The human circadian clock from health to economics

TW68, cryptochromes stabilizer, regulates fasting blood glucose levels in diabetic ob/ob and high fat-diet-induced obese mice

Cryptochromes (CRYs), transcriptional repressors of the circadian clock in mammals, inhibit cAMP production when glucagon activates G-protein coupled receptors. Therefore, molecules that modulate CRYs have the potential to regulate gluconeogenesis. In this study, we discovered a new molecule called TW68 that interacts with the primary pockets of mammalian CRY1/2, leading to reduced ubiquitination levels and increased stability. In cell-based circadian rhythm assays using U2OS Bmal1-dLuc cells, TW68 extended the period length of the circadian rhythm. Additionally, TW68 decreased the transcriptional levels of two genes, Phosphoenolpyruvate carboxykinase 1 (PCK1) and Glucose-6-phosphatase (G6PC), which play crucial roles in glucose biosynthesis during glucagon-induced gluconeogenesis in HepG2 cells. Oral administration of TW68 in mice showed good tolerance, a good pharmacokinetic profile, and remarkable bioavailability. Finally, when administered to fasting diabetic animals from ob/ob and HFD-fed obese mice, TW68 reduced blood glucose levels by enhancing CRY stabilization and subsequently decreasing the transcriptional levels of Pck1 and G6pc. These findings collectively demonstrate the antidiabetic efficacy of TW68 in vivo, suggesting its therapeutic potential for controlling fasting glucose levels in the treatment of type 2 diabetes mellitus.

Sarm1 Regulates Circadian Rhythm Disorder in Alzheimer's Disease in Mice

BACKGROUND

Sarm1 (Sterile alpha and TIR motif-containing 1) is a key protein that regulates neurodegenerative pathologies. Alzheimer's disease (AD) is highly associated with neurodegenerative lesions and biorhythmic disturbances.

OBJECTIVE

This study aims to decipher the role of Sarm1 in AD-induced circadian rhythm disturbances and AD progression.

METHODS

Open field and water maze tests were used to assess the cognitive function of mice. Thioflavin-S staining was used to assess amyloid-β (Aβ) plaque deposition in the hippocampus and cortex. Rhythmic waveform of home cage activity and temperature was recorded to evaluate circadian rhythm. Expression of clock molecules including Bmal1 and Per2 in the hippocampus were analyzed using western blot and real-time PCR. Further, HT22 cells with Sam1 knockout were treated with Aβ 31-35 treatment to initiate circadian rhythm disorder in the cellular level to assess the changes in Bmal1 and Per2.

RESULTS

Our data suggested that Sarm1 deficiency rescued cognitive disorder, decreased Aβ plaque deposition in the hippocampus and cortex, inhibited astrocyte activation, improved circadian rhythm, altered clock molecule expression in the cortex and hippocampus in APP/PS1 mice.

CONCLUSION

Sarm1 attenuates circadian rhythm disturbances and reduces AD progression. These data support the potential use of Sarm1 as a therapeutic target to improve circadian rhythm to impede AD progression.

Circadian rhythm disruption exacerbates Th2-like immune response in murine allergic airway inflammation

BACKGROUND

Chronic jet lag (CJL)-induced circadian rhythm disruption (CRD) is positively correlated with an increased risk of allergic diseases. However, little is known about the mechanism involved in allergic rhinitis (AR).

METHODS

Aberrant light/dark cycles-induced CRD mice were randomly divided into negative control (NC) group, AR group, CRD+NC group, and CRD+AR group (n = 8/group). After ovalbumin (OVA) challenge, nasal symptom scores were recorded. The expression of Occludin and ZO-1 in both nasal mucosa and lung tissues was detected by reverse transcription-quantitative polymerase chain reaction (RT-PCR) and immunohistochemical staining. The level of OVA-specific immunoglobulin E (sIgE) and T-helper (Th)-related cytokines in the plasma was measured by enzyme-linked immunosorbent assay (ELISA), and the proportion of Th1, Th2, Th17, and regulatory T cell (Treg) in splenocytes was evaluated by flow cytometry.

