Proteomics Indicates Lactate Dehydrogenase Is Prognostic in Acetaminophen-Induced Acute Liver Failure Patients and Reveals Altered Signaling Pathways

Serum proteomics of adults with acute liver failure provides mechanistic insights and attractive prognostic biomarkers

Background & Aims

Acute liver failure (ALF) is defined as rapid onset coagulopathy and encephalopathy in patients without a prior history of liver disease. We performed untargeted and targeted serum proteomics to delineate processes occurring in adult patients with ALF and to identify potential biomarkers.

Methods

Sera of 319 adult patients with ALF (∼50% acetaminophen [APAP]-related cases) were randomly selected from admission samples of the multicenter USA Acute Liver Failure Study Group consortium and subdivided into discovery/validation cohorts. They were analyzed using untargeted proteomics with mass spectroscopy and a serum cytokine profiling and compared with 30 healthy controls. The primary clinical outcome was 21-day transplant-free survival. Single-cell RNAseq data mapped biomarkers to cells of origin; functional enrichment analysis provided mechanistic insights. Novel prognostic scores were compared with the model for end-stage liver disease and ALFSG prognostic index scores.

Results

In the discovery cohort, 117 proteins differed between patients with ALF and healthy controls. There were 167 proteins associated with APAP-related ALF, with the majority being hepatocyte-derived. Three hepatocellular proteins (ALDOB, CAT, and PIGR) robustly and reproducibly discriminated APAP from non-APAP cases (AUROCs ∼0.9). In the discovery cohort, 37 proteins were related to 21-day outcome. The key processes associated with survival were acute-phase response and hepatocyte nuclear factor 1α signaling. SERPINA1 and LRG1 were the best individual discriminators of 21-day transplant-free survival in both cohorts. Two models of blood-based proteomic biomarkers outperformed the model for end-stage liver disease and ALFSG prognostic index and were reproduced in the validation cohort (AUROCs 0.83-0.86) for 21-day transplant-free survival.

Conclusions

Proteomics and cytokine profiling identified new, reproducible biomarkers associated with APAP etiology and 21-day outcome. These biomarkers may improve prognostication and understanding of the etiopathogenesis of ALF but need to be independently validated.

Impact and implications

Acute liver failure (ALF) is a sudden, and severe condition associated with high fatality. More sensitive and specific prognostic scores are urgently needed to facilitate decision-making regarding liver transplantation in patients with ALF. Our proteomic analysis uncovered marked differences between acetaminophen and non-acetaminophen-related ALF. The identification of routinely measurable biomarkers that are associated with 21-day transplant-free survival and the derivation of novel prognostic scores may facilitate clinical management as well as decisions for/against liver transplantation. Further studies are needed to quantify less abundant proteins. Although we used two cohorts, our findings still need to be independently and prospectively validated.

Alpha-fetoprotein and carbohydrate antigen 19-9 as prognostic biomarkers in acute liver failure: A retrospective study

ObjectiveTo investigate the clinical significance of alpha-fetoprotein and carbohydrate antigen 19-9 as potential predictors of outcomes in patients with acute liver failure.MethodsWe conducted a retrospective analysis of 208 patients with acute liver failure admitted to the intensive care unit between 2009 and 2023. Serum alpha-fetoprotein and carbohydrate antigen 19-9 levels were measured on Days 1 and 3, and their prognostic value was evaluated using logistic regression and receiver operating characteristic curve analyses. Patients were stratified by etiologies to assess biomarker performance across different causes of acute liver failure.ResultsNonsurvivors had significantly lower alpha-fetoprotein levels and higher carbohydrate antigen 19-9 levels than survivors on Days 1 and 3 (all p < 0.05). Alpha-fetoprotein levels increased over time in both groups, whereas carbohydrate antigen 19-9 levels increased in nonsurvivors and decreased in survivors. The combination of carbohydrate antigen 19-9 with the Model for End-Stage Liver Disease score significantly improved prognostic accuracy, with an area under the curve value of 0.828, compared with 0.784 for alpha-fetoprotein combined with Model for End-Stage Liver Disease score. Etiology-specific analysis revealed that carbohydrate antigen 19-9 showed the best predictive performance in acetaminophen-induced acute liver failure (area under the curve value = 0.885), whereas alpha-fetoprotein showed better predictive performance in viral hepatitis-associated acute liver failure (area under the curve value = 0.880).ConclusionsAlpha-fetoprotein is a protective prognostic factor, whereas carbohydrate antigen 19-9 enhances outcome prediction, particularly when combined with Model for End-Stage Liver Disease score. Etiology-specific biomarker performance supports tailored prognostic approaches in the management of acute liver failure.

