Potential mechanisms linking gut microbiota and portal hypertension

Gut-related molecules as potential biomarkers in patients with decompensated cirrhosis

INTRODUCTION AND OBJECTIVES

Microbial translocation contributes to cirrhosis progression and complications. This study aims to investigate whether molecules related to intestinal permeability or microbial translocation can serve as prognostic biomarkers in patients with decompensated cirrhosis.

MATERIALS AND METHODS

We prospectively evaluated hospitalized patients with decompensated cirrhosis for liver function, complications during hospitalization, in-hospital mortality, composite outcomes of in-hospital mortality and complications, 12-month mortality, and survival rates. Blood samples were collected upon admission, and 1,3 beta-D-glucan, zonulin, calprotectin, and lipopolysaccharide-binding protein were measured using commercial kits.

RESULTS

Ninety-one patients with decompensated cirrhosis were enrolled. The mean age was 58 ± 12 years; 57% were male. The three main cirrhosis etiologies were hepatitis C (35%), alcohol (25%), and non-alcoholic steatohepatitis (17%). In terms of liver function, 52% were Child C, and 68% had model for end-stage liver disease ≥15. The in-hospital and one-year mortality rates were 31% and 57%, respectively. Child-Pugh, 1,3 beta-glucan, and model for end-stage liver disease were positively correlated; zonulin was associated with complications during hospitalization (acute kidney injury) and composite outcomes, and calprotectin was associated with all outcomes except 12-month mortality.

CONCLUSIONS

Serum calprotectin and zonulin levels emerge as noninvasive prognostic biomarkers for potentially unfavorable outcomes in patients with decompensated cirrhosis.

Gut Microbiota and Sinusoidal Vasoregulation in MASLD: A Portal Perspective

Metabolic dysfunction-associated steatotic liver disease (MASLD) is a common condition with heterogeneous outcomes difficult to predict at the individual level. Feared complications of advanced MASLD are linked to clinically significant portal hypertension and are initiated by functional and mechanical changes in the unique sinusoidal capillary network of the liver. Early sinusoidal vasoregulatory changes in MASLD lead to increased intrahepatic vascular resistance and represent the beginning of portal hypertension. In addition, the composition and function of gut microbiota in MASLD are distinctly different from the healthy state, and multiple lines of evidence demonstrate the association of dysbiosis with these vasoregulatory changes. The gut microbiota is involved in the biotransformation of nutrients, production of de novo metabolites, release of microbial structural components, and impairment of the intestinal barrier with impact on innate immune responses, metabolism, inflammation, fibrosis, and vasoregulation in the liver and beyond. The gut-liver axis is a conceptual framework in which portal circulation is the primary connection between gut microbiota and the liver. Accordingly, biochemical and hemodynamic attributes of portal circulation may hold the key to better understanding and predicting disease progression in MASLD. However, many specific details remain hidden due to limited access to the portal circulation, indicating a major unmet need for the development of innovative diagnostic tools to analyze portal metabolites and explore their effect on health and disease. We also need to safely and reliably monitor portal hemodynamics with the goal of providing preventive and curative interventions in all stages of MASLD. Here, we review recent advances that link portal metabolomics to altered sinusoidal vasoregulation and may allow for new insights into the development of portal hypertension in MASLD.

Effect of Probiotics on Portal Hypertension (PH) with Cirrhosis: A Systematic Review and Meta-Analysis

INTRODUCTION

There are many options for the reduction of portal hypertension (pH) in cirrhotic patients, but all the current ones have side effects. Probiotics are a new approach for ameliorating the hyperdynamic circulation of cirrhotic patients. The aim of this study is to measure the effect of probiotics on pH in cirrhosis for the first time.

METHODS

A search was conducted across four electronic databases (PubMed, Scopus, Web of Science, Cochrane) for English-language records evaluating probiotic effects on pH in cirrhotic patients. Quality assessment used the Cochrane Collaboration's tool, employing a random-effects model in statistical analysis with Stata software version 1.

RESULTS

A search yielded 1,251 articles, which were narrowed down to 5 through screening. These studies, involving 158 participants across Canada, India, Spain, and Russia, focused on probiotic interventions in cirrhotic patients. Meta-analysis of two RCTs (66 participants) indicated a significant decrease in hepatic venous pressure gradient (HVPG) (SMD: -0.60 [-1.09, -0.12]). In single-arm analysis, four studies (58 participants) showed a substantial reduction in HVPG with probiotic use compared to the control (SMD: -2.55 [-3.42, -1.68]).

CONCLUSION

In summary, it showcased a notable reduction in HVPG compared to the control group, indicating a potential advantage of probiotics in decreasing pH in cirrhotic patients. Further research with larger samples and robust designs is warranted.

Gut-Liver Axis Dysregulation in Portal Hypertension: Emerging Frontiers

Portal hypertension (PH) is a complex clinical challenge with severe complications, including variceal bleeding, ascites, hepatic encephalopathy, and hepatorenal syndrome. The gut microbiota (GM) and its interconnectedness with human health have emerged as a captivating field of research. This review explores the intricate connections between the gut and the liver, aiming to elucidate how alterations in GM, intestinal barrier function, and gut-derived molecules impact the development and progression of PH. A systematic literature search, following PRISMA guidelines, identified 12 original articles that suggest a relationship between GM, the gut-liver axis, and PH. Mechanisms such as dysbiosis, bacterial translocation, altered microbial structure, and inflammation appear to orchestrate this relationship. One notable study highlights the pivotal role of the farnesoid X receptor axis in regulating the interplay between the gut and liver and proposes it as a promising therapeutic target. Fecal transplantation experiments further emphasize the pathogenic significance of the GM in modulating liver maladies, including PH. Recent advancements in metagenomics and metabolomics have expanded our understanding of the GM's role in human ailments. The review suggests that addressing the unmet need of identifying gut-liver axis-related metabolic and molecular pathways holds potential for elucidating pathogenesis and directing novel therapeutic interventions.

