Development and validation of a UPLC-MS/MS method to quantify fructose in serum and urine.

The study of the involvement of fructose in the pathogenesis of cardiometabolic disease requires accurate and precise measurements of serum and urinary fructose. The aim of the present study was to develop and validate such a method by Ultra Performance Liquid Chromatography-tandem Mass Spectrometry (UPLC-MS/MS). Fructose was quantified using hydrophilic interaction UPLC-MS/MS with a labelled internal standard. Serum fructose levels were determined in healthy individuals (n = 3) after a 15-gram oral fructose load. Twenty-four hours urinary fructose levels were determined in individuals consuming low (median: 1.4 g/day, interquartile range [IQR]: 0.9-2.0; n = 10), normal (31 g/day, 23-49; n = 15) and high (70 g/day, 55-84; n = 16) amounts of fructose. The calibration curves showed perfect linearity in water, artificial, serum, and urine matrices (r2 > 0.99). Intra- and inter-day assay variation of serum and urinary fructose ranged from 0.3 to 5.1% with an accuracy of ~98%. Fasting serum fructose levels (5.7 ± 0.6 µmol/L) increased 60 min after a 15-gram oral fructose load (to 150.3 ± 41.7 µmol/L) and returned to normal after 180 min (8.4 ± 0.6 µmol/L). Twenty-four hours urinary fructose levels were significantly lower in low fructose consumers when compared to normal and high fructose consumers (median: 36.1 µmol/24 h, IQR: 26.4-64.2; 142.3 µmol/24 h, 98.8-203.0; and 238.9 µmol/24 h, 127.1-366.1; p = 0.004 and p < 0.001, respectively). Fructose concentrations can be measured accurately and precisely with this newly-developed UPLC-MS/MS method. Its robustness makes it suitable for assessing the value of fructose in clinical studies.