Effects of both Pro- and Synbiotics in Liver Surgery and Transplantation with Special Focus on the Gut-Liver Axis-A Systematic Review and Meta-Analysis

The role of gut barrier dysfunction in postoperative complications in liver transplantation: pathophysiological and therapeutic considerations

PURPOSE

Gut barrier dysfunction is a pivotal pathophysiological alteration in cirrhosis and end-stage liver disease, which is further aggravated during and after the operational procedures for liver transplantation (LT). In this review, we analyze the multifactorial disruption of all major levels of defense of the gut barrier (biological, mechanical, and immunological) and correlate with clinical implications.

METHODS

A narrative review of the literature was performed using PubMed, PubMed Central and Google from inception until November 29th, 2023.

RESULTS

Systemic translocation of indigenous bacteria through this dysfunctional barrier contributes to the early post-LT infectious complications, while endotoxin translocation, through activation of the systemic inflammatory response, is implicated in non-infectious complications including renal dysfunction and graft rejection. Bacterial infections are the main cause of early in-hospital mortality of LT patients and unraveling the pathophysiology of gut barrier failure is of outmost importance.

CONCLUSION

A pathophysiology-based approach to prophylactic or therapeutic interventions may lead to enhancement of gut barrier function eliminating its detrimental consequences and leading to better outcomes for LT patients.

Microbiota and Gut-Liver Axis: An Unbreakable Bond?

The gut microbiota, amounting to approximately 100 trillion (1014) microbes represents a genetic repertoire that is bigger than the human genome itself. Evidence on bidirectional interplay between human and microbial genes is mounting. Microbiota probably play vital roles in diverse aspects of normal human metabolism, such as digestion, immune modulation, and gut endocrine function, as well as in the genesis and progression of many human diseases. Indeed, the gut microbiota has been most closely linked to various chronic ailments affecting the liver, although concrete scientific data are sparse. In this narrative review, we initially discuss the basic epidemiology of gut microbiota and the factors influencing their initial formation in the gut. Subsequently, we delve into the gut-liver axis and the evidence regarding the link between gut microbiota and the genesis or progression of various liver diseases. Finally, we summarise the recent research on plausible ways to modulate the gut microbiota to alter the natural history of liver disease.

Role of the immune system in liver transplantation and its implications for therapeutic interventions

Liver transplantation (LT) stands as the gold standard for treating end-stage liver disease and hepatocellular carcinoma, yet postoperative complications continue to impact survival rates. The liver's unique immune system, governed by a microenvironment of diverse immune cells, is disrupted during processes like ischemia-reperfusion injury posttransplantation, leading to immune imbalance, inflammation, and subsequent complications. In the posttransplantation period, immune cells within the liver collaboratively foster a tolerant environment, crucial for immune tolerance and liver regeneration. While clinical trials exploring cell therapy for LT complications exist, a comprehensive summary is lacking. This review provides an insight into the intricacies of the liver's immune microenvironment, with a specific focus on macrophages and T cells as primary immune players. Delving into the immunological dynamics at different stages of LT, we explore the disruptions after LT and subsequent immune responses. Focusing on immune cell targeting for treating liver transplant complications, we provide a comprehensive summary of ongoing clinical trials in this domain, especially cell therapies. Furthermore, we offer innovative treatment strategies that leverage the opportunities and prospects identified in the therapeutic landscape. This review seeks to advance our understanding of LT immunology and steer the development of precise therapies for postoperative complications.

Gut Microbiome-Based Therapeutics in Critically Ill Adult Patients-A Narrative Review

The gut microbiota plays a crucial role in the human microenvironment. Dysbiosis of the gut microbiota is a common pathophysiological phenomenon in critically ill patients. Therefore, utilizing intestinal microbiota to prevent complications and improve the prognosis of critically ill patients is a possible therapeutic direction. The gut microbiome-based therapeutics approach focuses on improving intestinal microbiota homeostasis by modulating its diversity, or treating critical illness by altering the metabolites of intestinal microbiota. There is growing evidence that fecal microbiota transplantation (FMT), selective digestive decontamination (SDD), and microbiota-derived therapies are all effective treatments for critical illness. However, different treatments are appropriate for different conditions, and more evidence is needed to support the selection of optimal gut microbiota-related treatments for different diseases. This narrative review summarizes the curative effects and limitations of microbiome-based therapeutics in different critically ill adult patients, aiming to provide possible directions for gut microbiome-based therapeutics for critically ill patients such as ventilator-associated pneumonia, sepsis, acute respiratory distress syndrome, and COVID-19, etc.

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.

Gastrointestinal Microbiome and Multiple Health Outcomes: Umbrella Review

In recent years, there has been growing concern about the impact of the gastrointestinal microbiome on human health outcomes. To clarify the evidence for a link between the gastrointestinal microbiome and a variety of health outcomes in humans, we conducted an all-encompassing review of meta-analyses and systematic reviews that included 195 meta-analyses containing 950 unique health outcomes. The gastrointestinal microbiome is related to mortality, gastrointestinal disease, immune and metabolic outcomes, neurological and psychiatric outcomes, maternal and infant outcomes, and other outcomes. Existing interventions for intestinal microbiota (such as probiotics, fecal microbiota transplant, etc.) are generally safe and beneficial to a variety of human health outcomes, but the quality of evidence is not high, and more detailed and well-designed randomized controlled trials are necessary.