Association of gut microbiota with portal vein pressure in patients with liver cirrhosis undergoing living donor liver transplantation

Background and Aim

Many recent studies have shown a relationship between various systemic diseases and the gut microbiota (GM), with the gut-liver axis receiving particular attention. In contrast, no report has comprehensively shown the effects of GM on the pathophysiology of patients undergoing living donor liver transplantation (LDLT).

Method

We enrolled 16 recipients who underwent LDLT for liver cirrhosis, and 17 donors constituted the reference group. We examined the differences in GM between recipients and donors. We also examined the relationships between GM, short-chain fatty acids, and portal vein pressure (PVP) in recipients.

Results

There was no significant difference in alpha-diversity between the recipients and donors, but there was variation in beta-diversity among the recipients. The abundance of the phylum Bacteroidetes was significantly higher in recipients than in donors (P = 0.016), and it was positively correlated with PVP (r = 0.511, P = 0.043). Propionic acid, which is a component of short-chain fatty acids, was positively correlated with PVP (r = 0.544, P = 0.0295), the phylum Bacteroidetes (r = 0.677, P = 0.004), and total bilirubin concentration (r = 0.501, P = 0.048). Propionic acid was negatively correlated with serum albumin concentration (r = -0.482, P = 0.043).

Conclusion

Our findings suggest relationships between fecal Bacteroidetes levels, propionic acid concentrations, and PVP in patients with liver cirrhosis undergoing LDLT.

Potential contribution of the gut microbiota to the development of portal vein thrombosis in liver cirrhosis

Background

Portal vein thrombosis (PVT) is a serious complication of liver cirrhosis (LC) and is closely related to gut homeostasis. The study aimed to investigate the composition of gut microbiota and its putative role in PVT development in LC.

Methods

33 patients with LC admitted between January 2022 and December 2022 were enrolled in this study. Based on imaging findings, they were categorized into LC without PVT (n = 21) and LC with PVT (n = 12) groups. Fecal samples were collected from each participant and underwent 16S rDNA sequencing.

Results

D-Dimer and platelet elevations were the main clinical features of LC with PVT. The alpha and beta diversity of the gut microbiota in LC with PVT group was found to be significantly higher compared to the control group. The structure of the gut microbiota was significantly different between the two groups. Based on LEfSe data, the genera Akkermansia, Eubacterium hallii group, Fusicatenibacter, and Anaerostipes were enriched in the LC with PVT, while Enterococcus, Weissella, Bacteroides, and Subdoligranulum were enriched in those of the LC subjects. Changes in microbiota structure result in significant differences in gut microbiota metabolism between the two groups. Altered levels of the microbiota genera were shown to be correlated with coagulation factor parameters. In animal experiments, the addition of Bacteroides reversed the CCl4-induced PVT.

Conclusion

Liver cirrhosis with PVT led to a disorder in the gut microbiota, which was characterized by an increase in pathogenic bacteria and a decrease in beneficial bacteria. Furthermore, modulating the gut microbiota, especially Bacteroides, may be a promising therapeutic approach to reduce the progression of PVT in LC.

Electroacupuncture relieves portal hypertension by improving vascular angiogenesis and linking gut microbiota in bile duct ligation rats

The pathological increase in the intrahepatic resistance and decrease peripheral vascular tone in the development of portal hypertension (PHT). PHT has been linked to lower microbial diversity and weakened intestinal barrier, and interplay alters inflammatory signaling cascades. Electroacupuncture (EA) may ameliorate the inflammatory response and limit arterial vasodilatation and portal pressure. This study addresses the possible mechanisms underlying putative hemodynamics effects of EA in PHT rats. PHT was induced by bile duct ligation (BDL) over 7 days in rats. BDL rats were treated with low-frequency EA (2 Hz) at acupoint, ST36, 10 min once daily for 7 consecutive days. EA significantly reduced portal pressure and enhanced maximum contractile responses in the aorta, and blunts the angiogenesis cascade in PHT rats. EA decreased the aortic angiogenesis signaling cascade, reflected by downregulated of ICAM1, VCAM1, VEGFR1, and TGFβR2 levels. In addition, EA preserved claudin-1, occludin, and ZO-1 levels in BDL-induced PHT model. Furthermore, EA demonstrates to have a positive effect on the gut Bacteroidetes/Firmicutes ratio and to reduce pro-inflammatory cytokines and endotoxins. These results summarize the potential role of EA in the gut microbiota could potentially lead to attenuate intestine injury which could further contribute to vascular reactivity in PHT rats.

Transjugular Intrahepatic Portosystemic Shunt Benefits for Hepatic Sinusoidal Obstruction Syndrome Associated with Consumption of Gynura Segetum: a Propensity Score-Matched Analysis

PURPOSE

Pyrrolidine alkaloids-related hepatic sinusoidal obstruction syndrome (PA-HSOS) is associated with a high mortality rate without standardized therapy. The efficacy of transjugular intrahepatic portosystemic shunts (TIPS) remains controversial. The study aimed to explore the risk factors influencing the clinical response in patients with PA-HSOS related to Gynura segetum (GS) to assess the disease prognosis at an early stage and to evaluate the efficacy of TIPS in these patients.

METHODS

This study retrospectively enrolled patients diagnosed with PA-HSOS between January 2014 and June 2021 with a clear history of exposure to GS. Univariate and multivariate logistic regression analyses were used to evaluate the risk factors influencing the clinical response in patients with PA-HSOS. Propensity score matched (PSM) was performed to compensate for differences in baseline characteristics between patients with and without TIPS. The primary outcome was the clinical response defined as the disappearance of ascites with normal total bilirubin levels and/or a reduction of elevated transaminase levels < 50% within 2 weeks.

