSIONS

Results showed the value and limits of non-invasive tests for monitoring the evolution of liver fibrosis after an intervention. Following bariatric surgery, the best performances to predict the resolution of significant fibrosis were observed at M60 with tests combining liver and metabolic traits, namely FNI and LRS.

Cross talk between the liver microbiome and epigenome in patients with metabolic dysfunction-associated steatotic liver disease

BACKGROUND

The pathogenesis of MASLD (metabolic dysfunction-associated steatotic liver disease), including its severe clinical forms, involves complex processes at all levels of biological organization. This study examined the potential link between the liver microbiome profile and epigenetic factors.

METHODS

Liver microbial DNA composition was analysed using high throughput 16S rRNA gene sequencing in 116 individuals, with 55% being female, across the spectrum of liver disease severity. Total activity of histone deacetylases (HDACs) and acetyltransferases (HATs) was assayed in nuclear extracts from fresh liver samples. In addition, we measured the global 5-hydroxymethylcytosine (5-hmC) levels of liver DNA.

FINDINGS

Patients with MASLD showed a 2.07-fold increase (p = 0.013) in liver total HAT activity. Moreover, a correlation was observed between liver total HAT activity and the score for histological steatosis (Spearman's R = 0.60, p = 1.0E-3) and disease severity (R = 0.40, p = 2.0E-2). Liver HAT and HDAC activities also showed associations with the abundance of several liver bacterial DNAs. Additionally, liver global levels of 5-hmC showed negative correlation with the read number of Bacteroidetes (R = -0.62, p = 9.3E-4) and Gammaproteobacteria (R = -0.43, p = 3.2E-2), while it was positively correlated with the abundance of Acidobacteria (R = 0.42, p = 4.1E-2) and Actinobacteria (R = 0.47, p = 1.8E-2).

INTERPRETATION

The host liver epigenome, including the activity of enzymes involved in maintaining the balance between protein acetylation and deacetylation and the global DNA hydroxy-methylation status, may be the target of microbial signals.

FUNDING

Agencia Nacional de Promoción Científica y Tecnológica, FonCyT.

The therapeutic potential of dietary intervention: based on the mechanism of a tryptophan derivative-indole propionic acid on metabolic disorders

Tryptophan (TRP) contributes to individual immune homeostasis and good condition via three complex metabolism pathways (5-hydroxytryptamine (5-HT), kynurenine (KP), and gut microbiota pathway). Indole propionic acid (IPA), one of the TRP derivatives of the microbiota pathway, has raised more attention because of its impact on metabolic disorders. Here, we retrospect increasing evidence that TRP metabolites/IPA derived from its proteolysis impact host health and disease. IPA can activate the immune system through aryl hydrocarbon receptor (AHR) and/or Pregnane X receptor (PXR) as a vital mediator among diet-caused host and microbe cross-talk. Different levels of IPA in systemic circulation can predict the risk of NAFLD, T2DM, and CVD. IPA is suggested to alleviate cognitive impairment from oxidative damage, reduce gut inflammation, inhibit lipid accumulation and attenuate the symptoms of NAFLD, putatively enhance the intestinal epithelial barrier, and maintain intestinal homeostasis. Now, we provide a general description of the relationships between IPA and various physiological and pathological processes, which support an opportunity for diet intervention for metabolic diseases.

The Role of Nuclear Receptors in the Pathogenesis and Treatment of Non-alcoholic Fatty Liver Disease

Non-alcoholic fatty liver disease (NAFLD) is a global health burden closely linked to insulin resistance, obesity, and type 2 diabetes. The complex pathophysiology of NAFLD involves multiple cellular pathways and molecular factors. Nuclear receptors (NRs) have emerged as crucial regulators of lipid metabolism and inflammation in NAFLD, offering potential therapeutic targets for NAFLD. Targeting PPARs and FXRs has shown promise in ameliorating NAFLD symptoms and halting disease progression. However, further investigation is needed to address side effects and personalize therapy approaches. This review summarizes the current understanding of the involvement of NRs in the pathogenesis of NAFLD and explores their therapeutic potential. We discuss the role of several NRs in modulating lipid homeostasis in the liver, including peroxisome proliferator-activated receptors (PPARs), liver X receptors (LXRs), farnesoid X receptors (FXRs), REV-ERB, hepatocyte nuclear factor 4α (HNF4α), constitutive androstane receptor (CAR) and pregnane X receptor (PXR).The expanding knowledge of NRs in NAFLD offers new avenues for targeted therapies, necessitating exploration of novel treatment strategies and optimization of existing approaches to combat this increasingly prevalent disease.

Insights into the role of vitamin D in targeting the culprits of non-alcoholic fatty liver disease

Vitamin D (VD) is a secosteroid hormone that is renowned for its crucial role in phospho-calcium homeostasis upon binding to the nuclear vitamin D receptor (VDR). Over and above, the pleiotropic immunomodulatory, anti-inflammatory, and metabolic roles VD plays in different disease settings started to surface in the past few decades. On the other hand, a growing body of evidence suggests a correlation between non-alcoholic fatty liver disease (NAFLD) and its progressive inflammatory form non-alcoholic steatohepatitis (NASH) with vitamin D deficiency (VDD) owing to the former's ingrained link with obesity and metabolic syndrome. Accordingly, a better understanding of the contribution of disrupted VDR signalling to NAFLD incidence and progression would provide further insights into its diagnosis, treatment modalities, and prognosis. This is especially significant as, hitherto, no drug for NAFLD has been approved. This review, therefore, sought to set forth the likely contribution of VDR signalling in NAFLD and how it might influence its multiple drivers.

