Bacteroides in colonic mucosa-associated microbiota affects the development of minimal hepatic encephalopathy in patients with cirrhosis

Distribution of gut microbiota across intestinal segments and their impact on human physiological and pathological processes

In recent years, advancements in metagenomics, metabolomics, and single-cell sequencing have enhanced our understanding of the intricate relationships between gut microbiota and their hosts. Gut microbiota colonize humans from birth, with their initial composition significantly influenced by the mode of delivery and feeding method. During the transition from infancy to early childhood, exposure to a diverse diet and the maturation of the immune system lead to the gradual stabilization of gut microbiota's composition and distribution. Numerous studies have demonstrated that gut microbiota can influence a wide range of physiological functions and pathological processes by interacting with various tissues and organs through the gut-organ axis. Different intestinal segments exhibit unique physical and chemical conditions, which leads to the formation of vertical gradients along the intestinal tract: aerobes and facultative aerobes mainly live in the small intestine and anaerobic bacteria mainly live in the large intestine, and horizontal gradients: mucosa-associated microbiota and lumen-associated microbiota. In this review, we systematically summarize the distribution characteristics of gut microbiota across six intestinal segments: duodenum, jejunum, ileum, cecum, colon, and rectum. We also draw a conclusion that gut microbiota distributed in different intestinal segments affect the progression of different diseases. We hope to elucidate the role of microbiota at specific anatomic sites within the gut in precisely regulating the processes of particular diseases, thereby providing a solid foundation for developing novel diagnostic and therapeutic strategies for related diseases.

Isolation of mucosa-associated microbiota dysbiosis in the ascending colon in hepatitis C virus post-sustained virologic response cirrhotic patients

Background

Achieving sustained virologic response (SVR) in patients infected with hepatitis C virus (HCV) reduces all-cause mortality. However, the mechanisms and risk factors for liver fibrosis and portal hypertension post-SVR remain incompletely understood. In the gut-liver axis, mucosa-associated microbiota (MAM) substantially influence immune and metabolic functions, displaying spatial heterogeneity at the anatomical intestinal site. We analyzed MAM composition and function to isolate the locoregional MAM involved in chronic liver disease progression in HCV post-SVR patients.

Methods

We collected MAM samples from three intestinal sites (terminal ileum, ascending colon, and sigmoid colon) via brushing during colonoscopy in 23 HCV post-SVR patients and 25 individuals without liver disease (controls). The 16S rRNA of bacterial DNA in specimens collected with a brush and in feces was sequenced. The molecular expression of intestinal tissues and hepatic tissues were evaluated by quantitative real-time PCR.

Results

In the post-SVR group, the microbial β-diversity of MAM, especially in the ascending colon, differed from the control group and was associated with liver fibrosis progression. In PICRUSt analysis, MAM in the ascending colon in the liver cirrhosis (LC) group showed compromised functions associated with the intestinal barrier and bile acid production, and FGF19 expression was markedly decreased in the terminal ileum biopsy tissue in the LC group. At the genus level, six short-chain fatty acid (SCFA)-producing bacterial genera, Blautia, Alistipes, Roseburia, Agathobaculum, Dorea, and Pseudoflavonifractor were reduced in the ascending colon of post-SVR LC patients.

Conclusion

In patients of HCV post-SVR, we identified the association between the degree of liver fibrosis and dysbiosis of mucosa-associated SCFA-producing bacterial genera that may be related to intestinal barrier and bile acid production in the ascending colon.

Prenatal exposure to hexafluoropropylene oxide trimer acid (HFPO-TA) disrupts the maternal gut microbiome and fecal metabolome homeostasis