RESULTS

A total of 67 patients were identified in our cohort with a clinical response rate of 58.2%. Of these, thirteen patients were assigned to the TIPS group and 54 to the conservative treatment group. Logistic regression analysis revealed that TIPS treatment (P = 0.047), serum globulin levels (P = 0.043), and prothrombin time (P = 0.001) were independent factors influencing clinical response. After PSM, there was a higher long-term survival rate of patients (92.3% vs. 51.3%, P = 0.021) and a shorter hospital stay (P = 0.043), but a high trend in hospital costs (P = 0.070) in the TIPS group. The 6-month survival probability in patients undergoing TIPS therapy was more than ninefold higher than in patients without receiving that treatment [hazard ratio (95% CI) = 9.304 (4.250, 13.262), P < 0.05].

CONCLUSIONS

TIPS therapy may be an effective treatment option for patients with GS-related PA-HSOS.

Transjugular intrahepatic Porto-systemic shunt positively influences the composition and metabolic functions of the gut microbiota in cirrhotic patients

BACKGROUND & AIMS

Cirrhosis and its complications may affect gut microbiota (GM) composition. Transjugular intrahepatic portosystemic shunt (TIPS) represents the most effective treatment for portal hypertension (PH). We aimed to evaluate whether TIPS placement modifies GM composition and metabolic function.

METHODS

A compositional and functional GM analysis was prospectively performed in 13 cirrhotic patients receiving TIPS. Patients receiving systemic or non-absorbable antibiotics for any indications were excluded. Fecal samples were collected before and three months after TIPS. GM was analyzed by 16S ribosomal RNA sequencing. Small- and medium-chain fatty acids (SCFAs and MCFAs, respectively) were measured by gas chromatography/mass spectrometry.

RESULTS

TIPS placement resulted in a mean 48% reduction in portal-caval pressure gradient. No recurrence of PH related complications was observed. After TIPS, increased levels of Flavonifractor spp. (p = 0.049), and decreased levels of Clostridiaceae (p = 0.024), these latter linked to abdominal infections in cirrhotic patients, were observed. No differences were found in the SCFAs signature while analysis of MCFA profiles showed a decreased abundance of pro-inflammatory isohexanoic (p<0.01), 2-ethylhexanoic (p<0.01) and octanoic acids (p<0.01) after TIPS.

CONCLUSION

Correction of PH following TIPS results in modifications of GM composition which could be potentially beneficial and reduces the levels of fecal pro-inflammatory MCFAs.

Oral microbiota and liver diseases

Gut microbiota plays a crucial role in our health and particularly liver diseases, including NAFLD, cirrhosis, and HCC. Oral microbiome and its role in health and disease represent an active field of research. Several lines of evidence have suggested that oral microbiota dysbiosis represents a major factor contributing to the occurrence and progression of many liver diseases. The human microbiome is valuable to the diagnosis of cancer and provides a novel strategy for targeted therapy of HCC. The most studied liver disease in relation to oral-gut-liver axis dysbiosis includes MAFLD; however, other diseases include Precancerous liver disease as viral liver diseases, liver cirrhosis, AIH and liver carcinoma (HCC). It seems that restoring populations of beneficial organisms and correcting dysbiosis appears to improve outcomes in liver disorders. We discuss the possible role of oral microbiota in these diseases.

Liver Cirrhosis and Portal Hypertension

The understanding of pathogenesis of portal hypertension in patients with liver cirrhosis continues to evolve. In addition to progressive fibrosis, cirrhosis is characterized by parenchymal extinction and vascular remodelling, causing architectural distortion. Existence of prothrombotic state and more recently, intestinal bacterial dysbiosis are recently described in the pathogenesis of portal hypertension. Clinically significant portal hypertension (CSPH) is an important prognostic milestone in patients with liver cirrhosis. This is a pre-symptomatic phase that predicts the development of varices, ascites and importantly increased risk of Hepatocellular carcinoma (HCC). CSPH is associated with significantly reduced survival. Endoscopic surveillance is necessary in these patients. Non-selective Beta-blocker is the preferred therapy for primary prophylaxis in the management of portal hypertension. Patients with acute variceal bleed should be resuscitated appropriately, followed by vasoactive drugs and endoscopic therapy. Early TIPS should be considered in those with refractory bleed or in endoscopic treatment failure. Application of artificial intelligence and machine learning may be useful in future for identifying patients at risk of variceal hemorrhage.

Antibiotics and probiotics on hepatic venous pressure gradient in cirrhosis: A systematic review and a meta-analysis

Background

Modulation of the gut microbiome could favorably alter the hepatic venous pressure gradient (HVPG) in cirrhosis and portal hypertension (PH).

Aim

This meta-analysis was to evaluate the effects of microbiome-targeted therapies (MTTs) on HVPG in persons with cirrhosis and PH.

Methods

PubMed, The Cochrane Library, Embase, Web of Science and Scopus were searched for randomized clinical trials (RCTs) analyzing the effects on HVPG in people with cirrhosis who received MTTs. Clinical outcomes were pooled using RevMan5.3 software. A trial sequential analysis was applied to calculate the required information size and evaluate the credibility of the meta-analysis results.

Results

A total of six studies were included. MTTs were associated with a reduction of 1.22 mm Hg in HVPG (95% CI: -2.31, -0.14 mmHg, P = 0.03). Subgroup analysis showed a greater reduction with longer duration (-1.88 mmHg;95% CI: -3.23, -0.53; P = 0.006). In the trial sequential analysis of HVPG reduction, the cumulative Z curve crossed the traditional significance boundary without the achievement of required information size (330).

Conclusions

MTTs may be associated with a reduction in HVPG in patients with cirrhosis and PH. Microbiome-targeted therapies merit additional large-sample studies to define the efficacy of HVPG.

Systematic review registration

PROSPERO 2020: CRD4202021609.

