Progress in the enzyme diagnosis of liver disease: reality or illusion?

The antifibrogenic effect of etanercept on development of liver cirrhosis induced by thioacetamide in rats

Liver cirrhosis is an elevating cause of morbidity and mortality worldwide. TNF-α/TNF-R1 signal is implicated in progression of many liver diseases. This study provides histological and ultrastructural view that clarifies the effect of etanercept, a TNF-α inhibitor, on development of thioacetamide (TAA)-induced liver cirrhosis and the accompanied hemosiderosis in rats, highlighting the implication and distribution pattern of hepatic TNF-R1. Sixty male albino rats (Rattus norvegicus) were equally randomized into three groups. Group I served as the control. Liver cirrhosis was triggered in the other two groups by intraperitoneal injection of TAA twice a week for five months. Group II received TAA only, while group III subcutaneously injected with etanercept one hour before TAA, along five months. At the end of the experiment, blood was collected for biochemical analysis and livers were excised for histological, immunohistochemical, and electron microscopical preparations. Rats treated with TAA only developed hepatic cirrhosis accompanied by massive deposition of hemosiderin; strong and widespread expression of hepatic TNF-R1 in sinusoidal endothelial cells (SECs), Kupffer cells (KCs), and many hepatocytes; and frequent appearance of fibrogenic, plasma, and mast cells, at the ultrastructural level. By contrast, administration of etanercept diminished the expression of TNF-R1, attenuated the accumulation of collagen and hemosiderin, and preserved the hepatic histoarchitecture. In conclusion, TNF-α signal via TNF-R1 may be implicated in the mechanism of fibrogenesis and the associated hemosiderosis. Etanercept may provide a promising therapeutic approach not only for attenuating the progression of fibrogenesis, but also for hepatic iron overload-associated disorders.

Biomarkers in HCV Infection

Liver-related biomarkers have been developed and validated mainly in patients with chronic hepatitis C for the prediction of liver fibrosis or cirrhosis, which is a final pathway of chronic liver injury. They are noninvasive, traceable, and easy-to-use. Biomarkers provide implications related to screening, diagnosis, treatment, and prognosis of chronic hepatitis. For the improvement of performance and coverage, biomarker panels, imaging biomarkers, and even genetic biomarkers have been developed. With the advancement of genomics and proteomics, earlier and more precise prediction is expected in the near future. In this review, multiple biomarker panels for the estimation of the degree of fibrosis in chronic hepatitis C, biomarkers for the screening and diagnosis of hepatitis C, biomarkers for the treatment of hepatitis C, biomarkers for the prediction of complications related to the chronic hepatitis C, and future perspectives will be summarized.

Biochemical diagnosis of liver disease

It is important that clinicians and laboratorians, including clinical chemists and pathologists, recognize and understand the clinical significance of abnormal liver function tests. The liver regulates many important metabolic functions. Hepatic injury is associated with distortion of these metabolic functions. Hepatic disease can be evaluated and diagnosed by determining serum concentrations of a number of serum analytes. Many serum analytes exist to assist in the biochemical diagnosis of liver disease. The focus of this paper is on the analytes which are associated with hepatic necrosis, cholestasis, defects in excretion and end stage hepatic disease which results in decreased synthetic function. The abnormalities of these serum analytes will be correlated with the important types of liver disease.

Association between posttraumatic stress disorder following myocardial infarction and liver enzyme levels: a prospective study

BACKGROUND

Research in rodents demonstrated that psychological stress increases circulating levels of alanine transaminase, aspartate transaminase, and alkaline phosphatase reflecting liver injury. Moreover, chronic posttraumatic stress disorder and transaminases predicted coronary heart disease.

AIMS

To investigate the hypothesis that severity of posttraumatic stress disorder following myocardial infarction would prospectively relate to liver enzymes.

METHODS

Study participants were 24 patients (mean 59+/-7 years, 79% men) with an interviewer-rated diagnosis of posttraumatic stress disorder caused by an index myocardial infarction 3+/-3 months before. After a mean follow-up of 26+/-6 months, patients had a clinical interview to reassess posttraumatic stress disorder severity, a medical history, and blood collected to determine liver enzymes.

RESULTS

Total posttraumatic stress disorder symptoms assessed at study entry prospectively predicted plasma levels of alanine transaminase (r=.47, p=.031) and alkaline phosphatase (r=.57, p=.004), but not of aspartate transaminase (p=.15), controlling for follow-up duration and antidepressant use. Total posttraumatic stress disorder symptoms assessed at follow-up were associated with alanine transaminase (r=.72, p=.004), aspartate transaminase (r=.60, p=.018), and alkaline phosphatase (r=.64, p=.001) in the 16 patients who had maintained diagnostic posttraumatic stress disorder, but not in all 24 patients.

CONCLUSIONS

The severity of posttraumatic stress disorder following myocardial infarction was associated with mild increase in liver enzyme levels, suggesting that chronic psychological stress relates to hepatic damage in humans. This might help to explain the previously observed increased cardiovascular risk in chronically traumatized individuals.

