Alanine aminopeptidase (AAP) activity in urine: A new marker of chronic alcohol abuse?

The purpose of this study was to evaluate a new biological marker of chronic alcohol abuse, an enzyme released from the brush border membrane of proximal tubule – urine alanine aminopeptidase (AAP). AAP was examined in 76 alcohol dependent patients undergoing detoxification, and the test results were compared with those of 37 alcoholics abstaining from alcohol for more than 6 weeks. AAP was measured in native urine (uAAP), and in eluate after removal of endogenous inhibitors (eAAP). The discriminative power of eAAP, evaluated by means of ROC analysis, proved higher than the power of uAAP. The areas under ROC curves of these tests were 0.84 and 0.78 respectively. The application of markers based on nephrotoxic influence of alcohol could be a valuable complement to the class of presently used markers, which are generally based on hepatotoxic effects of alcohol.