WITHDRAWN: Vinpocetine and Lactobacillus improve fatty liver in rats via modulating the oxidative stress, inflammation, adiponectin and gut microbiome

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The Gut Microbial Bile Acid Modulation and Its Relevance to Digestive Health and Diseases

The human gut microbiome has been linked to numerous digestive disorders, but its metabolic products have been much less well characterized, in part due to the expense of untargeted metabolomics and lack of ability to process the data. In this review, we focused on the rapidly expanding information about the bile acid repertoire produced by the gut microbiome, including the impacts of bile acids on a wide range of host physiological processes and diseases, and discussed the role of short-chain fatty acids and other important gut microbiome-derived metabolites. Of particular note is the action of gut microbiome-derived metabolites throughout the body, which impact processes ranging from obesity to aging to disorders traditionally thought of as diseases of the nervous system, but that are now recognized as being strongly influenced by the gut microbiome and the metabolites it produces. We also highlighted the emerging role for modifying the gut microbiome to improve health or to treat disease, including the "engineered native bacteria'' approach that takes bacterial strains from a patient, modifies them to alter metabolism, and reintroduces them. Taken together, study of the metabolites derived from the gut microbiome provided insights into a wide range of physiological and pathophysiological processes, and has substantial potential for new approaches to diagnostics and therapeutics of disease of, or involving, the gastrointestinal tract.

Bile acid-mediated signaling in cholestatic liver diseases

Chronic cholestatic liver diseases, such as primary biliary cholangitis (PBC) and primary sclerosing cholangitis (PSC), are associated with bile stasis and gradually progress to fibrosis, cirrhosis, and liver failure, which requires liver transplantation. Although ursodeoxycholic acid is effective in slowing the disease progression of PBC, it has limited efficacy in PSC patients. It is challenging to develop effective therapeutic agents due to the limited understanding of disease pathogenesis. During the last decade, numerous studies have demonstrated that disruption of bile acid (BA) metabolism and intrahepatic circulation promotes the progression of cholestatic liver diseases. BAs not only play an essential role in nutrition absorption as detergents but also play an important role in regulating hepatic metabolism and modulating immune responses as key signaling molecules. Several excellent papers have recently reviewed the role of BAs in metabolic liver diseases. This review focuses on BA-mediated signaling in cholestatic liver disease.

TRANSCRIPTOMICS OF NATURAL AND SYNTHETIC VITAMIN D IN HUMAN HEPATOCYTE LIPOTOXICITY

Vitamin D (VD) has been used to prevent non-alcoholic fatty liver disease (NAFLD), a condition of lipotoxicity associated with a defective metabolism and function of this vitamin. Different forms of VD are available and can be used for this scope, but their effects on liver cell lipotoxicity remain unexplored. In this study we compared a natural formulation rich in VD2 (Shiitake Mushroom extract or SM-VD2) with a synthetic formulation containing pure VD3 (SV-VD3) and the bioactive metabolite 1,25(OH)₂-D3. These were investigated in chemoprevention mode in human HepaRG liver cells supplemented with oleic and palmitic acid to induce lipotoxicity. All the different forms of VD showed similar efficacy in reducing the levels of lipotoxicity and the changes that lipotoxicity induced on the cellular transcriptome. However, the three forms of VD generated different gene fingerprints suggesting diverse, even if functionally convergent, cytoprotective mechanisms. Main differences were 1) the number of differentially expressed genes (SV-VD3 > 1,25(OH)₂-D3 > SM-VD2), 2) their identity that demonstrated significant gene homology between SM-VD2 and 1,25(OH)₂-D3, and 3) the number and type of biological functions identified by Ingenuity Pathway Analysis as relevant to liver metabolism and cytoprotection annotations. Immunoblot confirmed a different response of VDR and other VDR-related proteins to natural and synthetic VD formulations, including FXR, PXR, PPARγ/PGC-1α, and CYP3A4 and CYP24A1. In conclusion, different responses of the cellular transcriptome drive the cytoprotective effect of natural and synthetic formulations of VD in the free fatty acid-induced lipotoxicity of human hepatocytes.

