*4.8. Glycemia, Insulin, C-Peptide, and Glycated Hemoglobin A1C Measurements*

Glucose, insulin, and C-peptide concentrations were measured in fasting plasma and at different time points of the OGTT. Blood glucose was measured using The Dimension Vista® GLU method (REF K1039) (Siemens Healthcare Diagnostics Inc., Tarrytown, NY, USA), an adaptation of the hexokinase-glucose-6-phosphate dehydrogenase method [60]. Insulin and C-peptide, a marker of insulin secretion, were determined using ADVIA Centaur XPT

Immunoassay System test (Siemens Healthcare Diagnostics Inc., Tarrytown, NY, USA), a sandwich immunoassay using direct chemiluminescent technology, and specific insulin and C-peptide antibodies. HbA1c was determined using a 2.0 assay on a VARIANT II TURBO Hemoglobin Testing System (Bio-Rad Laboratories Inc., Hercules, CA, USA) using the principle of ion-exchange high-performance liquid chromatography. These analyses were performed at the Research Centre of Laval University Hospital (CHU of Québec) (QC, Canada).

The Homeostasis Model Assessment of Insulin Resistance (HOMA-IR) was used to estimate insulin sensitivity/resistance. HOMA-IR index was calculated according to the following formula: fasting insulin concentration (μL/mL) × fasting glucose concentration (mmol/L)/22.5 [61].