The endothelial growth factor Angiopoietin-2 is an accurate prognostic biomarker in patients with acetaminophen-induced acute liver failure

Background and Aims

Acetaminophen (APAP) overdose is the leading individual cause of acute liver failure (ALF) in the United States, with many patients rapidly progressing to hyperacute liver failure. While hepatocytes are the main target of APAP toxicity, endothelial cells (ECs) are also affected. However, the efficacy of an endothelial-specific biomarker to predict patient outcomes remains unknown. This study aimed to evaluate angiopoietin-2 (ANGPT2) as a prognostic biomarker for poor outcomes in APAP-induced ALF.

Approach and Results

Using human and mouse single-cell RNA sequencing (scRNAseq) data, we found that ANGPT2 expression was significantly elevated in ECs following APAP exposure. We measured circulating ANGPT2 levels from two independent APAP-ALF cohorts: a Phoenix cohort (n=43) and a cohort from the ALF Study Group (n=80). In the Phoenix cohort, ANGPT2 levels were significantly higher in non-survivors with an AUROC of 0.938. In the ALFSG cohort, we stratified patients based on time of symptom onset finding that ANGPT2 had improved prognostic value in early-presenting patients, with day 1 and day 3 AUC values of 0.825 and 0.918, respectively. Lastly, we combined the patient cohorts (n=110) finding that ANGPT2 alone or in combination with MELD outperformed MELD alone based on AUC (ANGPT2: 0.87, MELD 0.83, ANGPT2+MELD 0.90).

Conclusions

ANGPT2 is a promising prognostic biomarker for APAP-induced ALF, reflecting endothelial stress and offering superior predictive value compared to MELD alone, especially in early-presenting patients. Its capacity for predicting poor outcomes underscores its value in improving patient prognosis and therapeutic intervention strategies in APAP overdose cases.

Lay Summary

Accidental or intentional overdosing on acetaminophen can cause liver injury and in severe cases acute liver failure. Under these circumstances, receiving a liver transplant may be the only remaining therapeutic option. However, a liver transplant is a major surgery and commits the patient to a lifetime of anti-rejection medication. Because there is only a limited time window to decide who will recover and who needs a transplant to survive, prognostic biomarkers are essential to identify transplant candidates as early as possible after the overdose. In this study we discovered that plasma levels of the endothelial growth factor angiopoietin-2 can accurately predict at the peak of injury who will need a liver transplant to survive. In addition, this biomarker can be rapidly measured, which allows the data to be available for clinical decision making.

Highlights

Acetaminophen-induced liver injury can cause hyper-acute liver failure within 3 to 7 days with a high probability of negative outcome.Under these conditions, a liver transplant may be the only therapeutic option.In two independent cohorts, angiopoietin 2 was identified as an early prognostic biomarker for poor outcome.Angiopoietin can more accurately inform clinical management during the initial stages of hospital presentation than the MELD score.

Stratifying and predicting progression to acute liver failure during the early phase of acute liver injury

Acute liver failure (ALF) is a serious disease that progresses from acute liver injury (ALI) and that often leads to multiorgan failure and ultimately death. Currently, effective treatment strategies for ALF, aside from transplantation, remain elusive, partly because ALI is highly heterogeneous. Furthermore, clinicians lack a quantitative indicator that they can use to predict which patients hospitalized with ALI will progress to ALF and the need for liver transplantation. In our study, we retrospectively analyzed data from 319 patients admitted to the hospital with ALI. By applying a machine-learning approach and by using the SHapley Additive exPlanations (SHAP) algorithm to analyze time-course blood test data, we identified prothrombin time activity percentage (PT%) as a biomarker reflecting individual ALI status. Unlike previous studies predicting the need for liver transplantation in patients with ALF, our study focused on PT% dynamics. Use of this variable allowed us to stratify the patients with highly heterogeneous ALI into six groups with distinct clinical courses and prognoses, i.e. self-limited, intensive care-responsive, or intensive care-refractory patterns. Notably, these groups were well predicted by clinical data collected at the time of admission. Additionally, utilizing mathematical modeling and machine learning, we assessed the predictability of individual PT% dynamics during the early phase of ALI. Our findings may allow for optimizing medical resource allocation and early introduction of tailored individualized treatment, which may result in improving ALF prognosis.

Identification of multiple complications as independent risk factors associated with 1-, 3-, and 5-year mortality in hepatitis B-associated cirrhosis patients

BACKGROUND

Hepatitis B-associated cirrhosis (HBC) is associated with severe complications and adverse clinical outcomes. This study aimed to develop and validate a predictive model for the occurrence of multiple complications (three or more) in patients with HBC and to explore the effects of multiple complications on HBC prognosis.

