The Intestinal Microbiome and the Liver Transplant Recipient: What We Know and What We Need to Know

Interaction between ischemia-reperfusion injury and intestinal microecology in organ transplantation and its therapeutic prospects

Organ transplantation is a vital intervention for end-stage organ failure; however, ischemia-reperfusion injury is a complication of transplantation, affecting the prognosis and survival of transplant recipients. As a complex ecosystem, recent research has highlighted the role of the intestinal microecology in transplantation, revealing its significant interplay with ischemia-reperfusion injury. This review explores the interaction between ischemia-reperfusion injury and intestinal microecology, with a special focus on how ischemia-reperfusion injury affects intestinal microecology and how these microecological changes contribute to complications after organ transplantation, such as infection and rejection. Based on a comprehensive analysis of current research advances, this study proposes potential strategies to improve transplant outcomes, offering guidance for future research and clinical practice.

Microbiome composition recovery after liver transplantation correlates with initial liver disease severity and antibiotics treatment

Liver transplantation (LT) is crucial for end-stage liver disease, but it is linked to infection risks. Pathobionts, microorganisms potentially harmful under specific conditions, can cause complications posttransplant. Monitoring such pathogens in fecal samples can be challenging and therefore remains underexplored post-LT. This study aimed to analyze the gut microbiome before and after LT, tracking pathobionts and correlating clinical data. The study involved 17 liver transplant recipients, 17 healthy relatives (spouses), and 13 donors. Gut samples collected pretranplantation and posttransplantation underwent bacterial and fungal profiling through DNA sequencing. Quantitative polymerase chain reaction was used to assess microbial load. Statistical analyses included alpha and beta diversity measures, differential abundance analysis, and correlation tests between microbiome and clinical parameters. Microbiome analysis revealed dynamic changes in diversity posttransplant. Notably, high-severity patients showed persistent and greater dysbiosis during the first months post-LT compared with low-severity patients, partly due to an antibiotic treatment pre-LT. The analysis identified a higher proportion of pathogens such as Escherichia coli/Shigella flexneri in high-severity cases posttransplant. Furthermore, butyrate producers including Roseburia intestinalis, Anaerostipes hadrus, and Eubacterium coprostanoligenes were positively correlated with levels of albumin. This study offers valuable insights into post-LT microbiome changes, shedding light on the need for tailored prophylactic treatment post-LT.

Comparative Effectiveness of Perioperative Antibiotic Regimens to Prevent Surgical Site Infections in Pediatric Liver Transplant Recipients

BACKGROUND

Surgical site infections (SSIs) are a common complication in liver transplant (LT) recipients. Lack of pediatric prophylaxis guidelines results in variation in preventative antibiotic regimens.

METHODS

We performed a retrospective observational study of LT recipients <18 years old using a merged data set that included data from the Pediatric Health Information System and the United Network for Organ Sharing between 2006 and 2017. The exposure was defined as the antibiotic(s) received within 24 hours of LT, with 6 categories, ranging from narrow (category 1: cefazolin), to broad). The primary outcome was presence or absence of SSI in the index admission. Mixed-effects logistic regression compared the effectiveness of each category in preventing SSI, relative to category 1.

RESULTS

Of the 2586 LT, 284 (11%) met SSI criteria. The SSI rate was higher in the younger subcohort (16.2%) than in the older (8.6%), necessitating a stratified analysis. Antibiotics from category 5 were most commonly used. In the younger subcohort, the adjusted risk was increased in all categories compared with the reference, most notably in category 3 (odds ratio [OR], 2.58 [95% confidence interval: .69-9.59]) and category 6 (2.76 [.66-11.56]). In the older subcohort, estimated ORs were also increased for each category, most notably in category 4 (2.49 [95% confidence interval: .99-6.27]). None of the ORs suggested benefit from broader-spectrum prophylaxis. Our E-value assessment suggests that it's unlikely there is unmeasured confounding by indication to the degree necessary to revert ORs to protective.

CONCLUSIONS

There was wide variation in antibiotic prophylaxis. Adjusted analyses did not reveal a protective benefit of broader-spectrum prophylaxis in either subcohort, suggesting that narrower regimens may be adequate.

Identification of hub genes and potential inhibitory compounds in the process of liver transplantation through transcriptome sequencing

Liver transplantation (LT) is the best choice for patients with end-stage liver diseases. In order to better understand pathophysiological alterations in LT, we aimed to identify potential hub genes and inhibitory compounds involved in the LT process. Four pairs of peripheral blood mononuclear cell (PBMC) samples of the LT recipients before and after surgery were collected and taken for transcriptome sequencing. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses were performed for the screened differentially expressed genes (DEGs) between pre- and post-operation groups. Common DEGs were obtained from GO and KEGG enriched pathways, followed by protein-protein interaction (PPI) network construction, hub gene identification, module analysis, and structure-based virtual screening process (SBVS). Compared to the pre-operation stage, 4745 genes were down-regulated and 798 up-regulated after LT. GO analysis showed that the DEGs were enriched in ribosome-related translation regulation, and KEGG analysis indicated that infection and immune-related pathways and diseases were largely enriched. A large number of down-regulated DEGs were not only associated with ribosome-related pathways but also with the alterations of epigenetic modifications, in particular ubiquitination. Moreover, through the PPI network of 29 common genes from GO and KEGG-enriched pathways, 7 hub genes were identified, including PTEN, MYC, EIF2S1, EIF4EBP1, HSP90AB1, TP53, and HSPA8, which were mainly involved in the PI3K-AKT signaling pathway. SBVS of the seed molecule PTEN (PDB code: 1D5R) predicted top hits compounds that may serve as potential inhibitors of PTEN, of which the compound ZINC4235331 had the lowest binding affinity of -10 kcal/mol. The significance of screened hub genes and potential inhibitors involved in the process of LT provides novel therapeutic strategies for improving the outcomes of LT recipients during surgery.

