The conversion of d-xylose into d-threitol in patients without liver disease and in patients with portal liver cirrhosis

An oral d-xylose tolerance test was carried out on 12 patients with portal liver cirrhosis, on 7 patients with active fatty liver disease and on 29 subjects without liver diseases. d-Xylose and d-threitol were measured by means of gasliquid chromatography.Fifteen percent of the d-xylose dose excreted in urine within five hours was recovered as d-threitol. The proportion of d-threitol was greater when the collection was extended to 24 h. The d-threitol excretion was markedly diminished in cirrhotic patients, suggesting that a substantial proportion of the d-xylose-d-threitol conversion occurs in the liver. No decrease was detected in patients with fatty liver disease. No significant change in d-xylose excretion was observed in liver cirrhosis or in fatty liver disease.d-Threitol can be regarded as the main end product of d-xylose metabolism in man. The role of the glucuronate pathway in the d-xylose-d-threitol conversion is discussed.