Diversity and Comparison of Intestinal Desulfovibrio in Patients with Liver Cirrhosis and Healthy People

Desulfovibrio belongs to Sulfate-reducing bacteria (SRB), which are widely present in anaerobic environments, including the human gut. Desulfovibrio has been associated with many human diseases, including chronic liver disease. However, the characteristics and difference of Desulfovibrio from fecal samples of healthy volunteers (HV) and patients with liver cirrhosis (LC) have not been fully elucidated. Here, we isolated Desulfovibrio from the feces of 6 HV and 9 LC, and 88 Desulfovibrio strains were obtained. In the feces of HV, 55% of isolated strains were D. desulfuricans, followed by D. intestinalis (15%), D. simplex (11%), D. piger (9%), D. legallii (4%), Cupidesulfovibrio oxamicus (4%) and D. fairfieldensis (2%). However, only D. desulfuricans (60%) and C. oxamicus (40%) were isolated from fecal samples of patients with LC. Our results suggest that there was a significant difference in the desulfurization ability and the H₂S production ability of different Desulfovibrio. Desulfovibrio. Furthermore, we found that Desulfovibrio isolated from the patients with LC generally had a higher hydrogen sulfide production capacity, gastrointestinal tolerance, and levels of antibiotic resistance than the same species isolated from HV. Our findings suggested that Desulfovibrio may be associated with the occurrence and development of liver cirrhosis.

The identification of metabolites from gut microbiota in NAFLD via network pharmacology

The metabolites of gut microbiota show favorable therapeutic effects on nonalcoholic fatty liver disease (NAFLD), but the active metabolites and mechanisms against NAFLD have not been documented. The aim of the study was to investigate the active metabolites and mechanisms of gut microbiota against NAFLD by network pharmacology. We obtained a total of 208 metabolites from the gutMgene database and retrieved 1256 targets from similarity ensemble approach (SEA) and 947 targets from the SwissTargetPrediction (STP) database. In the SEA and STP databases, we identified 668 overlapping targets and obtained 237 targets for NAFLD. Thirty-eight targets were identified out of those 237 and 223 targets retrieved from the gutMgene database, and were considered the final NAFLD targets of metabolites from the microbiome. The results of molecular docking tests suggest that, of the 38 targets, mitogen-activated protein kinase 8-compound K and glycogen synthase kinase-3 beta-myricetin complexes might inhibit the Wnt signaling pathway. The microbiota-signaling pathways-targets-metabolites network analysis reveals that Firmicutes, Fusobacteria, the Toll-like receptor signaling pathway, mitogen-activated protein kinase 1, and phenylacetylglutamine are notable components of NAFLD and therefore to understanding its processes and possible therapeutic approaches. The key components and potential mechanisms of metabolites from gut microbiota against NAFLD were explored utilizing network pharmacology analyses. This study provides scientific evidence to support the therapeutic efficacy of metabolites for NAFLD and suggests holistic insights on which to base further research.

Perspectives on the Underlying Etiology of HCC and Its Effects on Treatment Outcomes

Hepatocellular carcinoma (HCC) continues to be a serious medical problem with poor prognosis worldwide. The distribution of the major etiologies of HCC is changing due to the progress of anti-viral treatments, including hepatitis B virus (HBV) suppression by nucleoside/nucleotide analogues (NAs) and increased sustained virologic response (SVR) rates by direct-acting antivirals (DAAs) for hepatitis C virus (HCV), as well as the rising trend of nonviral liver disease. Although viral hepatitis remains the most common cause of HCC, non-alcoholic liver disease (NAFLD) with metabolic syndrome and alcohol-associated liver disease (ALD) are increasing. Effective and well-tolerated NAs treatment can slow the disease progression of chronic HBV infection to cirrhosis, end-stage liver disease, and reduce HCC risk. Treatment with NAs is also associated with significant improvement in the long-term survival of patients with HBV infection who already have HCC. DAAs have achieved viral elimination in almost all patients with HCV without significant adverse events, even in patients with decompensated liver cirrhosis and HCC. Similarly, DAA therapy can reduce disease progression, liver and non-liver complications, and improve the long-term survival of patients with chronic HCV infection with or without HCC. Meanwhile, NAFLD is a rapidly increasing cause of HCC along with the epidemics of obesity and type 2 diabetes globally. NAFLD-related HCC can occur in patients without cirrhosis and is known to have a lower survival rate than viral hepatitis-related HCC. Since there is currently no specific pharmacotherapy effective for NAFLD, lifestyle modification and prevention of complications are important to improve prognosis. Additionally, ALD is the second fastest-growing cause of HCC-related deaths, especially with an accelerated trend since the COVID-19 pandemic. This review provides an overview of the epidemiologic trends in the etiologies of HCC, and the progress of treatments for each etiology and the impact on outcome in the patients with HCC.

Postbiotics Prepared Using Lactobacillus paracasei CCFM1224 Prevent Nonalcoholic Fatty Liver Disease by Modulating the Gut Microbiota and Liver Metabolism

Postbiotics are rich in a variety of bioactive components, which may have beneficial effects in inhibiting hepatic lipid accumulation. In this study, we investigated the preventive effects of postbiotics (POST) prepared from Lactobacillus paracasei on non-alcoholic fatty liver disease (NAFLD). Our results showed that when mice ingested a high-fat diet (HFD) and POST simultaneously, weight gain was slowed, epididymal white fat hypertrophy and insulin resistance were suppressed, serum biochemical indicators related to blood lipid metabolism were improved, and hepatic steatosis and liver inflammation decreased. Bacterial sequencing showed that POST modulated the gut microbiota in HFD mice, increasing the relative abundance of Akkermansia and reducing the relative abundance of Lachnospiraceae NK4A136 group, Ruminiclostridium and Bilophila. Spearman’s correlation analysis revealed significant correlations between lipid metabolism parameters and gut microbes. Functional prediction results showed that the regulation of gut microbiota was associated with the improvement of metabolic status. The metabolomic analysis of the liver revealed that POST-regulated liver metabolic pathways, such as glycerophospholipid and ether lipid metabolism, pantothenate and CoA biosynthesis, some parts of amino acid metabolism, and other metabolic pathways. In addition, POST regulated the gene expression in hepatocytes at the mRNA level, thereby regulating lipid metabolism. These findings suggest that POST plays a protective role against NAFLD and may exert its efficacy by modulating the gut microbiota and liver metabolism, and these findings may be applied to related functional foods.

