Figure 3. Peripheral clock phases mimic human eating habits.

Schematic feeding schedules (left) and average PER2::LUC peak phases for each organ under each feeding condition (right, mean ± SEM). The white and black bars on the horizontal axis indicate environmental 12-h light and dark conditions, respectively. The white circles indicate feeding times, and the circle size is relative to the food volume. The arrowheads indicate the feeding times that followed the longest non-feeding interval, for each condition. After 2 weeks of habituation to each feeding condition, peripheral clocks were monitored. (A) Peripheral clock phase of mice fed 3 meals equally spaced throughout the day and night; food was given at ZT 0, 6, and 12 (a) or at ZT 12, 18, and 24 (b); n = 6 mice per condition. *p < 0.05, vs. (a), by Student's t-test. (B) Peripheral clock phases of mice fed 3 meals per day, mimicking the eating schedule typically followed by humans: breakfast (ZT 12), lunch (ZT 17), and dinner (ZT 1, 3, or 4) (c–e). Meal sizes were as follows: breakfast, 0.9 g (27% of total food volume); lunch, 1.2 g (36%); and dinner, 1.2 g (36%); n = 4 for (c) and n = 6 for (d) and (e). *p < 0.05, vs. (c), by the Tukey-Kramer test for each organ. (C) Peripheral clock phases of mice fed either a late dinner (ZT 4) or a late dinner separated into 2 meals at ZT 0 and ZT 4. The data for (f) is the same as those for (e) of figure 3B. After monitoring mice for the conditions described for (f), the same mice were used for experimental condition (g) (n = 6 mice per condition). *p < 0.05, vs. (f), by paired Student's t-test. Sub Gla, submandibular gland; ZT, Zeitgeber time.