Edta 2k

All participants performed 75 g OGTT after 12 hours over night fast. Before performing OGTT, height and body weight was measured. Body mass index (BMI) was calculated from height (m) and body weight. Blood samples were collected before, 30, 60, 90 and 120 min after glucose intake for measuring plasma glucose (PG), insulin, C-peptide immunoreactivity (CPR), glucagon, and active GLP-1 (6-36-GLP-1 and 7-36-GLP-1 amide). Blood was drawn from the catheter placed in participants' forearm or cubital vein. Blood samples for measuring glucagon and GLP-1 concentration were collected in vacutainer tubes, P800, containing EDTA-2K, protease, esterase, and dipeptidyl peptidase-4 inhibitors (Becton, Dickinson and Company, New Jersey, USA). After blood collection, the tubes were immediately immersed in ice water and centrifuged at 20°C for 20 min. Plasma was collected and stored in deep-freezer at -80°C until analysis. We used the criteria of glucose tolerance in OGTT according to World Health Organization criteria; fasting PG (FPG) <110 mg/dL (6.1 mmol/L) and PG at 120 minutes (2 h PG) <140 mg/dL (7.8 mmol/L) defined as NGT, 110 mg/dL ≤ FPG < 126 mg/dL (7.0 mmol/L) and/or 140 mg/dL (7.8 mmol/L) ≤ 2 h PG < 200 mg/dL (11.1 mmol/L) as preDM, fasting PG ≥126 mg/dL (7.0 mmol/L) and/or 2 h PG ≥200 mg/dL (11.1 mmol/L) as DM.