Serum bile acids in liver transplantation--early indicator for acute rejection and monitor for antirejection therapy

Progress and challenges in diagnosis and treatment of rejection following liver transplantation

PURPOSE OF REVIEW

Liver biopsy remains the most widely utilized method for diagnosis of allograft rejection following liver transplantation. However, associated risks and limitations present an opportunity for emerging noninvasive diagnostic techniques to improve upon the current standard of care. This review evaluates progress toward development of new noninvasive methods for the monitoring and diagnosing of allograft rejection.

RECENT FINDINGS

Recent studies investigate the potential of a variety of analytes. Quantification of dd-cfDNA and of DSA show potential to indicate status of allograft rejection and aid in immunosuppression modulation. Moreover, mRNA microarray profiling of differentially expressed genes, as well as characterization of cytokine responses and immunophenotypic shifts following liver transplantation, may predict and recognize rejection events.

SUMMARY

Noninvasive methods are not yet ready to replace liver biopsy as the standard of care for diagnosis of allograft rejection, though several assays and biomarkers have shown promising preliminary results. As noninvasive techniques become validated in clinical settings, their integration with current diagnostic methods is likely to foster increased sensitivity, specificity, and reliability of diagnosis.

Use of bile acids as potential markers of liver dysfunction in humans: A systematic review

OBJECTIVE

This study aimed to determine the effectiveness of using total, individual serum, or urinary bile acids (BA) as potential markers of liver dysfunction.

METHODS

We searched the PubMed and Web of Science databases using the following keywords- "serum bile acids," "liver dysfunction," "liver injury," "liver disease," "traditional liver function tests," "Chronic liver disease," "acute liver injury". The search was complemented by manual screening of the list of references for relevant articles. We selected only English-language manuscripts for adult patients based on predetermined inclusion and exclusion criteria. Animal studies and studies on neonates and children were not included.

OUTCOME MEASURES

Changes in BA concentrations or ratios at or prior to changes in liver function tests.

RESULTS

A total of 547 studies were identified, of which 28 were included after reading the entire manuscript. These studies included 1630 patients and 836 controls published between 1990 and 2017. The methods used in BA assays varied significantly, and the studies did not agree. on specific individual BA or BA ratios as biomarkers of specific liver injury or dysfunction. Except for the prognostic value of BA in intrahepatic cholestasis of pregnancy (ICP), studies have failed to provide evidence for BA as a liver biomarker.

CONCLUSIONS

Despite the research conducted on BA for over 27 years, there are inconsistencies in the reported results and a lack of solid evidence to support the use of individual BA or BA ratios as biomarkers of liver injury. Adequately conducted studies needed to resolve this limitation in the literature.

Programmable receptors enable bacterial biosensors to detect pathological biomarkers in clinical samples

Bacterial biosensors, or bactosensors, are promising agents for medical and environmental diagnostics. However, the lack of scalable frameworks to systematically program ligand detection limits their applications. Here we show how novel, clinically relevant sensing modalities can be introduced into bactosensors in a modular fashion. To do so, we have leveraged a synthetic receptor platform, termed EMeRALD (Engineered Modularized Receptors Activated via Ligand-induced Dimerization) which supports the modular assembly of sensing modules onto a high-performance, generic signaling scaffold controlling gene expression in E. coli. We apply EMeRALD to detect bile salts, a biomarker of liver dysfunction, by repurposing sensing modules from enteropathogenic Vibrio species. We improve the sensitivity and lower the limit-of-detection of the sensing module by directed evolution. We then engineer a colorimetric bactosensor detecting pathological bile salt levels in serum from patients having undergone liver transplant, providing an output detectable by the naked-eye. The EMeRALD technology enables functional exploration of natural sensing modules and rapid engineering of synthetic receptors for diagnostics, environmental monitoring, and control of therapeutic microbes.

Serum bile acid levels assist the prediction of biliary stricture and survival after liver transplantation in children

Biliary stricture is an important biliary complication after liver transplant in children. We aimed to investigate the utility of serum bile acid levels for prediction of biliary stricture in children after liver transplant. This study enrolled 60 children who underwent liver transplantation at a mean age of 2.04±0.30 years; serum bile acid levels were surveyed in a cross-sectional design. These patients were followed regularly at our institute, and the clinical data were collected prospectively. The major indication of liver transplant in this pediatric cohort was biliary atresia (78.33%). During the follow-up period (3.08±0.30 years), nine patients (15%) developed biliary stricture after the check of serum bile acid. A receiver operating characteristic curve analysis yielded a serum bile acid cutoff of >40 μM for the prediction of biliary stricture (P = 0.002). A serum bile acid level >40 is the most important predictor of a biliary stricture after liver transplant (odds ratio=65.65, P = 0.003) after adjusting for gender and GGT levels. The phenomenon remained on Cox's proportional hazard survival analysis (hazard ratio =15.42, P = 0.001). The mortality risk after liver transplant was significantly higher in subjects with serum bile acid levels >40 μM than in those with levels ≤40 μM (log-rank test, P = 0.004).Conclusion: Serum bile acid levels can be used for non-invasive screening and prediction of biliary stricture and mortality in children after liver transplantation. What is Known: • Biliary stricture is a major biliary complication after pediatric liver transplantation, and we showed the serum bile acid level significantly associates with biliary stricture. What is New: • In this study, we demonstrated the serum bile acid level may assist in the early detection of biliary stricture and mortality non-invasively.

