Low density lipoprotein receptor (LDLR) plays an important role in the cholesterol homeostasis. We examined the possible circadian regulation of LDLR and mechanism(s) underlying it. In mice, blood glucose and plasma triglyceride, total and high density lipoprotein cholesterol varied distinctively throughout a day. In addition, LDLR mRNA oscillated in the liver in a functional clock-dependent manner. Accordingly, analysis of human LDLR promoter sequence revealed three putative E-boxes, raising the possible regulation of LDLR expression by E-box-binding transcription factors. To test this possibility, human LDLR promoter reporter constructs were transfected into HepG2 cells and the effects of CLOCK/BMAL1, Hes1, and Hes6 expression were analyzed. It was found that positive circadian transcription factor complex CLOCK/BMAL1 upregulated human LDLR promoter activity in a serum-independent manner, while Hes family members Hes1 and Hes6 downregulated it only under serum-depleted conditions. Both effects were mapped to proximal promoter region of human LDLR, where mutation or deletion of well-known sterol regulatory element (SRE) abolished only the repressive effect of Hes1. Interestingly, hes6 and hes1 mRNA oscillated in an anti-phasic manner in the wild-type but not in the per1-/-per2-/- mouse. Comparative analysis of mouse, rat and human hes6 genes revealed that three E-boxes are conserved among three species. Transfection and site-directed mutagenesis studies with hes6 reporter constructs confirmed that the third E-box in the exon IV is functionally induced by CLOCK/BMAL1. Taken together, these results suggest that LDLR expression is under circadian control involving CLOCK/BMAL1 and Hes family members Hes1 and Hes6.
ARNTL Transcription Factors/physiology ; Animals ; Base Sequence ; Basic Helix-Loop-Helix Transcription Factors/*genetics/metabolism/physiology ; CLOCK Proteins/physiology ; Cholesterol/blood ; *Circadian Rhythm ; E-Box Elements ; Exons ; *Gene Expression Regulation ; Hep G2 Cells ; Homeodomain Proteins/*genetics/metabolism/physiology ; Homeostasis ; Humans ; Liver/metabolism ; Male ; Mice ; Mice, Inbred C57BL ; *Promoter Regions, Genetic ; Receptors, LDL/*genetics/metabolism ; Repressor Proteins/*genetics/metabolism/physiology ; Transcription, Genetic

While circadian rhythms in fluid intake, urine production, and urine storage have been substantiated in diurnal human and nocturnal rodents, the mechanism(s) underlying it is largely unknown. With the elucidations of molecular clockwork and its functional significance in mammals, new opportunities arise to investigate possible circadian control of voiding function and dysfunction, which undoubtedly needs immediate attentions of researchers in the field.
Attention ; Circadian Rhythm ; Humans ; Mammals ; Rodentia

Circadian clocks are the endogenous oscillators that harmonize a variety of physiological processes within the body. Although many urinary functions exhibit clear daily or circadian variation in diurnal humans and nocturnal rodents, the precise mechanisms of these variations are as yet unclear. In this review, we briefly introduce circadian clocks and their organization in mammals. We then summarize known daily or circadian variations in urinary function. Importantly, recent findings by others as well as results obtained by us suggest an active role of circadian clock genes in various urinary functions. Finally, we discuss possible research avenues for the circadian control of urinary function.
Biological Clocks ; Circadian Clocks ; Circadian Rhythm ; Humans ; Mammals ; Physiological Processes ; Rodentia ; Urinary Bladder ; Urination

Circadian clocks are the endogenous oscillators that harmonize a variety of physiological processes within the body. Although many urinary functions exhibit clear daily or circadian variation in diurnal humans and nocturnal rodents, the precise mechanisms of these variations are as yet unclear. In the present study, we demonstrate that Per2 promoter activity clearly oscillates in neonate and adult bladders cultured ex vivo from Per2::Luc knock-in mice. In subsequent experiments, we show that multiple local oscillators are operating in all the bladder tissues (detrusor, sphincter and urothelim) and the lumbar spinal cord (L4-5) but not in the pontine micturition center or the ventrolateral periaqueductal gray of the brain. Accordingly, the water intake and urine volume exhibited daily and circadian variations in young adult wild-type mice but not in Per1-/- Per2-/- mice, suggesting a functional clock-dependent nature of the micturition rhythm. Particularly in PDK mice, the water intake and urinary excretion displayed an arrhythmic pattern under constant darkness, and the amount of water consumed and excreted significantly increased compared with those of WT mice. These results suggest that local circadian clocks reside in three types of bladder tissue and the lumbar spinal cord and may have important roles in the circadian control of micturition function.
Animals ; *Circadian Clocks ; Drinking ; Mice ; Organ Specificity ; Periaqueductal Gray/metabolism/physiology ; Period Circadian Proteins/genetics/*metabolism ; Pons/metabolism/physiology ; Spinal Cord/*metabolism/physiology ; Urinary Bladder/innervation/metabolism/*physiology ; Urination

