The top panel shows the experimental protocol. Mice in the LL group were exposed to light continuously from weeks 0 to 24 (experimental phase), then returned to a standard 12 hr light/12 hr dark (LD) cycle from weeks 24 to 48 (recovery phase). Mice in the control group were maintained under the standard LD cycle for the entire 48 weeks. At the indicated time points, mice were sacrificed for muscle and bone experiments or for LPS experiments. Note that separate cohorts of mice were used at every time point. Mice used for the in vivo recordings are not included in the figure.

(A) Examples of actograms recorded in LL and control (LD) mice at the indicated time points. Each horizontal row represents behavioral activity measured using a passive infrared motion detector on a double-plotted 24-hr day. Gray background represents the dark period, and white background represents the light period.

(B–D) Rhythm strength, rhythm period, and total activity of mice in the LL and control groups at the indicated times (mean ± SD; n = 8–22 mice per group).

(E and F) 5-day moving averages of rhythm strength and period in behavior in the final days of LL (or control) and in the first days after returning to an LD cycle (mean ± SEM; n = 22 per group).

(G and H) Body weight and unfasted glucose levels in the LL and control groups at the indicated times (mean ± SD; n = 8–10 per group).