Intestinal Bacteremia After Liver Transplantation Is a Risk Factor for Recurrence of Primary Sclerosing Cholangitis

BACKGROUND

Primary sclerosing cholangitis (PSC) is a chronic progressive pathological process, related to inflammatory bowel disease and subsequent bacterial translocation. Liver transplantation (LT) is the only curative therapy, but outcomes are compromised by recurrence of PSC (rPSC). The aim of the study was to investigate a potential link between intestinal bacteremia, fucosyltransferase-2 (FUT2), and rPSC after LT.

METHODS

LT recipients with PSC (n = 81) or without PSC (n = 271) were analyzed for clinical outcomes and positive bacterial blood cultures. A link between bacteremia and the genetic variant of the FUT2 gene was investigated.

RESULTS

The incidence of inflammatory bowel disease was significantly higher in PSC recipients but not associated with rPSC. Bacteremia occurred in 31% of PSC recipients. The incidence of rPSC was 37% and was significantly more common in patients with intestinal bacteremia versus no bacteremia (82% versus 30%; P = 0.003). The nonsecretor polymorphism of the FUT2 gene was identified as a genetic risk factor for both intestinal bacteremia and rPSC. Combined FUT2 genotype and intestinal bacteremia in recipients resulted in the highest risk for rPSC (hazard ratio, 15.3; P < 0.001).

CONCLUSIONS

Thus, in this article, we showed that bacterial translocation is associated with rPSC after LT and related to the FUT2 nonsecretor status.

Longitudinal analysis of transplant candidates with primary sclerosing cholangitis in an Asian liver transplant center

BACKGROUND

Primary sclerosing cholangitis (PSC) is a rare disease in Asia, and few studies have investigated the disease in this ethnicity, particularly in wait-listed patients for liver transplantation (LT). We aimed to investigate the prognostic factors and outcomes of wait-listed patients with PSC in an Asian transplant center.

METHODS

Survival was retrospectively analyzed.

RESULTS

Eighteen (10 male and 8 female) wait-listed patients with PSC, with a median age at diagnosis of 44.5 years, were included. Compared with men, women had significantly higher aspartate aminotransferase to platelet ratio index scores (3.28 vs. 1.13; P  = 0.012) and bilirubin levels (7.68 vs. 4.03 mg/dl; P  = 0.043) and more often presented with decompensating events, including ascites [5 (63%) vs. 1 (10%); P  = 0.043] and splenomegaly [8 (100%) vs. 4 (40%); P  = 0.013]. Compared with the non-LT group, the LT group exhibited a superior survival rate for women ( P  = 0.004) but not for men. In the univariable analysis, significant risk factors associated with overall survival included malignancies with a hazard ratio (95% confidence interval) of 5.53 (1.00-30.51) and esophageal varices (EV) [4.18 (1.05-16.61)], whereas female gender [25.00 (1.49-500.00)], LT [0.09 (0.01-0.80)] and EV [39.03 (2.92-521.96)] were indicated in the multivariable analysis.

CONCLUSIONS

For Asian wait-listed patients with PSC, EV and female gender were the risk factors related to overall survival, and LT was the protective factor. Our experiences suggested that LT brings more benefits in female patients. Strategies are needed to provide equivalent transplant benefits.

The effect of sex inequality on solid organ transplantation: A systematic review and meta-analysis

BACKGROUND

Sex disparities are related to biological differences, which may have significant impact on patient and allograft outcomes. The aim was to investigate the impact of sex on clinical and safety outcomes after solid organ transplantation (SOT).

METHODS

A systematic review and meta-analysis was performed. Observational studies comparing females vs. males after SOT were considered for inclusion after a systematic search of the Pubmed, Cochrane Library, and Web of Science databases conducted from 2016 to 2021. Primary outcome was mortality. PROSPERO register number: CRD42021282615.

RESULTS

After retrieving 1103 studies, 22 observational studies (1,045,380 subjects) were finally deemed eligible for inclusion. Females accounted 36.3% of SOT recipients, but presented significantly lower mortality (odds ratio (OR): 0.87, 95% confidence interval (CI): 0.83-0.92, I2=78%). In subgroup analyses, mortality was significantly lower in females undergoing liver (OR: 0.89 95%CI: 0.86-0.92, I2=0%) or kidney transplantation (OR: 0.82 95%CI: 0.76-0.89, I2=72%). Male sex was consistently reported as a protective factor against hospital readmission. Among the outcomes, allograft dysfunction was influenced by a combination of donor-recipient sex and age. Data on overall infections were inconclusive. Several reports suggest a higher risk of malignancy among males.

CONCLUSIONS

Females represent one-third of SOT recipients but have higher survival rates than males after liver and kidney transplantation. The impact on graft dysfunction was heterogeneous. While further research is warranted, our findings should encourage clinicians and researchers to consider sex as a factor when taking decisions regarding SOT management.

The role of gut microbiota in liver regeneration

The liver has unique regeneration potential, which ensures the continuous dependence of the human body on hepatic functions. As the composition and function of gut microbiota has been gradually elucidated, the vital role of gut microbiota in liver regeneration through gut-liver axis has recently been accepted. In the process of liver regeneration, gut microbiota composition is changed. Moreover, gut microbiota can contribute to the regulation of the liver immune microenvironment, thereby modulating the release of inflammatory factors including IL-6, TNF-α, HGF, IFN-γ and TGF-β, which involve in different phases of liver regeneration. And previous research have demonstrated that through enterohepatic circulation, bile acids (BAs), lipopolysaccharide, short-chain fatty acids and other metabolites of gut microbiota associate with liver and may promote liver regeneration through various pathways. In this perspective, by summarizing gut microbiota-derived signaling pathways that promote liver regeneration, we unveil the role of gut microbiota in liver regeneration and provide feasible strategies to promote liver regeneration by altering gut microbiota composition.

The Microbiome and Metabolomic Profile of the Transplanted Intestine with Long-Term Function

We analyzed the fecal microbiome by deep sequencing of the 16S ribosomal genes and the metabolomic profiles of 43 intestinal transplant recipients to identify biomarkers of graft function. Stool samples were collected from 23 patients with stable graft function five years or longer after transplant, 15 stable recipients one-year post-transplant and four recipients with refractory rejection and graft loss within one-year post-transplant. Lactobacillus and Streptococcus species were predominant in patients with stable graft function both in the short and long term, with a microbiome profile consistent with the general population. Conversely, Enterococcus species were predominant in patients with refractory rejection as compared to the general population, indicating profound dysbiosis in the context of graft dysfunction. Metabolomic analysis demonstrated significant differences between the three groups, with several metabolites in rejecting recipients clustering as a distinct set. Our study suggests that the bacterial microbiome profile of stable intestinal transplants is similar to the general population, supporting further application of this non-invasive approach to identify biomarkers of intestinal graft function.