Influence of Gut–Liver Axis on Portal Hypertension in Advanced Chronic Liver Disease: The Gut Microbiome as a New Protagonist in Therapeutic Management

Clinically significant portal hypertension is associated with most complications of advanced chronic liver disease (ACLD), including variceal bleeding, ascites, spontaneous bacterial peritonitis, hepatorenal syndrome, and hepatic encephalopathy. Gut dysbiosis is a hallmark of ACLD with portal hypertension and consists of the overgrowth of potentially pathogenic bacteria and a decrease in autochthonous bacteria; additionally, congestion makes the intestinal barrier more permeable to bacteria and their products, which contributes to the development of complications through inflammatory mechanisms. This review summarizes current knowledge on the role of the gut–liver axis in the pathogenesis of portal hypertension, with a focus on therapies targeting portal hypertension and the gut microbiota. The modulation of the gut microbiota on several levels represents a major challenge in the upcoming years; in-depth characterization of the molecular and microbiological mechanisms linking the gut–liver axis to portal hypertension in a bidirectional relationship could pave the way to the identification of new therapeutic targets for innovative therapies in the management of ACLD.

Regulatory effect of gut microbes on blood pressure

Hypertension is an important global public health issue because of its high morbidity as well as the increased risk of other diseases. Recent studies have indicated that the development of hypertension is related to the dysbiosis of the gut microbiota in both animals and humans. In this review, we outline the interaction between gut microbiota and hypertension, including gut microbial changes in hypertension, the effect of microbial dysbiosis on blood pressure (BP), indicators of gut microbial dysbiosis in hypertension, and the microbial genera that affect BP at the taxonomic level. For example, increases in Lactobacillus, Roseburia, Coprococcus, Akkermansia, and Bifidobacterium are associated with reduced BP, while increases in Streptococcus, Blautia, and Prevotella are associated with elevated BP. Furthermore, we describe the potential mechanisms involved in the regulation between gut microbiota and hypertension. Finally, we summarize the commonly used treatments of hypertension that are based on gut microbes, including fecal microbiota transfer, probiotics and prebiotics, antibiotics, and dietary supplements. This review aims to find novel potential genera for improving hypertension and give a direction for future studies on gut microbiota in hypertension.

Microbiota transplantation in portal hypertension: promises and pitfalls

In this commentary, we discuss new findings indicating that microbiota transplantation has favorable impact on portal hypertension (PH) in the experimental model of cirrhosis induced by bile duct ligation (BDL) (Huang et al.; Clin Sci (Lond) (2021) 135(24): 2709-2728, doi: 10.1042/CS20210602). Sinusoidal PH is an ominous outcome of advanced chronic liver disease, characterized by increased intrahepatic vascular resistance (IHVR), splanchnic hyperemia, and the development of portosystemic collaterals. In the work of Huang et al., microbiota transplantation not only alleviated splanchnic hyperdynamic circulation by improving vascular responsiveness and decreasing mesenteric angiogenesis, but also reduced blood flow in portosystemic collaterals. Surprisingly, however, microbiota transplantation had no effect on intrahepatic vasoconstriction in this experimental model. We discuss these observations in the context of recent literature showing that manipulation of the gut microbiota (either by transplantation or through the use of probiotics) may improve IHVR, which is one of the earliest abnormalities in the pathogenesis of sinusoidal PH. Further research is needed to explore the specific molecular and cellular targets associated with the correction of dysbiosis in liver disease.

The Effects of Helicobacter Pylori Eradication on Liver Function and Metabolic Profile in Non-diabetic Non-alcoholic Steatohepatitis: A 5-year Randomized Clinical Trial

BACKGROUND: To evaluate the effects of Helicobacter pylori (HP) eradication on liver function tests (LFT) and fat content (LFC) in non-diabetic non-alcoholic steatohepatitis (NASH). METHODS: This randomized clinical trial included dyspeptic HP infected non-diabetic NASH participants. The intervention arm received HP eradication treatment, while the control arm did not get any HP treatment. In the meantime, the standard management of NASH was performed in both trial arms. Mean alterations in LFT were the primary outcome and the secondary outcomes included the mean changes in LFC and serum metabolic profile. The trial follow-up period was 5 years. RESULTS: 40 participants (female: 20), with a mean age of 41.58 (±12.31) years, were enrolled in the study. The HP eradication arm included 20 participants (female: 11) with a mean age of 40.25 (±10.59) years, and the control arm consisted of 20 individuals (female: 9) with a mean age of 42.90 (±13.97) years. The tests of within-subjects effects showed a significant decrease in mean serum alanine aminotransferase (ALT; P=0.007), triglyceride (TG; P=0.04), cholesterol (P=0.004), and fasting blood sugar (FBS; P<0.001), and an increase in high-density lipoprotein (HDL; P=0.04) in both research groups during the study period. The tests of between-subjects effects demonstrated a more significant decrement of FBS in HP eradicated patients than the controls (P=0.02). The reduction in waist circumference, aspartate aminotransferase (AST), ALT, alkaline phosphatase, triglyceride, cholesterol, low-density lipoprotein, insulin, and LFC were more prominent in the intervention group than the controls; however, these differences were not statistically significant. CONCLUSION: Adding HP eradication treatment to standard NASH treatment showed more therapeutic effect thanthe standard NASH treatment protocol alone regarding the decrement of FBS in participants with dyspeptic non-diabetic NASH. Considering the non-statistically significant improvement in other metabolic indices and LFT in this trial, further studies are recommended.