METHODS

In this retrospective cohort study, data from 121 HBC patients treated at Nanjing Second Hospital from February 2009 to November 2019 were analysed. The maximum follow-up period was 10.75 years, with a median of 5.75 years. Eight machine learning techniques were employed to construct predictive models, including C5.0, linear discriminant analysis (LDA), least absolute shrinkage and selection operator (LASSO), k-nearest neighbour (KNN), gradient boosting decision tree (GBDT), support vector machine (SVM), generalised linear model (GLM) and naive Bayes (NB), utilising variables such as medical history, demographics, clinical signs, and laboratory test results. Model performance was evaluated via receiver operating characteristic (ROC) curve analysis, residual analysis, calibration curve analysis, and decision curve analysis (DCA). The influence of multiple complications on HBC survival time was assessed via Kaplan‒Meier curve analysis. Furthermore, LASSO and univariable and multivariable Cox regression analyses were conducted to identify independent prognostic factors for overall survival (OS) in patients with HBC, followed by ROC, C-index, calibration curve, and DCA curve analyses of the constructed prognostic nomogram model. This study utilized bootstrap resampling for internal validation and employed the Medical Information Mart for Intensive Care IV (MIMIC-IV) database for external validation.

RESULTS

The GBDT model exhibited the highest area under the curve (AUC) and emerged as the optimal model for predicting the occurrence of multiple complications. The key predictive factors included posthospitalisation fever (PHF), body mass index (BMI), retinol binding protein (RBP), total bilirubin (TB) levels, and eosinophils (EOS). Kaplan-Meier analysis revealed that patients with multiple complications had significantly worse OS than those with fewer complications. Additionally, multivariable Cox regression analysis, informed by least absolute shrinkage and LASSO selection, identified hepatocellular carcinoma (HCC), multiple complications, and lactate dehydrogenase (LDH) levels as independent prognostic factors for OS. The prognostic model demonstrated 1-year, 3-year, and 5-year OS ROC AUCs of 0.802, 0.793, and 0.817, respectively. For the internal validation cohort, the corresponding AUC values were 0.797, 0.832, and 0.835. In contrast, the external validation cohort yielded a 1-year ROC AUC of 0.707. Calibration curves indicated good consistency of the model, and DCA demonstrated the model's clinical utility, showing high net benefits within certain threshold ranges. Compared with the univariable models, the multivariable ROC curves indicated higher AUC values for this prognostic model, and the model also possessed the best c-index.

CONCLUSION

The GBDT prediction model provides a reliable tool for the early identification of high-risk HBC patients prone to developing multiple complications. The concurrent occurrence of multiple complications is an independent prognostic factor for OS in patients with HBC. The constructed prognostic model demonstrated remarkable predictive performance and clinical applicability, indicating its crucial role in enhancing patient outcomes through timely and targeted interventions.

Mechanistic insights from a pilot exploratory study of the dynamic proteomic changes during plasma exchange in patients with acute liver failure

BACKGROUND & AIMS

Therapeutic plasma exchange (PEX) has shown potential in improving transplant-free survival in acute liver failure (ALF) however the mechanism of action is not understood. This exploratory study aimed to elucidate the circulating proteomic changes associated with PEX in ALF to provide insight into mechanisms underlying the benefit of this therapy.

METHODS

Consecutive patients admitted with ALF between June 2019 and August 2020 were enrolled. Patients received either standard medical treatment (n = 5) or PEX (n = 5). Plasma samples were collected at multiple time points and analysed using the Olink Proximity Extension Assay. Comparative analyses included healthy controls and Octaplas batches.

RESULTS

Biomarker results were available for 54 samples: Octaplas batches (n = 7), healthy controls (n = 6), ALF-standard medical treatment (n = 8), and ALF-PEX (n = 33). Proteomic analysis of 177 biomarkers revealed marked baseline differences between ALF and healthy controls, with ALF patients exhibiting lower levels of proteins secreted by the liver and higher levels of inflammatory cytokines and growth factors. Longitudinal analysis showed several distinct patterns with PEX. Proteins including carboxylesterase-1, hepatocyte growth factor, fetuin B, IL-6 and IL-10 showed differential expression patterns longitudinally, indicating some of the potential underlying mechanisms and therapeutic effects of PEX.

CONCLUSIONS

PEX in ALF patients leads to dynamic proteomic changes, reflecting its multifaceted role in modulating inflammation, liver regeneration and replacing essential proteins. These findings provide insight into some of the changes in circulating blood proteins and underlying mechanisms of PEX.

