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Purpose: To examine nocturnal sleep patterns, napping behaviors, and subjective wellness responses of elite water polo players within an in-season week and to identify whether sleeping patterns differ between men and women. Methods: Sleep characteristics of 10 male and 17 female professional water polo players were objectively assessed during 1 week of the in-season period, including 5 training days, 1 match day, and 1 day of rest. Internal load (rating of perceived exertion × duration of training or match) was assessed 30 minutes posttraining or postmatch, and the total quality of recovery was recorded every morning. A series of multilevel models were used to analyze the data. Results: Time in bed and wake-up time were earlier on both training (P <.001) and rest days (P <.001) than on the day of the match. Internal workload did not predict any of the players' sleeping patterns. Midday naps predicted less time in bed (P =.03) and likely less sleep time (P =.08). The total quality of recovery was predicted only by the total sleep time (P <.01). Women exhibited higher sleep efficiency (P <.001), less waking after sleep onset (P =.01), and a lower number of awakenings (P =.02) than men. Conclusions: The current results indicate that the nocturnal sleep patterns of elite water polo players are not associated with internal load and that women display better nocturnal sleep quality compared with men. As long naps interfere with nocturnal sleep, and total nocturnal sleep time predicts total quality of recovery, we suggest that athletes follow hygiene sleep strategies to facilitate adequate nocturnal sleep and next-day recovery. [ABSTRACT FROM AUTHOR]

The objective of this 18-month walking intervention was to evaluate the effect on rest–activity rhythm (RAR) for older adults with mild-to-moderate dementia (65.8% female; aged M = 82.4 [SD = 6.5]). The intervention group (n = 44) was intended to walk 30 min, five times per week for 18 months. The control group (n = 35) received sedentary activities or usual care. RAR was measured at baseline to after 18 months and five times in between actigraphy outcome variables (interdaily stability, intradaily variability, relative amplitude, activity 10 most active hours, and activity 5 least active hours). Hierarchical mixed model analyses revealed no significant intervention effects (with or without baseline confounders as covariate) on RAR. However, participants in the intervention group were able to significantly increase their daily life activity (activity 10 most active hours) from the onset of the preceding measurement, b = 0.10, t(239.32) = 2.36, p =.019. More research is warranted to study the effect of regular walks on older persons with dementia whose RAR is worst at baseline. [ABSTRACT FROM AUTHOR]

Huntingtons Disease (HD) is a neurodegenerative disorder caused by an autosomal-dominant mutation in the huntingtin gene, which manifests with a triad of motor, cognitive and psychiatric declines. Individuals with HD often present with disturbed sleep/wake cycles, but it is still debated whether altered circadian rhythms are intrinsic to its aetiopathology or a consequence. Conversely, it is well established that sleep/wake disturbances, perhaps acting in concert with other pathophysiological mechanisms, worsen the impact of the disease on cognitive and motor functions and are a burden to the patients and their caretakers. Currently, there is no cure to stop the progression of HD, however, preclinical research is providing cementing evidence that restoring the fluctuation of the circadian rhythms can assist in delaying the onset and slowing progression of HD. Here we highlight the application of circadian-based interventions in preclinical models and provide insights into their potential translation in clinical practice. Interventions aimed at improving sleep/wake cycles synchronization have shown to improve motor and cognitive deficits in HD models. Therefore, a strong support for their suitability to ameliorate HD symptoms in humans emerges from the literature, albeit with gaps in our knowledge on the underlying mechanisms and possible risks associated with their implementation.

Chrononutrition is a rapidly evolving field of nutritional epidemiology that addresses the complex relationship between temporal eating patterns, circadian rhythms, and metabolic health, but most prior research has focused on the cardiometabolic consequences of time-restricted feeding and intermittent fasting. The purpose of this topical review is to summarize epidemiological evidence from observational and intervention studies regarding the role of chrononutrition metrics related to eating timing and regularity in cardiometabolic health preservation and cardiovascular disease prevention. Observational studies are limited due to the lack of time-stamped diet data in most population-based studies. Findings from cohort studies generally indicate that breakfast skipping or the later timing of the first eating occasion, a later lunch and dinner, and a greater proportion of caloric intake consumed in the evening are associated with adverse cardiometabolic outcomes, including higher risk for coronary heart disease, hypertension, type 2 diabetes, obesity, dyslipidemia, and systemic inflammation. Randomized controlled trials are also limited, as most in the field of chrononutrition focus on the cardiometabolic consequences of time-restricted feeding. Overall, interventions that shift eating timing patterns to earlier in the day and that restrict evening caloric intake tend to have protective effects on cardiometabolic health, but small sample sizes and short follow-up are notable limitations. Innovation in dietary assessment approaches, to develop low-cost validated tools with acceptable participant burden that reliably capture chrononutrition metrics, is needed for advancing observational evidence. Culturally responsive pragmatic intervention studies with sufficiently large and representative samples are needed to understand the impact of fixed and earlier eating timing schedules on cardiometabolic health. Additional research is warranted to understand the modifiable determinants of temporal eating patterns, to investigate the role of chrononutrition in the context of other dimensions of diet (quantity, quality, and food and nutrition security) in achieving cardiometabolic health equity, and to elucidate underlying physiological mechanisms.

Purpose: Transmeridian travel is common for elite athletes participating in competitions and training. However, this travel can lead to circadian misalignment wherein the internal biological clock becomes desynchronized with the light–dark cycle of the new environment, resulting in performance decrement and potential negative health consequences. Existing literature extensively discusses recommendations for managing jet lag, predominantly emphasizing light-based interventions to synchronize the internal clock with the anticipated time at the destination. Nevertheless, visually impaired (VI) athletes may lack photoreceptiveness, diminishing or nullifying the effectiveness of this therapy. Consequently, this invited commentary explores alternative strategies for addressing jet lag in VI athletes. Conclusions: VI athletes with light perception but reduced visual acuity or visual fields may still benefit from light interventions in managing jet lag. However, VI athletes lacking a conscious perception of light should rely on gradual shifts in behavioral factors, such as meal timing and exercise, to facilitate the entrainment of circadian rhythms to the destination time. Furthermore, interventions like melatonin supplementation may prove useful during and after travel. In addition, it is recommended that athlete guides adopt phase-forward or phase-back approaches to synchronize with the athlete, aiding in jet-lag management and optimizing performance. [ABSTRACT FROM AUTHOR]

Paradoxical leadership—the integration of leadership behaviors that are seemingly contradictory, but nevertheless interdependent—is becoming increasingly important in today's complex and turbulent business environments. Despite evidence for the positive consequences of paradoxical leadership, little research has examined how and when leaders can effectively integrate or reconcile opposing leadership behaviors. Two of the most fundamental paradoxical challenges that leaders face include the need to integrate control and empowerment, as well as reconciling collective rules with followers' individual needs. In this article, we advance a circadian theory of paradoxical leadership that outlines how leaders can combine episodic thinking with circadian principles to achieve a dynamic equilibrium between the opposing poles of these two leadership paradoxes. Our temporal framework explains how leaders can effectively structure paradoxical leadership episodes that leverage their own and their followers' circadian processes within a broader framework of situation-driven leadership. In doing so, we contribute to future research by providing a novel circadian perspective on how paradoxical tensions in organizations can be reconciled within the constraints of situational demands. [ABSTRACT FROM AUTHOR]

STUDY OBJECTIVES: This single-arm, mixed-methods, pilot study examined the feasibility and preliminary efficacy of an adapted version of the transdiagnostic intervention for sleep and circadian dysfunction (TranS-C) on multidimensional sleep health (MDSH) in a sample of adults with excess weight and suboptimal sleep health. METHODS: Participants received up to eight, weekly, remotely delivered, tailored TranS-C sessions. At pre- and post-intervention, the Pittsburgh Sleep Quality Index, Epworth Sleepiness Scale, and 7 days of Fitbit data were used to evaluate changes in sleep dimensions (regularity, alertness, timing, satisfaction, duration, and efficiency) and the composite MDSH score. Study feasibility examined recruitment, data collection, and intervention engagement (completion of core TranS-C sessions). Acceptability of the intervention was assessed with semi-structured interviews, which were analyzed using thematic analysis. RESULTS: From 85 referrals, 11 individuals were eligible, and 10 completed the study. All intervention participants completed the measures needed to calculate their composite MDSH score and completed the core intervention sessions. Themes from interviews support the interventions remote delivery approach, applicability of the information provided, and impact on self-reported health. The intervention resulted in a large improvement in the mean composite MDSH score (Cohens d = 1.17). Small-to-large effects were also observed for individual sleep health dimensions except for timing. CONCLUSIONS: Adapted TranS-C is acceptable for adults with excess weight and suboptimal sleep health and may be effective at improving short-term MDSH. With changes to recruitment methods, a larger study is feasible. Limitations include the small sample size and the lack of a control condition.

