Ornithine carbamyltransferase is a sensitive marker for alcohol-induced liver injury

Green Tea Catechin EGCG Ameliorates Thioacetamide-Induced Hepatic Encephalopathy in Rats via Modulation of the Microbiota-Gut-Liver Axis

SCOPE

Existing research suggests that (-)-epigallocatechin-3-gallate (EGCG), which is a natural tea catechin active substance, can protect against liver injury. However, its mechanism for hepatic encephalopathy (HE) treatment is still unclear. In this study, the role of EGCG in the amelioration of HE rats and the effect on the microbiota-gut-liver axis are mainly analyzed.

METHODS AND RESULTS

Thioacetamide (TAA) is employed to induce the HE model in rats. The results of open field test show that EGCG restores locomotor activity and exploratory behavior. Histological and biochemical results demonstrate that EGCG ameliorates brain and liver damage, decreases the expression of pro-inflammatory cytokines, and increases the activity of antioxidant enzymes. Meanwhile, EGCG modulates the Nrf2 pathway and TLR4/NF-κB pathway to mitigate TAA-induced oxidative stress and inflammatory responses. Immunohistochemistry reveals protection of the intestinal barrier by EGCG upregulating the expression of occludin and zonula occludens-1. Furthermore, serum levels of ammonia and LPS are reduced. 16S rRNA analysis shows that EGCG treatment increases the abundance of beneficial bacteria (e.g., Bifidobacterium, Lactobacillus, and Limosilactobacillus).

CONCLUSION

The above results reveal that EGCG has anti-oxidative stress and anti-inflammatory effects, and ameliorates the condition through the microbiota-gut-liver axis, with potential for the treatment of HE.

Circadian oscillation expression of ornithine carbamoyltransferase and its significance in sleep disturbance

Ornithine transcarbamylases (OTC), a key enzyme in urea cycle, is an important marker for some liver injury or diseases. However, whether OTC could be a sensitive indicator for liver dysfunction under sleep disturbance condition remains unknown. The present study aimed to explore the circadian oscillation expression of OTC and its significance in disturbed sleep condition. Sleep disturbance was conducted by a sleep deprivation (SD) instrument. Our results found that SD for 72h induced abnormal increasing of OTC levels in serum and liver of rats. And, serum OTC concentration and liver OTC expression could return to normal levels after recovery sleep following SD. Moreover, hepatic OTC expression showed circadian oscillation in day and night, characterized with occurrence of a peak between ZT 22 and ZT 2, and a nadir between ZT 14 and ZT 18. Further analysis suggested the existence of ROR response element (RORE) for potential RORɑ binding sites in OTC promoter region, and elevated RORɑ expression in rat livers under sleep disturbance condition. Additionally, oscillation expression of OTC induced by serum shock in HepG2 cells was characterized with a peak occurred between ZT 12 and ZT 16, and RORɑ knockdown at ZT 16 significantly lowered OTC expression. The results together indicate that OTC is closely correlated with circadian clock, and could be a sensitive indicator for sleep disturbance stress.

Evaluation of conventional and non-conventional biomarkers of liver toxicity in greenhouse workers occupationally exposed to pesticides

The liver plays a prominent role in maintenance of homeostasis and is the major organ for xenobiotic metabolism, including pesticides. Conventional liver function tests are widely used to assess hepatocellular and biliary system dysfunction by measuring serum levels of aminotransferases (ALT, AST) and cholestasis enzymes (alkaline phosphatase -ALP- and γ-glutamyl transferase -GGT-), respectively. Although these tests are not entirely specific for liver damage, their specificity increases when measured concurrently, but still have limited usefulness to predict early liver dysfunction. Hence, non-conventional biomarkers may have a better performance for the early detection of biochemical hepatotoxicity with a greater specificity and sensitivity. A cross-sectional study with a follow-up component was conducted on 175 greenhouse workers regularly exposed to pesticides under integrated production system, and 91 controls living in the same geographical area. All individuals were evaluated for conventional (ALT, AST, ALP, GGT) and non-conventional biomarkers of hepatotoxicity (ornithine transcarbamylase (-OTC-), Arginase-1 -ARG1- and glutathione S-transferase alpha -GSTα-) over two periods of the same crop season, one of high pesticide exposure and other of low exposure. A slight increase in AST was observed in greenhouse workers relative to controls, suggestive of subtle hepatocellular toxicity. Although ALP, ARG1 and GST-α levels were decreased in greenhouse workers, this might be related to a potential homeostatic mechanism that regulates their expression. Altogether, these findings do not represent unambiguous evidence of liver dysfunction (e.g., hepatocellular or biliary system impairment) but may be the result of the low-toxicity pesticides used by greenhouse workers.