Novel reduced heteropolyacid nanoparticles for effective treatment of drug-induced liver injury by manipulating reactive oxygen and nitrogen species and inflammatory signals

With the rapid advancements in biomedicine, the use of clinical drugs has surged sharply. However, potential hepatotoxicity limits drug exploitation and widespread usage, posing serious threats to patient health. Hepatotoxic drugs disrupt liver enzyme levels and cause refractory pathological damage, creating a challenge in the application of diverse first-line drugs. The activation and deterioration of reactive oxygen and nitrogen species (RONS) and inflammatory signals are key pathological mechanisms of drug-induced liver injury (DILI). Herein, a novel reduced heteropolyacid nanoparticle (RNP) has been developed, possessing high RONS-scavenging ability, strong anti-inflammatory activity, and excellent biosafety. These features enable it to swiftly restore the redox and immune balance of the liver. Intravenous administration of RNP effectively scavenged RONS storm, reversing liver oxidative stress and restoring normal mitochondrial membrane potential and function. Furthermore, by inhibiting c-Jun-N-terminal kinase phosphorylation, RNP facilitated the restoration of nuclear factor erythroid 2-related factor 2-mediated endogenous antioxidant signaling, ultimately rescuing the liver function and tissue morphology in acetaminophen-induced DILI mice. Crucially, the high biocompatible RNP exhibited superior efficacy in the DILI mouse model compared to the clinical antioxidant N-acetylcysteine. This targeted therapeutic approach, tailored to address the onset and progression of DILI, offers valuable new insights into controlling the condition and restoring liver structure and function.

Assessment of Subacute Toxicity of Ulexite in Rats: Behavioral, Hematological, and Biochemical Insights

Ulexite (UX), a naturally occurring borate mineral, has gained interest for its diverse industrial applications, yet its toxicological profile remains inadequately characterized. This study aimed to evaluate the subacute toxicity of UX in rats, focusing on behavioral, hematological, and biochemical parameters. Rats were administered UX via gavage at doses of 10, 30, and 300 mg/kg for 7 days. No mortality or significant signs of toxicity were observed, although body weight measurements indicated a notable reduction in the UX-treated groups compared to controls. Behavioral assessments demonstrated increased exploratory activity in the 10 and 300 mg/kg UX treated groups, suggesting low anxiety levels. Likewise, hematological analysis revealed that 30 and 300 mg/kg UX led a significant (P < 0.001) increase in hematocrit and a decrease in mean corpuscular hemoglobin concentration (P < 0.001), indicating potential changes in erythropoiesis. Additionally, serum biochemistry showed elevated aspartate aminotransferase (P < 0.05), lactate dehydrogenase (P < 0.001), and uric acid levels (P < 0.01), suggesting liver stress. Histopathological examinations indicated dose-dependent alterations, with mild hepatocellular degeneration and neuronal changes observed at the highest dose. Also, MN levels in the blood of rats exposed to 10 and 30 mg/kg UX showed no significant differences. These results suggest that UX is relatively safe at lower doses, though higher exposures may pose health risks. Further research is warranted to elucidate the mechanisms underlying UX-induced effects and to evaluate its safety for therapeutic and occupational applications.

Human quad liver-on-chip system as a tool toward bridging the gap between animals and humans regarding toxicology and pharmacology of a cannabidiol-rich cannabis extract

Cannabidiol (CBD) is a major phytocannabinoid from Cannabis sativa. It is currently widely available and widely used in the USA, but despite its rapid progress to market, the pharmacology and toxicology of both CBD and cannabidiol-rich cannabis extracts (CRCE) remain largely unknown. The goals of this study were to investigate the potential of a novel human microphysiological system to emulate CRCE-induced hepatotoxicity and pharmacological properties demonstrated in animal models. For this purpose, C57BL6/J male mice were subjected to dosing with either 0, 61.5, 184.5, or 615 mg/kg of CRCE for 10 days. The liver-on-chip system, incorporating human primary hepatocytes, sinusoidal endothelial cells, as well as Kupffer and stellate cells was subjected to 0, 300, 1,200, or 4,400 ng/mL of CRCE (8 h exposure followed by 16 h washout) for 5 days. Administration of CRCE in mice resulted in nearly 4-fold elevations of plasma ALT at 615 mg/kg (p < 0.01) and a dose-dependent decrease in intrahepatic miR-122. Elevated levels of ALT, paralleled by decreased intrahepatic and increased effluent levels of miR-122, were also observed in the liver-on-chip, although these results were not statistically significant. Exposure to CRCE resulted in a robust and dose-dependent induction of key cytochrome P450 enzymes, namely Cyp1a2, Cyp2b6 (CYP2B10), Cyp2e1, and Cyp2c9 (CYP2C19) in both mouse livers and liver-on-chip. The results of this study demonstrate the congruence between the responses observed in mouse and human liver-on-chip experimental systems and provide evidence of the potential microphysiological systems hold for translating animal data into clinical practice.

