Only total CK-18 assays differentiated patients with minimal steatosis (<10% hepatic fat accumulation) from those with more hepatic fat (>10% steatosis). All three assays distinguished patients with steatosis from healthy controls. A selective analysis of the NAFLD subgroup demonstrated that the total CK-18 assays reliably CH5424802 concentration differentiated patients with mild NAFL from healthy or real-life controls, whereas the M30 assay could

not. The total CK-18 assays were more sensitive (100% versus 75%) and specific (80% versus 70%) than the M30 ELISA for discriminating between NAFL and NASH. The better classification of NAFL/NASH by the total CK-18 assays was not a byproduct of superior fibrosis staging because the fibrosis severity was similar (generally low) in these patients. Although the NASH patients tended to have higher ALT levels than the NAFL patients, a regression analysis revealed that total CK-18 levels predicted NASH independently of ALT levels, whereas cleaved CK-18 levels did not. The aggregated data demonstrate that a noninvasive measure of various types of hepatocyte death (total CK-18) is a better biomarker of related liver pathology than a test that merely reflects apoptotic severity

(cleaved CK-18). This finding has a number of fundamental Y 27632 implications. First, it supports the concept that dying liver epithelial cells provide key fibrosis stimuli. Completely dead hepatocytes have long been implicated in the pathogenesis of liver fibrosis because of increased fibrogenic activity selleck chemical in hepatic stellate cells that have phagocytosed apoptotic hepatocytes.3 More recent data show that dying (but viable) liver epithelial cells produce and release soluble factors that promote liver fibrosis. Diverse insults that sensitize hepatocytes to death (e.g., an infection

with hepatitis C virus,4 an exposure to agents that induce endoplasmic reticulum stress,5 or an inhibition of autocrine viability factors6) induce them to generate damage-associated molecules. These include hedgehog ligands, which are morphogens stimulating wound-healing mechanisms that promote myofibroblastic cell outgrowth, immune cell infiltration, and the accumulation of liver epithelial progenitors (with fibrogenic activity).7, 8 It is thus not surprising that an assay with improved sensitivity and specificity for detecting hepatocyte death would provide better sensitivity and specificity for responses that are triggered by all dying hepatocytes (and not simply a subset of dead cells). Second, the latter concept raises the intriguing possibility that dying hepatocytes promote hepatic steatosis (rather than vice versa as currently believed). This possibility is supported by evidence showing that hepatic steatosis occurs transiently in remnant livers after partial hepatectomy, which is another process stimulating wound-healing responses to promote liver regeneration.