Synbiotic Supplementation Modulates Gut Microbiota, Regulates β-Catenin Expression and Prevents Weight Gain in ob/ob Mice: Preliminary Findings

Background: Obesity is one of the main health problems in the world today, and dysbiosis seems to be one of the factors involved. The aim of this study was to examine the impact of synbiotic supplementation on obesity and the microbiota in ob/ob mice. Twenty animals were divided into four groups: obese treated (OT), obese control (OC), lean treated (LT) and lean control (LC). All animals received a standard diet for 8 weeks. The treated groups received a synbiotic (Simbioflora-Invictus Farmanutrição Ltd., Sao Paulo, Brazil) in water, while the nontreated groups received only water. After 8 weeks, all animals were sacrificed, and gut tissue and stool samples were collected for mRNA isolation and microbiota analysis, respectively. β-Catenin, occludin, cadherin and zonulin in the gut tissue were analyzed via RT-qPCR. Microbiome DNA was extracted from stool samples and sequenced using an Ion PGM Torrent platform. Results: Synbiotic supplementation reduced body weight gain in the OT group compared with the OC group (p = 0.0398) and was associated with an increase in Enterobacteriaceae (p = 0.005) and a decrease in Cyanobacteria (p = 0.047), Clostridiaceae (p = 0.026), Turicibacterales (p = 0.005) and Coprococcus (p = 0.047). On the other hand, a significant reduction in Sutterella (p = 0.009) and Turicibacter (p = 0.005) bacteria was observed in the LT group compared to the LC group. Alpha and beta diversities were different among all treated groups. β-Catenin gene expression was significantly decreased in the gut tissue of the OT group (p ≤ 0.0001) compared to the other groups. No changes were observed in occludin, cadherin or zonulin gene expression in the gut tissue. Conclusions: Synbiotic supplementation prevents excessive weight gain, modulates the gut microbiota, and reduces β-catenin expression in ob/ob mice.

Structural and compositional segregation of the gut microbiota in HCV and liver cirrhotic patients: A clinical pilot study

Gut microbial dysbiosis during the development of Hepatitis C virus and liver-related diseases is not well studied. Nowadays, HCV and liver cirrhosis are the major concerns that cause gut bacterial alteration, which leads to dysbiosis. For this purpose, the present study was aimed at correlating the gut bacterial community of the control group in comparison to HCV and liver cirrhotic patients. A total of 23 stool samples were collected, including control (9), liver cirrhotic (8), and HCV (6). The collected samples were subjected to 16S rRNA Illumina gene sequencing. In comparison with control, a significant gut bacterial alteration was observed in the progression of HCV and liver cirrhosis. Overall, Firmicutes were significantly abundant in the whole study. No significant difference was observed in the alpha diversity of the control and patient studies. Additionally, the beta diversity based on non-metric multidimensional scaling (NMDS) has a significant difference (p = 0.005) (ANOSIM R² = 0.14) in all groups. The discriminative results based on the LEfSe tool revealed that the HCV-infected patients had higher Enterobacteriaceae and Enterobacterial, as well as Lactobacillus and Bacilli in comparison than the liver-cirrhotic patients. These taxa were significantly different from the control group (p < 0.05). Regarding prospects, a detailed analysis of the function through metagenomics and transcriptomics is needed.

Clinical Phenotyping and the Application of Precision Medicine in MAFLD

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Pterostilbene and Its Derivative 3'-Hydroxypterostilbene Ameliorated Nonalcoholic Fatty Liver Disease Through Synergistic Modulation of the Gut Microbiota and SIRT1/AMPK Signaling Pathway

Nonalcoholic fatty liver disease (NAFLD) is a recent chronic liver disease common in many developed countries and is closely associated with metabolic syndrome, such as obesity and insulin resistance. The present study was performed to investigate the effects of pterostilbene (Pt) and its derivative 3'-hydroxypterostilbene (OHPt) on free fatty acids (FFA)-induced lipid accumulation in HepG2 cells and high-fat diet (HFD)-induced NAFLD in C57BL/6J mice. The results showed that Pt and OHPt significantly ameliorated FFA-induced steatosis in HepG2 cells and enhanced lipolysis through the upregulation of SIRT1/AMPK and insulin signaling pathways. In the in vivo study, Pt and OHPt treatment resulted in reduced hepatic lipid droplets accumulation. The data showed that Pt and OHPt upregulated the SIRT1/AMPK pathway and subsequently downregulated the protein expression of SREBP-1 to activate fatty acid (FA) β-oxidation to inhibit FA synthesis. Pt and OHPt administration activated the insulin signaling pathway and further ameliorated the insulin resistance and liver function in the HFD-fed mice. Furthermore, Pt and OHPt markedly increased the numbers of Oscillospira and decreased the numbers of Allobaculum, Phascolarctobacterium, and Staphylococcus compared with those in the HFD group. These robust results indicate that Pt and OHPt are able to possess potential health benefits in improving insulin resistance and hepatic steatosis by promoting healthy populations or abundances of considered vital microbiota. Besides, OHPt is more effective than Pt, which might have promising chemotherapeutic effects for future clinical application.