Peroxisome proliferator activated receptor (PPAR) gamma coactivator-1alpha (PGC-1alpha) may be implicated in cholesterol metabolism since PGC-1alpha co-activates estrogen receptor alpha (ERalpha) transactivity and estrogen/ERalpha induces the transcription of LDL receptor (LDLR). Here, we show that overexpression of PGC-1alpha in HepG2 cells represses the gene expression of LDLR and does not affect the ERalpha-induced LDLR expression. PGC-1alpha suppressed the LDLR promoter-luciferase (pLR1563-luc) activity regardless of cholesterol or functional sterol-regulatory element-1. Serial deletions of the LDLR promoter revealed that the inhibition by PGC-1alpha required the LDLR promoter regions between -650 bp and -974 bp. Phosphorylation of PGC-1alpha may not affect the suppression of LDLR expression because treatment of SB202190, a p38 MAP kinase inhibitor, did not reverse the LDLR down-regulation by PGC-1alpha. This may be the first report showing the repressive function of PGC-1alpha on gene expression. PGC-1alpha might be a novel modulator of LDLR gene expression in a sterol-independent manner, and implicated in atherogenesis.
Base Sequence ; Cell Line, Tumor ; Cholesterol/metabolism ; Estrogen Receptor alpha/metabolism ; Gene Expression Regulation ; Heat-Shock Proteins/*genetics/*metabolism ; Humans ; Molecular Sequence Data ; Promoter Regions, Genetic ; RNA, Messenger/genetics ; Receptors, LDL/*genetics/*metabolism ; Sterol Regulatory Element Binding Protein 2/metabolism ; Transcription Factors/*genetics/*metabolism ; p38 Mitogen-Activated Protein Kinases/antagonists & inhibitors

PURPOSE: Healthy, young individuals are known to exhibit circadian variation in urinary functions. However, the effects of chronic circadian disturbance on voiding functions are largely unknown. The present work compared the effects of rotational shifts on the micturition patterns of female nurses to that in female nurses with routine daytime shifts. METHODS: A total of 19 nurses without lower urinary tract symptoms who worked rotational shifts for an average duration of 2 years were recruited. A voiding diary was kept for 9 consecutive days, and the overactive bladder symptom score (OABSS) questionnaire was completed three times, starting 3 days before their night duties until 3 days after completion of their night duties. For comparison, seven nurses with regular shifts completed a 3-day voiding diary and the OABSS questionnaire. RESULTS: Female nurses working rotational shifts had lower overall urine production and had decreased urination frequency and nocturia than female nurses working regular shifts, even when the nurses who worked rotational shifts had a regular night's sleep for at least 7 days. Upon reinitiation of night duty, overall urine production increased significantly, with no significant changes in urgency and frequency. When these nurses returned to daytime duty, the volume of urine decreased but nocturnal urine production remained high, and the incidence of nocturia also increased significantly. However, the effects on OABSS score were not significant under the study design used. CONCLUSIONS: Long-term rotational shifts resulted in adaptive changes such as decreased urine production and frequency in healthy, young female nurses. In addition, their micturition patterns were significantly affected by abrupt changes in their work schedules. Although working in shifts did not increase urgency or frequency of urination in healthy, young female nurses working rotational shifts for an average 2 years, large-scale studies are needed to systematically analyze the influence of shift work timings on micturition in humans.
Appointments and Schedules ; Circadian Rhythm ; Female ; Humans ; Incidence ; Lower Urinary Tract Symptoms ; Nocturia ; Pilot Projects* ; Urinary Bladder, Overactive ; Urination*

PURPOSE: Circadian rhythm affects learning process, memory consolidation, and long-term memory. In this study, the alleviating effect of exercise on circadian rhythm disruption-induced memory deficits was investigated. METHODS: BMAL1 knockdown transgenic mice (BMAL1 TG) were used as the BMAL1-TG group and the BMAL1-TG with treadmill exercise group. Female C57BL/6J mice of the same age were used as the wildtype group and the wildtype with treadmill exercise group. The mice in the treadmill exercise groups performed running on a motorized treadmill under the dark-dark conditions for 8 weeks. Short-term memory, nonspatial object memory, and spatial learning memory were determined using stepdown avoidance test, novel object-recognition test, and radial 8-arm maze test. Immunohistochemistry for doublecortin and 5-bromo-2’-deoxyuridine was conducted for the determination of hippocampal neurogenesis. Using the western blot analysis, we determined the expressions of glucocorticoid receptor (GR) and factors related to the neurogenesis and memory consolidation, such as brain-derived neurotrophic factor, tyrosine kinase B, p44/42 mitogen-activated protein kinase, cyclic AMP-responsive element binding protein, phosphatidylinositol 3-kinase, protein kinas B, protein kinase C alpha, early-growth-response gene 1. RESULTS: Circadian rhythm disruption impaired memory function through inhibiting the expressions of GR and the factors related to neurogenesis and memory consolidation. Treadmill exercise improved memory function via enhancing the expressions of GR and above-mentioned factors. CONCLUSIONS Treadmill exercise acts as the zeitgeber that improves memory function under the circadian rhythm disrupted conditions.