Author(s): TSUDA, E., MICHISHITA, R., SAKAMOTO, M., KAWAKAMI, S., ABE, T., NAKASHIMA, S., HIGAKI, Y., UEHARA, Y., Institution: FACULTY OF SPORTS AND HEALTH SCIENCES, FUKUOKA UNIVERSITY, Country: JAPAN, Abstract-ID: 2137

INTRODUCTION:
It is well known that circadian rhythm disorders progress to development of various disease such as diabetes, cancer, depression, and sleep disorders. The circadian rhythm is thought to have been regulate to the light stimulation, diet, exercise, thermoregulation, and hormonal balance. From the perspective of disease prevention, it is extremely important to consider the effects of lifestyle modification on the progress of the circadian rhythm. It has been reported that circadian rhythm is controlled the clock gene, and a few animal studies shown a single bout of exercise is effective in advancing clock gene expression. However, the effect of difference in timing of exercise on circadian clock gene expression had not been clarified. This study was designed to examine the effects of difference in timing of exercise on human circadian clock gene expression.
METHODS:
Five healthy young males (age, 23.8 ± 1.9 years; BMI, 23.1 ± 3.1kg/m2) participated in a two-night, three-day residential study. This study set the following four conditions of timing of exercise; 1) morning exercise (exercise starts at 8:00 am), 2) daytime exercise (exercise starts at 12:00 pm), 3) night exercise (exercise starts at 5:00 pm), and 4) control (no exercise). All of participants were performed to exercise using a bicycle ergometer for 60 min at the lactate threshold (LT) intensity. The hair of head was collected a total of 6 times every 4 hours starting at 7:00 am on the test day, and the expression levels of Clock, Bmal1, and Per2 mRNAs were analyzed from the hair follicle cells using real-time PCR method. Salivary sample was collected from 20:00 to 23:00 on every 30 min the test day, and from 6:00 to 8:00 on every 30 min the next morning to measure the salivary melatonin, serotonin and cortisol secretion. This study was examined the difference in relative expression levels of clock gene, and changes in salivary melatonin, serotonin and cortisol secretion levels among the above four conditions.
RESULTS:
The mean LT intensity and maximal oxygen uptake in all of participants were 95.8 ± 13.9 watts, and 47.5 ± 6.5 ml/min/kg, respectively. The relative expression level of Bmal1 mRNA increased after exercise in the morning and daytime exercise conditions. However, there was no difference in the relative expression levels of Clock and Per2 mRNA among the four conditions. Although there was no difference in the change in salivary melatonin secretion level among four conditions, DLMO (Dim Light Melatonin Onset) was the fastest in the morning exercise condition compared to the other three conditions. However, there was no difference in the changes in salivary serotonin and cortisol secretion levels among the above four conditions.
CONCLUSION:
These results suggested that morning and daytime exercise may increase the expression level of circadian clock gene, particularly Bmal1 mRNA, and morning exercise may promote melatonin secretion level.