D01060502

At 21 days old, male heterozygous PER2::LUC mice were weaned and group housed (2–4 mice per cage). Chow and water were provided ad libitum. At 7 weeks old, mice were singly housed in cages (33 × 17 × 14 cm) and provided with chow ad libitum. The cages contained either locked wheels (wheels could not rotate) or freely rotating wheels and were housed in light-tight boxes in 12L:12D (light intensity 200–300 lux; temperature inside light-tight boxes: 25.5 ± 1.5°C). At 8 weeks old, the chow was replaced with either high-fat diet (45% kcal from fat; Research Diets D01060502) or with fresh chow. Food was changed within 3 h of lights off. One mouse was excluded from the analysis because it did not have any eating events for 12 h after high-fat diet was placed in the food hopper. To evaluate the effect of environmental enrichment without a running wheel, the experiment was performed as described above except that mice were single-housed in empty cages or in cages with 1 paper-based refuge hut and 2 sheets of nesting paper. At 9 weeks old, PER2::LUC expression was measured in ex vivo tissues. Body weight and food were measured at 7, 8, and 9 weeks old within 3 h before lights off. Total kcal consumed was calculated based on the grams of food consumed (chow: 3.02 kcal/g metabolizable energy; 45% HFD: 4.73 kcal/g).

Heterozygous PER2:LUC C57BL/6J and wild-type female mice were single housed in cages (33 cm × 17 cm × 14 cm) with locked running wheels (wheels could not rotate) in light-tight boxes in 12L:12D (light intensity 200–300 lux; temperature inside light-tight boxes: 25.5 ± 1.5°C) at 7 weeks old and maintained on chow ad libitum. Beginning at 8 weeks old, mice were fed either chow or 45% high-fat diet (Research Diets D01060502) for 8 weeks. Body weight was measured weekly (always within 3 h before lights off).

At 7 weeks old, male heterozygous PER2::LUC mice were singly housed in cages (33 x 17 x 14 cm) with locked running wheels (running wheels were present but could not rotate) and fed chow ad libitum. The cages were housed in light-tight, ventilated boxes in 12h light:12h dark (light intensity ~200–300 lux) at 25.5±1.5°C. At 8 weeks old, mice were either fed chow for 5 weeks (Fig 1A; n = 7), fed high-fat diet (45% kcal from fat; Research Diets D01060502; 4.73 kcal/g) for 5 weeks (Fig 1B; n = 7), or fed high-fat diet for 4 weeks and then chow for 1 week (Fig 1C; n = 7). At 13 weeks old, PER2::LUC expression was measured in ex vivo liver cultures.