Biomarkers associated with binaprofen‑induced liver injury

Drug‑induced liver injury (DILI) is a common hepatic disease. The identification of biomarkers for DILI prediction is critical for rational drug use. The aim of the present study was to investigate liver injury caused by binaprofen and identify proteins that may serve as early biomarkers to predict DILI. For in vivo DILI assays, zebrafish were exposed to acetaminophen (APAP) and binaprofen for 12‑96 h before lethal concentration 50 (LC50), histopathological analysis, conventional and non‑conventional biomarker measurements were conducted. In vitro assays were performed in cultured liver cells; after 6‑24 h treatment with APAP and binaprofen the same measurements were conducted as aforementioned. The in vivo assays indicated that the LC50 of APAP was 5.2 mM, whereas the LC50 of binaprofen was 1.2 mM; 12‑48 h post‑treatment, liver cells exhibited mild to moderate vacuolization in a time‑ and concentration‑dependent manner in response to both drugs. During this time, conventional and non‑conventional biomarkers were also altered in a time‑ and concentration‑dependent manner; however, alterations in the levels of non‑conventional biomarkers occurred at an earlier time point compared with conventional biomarkers. The in vitro assays indicated that the half maximal inhibitory concentration (IC50) of APAP was 16.2 mM, whereas the IC50 of binaprofen was 5.3 mM; 12‑48 h post‑treatment, cultured liver cells exhibited mild to moderate swelling in a time‑ and concentration‑dependent manner. Alterations in the levels of conventional and non‑conventional biomarkers were similar to those observed in the in vivo assays. As a non‑steroidal anti‑inflammatory drug, binaprofen exhibited expected levels of liver toxicity in in vitro and in vivo assays, which were similar to APAP. Total bile acid and argininosuccinate lyase were identified as early biomarkers, which could accurately predict onset of binaprofen‑induced liver injury.

Proteomic Profiling of Liver and Plasma in Chronic Ethanol Feeding Model of Hepatic Alcohol Dehydrogenase-Deficient Deer Mice

BACKGROUND

Chronic alcohol abuse, a major risk factor for such diseases as hepatitis and cirrhosis, impairs hepatic alcohol dehydrogenase (ADH; key ethanol [EtOH]-metabolizing enzyme). Therefore, differentially altered hepatic and plasma proteomes were identified in chronic EtOH feeding model of hepatic ADH-deficient (ADH^- ) deer mice to understand the metabolic basis of alcoholic liver disease (ALD).

METHODS

ADH^- deer mice were fed 3.5 g% EtOH via Lieber-DeCarli liquid diet daily for 3 months and histology of the liver assessed. Liver and plasma proteins were separated by 2-dimensional gel electrophoresis. The proteins differentially expressed were identified by matrix-assisted laser desorption ionization-time of flight mass spectrometry.

RESULTS

Histology of the liver showed panlobular steatosis and infiltration of T lymphocytes. Using the criteria of ≥1.5 for fold change (p-value ≤0.05) with expectation value (E ≤10^-3 ) and protein score (≥64), 18 proteins in the livers and 5 in the plasma of EtOH-fed mice were differentially expressed and identified. Prolyl 4-hydroxylase, cytochrome b-5, endo A cytokeratin, ATP synthase, heat-shock 70 kD proteins, enoyl CoA hydratase, stress-70 protein, peroxiredoxin 1, and ornithine carbamoyl transferase were up-regulated in the livers. However, carbonic anhydrase 3, mitochondrial ATP synthase, aldolase 2, actin γ, laminin receptor, and carbamoyl phosphate synthase were down-regulated. Contrary to the increased expression of creatine kinase M-type, a decreased expression of serine protease inhibitor A3A precursor, sulfated glycoprotein-2 (clusterin), and apolipoprotein E isoforms were found in the plasma of EtOH group.

CONCLUSIONS

Chronic EtOH feeding in ADH^- deer mice causes steatosis and infiltration of T lymphocytes in the livers along with increased expression of proteins involved in endoplasmic reticulum (ER) stress, fibrosis, fatty acid β oxidation and biogenesis, and decreased expression of proteins involved in ATP synthesis, carbohydrate metabolism, in cell regulation and architecture. Reduced expression of various carrier proteins as found in the plasma of EtOH group has a biomarker potential.