The Role of Mechanistic Biomarkers in Understanding Acetaminophen Hepatotoxicity in Humans

Our understanding of the fundamental molecular mechanisms of acetaminophen (APAP) hepatotoxicity began in 1973 to 1974, when investigators at the US National Institutes of Health published seminal studies demonstrating conversion of APAP to a reactive metabolite that depletes glutathione and binds to proteins in the liver in mice after overdose. Since then, additional groundbreaking experiments have demonstrated critical roles for mitochondrial damage, oxidative stress, nuclear DNA fragmentation, and necrotic cell death as well. Over the years, some investigators have also attempted to translate these mechanisms to humans using human specimens from APAP overdose patients. This review presents those studies and summarizes what we have learned about APAP hepatotoxicity in humans so far. Overall, the mechanisms of APAP hepatotoxicity in humans strongly resemble those discovered in experimental mouse and cultured hepatocyte models, and emerging biomarkers also suggest similarities in liver repair. The data not only validate the first mechanistic studies of APAP-induced liver injury performed 50 years ago but also demonstrate the human relevance of numerous studies conducted since then. SIGNIFICANCE STATEMENT: Human studies using novel translational, mechanistic biomarkers have confirmed that the fundamental mechanisms of acetaminophen (APAP) hepatotoxicity discovered in rodent models since 1973 are the same in humans. Importantly, these findings have guided the development and understanding of treatments such as N-acetyl-l-cysteine and 4-methylpyrazole over the years. Additional research may improve not only our understanding of APAP overdose pathophysiology in humans but also our ability to predict and treat serious liver injury in patients.

Central Mechanisms of Acetaminophen Hepatotoxicity: Mitochondrial Dysfunction by Protein Adducts and Oxidant Stress

Acetaminophen (APAP) is an analgesic and antipyretic drug used worldwide, which is safe at therapeutic doses. However, an overdose can induce liver injury and even liver failure. Mechanistic studies in mice beginning with the seminal papers published by B.B. Brodie's group in the 1970s have resulted in important insight into the pathophysiology. Although the metabolic activation of APAP with generation of a reactive metabolite, glutathione depletion, and protein adduct formation are critical initiating events, more recently, mitochondria have come into focus as an important target and decision point of cell death. This review provides a comprehensive overview of the induction of mitochondrial superoxide and peroxynitrite formation and its propagation through a mitogen-activated protein kinase cascade, the mitochondrial permeability transition pore opening caused by iron-catalyzed protein nitration, and the mitochondria-dependent nuclear DNA fragmentation. In addition, the role of adaptive mechanisms that can modulate the pathophysiology, including autophagy, mitophagy, nuclear erythroid 2 p45-related factor 2 activation, and mitochondrial biogenesis, are discussed. Importantly, it is outlined how the mechanisms elucidated in mice translate to human hepatocytes and APAP overdose patients, and how this mechanistic insight explains the mechanism of action of the clinically approved antidote N-acetylcysteine and led to the recent discovery of a novel compound, fomepizole, which is currently under clinical development. SIGNIFICANCE STATEMENT: Acetaminophen (APAP)-induced liver injury is the most frequent cause of acute liver failure in western countries. Extensive mechanistic research over the last several decades has revealed a central role of mitochondria in the pathophysiology of APAP hepatotoxicity. This review article provides a comprehensive discussion of a) mitochondrial protein adducts and oxidative/nitrosative stress, b) mitochondria-regulated nuclear DNA fragmentation, c) adaptive mechanisms to APAP-induced cellular stress, d) translation of cell death mechanisms to overdose patients, and e) mechanism-based antidotes against APAP-induced liver injury.

Role of lactate and lactate metabolism in liver diseases (Review)

Lactate is a byproduct of glycolysis, and before the Warburg effect was revealed (in which glucose can be fermented in the presence of oxygen to produce lactate) it was considered a metabolic waste product. At present, lactate is not only recognized as a metabolic substrate that provides energy, but also as a signaling molecule that regulates cellular functions under pathophysiological conditions. Lactylation, a post‑translational modification, is involved in the development of various diseases, including inflammation and tumors. Liver disease is a major health challenge worldwide. In normal liver, there is a net lactate uptake caused by gluconeogenesis, exhibiting a higher net lactate clearance rate compared with any other organ. Therefore, abnormalities of lactate and lactate metabolism lead to the development of liver disease, and lactate and lactate metabolism‑related genes can be used for predicting the prognosis of liver disease. Targeting lactate production, regulating lactate transport and modulating lactylation may be potential treatment approaches for liver disease. However, currently there is not a systematic review that summarizes the role of lactate and lactate metabolism in liver diseases. In the present review, the role of lactate and lactate metabolism in liver diseases including liver fibrosis, non‑alcoholic fatty liver disease, acute liver failure and hepatocellular carcinoma was summarized with the aim to provide insights for future research.