Microbiota transplants from feces or gut content attenuated portal hypertension and portosystemic collaterals in cirrhotic rats

Liver cirrhosis and portal hypertension is the end of chronic liver injury with hepatic, splanchnic and portosystemic collateral systems dysregulation. Liver injury is accompanied by gut dysbiosis whereas dysbiosis induces liver fibrosis, splanchnic angiogenesis and dysregulated vascular tones vice versa, making portal hypertension aggravated. It has been proved that intestinal microbiota transplantation alleviates dysbiosis. Nevertheless, the influences of microbiota transplantation on cirrhosis-related portal hypertension are not so clear. Liver cirrhosis with portal hypertension was induced by bile duct ligation (BDL) in rats. Sham rats were surgical controls. Rats randomly received vehicle, fecal or gut (terminal ileum) material transplantation. The results showed that microbiota transplantation from feces or gut material significantly reduced portal pressure in cirrhotic rats (P=0.010, 0.044). Hepatic resistance, vascular contractility, fibrosis and relevant protein expressions were not significantly different among cirrhotic rats. However, microbiota transplantation ameliorated splanchnic hyperdynamic flow and vasodilatation. Mesenteric angiogenesis, defined by whole mesenteric window vascular density, decreased in both transplantation groups and phosphorylated endothelial nitric-oxide synthase (eNOS) was down-regulated. Portosystemic shunts determined by splenorenal shunt (SRS) flow decreased in both transplantation groups (P=0.037, 0.032). Shunting severity assessed by microsphere distribution method showed consistent results. Compared with sham rats, cirrhotic rats lacked Lachnospiraceae. Both microbiota transplants increased Bifidobacterium. In conclusion, microbiota transplantation in cirrhotic rats reduced portal pressure, alleviated splanchnic hyperdynamic circulation and portosystemic shunts. The main beneficial effects may be focused on portosystemic collaterals-related events, such as hepatic encephalopathy and gastroesophageal variceal hemorrhage. Further clinical investigations are mandatory.

Novel Sesquiterpene Glycoside from Loquat Leaf Alleviates Type 2 Diabetes Mellitus Combined with Nonalcoholic Fatty Liver Disease by Improving Insulin Resistance, Oxidative Stress, Inflammation, and Gut Microbiota Composition

Nonalcoholic fatty liver disease (NAFLD) is strongly associated with type 2 diabetes mellitus (T2DM). Sesquiterpene glycosides from loquat leaf achieved beneficial effects on metabolic syndromes such as NAFLD and diabetes; however, their specific activity and underlying mechanism on T2DM-associated NAFLD have not yet been fully understood. In the present study, we found that sesquiterpene glycoside 3 (SG3), a novel sesquiterpene glycoside isolated from loquat leaf, was able to prevent insulin resistance (IR), oxidative stress, and inflammation. In db/db mice, SG3 administration (25 and 50 mg/kg/day) inhibited obesity, hyperglycemia, and the release of inflammatory cytokines. SG3 (5 and 10 μM) also significantly alleviated hepatic lipid accumulation, oxidative stress, and inflammatory response induced by high glucose combined with oleic acid in HepG2 cells. Western blotting analysis showed that these effects were related to repair the abnormal insulin signaling and inhibit the cytochrome P450 2E1 (CYP2E1) and NOD-like receptor family pyrin domain-containing 3 (NLRP3), both in vivo and in vitro. In addition, SG3 treatment could decrease the ratio of Firmicutes/Bacteroidetes and increase the relative abundance of Lachnospiraceae, Muribaculaceae, and Lactobacillaceae after a high-throughput pyrosequencing of 16S rRNA to observe the changes of related gut microbial composition in db/db mice. These findings proved that SG3 could protect against NAFLD in T2DM by improving IR, oxidative stress, inflammation through regulating insulin signaling and inhibiting CYP2E1/NLRP3 pathways, and remodeling the mouse gut microbiome. It is suggested that SG3 could be considered as a new functional additive for a healthy diet.

Gut Microbiota, Glucose, Lipid, and Water-Electrolyte Metabolism in Children With Nonalcoholic Fatty Liver Disease

There is evidence that nonalcoholic fatty liver disease (NAFLD) is affected by gut microbiota, glucose, and lipid. However, the function of water-electrolyte metabolism remains undefined in children with NAFLD. Therefore, the aim of this case-control study was to better understand these interactions. The sample consisted of 75 children, aged between 7 and 16, of whom 25 had nonalcoholic fatty liver (NAFL), 25 had nonalcoholic steatohepatitis (NASH), and 25 were obese and without NAFLD. These groups were matched by age, sex, and body mass index. Data were collected between June, 2019 and December, 2019 at the Hunan Children’s Hospital, in China. Microbiome composition in fecal samples was assessed using 16S ribosomal RNA amplicon sequencing. In the clinical indices, 12 glucose and lipid metabolism indices were included, and six water-electrolyte metabolism indices were included. The results indicated that microbiomes of NAFLD children had lower alpha diversity but higher beta diversity index than the other two groups. Specifically, anti-inflammatory and probiotics abundance (e.g., Faecalibacterium, Akkermansia, and Bifidobacterium_adolescentis) was significantly decreased in NAFLD, whereas the abundance of harmful bacteria (e.g., Staphylococcaceae) was increased. Moreover, the abundance of butyrate-producing bacteria (e.g., Faecalibacterium, Roseburia_inulinivorans, Roseburia_intestinalis, and Coprococcus_comes) was significantly decreased in NASH. The abundance of these bacteria were associated with glucose, lipid, and water-electrolyte metabolism (e.g., glucose, triglyceride, cholesterol, inorganic salt, total body water, etc.), implying that the NAFLD and its severity were associated with glucose, lipid, and water-electrolyte metabolism dysbiosis. Therefore, these findings suggest that the gut microbiome, especially butyrate-producing bacteria, play an important role in the development of NAFLD in children.