Background: Sleep regularity has been linked to a risk of arterial stiffness (AS). However, the association between sleep regularity indicators, which reflect 24-hour sleep variability, and AS has not yet been examined. Methods: We analyzed data from 516 adults, aged 40–65 years (the median age of 51 years), from the 'Follow-up Study of Sleep Characteristics and Chronic Diseases in the Middle-aged and Elderly Population in Guizhou Province'. Participants underwent assessments of AS (OMRON HBP-8000, baPWV ≥ 1400 cm/s) and sleep (wrist smart band (Honor band 5i) for ≥ 7 days). Logistic regression was utilized to evaluate the odds ratio (OR) and 95% confidence interval (CI) of the association between sleep regularity and AS. Results: A total of 516 people were included in this study, of which 279 (54.07%) were in the AS group. The univariate results showed that the AS group (Median 71.18) had lower SRI compared to the No-AS group (Median 75.00) (p < 0.001). The multifactorial results showed participants with higher SRI scores were more likely to have a lower risk of AS compared to those with lower SRI scores (ORQ4 VS. Q1=0.46, 95%CI: 0.25–0.85, p = 0.013). The SRI effect was more pronounced in male (ORQ4 VS. Q1=0.28, 95%CI: 0.12–0.69, p = 0.005), snoring populations (ORQ4 VS. Q1=0.13, 95%CI: 0.04–0.48, p = 0.002), and non-retired populations (ORQ4 VS. Q1=0.45, 95%CI: 0.22–0.92, p = 0.028). Conclusions: The present findings indicated that the effect between SRI and AS may be more sensitive than the standard deviation of sleep duration as well as the standard deviation of sleep onset. [ABSTRACT FROM AUTHOR]

Disrupted sleep and rest-activity pattern are common clinical features in depressed individuals. This meta-analysis compared sleep and circadian rest-activity rhythms in people with major depressive disorder (MDD) or depressive symptoms and healthy controls. Eligible studies were identified in five databases up to December 2023. The search yielded 53 studies with a total of 11,115 participants, including 4000 depressed participants and 7115 healthy controls. Pooled meta-analyses demonstrated that depressed individuals have significantly longer sleep latency (SMD = 0.23, 95 % CI: 0.12 to 0.33) and wake time after sleep onset (SMD = 0.37, 95 % CI: 0.22 to 0.52), lower sleep efficiency (SMD = −0.41, 95 % CI: −0.56 to −0.25), more nocturnal awakenings (SMD = 0.58, 95 % CI: 0.29 to 0.88), lower MESOR (SMD = −0.54, 95 % CI: −0.81 to −0.28), amplitude (SMD = −0.33, 95 % CI: −0.57 to −0.09), and interdaily stability (SMD = −0.17, 95 % CI: −0.28 to −0.05), less daytime (SMD = −0.79, 95 % CI: −1.08 to −0.49) and total activities (SMD = −0.89, 95 % CI: −1.28 to −0.50) when compared with healthy controls. Most of the included studies reported separate sleep and activity parameters instead of 24-hour rest-activity rhythms. The variabilities among actigraphy devices and the types of participants recruited also impede precise comparisons. The findings emerging from this study offered a better understanding of sleep and rest-activity rhythm in individuals with MDD or depressive symptoms. Future studies could advocate for deriving objective, distinctive 24-hour rest-activity profiles contributing to the risk of depression. CRD42021259780. • The review included 53 new studies up to December 2023. • Depressed individuals reported significantly poorer sleep than healthy controls. • Depressed individuals had disrupted circadian rest-activity rhythms. • Actigraphy has wide reaching and cost-effective public mental health implication. • Future studies can identify objective, distinctive 24-h rest-activity profiles in depression. [ABSTRACT FROM AUTHOR]

Background: Altered meal timing patterns can disrupt the circadian system and affect metabolism. Our aim was to describe sex-specific chrono-nutritional patterns, assess their association with body mass index (BMI) and investigate the role of sleep in this relationship. Methods: We used the 2018 questionnaire data from the population-based Genomes for Life (GCAT) (n = 7074) cohort of adults aged 40–65 in Catalonia, Spain, for cross-sectional analysis and its follow-up questionnaire data in 2023 (n = 3128) for longitudinal analysis. We conducted multivariate linear regressions to explore the association between mutually adjusted meal-timing variables (time of first meal, number of eating occasions, nighttime fasting duration) and BMI, accounting for sleep duration and quality, and additional relevant confounders including adherence to a Mediterranean diet. Finally, cluster analysis was performed to identify chrono-nutritional patterns, separately for men and women, and sociodemographic and lifestyle characteristics were compared across clusters and analyzed for associations with BMI. Results: In the cross-sectional analysis, a later time of first meal (β 1 h increase = 0.32, 95% CI 0.18, 0.47) and more eating occasions (only in women, β 1 more eating occasion = 0.25, 95% CI 0.00, 0.51) were associated with a higher BMI, while longer nighttime fasting duration with a lower BMI (β 1 h increase=-0.27, 95% CI -0.41, -0.13). These associations were particularly evident in premenopausal women. Longitudinal analyses corroborated the associations with time of first meal and nighttime fasting duration, particularly in men. Finally, we obtained 3 sex-specific clusters, that mostly differed in number of eating occasions and time of first meal. Clusters defined by a late first meal displayed lower education and higher unemployment in men, as well as higher BMI for both sexes. A clear "breakfast skipping" pattern was identified only in the smallest cluster in men. Conclusions: In a population-based cohort of adults in Catalonia, we found that a later time of first meal was associated with higher BMI, while longer nighttime fasting duration associated with a lower BMI, both in cross-sectional and longitudinal analyses. [ABSTRACT FROM AUTHOR]

Circadian clock properties vary between individuals and relate to variation in entrained timing in captivity. How this variation translates into behavioural differences in natural settings, however, is poorly understood. Here, we tested in great tits whether variation in the free‐running period length (tau) under constant dim light (LL) was linked to the phase angle of the entrained rhythm (“chronotype”) in captivity and in the wild, as recently indicated in our study species. We also assessed links between tau and the timing of first activity onset and offset under LL relative to the last experienced light–dark (LD) cycle. We kept 66 great tits, caught in two winters, in LL for 14 days and subsequently released them with a radio transmitter back to the wild, where their activity and body temperature rhythms were tracked for 1 to 22 days. For a subset of birds, chronotype was also recorded in the lab before release. Neither wild nor lab chronotypes were related to tau. We also found no correlation between lab and wild chronotypes. However, the first onset in LL had a positive relationship with tau, but only in males. Our results demonstrate that links between tau and phase of entrainment, postulated on theoretical grounds, may not consistently hold under natural conditions, possibly due to strong masking. This calls for more holistic research on how the many components of the circadian system interact with the environment to shape timing in the wild.Wild birds showed chronotypes in the field that were unlinked to their circadian period length tau measured in captivity. In males only, the first onset of activity after exposure to constant dim light did correlate with tau. Our study emphasises the need to investigate clocks in the real world, including a need to better understand masking. [ABSTRACT FROM AUTHOR]