Proteomic study of gamma-oryzanol preventive effect on a diet-induced non-alcoholic fatty liver disease model

Nonalcoholic fatty liver disease (NAFLD) is the most common liver disease associated with obesity and diabetes prevalence. The use of natural compounds has become an attractive approach to prevent NAFLD and its progression. Gamma-oryzanol (Orz) is a natural compound whose beneficial effects on chronic metabolic diseases have been reported. Therefore, we aimed to investigate the preventive effect of Orz on the hepatic proteome in a diet induced NAFLD model. Wistar rats were randomly distributed into three experimental groups (n=6/group) according to the diet received for 30 weeks: Control group, high sugar-fat (HSF) group, and HSF+Orz group. The isolated Orz was added to the chow at the dose of 0.5% (w/w). We evaluated the nutritional profile, characterized the presence of steatosis through histological analysis, triglyceride content in liver tissue and hepatic inflammation. Next, we performed label-free quantitative proteomics of hepatic tissue. Network analysis was performed to describe involved protein pathways. NAFLD induction was characterized by the presence of hepatic steatosis. Orz prevented lipid accumulation. The compound prevented alterations of the hepatic proteome, highlighted by the modulation of lipid metabolism, inflammation, oxidative stress, xenobiotic metabolism, and the sirtuin signaling pathway. It was possible to identify key altered pathways of NAFLD pathophysiology modulated by Orz which may provide insights into NAFLD treatment targets.

Biomarker discovery in acetaminophen hepatotoxicity: leveraging single-cell transcriptomics and mechanistic insight

INTRODUCTION

Acetaminophen (APAP) overdose is the leading cause of drug-induced liver injury and can cause a rapid progression to acute liver failure (ALF). Therefore, the identification of prognostic biomarkers to determine which patients will require a liver transplant is critical for APAP-induced ALF.

AREAS COVERED

We begin by relating the mechanistic investigations in mouse models of APAP hepatotoxicity to the human APAP overdose pathophysiology. We draw insights from the established sequence of molecular events in mice to understand the progression of events in the APAP overdose patient. Through this mechanistic understanding, several new biomarkers, such as CXCL14, have recently been evaluated. We also explore how single-cell RNA sequencing, spatial transcriptomics, and other omics approaches have been leveraged for identifying novel biomarkers and how these approaches will continue to push the field of biomarker discovery forward.

EXPERT OPINION

Recent investigations have elucidated several new biomarkers or combination of markers such as CXCL14, a regenerative miRNA signature, a cell death miRNA signature, hepcidin, LDH, CPS1, and FABP1. While these biomarkers are promising, they all require further validation. Larger cohort studies analyzing these new biomarkers in the same patient samples, while adding these candidate biomarkers to prognostic models will further support their clinical utility.

The Evolution of Circulating Biomarkers for Use in Acetaminophen/Paracetamol-Induced Liver Injury in Humans: A Scoping Review

Acetaminophen (APAP) is a widely used drug, but overdose can cause severe acute liver injury. The first reports of APAP hepatotoxicity in humans were published in 1966, shortly after the development of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) as the first biomarkers of liver injury as opposed to liver function. Thus, the field of liver injury biomarkers has evolved alongside the growth in APAP hepatotoxicity incidence. Numerous biomarkers have been proposed for use in the management of APAP overdose patients in the intervening years. Here, we comprehensively review the development of these markers from the 1960s to the present day and briefly discuss possible future directions.

Hepatic pyruvate and alanine metabolism are critical and complementary for maintenance of antioxidant capacity and resistance to oxidative insult

OBJECTIVE

Mitochondrial pyruvate is a critical intermediary metabolite in gluconeogenesis, lipogenesis, and NADH production. As a result, the mitochondrial pyruvate carrier (MPC) complex has emerged as a promising therapeutic target in metabolic diseases. Clinical trials are currently underway. However, recent in vitro data indicate that MPC inhibition diverts glutamine/glutamate away from glutathione synthesis and toward glutaminolysis to compensate for loss of pyruvate oxidation, possibly sensitizing cells to oxidative insult. Here, we explored this in vivo using the clinically relevant acetaminophen (APAP) overdose model of acute liver injury, which is driven by oxidative stress.

METHODS

We used pharmacological and genetic approaches to inhibit MPC2 and alanine aminotransferase 2 (ALT2), individually and concomitantly, in mice and cell culture models and determined the effects on APAP hepatotoxicity.

RESULTS

We found that MPC inhibition sensitizes the liver to APAP-induced injury in vivo only with concomitant loss of alanine aminotransferase 2 (ALT2). Pharmacological and genetic manipulation of neither MPC2 nor ALT2 alone affected APAP toxicity, but liver-specific double knockout (DKO) significantly worsened APAP-induced liver damage. Further investigation indicated that DKO impaired glutathione synthesis and increased urea cycle flux, consistent with increased glutaminolysis, and these results were reproducible in vitro. Finally, induction of ALT2 and post-treatment with dichloroacetate both reduced APAP-induced liver injury, suggesting new therapeutic avenues.