Probiotic yogurt blunts the increase of blood pressure in spontaneously hypertensive rats via remodeling of the gut microbiota

Dietary intake of probiotic yogurt, which has beneficial effects on intestinal microecology, is associated with a lower incidence of hypertension. Recent studies have shown that the gut microbiota plays a vital role in the development of hypertension. However, the impact of the gut microbiota in the antihypertensive effect of probiotic yogurt remains unclear. Here, we evaluated the impact of the gut microbiota in the antihypertensive effect of probiotic yogurt in spontaneously hypertensive rats (SHR). SHR were treated with probiotic yogurt (0.2 mL per 100 g body weight) (SHR-Y group) for seven weeks and compared with whole milk-treated (0.2 mL per 100 g body weight) SHR (SHR group) and with normotensive Wistar-Kyoto rats (WKY group). The blood pressure and heart function of the rats in the WKY, SHR, and SHR-Y groups were measured. Fecal microbiota was assessed by 16S ribosomal RNA (16S rRNA) gene sequencing. To investigate whether probiotic yogurt prevents hypertension in spontaneously hypertensive rats through the gut microbiota, we co-housed SHR rats (SHR^COH) with SHR-Y rats (SHR^COH-Y), thus allowing the transfer of microbiota via coprophagy. Compared with whole milk, supplementation of probiotic yogurt significantly reduced the blood pressure, heart rate (HR), and cardiac function. We found that the probiotic yogurt modified the gut microbiota populations and increased the alpha diversity. Gut microbiota remodeling by co-housing partly rescued the increase of blood pressure and impaired the cardiac function of SHR rats. Moreover, probiotic yogurt modulated the gut microbiota in mice by increasing the abundance of short-chain fatty acid (SCFA)-producing bacteria and SCFA levels (acetic acid, propionic acid, butyric acid, and valeic acid) in the feces. Together, the presented data revealed that probiotic yogurt exhibited antihypertensive effects in SHR rats via remodeling of the gut microbiota.

Targeting Gut–Liver Axis for Treatment of Liver Fibrosis and Portal Hypertension

Antifibrotic therapies for the treatment of liver fibrosis represent an unconquered area of drug development. The significant involvement of the gut microbiota as a driving force in a multitude of liver disease, be it pathogenesis or fibrotic progression, suggest that targeting the gut–liver axis, relevant signaling pathways, and/or manipulation of the gut’s commensal microbial composition and its metabolites may offer opportunities for biomarker discovery, novel therapies and personalized medicine development. Here, we review potential links between bacterial translocation and deficits of host-microbiome compartmentalization and liver fibrosis that occur in settings of advanced chronic liver disease. We discuss established and emerging therapeutic strategies, translated from our current knowledge of the gut–liver axis, targeted at restoring intestinal eubiosis, ameliorating hepatic fibrosis and rising portal hypertension that characterize and define the course of decompensated cirrhosis.

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

BACKGROUND & AIMS

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

METHOD

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

RESULTS

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

CONCLUSIONS

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

Intestinal Microbiota and Liver Diseases: Insights into Therapeutic Use of Traditional Chinese Medicine

Liver disease is a leading cause of global morbidity and mortality, for which inflammation, alcohol use, lipid metabolic disorders, disturbance to bile acid metabolism, and endotoxins are common risk factors. Traditional Chinese Medicine (TCM) with its "holistic approach" is widely used throughout the world as a complementary, alternative therapy, due to its clinical efficacy and reduced side effects compared with conventional medicines. However, due to a lack of reliable scientific evidence, the role of TCM in the prevention and treatment of liver disease remains unclear. Over recent years, with the rapid development of high-throughput sequencing, 16S rRNA detection, and bioinformatics methodology, it has been gradually recognized that the regulation of intestinal microbiota by TCM can play a substantial role in the treatment of liver disease. To better understand how TCM regulates the intestinal microbiota and suppresses liver disease, we have reviewed and analyzed the results of existing studies and summarized the relationship and risk factors between intestinal microbiota and liver disease. The present review summarizes the related mechanisms by which TCM affects the composition and metabolites of the intestinal microbiome.

Skeletal Muscle Dysfunction in the Development and Progression of Nonalcoholic Fatty Liver Disease

The association between the pathogenesis and natural course of nonalcoholic fatty liver disease (NAFLD) and skeletal muscle dysfunction is increasingly recognized. These obesity-associated disorders originate primarily from sustained caloric excess, gradually disrupting cellular and molecular mechanisms of the adipose-muscle-liver axis resulting in end-stage tissue injury exemplified by cirrhosis and sarcopenia. These major clinical phenotypes develop through complex organ-tissue interactions from the earliest stages of NAFLD. While the role of adipose tissue expansion and remodeling is well established in the development of NAFLD, less is known about the specific interplay between skeletal muscle and the liver in this process. Here, the relationship between skeletal muscle and liver in various stages of NAFLD progression is reviewed. Current knowledge of the pathophysiology is summarized with the goal of better understanding the natural history, risk stratification, and management of NAFLD.

The Gut Barrier, Intestinal Microbiota, and Liver Disease: Molecular Mechanisms and Strategies to Manage

Liver disease encompasses pathologies as non-alcoholic fatty liver disease, non-alcoholic steatohepatitis, alcohol liver disease, hepatocellular carcinoma, viral hepatitis, and autoimmune hepatitis. Nowadays, underlying mechanisms associating gut permeability and liver disease development are not well understood, although evidence points to the involvement of intestinal microbiota and their metabolites. Animal studies have shown alterations in Toll-like receptor signaling related to the leaky gut syndrome by the action of bacterial lipopolysaccharide. In humans, modifications of the intestinal microbiota in intestinal permeability have also been related to liver disease. Some of these changes were observed in bacterial species belonging Roseburia, Streptococcus, and Rothia. Currently, numerous strategies to treat liver disease are being assessed. This review summarizes and discusses studies addressed to determine mechanisms associated with the microbiota able to alter the intestinal barrier complementing the progress and advancement of liver disease, as well as the main strategies under development to manage these pathologies. We highlight those approaches that have shown improvement in intestinal microbiota and barrier function, namely lifestyle changes (diet and physical activity) and probiotics intervention. Nevertheless, knowledge about how such modifications are beneficial is still limited and specific mechanisms involved are not clear. Thus, further in-vitro, animal, and human studies are needed.