A decrease in functional microbiomes represented as Faecalibacterium affects immune homeostasis in long-term stable liver transplant patients

LT, liver transplantation; HCC, hepatocellular carcinoma; IS, immunosuppressants; DC, dendritic cells; Treg, regulatory T; Th17, T helper 17; AST, aspartate transaminase; ALT, alanine transaminase; OUT, operational taxonomic unit; LEfSe, linear discriminant analysis effect size; LDA, linear discriminant analysis; IL, interleukin; TGF, transforming growth factor; GM-CSF, granulocyte-macrophage colony-stimulating factor; IFN, interferon; TNF-α, tumor necrosis factor-α; MIP-1α, macrophage inflammatory protein-1α; IP-10, interferon γ-induced protein; MCP-1, monocyte chemoattractant protein-1; ACR, acute cellular rejection; NF-κB, nuclear factor κB; PT INR, prothrombin time; QC, quality check; PBMC, peripheral blood mononuclear cells; PBS, phosphate-buffered saline; ELISA, enzyme-linked immunosorbent assay.

Interactions between human microbiome, liver diseases, and immunosuppression after liver transplant

In liver transplant patients, solid tumors and post-transplant lymphoproliferative disorders have emerged as significant long-term mortality causes. In addition, it is assumed that de novo malignancy after liver transplantation (LT) is the second-leading cause of death after cardiovascular complications. Well-established risk factors for post-transplant lymphoproliferative disorders and solid tumors are calcineurin inhibitors, tacrolimus, and cyclosporine, the cornerstones of all immunosuppressive therapies used after LT. The loss of immunocompetence facilitated by the host immune system due to prolonged immunosuppressive therapy leads to cancer development, including LT patients. Furthermore, various mechanisms such as bacterial dysbiosis, activation through microbe-associated molecular patterns, leaky gut, and bacterial metabolites can drive cancer-promoting liver inflammation, fibrosis, and genotoxicity. Therefore, changes in human microbiota composition may contribute further to de novo carcinogenesis associated with the severe immunosuppression after LT.

Characteristics, Trends, and Outcomes of Liver Transplantation for Primary Sclerosing Cholangitis in Female Versus Male Patients: An Analysis From the European Liver Transplant Registry

BACKGROUND

The influence of sex on primary sclerosing cholangitis (PSC), pre- and postliver transplantation (LT) is unclear. Aims are to assess whether there have been changes in incidence, profile, and outcome in LT-PSC patients in Europe with specific emphasis on sex.

METHODS

Analysis of the European Liver Transplant Registry database (PSC patients registered before 2018), including baseline demographics, donor, biochemical, and clinical data at LT, immunosuppression, and outcome.

RESULTS

European Liver Transplant Registry analysis (n = 6463, 32% female individuals) demonstrated an increasing number by cohort (1980-1989, n = 159; 1990-1999, n = 1282; 2000-2009, n = 2316; 2010-2017, n = 2549) representing on average 4% of all transplant indications. This increase was more pronounced in women (from 1.8% in the first cohort to 4.3% in the last cohort). Graft survival rate at 1, 5, 10, 15, 20, and 30 y was 83.6%, 70.8%, 57.7%, 44.9%, 30.8%, and 11.6%, respectively. Variables independently associated with worse survival were male sex, donor and recipient age, cholangiocarcinoma at LT, nondonation after brain death donor, and reduced size of the graft. These findings were confirmed using a more recent LT population closer to the current standard of care (LT after the y 2000).

CONCLUSIONS

An increasing number of PSC patients, particularly women, are being transplanted in European countries with better graft outcomes in female recipients. Other variables impacting outcome include donor and recipient age, cholangiocarcinoma, nondonation after brain death donor, and reduced graft size.

Temporal dynamics of the plasma microbiome in recipients at early post-liver transplantation: a retrospective study

Background

Immunosuppression during liver transplantation (LT) enables the prevention and treatment of organ rejection but poses a risk for severe infectious diseases. Immune modulation and antimicrobials affect the plasma microbiome. Thus, determining the impact of immunosuppression on the microbiome may be important to understand immunocompetence, elucidate the source of infection, and predict the risk of infection in LT recipients. We characterized the plasma microbiome of LT recipients at early post-LT and assessed the association between the microbiome and clinical events.

Results

In this study, 51 patients who received LT at Nagoya University Hospital from 2016 to 2018 were enrolled. Plasma samples were retrospectively collected at the following time points: 1) within a week after LT; 2) 4 ± 1 weeks after LT; 3) 8 ± 1 weeks after LT; and 4) within 2 days after a positive blood culture. A total of 111 plasma samples were analyzed using shotgun next-generation sequencing (NGS) with the PATHDET pipeline. Relative abundance of Anelloviridae, Nocardiaceae, Microbacteriaceae, and Enterobacteriaceae significantly changed during the postoperative period. Microbiome diversity was higher within a week after LT than that at 8 weeks after LT. Antimicrobials were significantly associated with the microbiome of LT recipients. In addition, the proportion of Enterobacteriaceae was significantly increased and the plasma microbiome diversity was significantly lower in patients with acute cellular rejection (ACR) than non-ACR patients. Sequencing reads of bacteria isolated from blood cultures were predominantly identified by NGS in 8 of 16 samples, and human herpesvirus 6 was detected as a causative pathogen in one recipient with severe clinical condition.

Conclusions

The metagenomic NGS technique has great potential in revealing the plasma microbiome and is useful as a comprehensive diagnostic procedure in clinical settings. Temporal dynamics of specific microorganisms may be used as indirect markers for the determination of immunocompetence and ACR in LT recipients.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12866-021-02154-w.

