Figure 4. SirT1-null mice are hypermetabolic.

Whole animal indirect calorimetry (IC) was used to assess oxygen consumption normalized to body weight (VO₂/BWT) plotted (panel A) at 30 minute intervals during a 24 hour period or (panel B) as the percent relative cumulative frequency (PRCF) of VO₂/BWT. The respiratory exchange ratio (RER = VO₂/VCO₂) was calculated from VO₂ and VCO₂ data and plotted at 30 minute intervals during a 24 hour period (panel C) or as PRCF (panel D). In a fasting-refeeding experiment (panel E), food was either removed or added at the indicated times (arrows) and the interval RER plotted. Grey and black lines above the X-axis (panels A, C, and E) indicate light and dark periods, respectively. An RER of 1.0 is expected for glucose oxidation and an RER of 0.7 occurs during lipid oxidation. Means and standard errors are represented. An unpaired T-test using medians was performed to assess statistical significance (B).