Activity of the liver enzyme ornithine carbamoyltransferase (OTC) in blood: LC-MS/MS assay for non-invasive diagnosis of ornithine carbamoyltransferase deficiency

Background:

Liver enzymes are released from hepatocytes into circulation and their activity can be measured in the blood. We examined whether the plasma activity of the liver enzyme ornithine carbamoyltransferase, determined by a novel liquid chromatography-mass spectrometry (LC-MS/MS) assay, could be utilized for the detection of OTC deficiency (OTCD), an X-linked inborn error of the urea cycle.

Methods:

The plasma ornithine carbamoyltransferase (OTC) activity was assayed in the reverse reaction using isotopically labeled citrulline-d4 as a substrate and by determination of the product, ornithine-d4, by LC-MS/MS analysis.

Results:

The plasma OTC activity in the controls was in the range of 111–658 pkat/L (n=49, median 272 pkat/L), and the activity increased linearly with serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activities in patients with hepatopathy. The OTC activity was subsequently determined in 32 individuals carrying mutations in the OTC gene, and OTC/ALT and OTC/AST ratios were calculated to account for the degree of hepatopathy, which is a common finding in OTCD. The OTC/ALT ratio enabled clear differentiation of OTCD hemizygotes (n=11, range 0–69×10−6) from controls (504–3440×10−6). This ratio also enabled the detection of 11 of 12 symptomatic heterozygotes (range 38–794×10−6), while this marker did not allow for reliable differentiation of asymptomatic heterozygotes (n=9) from controls.

Conclusions:

LC-MS/MS assay of plasma OTC activity enabled the detection of all hemizygous and the majority of symptomatic heterozygous OTCD patients in the tested cohort. This study demonstrates that non-invasive assay of enzymes expressed predominantly in the liver could be used as an alternative approach for diagnosing inborn errors of metabolism.

In vivo and ex vivo measurements: noninvasive assessment of alcoholic fatty liver using 1H-MR spectroscopy

PURPOSE

We aimed to evaluate the ability of 1H-magnetic resonance spectroscopy (1H-MRS) to detect and quantify hepatic fat content in vivo and ex vivo in an experimental rat model of alcoholic fatty liver using histopathology, biochemistry, and laboratory analyses as reference.

METHODS

Alcoholic fatty liver was induced within 48 hours in 20 Lewis rats; 10 rats served as control. Intrahepatic fat content determined by 1H-MRS was expressed as the percent ratio of the lipid and water peaks and was correlated with intrahepatic fat content determined histologically and biochemically. Liver enzymes were measured in serum.

RESULTS

Fatty liver could be detected in vivo as well as ex vivo using 1H-MRS, in all 20 animals. Histologic analysis showed a fatty liver in 16 of 20 animals. Histology and 1H-MRS results were highly correlated (in vivo, r=0.93, P = 0.0005; ex vivo, r=0.92, P = 0.0006). Also a strong correlation was noted between in vivo 1H-MRS measurements and the fat content determined biochemically (r=0.96, P = 0.0003). Ex vivo results showed a similarly strong correlation between 1H-MRS and biochemistry (r=0.89, P = 0.0011).

CONCLUSION

1H-MRS can be carried out in ex vivo models, as well as in vivo, to detect and quantify intrahepatic fat content in the acute fatty liver.

Involvement of Ornithine Carbamoyltransferase in the Progression of Chronic Hepatitis C and Liver Cirrhosis

Background: The involvement of serum ornithine carbamoyltransferase (OCT) in the progression of chronic hepatitis and liver cirrhosis is unclear. Methods: A total 256 patients with chronic hepatitis C and 5 healthy controls were examined. Serum OCT concentrations were measured by enzyme-linked immunosorbent assay. Serum OCT concentrations were compared with serum cytokine and chemokine levels, and with disease severity and development of hepatocellular carcinoma (HCC). Results: The median OCT concentrations were 21.8 ng/ml for healthy controls, 36.7 ng/ml for F0 stage disease, 48.7 ng/ml for F1 stage, 77.9 ng/ml for F2 stage, 104.8 ng/ml for F3 stage, and 121.4 ng/ml for F4 stage. OCT concentrations were correlated with aspartate aminotransferase, alanine aminotransferase, γ-glutamyl transpeptidase, platelet counts, indocyanine green retention rate at 15 min, prothrombin times, the molar ratio of branched chain amino acids to tyrosine, and tyrosine. Furthermore, there were significant correlations among OCT concentrations and IP10 and IL18 levels. There were weak correlations between serum OCT concentrations and liver histology. The cumulative incidence of HCC in the high-OCT concentration group (≥75.3 ng/ml) was higher than that in the low-OCT concentration group. Conclusion: The measurement of serum OCT concentration may provide a useful marker of disease severity, and thus could be a useful marker for a high risk of HCC occurrence.