Effects of Gut Metabolites and Microbiota in Healthy and Marginal Livers Submitted to Surgery

Microbiota is defined as the collection of microorganisms within the gastrointestinal ecosystem. These microbes are strongly implicated in the stimulation of immune responses. An unbalanced microbiota, termed dysbiosis, is related to the development of several liver diseases. The bidirectional relationship between the gut, its microbiota and the liver is referred to as the gut-liver axis. The translocation of bacterial products from the intestine to the liver induces inflammation in different cell types such as Kupffer cells, and a fibrotic response in hepatic stellate cells, resulting in deleterious effects on hepatocytes. Moreover, ischemia-reperfusion injury, a consequence of liver surgery, alters the microbiota profile, affecting inflammation, the immune response and even liver regeneration. Microbiota also seems to play an important role in post-operative outcomes (i.e., liver transplantation or liver resection). Nonetheless, studies to determine changes in the gut microbial populations produced during and after surgery, and affecting liver function and regeneration are scarce. In the present review we analyze and discuss the preclinical and clinical studies reported in the literature focused on the evaluation of alterations in microbiota and its products as well as their effects on post-operative outcomes in hepatic surgery.

Impact of the Post-Transplant Period and Lifestyle Diseases on Human Gut Microbiota in Kidney Graft Recipients

Gaining long-term graft function and patient life quality remain critical challenges following kidney transplantation. Advances in immunology, gnotobiotics, and culture-independent molecular techniques have provided growing insights into the complex relationship of the microbiome and the host. However, little is known about the over time-shift of the gut microbiota in the context of kidney transplantation and its impact on both graft and health stability. Here we aimed to characterize the structure of gut microbiota within stable kidney graft recipients. We enrolled forty kidney transplant patients after at least three months of transplantation and compared them to eighteen healthy controls. The overall microbial community structure of the kidney transplanted group was clearly different from control subjects. We found lower relative abundances of Actinobacteria, Bacteroidetes, and Verrucomicrobia within the patient group and a higher abundance of Proteobacteria compared to the control group. Both richness and Shannon diversity indexes were significantly lower in the kidney graft recipients than in healthy controls. Post-graft period was positively correlated with the relative abundance of the Proteobacteria phylum, especially Escherichia.Shigella genus. Interestingly, only Parabacteroides was found to significantly differentiate patients that were not suffering from lifestyle diseases and those who suffer from post-graft complications. Furthermore, network analysis showed that the occurrence of lifestyle diseases was significantly linked with a higher number of negative interactions of Sutterella and Succinivibrio genera within patients. This study characterizes gut microbiome fluctuation in stable kidney transplant patients after a long post-allograft period. Analysis of fecal microbiota could be useful for nephrologists as a new clinical tool that can improve kidney allograft monitoring and outcomes.

Clinical relevance of plasma virome dynamics in liver transplant recipients

BACKGROUND

The role of the microbiome in liver transplantation (LT) outcome has received a growing interest in the past decades. In contrast to bacteria, the role of endogenous viral communities, known as the virome, is poorly described. Here, we applied a viral metagenomic approach to study the dynamic evolution of circulating viruses in the plasma of LT recipients and its effect on the clinical course of patients.

METHODS

Patients chronically infected with hepatitis B virus (HBV) that received a LT due to endstage liver disease were included in this study. Longitudinal plasma samples were collected pre- and post-LT. Intact viral particles were isolated and sequenced on an Illumina HiSeq 2500 platform. Short read libraries were analysed with an in-house bioinformatics pipeline. Key endpoints were the dynamics of viral families and post-LT complications.

FINDINGS

The initiation of immunosuppression induced a bloom of the Anelloviridae that dominated the post-LT plasma virome. A variety of post-LT complication were observed. Nephrotoxicity was reported in 38% of the patients and was associated with a high abundance of anelloviruses. Besides nephrotoxicity, 16 (67%) patients experienced flares of viral or bacterial infections in post-transplant follow-up. These flares were recognized by an increased burden of anelloviruses (p < 0.05). Interestingly, no mortality was observed in patients infected with human pegivirus.

INTERPRETATION

These findings suggest a diagnostic potential for the Anelloviridae family in post-LT complications. Furthermore, the impact of human pegivirus infection on post-transplant survival should be further investigated.

FUNDING

This trial was supported by Gilead Sciences grant number BE-2017-000133.

Anti-aging properties of Dendrobium nobile Lindl.: From molecular mechanisms to potential treatments

ETHNOPHARMACOLOGICAL RELEVANCE

Dendrobium Nobile Lindl. (DNL) is one of the central herbs in traditional Chinese medicine which mainly distributes in Guizhou, Yunnan, Guangxi and other sub-tropical areas south of the Yangtze River. In the past decades, it has been used to treat tumors, hyperglycemia, hyperlipidemia, and diseases of the nervous system that may be caused by aging.

AIM OF THE REVIEW

The purpose of this review is to summarize the anti-aging information of DNL from the molecular mechanism level, including classic theories related to aging, main chemical components, pharmacological research and anti-aging theory based on traditional Chinese medicine theory, for exploring the future development and clinical treatment.

MATERIALS AND METHODS

The information in this paper has been collected from the scientific literature databases including PubMed, Google Scholar, Web of Science, Science Direct, Springer, China National Knowledge Infrastructure, published books, Ph.D. and M.S. dissertations systematically.

RESULTS

In this paper, we have reviewed the several mechanisms underlying the potential effects of DNL on the prevention of aging, including the scavenging of free radicals for oxidation, delaying of DNA impairment, inhibition of apoptosis, and alteration of DNA methylation. Together with the theory of telomeres, this review also has summarized recent research progress in the use of DNL and its traditional efficacy.

CONCLUSIONS

We conclude that "strengthening Yin and benefiting the spirit", "thickening the intestine and stomach", "lightning the body and prolonging the life-span", and delaying aging, are key effects of DNL that can be used to combat age-related diseases (ARDs) such as Alzheimer's disease, hyperlipidemia, and diabetes. This review provides a reference for future study of ARDs and the clinical application of DNL.