CONCLUSIONS

Increased susceptibility to APAP toxicity requires loss of both the MPC and ALT2 in vivo, indicating that MPC inhibition alone is insufficient to disrupt redox balance. Furthermore, the results from ALT2 induction and dichloroacetate in the APAP model suggest new metabolic approaches to the treatment of liver damage.

The impact of vaccine-linked chemotherapy on liver health in a mouse model of chronic Trypanosoma cruzi infection

BACKGROUND

Chagas disease, chronic infection with Trypanosoma cruzi, mainly manifests as cardiac disease. However, the liver is important for both controlling parasite burdens and metabolizing drugs. Notably, high doses of anti-parasitic drug benznidazole (BNZ) causes liver damage. We previously showed that combining low dose BNZ with a prototype therapeutic vaccine is a dose sparing strategy that effectively reduced T. cruzi induced cardiac damage. However, the impact of this treatment on liver health is unknown. Therefore, we evaluated several markers of liver health after treatment with low dose BNZ plus the vaccine therapy in comparison to a curative dose of BNZ.

METHODOLOGY

Female BALB/c mice were infected with a bioluminescent T. cruzi H1 clone for approximately 70 days, then randomly divided into groups of 15 mice each. Mice were treated with a 25mg/kg BNZ, 25μg Tc24-C4 protein/ 5μg E6020-SE (Vaccine), 25mg/kg BNZ followed by vaccine, or 100mg/kg BNZ (curative dose). At study endpoints we evaluated hepatomegaly, parasite burden by quantitative PCR, cellular infiltration by histology, and expression of B-cell translocation gene 2(BTG2) and Peroxisome proliferator-activated receptor alpha (PPARα) by RT-PCR. Levels of alanine transaminase (ALT), aspartate transaminase (AST), alkaline phosphatase (ALP) and lactate dehydrogenase (LDH) were quantified from serum.

RESULTS

Curative BNZ treatment significantly reduced hepatomegaly, liver parasite burdens, and the quantity of cellular infiltrate, but significantly elevated serum levels of ALT, AST, and LDH. Low BNZ plus vaccine did not significantly affect hepatomegaly, parasite burdens or the quantity of cellular infiltrate, but only elevated ALT and AST. Low dose BNZ significantly decreased expression of both BTG2 and PPARα, and curative BNZ reduced expression of BTG2 while low BNZ plus vaccine had no impact.

CONCLUSIONS

These data confirm toxicity associated with curative doses of BNZ and suggest that while dose sparing low BNZ plus vaccine treatment does not reduce parasite burdens, it better preserves liver health.

Crosstalk between lactic acid and immune regulation and its value in the diagnosis and treatment of liver failure

Liver failure is a common clinical syndrome of severe liver diseases, which belongs to one of the critical medical conditions. Immune response plays a leading role in the pathogenesis of liver failure. Lactic acid as a target for the treatment and prediction of liver failure has not attracted enough attention. Since the emergence of the concept of "histone lactation," lactic acid has shown great promise in immune response and escape. Therefore, targeted lactic acid may be a reliable agent to solve immune and energy metabolism disorders in liver failure. Based on the relationship between lactic acid and immune response, the cross-talk between lactic acid metabolism, its compounds, and immune regulation and its significance in the diagnosis and treatment of liver failure were expounded in this article to provide new ideas for understanding and treating liver failure.

Amniotic Membrane and Its Derivatives: Novel Therapeutic Modalities in Liver Disorders

The liver is a vital organ responsible for metabolic and digestive functions, protein synthesis, detoxification, and numerous other necessary functions. Various acute, chronic, and neoplastic disorders affect the liver and hamper its biological functions. Most of the untreated liver diseases lead to inflammation and fibrosis which develop into cirrhosis. The human amniotic membrane (hAM), the innermost layer of the fetal placenta, is composed of multiple layers that include growth-factor rich basement membrane, epithelial and mesenchymal stromal cell layers. hAM possesses distinct beneficial anti-fibrotic, anti-inflammatory and pro-regenerative properties via the secretion of multiple potent trophic factors and/or direct differentiation into hepatic cells which place hAM-based therapies as potential therapeutic strategies for the treatment of chronic liver diseases. Decellularized hAM is also an ideal scaffold for liver tissue engineering as this biocompatible niche provides an excellent milieu for cell proliferation and hepatocytic differentiation. Therefore, the current review discusses the therapeutic potential of hAM and its derivatives in providing therapeutic solutions for liver pathologies including acute liver failure, metabolic disorders, liver fibrosis as well as its application in liver tissue engineering.

The impact of vaccine-linked chemotherapy on liver health in a mouse model of chronic Trypanosoma cruzi infection

Background

Chagas disease, chronic infection with Trypanosoma cruzi, mainly manifests as cardiac disease. However, the liver is important for both controlling parasite burdens and metabolizing drugs. Notably, high doses of anti-parasitic drug benznidazole (BNZ) causes liver damage. We previously showed that combining low dose BNZ with a prototype therapeutic vaccine is a dose sparing strategy that effectively reduced T. cruzi induced cardiac damage. However, the impact of this treatment on liver health is unknown. Therefore, we evaluated several markers of liver health after treatment with low dose BNZ plus the vaccine therapy in comparison to a curative dose of BNZ.