NAFLD-driven HCC: Safety and efficacy of current and emerging treatment options

In light of a global rise in obesity and type 2 diabetes, non-alcoholic fatty liver disease (NAFLD) and non-alcoholic steatohepatitis (NASH) represent an increasingly important underlying aetiology of hepatocellular carcinoma (HCC). HCCs arising from lipotoxicity-mediated chronic inflammation are characterised by several unique features: in contrast to virally driven HCC, up to 50% of NAFLD-HCC occurs in patients without cirrhosis and annual HCC incidence is comparatively low, complicating current surveillance strategies. On average, patients are older and are more frequently diagnosed at an advanced stage. While locoregional treatments are probably equally effective regardless of HCC aetiology, the picture is less clear for systemic therapy. Tyrosine kinase inhibitors are probably equally effective, while there have been initial signals that immune checkpoint inhibitors may be less effective in NAFLD-HCC than in viral HCC. Current international clinical practice guidelines for HCC do not consider aetiology, as there are insufficient data to draw specific conclusions or to recommend aetiology-specific modifications to the current management of patients with HCC. However, in light of the growing relevance of NAFLD-HCC, future clinical trials should assess whether HCC aetiology - and NAFLD/NASH in particular - influence the safety and efficacy of a given treatment.

NASH and the Gut Microbiome: Implications for New Therapies

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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.

Nonalcoholic Fatty Liver Disease-A Novel Risk Factor for Recurrent Clostridioides difficile Infection

Recurrent Clostridioides difficile infections (rCDI) have a substantial impact on healthcare systems, with limited and often expensive therapeutic options. Nonalcoholic fatty liver disease (NAFLD) affects about 25% of the adult population and is associated with metabolic syndrome, changes in gut microbiome and bile acids biosynthesis, all possibly related with rCDI. The aim of this study was to determine whether NAFLD is a risk factor associated with rCDI. A retrospective cohort study included patients ≥ 60 years hospitalized with CDI. The cohort was divided into two groups: those who were and were not readmitted with CDI within 3 months of discharge. Of the 329 patients included, 107 patients (32.5%) experienced rCDI. Patients with rCDI were older, had higher Charlson Age-Comorbidity Index (CACI) and were more frequently hospitalized within 3 months. Except for chronic kidney disease and NAFLD, which were more frequent in the rCDI group, there were no differences in other comorbidities, antibiotic classes used and duration of antimicrobial therapy. Multivariable Cox regression analysis showed that age >75 years, NAFLD, CACI >6, chronic kidney disease, statins and immobility were associated with rCDI. In conclusion, our study identified NAFLD as a possible new host-related risk factor associated with rCDI.

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

BACKGROUND AND AIM

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Dietary Fruit and Vegetable Supplementation Suppresses Diet-Induced Atherosclerosis in LDL Receptor Knockout Mice

BACKGROUND

Epidemiologic studies suggest that fruit and vegetable (F&V) consumption is inversely associated with incidence of cardiovascular disease (CVD). However, evidence for causality is lacking, and the underlying mechanisms are not well understood.

OBJECTIVES

We aimed to determine whether there is a causal relation between consuming high levels of F&V and prevention of atherosclerosis, the hallmark of CVD pathogenesis. Furthermore, the underlying mechanisms were determined.

METHODS

Six-week-old male LDL receptor-knockout mice were randomly assigned to 3 diet groups (12 mice/group) for 20 wk: control (CON, 10% kcal fat, 0.20 g/kg cholesterol), atherogenic (Ath, 27% kcal fat, 0.55 g/kg cholesterol), and Ath supplemented with 15% F&V (Ath + FV) (equivalent to 8-9 servings/d in humans). F&V was added as a freeze-dried powder that was prepared from the 24 most commonly consumed F&Vs in the United States. Body weight, aortic atherosclerotic lesion area, hepatic steatosis area, serum lipid profile and proinflammatory cytokine TNF-α concentrations, gut microbiota, and liver TNF-α and fatty acid synthase (Fasn) mRNA concentrations were assessed.

RESULTS

F&V supplementation did not affect weight gain. Mice fed the Ath + FV diet had a smaller aortic atherosclerotic lesion area (71.7% less) and hepatic steatosis area (80.7% less) than those fed the Ath diet (both P < 0.001) independent of impact on weight, whereas no difference was found between Ath + FV and CON groups in these 2 pathologic markers. Furthermore, F&V supplementation prevented Ath diet-induced dyslipidemia (high concentrations of serum TG and VLDL cholesterol and lower concentrations of HDL cholesterol), reduced serum TNF-α concentration (by 21.5%), suppressed mRNA expression of liver TNF-α and Fasn, and ameliorated Ath-induced gut microbiota dysbiosis.

