Carnitine Metabolism in Patients With Chronic Liver Disease

Carnitine metabolism was studied in 79 patients with chronic liver disease, including 22 patients with noncirrhotic liver disease and 57 patients with different types of cirrhosis (22 patients with hepatitis B– or C–associated cirrhosis, 15 patients with alcohol–induced cirrhosis, 15 patients with primary biliary cirrhosis [PBC], and 5 patients with cryptogenic cirrhosis), and compared with 28 control subjects. In comparison with control subjects, patients with noncirrhotic liver disease showed no change in the plasma carnitine pool, whereas patients with cirrhosis had a 29% increase in the long–chain acylcarnitine concentration. Analysis of subgroups of patients with cirrhosis showed that patients with alcohol–induced cirrhosis had an increase in the total plasma carnitine concentration (67.8 ± 29.5 vs. 55.2 ± 9.9 μmol/L in control subjects), resulting from increases in both the short–chain and long–chain acylcarnitine concentration. In this group of patients, the acylcarnitine concentrations showed a close correlation with the total carnitine concentration, and the total carnitine concentration with the serum bilirubin concentration. Urinary excretion of carnitine was not different between patients with noncirrhotic or cirrhotic liver disease and control patients. However, patients with PBC showed an increased urinary excretion of total carnitine (52.5 ± 40.0 vs. 28.0 ± 16.7 micromol carnitine/μmol creatinine), resulting from an increase in the fractional excretion of both free carnitine and short–chain acylcarnitine. The current studies show that patients with cirrhosis are normally not carnitine deficient. Patients with alcohol–induced cirrhosis have increased plasma carnitine concentrations, which may result from increased carnitine biosynthesis because of increased skeletal muscle protein turnover. The increase in the fractional carnitine excretion in patients with primary biliary cirrhosis may result from competition of bile acids and/or bilirubin with tubular carnitine reabsorption and/or from a reduced activity of the carnitine transporter located in the proximal tubule.