Marked elevation of serum mitochondrion-derived markers in mild models of non-alcoholic steatohepatitis in rats

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.

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.

Wild ginseng cambial meristematic cells ameliorate hepatic steatosis and mitochondrial dysfunction in high-fat diet-fed mice

Objectives

The aim of this study was to determine the protective mechanisms of wild ginseng cambial meristematic cells (CMCs) on non-alcoholic fatty liver disease in high-fat diet (HFD)-fed mice.

Methods

Male C57BL/6 mice received either normal-fat diet or HFD for 10 weeks along with wild ginseng CMCs (75, 150 and 300 mg/kg) or vehicle (0.5% carboxyl methyl cellulose) by oral administration once a day. Triglyceride and total cholesterol contents were measured in liver and serum samples. Parameters for hepatic lipid metabolism and mitochondria biogenesis were assessed.

Key findings

Treatment with wild ginseng CMCs markedly attenuated body weight, serum and hepatic lipid contents, and serum aminotransferase activity. While wild ginseng CMCs attenuated the increases in sterol regulatory element-binding transcription factor 1 (SREBP-1) and carbohydrate-responsive element-binding protein (ChREBP) expression, it enhanced the increases in carnitine palmitoyltransferase 1A (CPT1A) and peroxisome proliferator-activated receptor alpha (PPAR-α) expression. HFD decreased glutamate dehydrogenase activity and glutathione content, and increased lipid peroxidation, which were all attenuated by wild ginseng CMCs. Furthermore, wild ginseng CMCs enhanced mitochondrial biogenesis-related factors, including peroxisome proliferator-activated receptor-γ co activator 1α (PGC1α), nuclear respiratory factor 1 (NRF1) and mitochondrial transcription factor A (TFAM).

Conclusions

Wild ginseng CMCs protect against HFD-induced liver injury, which prevents lipid accumulation and mitochondrial oxidative stress, and enhances mitochondrial biogenesis.

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.

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

BACKGROUND

Although mitochondrion-derived markers such as ornithine carbamyltransferase (OCT) and glutamate dehydrogenase (GLDH) have been reported to be good markers for alcohol-induced hepatic injury, their use has been limited due to the notion that mitochondrial markers are less sensitive than cytosol-derived markers. We determined the clinical importance of mitochondrion-derived markers in the evaluation of alcohol-induced hepatotoxicity.

METHODS

Rats were administered alcohol chronically (5-30% ethanol in drinking water with or without high fat diet feeding for 15 weeks) and hepatic damages were evaluated by serum OCT and GLDH, together with other liver enzymes such as alanine aminotransferase and aspartate aminotransferase. Hepatic content of the enzymes was also evaluated in the chronic ethanol feeding model to confirm whether induction of the enzyme in the liver reflects the serum activity.

RESULTS

The serum activities of OCT and GLDH increased significantly by chronic ethanol feeding while other markers did not. Although the hepatic content of OCT and GLDH also increased, the serum activities did not correlate with the hepatic activities and the extent of increase in the liver was much less than in serum.

CONCLUSIONS

Mitochondrion-derived markers, especially OCT, appeared superior to cytosol-derived markers in the detection of alcohol-induced liver injury.