Effect of a single bout of exercise on clock gene expression in human leukocyte.

Mammals have circadian clocks, which consist of the central clock in the suprachiasmatic nucleus and the peripheral clocks in the peripheral tissues. The effect of exercise on phase of peripheral clocks have been reported in rodents, but not in humans. Continuous sampling is necessary to assess the phase of the circadian rhythm of peripheral clock gene expressions. It has been assumed that the expression of the genes in leukocyte may be "an accessible window to the multiorgan transcriptome". The present study aimed to examine whether exercise affects the level and phase of clock gene expression in human leukocytes. Eleven young men participated in 3 trials, in which they performed a single bout of exercise at 60% O2max for 1 h beginning either at 7:00 (morning exercise), 16:00 (afternoon exercise) or no exercise (control). Blood samples were collected at 6:00, 9:00, 12:00, 15:00, 18:00, 21:00, 23:00, and at 6:00 the next morning, to assess diurnal changes of clock gene expression in leukocytes. Bmal1 expression level increased after morning and afternoon exercise, and Cry1 expression level increased after morning exercise. Compared with control trial, acrophase of Bmal1 expression tended to be earlier in morning exercise trial, and later in afternoon exercise trial. Acrophase of Cry1 expression was earlier in morning exercise trial, but not affected by afternoon exercise. Clock, Per1-3, and Cry2 expression levels and those acrophases were not affected by exercise. The present results suggest a potential role of a single bout of exercise to modify peripheral clocks in humans.