Investigation of ornithine carbamoyltransferase as a biomarker of liver cirrhosis

OBJECTIVE

Ornithine carbamoyltransferase (OCT) is a liver-specific mitochondrial matrix enzyme and potential biomarker of liver fibrosis. This study investigated the OCT levels in patients with chronic liver disease with or without cirrhosis in order to assess the usefulness of OCT as a biomarker of cirrhosis.

METHODS

The subjects included 440 Japanese patients with chronic liver disease and 80 control subjects. The patients were divided into two groups, those with and without cirrhosis, both of which were further stratified into high-OCT and low-OCT subgroups.

RESULTS

In the non-cirrhosis group, the patients with non-alcoholic steatohepatitis (NASH), alcoholic liver disease, primary biliary cirrhosis and primary sclerosing cholangitis (PSC) comprised the high-OCT subgroup, while the patients with hepatitis B, hepatitis C and autoimmune hepatitis formed the low-OCT subgroup. There were significant differences in the OCT levels, OCT/aspartate aminotransferase ratios and OCT/alanine transaminase (ALT) ratios between these two subgroups (p<0.001). The same findings were observed in the cirrhosis group. The OCT levels were markedly higher in the cirrhosis group than in the non-cirrhosis group, particularly among the patients with PSC (p<0.001). The most useful biomarker for predicting cirrhosis was the OCT/ALT ratio in the patients with hepatitis C and NASH and the OCT level in patients with PSC.

CONCLUSION

The OCT level differs among patients with different chronic liver diseases. The role of OCT should be further evaluated in order to improve our understanding of the pathogenesis of these diseases. The OCT level is a useful surrogate marker of cirrhosis, particularly in PSC patients.

Detection of a fatty liver after binge drinking: correlation of MR-spectroscopy, DECT, biochemistry and histology in a rat model

RATIONALE AND OBJECTIVES

The purpose of this study was to evaluate the possibility of detecting a fatty liver after binge drinking in an animal model using (1)H magnetic resonance spectroscopy ((1)H-MRS), dual-energy computed tomography (DECT), biochemistry, and the gold standard of histology.

MATERIALS AND METHODS

In 20 inbred female Lewis rats, an alcoholic fatty liver was induced; 20 rats served as controls. To simulate binge drinking, each rat was given a dose of 9.3 g/kg body weight 50% ethanol twice, with 24 hours between applications. Forty-eight hours after the first injection, DECT and (1)H-MRS were performed. Fat content as well as triglycerides were also determined histologically and biochemically, respectively. To assess specific liver enzymes, blood was drawn from the orbital venous plexus.

RESULTS

In all 20 animals in the experimental group, fatty livers were detected using (1)H-MRS, DECT, and biochemical and histologic analysis. The spectroscopic fat/water ratio and the biochemical determination were highly correlated (r = 0.892, P < .05). A significant correlation was found between (1)H-MRS and histologic analysis (r = 0.941, P < .001). Also, a positive linear correlation was found between the dual-energy computed tomographic density of ΔHU and the biochemical (r = 0.751, P < .05) and histologic (r = 0.786, P < .001) analyses.

CONCLUSIONS

Quantification of hepatic fat content on (1)H-MRS showed high correlation with histologic and biochemical steatosis determination. In comparison to DECT, it is more suitable to reflect the severity of acute fatty liver.

Predicting and preventing acute drug-induced liver injury: what's new in 2010?

IMPORTANCE OF THE FIELD

The field of drug-induced liver injury (DILI) continues to expand in terms of global registries and with new agents added every year. Given the need to improve on our current methods of preclinical testing and monitoring for DILI during both clinical trials and in the post-approval setting, there is increasing research aimed at better understanding why injury occurs and who is most susceptible. To this end, the active pursuit of biomarkers that will predict injury prior to its occurrence and genetic testing that can identify individuals at risk of DILI continue to be at the forefront.