Genomics and Liver Transplantation: Genomic Biomarkers for the Diagnosis of Acute Cellular Rejection

Acute cellular rejection (ACR) is a common complication in liver transplantation recipients (LTRs), especially within the first 12 months, and it is associated with increased morbidity and mortality. Although abnormalities in standard liver biochemistries may raise the clinical suspicion for ACR, it lacks specificity, and invasive liver biopsies, which are associated with numerous risks, are required for definitive diagnoses. Biomarker discovery for minimally invasive tools for diagnosis and prognostication of ACR after liver transplantation (LT) has become a rapidly evolving field of research with a recent shift in focus to omics-based biomarker discovery. Although none are yet ready to replace the standard of care, there are several promising minimally invasive, blood-derived biomarkers that are under intensive research for the diagnosis of ACR in LTRs. These omics-based biomarkers, encompassing DNA, RNA, proteins, and metabolites, hold tremendous potential. Some are likely to become integrated into ACR diagnostic algorithms to assist clinical decision making with a high degree of accuracy that is cost-effective and reduces or even obviates the need for an invasive liver biopsy.

Prognostic value of endogenous and exogenous metabolites in liver transplantation

Liver transplantation has been widely accepted as an effective intervention for end-stage liver diseases and early hepatocellular carcinomas. However, a variety of postoperative complications and adverse reactions have baffled medical staff and patients. Currently, transplantation monitoring relies primarily on nonspecific biochemical tests, whereas diagnosis of multiple complications depends on invasive pathological examination. Therefore, a noninvasive monitoring method with high selectivity and specificity is desperately needed. This review summarized the potential of endogenous small-molecule metabolites as biomarkers for assessing graft function, ischemia-reperfusion injury and liver rejection. Exogenous metabolites, mainly those immunosuppressive agents with high intra- and inter-individual variability, were also discussed for transplantation monitoring.

Bile acids: Metabolism, physiology and clinical significance

Enterohepatic circulation of bile acids can promote lipid digestion and absorption, prevent gallstone formation, and increase the secretion of bile. Measurement of serum bile acids can be used to predict the progression from acute hepatitis to chronic hepatitis and evaluate the degree of inflammation and fibrosis in patients with chronic hepatitis and the degree of portal hypertension and severe hepatitis. Serum bile acids are also an early and sensitive predictor of the relief of biliary obstruction in patients with obstructive jaundice. In addition, serum bile acids can be used for the diagnosis of inflammatory bowel disease, intrahepatic cholestasis during pregnancy, congenital biliary tract disease, and liver transplantation.

Cell-free DNA as a potential marker to predict carbon tetrachloride-induced acute liver injury in rats

PURPOSE

Finding an optimal biomarker for the noninvasive evaluation of acute liver injury (ALI) may be of great value in predicting clinical outcomes and investigating potential treatments. We investigated cell-free DNA (CFD) as a potential biomarker to predict carbon tetrachloride-induced ALI in rats.

METHODS

Forty-five Sprague-Dawley rats were randomly assigned to three groups. ALI was induced by carbon tetrachloride via a nasogastric tube at 1, 2.5, or 5 ml/kg of a 50 % solution. Fifteen additional rats underwent a sham procedure. Blood samples were drawn at time t which was 0 (baseline), 3, 6, 12, 24, 48, 72, 96, and 120 h for the measurements of CFD, glutamate-pyruvate transaminase (GPT), glutamate-oxaloacetate transaminase (GOT), and total bilirubin. Prothrombin time and histology were examined at 24 and 120 h following injection of 5 ml/kg carbon tetrachloride in 18 additional rats and in 10 control rats.

RESULTS

CFD levels in rats subjected to carbon tetrachloride-induced ALI were significantly increased in all blood samples starting at 12 h after the induction of ALI (p < 0.001), reaching peak levels at 24 h. Blood GOT, GPT, and total bilirubin were elevated in all blood samples starting at 3 h after the induction of ALI (p < 0.0001), reaching peak levels by 48 h. A positive correlation was demonstrated between CFD levels and GOT (R (2) = 0.92), GPT (R (2) = 0.92), and total bilirubin (R (2) = 0.76). CFD levels correlated with liver damage seen on histological examination, as well as predicted liver damage, at 24 h after ALI.

CONCLUSIONS

CFD may be a useful biomarker for the prediction and measurement of ALI. There is no evidence to suggest that CFD is superior to other available noninvasive biomarkers.

A proteomic analysis of allograft rejection in rats after liver transplantation

In order to understand the allograft rejection in orthotopic liver transplantation (OLT), an allograft rejection rat model was established and studied by proteomic approach. The protein expression profiles of liver tissues were acquired by fluorescence two-dimensional difference gel electrophoresis (2D DIGE) that incorporated a pooled internal standard and reverse fluorescent labeling method. The expression levels of 27 protein spots showed significant changes in acute rejection rats. Among these spots, 19 were identified with peptide mass fingerprinting using matrix-assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF MS) after tryptic in-gel digestion. The results of the present paper could be helpful for our better understanding of allograft rejection in organ transplantation.