Relationship between blood lactic acid and serum proline in alcoholic liver cirrhosis

Abstract

One of the distinctive features of liver damage in alcoholic patients as compared to other chronic liver diseases, is the presence of hyperprolinemia. Since lactic acid may regulate the disposition of proline by the liver due to its inhibitory effect on proline oxidase, the first enzyme in the catabolic pathway of proline, this hyperprolinemia could be related to the hyperlactacidemia found in alcoholic cirrhotics. We therefore measured serum proline and blood lactic acid in 42 alcoholic cirrhotic patients and 20 posthepatitic cirrhotics. We also determined these parameters in 7 alcoholic cirrhotics that received colchicine treatment for 1 yr and whose proline values returned to normal, and in a group of 11 normal non-alcoholic volunteers during acute intoxication with ethanol. In the alcoholic cirrhotics blood lactate and serum proline values were significantly increased when compared with normals and with nonalcoholic cirrhotic patients. A linear correlation (r = 0.973) was found when both tests were compared. In the alcoholic cirrhotics on colchicine, both serum proline and blood lactate decreased to almost normal values. In normal volunteers alcohol intake was accompanied by a small but significant increase in blood lactic acid. However, this elevation was transient and in general less than 2 SD of the mean control value. These findings confirm that elevated serum proline values are characteristic of alcoholic liver disease. We postulate that hyperprolinemia of the alcoholic cirrhotic patient is secondary to the elevation in blood lactic acid, and that colchicine lowers serum proline by modifying the metabolism of lactic acid. We also suggest that blood lactic acid and serum proline values could be used as possible markers of liver fibrogenesis in alcoholic liver disease. © 1981.