Measurement of serum fructose and uric acid levels
Prior to measuring serum fructose concentrations using a fructose fluorometric assay kit (K611-100; BioVision Inc., Milpitas, CA, USA), the serum samples were diluted 1:5 in the assay buffer. The assay was performed in accordance with the manufacturer’s instructions. Glucose interference was removed using a sample purification reagent. Free fructose was enzymatically processed, and the metabolites formed were reacted with the probe to generate fluorescence, which could be measured at Ex/Em 535/587 nm. The intra- and inter-assay coefficients of variation (CVs) were 7.8% and 10.2%, respectively.
Serum uric acid levels were determined using an enzymatic assay performed on an ARCHITECT ci16200 Automatic Biochemical Analyzer (Abbott Laboratories, IL, USA) using the Architect urid acid Reagent Kit (Abbott Laboratories), according to the manufacturer’s and supplier’s instructions. The reference range for serum uric acid levels at the study center was considered as 155-357 µmol/l, which established 357 µmol/l as a clinical diagnostic cutoff for hyperuricemia in healthy Chinese participants. The participants’ characteristics are provided in Table 2.