The Gut-liver Axis in Immune Remodeling: New insight into Liver Diseases

The gut microbiota consists of a dynamic multispecies community of bacteria, fungi, archaea, and protozoans, playing a fundamental role in the induction, training, and function of the host immune system. The liver is anatomically and physiologically linked to the gut microbiota via enterohepatic circulation, specifically receiving intestine-derived blood through the portal vein. The gut microbiota is crucial for maintaining immune homeostasis of the gut-liver axis. A shift in gut microbiota composition can result in activation of the mucosal immune response causing homeostasis imbalance. This imbalance results in translocation of bacteria and migration of immune cells to the liver, which is related to inflammation-mediated liver injury and tumor progression. In this review, we outline the role of the gut microbiota in modulating host immunity and summarize novel findings and recent advances in immune-based therapeutics associated with the gut-liver axis. Moving forward, a deep understanding of the microbiome-immune-liver axis will provide insight into the basic mechanisms of gut microbiota dysbiosis affecting liver diseases.

A new insight into acute lymphoblastic leukemia in children: influences of changed intestinal microfloras

Background

Previous studies have shown that changes in intestinal microfloras are associated with both gastrointestinal (GI) and non-GI tumors. It is not clear whether there is an association between GI microflora changes and hematological malignancies.

Methods

In the current study, we used 16S rDNA gene sequencing techniques to profile the GI microbiome in children with lymphoblastic leukemia (ALL, n = 18) and matched healthy control (n = 18). Using multiple specialized software [Heatmap, Principal coordinates analysis (PCoA), Claster and Metastates], we analyzed the sequencing data for microfloral species classification, abundance and diversity.

Results

A total of 27 genera between the ALL and control groups (FDR ≤ 0.05 and/or P ≤ 0.05) showed significantly different abundance between ALL patients and healthy controls: 12 of them were predominant in healthy group and other 15 species were significantly higher in ALL group. In addition, we compared the abundance and diversity of microfloral species in ALL patients prior to and during remission stage after chemotherapy, and no significant difference was detected.

Conclusions

Compared to healthy controls, ALL patient showed significant changes of GI microfloras. Further explorations of the intestinal micro-ecology in ALL patients may provide important information to understand relationship between microfloras and ALL.

Bile microbiota: new insights into biliary complications in liver transplant recipients

Background

Biliary complications represent a major problem associated with liver transplantation. This report represents the first study to use high-throughput 16S ribosomal RNA (rRNA) gene sequencing to assess bile microbiota within bile samples of liver transplant recipients with biliary complications. Our goal in this report was to identify the species and abundance of microbes and examine the potential for microbial involvement of bile in liver transplantation patients with biliary complications.

Methods

Liver transplant recipients treated at our center over the period from September 2015 to June 2017 were enrolled in the study. Patients satisfying the inclusion criteria were divided into two groups, control (N=13) and symptom (N=10). Sequencing of 16s rDNA was then performed on bile samples from both groups.

Results

The main bacterial phyla of bile samples in the symptom group included Proteobacteria (55.19%), Firmicutes (32.36%), Actinobacteria (10.24%) and Bacteroidetes (1.23%) and the main bacterial genera were Pseudomonas (23.31%), Klebsiella (18.42%), Lactococcus (9.61%), Rhodococcus (9.59%) and Rhizobium (5.08%). Proteobacteria and Staphylococcus were enriched in the symptom group (P<0.05), whereas Firmicutes (P<0.05) and Enterococcus (P<0.01) were enriched in the control group. Pathways involved as determined with use of the Kyoto Encyclopedia of Genes and Genomes (KEGG), revealed that metabolism pathways of glyoxylate and dicarboxylate, porphyrin and chlorophyll, arginine and proline, glycine, serine and threonine, as well as the bacterial secretion system were all enriched in bile samples from the symptom group (P<0.05).

Conclusions

Clear differences exist in microbial species distribution in bile samples from the symptom versus control group. The species and pathways enriched in bile samples within the symptom group may be involved in the pathogenesis of biliary complication after liver transplantation.

Role of Gut Dysbiosis in Liver Diseases: What Have We Learned So Far?

Accumulating evidence supports that gut dysbiosis may relate to various liver diseases. Alcoholics with high intestinal permeability had a decrease in the abundance of Ruminnococcus. Intestinal dysmotility, increased gastric pH, and altered immune responses in addition to environmental and genetic factors are likely to cause alcohol-associated gut microbial changes. Alcohol-induced dysbiosis may be associated with gut barrier dysfunction, as microbiota and their products modulate barrier function by affecting epithelial pro-inflammatory responses and mucosal repair functions. High levels of plasma endotoxin are detected in alcoholics, in moderate fatty liver to advanced cirrhosis. Decreased abundance of Faecalibacterium prausnitzii, an anti-inflammatory commensal, stimulating IL-10 secretion and inhibiting IL-12 and interferon-γ expression. Proteobacteria, Enterobacteriaceae, and Escherichia were reported to be increased in NAFLD (nonalcoholic fatty liver disease) patients. Increased abundance of fecal Escherichia to elevated blood alcohol levels in these patients and gut microbiota enriched in alcohol-producing bacteria produce more alcohol (alcohol hypothesis). Some undetermined pathological sequences related to gut dysbiosis may facilitate energy-producing and proinflammatory conditions for the progression of NAFLD. A shortage of autochthonous non-pathogenic bacteria and an overgrowth of potentially pathogenic bacteria are common findings in cirrhotic patients. The ratio of the amounts of beneficial autochthonous taxa (Lachnospiraceae + Ruminococaceae + Veillonellaceae + Clostridiales Incertae Sedis XIV) to those of potentially pathogenic taxa (Enterobacteriaceae + Bacteroidaceae) was low in those with early death and organ failure. Cirrhotic patients with decreased microbial diversity before liver transplantation were more likely to develop post-transplant infections and cognitive impairment related to residual dysbiosis. Patients with PSC had marked reduction of bacterial diversity. Enterococcus and Lactobacillus were increased in PSC patients (without liver cirrhosis.) Treatment-naive PBC patients were associated with altered composition and function of gut microbiota, as well as a lower level of diversity. As serum anti-gp210 antibody has been considered as an index of disease progression, relatively lower species richness and lower abundance of Faecalibacterium spp. in gp210-positive patients are interesting. The dysbiosis-induced altered bacterial metabolites such as a hepatocarcinogenesis promotor DCA, together with a leaky gut and bacterial translocation. Gut protective Akkermansia and butyrate-producing genera were decreased, while genera producing-lipopolysaccharide were increased in early hepatocellular carcinoma (HCC) patients.