Methodology

Female BALB/c mice were infected with a bioluminescent T. cruzi H1 clone for approximately 70 days, then randomly divided into groups of 15 mice each. Mice were treated with a 25mg/kg BNZ, 25μg Tc24-C4 protein/5μg E6020-SE (Vaccine), 25mg/kg BNZ followed by vaccine, or 100mg/kg BNZ (curative dose). At study endpoints we evaluated hepatomegaly, parasite burden by quantitative PCR, cellular infiltration by histology, and expression of B-cell translocation gene 2(BTG2) and Peroxisome proliferator-activated receptor alpha (PPARα) by RT-PCR. Levels of alanine transaminase (ALT), aspartate transaminase (AST), alkaline phosphatase (ALP) and lactate dehydrogenase (LDH) were quantified from serum.

Results

Curative BNZ treatment significantly reduced hepatomegaly, liver parasite burdens, and the quantity of cellular infiltrate, but significantly elevated serum levels of ALT, AST, and LDH. Low BNZ plus vaccine did not significantly affect hepatomegaly, parasite burdens or the quantity of cellular infiltrate, but only elevated ALT and AST. Low dose BNZ significantly decreased expression of both BTG2 and PPARα, and curative BNZ reduced expression of BTG2 while low BNZ plus vaccine had no impact.

Conclusions

These data confirm toxicity associated with curative doses of BNZ and suggest that the dose sparing low BNZ plus vaccine treatment better preserves liver health.

LDH and the MELD-LDH in Severe Acute Liver Injury and Acute Liver Failure: Preliminary Confirmation of a Novel Prognostic Score for Risk Stratification

BACKGROUND

Acute liver failure (ALF) is a devastating condition with high mortality. Currently, liver transplantation is the only life-saving treatment, but the decision to transplant is difficult due to the rapid progression of ALF and persistent shortage of donor organs. Biomarkers that predict death better than current prognostics could help. To our surprise, proteomics recently revealed that lactate dehydrogenase (LDH) is prognostic in ALF by itself and in a novel form of the model for end-stage liver disease (MELD) score called the MELD-LDH. The purpose of this study was to confirm our proteomics results in a larger population.

METHODS

We reviewed laboratory data from 238 patients admitted to the University of Arkansas for Medical Sciences Medical Center with a diagnosis of ALF and biochemical evidence of acute liver failure over a 12-year period, as well as subset of 170 patients with encephalopathy.

RESULTS

LDH was strikingly elevated in the nonsurvivors at the time of peak injury. Receiver operating characteristic (ROC) curve analyses revealed that LDH by itself could discriminate between survivors and nonsurvivors on the first day of hospitalization, although not as well as the MELD and MELD-LDH scores that performed alike. Importantly, however, LDH by itself performed similarly to the MELD at the time of peak injury and the MELD-LDH score moderately outperformed both. The MELD-LDH score also had greater sensitivity and negative predictive value than the MELD and the King's College Criteria.

CONCLUSIONS

The results support our prior finding that LDH and the MELD-LDH score predict death and therefore transplant need in ALF patients.

Low intensity pulsed ultrasound reduces liver inflammation caused by fatigue exercise

Low-intensity pulsed ultrasound (LIPUS) has been shown to have many benefits, such as inhibiting inflammation, stimulating cell proliferation and differentiation, promoting angiogenesis, and so on. So, can exercise fatigue induced liver inflammation be effectively relieved by LIPUS? If possible, what is the possible mechanism? This study first investigated the effect of different intensity exercise on liver inflammation. Rats were divided into three groups: normal control group, exercise fatigue group, and aerobic exercise group. The results showed that aerobic exercise increases both anti-inflammatory factors and pro-inflammatory factors, while fatigue exercise decreases anti-inflammatory factors and increases pro-inflammatory factors, leading to severe liver injury and fibrosis. Then, we investigated the therapeutic effect of LIPUS on liver inflammation caused by exercise fatigue. Starting from the 6th week, the liver was irradiated with LIPUS of 80 mW/cm² for 20 min/d after daily exercise for 7 weeks. The results showed that LIPUS significantly decreased liver injury and fibrosis, significantly up-regulated the expression of STAT6, IL-13, and its receptors IL-13Rα1, and down regulated the expression of NF-κBp65 in exercise fatigue rats. These results indicate that LIPUS can reduce fatigue-induced liver inflammation, and the mechanism is related to the regulation of the IL-13/STAT6/NF-κBp65 pathway.