Initially considered a "safe" substitute for perfluorooctanoic acid (PFOA), hexafluoropropylene oxide trimer acid (HFPO-TA) has been extensively used in the production of fluoropolymers for several years, leading to its environmental ubiquity and subsequent discovery of its significant bio-accumulative properties and toxicological effects. However, the specific impact of HFPO-TA on females, particularly those who are pregnant, remains unclear. In the present study, pregnant mice were exposed to 0.63 mg/kg/day HFPO-TA from gestational day (GD) 2 to GD 18. We then determined the potential effects of exposure on gut microbiota and fecal metabolites at GD 12 (mid-pregnancy) and GD 18 (late pregnancy). Our results revealed that, in addition to liver damage, HFPO-TA exposure during the specified window altered the structure and function of cecal gut microbiota. Notably, these changes showed the opposite trends at GD 12 and GD 18. Specifically, at GD 12, HFPO-TA exposure primarily resulted in the down-regulation of relative abundances within genera from the Bacteroidetes and Proteobacteria phyla, as well as associated Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways. With extended exposure time, the down-regulated genera within Proteobacteria became significantly up-regulated, accompanied by corresponding up-regulation of human disease- and inflammation-associated pathways, suggesting that HFPO-TA exposure can induce intestinal inflammation and elevate the risk of infection during late pregnancy. Pearson correlation analysis revealed that disturbances in the gut microbiota were accompanied by abnormal fecal metabolite. Additionally, alterations in hormones related to the steroid hormone biosynthesis pathway at both sacrifice time indicated that HFPO-TA exposure might change the steroid hormone level of pregnant mice, but need further study. In conclusion, this study provides new insights into the mechanisms underlying HFPO-TA-induced adverse effects and increases awareness of potential persistent health risks to pregnant females.

From-Toilet-to-Freezer: A Review on Requirements for an Automatic Protocol to Collect and Store Human Fecal Samples for Research Purposes

The composition, viability and metabolic functionality of intestinal microbiota play an important role in human health and disease. Studies on intestinal microbiota are often based on fecal samples, because these can be sampled in a non-invasive way, although procedures for sampling, processing and storage vary. This review presents factors to consider when developing an automated protocol for sampling, processing and storing fecal samples: donor inclusion criteria, urine-feces separation in smart toilets, homogenization, aliquoting, usage or type of buffer to dissolve and store fecal material, temperature and time for processing and storage and quality control. The lack of standardization and low-throughput of state-of-the-art fecal collection procedures promote a more automated protocol. Based on this review, an automated protocol is proposed. Fecal samples should be collected and immediately processed under anaerobic conditions at either room temperature (RT) for a maximum of 4 h or at 4 °C for no more than 24 h. Upon homogenization, preferably in the absence of added solvent to allow addition of a buffer of choice at a later stage, aliquots obtained should be stored at either -20 °C for up to a few months or -80 °C for a longer period-up to 2 years. Protocols for quality control should characterize microbial composition and viability as well as metabolic functionality.

Clinical study of probiotics combined with lactulose for minimal hepatic encephalopathy treatment

OBJECTIVE

This study aimed to investigate the clinical effect of probiotics combined with lactulose for minimal hepatic encephalopathy (MHE) treatment.

METHODS

A total of 88 patients with MHE were randomly divided into the control ( n  = 44) and combined groups ( n  = 44). The control group was treated with lactulose, while the combined group was treated with probiotics and lactulose. Serum ammonia, liver function [alanine aminotransferase (ALT) and aspartate transaminase (AST)], intestinal mucosal barrier markers [fatty acid-binding protein 2 (FABP2) and advanced glycation end-products (AGEs)] and number connection test A (NCT-A) and digit symbol test (DST) scores were tested and compared between the two groups.

RESULTS

The post-treatment in the control and combined groups shows decreased serum ammonia levels, ALT and AST levels, FABP2 and AGEs levels and NCT-A score and increased DST score compared with pre-treatment, with a significant difference ( P  < 0.05). Post-treatment, the serum ammonia level, ALT and AST levels, FABP2 and AGEs levels, NCT-A score decreased and DST score increased in the combined group compared with the control group, with a significant difference ( P  < 0.05).

CONCLUSION

Probiotics can promote lactulose in MHE treatment.

Modulation of duodenal and jejunal microbiota by rifaximin in mice with CCl4-induced liver fibrosis

BACKGROUND

Rifaximin is a poorly absorbed broad-spectrum antibiotic used for hepatic encephalopathy. Although increased Lactobacillaceae and decreased Bacteroidetes abundance are characteristic of hepatic encephalopathy, rifaximin does not dramatically alter the stool microbiota. As the antimicrobial effect of rifaximin increases by micellization with bile acids, we hypothesized that rifaximin alters the microbiota in the duodenum and jejunum, where the levels of bile acids are abundant.

