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Endocrine/Metabolic Function/Body Composition

Body Composition


Rationale: Measures of whole body fat mass, lean tissue mass and free water.
Instrument: Quantitative magnetic resonance imaging (qMRI) instrument by EchoMRI.
Measures: Exact measures of total body fat, lean mass, and free water are obtained by ascertaining how protons contained in the lean and fat mass perturb a magnetic field. Measures are performed without the need for sedation, in less than one minute.
Data Inference: Data are QMR fat mass (grams), QMR lean mass, QMR free water and QMR body weight calculated by adding fat mass, lean mass, and free water together.
Controls: All animals are tested individually.

Clamp Studies for Sensitivity and β-cell Function


Hyperinsulinemic euglycemic clamps are performed in conscious unrestrained rodents to assess whole body glucose turnover and insulin sensitivity. Hyperglycemic clamps are performed to evaluate beta cell function.

Circulating Lipids, Glucose, and Insulin Concentration

Exercise Tolerance and Performance


Exercise tolerance testing is performed following a ramped protocol using a treadmill for rodents (Columbus Instruments). Voluntary activity is measured using running wheels with magnetic indicators that count turns.

HbA1c Levels



Rationale: Measures of metabolism (oxygen consumption, carbon dioxide production, respiratory quotient) and spontaneous activity in a 48 h period.
Instrument: MARS (Multiple Animal Respirometry System) from Sable Systems International.
Measures: Animals are placed in cages for 48 hours. The difference between the concentrations of oxygen and carbon dioxide in a sealed cage at baseline is compared to the amounts present after the mouse has breathed the air during the testing period.
Data Inference: Oxygen consumption, carbon dioxide production, respiratory quotient and spontaneous activity are analyzed through ExpeData software.
Controls: Care is taken to acclimatize animals and ensure that room is secluded and not accessed during testing.

Thyroid Hormone, Cortisol, and Sex Steroid Levels

Voluntary Activity/Mobility


Rationale: Measures of circadian activity in rodents.
Instrument: SmartFrameTM High Density Cage Rack 8 unit system (Hamilton-Kinder, Inc.).
Measures: Interruptions of high-density infrared photo-beams mounted in large, high cages similar to home cages with food and water available ad libitum are recorded during a 24 hour period.
Data Inference: Measures of circadian activity including fine movements, time, entries and pokes in specific zones, distance traveled, rest time, active time and number of rears are obtained for a 24 h period.
Controls: Care is taken to acclimatize animals and ensure that room is secluded and not accessed during testing.