[Function of zinc in liver disease].

Zinc deficiency is highly prevalent in cirrhotic patients, and contributes to several clinical symptoms such as hepatic encephalopathy and liver fibrosis. Ammonia is detoxified in liver to urea through urea cycle, and is also detoxified in extrahepatic tissue to glutamine through glutamine synthetase. The reduced ability of ammonia detoxification in liver cirrhosis is ascribed to zinc deficiency, because a member of urea cycle, ornithine transcarbamylase is a zinc enzyme. In this condition, glutamine synthesis is enhanced, which enables the body, at least temporarily, to suppress the increase of ammonia. However, the glutamine is metabolized predominantly in enterocyte to ammomia and glutamate, indicating that a vicious cycle in glutamine synthesis and glutamine breakdown occurs in liver cirrhosis. Attention should be given to the clinical significance of zinc in liver diseases.