METABOLIC PHENOTYPING

At 18 weeks of the feeding period, mice were placed in fully automated metabolic chambers, and indirect calorimetry and voluntary activity were measured using the Oxymax System (Columbus Instruments, OH) as described.⁹ Due to differences in body mass between groups, all indirect calorimetry data were normalized to lean body mass. For blood fasting glucose and insulin analysis, mice were fasted for 6 hours. Fasting glucose was evaluated using a blood glucose monitor (Assure 4; Arkray, MN). Fasting insulin was measured using the Ultra‐Sensitive Mouse Insulin enzyme‐linked immunosorbent assay kit (Crystal Chem, IL) as per the manufacturer's instructions. The homeostatis model assessment of insulin resistance index was calculated as described.²⁴