Echomri 3 in 1 model instrument

Lean (protein) and fat (lipid) mass was determined on mice and tissue samples using an EchoMRI 3-in-1 model instrument (Echo Medical Systems, Houston, TX). Whole-body fat was also determined by dual-energy X-ray absorptiometry (PIXImus; GE Lunar, Fitchburg, WI) as described by Craft et al. (11 (link)). The activity of individual mice was quantified over a 24-h period using an infrared motion sensor (InfraMot apparatus; TSE Systems, Midland, MI) as previously described (20 (link)). The first 4 h of data (acclimation period) were not included in the analysis. For glucose tolerance tests (GTTs), mice were fasted overnight prior to a 1–2 g/kg dextrose injection. For insulin sensitivity tests (ITTs), mice were fasted 6 h prior to 0.75 units/kg Humulin-R insulin injection (Lilly, Indianapolis, IN). Contour meters (Bayer, Whippany, NJ) measured tail blood glucose concentration. Serum insulin concentration following 1 g/kg dextrose injection was determined using an Erenna digital single molecule counting platform (Singulex, St. Louis, MO). Triglyceride level and cholesterol concentration were determined as previously described (21 (link),22 (link)). Serum leptin was assayed by ELISA using commercial reagents (CrystalChem, Downers Grove, IL).