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.

Functional Microbiomics in Liver Transplantation: Identifying Novel Targets for Improving Allograft Outcomes

Gut dysbiosis, defined as a maladaptive gut microbial imbalance, has been demonstrated in patients with end-stage liver disease, defined as a contributor to disease progression, and associated clinically with severity of disease and liver-related morbidity and mortality. Despite this well-recognized phenomena in patients with end-stage liver disease, the impact of gut dysbiosis and its rate of recovery following liver transplantation (LT) remains incompletely understood. The mechanisms by which alterations in the gut microbiota impact allograft metabolism and immunity, both directly and indirectly, are multifactorial and reflect the complexity of the gut-liver axis. Importantly, while research has largely focused on quantitative and qualitative changes in gut microbial composition, changes in microbial functionality (in the presence or absence of compositional changes) are of critical importance. Therefore, to translate functional microbiomics into clinical practice, one must understand not only the compositional but also the functional changes associated with gut dysbiosis and its resolution post-LT. In this review, we will summarize critical advances in functional microbiomics in LT recipients as they apply to immune-mediated allograft injury, posttransplant complications, and disease recurrence, while highlighting potential areas for microbial-based therapeutics in LT recipients.

Fecal Microbiome Data Distinguish Liver Recipients With Normal and Abnormal Liver Function From Healthy Controls

Emerging evidence suggests that altered intestinal microbiota plays an important role in the pathogenesis of many liver diseases, mainly by promoting inflammation via the “intestinal microbiota-immunity-liver” axis. We aimed to investigate the fecal microbiome of liver recipients with abnormal/normal liver function using 16S rRNA gene sequencing. Fecal samples were collected from 90 liver recipients [42 with abnormal liver function (Group LT_A) and 48 with normal liver function (Group LT_N)] and 61 age- and gender-matched healthy controls (HCs). Fecal microbiomes were analyzed for comparative composition, diversity, and richness of microbial communities. Principal coordinates analysis successfully distinguished the fecal microbiomes of recipients in Group LT_A from healthy subjects, with the significant decrease of fecal microbiome diversity in recipients in Group LT_A. Other than a higher relative abundance of opportunistic pathogens such as Klebsiella and Escherichia/Shigella in all liver recipients, the main difference in gut microbiome composition between liver recipients and HC was the lower relative abundance of beneficial butyrate-producing bacteria in the recipients. Importantly, we established a fecal microbiome index (specific alterations in Staphylococcus and Prevotella) that could be used to distinguish Group LT_A from Group LT_N, with an area under the receiver operating characteristic curve value of 0.801 and sensitivity and specificity values of 0.771 and 0.786, respectively. These findings revealed unique gut microbial characteristics of liver recipients with abnormal and normal liver functions, and identified fecal microbial risk indicators of abnormal liver function in liver recipients.

A High Portal Venous Pressure Gradient Increases Gut-Related Bacteremia and Consequent Early Mortality After Living Donor Liver Transplantation

BACKGROUND

Portal hypertension (PHT) is defined as a portal venous pressure gradient (PVPG) exceeding 5 mm Hg, which results in severe clinical manifestations. However, the validity of intraoperative PVPG monitoring and the association between PHT and bacterial translocation after liver transplantation remain unclear.

METHODS

In this retrospective study, 223 patients who underwent primary adult-to-adult living donor liver transplantation from 2008 to 2015 were divided into 2 groups based on the PVPG at the end of the operation: high PVPG (>5 mm Hg, n = 69) and low PVPG (≤5 mm Hg, n = 154). The clinical factors were compared between the groups, and the association between a high PVPG and posttransplant bacteremia/bacterial infections was investigated.

RESULTS

The high PVPG group had a significantly higher incidence of bacteremia (46% vs 24%, P < 0.001), higher 90-day mortality rate (20% vs 7%, P = 0.002), and poorer 1-year survival (71% vs 86%, P = 0.006). The high PVPG group had a particularly higher incidence of bacteremia caused by "gut bacteria" including Enterobacteriaceae, Bacteroides spp., and Enterococcus spp. (29% vs 12%, P = 0.003). Multivariate analysis showed that a PVPG greater than 5 mm Hg (odds ratio, 2.55; 95% confidence interval, 1.18-5.55; P = 0.017) was an independent predictor of bacteremia due to gut bacteria.

CONCLUSIONS

Monitoring of the PVPG is clinically meaningful for predicting patients' prognosis. In particular, a high PVPG with a threshold of 5 mm Hg at the end of adult-to-adult living donor liver transplantation may increase gut-related bacteremia through the mechanism of bacterial translocation, resulting in early mortality.

The impact of ileal pouch-anal anastomosis on graft survival following liver transplantation for primary sclerosing cholangitis

BACKGROUND

Liver transplantation is the only life-extending intervention for primary sclerosing cholangitis (PSC). Given the co-existence with colitis, patients may also require colectomy; a factor potentially conferring improved post-transplant outcomes.

AIM

To determine the impact of restorative surgery via ileal pouch-anal anastomosis (IPAA) vs retaining an end ileostomy on liver-related outcomes post-transplantation.

METHODS

Graft survival was evaluated across a prospectively accrued transplant database, stratified according to colectomy status and type.