CONCLUSIONS

Our results indicate that consuming a large quantity and variety of F&Vs causally attenuates diet-induced atherosclerosis and hepatic steatosis in mice. These effects of F&Vs are associated with, and may be mediated through, improved atherogenic dyslipidemia, alleviated gut dysbiosis, and suppressed inflammation.

Recent Epidemiology of Nonalcoholic Fatty Liver Disease

The ongoing obesity epidemic and the increasing recognition of metabolic syndrome have contributed to the growing prevalence of nonalcoholic fatty liver disease (NAFLD), the most common form of liver disease worldwide. It is imperative to understand the incidence and prevalence of NAFLD as it is associated with a profound economic burden of hospitalizations, including the shifting trends in liver transplantation. The long-term cumulative healthcare cost of NAFLD patients has been shown to be 80% higher than that of non-NAFLD patients. We explore diagnostic challenges in identifying those with NAFLD who have a higher predilection to progress to end-stage liver disease. We aim to assess all-cause and cause-specific mortality as it relates to NAFLD.

[Features of intestinal microbiota disorders in the development of metabolic disorders in non-alcoholic fatty liver disease]

We discussed about the term intestinal permeability like as the mucosal barrier a single structural and functional conception that includes the layer of mucus, the indigenous microbiota and the epithelium of the mucosa in this publication. Information was presented about the role of the microbiota, the composition of intestinal mucus, epithelial cells and proteins of tight junctions which lead to various metabolic diseases. The complex pathogenetic interactions are formed between the intestinal mucosal barrier, metabolic disorders such as non-alcoholic fatty liver disease and cardiovascular diseases. The complex researches and modification of this interactions will allow to create personalized approaches and to prevent of these diseases.

Gut microbiota and their metabolites in the progression of non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) is the most prevalent liver disorder worldwide. It comprises a spectrum of conditions that range from steatosis to non-alcoholic steatohepatitis, with progression to cirrhosis and hepatocellular carcinoma. Currently, there is no FDA-approved pharmacological treatment for NAFLD. The pathogenesis of NAFLD involves genetic and environmental/host factors, including those that cause changes in intestinal microbiota and their metabolites. In this review, we discuss recent findings on the relationship(s) of microbiota signature with severity of NAFLD and the role(s) microbial metabolites in NAFLD progression. We discuss how metabolites may affect NAFLD progression and their potential to serve as biomarkers for NAFLD diagnosis or therapeutic targets for disease management.

Nonalcoholic steatohepatitis: the role of peroxisome proliferator-activated receptors

The increasing epidemic of obesity worldwide is linked to serious health effects, including increased prevalence of type 2 diabetes mellitus, cardiovascular disease and nonalcoholic fatty liver disease (NAFLD). NAFLD is the liver manifestation of the metabolic syndrome and includes the spectrum of liver steatosis (known as nonalcoholic fatty liver) and steatohepatitis (known as nonalcoholic steatohepatitis), which can evolve into progressive liver fibrosis and eventually cause cirrhosis. Although NAFLD is becoming the number one cause of chronic liver diseases, it is part of a systemic disease that affects many other parts of the body, including adipose tissue, pancreatic β-cells and the cardiovascular system. The pathomechanism of NAFLD is multifactorial across a spectrum of metabolic derangements and changes in the host microbiome that trigger low-grade inflammation in the liver and other organs. Peroxisome proliferator-activated receptors (PPARs) are a group of nuclear regulatory factors that provide fine tuning for key elements of glucose and fat metabolism and regulate inflammatory cell activation and fibrotic processes. This Review summarizes and discusses the current literature on NAFLD as the liver manifestation of the systemic metabolic syndrome and focuses on the role of PPARs in the pathomechanisms as well as in the potential targeting of disease.

Intestinal Virome Signature Associated With Severity of Nonalcoholic Fatty Liver Disease

BACKGROUND & AIMS

Alterations in the gut microbiome have been associated with the severity of nonalcoholic fatty liver disease (NAFLD). Previous studies focused exclusively on the bacteria in the microbiome; we investigated changes in the viral microbiome (virome) in patients with NAFLD.

METHODS

In a prospective, cross-sectional, observational study, we extracted RNA and DNA virus-like particles from fecal samples from 73 patients with NAFLD: 29 patients had an NAFLD Activity Score (NAS) of 0-4, 44 patients had an NAS of 5-8 or liver cirrhosis (LCI), 37 patients had F0-F1 fibrosis, and 36 patients had F2-F4 fibrosis. As controls, 9 individuals without liver disease and 13 patients with mild primary biliary cholangitis were included in the analysis. We performed shotgun metagenomic sequencing of virus-like particles.

