Research ArticleAn apoptosis panel for nonalcoholic steatohepatitis diagnosis
Introduction
Nonalcoholic fatty liver disease (NAFLD) has become the most common form of chronic liver disease, currently affecting 20–30% of adults and 10% of children in the United States [1]. The spectrum of NAFLD is wide ranging from hepatic steatosis to nonalcoholic steatohepatitis (NASH) and cirrhosis [2]. Patients with hepatic steatosis appear to have a non-progressive course with more benign prognosis. Patients with NASH may progress to cirrhosis in as many as 25% of cases and suffer from its complications including portal hypertension, liver failure, and hepatocellular carcinoma [3], [4]. Liver biopsy remains the gold standard for differentiating between hepatic steatosis and NASH in addition to providing information regarding the degree of steatosis, severity of inflammatory activity, and stage of fibrosis [5]. However, liver biopsy is an invasive procedure that carries possible significant risks. There are several clinical trials investigating therapies for NASH; the results of which will hopefully provide physicians with treatment options for this condition. This underscores the importance of a screening test that identifies NASH in patients with NAFLD. Such a screening test should be simple, noninvasive, reproducible, and accurately differentiate NASH from hepatic steatosis.
Hepatocyte apoptosis plays a critical role in liver injury and NASH development [6], [7], [8]. Increase in hepatocyte apoptosis is typically present in humans as well as animal models of NASH but absent in those with hepatic steatosis [8]. Increasing evidence suggests a role for both the so called extrinsic (death receptor mediated) pathway and the intrinsic (organelle-initiated) pathway of apoptosis. Fas, a death receptor member of the TNFR family, appears to have a prominent role. Fas protein expression is increased in liver samples from NASH patients [6]. Expression of this receptor increases in experimental models of NASH and results in increased sensitivity to Fas mediated apoptosis [9]. Accumulation of free fatty acids in liver cells results in upregulation of Fas in the cell surface [9]. Although the relative importance of the two main apoptotic pathways in human NASH remains to be elucidated, in hepatocytes, both pathways tend to converge at the level of the mitochondria resulting in permeabilization of the mitochondrial outer membrane and release of multiple proteins from the mitochondrial inter-membrane space into the cytosol [10]. This results in activation of effector caspases (mainly caspase 3) which will then cleave a number of different substrates inside the cell including cytokeratin 18 (CK-18), the major intermediate filament protein in the liver, resulting in the characteristic morphologic changes of apoptosis [10]. We have previously demonstrated that caspase generated CK-18 fragments are significantly elevated in NASH patients [7]. Since the initial report, we and others have confirmed the utility of quantification of this marker for NASH diagnosis [11], [12], [13], [14]. The aim of the present study was to test a panel of circulating apoptotic markers for diagnosis of NASH.
Section snippets
Patients characteristics
The study was approved by the Cleveland Clinic Institutional Review Board, and all patients gave written informed consent prior to participation. Our initial cohort consisted of 95 consecutive patients undergoing a baseline liver biopsy for clinical suspicion of NASH by their treating hepatologists. Up to date, there are no established guidelines for performing a liver biopsy in patients with suspected NAFLD. Thus, the decision to perform the biopsy was individualized, and mostly performed due
Patient characteristics
The main clinical and serological characteristics of the initial cohort of patients are described in Table 1. The mean age of patients was 50 (± 11.6) years. The patients’ gender (50.5% male) and race (83.2% Caucasian) did not statistically differ between the two histologic groups. Patients with NASH were significantly older and had significantly higher body mass index. They also had significantly higher prevalence of hypertension, clinical diabetes and metabolic syndrome, and significantly
Discussion
Obesity and type 2 diabetes have reached epidemic proportions in most of the western world, and both conditions are strongly associated with NAFLD [2], [18], [19]. NAFLD encompasses a wide spectrum of conditions associated with over-accumulation of lipids in the liver ranging from hepatic steatosis in which there is evidence for fat accumulation without signs of liver cell injury or inflammation, to nonalcoholic steatohepatitis characterized by the accumulation of fat in the liver along with
Conflict of interest
The authors who have taken part in this study declared that they do not have anything to disclose regarding funding or conflict of interest with respect to this manuscript.
References (26)
- et al.
The natural history of nonalcoholic fatty liver disease: a population-based cohort study
Gastroenterology
(2005) - et al.
Nonalcoholic fatty liver disease: a spectrum of clinical and pathological severity
Gastroenterology
(1999) - et al.
Hepatocyte apoptosis and fas expression are prominent features of human nonalcoholic steatohepatitis
Gastroenterology
(2003) - et al.
Diet associated hepatic steatosis sensitizes to Fas mediated liver injury in mice
J Hepatol
(2003) - et al.
Cellular and molecular mechanisms of liver injury
Gastroenterology
(2008) - et al.
Cytokeratin 18 fragment levels as a noninvasive biomarker for nonalcoholic steatohepatitis in bariatric surgery patients
Clin Gastroenterol Hepatol
(2008) - et al.
Nonalcoholic steatohepatitis: a proposal for grading and staging the histological lesions
Am J Gastroenterol
(1999) - et al.
Nonalcoholic fatty liver, steatohepatitis, and the metabolic syndrome
Hepatology
(2003) - et al.
Hepatic histology in obese patients undergoing bariatric surgery
J Hepatol
(2006) - et al.
The evolution of severe steatosis after bariatric surgery is related to insulin resistance
Gastroenterology
(2006)
Sampling variability of liver biopsy in nonalcoholic fatty liver disease
Gastroenterology
Diagnosis of nonalcoholic fatty liver disease: invasive versus noninvasive
Semin Liver Dis
Nonalcoholic fatty liver disease
N Engl J Med
Cited by (154)
CD1d protects against hepatocyte apoptosis in non-alcoholic steatohepatitis
2024, Journal of HepatologyNon-invasive tests for evaluating treatment response in NAFLD
2023, Journal of HepatologyAncestral BPA exposure caused defects in the liver of medaka for four generations
2023, Science of the Total EnvironmentConcurrent HCV or fatty liver in patients with chronic hepatitis B virus infection
2023, Comprehensive Guide to Hepatitis AdvancesComprehensive molecular mechanisms and clinical therapy in nonalcoholic steatohepatitis: An overview and current perspectives
2022, Metabolism: Clinical and ExperimentalCorrelation between M30 immunochemistry and histological activity in steatohepatitis: One piece of a complex puzzle
2020, Pathology Research and Practice