AbstractPurposeMethodsResultsConclusionsAffecting one-third of the population worldwide and increasing, the sight-threatening condition myopia is causing a significant socio-economic burden. To better understand its etiology, recent studies investigated the role of ocular and systemic rhythms, yet results are conflicting. Here we profiled 24-h variations of axial length of the eye and salivary melatonin concentration in young adults with and without myopia and explored the potential impacts of bedtime on these rhythms.A total of 25 healthy young adults (age 25.0 ± 4.8 years, 13 females) completed this study, including 13 myopes (mean spherical equivalent refractive error −2.93 ± 1.46 diopters) and 12 non-myopes (0.14 ± 0.42 diopters). Saliva sample collection and axial length measurements were repeated for seven times over 24 h starting from 8 am. Information on sleep and chronotype was collected at first visit with the Pittsburgh Sleep Quality Index and the Morningness-Eveningness Questionnaire.Significant diurnal rhythms of axial length and salivary melatonin concentration were identified in both refractive groups (both p < 0.001), with no myopia-related rhythm difference (interaction of measurement time-point × myopia, p = 0.9). Late bedtime was associated with altered rhythms (p = 0.009) and smaller diurnal change (p = 0.01) in axial length. Elevated melatonin levels were observed in myopes (p = 0.006) and in late sleepers (p = 0.017).These findings suggest that sleep/wake cycles may be involved in the regulation of axial length rhythms. Further research is needed to determine if there exists a causal relationship between the two. [ABSTRACT FROM AUTHOR]

Microglia, as immune cells in the central nervous system, possess the ability to adapt morphologically and functionally to their environment. Glymphatic system, the principal waste clearance system in the brain, exhibits circadian rhythms. However, the impact of microglia on the glymphatic system function remains unknown. In this study, we explored the intricate relationship between microglia and the glymphatic system. Examining diurnal patterns, we identified synchronized behaviors in glymphatic activity and microglial morphology, peaking during sleep and exhibiting distinct changes in branching complexity. Depleting microglia using PLX5622 or in P2Y12 knockout mice enhanced glymphatic function. Chemogenetic manipulation of microglia demonstrated that activating HM3D improved glymphatic function, while inhibiting HM4D unexpectedly increased microglial complexity. These findings highlight the dynamic influence of microglia on the glymphatic system. [ABSTRACT FROM AUTHOR]

FKBP51, also known as FK506‐binding protein 51, is a molecular chaperone and scaffolding protein with significant roles in regulating hormone signaling and responding to stress. Genetic variants in FKBP5, which encodes FKBP51, have been implicated in a growing number of neuropsychiatric disorders, which has spurred efforts to target FKBP51 therapeutically. However, the molecular mechanisms and sub‐anatomical regions influenced by FKBP51 in these disorders are not fully understood. In this study, we aimed to examine the impact of Fkbp5 ablation using circadian phenotyping and molecular analyses. Our findings revealed that the lack of FKBP51 did not significantly alter circadian rhythms, as detected by wheel‐running activity, but did offer protection against stress‐mediated disruptions in rhythmicity in a sex‐dependent manner. Protein changes in Fkbp5 KO mice, as measured by histology and proteomics, revealed alterations in a brain region‐ and sex‐dependent manner. Notably, regardless of sex, aged Fkbp5 KOs showed elevated MYCBP2, FBXO45, and SPRYD3 levels, which are associated with neuronal‐cell adhesion and synaptic integrity. Additionally, pathways such as serotonin receptor signaling and S100 family signaling were differentially regulated in Fkbp5 KO mice. Weighted protein correlation network analysis identified protein networks linked with synaptic transmission and neuroinflammation. The information generated by this work can be used to better understand the molecular changes in the brain during aging and in the absence of Fkbp5, which has implications for the continued development of FKBP51‐focused therapeutics for stress‐related disorders. [ABSTRACT FROM AUTHOR]

Viruses of eukaryotic algae have become an important research focus due to their role(s) in nutrient cycling and top-down control of algal blooms. Omics-based studies have identified a boom of genomic and transcriptional potential among the Nucleocytoviricota, a phylum of large dsDNA viruses which have been shown to infect algal and non-algal eukaryotes. However, little is understood regarding the infection cycle of these viruses, particularly in how they take over a metabolically active host and convert it into a virocell state. Of particular interest are the roles light and the diel cycle play in virocell development. Yet despite such a large proportion of Nucleocytoviricota infecting phototrophs, little work has been done to tie infection dynamics to the presence, and absence, of light. Here, we examined the role of the diel cycle on the physiological and transcriptional state of the pelagophyte Aureococcus anophagefferens while undergoing infection by Kratosvirus quantuckense strain AaV through flow cytometry and differential expression analyses. Our observations demonstrate how infection by the virus interrupts the diel growth and division of this cell strain, and that infection further complicates the system by enhancing export of cell biomass. Furthermore, these analyses reinforce the expectation that viral activity is heavily associated with the diel cycle. [ABSTRACT FROM AUTHOR]

Viruses are abundant in the ocean and influence both the composition of marine communities and biogeochemical cycles. Despite their high abundance, production rates of distinct virus taxa in the environment are largely unknown. Here, we investigated production dynamics of T4-like cyanophages and compared them to those of the total dsDNA virioplankton community in two adjacent eddies of opposite polarity in the North Pacific Subtropical Gyre. Virioplankton production rateswere 3-fold higher in the cyclonic than in the anticyclonic eddy, potentially due to higher metabolic activity of their bacterial hosts in the cyclone, and had similar virus production rates during the day and night in the cyclone. In contrast, T4-like cyanophages had similar production rates in the two eddies but showed approximately 4-fold higher production rates at night than during the day, potentially due to a combination of greater infection, increased burst size and more cyanophages completing their infection cycle at night. These findings suggest that virioplankton community production is affected more by spatially differentiated environmental conditions while T4-like cyanophage production is more affected over the diel cycle. Differences in production for the T4-like cyanophages relative to the virioplankton community indicate that spatial variability at the mesoscale differentially impact distinct components of the virioplankton. [ABSTRACT FROM AUTHOR]

The circadian clock of cyanobacteria, which predicts daily environmental changes, typically includes a standard oscillator consisting of proteins KaiA, KaiB, and KaiC. However, several cyanobacteria have diverse Kai protein homologs of unclear function. In particular, Synechocystis sp. PCC 6803 harbours, in addition to a canonical kaiABC gene cluster (named kaiAB1C1), two further kaiB and kaiC homologs (kaiB2, kaiB3, kaiC2, kaiC3). Here, we identify a chimeric KaiA homolog, named KaiA3, encoded by a gene located upstream of kaiB3. At the N-terminus, KaiA3 is similar to response-regulator receiver domains, whereas its C-terminal domain resembles that of KaiA. Homology analysis shows that a KaiA3-KaiB3-KaiC3 system exists in several cyanobacteria and other bacteria. Using the Synechocystis sp. PCC 6803 homologs, we observe circadian oscillations in KaiC3 phosphorylation in vitro in the presence of KaiA3 and KaiB3. Mutations of kaiA3 affect KaiC3 phosphorylation, leading to growth defects under both mixotrophic and chemoheterotrophic conditions. KaiC1 and KaiC3 exhibit phase-locked free-running phosphorylation rhythms. Deletion of either system (∆kaiAB1C1 or ∆kaiA3B3C3) alters the period of the cellular backscattering rhythm. Furthermore, both oscillators are required to maintain high-amplitude, self-sustained backscatter oscillations with a period of approximately 24 h, indicating their interconnected nature. The cyanobacterial circadian clock typically includes a standard oscillator consisting of proteins KaiA, KaiB and KaiC, but some cyanobacteria have additional homologous proteins of unclear function. Here, the authors show that a KaiABC homolog system contributes, together with the canonical oscillator, to the control of circadian rhythms in the model cyanobacterium Synechocystis sp. PCC 6803. [ABSTRACT FROM AUTHOR]

