Applying indirect open circuit calorimetry to study energy expenditure in gnotobiotic mice harboring different human gut communities

Given the increasing use of gnotobiotic mouse models for deciphering the effects of human microbial communities on host biology, there is an increased need to develop new ways of characterizing these animals within the confines of their isolators. We describe a method for performing open circuit indirect calorimetry on gnotobiotic mice colonized with gut microbial consortia obtained from different human donors; in the illustrative case, culture collections were obtained from obese and lean co-twins. The approach allows microbial contributions to energy homeostasis to be characterized.