METHODS AND RESULTS

Eight-week-old BALB/c mice were injected with carbon tetrachloride (CCl₄) intraperitoneally for 12 weeks to induce liver fibrosis. The mice were grouped into the control (n = 9), CCl₄ (n = 13), and rifaximin group in which mice were treated with rifaximin for two weeks after CCl₄ administration (n = 13). We analyzed the microbiota of the duodenum, jejunum, ileum, cecum, and stool using 16S ribosomal RNA gene analysis. The content of Lactobacillaceae, the most abundant bacterial family in the duodenum and small intestine, increased in the CCl₄ group, especially in the jejunum (median 67.0% vs 87.8%, p = 0.03). Rifaximin significantly decreased Lactobacillaceae content in the duodenum (median 79.4% vs 19.0%, p = 0.006) and jejunum (median 87.8% vs 61.3%, p = 0.03), but not in the ileum, cecum, and stool. Bacteroidetes abundance tended to decrease on CCl₄ administration and increased following rifaximin treatment in the duodenum and jejunum. S24_7, the most abundant family in Bacteroidetes, demonstrated a significant inverse correlation with Lactobacillaceae (duodenum, r = - 0.61, p < 0.001; jejunum, r = - 0.72, p < 0.001). In the ileum, cecum, and stool, the effect of rifaximin on the microbiota was minimal, with changes within the same phylum. The percentage of bacterial families, such as Lactobacillaceae and S24_7 in the duodenum and small intestine, did not correlate with that in the stool.

CONCLUSIONS

The abundance of Lactobacillaceae increased in the jejunum of mice with CCl₄-induced liver fibrosis, while rifaximin significantly reduced it in the duodenum and jejunum. Thus, rifaximin possibly exerts its effect by altering the duodenal and jejunal microbiota. Furthermore, changes in the duodenal and small intestinal microbiota were not associated with that of stool, suggesting that the analysis of stool microbiota is insufficient to evaluate upper intestinal microbiota.

Comparison of the effects of probiotics, rifaximin, and lactulose in the treatment of minimal hepatic encephalopathy and gut microbiota

Background

Minimal hepatic encephalopathy (MHE) is an early stage in the pathogenesis of hepatic encephalopathy. Intestinal microbiota is involved in the pathogenesis of hepatic encephalopathy and has become an important therapeutic target. Since there is no unified treatment principle for MHE, this study was conducted to determine the safety and efficacy of different intestinal microecological modulators in the treatment of MHE, and to explore the potential mechanism through intestinal microbiota analysis.

Methods

Patients with liver cirrhosis were screened for MHE using psychometric hepatic encephalopathy score test. Patients diagnosed with MHE were enrolled and received probiotics, rifaximin, or lactulose for 4 weeks. Adverse events were recorded. The psychometric hepatic encephalopathy score test was performed after treatment. Samples of blood and stool were collected at entry and 4 weeks. Blood samples were analyzed to assess blood ammonia, liver, kidney, and hemostatic functions. Stool microbiota were sequenced to confirm changes in microbial composition.

Results

Of 323 patients with liver cirrhosis, 74 patients were diagnosed with MHE. In all, 54 patients were enrolled and 52 who agree to follow-up were included in analysis. The recovery rates of MHE patients received probiotics, rifaximin, and lactulose were 58.8% (20/34), 45.5% (5/11), and 57.1% (4/7), respectively. Probiotics and rifaximin improved liver function in MHE patients to a certain extent. Taxonomic compositions of gut microbiota in MHE patients were distinct from healthy people before treatment; the differences were significantly reduced after treatment, and the gut microbiota gradually resembled the structure of healthy individuals. We found that the relative abundance of specific taxa associated with anti-inflammatory and good cognitive functions was increased in MHE patients after treatment. Accordingly, metabolic pathways in MHE patients were altered before and after treatment. Downregulated pathways after probiotics treatment included glycometabolism and degradation of aromatic compounds. After lactulose treatment, degradation pathways of arginine and ornithine showed a downward trend.

