Increased fructose concentrations in blood and urine in patients with diabetes

Abstract

OBJECTIVE - To investigate fructose metabolic changes in patients with diabetes. RESEARCH DESIGN AND METHODS - Serum and urinary fructose concentrations were determined in healthy subjects (n = 23) and in nondiabetic (n = 23) and diabetic patients (n = 26). Fructose was measured using our newly developed method, and 13C6-fructose was used as the internal standard. After adding sample to a fixed amount of internal standard, ion-exchange resins and high-performance liquid chromatography pretreatments were performed. Then, the amount of fructose in the sample was measured by gas chromatography-mass spectrometry. RESULTS - Serum fructose concentrations in patients with diabetes (12.0 ± 3.8 μmol/l) were significantly higher than those in healthy subjects (8.1 ± 1.0 μmol/l, P < 0.001) and nondiabetic patients (7.7 ± 1.6 μmol/l, P < 0.001), and daily urinary fructose excretion was significantly greater in patients with diabetes (127.8 ± 106.7 μmol/day) than in nondiabetic patients (37.7 ± 23.0 μmol/day, P < 0.001). In patients with diabetes (n = 20), serum fructose concentrations (8.6 ± 1.8 μmol/l, P < 0.001) and daily urinary fructose excretion (63.4 ± 63.8 μmol/day, P < 0.01) significantly decreased by week 2 after admission. CONCLUSIONS - The present results differed from those of previous studies in that we found that the serum and urinary fructose concentrations decreased rapidly, concomitant with an improvement in glycemia. Therefore, hyperglycemia was associated with increased serum and urinary fructose concentrations in patients with diabetes.