Comparison of The Effects of High Fat Diet on Energy Flux in Mice Using Two Multiplexed Metabolic Phenotyping Systems

OBJECTIVE: Multiplexed metabolic phenotyping systems are available from multiple commercial vendors, and each system includes unique design features. Although expert opinion supports strengths and weaknesses of each design, empirical data from carefully controlled studies to test the biological impact of design differences is lacking. METHODS: Wildtype C57BL/6J mice of both sexes underwent phenotyping in OxyMax (Columbus Instruments International) and Promethion (Sable Systems International) systems located within the same room of a newly constructed animal research facility, in a crossover design study. Phenotypes were examined under chow (2920x)-fed conditions, and again after four weeks of 60% high fat diet (D12492) feeding. RESULTS: Food intake, physical activity, and respiratory gas exchange data significantly diverged between systems, depending upon sex of animals and diet supplied. Estimates of energy expenditure based on gas exchange in both systems accounted for a fraction of consumed calories that was greater in males than females. CONCLUSIONS: Design differences quantitatively impact the assessment of metabolic endpoints and therefore the qualitative interpretation of various interventions. Importantly, current multiplexed systems remain blind to multiple additional endpoints including digestive efficiency and selected forms of energy flux (nitrogenous, anaerobic, etc.) which account for a physiologically / pathophysiologically-significant fraction of total energy flux.