Conclusion

Probiotics, rifaximin, and lactulose are safe and effective in the treatment of MHE, and improve the composition of gut microbiota to some extent.

Comparison of whole goat milk and its major fractions regarding the modulation of gut microbiota

BACKGROUND

Goat milk can be important for human nutrition because of its nutritional value, which may be attributed to its richness in protein, lactose, fat, and other bioactive components. This study compared the diversity and composition of gut microbiota in response to whole goat milk and its major fractions (milk fat, casein, milk whey, whey protein, and whey supernatant). Goat milk, its major fractions, and sterile distilled water (for the control group) were administered to mice intragastrically, and gut microbiota were compared in these groups using metagenomic analysis.

RESULTS

We observed distinct patterns of gut microbiota from different diet groups. The sample distance heatmap showed that, compared with other goat milk fractions, gut microbiota in the casein group was more similar to that in the whole goat-milk group. The relative abundance of the genus Lactobacillus increased significantly after whole goat-milk treatment; the milk whey fraction increased the abundance of Blautia; milk fat and milk whey related fractions treatment promoted the population of Bacteroides. The network analysis showed that genera Lactobacillus and Lactococcus were negatively associated with Helicobacter and Acinetobacter, respectively.

CONCLUSION

Fractions of goat milk could contain different gut microbiota from whole goat milk. Consumption of certain goat milk fractions could increase the ingestion of beneficial bacteria and inhibit the growth of some pathogenic bacteria. Our results could provide the basis for the research into and development of goat-milk based functional foods. © 2021 Society of Chemical Industry.

The impact of proton pump inhibitors in liver diseases and the effects on the liver

In this systematic and comprehensive overview, we aimed to evaluate the impact of proton pump inhibitors (PPIs) on chronic liver diseases, especially on cirrhosis. A manual and comprehensive search of the PubMed database was conducted to obtain relevant literatures. PPIs altered the composition and function of the intestinal microflora and might lead to small intestinal bacterial overgrowth and bacterial translocation, which were associated with adverse effects in liver diseases. They might increase the risk of hepatic encephalopathy, spontaneous bacterial peritonitis, infections, and are related to an increased mortality in cirrhosis. PPIs might lead to an increased risk of hepatocellular carcinoma, although the mechanism is unknown, and the results are controversial. PPIs also had an impact on the direct-acting antiviral regimen in patients with chronic hepatitis C. They were associated with an increased risk of liver abscess and increased mortality. Additionally, PPIs might lead to metabolic risk events, such as liver steatosis and weight gain. PPIs are associated with several adverse outcomes in liver diseases. Cautious use of PPIs is recommended and clinicians should be aware of the indications for their use in patients with liver diseases.

Lactic acid bacteria alleviate liver damage caused by perfluorooctanoic acid exposure via antioxidant capacity, biosorption capacity and gut microbiota regulation

Perfluorooctanoic acid (PFOA) is an environmental pollutant that has multiple toxic effects. Although some medicines and functional food ingredients are currently being used to alleviate the biological toxicity effects caused by PFOA, these candidates all show potential side effects and cannot prevent the accumulation of PFOA in the body, making them unable to be used as a daily dietary supplement to relieve the toxic effects of PFOA. However, new research has shown that lactic acid bacteria (LAB) can alleviate toxicity caused by exposure to foreign substances. In this study, multiple strains of LAB with different adsorption capacities or antioxidant capacities were used to analyse their mitigation effects of on liver damage caused by PFOA exposure. The results showed that the adsorption capacity and antioxidant capacity of LAB could alleviate the liver toxicity of PFOA to a certain extent. Moreover, treatment with some strains of LAB was able to recover the gut microbiota dysbiosis caused by PFOA exposure, such as by increasing the relative abundances of Patescibacteria, Proteobacteria, Akkermansia and Alistipes or decreasing the abundances of Bacteroides and Blautia. In addition, a strain with neither outstanding antioxidant capacity nor adsorption capacity also reversed the decline in short-chain fatty acid levels caused by PFOA exposure. The ability of these strains to relieve gut microbiota dysbiosis partly explains the inconsistency between the capacity for antioxidant or PFOA adsorption and the ability of the strains to alleviate PFOA toxicity. The results indicate that the PFOA adsorption capacity and antioxidant capacity of LAB may be involved in the alleviation of PFOA liver toxicity. In addition, LAB could also alleviate liver damage caused by PFOA by adjusting the gut microbiota and short-chain fatty acid content. Therefore, some strains of LAB can be used as a potentially safe dietary supplement to relieve PFOA-induced liver damage.