Induction of endogenous pathways by antiepileptics and clinical implications

The aim of this study was to review modifications of the endogenous pathways (e.g. enzyme elevations, normal body constituent depletion or higher formation/excretion of endogenous metabolites) which could be ascribed to enzyme induction by antiepileptic drugs (AEDs). Information on older (e.g. phenobarbital, phenytoin and carbamazepine) and newer drugs (where information is available) is discussed together with clinical implications. The enzymes involved in the endogenous pathways and induced by the AEDs will not be limited to the hepatic microsomal enzymes; extrahepatic enzymes and/or enzymes present in other subcellular fractions will also be discussed, if pertinent. The induction of endogenous pathways by AEDs has been taken into account in the past, but much less emphasis has been given compared with the extensive literature on induction by AEDs of the metabolism of concomitantly administered drugs, either of the same or of different classes. Not all of the endogenous pathways examined and induced by AEDs appear to result in serious clinical consequences (e.g. induction of hepatic ALP, increased excretion of d-glucaric acid or of 6 beta-hydroxycortisol). In some cases, induction of some pathways (e.g. increase of high-density lipoprotein cholesterol or of conjugated bilirubin) might even be a beneficial side-effect, however enzyme induction is considered rather a detrimental aspect for an AED, as induction is generally a broad and a non-specific phenomenon. The new AEDs have generally less induction potential than the older agents. Yet some (felbamate, topiramate, oxcarbazepine and lamotrigine) have the potential for inducing enzymes, whereas others (levetiracetam, gabapentin and vigabatrin) appear to be completely devoid of enzyme inducing characteristics, at least as far as the enzymes investigated are concerned.

Diagnosis and monitoring of hepatic injury. II. Recommendations for use of laboratory tests in screening, diagnosis, and monitoring

Purpose: To review information on the use of laboratory tests in screening, diagnosis, and monitoring of acute and chronic hepatic injury.

Data Sources and Study Selection: A MEDLINE search was performed for key words related to hepatic diseases, including acute hepatitis, chronic hepatitis, alcoholic hepatitis, cirrhosis, hepatocellular carcinoma, and etiologic causes. Abstracts were reviewed, and articles discussing use of laboratory tests selected for review. Additional articles were selected from the references.

Guideline Preparation and Review: Drafts of the guidelines were posted on the Internet, presented at the AACC Annual Meeting in 1999, and reviewed by experts. Areas requiring further amplification or literature review were identified for further analysis. Specific recommendations were made based on analysis of published data and evaluated for strength of evidence and clinical impact.

Recommendations: Although many specific recommendations are made in the guidelines, only some summary recommendations are listed here. In acute hepatic injury, prothrombin time and, to a lesser extent, total bilirubin are the best indicators of severity of disease. Although ALT is useful for detecting acute and chronic hepatic injury, it is not related to severity of acute hepatic injury and only weakly related to severity of chronic hepatic injury. Specific tests of viral markers should be the initial differential tests in both acute and chronic hepatic injury; when positive, they are also useful for monitoring recovery from hepatitis B and C.

Diagnosis and Monitoring of Hepatic Injury. I. Performance Characteristics of Laboratory Tests

Purpose: To review information on performance characteristics for tests that are commonly used to identify acute and chronic hepatic injury.

Data Sources and Study Selection: A MEDLINE search was performed for key words related to hepatic tests, including quality specifications, aminotransferases, alkaline phosphatase, γ-glutamyltransferase, bilirubin, albumin, ammonia, and viral markers. Abstracts were reviewed, and articles discussing performance of laboratory tests were selected for review. Additional articles were selected from the references.

Guideline Preparation and Review: Drafts of the guidelines were posted on the Internet, presented at the AACC Annual Meeting in 1999, and reviewed by experts. Areas requiring further amplification or literature review were identified for further analysis. Specific recommendations were made based on analysis of published data and evaluated for strength of evidence and clinical impact. The drafts were also reviewed by the Practice Guidelines Committee of the American Association for the Study of Liver Diseases and approved by the committee and the Association’s Council.

Recommendations: Although many specific recommendations are made in the guidelines, some summary recommendations are discussed here. Alanine aminotransferase is the most important test for recognition of acute and chronic hepatic injury. Performance goals should aim for total error of <10% at the upper reference limit to meet clinical needs in monitoring patients with chronic hepatic injury. Laboratories should have age-adjusted reference limits for enzymes in children, and gender-adjusted reference limits for aminotransferases, γ-glutamyltransferase, and total bilirubin in adults. The international normalized ratio should not be the sole method for reporting results of prothrombin time in liver disease; additional research is needed to determine the reporting mechanism that best correlates with functional impairment. Harmonization is needed for alanine aminotransferase activity, and improved standardization for hepatitis C viral RNA measurements.

Serum transaminase elevations as indicators of hepatic injury following the administration of drugs

During the preclinical, early clinical, late-stage clinical, and postmarketing phases of the pharmaceutical discovery and development process, one important aspect of drug safety assessment involves monitoring for possible drug-induced hepatic injury. Hepatic injuries vary in nature from direct, intrinsic effects that are observed in most recipients and more than one species to rare idiosyncratic responses seen only in a few clinical subjects. Histological types of injuries vary from hepatocellular to hepatobiliary with multiple cellular effects characteristic of each type. Of the various clinical laboratory markers for hepatic injury, serum transaminases, especially alanine aminotransferase (ALT), are the most universally important indicators for studies ranging from early preclinical animal testing to postmarketing patient monitoring. This review examines the characteristics of hepatic toxicity that result in serum ALT changes, the differences in the etiology of hepatic responses which govern when liver injury is most likely to be detected during the four phases of the drug discovery and development process, and those modulating factors which affect the utility of ALT as a dependable marker of hepatic injury in clinical populations. The paper concludes with a summary of some ancillary methods for early preclinical screening such as in vitro metabolism and toxicity assays, gene and protein expression analysis, and some strategies for enhancing the probability for the early detection of idiosyncratic hepatotoxic responses which are infrequent but significant factors in the safety assessment process.