RESULTS

Between 1990 and 2016, 240 individuals with PSC/colitis underwent transplantation (cumulative 1870 patient-years until first graft loss or last follow-up date), of whom 75 also required colectomy. A heightened incidence of graft loss was observed for the IPAA group vs those retaining an end ileostomy (2.8 vs 0.4 per 100 patient-years, log-rank P = 0.005), whereas rates between IPAA vs no colectomy groups were not significantly different (2.8 vs 1.7, P = 0.1). In addition, the ileostomy group experienced significantly lower graft loss rates vs. patients retaining an intact colon (P = 0.044). The risks conferred by IPAA persisted when taking into account timing of colectomy as related to liver transplantation via time-dependent Cox regression analysis. Hepatic artery thrombosis and biliary strictures were the principal aetiologies of graft loss overall. Incidence rates for both were not significantly different between IPAA and no colectomy groups (P = 0.092 and P = 0.358); however, end ileostomy appeared protective (P = 0.007 and 0.031, respectively).

CONCLUSION

In PSC, liver transplantation, colectomy + IPAA is associated with similar incidence rates of hepatic artery thrombosis, recurrent biliary strictures and re-transplantation compared with no colectomy. Colectomy + end ileostomy confers more favourable graft outcomes.

Alterations in gut microbial function following liver transplant

Liver transplantation (LT) improves daily function and ameliorates gut microbial composition. However, the effect of LT on microbial functionality, which can be related to overall patient benefit, is unclear and could affect the post-LT course. The aims were to determine the effect of LT on gut microbial functionality focusing on endotoxemia, bile acid (BA), ammonia metabolism, and lipidomics. We enrolled outpatient patients with cirrhosis on the LT list and followed them until 6 months after LT. Microbiota composition (Shannon diversity and individual taxa) and function analysis (serum endotoxin, urinary metabolomics and serum lipidomics, and stool BA profile) and cognitive tests were performed at both visits. We enrolled 40 patients (age, 56 ± 7 years; mean Model for End-Stage Liver Disease score, 22.6). They received LT 6 ± 3 months after enrollment and were re-evaluated 7 ± 3 months after LT with a stable course. A significant improvement in cognition with increase in microbial diversity, increase in autochthonous and decrease in potentially pathogenic taxa, and reduced endotoxemia were seen after LT compared with baseline. Stool BAs increased significantly after LT, and there was evidence of greater bacterial action (higher secondary, oxo and iso-BAs) after LT although the levels of conjugated BAs remained similar. There was a reduced serum ammonia and corresponding rise in urinary phenylacetylglutamine after LT. There was an increase in urinary trimethylamine-N-oxide, which was correlated with specific changes in serum lipids related to cell membrane products. The ultimate post-LT lipidomic profile appeared beneficial compared with the profile before LT. In conclusion, LT improves gut microbiota diversity and dysbiosis, which is accompanied by favorable changes in gut microbial functionality corresponding to BAs, ammonia, endotoxemia, lipidomic, and metabolomic profiles. Liver Transplantation 24 752-761 2018 AASLD.

Comparative pharmacokinetics of triterpenic acids in normal and immunosuppressed rats after oral administration of Jujubae Fructus extract by UPLC-MS/MS

The fruit of Ziziphus jujuba (Jujubae Fructus) has been used as food and crude drug for thousands of years. Although several chemical and biological studies have revealed triterpenic acid as the main bioactive constituent of Jujubae Fructus responsible for immune-regulatory activity, only few pharmacokinetic studies have been conducted. To comprehend the kinetics of triterpenic acids and promote their curative application, a sensitive and efficient ultra-performance liquid chromatography coupled with mass spectrometry method (UPLC-MS/MS) was established. UPLC-MS/MS was applied for the simultaneous determination of ceanothic acid, epiceanothic acid, pomonic acid, alphitolic acid, maslinic acid, betulinic acid, and betulonic acid in normal and immunosuppressed rat plasma samples. After sample preparation, chromatographic separation was performed on an Acquity UPLC BEH C₁₈ column (2.1 × 100 mm, 1.7 μm) with acetonitrile: methanol (1:1, v/v) and 0.5% ammonium acetate in water as mobile phase. The established method was validated and found to be specific, accurate, and precise for the seven triterpenic acids, and was successfully applied for the pharmacokinetic study of rat plasma samples. The results showed that the pharmacokinetic parameters (C_max, T_max, AUC_0-t, AUC_0-∞, and CLz/F) in the plasma samples of immunosuppressed rats were significantly different from those in normal rats, and might provide an insight for the clinical usage of triterpenic acids from Jujubae Fructus.

Characteristics of fecal microbial communities in patients with non-anastomotic biliary strictures after liver transplantation

AIM

To explore the possible relationship between fecal microbial communities and non-anastomotic stricture (NAS) after liver transplantation (LT).

METHODS

A total of 30 subjects including 10 patients with NAS, 10 patients with no complications after LT, and 10 non-LT healthy individuals were enrolled. Fecal microbial communities were assessed by the 16S rRNA gene sequencing technology.

RESULTS

Different from the uncomplicated and healthy groups, unbalanced fecal bacterium ratio existed in patients with NAS after LT. The results showed that NAS patients were associated with a decrease of Firmicutes and Bacteroidetes and an increase of Proteobacteria at the phylum level, with the proportion-ratio imbalance between potential pathogenic families including Enterococcaceae, Streptococcaceae, Enterobacteriaceae, Pseudomonadaceae and dominant families including Bacteroidaceae.

CONCLUSION

The compositional shifts of the increase of potential pathogenic bacteria as well as the decrease of dominant bacteria might contribute to the incidence of NAS.

Impact of Immunosuppression on the Metagenomic Composition of the Intestinal Microbiome: a Systems Biology Approach to Post-Transplant Diabetes

Solid organ transplantation (SOT) outcomes have continued to improve, although long-term use of immunosuppressants can lead to complications such as diabetes, compromising post-transplant outcomes. In this study, we have characterized the intestinal microbiome (IM) composition at the metagenomic level in the context of hyperglycemia induced by immunosuppressants. Sprague-Dawley rats were subjected to doses of tacrolimus and sirolimus that reliably induce hyperglycemia and an insulin-resistant state. Subsequent exposure to probiotics resulted in reversal of hyperglycemia. 16S rRNA and metagenomic sequencing of stool were done to identify the bacterial genes and pathways enriched in immunosuppression. Bacterial diversity was significantly decreased in sirolimus-treated rats, with 9 taxa significantly less present in both immunosuppression groups: Roseburia, Oscillospira, Mollicutes, Rothia, Micrococcaceae, Actinomycetales and Staphylococcus. Following probiotics, these changes were reversed to baseline. At the metagenomic level, the balance of metabolism was shifted towards the catabolic side with an increase of genes involved in sucrose degradation, similar to diabetes. Conversely, the control rats had greater abundance of anabolic processes and genes involved in starch degradation. Immunosuppression leads to a more catabolic microbial profile, which may influence development of diabetes after SOT. Modulation of the microbiome with probiotics may help in minimizing adverse long-term effects of immunosuppression.

