Phenomaster metabolism research platform

Body composition of WT and Nmp4^−/− mice was evaluated by quantitative magnetic resonance imaging using EchoMRI Body Composition Analyzer (EchoMRI, LLC, Houston, Texas). Metabolic cage studies were performed using a TSE systems PhenoMaster Metabolism Research Platform (Chesterfield, MO) equipped with calorimetry, feeding/drinking, and activity monitoring^{38 (link)}. Intraperitoneal glucose tolerance tests (IP-GTT) were performed subsequent to a 6hr fast and intraperitoneal injection of glucose at 1 g/kg; blood glucose levels were measured using an AlphaTRAK glucometer (Abbott Laboratories, Abbott Park, IL) at 0, 10, 20, 30, 60, 90, 120, and 180 min. To evaluate insulin sensitivity, insulin tolerance tests (ITT) were conducted by administering 0.75 U/kg insulin via IP injection after 2 hours fast and blood glucose levels were measured at times 0, 15, 30, 45, 60 minutes post insulin challenge. For β cell mass pancreata were processed, and insulin immunohistochemistry was performed as previously described^{39 (link)}. Tissue sections, 3 per mouse (technical replicates for each biological replicate) and at least 50μm apart, were analyzed using Zen Blue software (Zeiss, Oberkochen, Germany). The insulin positive area in pixels were divided by the total pancreas area in pixels, and then multiplied by pancreas weight to generate β cell mass in mg.

Body composition was analyzed by quantitative magnetic resonance imaging using EchoMRI Body Composition Analyzer (EchoMRI, LLC, Houston, Texas). Indirect calorimetry measures were performed using a TSE systems PhenoMaster Metabolism Research Platform (Chesterfield, MO) equipped with calorimetry, feeding/drinking, and activity monitoring as described.^{23 (link)} Glucose tolerance tests (GTTs) were performed following a 16 hour fast and intraperitoneal injection of 2 g/kg lean mass of D-glucose solution. Blood was sampled from the tail vein at 0, 10, 20, 30, 60, 90, and 120 min, and glucose was measured using a glucometer (AlphaTRAK, Abbott Park, IL, USA). Insulin tolerance tests (ITTs) were performed on 2 hour fasted mice following an intraperitoneal injection of 0.75 U/kg lean mass Humulin-R insulin (Lilly, Indianapolis, IN, USA). Blood glucose was measured from tail vein blood at 0, 15, 30, 45, and 60 min.