RESULTS

The nasal symptom score in the CRD+AR group was significantly higher than those in the AR group with respect to eosinophil infiltration, mast cell degranulation, and goblet cell hyperplasia. The expression of ZO-1 and Occludin in the nasal mucosa and lung tissues in the CRD+AR group were significantly lower than those in the AR group. Furthermore, Th2 and Th17 cell counts from splenocytes and OVA-sIgE, interleukin 4 (IL-4), IL-6, IL-13, and IL-17A levels in plasma were significantly increased in the CRD+AR group than in the AR group, whereas Th1 and Treg cell count and interferon γ (IFN-γ) level were significantly decreased in the CRD+AR group.

CONCLUSION

CRD experimentally mimicked CJL in human activities, could exacerbate local and systemic allergic reactions in AR mice, partially through decreasing Occludin and ZO-1 level in the respiratory mucosa and increasing Th2-like immune response in splenocytes.

Recommendations for daytime, evening, and nighttime indoor light exposure to best support physiology, sleep, and wakefulness in healthy adults

Ocular light exposure has important influences on human health and well-being through modulation of circadian rhythms and sleep, as well as neuroendocrine and cognitive functions. Prevailing patterns of light exposure do not optimally engage these actions for many individuals, but advances in our understanding of the underpinning mechanisms and emerging lighting technologies now present opportunities to adjust lighting to promote optimal physical and mental health and performance. A newly developed, international standard provides a SI-compliant way of quantifying the influence of light on the intrinsically photosensitive, melanopsin-expressing, retinal neurons that mediate these effects. The present report provides recommendations for lighting, based on an expert scientific consensus and expressed in an easily measured quantity (melanopic equivalent daylight illuminance (melaponic EDI)) defined within this standard. The recommendations are supported by detailed analysis of the sensitivity of human circadian, neuroendocrine, and alerting responses to ocular light and provide a straightforward framework to inform lighting design and practice.

The interindividual variability of sleep timing and circadian phase in humans is influenced by daytime and evening light conditions

Human cognitive functioning shows circadian variations throughout the day. However, individuals largely differ in their timing during the day of when they are more capable of performing specific tasks and when they prefer to sleep. These interindividual differences in preferred temporal organization of sleep and daytime activities define the chronotype. Since a late chronotype is associated with adverse mental and physical consequences, it is of vital importance to study how lighting environments affect chronotype. Here, we use a mathematical model of the human circadian pacemaker to understand how light in the built environment changes the chronotype distribution in the population. In line with experimental findings, we show that when individuals spend their days in relatively dim light conditions, this not only results in a later phase of their biological clock but also increases interindividual differences in circadian phase angle of entrainment and preferred sleep timing. Increasing daytime illuminance results in a more narrow distribution of sleep timing and circadian phase, and this effect is more pronounced for longer photoperiods. The model results demonstrate that modern lifestyle changes the chronotype distribution towards more eveningness and more extreme differences in eveningness. Such model-based predictions can be used to design guidelines for workplace lighting that help limiting circadian phase differences, and craft new lighting strategies that support human performance, health and wellbeing.

Circadian Biology in Obstructive Sleep Apnea

Obstructive sleep apnea (OSA) is a complex process that can lead to the dysregulation of the molecular clock, as well as 24 h rhythms of sleep and wake, blood pressure, and other associated biological processes. Previous work has demonstrated crosstalk between the circadian clock and hypoxia-responsive pathways. However, even in the absence of OSA, disrupted clocks can exacerbate OSA-associated outcomes (e.g., cardiovascular or cognitive outcomes). As we expand our understanding of circadian biology in the setting of OSA, this information could play a significant role in the diagnosis and treatment of OSA. Here, we summarize the pre-existing knowledge of circadian biology in patients with OSA and examine the utility of circadian biomarkers as alternative clinical tools.