Simple Summary: The circadian clock controls the rhythmic timing of nearly every aspect of physiology, including sleep, body temperature, hormone fluctuation, and overall metabolism on a daily basis. Research shows that disruption to this control contributes to the development of diseases, including cancer. Evidence also suggests that cancers may be amenable to treatments that target the circadian clock, which maximizes benefits while minimizing side effects. Here, the rhythmic influence over cancers of the liver and gut will be reviewed, and treatments that take into account the circadian clock will be discussed. Circadian rhythms dictate the timing of cellular and organismal physiology to maintain homeostasis. Within the liver and gut, circadian rhythms influence lipid and glucose homeostasis, xenobiotic metabolism, and nutrient absorption. Disruption of this orchestrated timing is known to negatively impact human health and contribute to disease progression, including carcinogenesis. Dysfunctional core clock timing has been identified in malignant growths and may be used as a molecular signature of disease progression. Likewise, the circadian clock and its downstream effectors also represent potential for novel therapeutic targets. Here, the role of circadian rhythms in the pathogenesis of cancers of the liver and gut will be reviewed, and chronotherapy and chronopharmacology will be explored as potential treatment options. [ABSTRACT FROM AUTHOR]

Background and Objectives: Circadian rhythms, the endogenous biological clocks that govern physiological processes, have emerged as pivotal regulators in the development and progression of breast cancer. This comprehensive review delves into the intricate interplay between circadian disruption and breast tumorigenesis from multifaceted perspectives, encompassing biological rhythms, circadian gene regulation, tumor microenvironment dynamics, and genetic polymorphisms. Methods and Results: Epidemiological evidence underscores the profound impact of external factors, such as night shift work, jet lag, dietary patterns, and exercise routines, on breast cancer risk and progression through the perturbation of circadian homeostasis. The review elucidates the distinct roles of key circadian genes, including CLOCK, BMAL1, PER, and CRY, in breast cancer biology, highlighting their therapeutic potential as molecular targets. Additionally, it investigates how circadian rhythm dysregulation shapes the tumor microenvironment, fostering epithelial-mesenchymal transition, chronic inflammation, and immunosuppression, thereby promoting tumor progression and metastasis. Furthermore, the review sheds light on the association between circadian gene polymorphisms and breast cancer susceptibility, paving the way for personalized risk assessment and tailored treatment strategies. Conclusions: Importantly, it explores innovative therapeutic modalities that harness circadian rhythms, including chronotherapy, melatonin administration, and traditional Chinese medicine interventions. Overall, this comprehensive review emphasizes the critical role of circadian rhythms in the pathogenesis of breast cancer and highlights the promising prospects for the development of circadian rhythm-based interventions to enhance treatment efficacy and improve patient outcomes. [ABSTRACT FROM AUTHOR]

Understanding the capacity for thermoregulation is critical for predicting organismal vulnerability to climate change, especially in lowland tropical rainforests, where warming conditions combine with high humidity and limited elevational or latitudinal refugia. Here, I focused on nine species of ground‐foraging insectivorous birds in the genus Myrmoderus, Myrmornis, Hylopezus, Myrmothera, Formicarius and Sclerurus – sensitive forest specialists characterized by recently documented population declines in both disturbed and undisturbed forests. Using high‐resolution data from loggers deployed on birds and their environment, I examined whether and how birds used thermoregulation and whether ambient water provided cooling opportunities. Variation in the rate of temperature change over the diel cycle suggested that all species employed behavioral and physiological thermoregulation, but some patterns differed by species' phylogenetic relatedness. All species warmed hours before their environment at sunrise, then experienced lower temperature increases at midday relative to the ambient thermal flux. These morning warming periods peaked around sunrise for all but Sclerurus rufigularis and constituted the diel temperature change maxima for five of the nine species. Six species exhibited pronounced oscillations in temperature change consistent with regular bathing around sunset, possibly for thermoregulatory or other purposes. This oscillation was the most prominent feature in the diel thermal flux for all three Sclerurus species and, to a lesser extent, for Myrmoderus ferrugineus, Myrmornis torquata and Myrmothera campanisona. Local rainfall reduced ambient temperatures, and birds experienced stronger cooling in the wet season and with higher rainfall intensity. However, rain‐induced cooling events were markedly absent in all three Sclerurus spp. These results highlight the fundamental role of water in avian thermoregulation and suggest that terrestrial insectivores attempt to maintain thermal homeostasis throughout the diel cycle. The observed thermoregulatory behaviors highlight a potentially critical aspect of their vulnerability – thermal regimes are profoundly altered by forest disturbance, climate change, and their combination. [ABSTRACT FROM AUTHOR]

Releasing farmed mallards into the wild is a common practice in wildlife management worldwide, involving millions of birds annually, and is mainly carried out to increase hunting opportunities. Ringing and previous research show that released mallards have low survival also outside the hunting season, and that survivors may compromise migration habits, morphology, and adaptations of the wild population. Detailed local movements of released mallards have not been studied before, despite the importance of spatiotemporal patterns for understanding the impact of releases and their utility for hunting. We studied local movements in August–October of 11 wild and 44 released mallards caught in the same wetland in southern Sweden and provided with GPS tags. Wild mallards moved longer distances than farmed, over the whole diel cycle, as well as during three out of four separate periods of the day (dawn, day, and dusk). Mallards of both origins moved the longest distances during dusk and dawn, and the shortest during the night. Males and females did not differ significantly in distance moved, regardless of origin (wild versus farmed). Our study demonstrates large differences in spatiotemporal movement patterns between wild and farmed mallards. The typical day of wild mallards included movements between wetlands in the landscape, likely to foraging sites known from previous experience. However, wild mallards frequently returned to the study wetland, probably attracted by supplementary bait. On the other hand, farmed mallards seldom left the study wetland, despite the possibility of accompanying wild birds to other sites. The sedentary behavior of farmed mallards and the fact that wild birds come to join them are both beneficial for hunting purposes. Limited movements of farmed mallards, together with their low survival, could also be positive as they limit hybridization between wild and farmed mallards, as well as dispersal of nutrients. [ABSTRACT FROM AUTHOR]

Skin health is impacted by a wide range of intrinsic and extrinsic factors (J Dermatol Sci, 2017, 85, 152), including those that impact circadian rhythm, such as sleep disruption (Textbook of Aging Skin, 2016), UV (Biomed Aging Pathol, 2013, 3, 161) and blue light (Int J Cosmet Sci, 2019, 41, 558). Disruption of the skin's endogenous circadian balance, even by a consistently late bedtime, has deleterious effects on multiple measurements of skin health, including hydration, skin barrier protection, microbiome counts and skin regeneration, among others (Clin Cosmet Investig Dermatol, 2022, 15, 1051). Skin repair processes occur at night and help to maintain important aspects of skin health (FEBS Lett, 2021, 595, 2413). Interest is increasing in the development of topical products that help restore proper circadian function. This study demonstrates that a proprietary topical formulation regulates new and established gene and protein biomarkers of circadian entrainment and circadian rhythm, demonstrating the product's potential to maintain appropriate dermal diurnal balance. [ABSTRACT FROM AUTHOR]

Organisms on Earth are known to evolve by cooperating with their neighbors in external environments. These cooperating organisms are under the influence of circadian rhythms derived from Earth's rotation and have various biological rhythms within them. However, little is known about the effects of these rhythms on the cooperation of organisms. In this study, we investigate the effects of the biological rhythms on the survival of cooperators in evolution using evolutionary game theory. We focused on the rhythm in reproduction among the various biological rhythms that organisms have. Our results are as follows. Rhythmic reproductions play a role in limiting the survival of cooperators; they reduce the survival limits of cooperators compared to when there is no rhythm. Their limiting force is sensitive to the number of interacting neighbors, however. When the number of interacting neighbors is relatively small, the effects of rhythm in reproduction on the survival limits of cooperators are not significant. As the number of interacting neighbors increases, the limiting force of rhythmic reproductions becomes more powerful, gradually decreasing the survival limits of cooperators. Variations of rhythm in reproduction do not alter the survival limits; they only cause fluctuations in the population of cooperators within the survival limits. Our findings suggest that the rhythmic reproductions in evolution determine the survival domain of cooperators, where the number of interacting neighbors is a major factor along with rhythmic reproductions. Organisms under the constant pressure imposed by rhythmic reproductions may need to find the optimal number of interacting neighbors to survive and evolve to a new level through cooperation. [ABSTRACT FROM AUTHOR]