RESULTS

Patients with NAFLD and NAS 5-8/LCI had a significant decrease in intestinal viral diversity compared with patients with NAFLD and NAS 0-4 or control individuals. The presence of more advanced NAFLD was associated with a significant reduction in the proportion of bacteriophages compared with other intestinal viruses. Using multivariate logistic regression analysis with leave-1-out cross validation, we developed a model, including a viral diversity index and simple clinical variables, that identified patients with NAS 5-8/LCI with an area under the curve of 0.95 (95% confidence interval, 0.91-0.99) and F2-F4 fibrosis with an area under the curve of 0.88 (95% confidence interval, 0.80-0.95). Addition of data on viral diversity significantly improved multivariate models, including those based on only clinical parameters or bacterial diversity.

CONCLUSIONS

In a study of fecal viromes from patients with NAFLD and control individuals, we associated histologic markers of NAFLD severity with significant decreases in viral diversity and proportion of bacteriophages. We developed a model based on fecal viral diversity and clinical data that identifies patients with severe NAFLD and fibrosis more accurately than models based only on clinical or bacterial data.

Pediatric Non-Alcoholic Fatty Liver Disease: Nutritional Origins and Potential Molecular Mechanisms

Non-alcoholic fatty liver disease (NAFLD) is the number one chronic liver disease worldwide and is estimated to affect nearly 40% of obese youth and up to 10% of the general pediatric population without any obvious signs or symptoms. Although the early stages of NAFLD are reversible with diet and lifestyle modifications, detecting such stages is hindered by a lack of non-invasive methods of risk assessment and diagnosis. This absence of non-invasive means of diagnosis is directly related to the scarcity of long-term prospective studies of pediatric NAFLD in children and adolescents. In the majority of pediatric NAFLD cases, the mechanisms driving the origin and rapid progression of NAFLD remain unknown. The progression from NAFLD to non-alcoholic steatohepatitis (NASH) in youth is associated with unique histological features and possible immune processes and metabolic pathways that may reflect different mechanisms compared with adults. Recent data suggest that circulating microRNAs (miRNAs) are important new biomarkers underlying pathways of liver injury. Several factors may contribute to pediatric NAFLD development, including high-sugar diets, in utero exposures via epigenetic alterations, changes in the neonatal microbiome, and altered immune system development and mitochondrial function. This review focuses on the unique aspects of pediatric NAFLD and how nutritional exposures impact the immune system, mitochondria, and liver/gastrointestinal metabolic health. These factors highlight the need for answers to how NAFLD develops in children and for early stage-specific interventions.

Role of Agents for the Treatment of Diabetes in the Management of Nonalcoholic Fatty Liver Disease

PURPOSE OF REVIEW

Nonalcoholic fatty liver disease (NAFLD) is an often unrecognized complication of type 2 diabetes (T2DM) associated with significant economic burden and poor long-term hepatic and extrahepatic outcomes. Our goal is to review evidence about the complex association between NAFLD and T2DM and highlight the potential for disease co-management with the available medications used for the treatment of diabetes.

RECENT FINDINGS

A milieu of metabolic factors such as insulin resistance, glucotoxicity, and lipotoxicity, as well as genetics and other factors, contribute to the pathogenesis and co-existence of NAFLD with T2DM. The presence of T2DM in patients with NAFLD increases the risk of disease progression to steatohepatitis (NASH) and advanced fibrosis, cirrhosis, and even hepatocellular carcinoma. In addition to lifestyle modification, pioglitazone and glucagon-like peptide 1 receptor agonists (GLP-1RAs) both reduce the high cardiovascular risk and improve liver histology in patients with NAFLD. Sodium-glucose cotransporter (SGLT-2) inhibitors also appear to reverse metabolic abnormalities as well as liver disease in NAFLD, but their impact on liver histology has not been fully established. Lastly, metformin, dipeptidyl dipetidase-4 (DPP-4) inhibitors, and insulin appear to have modest to no effect on modifying the natural history of NAFLD. Early recognition of NAFLD and monitoring for NASH with advanced liver fibrosis in patients with T2DM are crucial. The presence of NASH in a patient with T2DM should call for taking advantage of antidiabetic medications with proven efficacy to improve cardiometabolic health and prevent liver disease progression.

The role of TLR4/MyD88/NF-κB pathway in periodontitis-induced liver inflammation of rats

OBJECTIVES

The aim of this study was to clarify the immune mechanism of hepatic injury induced by periodontitis using a rat model.

METHODS

Twenty-four SPF male Wistar rats were randomly divided into two groups: control group (CG) and periodontitis group (PG). In order to induce experimental periodontitis, we tied the wire ligature around bilateral maxillary first molar of rats. After 8 weeks, the following indicators were valued: gingival index, tooth mobility, probing pocket depth; indexes about oxidative stress and circulating biomarkers; bone retraction by micro-CT analysis; Toll-like receptor 4 (TLR4), myeloid differential protein-88 (MyD88), and nuclear factor kappa B (NF-κB) by qRT-PCR and Western blotting; tumor necrosis factor α (TNF-α), and interleukin-6 (IL-6) by qRT-PCR and immunohistochemical staining; inflammation of periodontal and hepatic tissues by histopathological observation.

RESULTS

Periodontal indicators and micro-CT results showed the raised levels of inflammatory response and bone retraction in PG compared with CG. The mRNA and protein levels of TLR4, MyD88, NF-κB, TNF-α, and IL-6 have indicated high values in PG versus CG. Histopathological analysis revealed a correlation between periodontitis and hepatic injury.