Liver transplant modulates gut microbial dysbiosis and cognitive function in cirrhosis

Liver transplantation (LT) improves daily function and cognition in patients with cirrhosis, but a subset of patients can remain impaired. Unfavorable microbiota or dysbiosis is observed in patients with cirrhosis, but the effect of LT on microbial composition, especially with poor post-LT cognition, is unclear. The aims were to determine the effect of LT on gut microbiota and to determine whether gut microbiota are associated with cognitive dysfunction after LT. We enrolled outpatient patients with cirrhosis on the LT list and followed them until 6 months after LT. Cognition (Psychometric Hepatic Encephalopathy score [PHES]), health-related quality of life (HRQOL), and stool microbiota (multitagged sequencing for diversity and taxa) tests were performed at both visits. Persistent cognitive impairment was defined as a stable/worsening PHES. Both pre-/post-LT data were compared with age-matched healthy controls. We enrolled 45 patients (56 ± 7 years, Model for End-Stage Liver Disease score 26 ± 8). They received LT 6 ± 3 months after enrollment and were re-evaluated 7 ± 2 months after LT with a stable course. A significantly improved HRQOL, PHES, with increase in microbial diversity, increase in autochthonous, and decrease in potentially pathogenic taxa were seen after LT compared with baseline. However, there was continued dysbiosis and HRQOL/cognitive impairment after LT compared with controls in 29% who did not improve PHES after LT. In these, Proteobacteria relative abundance was significantly higher and Firmicutes were lower after LT, whereas the reverse occurred in the group that improved. Delta PHES was negatively correlated with delta Proteobacteria and positively with delta Firmicutes. In conclusion, LT improves gut microbiota diversity and dysbiosis compared with pre-LT baseline but residual dysbiosis remains compared with controls. There is cognitive and HRQOL enhancement in general after LT, but a higher Proteobacteria relative abundance change is associated with posttransplant cognitive impairment. Liver Transplantation 23 907-914 2017 AASLD.

Gut microbiota of liver transplantation recipients

The characteristics of intestinal microbial communities may be affected by changes in the pathophysiology of patients with end-stage liver disease. Here, we focused on the characteristics of intestinal fecal microbial communities in post-liver transplantation (LT) patients in comparison with those in the same individuals pre-LT and in healthy individuals. The fecal microbial communities were analyzed via MiSeq-PE250 sequencing of the V4 region of 16S ribosomal RNA and were then compared between groups. We found that the gut microbiota of patients with severe liver disease who were awaiting LT was significantly different from that of healthy controls, as represented by the first principal component (p = 0.0066). Additionally, the second principal component represented a significant difference in the gut microbiota of patients between pre-LT and post-LT surgery (p = 0.03125). After LT, there was a significant decrease in the abundance of certain microbial species, such as Actinobacillus, Escherichia, and Shigella, and a significant increase in the abundance of other microbial species, such as Micromonosporaceae, Desulfobacterales, the Sarcina genus of Eubacteriaceae, and Akkermansia. Based on KEGG profiles, 15 functional modules were enriched and 21 functional modules were less represented in the post-LT samples compared with the pre-LT samples. Our study demonstrates that fecal microbial communities were significantly altered by LT.

The Mycobiome: Impact on Health and Disease States

The term "microbiome" refers to microorganisms (microbiota) and their genomes (metagenome) coexisting with their hosts. Some researchers coined the term "second genome" to underscore the importance of the microbiota and its collective metagenome on their host's health and/or disease. It is now undeniable that the commensal fungal microorganisms, alongside the other components of the microbiota, play a central role in association with the human host. In recognition, projects were launched nationally and internationally to unify efforts to characterize the microbiome and elucidate the functional role of the microbiota and the mechanism(s) by which these organisms and their metabolites (metabolome) may affect health and disease states. In this article, we will highlight the role of the fungal community as an indispensable component of the microbiome.

Longitudinal Analysis of the Intestinal Microbiota in Liver Transplantation

BACKGROUND

Increasing evidence suggests that the intestinal microbiota plays an important role in liver diseases. However, the dynamics of the intestinal microbiota during liver transplantation (LT) and its potential role in clinical course remain unknown.

METHODS

We prospectively analyzed the intestinal microbiota of 38 patients who underwent LT in Kyoto University Hospital. We characterized the microbial compositions of fecal specimens from LT patients using a metagenomics approach by an Illumina MiSeq platform. We analyzed the diversity of microbiota sequentially from pretransplantation until 2 months after LT and also compared the microbiota during an episode of acute cellular rejection (ACR) and bloodstream infections (BSI) to the microbial composition of time-matched fecal specimens obtained from patients who did not experience ACR or BSI, respectively.

RESULTS

Three hundred twenty fecal specimens were analyzed. Dynamic changes were observed in the microbial composition of LT recipients during the perioperative period. Over the course of LT, the mean diversity index decreased during the first 3 weeks after LT and gradually increased during our observation period. The loss of intestinal microbiota diversity was associated with high Child-Pugh scores, high model for end-stage liver disease scores, ACR, and BSI. At the family level, Bacteroides, Enterobacteriaceae, Streptococcaceae, and Bifidobacteriaceae were increased whereas Enterococcaceae, Lactobacillaceae, Clostridiaceae, Ruminococcaceae, and Peptostreptococcaceae were decreased in ACR patients.

CONCLUSIONS

The microbiota of LT patients was associated with the severity of liver diseases and the presence of ACR and BSI. These results lay the groundwork for more comprehensive investigations of microbiota characteristics to identify diagnostic markers for transplant health and to guide intervention strategies to improve transplant outcomes.