Sleep disturbances have been shown to result in considerable morbidity and mortality. It is important for dental clinicians to understand the neuroscience behind sleep disorders. The authors conducted a search of the literature published from January 1990 through March 2024 of sleep medicine–related articles, with a focus on neuroscience. The authors prioritized articles about the science of sleep as related to dental medicine. The authors found a proliferation of articles related to sleep neuroscience along with its implications in dental medicine. The authors also found that the intricate neuroscientific principles of sleep medicine are being investigated robustly. The salient features of, and the differences between, central and obstructive sleep apneas have been elucidated. Sleep genes, such as CRY, PER1, PER2, and CLOCK, and their relationship to cancer and neurodegeneration are also additions to this rapidly developing science. The dental clinician has the potential to be the first to screen patients for possible sleep disorders and make prompt referrals to the appropriate medical professionals. This can be lifesaving as well as minimize potential future morbidity for the patient. [ABSTRACT FROM AUTHOR]

BACKGROUND: The widespread use of sodium propionate as a preservative in food may affect public health. We aimed to assess the effects of sodium propionate on circadian rhythms and pancreatic development in zebrafish and the possible underlying mechanisms. RESULTS: In this experiment, we analyzed the relationship between circadian rhythms and pancreatic development and then revealed the role of the thyroid endocrine system in zebrafish. The results showed that sodium propionate interfered with the rhythmic behavior of zebrafish, and altered the expression of important rhythmic genes. Experimental data revealed that pancreatic morphology and developmental genes were altered after sodium propionate exposure. Additionally, thyroid hormone levels and key gene expression associated with the hypothalamic–pituitary–thyroid axis were significantly altered. Melatonin at a concentration of 1 μmol L−1, with a mild effect on zebrafish, observably alleviated sodium propionate‐induced disturbances in circadian rhythms and pancreatic development, as well as regulating the thyroid system. CONCLUSION: Melatonin, while modulating the thyroid system, significantly alleviates sodium propionate‐induced circadian rhythm disturbances and pancreatic developmental disorders. We further revealed the deleterious effects of sodium propionate as well as the potential therapeutic effects of melatonin on circadian rhythm, pancreatic development and the thyroid system. © 2024 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Habitual short sleep durations are associated with several cardiovascular diseases. Experimental research generally supports these findings as metrics of arterial function are impaired after complete deprivation of sleep and after longer periods of partial sleep restriction. The acute influence of a single instance of partial sleep restriction (PSR), however, has not been defined. We evaluated arterial structure and function among 32 university‐aged participants on two occasions: once after normal habitual sleep (NS), and again the morning after an acute partial sleep restriction (PSR) intervention involving only 3 h of sleep for a single night. Endothelial function was measured using ultrasonography at the brachial artery via flow‐mediated dilatation (FMD), and a ramp peak oxygen uptake test was used to evaluate cardiorespiratory fitness. Blood samples were collected from a subset of participants to investigate the influence of circulatory factors on cellular mechanisms implicated in endothelial function. Sleep duration was lower after a night of PSR compared to NS (P < 0.001); however, there were no appreciable differences in any haemodynamic outcome between conditions. FMD was not different between NS and PSR (NS: 6.5 ± 2.9%; PSR: 6.3 ± 2.9%; P = 0.668), and cardiorespiratory fitness did not moderate the haemodynamic response to PSR (all P > 0.05). Ex vivo cell culture results aligned with in vivo data, showing that acute PSR does not alter intracellular processes involved in endothelial function. No differences in arterial structure or function were observed between NS and acute PSR in healthy and young participants, and cardiorespiratory fitness does not modulate the arterial response to acute sleep restriction. What is the central question of the study?Does a single night of restricted sleep alter indices of arterial structure and function? and if so what is the extent to which cardiorespiratory fitness might modulate the relationship between acute sleep perturbation and vascular function in humans?What is the main finding and its importance?One night of partial sleep restriction does not affect arterial function or structure in young and healthy humans, and arterial function may be sensitive to prolonged, but not necessarily acute, reductions in sleep durations. [ABSTRACT FROM AUTHOR]

Shift work disrupts circadian rhythms and alters sleep patterns, resulting in various health problems. To quantitatively assess the impact of shift work on brain health, we evaluated the brain age index (BAI) derived from sleep electroencephalography (EEG) results in night-shift workers and compared it with that in daytime workers. We studied 45 female night shift nurses (mean age: 28.2 ± 3.3 years) and 44 female daytime workers (30.5 ± 4.7 years). Sleep EEG data were analyzed to calculate BAI. The BAI of night shift workers who were asleep during the daytime with those of daytime workers who were asleep at night were statistically compared to explore associations between BAI, duration of shift work, and sleep quality. Night-shift workers exhibited significantly higher BAI (2.14 ± 6.04 vs. 0 ± 5.35), suggesting accelerated brain aging and altered sleep architecture, including reduced delta and sigma wave frequency activity during non-rapid eye movement sleep than daytime workers. Furthermore, poor deep sleep quality, indicated by a higher percentage of N1, lower percentage of N3, and higher arousal index, was associated with increased BAI among shift workers. Additionally, a longer duration of night-shift work was correlated with increased BAI, particularly in older shift workers. Night-shift work, especially over extended periods, may be associated with accelerated brain aging, as indicated by higher BAI and alterations in sleep architecture. Interventions are necessary to mitigate the health impacts of shift work. Further research on the long-term effects and potential strategies for sleep improvement and mitigating brain aging in shift workers is warranted. • Night-shift workers exhibited a significantly higher Brain Age Index (BAI) compared to daytime workers. • Poor deep sleep quality during daytime sleep in night-shift workers was associated with increased BAI. • Extended periods of night-shift work were associated with accelerated brain aging. [ABSTRACT FROM AUTHOR]

This study aimed to evaluate the impact of time-restricted eating (TRE) on neuro-physiological parameters, objective and subjective sleep, pulmonary capacity, and postural balance among women with excess body weight. Methods: Thirty-one participants were assigned to either a TRE group (n = 15, 28.74 ± 9.25 years, 88.32 ± 13.38 kg, and 32.71 ± 5.15 kg/m2), engaging in ad libitum 16 h fasting over a 12-week period, or a control group (CG, n = 16, 36.25 ± 11.52 years, 90.88 ± 19.01 kg, and 33.66 ± 6.18 kg/m2). The assessment of heart rate variability (HRV), spirometric parameters (forced vital capacity (FVC), forced expiratory volume in the first second (FEV1), FEV1/ FVC ratio, objective and subjective sleep assessments employing actigraphy and the Epworth Sleepiness Scale, and postural balance using the Y balance test (YBT) were conducted before and after the intervention. Results: No significant negative effects of TRE were observed for HRV and objective sleep parameters. Only the TRE group improved FEV1 in both sitting (p < 0.0005) and supine positions (p = 0.001). Furthermore, the TRE group showed improvement in postural balance performance compared to the CG in anterior (p = 0.03), postero-medial (p = 0.04), and postero-lateral directions (p = 0.003). Conclusion: This study highlights TRE as a feasible and safe dietary intervention with significant improvements in postural balance and pulmonary function, without any negative impact on HRV or objective sleep assessments among overweight or obese women. [ABSTRACT FROM AUTHOR]