Proposal of Stroop test cut-off values as screening for neuropsychological impairments in cirrhosis: A Japanese multicenter study

AIM

Despite its relevant clinical impact and high prevalence, covert hepatic encephalopathy (HE) still remains underdiagnosed. As patients with liver cirrhosis tend to be older in Japan, more suitable tests for the elderly and cut-off values based on this attribute are needed. Recently, a Stroop test has been developed and validated for the screening and diagnosis of covert HE in the United States. The present study aims to establish the cut-off values of the Stroop test to screen covert HE.

METHODS

This study was a prospective multicenter cross-sectional endeavor. We undertook a survey of 311 cirrhotic patients, administering the number connection test (NCT)-A and -B and the Stroop-off and -on test.

RESULTS

We determined the cut-off values of Stroop test results for cirrhotic patients in a variety of age ranges. The cut-off value of the Stroop test was strongly correlated with age. There was a significant correlation between the results of NCT-B and age, and Stroop-on test results showed a correlation with serum albumin (Alb) levels. Serum Alb ≤3.2 g/dl could have the potential to be an objective biomarker of covert HE. In addition, stepwise logistic regression analysis revealed a relationship between the results of the Stroop-on test and plasma ammonia levels.

CONCLUSIONS

We established the cut-off values of Stroop test results and confirmed the efficacy of the Stroop test as a simple tool for assessing cognitive alterations. The Stroop test could be suitable as a necessary minimum for the diagnosis of covert HE.

Assessment of the association between dysphagia and sarcopenia among elderly patients with cirrhosis: Usefulness of the finger-ring test

AIM

Sarcopenic dysphagia has become an urgent matter of debate in our aging society. However, little is known about the relationship between sarcopenia and dysphagia in patients with liver cirrhosis. Our aim was to assess sarcopenia and dysphagia among elderly patients with cirrhosis using two easy-to-use screening tests, i.e., the eating assessment tool-10 and the finger-ring test.

METHODS

The eating assessment tool-10, handgrip strength, skeletal muscle mass index, computed tomography, and the finger-ring test were included in our analysis. One hundred patients with cirrhosis and without a history of aspiration pneumonia were divided into the elderly (≥75 years) and non-elderly (<75 years) groups.

RESULTS

In the elderly group, sarcopenia was identified in 56.5% of the patients; of these, 30.4% and 13.0% had eating assessment tool-10 scores of ≥2 and ≥3, respectively. Sarcopenia-related factors correlated significantly with the eating assessment tool-10 scores (p<0.01). Multivariate regression analysis revealed that sarcopenia was significantly associated with dysphagia (p=0.028; odds ratio, 7.27). Among the elderly patients, the calf size of the non-dominant lower limb was less than the finger-ring circumference in 37.0% of the patients. This group had a significantly higher proportion of patients with an eating assessment tool-10 score of ≥2 than those with a greater calf than finger-ring circumference (p<0.01).

CONCLUSIONS

Sarcopenia, rather than the hepatic reserve function, is associated with dysphagia among elderly patients with cirrhosis. The finger-ring test might be useful in screening for dysphagia.