AREAS COVERED IN THIS REVIEW

While alanine aminotransferase (ALT) testing remains the workhorse of biochemical monitoring, it only detects hepatic injury after it has occurred and, therefore, is not a true predictor. The utility and shortcomings of ALT and other liver tests are reviewed along with a synopsis of several other candidate biomarkers that are being studied. In addition, we review the recent data supporting testing for genetic predisposition to DILI and how identifying clinical risk factors may translate into better means for preventing DILI.

WHAT THE READER WILL GAIN

We update the basis on which age and gender are considered risk factors for DILI, and review the latest reports detailing the association of several candidate genes and the development of DILI in a susceptible patient. Human leukocyte antigen-B*5701 is closely linked to the hypersensitivity reaction seen with abacavir, and such screening has been successfully incorporated into HIV treatment around the globe and offers the promise that testing for other genetic markers will soon become a routine part of clinical practice. At present, candidate genes conferring specific susceptibility to DILI have been identified for a relatively few agents (e.g., flucloxacillin, amoxicillin-clavulanate, ximelagatran and isoniazid), but many more are under study. Preventing DILI often comes down to avoiding the use of potentially hepatotoxic drugs in certain situations, and we review the clinical scenarios in which this is most relevant.

TAKE HOME MESSAGE

Given the number and range of studies aimed at identifying predictors of DILI, the focus of this review is to summarize what we consider to be the most relevant new information published on the topics of clinical and genetic factors that predispose to DILI, the use of biomarkers as predictors of acute DILI, along with advances in prevention strategies.

Serum ornithine carbamyltransferase reflects hepatic damage in diabetic obese mice

BACKGROUND AND AIM

As ornithine carbamyltransferase (OCT) has proved to be a sensitive serum marker in the detection of hepatotoxicity in several models, it is important to confirm its application to the diagnosis of non-alcoholic fatty liver disease.

METHODS

C57BL/6, KK-Ta and KK-Ay mice were fed a high-fat diet for 8 weeks and serum enzyme markers were examined. Serum OCT and alanine aminotransferase (ALT) were also measured in diabetic obese ob/ob and db/db mice fed a normal diet. Liver damage in these mice was evaluated by the hepatic content of tumor necrosis factor-alpha.

RESULTS

Serum levels of OCT increased in KK-Ay fed a high-fat diet compared with the normal diet-fed group, whereas C57BL/6 and KK-Ta mice were not affected. In ob/ob mice, the relative increase was always greater in OCT than in ALT. In contrast, in db/db mice, the relative increase was always greater in ALT. Hepatic tumor necrosis factor-alpha was significantly elevated in ob/ob mice, but not in db/db mice.

CONCLUSIONS

Serum OCT seemed to reflect tumor necrosis factor-alpha-mediated hepatic damage when compared with ALT in diabetic obese mice and could be useful in the application for non-alcoholic fatty liver disease with features of metabolic syndrome, such as obesity and diabetes.

Mechanism-based bioanalysis and biomarkers for hepatic chemical stress

Adverse drug reactions, in particular drug-induced hepatotoxicity, represent a major challenge for clinicians and an impediment to safe drug development. Novel blood or urinary biomarkers of chemically-induced hepatic stress also hold great potential to provide information about pathways leading to cell death within tissues. The earlier pre-clinical identification of potential hepatotoxins and non-invasive diagnosis of susceptible patients, prior to overt liver disease is an important goal. Moreover, the identification, validation and qualification of biomarkers that have in vitro, in vivo and clinical transferability can assist bridging studies and accelerate the pace of drug development. Drug-induced chemical stress is a multi-factorial process, the kinetics of the interaction between the hepatotoxin and the cellular macromolecules are crucially important as different biomarkers will appear over time. The sensitivity of the bioanalytical techniques used to detect biological and chemical biomarkers underpins the usefulness of the marker in question. An integrated analysis of the biochemical, molecular and cellular events provides an understanding of biological (host) factors which ultimately determine the balance between xenobiotic detoxification, adaptation and liver injury. The aim of this review is to summarise the potential of novel mechanism-based biomarkers of hepatic stress which provide information to connect the intracellular events (drug metabolism, organelle, cell and whole organ) ultimately leading to tissue damage (apoptosis, necrosis and inflammation). These biomarkers can provide both the means to inform the pharmacologist and chemist with respect to safe drug design, and provide clinicians with valuable tools for patient monitoring.