Key Points: Question: What is the overlap between accelerometry-assessed sleep, physical activity, and circadian rhythms, and do they distinguish state and trait in major depressive disorder (MDD)? Findings: This cross-sectional study of 2317 adults used a multimodal data-reduction technique and found that joint components outweighed individual variation in the 3 domains. MDD was characterized by reduced and more fragmented physical activity, lower amplitude of circadian rhythm, and later timing of both sleep and the peak of physical activity. Meaning: These findings highlight the importance of characterizing 24-hour rhythms with accelerometry for future research and to define targets for interventions for MDD. This cross-sectional study examines joint and individual components of the accelerometry-derived domains of sleep, physical activity, and circadian rhythms and assesses associations with major depressive disorder (MDD) among adults from Lausanne, Switzerland. Importance: Accelerometry has been increasingly used as an objective index of sleep, physical activity, and circadian rhythms in people with mood disorders. However, most prior research has focused on sleep or physical activity alone without consideration of the strong within- and cross-domain intercorrelations; and few studies have distinguished between trait and state profiles of accelerometry domains in major depressive disorder (MDD). Objectives: To identify joint and individual components of the domains derived from accelerometry, including sleep, physical activity, and circadian rhythmicity using the Joint and Individual Variation Explained method (JIVE), a novel multimodal integrative dimension-reduction technique; and to examine associations between joint and individual components with current and remitted MDD. Design, Setting, and Participants: This cross-sectional study examined data from the second wave of a population cohort study from Lausanne, Switzerland. Participants included 2317 adults (1164 without MDD, 185 with current MDD, and 968 with remitted MDD) with accelerometry for at least 7 days. Statistical analysis was conducted from January 2021 to June 2023. Main Outcomes and Measures: Features derived from accelerometry for 14 days; current and remitted MDD. Logistic regression adjusted for age, sex, body mass index, and anxiety and substance use disorders. Results: Among 2317 adults included in the study, 1261 (54.42%) were female, and mean (SD) age was 61.79 (9.97) years. JIVE reduced 28 accelerometry features to 3 joint and 6 individual components (1 sleep, 2 physical activity, 3 circadian rhythms). Joint components explained 58.5%, 79.5%, 54.5% of the total variation in sleep, physical activity, and circadian rhythm domains, respectively. Both current and remitted depression were associated with the first 2 joint components that were distinguished by the salience of high-intensity physical activity and amplitude of circadian rhythm and timing of both sleep and physical activity, respectively. MDD had significantly weaker circadian rhythmicity. Conclusions and Relevance: Application of a novel multimodal dimension-reduction technique demonstrates the importance of joint influences of physical activity, circadian rhythms, and timing of both sleep and physical activity with MDD; dampened circadian rhythmicity may constitute a trait marker for MDD. This work illustrates the value of accelerometry as a potential biomarker for subtypes of depression and highlights the importance of consideration of the full 24-hour sleep-wake cycle in future studies. [ABSTRACT FROM AUTHOR]

Background: Prior work documented circadian rhythm impacts on efficacy and toxicity of cancer therapies. Methods: Secondary analysis of prospective, phase II trial of metastatic HNSCC randomized to nivolumab+/−SBRT. Used cutoffs of 1100 and 1630. Timing classified by first infusion or majority of SBRT (e.g., PM SBRT defined by two or three fractions after 1630). Results: Of 62 patients, there was no significant difference in median PFS between AM nivolumab (n = 7, 175 days), PM nivolumab (n = 21, 58 days), or Mid‐Day nivolumab (n = 34, 67 days; p = 0.8). There was no significant difference in median PFS with AM SBRT (n = 4, 78 days), PM SBRT (n = 13, 111 days), or Mid‐Day SBRT (n = 15, 63 days; p = 0.8). There was no significant difference in Grade 3–4 toxicity or ORR. Sensitivity analyses with other timepoints were negative. Conclusions: Further work may elucidate circadian impacts on select patients, tumors, and therapies; however, we found no significant effect in this study. [ABSTRACT FROM AUTHOR]

Light/dark (LD) cycles are responsible for oscillations in gene expression, which modulate several aspects of plant physiology. Those oscillations can persist under constant conditions due to regulation by the circadian oscillator. The response of the transcriptome to light regimes is dynamic and allows plants to adapt rapidly to changing environmental conditions. We compared the transcriptome of Arabidopsis under LD and constant light (LL) for 3 days and identified different gene co‐expression networks in the two light regimes. Our studies yielded unforeseen insights into circadian regulation. Intuitively, we anticipated that gene clusters regulated by the circadian oscillator would display oscillations under LD cycles. However, we found transcripts encoding components of the flavonoid metabolism pathway that were rhythmic in LL but not in LD. We also discovered that the expressions of many stress‐related genes were significantly increased during the dark period in LD relative to the subjective night in LL, whereas the expression of these genes in the light period was similar. The nocturnal pattern of these stress‐related gene expressions suggested a form of "skotoprotection." The transcriptomics data were made available in a web application named Cyclath, which we believe will be a useful tool to contribute to a better understanding of the impact of light regimes on plants. [ABSTRACT FROM AUTHOR]

Exposure to infectious or non‐infectious immune activation during early development is a serious risk factor for long‐term behavioural dysfunctions. Mouse models of maternal immune activation (MIA) have increasingly been used to address neuronal and behavioural dysfunctions in response to prenatal infections. One commonly employed MIA model involves administering poly(I:C) (polyriboinosinic‐polyribocytdilic acid), a synthetic analogue of double‐stranded RNA, during gestation, which robustly induces an acute viral‐like inflammatory response. Using electroencephalography (EEG) and infrared (IR) activity recordings, we explored alterations in sleep/wake, circadian and locomotor activity patterns on the adult male offspring of poly(I:C)‐treated mothers. Our findings demonstrate that these offspring displayed reduced home cage activity during the (subjective) night under both light/dark or constant darkness conditions. In line with this finding, these mice exhibited an increase in non‐rapid eye movement (NREM) sleep duration as well as an increase in sleep spindles density. Following sleep deprivation, poly(I:C)‐exposed offspring extended NREM sleep duration and prolonged NREM sleep bouts during the dark phase as compared with non‐exposed mice. Additionally, these mice exhibited a significant alteration in NREM sleep EEG spectral power under heightened sleep pressure. Together, our study highlights the lasting effects of infection and/or immune activation during pregnancy on circadian activity and sleep/wake patterns in the offspring. [ABSTRACT FROM AUTHOR]

Rivers efficiently collect, process, and transport terrestrial‐derived carbon. River ecosystem metabolism is the primary mechanism for processing carbon. Diel cycles of dissolved oxygen (DO) have been used for decades to infer river ecosystem metabolic rates, which are routinely used to predict metabolism of carbon dioxide (CO2) with uncertainties of the assumed stoichiometry ranging by a factor of 4. Dissolved inorganic carbon (DIC) has been less used to directly infer metabolism because it is more difficult to quantify, involves the complexity of inorganic carbon speciation, and as shown in this study, likely requires a two‐station approach. Here, we developed DIC metabolism models using single‐ and two‐station approaches. We compared metabolism estimates based on simultaneous DO and DIC monitoring in the Upper Clark Fork River (USA), which also allowed us to estimate ecosystem‐level photosynthetic and respiratory quotients (PQE and RQE). We observed that metabolism estimates from DIC varied more between single‐ and two‐station approaches than estimates from DO. Due to carbonate buffering, CO2 is slower to equilibrate with the atmosphere compared to DO, likely incorporating a longer distance of upstream heterogeneity. Reach‐averaged PQE ranged from 1.5 to 2.0, while RQE ranged from 0.8 to 1.5. Gross primary production from DO was larger than that from DIC, as was net ecosystem production by 100mmolm−2d−1$$ 100\kern0.5em \mathrm{mmol}\kern0.5em {\mathrm{m}}^{-2}\kern0.5em {\mathrm{d}}^{-1} $$. The river was autotrophic based on DO but heterotrophic based on DIC, complicating our understanding of how metabolism regulated CO2 production. We suggest future studies simultaneously model metabolism from DO and DIC to understand carbon processing in rivers. [ABSTRACT FROM AUTHOR]

