Frequency of hyperprolinemia in alcoholic liver cirrhosis: relationship to blood lactate

In alcohol-induced liver injury, hyperprolinemia has been proposed as a marker of fibrogenesis probably secondary to hyperlactacidemia. However, some studies of plasma proline in alcoholics with cirrhosis have reported normal rather than increased levels. In order to evaluate the frequency of hyperprolinemia in alcoholic liver disease and its relationship to blood lactate, we measured plasma proline levels in 145 subjects including 91 alcoholics with a spectrum of liver disease as well as 22 nonalcoholics with liver injury unrelated to alcohol. We also studied baboons fed alcohol as 50% of total calories for 1 to 4 years. Among alcoholics only 21/91 had elevated proline values. Elevations were most frequent among patients with severe hepatic decompensation (3/8), in patients with alcoholic hepatitis on liver biopsy (5/17), and in those with acute alcohol-related withdrawal, with alcohol still present in the blood (4/9). Patients with liver disease unrelated to alcohol but severe in nature also has elevations in proline (3/3). Only 4/28 patients with cirrhosis due to alcohol had elevated values, and none of the baboons fed alcohol had hyperprolinemia whether withdrawn from alcohol or not. Hyperlactacidemia was associated with hyperprolinemia, but so were depressed serum albumin values and prolongations of the prothrombin time, suggesting a general association with severe liver disease. These results reveal that hyperprolinemia occurs infrequently in patients with alcohol-induced cirrhosis and therefore does not appear to be a sensitive marker of hepatic fibrosis in these patients.