Circadian Locomotor Output Cycle Kaput Research Articles

Quercetin improved hepatic circadian rhythm dysfunction in middle-aged mice fed with vitamin D-deficient diet.

We aimed to determine whether quercetin is capable of improving circadian rhythm and metabolism disorder under vitamin D-deficient condition. Middle-aged mice were randomly divided into four groups, namely, control (CON), vitamin D-deficient diet (VDD), quercetin (Q), and quercetin intervention in vitamin D-deficient diet (VDQ), with a total of 12 weeks' intervention. Mice were sacrificed at zeitgeber time1 (ZT1) and ZT13 time points. At ZT1, circadian locomotor output cycle kaput (CLOCK) protein expression from VDD, Q, and VDQ groups; CRY1 from Q group; and CRY2 from VDD group were significantly lower compared to CON group. The mRNA expression of Sirt1, Bmal1, Clock, Cry1, and Cry2 in VDQ groups, also Bmal1, Clock, and Cry1 from Q group, were significantly decreased compared to CON group. At ZT13, compared to CON group, fasting insulin and homeostasis model assessment-insulin resistance (HOMA-IR) were higher in VDD group; BMAL1 was significantly increased, while CLOCK and CRY1 protein were significantly decreased from VDD group; CLOCK protein from VDQ group was significantly higher compared to CON, VDD, and Q groups, and also, BMAL1 protein expression from VDQ group was elevated compared to CON group. The mRNA expression of Bmal1, Clock, Per2, Cry1, and Cry2 in VDQ groups were significantly increased compared to CON groups. The mRNA expression of Bmal1 from VDQ group was decreased compared to both VDD and Q group. In conclusion, vitamin D-deficient diet resulted in a disordered liver circadian rhythm, and quercetin improved the hepatic circadian desynchronization. Quercetin supplementation might be effective for balancing circadian rhythm under vitamin D-deficient condition.

Molecular Evolution of clock Genes in Vertebrates.

Circadian rhythms not only influence the overall daily routine of organisms but also directly affect life activities to varying degrees. Circadian locomotor output cycle kaput (Clock), the most critical gene in the circadian rhythm feedback system, plays an important role in the regulation of biological rhythms. Here, we aimed to elucidate the evolutionary history of the clock gene family in a taxonomically diverse set of vertebrates, providing novel insights into the evolution of the clock gene family based on 102 vertebrate genomes. Using genome-wide analysis, we extracted 264 clock sequences. In lobe-finned fishes and some basal non-teleost ray-finned fishes, only two clock isotypes were found (clock1 and clock2). However, the majority of teleosts possess three clock genes (two clock1 genes and one clock2 gene) owing to extra whole-genome duplication. The following syntenic analysis confirmed that clock1a, clock1b, and clock2 are conserved in teleost species. Interestingly, we discovered that osteoglossomorph fishes possess two clock2 genes. Moreover, protein sequence comparisons indicate that CLOCK protein changes among vertebrates were concentrated at the N-terminal and poly Q regions. We also performed a dN/dS analysis, and the results suggest that clock1 and clock2 may show distinct fates for duplicated genes between the lobe-finned and ray-finned fish clades. Collectively, these results provide a genome-wide insight into clock gene evolution in vertebrates.

The Circadian Clock Regulates the Expression of the Nuclear Factor Erythroid 2-Related Factor 2 in Acute Kidney Injury following Myocardial Ischemia-Reperfusion in Diabetic Rat

Cardiac surgery-associated acute kidney injury (AKI) is a serious and frequent complication with poor prognosis, and disruption in circadian rhythm shall adversely influence cardiovascular and renal functions via oxidative stress mechanisms. However, the role of circadian clock genes (circadian locomotor output cycle kaput (CLOCK) and brain and muscle aryl hydrocarbon receptor nuclear translocator-like protein-1 (BMAL1)) and its interaction with nuclear factor erythroid 2-related factor 2 (Nrf2) in AKI following myocardial ischemia-reperfusion (MIR) in the diabetic rat has not yet been explored. In this study, rats were divided into the sham (S) group, MIR (M) group, diabetic (D) group, and diabetic+MIR (DM) group. At light (zeitgeber time (ZT) 0) and dark time points (ZT12), rat MIR model was established by occlusion of the left anterior descending coronary artery for 30 min followed by 2 -hour reperfusion, and then renal injury was evaluated. The renal histological changes in the DM group were significantly high compared to other groups; serum creatinine, blood urea nitrogen, and neutrophil gelatinase-associated lipocalin levels, as well as malondialdehyde and 8-iso-prostaglandin-F2α levels in renal tissues of M ZT12 and DM ZT12 subgroups, were significantly higher than those of M ZT0 and DM ZT0 subgroups, individually indicating increased oxidative stress at a dark cycle. Further, Nrf2 protein accumulated in a circadian manner with decreasing levels at night in the DM and M groups. In conclusion, renal injury following MIR was exacerbated in the diabetic rat at night through molecular mechanisms involving transcriptional control of the circadian clock on light-dark activation of Nrf2.

Chronic shift-lag promotes NK cell ageing and impairs immunosurveillance in mice by decreasing the expression of CD122.

