PURPOSE: Mammals urinate less frequently during sleep period than during awake period, which is modulated by triad factors; decreased arousal level in the brain, decreased urine production rate from the kidneys, and increased functional bladder capacity during sleep.
The circadian clock ('the clock') is genetic transcription-translation feedback machinery. The clock exists in most organs and cells, termed 'peripheral clock', which is orchestrated by the central clock in the suprachiasmatic nucleus of the brain. In this review we discuss the linkage between the day-and-night change in micturition frequency and the genetic rhythm maintained by the clock system, focusing on brain, kidney and bladder.
MATERIAL AND METHODS: We performed inclusive review of the literature on diurnal change in micturition frequency, urine volume, functional bladder capacity and urodynamics in humans and rodents, and related it with recent basic biological findings about the circadian clock.
RESULTS: In humans, various behavioral studies demonstrated diurnal functional change in kidney and bladder, and conversely, patients with nocturnal enuresis and nocturia show impairment of these triad factors. Rats and mice, which are nocturnal animals, also show rhythm in micturition frequency, decreased during daytime, which is sleep phase for them. Mice having genetically defective circadian clock system show impaired physiological rhythms in the triad factors. Existence of the circadian clock has been proven in brain, kidney and also in the bladder, in which exist thousands of circadian oscillating genes. In the kidney, they include genes involved in regulation of water and major electrolytes and in the bladder, a gene associated with regulation of bladder capacity, connexin 43.
CONCLUSION: Recent progress in molecular biology about the circadian clock provides an opportunity for investigating genetic basis of micturition rhythm, or impairment of the rhythm in nocturnal enuresis and nocturia. If this approach is to be translated clinically, one strategy is to analyze and treat the triad of micturition factors as separate parts of one problem. The other way could be, if possible, to cope with these triad problems simultaneously by treating the circadian physiological rhythm itself. Discoveries reviewed here point toward further investigation of micturition rhythm by basic and translational chronobiology.
Written by:
Negoro H, Kanematsu A, Yoshimura K, Ogawa O. Are you the author?
Department of Urology, Graduate School of Medicine, Kyoto University, Sakyo, Kyoto 606-8507, Japan.
Reference: J Urol. 2013 Feb 18. pii: S0022-5347(13)00293-0.
doi: 10.1016/j.juro.2013.02.024
PubMed Abstract
PMID: 23429068
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