OGTT and euglycemic-hyperinsulinemic clamp test (EHC)

After 10–12 h of fasting overnight, all subjects were given 75g glucose orally and the OGTT test was performed at 8:00 AM (American Diabetes, 2012). During the OGTT, blood samples were collected for the measurements of blood glucose, insulin, and serum fetuin-B at 0, 30, 60, and 120 min. The EHC was performed in all subjects. The operation process was as previously reported (Xu et al., 2020). During the EHC, human insulin (1mU/kg/min) was continuously infused for 2 h. At the same time, the infusion rate of the 20% glucose was adjusted according to the blood glucose levels, tested every 15 min, to maintain blood glucose at the basic level (4.5−5.5 mmol/L). In the steady-state of the clamp, GIR was equal to glucose disposal rate (GDR), and M-value was related to GIR and body weight. Blood samples were collected at 0, 80, 100, and 120 min for the determination of fetuin-B and insulin. Blood samples were centrifuged, and serum was separated and stored at −80 °C for subsequent analysis.