The circadian clock is an endogenous oscillator that harmonizes various physiological processes, including urinary function. We showed that each of the three bladder tissues and lumbar spine had a circadian clock. In addition, mice with 24-hour cycle genes show changes in water intake and excretion rhythms, suggesting a functional clock-dependent nature of micturition function. However, the effect of chronic circadian disturbance on urinary function and the exact mechanism is not yet clear. Therefore, in the present study, we investigated the effect of chronic meal time shifts on the daily cycle patterns of food intake, water consumption, and urine excretion in young adult male mice.

We induced chronic shifts in mealtime for 6 weeks and the activity of the Per2 promotor in the ex vivo state of a young adult bladder of Per2:: Luc knock-in mice were analyzed. To evaluate the metabolic changes glucose level, insulin resistance and reactive oxygen species (ROS) levels were analyzed. Administration with melatonin or C3G was performed to evaluate the influence of antioxidative agents on ROS levels.

Changes in mealtime increased the amplitude of Per2 oscillations. Also, mealtime shifts delayed the acrophore by delaying several hours. Mealtime shift-induced an imbalance between antioxidant capacity and ROS levels. Daily supplementation with melatonin or C3G in ZT23 blocked insulin resistance. However, supplementation of melatonin or C3G had no significant effect on the circadian pattern of water intake and urine excretion or the pattern of Per2 oscillation in the ex vivo cultured bladder.

In order to confirm whether this phenomenon is related to the clock gene, it was confirmed that the mealtime has a greater effect on the clock of the bladder than the clock gene. Subsequently, we confirmed that mealtime shift-induced an imbalance between antioxidant capacity and reactive oxygen species (ROS) levels in the body, resulting in increased oxidative damage during resting periods in mice. We found that daily supplementation of antioxidants such as melatonin or C3G in ZT23 can block insulin resistance due to chronic meal shifts and these findings meant that supplementation of antioxidants could decrease metabolic disturbance due to chronic meal shifts. However, the supplementation of antioxidants had no significant effect on the circadian pattern of water intake and urine excretion or the pattern of Per2 oscillation in the ex vivo cultured bladder. However, the longer the shift of mealtime, the more the change in urine volume and the rhythm that occurs every day was found to be weakened.

Our findings suggest that chronic mealtime shifts cause metabolic disorders and urinary changes through separable mechanisms.

Int Neurourol J 2019;23(Suppl 1):S40-49