Perfluorooctanoic acid-induced liver injury is potentially associated with gut microbiota dysbiosis

Perfluorooctanoic acid (PFOA), an environmental pollutant, is widely engaged in industrial products and tends to accumulate in the liver. Emerging evidence has suggested that the gut microbiome is a pivotal player in maintaining animal health and can potentially altered by xenobiotic. However, few studies explored whether PFOA-induced liver injury is associated with gut microbiota dysbiosis. In the present study, the effects of subacute and subchronic PFOA exposure on liver and gut microbiota in C57BL/6J mice were investigated. Our findings showed that both subacute and subchronic exposure to PFOA induced the liver inflammation, disrupted antioxidative homeostasis and caused liver histological abnormalities with detectable hepatomegaly, ultimately triggering liver injury. Besides, 16S rRNA sequencing analysis revealed that subacute PFOA exposure caused significant changes in the abundances of intestinal flora known to contribute to liver inflammation and oxidative stress, such as the Dehalobacterium and Bacteroides genera. Exposure to subchronic toxicity mainly induced the decrease in commensal probiotics including Lactobacillus and Bifidobacterium genera, which are potentially beneficial to liver damage, compared with that in the untreated group. They also resulted in disturbed functional capabilities of the microbial communities by a Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt) analysis. Additionally, the levels of short-chain fatty acids (SCFAs), especially butyric acid, were significantly reduced by PFOA administration. Collectively, our observations suggested that liver damage induced by both subacute and subchronic PFOA exposures probably partly related to the gut microbiota dysbiosis and provided a new insight into the role of PFOA in liver injury.

Comparative study of the effect of neuromuscular electrical stimulation and oral administration of branched-chain amino acid on preventing sarcopenia in patients after living-donor liver transplantation: study protocol for an open-label randomized controlled trial

Background

Liver cirrhosis is the irreversible fibrosis of the liver and causes refractory ascites and hepatic encephalopathy, which might not respond to treatment. Living donor liver transplantation (LDLT) is an effective treatment for patients with cirrhosis. However, post-LDLT patients are prone to muscle atrophy and sarcopenia. Therefore, physiotherapy of post-LDLT patients is essential for preventing the progression of sarcopenia. Recently, rehabilitation using neuromuscular electrical stimulation (NMES) has been reported to be useful for preventing the progression of sarcopenia. Similarly, nutrition therapy is essential for post-LDLT patients because these patients frequently experience malnutrition. However, the effects of combined NMES and nutrition therapy on post-LDLT patients remain unknown.

Methods/design

This open-label, randomized, parallel-group study will compare the effects of combined therapy with NMES and branched-chain amino acids (BCAA) with those of NMES alone in patients with decompensated cirrhosis after LDLT. After LDLT, 50 patients with decompensated cirrhosis will be randomly assigned to receive NMES with BCAA or NMES without BCAA. The duration of the intervention will be 3 months. To analyze the change in skeletal muscle mass, InBody 770 body composition and body water analysis and ultrasonography will be performed before LDLT and 4 weeks and 12 weeks post-LDLT. The primary endpoint is changes in the skeletal muscle mass from baseline to 3 months. Important secondary endpoints are the changes in the skeletal muscle mass from baseline to 1 month and changes in the quadriceps strength from baseline to 1 month.

Discussion

The results of this study are expected to provide evidence regarding the effect of NMES combined with BCAA therapy on the skeletal muscle of post-LDLT patients.

Trial registration

Japan Registry of Clinical Research jRCTs071190051. Registered on February 26, 2020.

The Role of Intestinal Bacteria and Gut-Brain Axis in Hepatic Encephalopathy

Hepatic encephalopathy (HE) is a neurological disorder that occurs in patients with liver insufficiency. However, its pathogenesis has not been fully elucidated. Pharmacotherapy is the main therapeutic option for HE. It targets the pathogenesis of HE by reducing ammonia levels, improving neurotransmitter signal transduction, and modulating intestinal microbiota. Compared to healthy individuals, the intestinal microbiota of patients with liver disease is significantly different and is associated with the occurrence of HE. Moreover, intestinal microbiota is closely associated with multiple links in the pathogenesis of HE, including the theory of ammonia intoxication, bile acid circulation, GABA-ergic tone hypothesis, and neuroinflammation, which contribute to cognitive and motor disorders in patients. Restoring the homeostasis of intestinal bacteria or providing specific probiotics has significant effects on neurological disorders in HE. Therefore, this review aims at elucidating the potential microbial mechanisms and metabolic effects in the progression of HE through the gut-brain axis and its potential role as a therapeutic target in HE.