Protective Effect of Probiotics against Esophagogastric Variceal Rebleeding in Patients with Liver Cirrhosis after Endoscopic Therapy

BACKGROUND Probiotic therapy has been shown to be beneficial against some liver diseases. However, there is still uncertainty regarding the clinical efficacy of probiotics for the treatment of variceal rebleeding. This research explored the efficacy of probiotics in variceal rebleeding. MATERIAL AND METHODS This was a retrospective study of 704 consecutive patients with liver cirrhosis who recovered from esophagogastric variceal bleeding after endoscopic treatment. Patients were subdivided into a probiotics cohort (n=214) and a non-probiotics cohort (n=490) based on the cumulative defined daily dose (cDDD) of probiotics received during follow-up. Propensity score matching was utilized to obtain a relatively balanced cohort of 200 patients per group for the analysis. Patients were monitored for rebleeding during the one-year follow-up. RESULTS Multivariate Cox regression analysis revealed that probiotic therapy (≥28cDDD) was an independent protector against rebleeding (AHR=0.623; 95% CI=0.488-0.795; P<0.001). After propensity score matching, Kaplan-Meier analysis revealed that the rebleeding rate was higher in the non-probiotics cohort (n=200) than in the probiotics cohort (n=200) (56.0% vs. 44.0%, P=0.002). The incidence of rebleeding decreased with increased probiotic dosage (56.0%, 48.5%, 43.3%, and 38.1% in <28 cDDD, 28-60 cDDD, 61-90 cDDD, and >90 cDDD groups, respectively; P=0.011). The median rebleeding interval in the probiotics cohort (n=95) was significantly longer than that in the non-probiotics cohort (n=261) (147.0 vs. 91.0 days; P<0.001). CONCLUSIONS Adjuvant probiotic therapy significantly reduced the incidence of variceal rebleeding and delayed rebleeding after endotherapy in patients with cirrhosis.

Nonalcoholic fatty liver disease and portal hypertension

Nonalcoholic fatty liver disease (NAFLD) is a substantial and growing problem worldwide and has become the second most common indication for liver transplantation as it may progress to cirrhosis and develop complications from portal hypertension primarily caused by advanced fibrosis and erratic tissue remodeling. However, elevated portal venous pressure has also been detected in experimental models of fatty liver and in human NAFLD when fibrosis is far less advanced and cirrhosis is absent. Early increases in intrahepatic vascular resistance may contribute to the progression of liver disease. Specific pathophenotypes linked to the development of portal hypertension in NAFLD include hepatocellular lipid accumulation and ballooning injury, capillarization of liver sinusoidal endothelial cells, enhanced contractility of hepatic stellate cells, activation of Kupffer cells and pro-inflammatory pathways, adhesion and entrapment of recruited leukocytes, microthrombosis, angiogenesis and perisinusoidal fibrosis. These pathological events are amplified in NAFLD by concomitant visceral obesity, insulin resistance, type 2 diabetes and dysbiosis, promoting aberrant interactions with adipose tissue, skeletal muscle and gut microbiota. Measurement of the hepatic venous pressure gradient by retrograde insertion of a balloon-tipped central vein catheter is the current reference method for predicting outcomes of cirrhosis associated with clinically significant portal hypertension and guiding interventions. This invasive technique is rarely considered in the absence of cirrhosis where currently available clinical, imaging and laboratory correlates of portal hypertension may not reflect early changes in liver hemodynamics. Availability of less invasive but sufficiently sensitive methods for the assessment of portal venous pressure in NAFLD remains therefore an unmet need. Recent efforts to develop new biomarkers and endoscopy-based approaches such as endoscopic ultrasound-guided measurement of portal pressure gradient may help achieve this goal. In addition, cellular and molecular targets are being identified to guide emerging therapies in the prevention and management of portal hypertension.

Consumption of a high energy density diet triggers microbiota dysbiosis, hepatic lipidosis, and microglia activation in the nucleus of the solitary tract in rats

Introduction

Obesity is a multifactorial chronic inflammatory disease. Consumption of high energy density (HED) diets is associated with hyperphagia, increased body weight and body fat accumulation, and obesity. Our lab has previously shown that short-term (4 weeks) consumption of a HED diet triggers gut microbiota dysbiosis, gut inflammation, and reorganization of the gut-brain vagal communication.

Objetives

The aim of this study was to investigate the effect of long-term (6 months) consumption of HED diet on body composition, gut microbiome, hepatocellular lipidosis, microglia activation in the nucleus of the solitary tract, and systemic inflammation.

Methods

Male Sprague–Dawley rats were fed a low energy density (LED) diet for 2 weeks and then switched to a HED diet for 26 weeks. Twenty-four-hour food intake, body weight, and body composition were measured twice a week. Blood serum and fecal samples were collected at baseline, 1, 4, 8, and 26 weeks after introduction of the HED diet. Serum samples were used to measure insulin, leptin, and inflammatory cytokines using Enzyme-linked Immunosorbent Assay. Fecal samples were assessed for 16 S rRNA genome sequencing.

Results

HED diet induced microbiota dysbiosis within a week of introducing the diet. In addition, there was significant microglia activation in the intermediate NTS and marked hepatic lipidosis after 4 weeks of HED diet. We further observed changes in the serum cytokine profile after 26 weeks of HED feeding.

Conclusions

These data suggest that microbiota dysbiosis is the first response of the organism to HED diets, followed by increased liver fat accumulation, microglia activation in the brain, and circulating levels of inflammatory markers. To our knowledge, this is the first study to present longitudinal and cross-sectional results on effect of long-term consumption of HED diets on all these parameters in a single cohort of animals.

Is the gut microbiota dysbiotic in patients with classical homocystinuria?

