Blood Sampling and Laboratory Analysis
BLOOD
The participants were not allowed to drink or eat for 6 h prior to blood collection. Preoperatively antidiabetic medications were terminated for 48 h and GLP-1 analogues for one week. Blood sampling was carried out during an 75gr OGTT (0, 30, 60, 120min) preoperatively, at 6 and 12 months postoperatively.Insulin was measured with enzyme-linked immunosorbent assay (ELISA) (Elecsys 2019, Roche) after serum collection. For the measurement of ghrelin, GLP-1 and PYY, blood collection was conducted with pre-cooled ethylenediaminetetraacetic acid (EDTA) vials, which contained 1,8 TIU (trypsin inhibitor units) of proteinase inhibitor, aprotinin (Trasylol). All the samples were centrifuged at 4°C for 20min, at 1600 RCF (Relative Centrifuge Force) and stored at −70°C until final analysis. For the above hormones analysis, commercial ELISA kits (Invitrogen, ThermoFisher Scientific) were utilized. All samples were collected, stored, and assayed at the same time in order to minimize the variation between groups.