Long‐term subjection to shift work increases the risk of cancer. The purpose of the present study was to explore the mechanism by which chronic circadian disruption impairs natural killer (NK) cell immunosurveillance. Mice were subjected to light‐dark reverse every 4 days for 12 weeks to disrupt normal circadian rhythm. NK cell development and function were evaluated by flow cytometry. The mRNA and protein levels of period 1 (per1) and per2 were suppressed, while circadian locomotor output cycle kaput (CLOCK) was increased in the shifted mice, indicating successful generation of the circadian rhythm disruption mouse model. Chronic shift‐lag promoted NK cell ageing, which is likely due to the reduction in Ly49 family receptor expression in shifted NK. We further studied the effects of circadian rhythm disruption on NK cell function. Chronic shift‐lag inhibited NK cell secretion of granular CD107a and interferon gamma. Moreover, chronic shift‐lag attenuated the clearance of MHC‐I–deficient tumour cells by NK cells in vivo and promoted lung metastasis of B16F10 melanomas. Furthermore, chronic shift‐lag reduced NK cell killing function, which may be due to the suppression of Eomes transcription factor expression, which inhibiting the transcription of CD122. In conclusion, our findings suggest that chronic circadian disruption attenuates NK cell cytolytic activity by decreasing the expression of CD122.

The polymorphism of CLOCK gene rs4864548 A>G is associated with susceptibility of Alzheimer’s disease in Chinese population

The aim of this study was to investigate the correlation between polymorphism of circadian locomotor output cycle kaput (CLOCK) gene rs4864548 A/G and susceptibility of Alzheimer’s disease (AD). A total of 296 unrelated AD patients and 423 control subjects were enrolled in the case-control study. Genotypes of apolipoprotein E (APOE) and CLOCK gene rs4864548 A/G were determined by a Polymerase Chain Reaction (PCR) restriction fragment length polymorphism detection method. Our results showed that in the whole sample or APOE ε 4 non-carriers, prevalence of A carriers in CLOCK gene rs4864548 A/G in AD patients was remarkably higher than that in control subjects (in the whole sample: χ2 = 47.614, p < 0.0001; in APOE ε 4 non-carriers: χ2 = 22.493, p < 0.0001). However, among APOE ε 4 carriers, the difference in the prevalence of A carriers in CLOCK gene rs4864548 A/G between AD patients and controls was no statistically significant (χ2 = 0.669, p = 0.379). These findings demonstrate that A carriers in CLOCK gene rs 4864548 A/G were closely related to a high susceptibility of AD among APOE ε 4 non-carriers while the functional polymorphism of CLOCK gene rs4864548 A/G was not associated with the susceptibility of AD among APOE ε 4 carriers.

Polymorphism of circadian clock genes and prophylactic lithium response

The therapeutic action of lithium in bipolar mood disorder may be connected with its effect on biological rhythms. In the present study, an attempt was made to investigate an association between multiple single nucleotide polymorphisms (SNPs) and their haplotypes pertaining to four genes involved in regulation of biological rhythms [circadian locomotor output cycle kaput (CLOCK), aryl hydrocarbon receptor nuclear translocator-like (ARNTL), timeless circadian clock (TIMELESS), period circadian clock 3 (PER 3)], and the efficacy of lithium prophylaxis. The study was performed on 115 patients with bipolar mood disorder (45 males, 70 females) with a mean age of 52 ± 12 years, with lithium prophylaxis for 22 ± 8 years, recruited from the outpatients in the Department of Psychiatry, Poznan University of Medical Sciences. The assessment of the lithium prophylactic response was made retrospectively using the Alda scale. Genotyping was done for nine SNPs of the CLOCK gene, 18 SNPs of the ARNTL gene, six SNPs of the timeless circadian clock (TIM) gene, and nine SNPs of the PER3 gene. An association with the degree of lithium prophylaxis was found for six SNPs and three haplotype blocks of the ARNTL gene, and two SNPs and one haplotype block of the TIM gene. No association with SNPs or haplotypes of the CLOCK and PER3 genes was observed. The results suggest that the ARNTL and TIM genes may be associated with the lithium prophylactic response in bipolar illness. This association may be related to the role of these genes in the predisposition to bipolar mood disorder. Of special interest may be polymorphisms of these genes involved both in the predisposition to bipolar mood disorder and the lithium response.

The Polymorphism of CLOCK Gene 3111T/C C>T Is Associated With Susceptibility of Alzheimer Disease in Chinese Population

ObjectivesIn the present study, it was examined whether polymorphism of circadian locomotor output cycle kaput (CLOCK) gene 3111T/C was associated with susceptibility of Alzheimer disease (AD).MethodsThis study was conducted using...

Polymorphism of CLOCK Gene rs 4580704 C>G Is Associated with Susceptibility of Alzheimer’s Disease in a Chinese Population

The association of polymorphism of circadian locomotor output cycle kaput (CLOCK) gene rs 4580704 C/G with susceptibility of Alzheimer's disease (AD) was examined in the present study. This was a case/control study and investigated the association of polymorphism of CLOCK gene rs 4580704 C/G with susceptibility of AD. Genotypes of apolipoprotein E (APOE) and CLOCK gene rs 4580704 C/G were determined by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) detection method. This study was comprised of 296 unrelated AD patients and 423 controls. We performed an analysis the association of polymorphism of CLOCK gene rs 4580704 C/G with susceptibility of AD. In the whole sample or APOEε4 noncarriers, prevalence of C carriers in CLOCK gene rs 4580704 in AD patients was significantly higher than incontrols (in the whole sample: χ(2)= 13.773, p <0.0001; in APOEε4 noncarriers: χ(2)= 51.588, p <0.0001). However, among APOEε4 carriers, prevalence of C carriers in CLOCK gene rs 4580704 between patients and controls was not statistically significant (χ(2)= 0.753, p= 0.386). Among APOEε4 noncarriers, C carriers in CLOCK gene rs 4580704 were associated with a high susceptibility of AD; however, among APOEε4 carriers the functional polymorphism of clock gene rs 4580704 C/G was not associated with AD susceptibility.