Disrupted rhythms of life, work and entertainment and their associations with psychological impacts under the stress of the COVID-19 pandemic: A survey in 5854 Chinese people with different sociodemographic backgrounds

BACKGROUND & AIM

The coronavirus disease 2019 (COVID-19) pandemic has affected the life and work of people worldwide. The present study aimed to evaluate the rhythm disruptions of life, work, and entertainment, and their associations with the psychological impacts during the initial phase of the COVID-19 pandemic.

METHOD

A cross-sectional study was conducted from the 10th to 17th March 2020 in China. A structured e-questionnaire containing general information, the Chinese version of Brief Social Rhythm Scale, and Zung's self-rating scales of depression and anxiety (SDS and SAS) was posted and collected online through a public media (i.e. EQxiu online questionnaire platform). Scores in sleeping, getting up, and socializing (SGS) rhythm and eating, physical practice, and entertainment (EPE) rhythm were compared among and between participants with different sociodemographic backgrounds including gender, age, education, current occupation, annual income, health status, and chronic disease status. Correlations of SDS and SAS with SGS-scale and EPE-scale were also analyzed.

RESULTS

Overall, 5854 participants were included. There were significant differences in the scores of SGS-scale and EPE-scale among people with different sociodemographic backgrounds. The scores were significantly higher in the groups with female gender, low education level, lower or higher than average income, poor health status, ages of 26-30 years or older than 61 years, nurses and subjects with divorce or widow status. There were also significant differences in SAS and SDS scores among people with different sociodemographic backgrounds (all P< 0.05). The overall prevalence of depression and anxiety was 24.3% and 12.6%, respectively, with nurses having the highest rates of depression (32.94%) and anxiety (18.98%) among the different occupational groups. SGS-scale was moderately correlated with SDS and SAS, and disruption of SGS rhythm was an independent risk factor for depression and anxiety.

CONCLUSION

Social rhythm disruption was independently associated with depression and anxiety. Interventions should be applied to people vulnerable to the rhythm disruption during the COVID-19 pandemic.

Modulations in irradiance directed at melanopsin, but not cone photoreceptors, reliably alter electrophysiological activity in the suprachiasmatic nucleus and circadian behaviour in mice

Intrinsically photosensitive retinal ganglion cells convey intrinsic, melanopsin-based, photoreceptive signals alongside those produced by rods and cones to the suprachiasmatic nucleus (SCN) circadian clock. To date, experimental data suggest that melanopsin plays a more significant role in measuring ambient light intensity than cone photoreception. Such studies have overwhelmingly used diffuse light stimuli, whereas light intensity in the world around us varies across space and time. Here, we investigated the extent to which melanopsin or cone signals support circadian irradiance measurements in the presence of naturalistic spatiotemporal variations in light intensity. To address this, we first presented high- and low-contrast movies to anaesthetised mice whilst recording extracellular electrophysiological activity from the SCN. Using a mouse line with altered cone sensitivity (Opn1mw^R mice) and multispectral light sources we then selectively varied irradiance of the movies for specific photoreceptor classes. We found that steps in melanopic irradiance largely account for the light induced-changes in SCN activity over a range of starting light intensities and in the presence of spatiotemporal modulation. By contrast, cone-directed changes in irradiance only influenced SCN activity when spatiotemporal contrast was low. Consistent with these findings, under housing conditions where we could independently adjust irradiance for melanopsin versus cones, the period lengthening effects of constant light on circadian rhythms in behaviour were reliably determined by melanopic irradiance, regardless of irradiance for cones. These data add to the growing evidence that modulating effective irradiance for melanopsin is an effective strategy for controlling the circadian impact of light.

Period2 gene regulates diurnal changes of nasal symptoms in an allergic rhinitis mouse model

Background

Allergic rhinitis (AR) symptoms exhibit prominent 24‐hour variations associated with the biological clock. Although endogenous glucocorticoids synchronize circadian oscillator in the nasal mucosa, the precise mechanism of AR remains unclear. Therefore, using a mouse model, we investigated the association between circadian‐clock genes and AR symptoms at various time‐points.