CONCLUSION

TLR4/MyD88/NF-κB pathway may play a role in periodontitis-induced liver inflammation of rats.

Genetic Pathways in Nonalcoholic Fatty Liver Disease: Insights From Systems Biology

Nonalcoholic fatty liver disease (NAFLD) represents a burgeoning worldwide epidemic whose etiology reflects multiple interactions between environmental and genetic factors. Here, we review the major pathways and dominant genetic modifiers known to be relevant players in human NAFLD and which may determine key components of the heritability of distinctive disease traits including steatosis and fibrosis. In addition, we have employed general assumptions which are based on known genetic factors in NAFLD to build a systems biology prediction model that includes functional enrichment. This prediction model highlights additional complementary pathways that represent plausible intersecting signaling networks that we define here as an NAFLD-Reactome. We review the evidence connecting variants in each of the major known genetic modifiers (variants in patatin-like phospholipase domain containing 3, transmembrane 6 superfamily member 2, membrane-bound O-acyltransferase domain containing 7, glucokinase regulator, and hydroxysteroid 17-beta dehydrogenase 13) to NAFLD and expand the associated underlying mechanisms using functional enrichment predictions, based on both preclinical and cell-based experimental findings. These major candidate gene variants function in distinct pathways, including substrate delivery for de novo lipogenesis; mitochondrial energy use; lipid droplet assembly, lipolytic catabolism, and fatty acid compartmentalization; and very low-density lipoprotein assembly and secretion. The NAFLD-Reactome model expands these pathways and allows for hypothesis testing, as well as serving as a discovery platform for druggable targets across multiple pathways that promote NAFLD development and influence several progressive outcomes. In conclusion, we summarize the strengths and weaknesses of studies implicating selected variants in the pathophysiology of NAFLD and highlight opportunities for future clinical research and pharmacologic intervention, as well as the implications for clinical practice.

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

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

[Pathogenesis of non-alcoholic fatty liver disease]

Non-Alcoholic Fatty Liver Disease (NAFLD) is a complex chronic disease resulting from an interaction between genetic and environmental factors. The phenotype and pathophysiology of NAFLD is heterogeneous. NAFLD is a continuum of histological lesions of the liver from steatosis, Non-Alcoholic SteatoHepatitis (NASH), NASH with fibrosis, cirrhosis to hepatocellular carcinoma. The pathophysiology encompasses a dysfunction in fatty tissue (sub-cutaneous and visceral) associated with insulin-resistance and metabolic inflammation. NAFLD is a "multi-systemic" disease. Reciprocal and aggravating interactions exist between NAFLD, cardiovascular anomalies and diabetes. The understanding of the mechanisms responsible for NAFLD allows the identification of potential novel therapeutic targets.

Vitamin D and nonalcoholic fatty liver disease

PURPOSE OF REVIEW

Vitamin D deficiency may impact disease progression of nonalcoholic fatty liver disease (NAFLD). The aim of this work was to review recent studies examining either vitamin D status or the effects of supplementation in patients with NAFLD, along with investigating the roles of genetic polymorphisms and the gut microbiome.

RECENT FINDINGS

Six heterogeneous observational studies of vitamin D status, and four randomized controlled intervention trials of vitamin D supplementation in NAFLD were conflicting. All studies were hampered by the challenges of diagnosing NAFLD, were underpowered, and lacked data on clinically important outcomes. The results of three cross-sectional studies, including a Mendelian randomization study, provide limited evidence for a role for genetic modifiers of vitamin D status in NAFLD. Genetic and experimental evidence suggests that vitamin D and the vitamin D receptor (VDR) may influence the gut microbiome in health and disease.

SUMMARY

The evidence relating either lower vitamin D status to the prevalence and severity of NAFLD, or examining vitamin D supplementation in patients with NAFLD is inconclusive. Larger, higher quality trials with relevant endpoints are needed. Further mechanistic studies on the roles of vitamin D and VDR in influencing the gut-liver axis in NAFLD are warranted.

Current Status in Testing for Nonalcoholic Fatty Liver Disease (NAFLD) and Nonalcoholic Steatohepatitis (NASH)

Nonalcoholic fatty liver disease (NAFLD) is the most common chronic liver disease in Western countries with almost 25% affected adults worldwide. The growing public health burden is getting evident when considering that NAFLD-related liver transplantations are predicted to almost double within the next 20 years. Typically, hepatic alterations start with simple steatosis, which easily progresses to more advanced stages such as nonalcoholic steatohepatitis (NASH), fibrosis and cirrhosis. This course of disease finally leads to end-stage liver disease such as hepatocellular carcinoma, which is associated with increased morbidity and mortality. Although clinical trials show promising results, there is actually no pharmacological agent approved to treat NASH. Another important problem associated with NASH is that presently the liver biopsy is still the gold standard in diagnosis and for disease staging and grading. Because of its invasiveness, this technique is not well accepted by patients and the method is prone to sampling error. Therefore, an urgent need exists to find reliable, accurate and noninvasive biomarkers discriminating between different disease stages or to develop innovative imaging techniques to quantify steatosis.