Energy Expenditure

CLAMS Apparatus for Measurement of Metabolic Rate and Resting Exchange Ratio in Mice or Rats


Body weight is a balance between energy input (food intake) and energy output (resting metabolic rate, meal-induced thermogenesis and activity). Compounds which increase energy expenditure may produce weight-loss and the effects of novel antiobesity drugs on both sides of the energy balance equation should always be examined.

We have recently validated the Comprehensive Laboratory Animal Monitoring System (CLAMS) for evaluation of the effects of drugs on metabolic rate and respiratory exchange ratio in mice and rats. 

This open-circuit indirect calorimetry system has 8 chambers and offers the automated measurement of heat output, O2  and CO2 levels, food intake and activity (measured as the number of horizontal beam breaks). Readings are provided from each cage every 9 min for up to 24 h. Output can be customised to calculate data in a variety of formats. For example, the  levels of O2 and CO2 measured at the cage outlet can be used to generate the respiratory exchange rato (RER, ratio of CO2 to O2). This parameter gives an estimate of the respiratory quotient (RQ).

We have used CLAMS to investigate the effects of the thyroid hormone, triiodothyronine (T3), on energy expenditure in dietary-induced obese (DIO) mice. T3 increased heat output in these animals as expected. The relatively small increase in measured activity indicates that the large increase in heat production was largely due to increased basal metabolic rate. The reduction in respiratory exchange ratio produced by T3 indicates that the increase in metabolic rate was due to increased metabolism of fat.


Measurement of Heat Output in DIO Mice using CLAMS



Measurement of Respiratory Exchange Ratio in DIO Mice using CLAMS



Measurement of Activity in DIO Mice using CLAMS


At the end of studies, inguinal and epididymal white adipose tissue (WAT) and interscapular brown adipose tissue (BAT) can be collected and weighed and tissue taken for determination of UCP1 immunohistochemistry if required.


Effect of T3 on Fat Pad Weights in DIO Mice


In this study, the observed reduction in white adipose tissue was consistent with the decrease in the respiratory exchange ratio produced by T3 in the DIO mice.

Please contact us for further information about measurement of the effects of drugs on energy expenditure in rats and mice.