Laboratory measurements were performed at Zhongnan Hospital for the current study. Kidney function parameters (creatinine, urea nitrogen, uric acid and eGFR[19 (link)]) and serum glucose were examined by the AU5800 Chemistry Analyzer (Beckman). The HA-8160 Glycohemoglobin Analyzer (ADAMS) was used to measure blood glycated hemoglobin (HbA1c). Serum insulin was assayed by the i4000SR Immunology Analyzer (Abbott Laboratories).