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

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.