Def+/+ mice show different respiratory profile compared to their WT littermates. Alpha-defensin transgenic mice demonstrate lower respiratory quotient (A); overexpression of alpha-defensin does not change total energy expenditure (TEE; B), but significantly increases fat oxidation (C) and lowers carbohydrate oxidation (D). Method: Mice were monitored using the Promethion High-Definition Behavioral Phenotyping System (Sable Instruments, Inc., Las Vegas, NV, USA) over a 24 h period. Effective mass was calculated by power of 0.75. Data are mean ± SD from 4 mice per group. *** p < 0.001 vs. C57 WT, **** p < 0.0001 vs. C57 WT.