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

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.

Markers of acute rejection and graft acceptance in liver transplantation

The evaluation of the immunosuppression state in liver transplanted patients is crucial for a correct post-transplant management and a major step towards the personalisation of the immunosuppressive therapy. However, current immunological monitoring after liver transplantation relies mainly on clinical judgment and on immunosuppressive drug levels, without a proper assessment of the real suppression of the immunological system. Various markers have been studied in an attempt to identify a specific indicator of graft rejection and graft acceptance after liver transplantation. Considering acute rejection, the most studied markers are pro-inflammatory and immunoregulatory cytokines and other proteins related to inflammation. However there is considerable overlap with other conditions, and only few of them have been validated. Standard liver tests cannot be used as markers of graft rejection due to their low sensitivity and specificity and the weak correlation with the severity of histopathological findings. Several studies have been performed to identify biomarkers of tolerance in liver transplanted patients. Most of them are based on the analysis of peripheral blood samples and on the use of transcriptional profiling techniques. Amongst these, NK cell-related molecules seem to be the most valid marker of graft acceptance, whereas the role CD4⁺CD25⁺Foxp3⁺ T cells has still to be properly defined.

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.