Plants sense and respond to environmental cues during 24 h fluctuations in their environment. This requires the integration of internal cues such as circadian timing with environmental cues such as light and temperature to elicit cellular responses through signal transduction. However, the integration and transduction of circadian and environmental signals by plants growing in natural environments remains poorly understood. To gain insights into 24 h dynamics of environmental signaling in nature, we performed a field study of signal transduction from the nucleus to chloroplasts in a natural population of Arabidopsis halleri. Using several modeling approaches to interpret the data, we identified that the circadian clock and temperature are key regulators of this pathway under natural conditions. We identified potential time-delay steps between pathway components, and diel fluctuations in the response of the pathway to temperature cues that are reminiscent of the process of circadian gating. We found that our modeling framework can be extended to other signaling pathways that undergo diel oscillations and respond to environmental cues. This approach of combining studies of gene expression in the field with modeling allowed us to identify the dynamic integration and transduction of environmental cues, in plant cells, under naturally fluctuating diel cycles. [ABSTRACT FROM AUTHOR]

Background: Light exposure significantly impacts human health, regulating our circadian clock, sleep–wake cycle and other physiological processes. With the emergence of wearable light loggers and dosimeters, research on real-world light exposure effects is growing. There is a critical need to standardize data collection and documentation across studies. Results: This article proposes a new metadata descriptor designed to capture crucial information within personalized light exposure datasets collected with wearable light loggers and dosimeters. The descriptor, developed collaboratively by international experts, has a modular structure for future expansion and customization. It covers four key domains: study design, participant characteristics, dataset details, and device specifications. Each domain includes specific metadata fields for comprehensive documentation. The user-friendly descriptor is available in JSON format. A web interface simplifies generating compliant JSON files for broad accessibility. Version control allows for future improvements. Conclusions: Our metadata descriptor empowers researchers to enhance the quality and value of their light dosimetry datasets by making them FAIR (findable, accessible, interoperable and reusable). Ultimately, its adoption will advance our understanding of how light exposure affects human physiology and behaviour in real-world settings. [ABSTRACT FROM AUTHOR]

Temporal ecological niche partitioning is an underappreciated driver of speciation. While insects have long been models for circadian biology, the genes and circuits that allow adaptive changes in diel-niches remain poorly understood. We compared gene expression in closely related day- and night-active non-model wild silk moths, with otherwise similar ecologies. Using an ortholog-based pipeline to compare RNA-Seq patterns across two moth species, we find over 25 pairs of gene orthologs showing differential expression. Notably, the gene disco, involved in circadian control, optic lobe and clock neuron development in Drosophila, shows robust adult circadian mRNA cycling in moth heads. Disco is highly conserved in moths and has additional zinc-finger domains with specific nocturnal and diurnal mutations. We propose disco as a candidate gene for the diversification of temporal diel-niche in moths. [ABSTRACT FROM AUTHOR]

While it is generally known that metabolic disorders and circadian dysfunction are intertwined, how the two systems affect each other is not well understood, nor are the genetic factors that might exacerbate this pathological interaction. Blood chemistry is profoundly changed in metabolic disorders, and we have previously shown that serum factors change cellular clock properties. To investigate if circulating factors altered in metabolic disorders have circadian modifying effects, and whether these effects are of genetic origin, we measured circadian rhythms in U2OS cell in the presence of serum collected from diabetic, obese or control subjects. We observed that circadian period lengthening in U2OS cells was associated with serum chemistry that is characteristic of insulin resistance. Characterizing the genetic variants that altered circadian period length by genome‐wide association analysis, we found that one of the top variants mapped to the E3 ubiquitin ligase MARCH1 involved in insulin sensitivity. Confirming our data, the serum circadian modifying variants were also enriched in type 2 diabetes and chronotype variants identified in the UK Biobank cohort. Finally, to identify serum factors that might be involved in period lengthening, we performed detailed metabolomics and found that the circadian modifying variants are particularly associated with branched chain amino acids, whose levels are known to correlate with diabetes and insulin resistance. Overall, our multi‐omics data showed comprehensively that systemic factors serve as a path through which metabolic disorders influence circadian system, and these can be examined in human populations directly by simple cellular assays in common cultured cells. [ABSTRACT FROM AUTHOR]

Exposure to bright light can be visually aversive. This study explored the association between light aversion and various facets of impulsivity. A total of 1,245 participants completed the UPPS-Impulsive Behavior Scale to assess five facets of impulsivity. Additionally, participants responded to questions regarding their aversion to light (e.g., how aversive do you find bright light?). Spearman's correlation coefficients (rho) revealed that individuals who find light physically aversive, or who experience a negative physical response to exposure (e.g., nausea or headache) triggered by bright indoor light or sunlight, tend to act impulsively under extreme negative and positive affect. Individuals who experience a negative physical response to exposure display greater premeditation, indicating a higher likelihood of considering the potential consequences of their actions. Moreover, these individuals score lower on sensation-seeking, suggesting a reduced inclination to seek out thrilling or novel experiences. These results reveal a complex relationship between light aversion and impulsivity, where those who find light aversive tend to be less impulsive in general, but more impulsive under extreme positive or negative affect. [ABSTRACT FROM AUTHOR]

Summary Arabidopsis PSEUDORESPONSE REGULATOR7 (PRR7) is a core component of the circadian oscillator which also plays a crucial role in freezing tolerance. PRR7 undergoes proteasome‐dependent degradation to discretely phase maximal expression in early evening. While its repressive activity on downstream genes is integral to cold regulation, the mechanism of the conditional regulation of the PRR7 abundance is unknown. We used mutant analysis, protein interaction and ubiquitylation assays to establish that the ubiquitin ligase adaptor, HIGH EXPRESSION OF OSMOTICALLY RESPONSIVE GENE 15 (HOS15), controls the protein accumulation pattern of PRR7 through direct protein–protein interactions at low temperatures. Freezing tolerance and electrolyte leakage assays show that PRR7 enhances cold temperature sensitivity, supported by ChIP‐qPCR at C‐REPEAT BINDING FACTOR1 (CBF1) and COLD‐REGULATED 15A (COR15A) promoters where PRR7 levels were higher in hos15 mutants. HOS15 mediates PRR7 turnover through enhanced ubiquitylation at low temperature in the dark. Under the same conditions, increased PRR7 association with the promoters of CBFs and COR15A in hos15 correlates with decreased CBF1 and COR15A transcription and enhanced freezing sensitivity. We propose a novel mechanism whereby HOS15‐mediated degradation of PRR7 provides an intersection between the circadian system and other cold acclimation pathways that lead to increased freezing tolerance. [ABSTRACT FROM AUTHOR]

Most mammalian cells have molecular circadian clocks that generate widespread rhythms in transcript and protein abundance. While circadian clocks are robust to fluctuations in the cellular environment, little is known about the mechanisms by which the circadian period compensates for fluctuating metabolic states. Here, we exploit the heterogeneity of single cells both in circadian period and a metabolic parameter--protein stability--to study their interdependence without the need for genetic manipulation. We generated cells expressing key circadian proteins (CRYPTOCHROME1/2 (CRY1/2) and PERIOD1/2 (PER1/2)) as endogenous fusions with fluorescent proteins and simultaneously monitored circadian rhythms and degradation in thousands of single cells. We found that the circadian period compensates for fluctuations in the turnover rates of circadian repressor proteins and uncovered possible mechanisms using a mathematical model. In addition, the stabilities of the repressor proteins are circadian phase dependent and correlate with the circadian period in a phase-dependent manner, in contrast to the prevailing model. [ABSTRACT FROM AUTHOR]

Summary In bipolar disorders, abnormalities of sleep patterns and of circadian rhythms of activity are observed during mood episodes, but also persist during euthymia. Shared vulnerabilities between mood disorders and abnormalities of sleep patterns and circadian rhythms of activity have been suggested. This exploratory study investigated the association between polygenic risk scores for bipolar disorder and major depressive disorder, actigraphy estimates of sleep patterns, and circadian rhythms of activity in a sample of 62 euthymic individuals with bipolar disorder. The polygenic risk score – bipolar disorder and polygenic risk score – major depressive disorder were calculated for three stringent thresholds of significance. Data reduction was applied to aggregate actigraphy measures into dimensions using principal component analysis. A higher polygenic risk score – major depressive disorder was associated with more fragmented sleep, while a higher polygenic risk score – bipolar disorder was associated with a later peak of circadian rhythms of activity. These results remained significant after adjustment for age, sex, bipolar disorder subtype, body mass index, current depressive symptoms, current tobacco use, and medications prescribed at inclusion, but not after correction for multiple testing. In conclusion, the genetic vulnerabilities to major depression and to bipolar disorder might be associated with different abnormalities of sleep patterns and circadian rhythms of activity. The results should be replicated in larger and independent samples. [ABSTRACT FROM AUTHOR]

