Luminex xmap instrument

Triglycerides, total cholesterol, LDL- and HDL-cholesterol were measured in plasma by enzymatic/colorimetric methods (SpinReact Kits, Girona, Spain) as described by Bucolo et al. The intensity of the color formed was proportional to the compound concentration [41 (link)].
Glycemic status was analyzed measuring fasting blood glucose and plasma insulin levels. Blood glucose concentration was measured by the enzyme electrode method, using an Ascensia ELITE XL blood glucose meter (Bayer Consumer Care, Basel, Switzerland); plasma insulin levels were measured using Milliplex xMAP multiplex technology on a Luminex xMAP instrument (Millipore, Austin, TX, USA).
Serum ALT and AST levels were measured on fasting morning plasma samples using the kinetic UV method (Liquid-Stat Reagent Kit Beckman Coulter, Nyon, Switzerland)

Fasting blood glucose and plasma insulin levels were measured after weeks 9, 14 and 23 in fasted animals. Blood glucose concentration was measured by the enzyme electrode method, using an Ascensia ELITE XL blood glucose meter (Bayer Consumer Care; Basel, Switzerland). Plasma insulin levels were measured using the rat/mouse insulin ELISA kit from Millipore Corporation (Billerica, MA, USA). The HOMA (Homeostatic Assessment Model) index was calculated as fasting insulin (µU/mL) × fasting glucose (mmol/L)/22.5^{23 (link)}. Insulin units (IU) were calculated using the conversion 1 IU = 0.0347 mg insulin.
The oral glucose tolerance test (OGTT) was performed at week 20 on fasted animals. A solution of glucose (1 g/kg body weight) was administered by oral gavage, and blood glucose concentration was measured 15, 30, 45, 60, 90 and 120 min after glucose intake by the enzyme electrode method.
Plasma leptin levels were measured using MILLIPLEX xMAP multiplex technology on a Luminex xMAP instrument (Millipore, Austin, TX, USA) at week 23. MILLIPLEX Analyst 5.1 (VigeneTech; Carlisle, PA, USA) software was used for data analysis.