Abstract
A rapid, non-invasive urine test for early stage alcohol-induced liver disease (ALD) would permit risk stratification and treatment of high-risk individuals before ALD leads to irreversible liver damage and death. Urinary metabolomic studies were carried out to identify ALD-associated metabolic biomarkers using Ppara-null mouse model that is susceptible to ALD development on chronic alcohol consumption. Two successive studies were conducted to evaluate the applicability of mass spectrometry-based metabolomics in identification of ALD-specific signatures and to examine the robustness of these biomarkers against genetic background. Principal components analysis of ultraperformance liquid chromatography coupled with electrospray ionization quadrupole time-of-flight mass spectrometry (UPLC-ESI-QTOFMS)-generated urinary metabolic fingerprints showed that alcohol-treated wild-type and Ppara-null mice could be distinguished from control animals. It also showed that a combined endogenous biomarker panel helps to identify subjects with ALD as well as those at risk of developing ALD even without any information on alcohol intake or genetics. Quantitative analysis showed that increased excretion of indole-3-lactic acid and phenyllactic acid was a genetic background-independent signature exclusively associated with ALD pathogenesis in Ppara-null mice that showed liver pathologies similar to those observed in early stages of human ALD. These findings demonstrated that mass spectrometry-based metabolomic analysis could help in the identification of ALD-specific signatures, and that metabolites such as indole-3-lactic acid and phenyllactic acid, may serve as robust noninvasive biomarkers for early stages of ALD.