Figure 4.

Oxygen consumption and RQ in WT and hl^−/− mice during dark (DC1, DC2) and light (LC) cycles. A and C, Chow diet. B and D, HF diet; two-way ANOVA for average VO₂ yields *, P < 0.005 for the contribution of genotype during LC, and *, P < 0.04 on DC2; **, P < 0.005 for the contribution of diet during LC and DC2. Two-way ANOVA for RQ reveals a *, **, P < 0.03 for the contribution of genotype during LC and P < 0.0001 for the contribution of diet during LC and DC2. E–H, Reduced diurnal variation in oxygen consumption (E), RQ (F), heat production (G), and locomotor activity (H) in WT and hl^−/− female mice on chow and HF diets. Diurnal variation is expressed as the ratio of light cycle and the mean of the two dark cycles [DC = (DC1 + DC2)/2] measurements of VO₂, RQ, heat production, and locomotor activity. A ratio of one indicates complete lack of diurnal variation (chow: WT, n = 6, and hl^−/−, n = 4, HF: WT, n = 7; hl^−/−, n = 5). On the chow diet, two-way ANOVA demonstrates a significant contribution of genotype to the diurnal variation in oxygen consumption and RQ (P = 0.002) as well as a significant contribution of genotype to the diurnal variation in heat expenditure and locomotor activity (P < 0.03).