Methods

Based on the rhythmic secretion of corticosterone levels, we chose 2 time‐points, ZT4 (10:00 AM) and ZT16 (10:00 PM), to observe dynamic changes of nasal symptoms, immunologic responses, and circadian‐clock gene period (Per) expressions.

Results

In the AR group, nasal symptom scores at ZT4 were significantly higher than at ZT16, with a greater increase in eosinophils, mast cells, and total immunoglobulin E levels at ZT4. The scores had a negative correlation with fluctuation of corticosterone levels. T‐helper 1 (Th1) cell counts and interferon‐γ levels decreased significantly at ZT4 compared with ZT16 in the AR group, whereas Th2 cells; Th17 cells; and interleukin (IL)‐4, ‐13, and ‐17A levels increased significantly at ZT4 compared with ZT16. Furthermore, Per2 gene expression levels were attenuated at ZT4 and elevated at ZT16, but correlated negatively with Th2 and Th17 responses associated with Gata3 and Rorγt expression levels that were enhanced at ZT4 and reduced at ZT16 in the AR group.

Conclusion

Our results suggest that the Per2 gene may influence diurnal variations of AR symptom severity, partially through its possible anti‐inflammatory effect on the circadian regulation of GATA3 and RORγt levels in immune cells. This further demonstrates the neural‐immune‐endocrinal mechanism of circadian rhythm in AR and sheds new light on chronotherapeutic approaches to AR.

Resetting the Aging Clock: Implications for Managing Age-Related Diseases

Worldwide, individuals are living longer due to medical and scientific advances, increased availability of medical care and changes in public health policies. Consequently, increasing attention has been focused on managing chronic conditions and age-related diseases to ensure healthy aging. The endogenous circadian system regulates molecular, physiological and behavioral rhythms orchestrating functional coordination and processes across tissues and organs. Circadian disruption or desynchronization of circadian oscillators increases disease risk and appears to accelerate aging. Reciprocally, aging weakens circadian function aggravating age-related diseases and pathologies. In this review, we summarize the molecular composition and structural organization of the circadian system in mammals and humans, and evaluate the technological and societal factors contributing to the increasing incidence of circadian disorders. Furthermore, we discuss the adverse effects of circadian dysfunction on aging and longevity and the bidirectional interactions through which aging affects circadian function using examples from mammalian research models and humans. Additionally, we review promising methods for managing healthy aging through behavioral and pharmacological reinforcement of the circadian system. Understanding age-related changes in the circadian clock and minimizing circadian dysfunction may be crucial components to promote healthy aging.

Circadian ontogeny through the lens of nonparametric variables of actigraphy

Studies focusing on human rhythmicity show that human circadian rhythm suffers constant changes across lifespan. Changes in rest-activity patterns can be studied through nonparametric variables of actigraphy: L5 (an individual's least active 5 h), M10 (an individual's most active 10 h) and RA (relative amplitude of the rest-activity rhythm). The variable RA is the normalized difference between L5 and M10 - the higher the RA, the greater the difference between these two variables. This study used the data bank of the Human Chronobiology Laboratory of Federal University of Paraná (Brazil). It analyzed actimetric data of 93 children between 4 and 11 years of age in their naturalistic context in order to describe the development of nonparametric variables. Correlation between age and L5 was significantly negative (rho = - 0.29, p = 0.004), while correlation between age and RA was significantly positive (rho = 0.31, p = 0.003). The variables M10, sL5 (start of L5) and sM10 (start of M10) did not show significant correlation to age. Furthermore, there were no statistical differences between genders. The population of this study, healthy children, has been poorly assessed by similar literature. Through our results, we have demonstrated that, as children age, L5 significantly decreases, which reflects a smaller fragmentation of circadian rhythm. As an expected consequence, RA significantly increases. In other words, these nonparametric variables of actimetry successfully demonstrate that children tend to reduce nocturnal activity as they age, a phenomenon that reflects the ongoing consolidation of circadian rhythm.