Influences of Oral Administration of Probiotics on Posthepatectomy Recovery in Patients in Child-Pugh Grade

Objective

This study is aimed at investigating the influences of oral administration of probiotics on posthepatectomy recovery in patients in Child-Pugh grade.

Methods

100 patients (50 cases in Child-Pugh A grade and 50 cases in Child-Pugh B grade) underwent hepatectomy in our hospital from January 2018 to January 2020 were involved in this study. Subsequently, Child-Pugh A grade and Child-Pugh B grade patients were set as probiotics group (taking Clostridium butyricum, n = 25) and control group (no probiotics, n = 25). The general information, infectious indexes, and liver function indexes on days 1, 3, and 5 after operation were collected.

Results

In Child-Pugh B grade subgroup patients, the procalcitonin, alanine aminotransferase, and prothrombin time of the probiotics group were statistically significantly lower than that of the control group on days 3 (P < 0.05) and 5 (P < 0.05) after surgery. In Child-Pugh A grade subgroup patients, there were no significant differences between probiotics group and control group after operation.

Conclusion

Child-Pugh A grade subgroup patients with hepatectomy could not benefit from oral probiotics. However, Child-Pugh B grade subgroup patients taking probiotics after hepatectomy could reduce postoperative infection and accelerate recovery of liver function.

Probiotics or Synbiotics for Preventing Postoperative Infection in Hepatopancreatobiliary Cancer Patients: A Meta-Analysis of Randomized Controlled Trials

OBJECTIVE

Postoperative infection of hepatopancreatobiliary cancer (HPBC) is a major cause of morbidity and mortality. Probiotics and synbiotics are potential prevention strategies, but evidence on the efficacy of probiotics or synbiotics in the prevention of postoperative infection for HPBC remains controversial. This study aimed to define the impact of probiotics or synbiotics on the incidence of postoperative infection in HPBC patients.

METHODS

A systematic search of the Cochrane Library, PubMed, Embase, and Web of Science databases was conducted from inception to February 2, 2021 to identify randomized controlled trials (RCTs) evaluating the efficacy of probiotics or synbiotics in HPBC. Data were pooled and expressed as the risk ratio (RR) and mean difference (MD) with 95% confidence intervals.

RESULTS

Eight RCTs involving 445 participants were included. Supplementation with probiotics or synbiotics significantly reduced the incidence of postoperative infection (RR 0.55) in HPBC patients, and both probiotics (RR 0.68) and synbiotics (RR 0.41) were effective in reducing the incidence of postoperative infection. In addition, probiotics or synbiotics can reduce duration of antibiotic use (MD -3.52) and length of hospital stay (MD -4.21).

CONCLUSION

Probiotics or synbiotics are effective strategies for the prevention of postoperative infection in HPBC patients.

Effects of Perioperative Probiotics and Synbiotics on Pancreaticoduodenectomy Patients: A Meta-Analysis of Randomized Controlled Trials

Post-pancreaticoduodenectomy infections cause mortality, morbidity, and prolonged antibiotic use. Probiotics or synbiotics may be advantageous for preventing postoperative infections, but their benefits on pancreaticoduodenectomy outcomes are controversial. This study evaluated the efficacy of probiotics and synbiotics in pancreaticoduodenectomy. The Embase, Web of Science, PubMed, and Cochrane Library databases were comprehensively searched for randomized controlled trials (RCTs) that evaluated the effects of probiotics or synbiotics on pancreaticoduodenectomy as of April 16, 2021. Outcomes included perioperative mortality, postoperative infectious complications, delayed gastric emptying, hospital stay length, and antibiotic-use duration. The results were reported as mean differences (MDs) and relative risks (RRs) with 95% confidence intervals (CI). Six RCTs involving 294 subjects were included. Probiotic or synbiotic supplementation did not reduce the perioperative mortality (RR, 0.34; 95% CI, 0.11, 1.03), but reduced the incidences of postoperative infection (RR, 0.49; 95% CI, 0.34, 0.70) and delayed gastric emptying (RR, 0.27; 95% CI, 0.09, 0.76) and also reduced the hospital stay length (MD, -7.87; 95% CI, -13.74, -1.99) and antibiotic-use duration (MD, -6.75; 95% CI, -9.58, -3.92) as compared to the controls. Probiotics or synbiotics can prevent infections, reduce delayed gastric emptying, and shorten the hospital stay and antibiotic-use durations in patients undergoing pancreaticoduodenectomy. These findings are clinically important for promoting recovery from pancreaticoduodenectomy, reducing the incidences of antibiotic resistance and iatrogenic infections, and reducing the medical burden.