Free fatty acids (NEFA C, Wako Pure Chemical Industries; Richmond, VA, USA) were measured using colorimetric methods in commercially available kits.
Serum levels of Leptin (ALPCO Diagnostics, 26 Keewaydin Drive Unit G. Salem, NH) and total non-esterified fatty acids (NEFA) (Wako Diagnostics, Wako Chemicals USA, Inc. VA, USA) were measured using standard ELISA method according to procedures provided from the manufacturer.
Serum OPN levels (eBioscience Inc., San Diego, CA, USA) were measured using a commercial available enzyme-linked immunosorbent assay (ELISA).
Serum intact parathyroid hormone levels (iPTH) (Diagnostic Systems Laboratories, Webster, Texas, USA) were measured using a commercially available ELISA [ 18].
Plasma concentrations of exenatide (Tandem Labs, San Diego, CA, USA) were measured using a validated enzyme-linked immunosorbent assay [ 20].
Plasma leptin (BioVendor, Candler, North Carolina, USA), adiponectin (R&D Systems, Minneapolis, Minnesota, USA) and apoA-1 levels (Mabtech, Cincinnati, Ohio, USA) were measured using ELISA.
Cyclic voltammetry (CV; BioLogic, SP-50, USA) was measured using a half-cell system with three electrodes for electrochemical analysis.
The activity of luciferase (Promega) and β-galactosidase (GalactoStar; Applied Biosystems, Foster City, CA, USA) was measured using a luminometer.
GIP (Millipore Corporation, USA), active ghrelin (Millipore Corporation, USA) and active GLP-1 (Millipore Corporation, USA) levels were measured using commercial ELISA kits.
After treatment for 24 hours the luciferase (Promega, Southampton, UK) and β-galactosidase (Galacto Star, Applied Biosystems, Bedford, MA, USA) activities were measured using a luminometer (TD20/20).
Plasma triglyceride (PAP 150, BioMérieux), non-esterified fatty acids (FAs) (Wako, Neuss, Germany), insulin (IBL, Hamburg, Germany) and adiponectin (Millipore Corporation, Billerica, MA, USA) levels were measured using commercial kits.