AbstractPurposePatients and methodsResultsConclusionThis aim of this study was to assess the possible association between diurnal oscillations and biochemical markers associated with calcium homeostasis. This included the markers parathyroid hormone (PTH), total calcium, total alkaline phosphatase, phosphate, and 25-hydroxyvitamin D (25-OH-D). By examining the influence of circadian rhythms on these parameters, the study aimed to deepen the understanding of calcium metabolism dynamics and its clinical implications.Blood samples from 24 Caucasian male volunteers aged 20 to 40 (mean age 26) with normal pulse, blood pressure, and BMI were analyzed for biochemical markers related to calcium homeostasis. Data was obtained from the Bispebjerg study of diurnal variations. Blood samples were collected every three hours over a 24-hour period. Patients were fasting from 22:00 to 09:00. The participants spent 24 h in the hospital ward, receiving regular meals and engaging in low-intensity activities. They experienced 15 h of daylight and 9 h of complete darkness during sleep. Diurnal oscillations were analyzed using cosinor analysis with statistical significance set at p < 0.05.Total calcium, phosphate, and PTH exhibited significant diurnal variations. Total calcium and PTH were inversely synchronized while PTH and phosphate oscillated in synchronization. The three parameters showed relatively large amplitude/reference range ratios from 25.4% to 41.5%.This study found notable fluctuations in total calcium, phosphate, and PTH levels over a 24-hour cycle, while 25-OH-D and total alkaline phosphatase remained consistent. It highlights the importance of considering sampling times for total calcium, PTH, and phosphate in clinical settings. [ABSTRACT FROM AUTHOR]

Introduction: Maintaining metabolic balance relies on accumulating nutrients during feeding periods and their subsequent release during fasting. In obesity and metabolic disorders, strategies aimed at reducing food intake while simulating fasting have garnered significant attention for weight loss. Caloric restriction (CR) diets and intermittent fasting (IF) interventions have emerged as effective approaches to improving cardiometabolic health. Although the comparative metabolic benefits of CR versus IF remain inconclusive, this review focuses on various forms of IF, particularly time-restricted eating (TRE). Methods: This study employs a narrative review methodology, systematically collecting, synthesizing, and interpreting the existing literature on TRE and its metabolic effects. A comprehensive and unbiased search of relevant databases was conducted to identify pertinent studies, including pre-clinical animal studies and clinical trials in humans. Keywords such as "Obesity," "Intermittent Fasting," "Time-restricted eating," "Chronotype," and "Circadian rhythms" guided the search. The selected studies were critically appraised based on predefined inclusion and exclusion criteria, allowing for a thorough exploration and synthesis of current knowledge. Results: This article synthesizes pre-clinical and clinical studies on TRE and its metabolic effects, providing a comprehensive overview of the current knowledge and identifying gaps for future research. It explores the metabolic outcomes of recent clinical trials employing different TRE protocols in individuals with overweight, obesity, or type II diabetes, emphasizing the significance of individual chronotype, which is often overlooked in practice. In contrast to human studies, animal models underscore the role of the circadian clock in mitigating metabolic disturbances induced by obesity through time-restricted feeding (TRF) interventions. Consequently, we examine pre-clinical evidence supporting the interplay between the circadian clock and TRF interventions. Additionally, we provide insights into the role of the microbiota, which TRE can modulate and its influence on circadian rhythms. [ABSTRACT FROM AUTHOR]

Introduction: Chronotype refers to individual preference in circadian cycles and is associated with psychiatric problems. It is mainly classified into early (those who prefer to be active in the morning and sleep and wake up early) and late (those who prefer to be active in the evening and sleep and wake up late) chronotypes. Although previous research has demonstrated associations between chronotype and cognitive function and brain structure in adults, little is known regarding these associations in children. Here, we aimed to investigate the relationship between chronotype and cognitive function in children. Moreover, based on the significant association between chronotype and specific cognitive functions, we extracted regions-of-interest (ROI) and examined the association between chronotype and ROI volumes. Methods: Data from 4,493 children (mean age of 143.06 months) from the Adolescent Brain Cognitive Development Study were obtained, wherein chronotype (mid-sleep time on free days corrected for sleep debt on school days) was assessed by the Munich Chronotype Questionnaire. Subsequently, the associations between chronotype, cognitive function, and ROI volumes were evaluated using linear mixed-effects models. Results: Behaviorally, chronotype was negatively associated with vocabulary knowledge, reading skills, and episodic memory performance. Based on these associations, the ROI analysis focused on language-related and episodic memory- related areas revealed a negative association between chronotype and left precentral gyrus and right posterior cingulate cortex volumes. Furthermore, the precentral gyrus volume was positively associated with vocabulary knowledge and reading skills, while the posterior cingulate cortex volume was positively associated with episodic memory performance. Discussion: These results suggest that children with late chronotype have lower language comprehension and episodic memory and smaller brain volumes in the left precentral gyrus and right posterior cingulate cortex associated with these cognitive functions. [ABSTRACT FROM AUTHOR]

Circadian fluctuations in physiological setpoints are determined by the suprachiasmatic nucleus (SCN) which exerts control over many target structures within and beyond the hypothalamus via projections. The SCN, or central pacemaker, orchestrates synchrony between the external environment and the internal circadian mechanism. The resulting cycles in hormone levels and autonomic nervous system (ANS) activity provide precise messages to specific organs, adjusting, for example, their sensitivity to approaching hormones or metabolites. The SCN responds to both photic (light) and non-photic input. Circadian patterns are found in both heart rate and blood pressure, which are linked to daily variations in activity and autonomic nervous system activity. Variations in blood pressure are of great interest as several cardiovascular diseases such as stroke, arrhythmias, and hypertension are linked to circadian rhythm dysregulation. The disruption of normal day-night cycles, such as in shift work, social jetlag, or eating outside of normal hours leads to desynchronization of the central and peripheral clocks. This desynchronization leads to disorganization of the cellular processes that are normally driven by the interactions of the SCN and photic input. Here, we review autonomic system function and dysfunction due to regulation and interaction between different cardiorespiratory brain centers and the SCN, as well as social, lifestyle, and external factors that may impact the circadian control of blood pressure. [ABSTRACT FROM AUTHOR]

Caffeine consumption is associated with the evening chronotype, and caffeine administration in mice results in prolonged period of the circadian rhythm in locomotor activity. However, as caffeine is bitter, sweetened caffeine is preferred by humans and mice; yet, its impact on the circadian clock has not been explored. In this study, mice were provided with freely available sweetened caffeine to investigate its effects on behavioral rhythms and peripheral clocks. Mice that freely consumed sweetened caffeine shifted from nocturnal to diurnal activity rhythms. In addition to the light-dark entrained behavioral rhythm component, some animals exhibited free-running period longer than 24-h. Intraperitoneal administration of caffeine at the beginning of the light phase also acutely induced diurnal behavior. The behavioral rhythms with long period (26–30 h) due to sweetened caffeine were observed even in mice housed under constant light or with a lesioned central circadian clock located in the suprachiasmatic nucleus of the hypothalamus; however, the rhythmicity was unstable. PER2::LUCIFERASE rhythms in peripheral tissues, such as the kidney, as measured via in vivo whole-body imaging during caffeine consumption, showed reduced amplitude and desynchronized phases among individuals. These results indicate that consumption of sweetened caffeine induces diurnal and long-period behavioral rhythms irrespective of the central clock, causing desynchronization of the clock in the body. [ABSTRACT FROM AUTHOR]