Classical homocystinuria (HCU) is characterized by increased plasma levels of total homocysteine (tHcy) and methionine (Met). Treatment may involve supplementation of B vitamins and essential amino acids, as well as restricted Met intake. Dysbiosis has been described in some inborn errors of metabolism, but has not been investigated in HCU. The aim of this study was to investigate the gut microbiota of HCU patients on treatment. Six unrelated HCU patients (males = 5, median age = 25.5 years) and six age-and-sex-matched healthy controls (males = 5, median age = 24.5 years) had their fecal microbiota characterized through partial 16S rRNA gene sequencing. Fecal pH, a 3-day dietary record, medical history, and current medications were recorded for both groups. All patients were nonresponsive to pyridoxine and were on a Met-restricted diet and presented with high tHcy. Oral supplementation of folate (n = 6) and pyridoxine (n = 5), oral intake of betaine (n = 4), and IM vitamin B12 supplementation (n = 4), were reported only in the HCU group. Patients had decreased daily intake of fat, cholesterol, vitamin D, and selenium compared to controls (p < 0.05). There was no difference in alpha and beta diversity between the groups. HCU patients had overrepresentation of the Eubacterium coprostanoligenes group and underrepresentation of the Alistipes, Family XIII UCG-001, and Parabacteroidetes genera. HCU patients and controls had similar gut microbiota diversity, despite differential abundance of some bacterial genera. Diet, betaine, vitamin B supplementation, and host genetics may contribute to these differences in microbial ecology.

A Microbial Signature Identifies Advanced Fibrosis in Patients with Chronic Liver Disease Mainly Due to NAFLD

The presence of advanced fibrosis is an important measure of the severity of chronic liver disease. Prior works that have examined the gut microbiome as a novel biomarker for advanced fibrosis have only examined patients with nonalcoholic fatty liver disease. Therefore, our goal was to examine the gut microbiome across varying etiologies of liver disease to create a predictive model for liver fibrosis based upon a microbial signature. Stool samples were obtained from patients with chronic liver disease (n = 50) undergoing FibroScan (ultrasound elastography) at the VA Greater Los Angeles Healthcare System. Healthy control patients (n = 25) were also recruited as a reference population. Fecal samples underwent 16S ribosomal RNA sequencing. Using differentially abundant microbes, a random forest classifier model was created to distinguish advanced fibrosis from mild/moderate fibrosis. The findings were then validated in a separate cohort of chronic liver disease patients (n = 37). Etiologies for liver disease included non-alcoholic liver disease (58.0%), hepatitis C (26.0%), hepatitis B (10.0%), and alcohol (6.0%). Microbiome composition was distinct in liver patients with advanced fibrosis compared to those with minimal fibrosis and healthy controls (p = 0.003). In multivariate negative binomial modeling, 26 bacterial taxa were differentially abundant in patients with advanced fibrosis as compared to those with minimal/moderate fibrosis (q-value < 0.05). A random forests classifier based on these taxa had an AUROC of 0.90 to predict advanced fibrosis. Prevotella copri, which was enriched in patients with advanced fibrosis, was the most strongly predictive microbe in the classifier. The classifier had an AUROC of 0.82 for advanced fibrosis in the validation cohort and Prevotella copri remained the strongest predictive microbe for advanced fibrosis. There is a distinct microbial signature for patients with advanced fibrosis independent of liver disease etiology and other comorbidities. These results suggest that microbial profiles can be used as a non-invasive marker for advanced fibrosis and support the hypothesis that microbes and their metabolites contribute to hepatic fibrosis.

Intestinal permeability in the pathogenesis of liver damage: From non-alcoholic fatty liver disease to liver transplantation

The intimate connection and the strict mutual cooperation between the gut and the liver realizes a functional entity called gut-liver axis. The integrity of intestinal barrier is crucial for the maintenance of liver homeostasis. In this mutual relationship, the liver acts as a second firewall towards potentially harmful substances translocated from the gut, and is, in turn, is implicated in the regulation of the barrier. Increasing evidence has highlighted the relevance of increased intestinal permeability and consequent bacterial translocation in the development of liver damage. In particular, in patients with non-alcoholic fatty liver disease recent hypotheses are considering intestinal permeability impairment, diet and gut dysbiosis as the primary pathogenic trigger. In advanced liver disease, intestinal permeability is enhanced by portal hypertension. The clinical consequence is an increased bacterial translocation that further worsens liver damage. Furthermore, this pathogenic mechanism is implicated in most of liver cirrhosis complications, such as spontaneous bacterial peritonitis, hepatorenal syndrome, portal vein thrombosis, hepatic encephalopathy, and hepatocellular carcinoma. After liver transplantation, the decrease in portal pressure should determine beneficial effects on the gut-liver axis, although are incompletely understood data on the modifications of the intestinal permeability and gut microbiota composition are still lacking. How the modulation of the intestinal permeability could prevent the initiation and progression of liver disease is still an uncovered area, which deserves further attention.

Role and effective therapeutic target of gut microbiota in NAFLD/NASH

Non-alcoholic fatty liver disease (NAFLD), the most prevalent chronic liver disease in the world, is affected by numerous extrinsic and intrinsic factors, including lifestyle, environment, diet, genetic susceptibility, metabolic syndrome and gut microbiota. Accumulating evidence has proven that gut dysbiosis is significantly associated with the development and progression of NAFLD, and several highly variable species in gut microbiota have been identified. The gut microbiota contributes to NAFLD by abnormal regulation of the liver-gut axis, gut microbial components and microbial metabolites, and affects the secretion of bile acids. Due to the key role of the gut microbiota in NAFLD, it has been regarded as a potential target for the pharmacological and clinical treatment of NAFLD. The present review provides a systematic summary of the characterization of gut microbiota and the significant association between the gut microbiota and NAFLD. The possible mechanisms of how the gut microbiota is involved in promoting the development and progression of NAFLD were also discussed. In addition, the potential therapeutic methods for NAFLD based on the gut microbiota were summarized.