Sex Differences in Circadian Rhythms

Exposure to real-ambient bedroom light at night delayed circadian rhythm in healthy Chinese young adults: A cross-sectional study

BACKGROUND

Light at night (LAN) have attracted increased research attention on account of its widespread health hazards. However, the underlying mechanism remains unknown. The objective of this study was to investigate the effects of real-ambient bedroom LAN exposure on circadian rhythm among young adults and potential sex differences.

METHODS

Bedroom LAN exposure was measured at 60-s intervals for 2 consecutive days using a portable illuminance meter. Circadian phase was determined by the dim light melatonin onset (DLMO) time in 7 time-series saliva samples.

RESULTS

The mean age of the 142 participants was 20.7 ± 0.8 years, and 59.9% were women. The average DLMO time was 21:00 ± 1:11 h, with men (21:19 ± 1:12 h) later than women (20:48 ± 1:07 h). Higher level of LAN intensity (LANavg ≥ 3lx vs. LANavg < 3lx) was associated with an 81.0-min later in DLMO time (95% CI: 0.99, 1.72), and longer duration of nighttime light intensity ≥ 5lx (LAN5; LAN5 ≥ 45 min vs. LAN5 < 45 min) was associated with a 51.6-min later in DLMO time (95% CI: 0.46, 1.26). In addition, the delayed effect of LAN exposure on circadian phase was more pronounced in men than in women (all P-values <0.05).

CONCLUSIONS

Overall, bedroom LAN exposure was significantly associated with delayed circadian rhythm. Additionally, the delayed effect is more significant in men. Keeping bedroom dark at night may be a practicable option to prevent circadian disruption and associated health implications. Future studies with more advanced light measurement instrument and consensus methodology for DLMO assessment are warranted.

Long-lasting effects of disturbing the circadian rhythm or sleep in adolescence

Circadian rhythms are endogenous, near 24-hour rhythms that regulate a multitude of biological and behavioral processes across the diurnal cycle in most organisms. Over the lifespan, a bell curve pattern emerges in circadian phase preference (i.e. chronotype), with children and adults generally preferring to wake earlier and fall asleep earlier, and adolescents and young adults preferring to wake later and fall asleep later than their adult counterparts. This well-defined shift speaks to the variability of circadian rhythmicity over the lifespan and the changing needs and demands of the brain as an organism develops, particularly in the adolescent period. Indeed, adolescence is known to be a critical period of development during which dramatic neuroanatomical changes are occurring to allow for improved decision-making. Due to the large amount of re-structuring occurring in the adolescent brain, circadian disruptions during this period could have adverse consequences that persist across the lifespan. While the detrimental effects of circadian disruptions in adults have been characterized in depth, few studies have longitudinally assessed the potential long-term impacts of circadian disruptions during adolescence. Here, we will review the evidence that disruptions in circadian rhythmicity during adolescence have effects that persist into adulthood. As biological and social time often conflict in modern society, with school start times misaligned with adolescents' endogenous rhythms, it is critical to understand the long-term impacts of disrupted circadian rhythmicity in adolescence.

Female mice display sex-specific differences in cerebrovascular function and subarachnoid haemorrhage-induced injury

BACKGROUND

In male mice, a circadian rhythm in myogenic reactivity influences the extent of brain injury following subarachnoid haemorrhage (SAH). We hypothesized that female mice have a different cerebrovascular phenotype and consequently, a distinct SAH-induced injury phenotype.

METHODS

SAH was modelled by pre-chiasmatic blood injection. Olfactory cerebral resistance arteries were functionally assessed by pressure myography; these functional assessments were related to brain histology and neurobehavioral assessments. Cystic fibrosis transmembrane conductance regulator (CFTR) expression was assessed by PCR and Western blot. We compared non-ovariectomized and ovariectomized mice.

FINDINGS

Cerebrovascular myogenic reactivity is not rhythmic in females and no diurnal differences in SAH-induced injury are observed; ovariectomy does not unmask a rhythmic phenotype for any endpoint. CFTR expression is rhythmic, with similar expression levels compared to male mice. CFTR inhibition studies, however, indicate that CFTR activity is lower in female arteries. Pharmacologically increasing CFTR expression in vivo (3 mg/kg lumacaftor for 2 days) reduces myogenic tone at Zeitgeber time 11, but not Zeitgeber time 23. Myogenic tone is not markedly augmented following SAH in female mice and lumacaftor loses its ability to reduce myogenic tone; nevertheless, lumacaftor confers at least some injury benefit in females with SAH.

INTERPRETATION

Female mice possess a distinct cerebrovascular phenotype compared to males, putatively due to functional differences in CFTR regulation. This sex difference eliminates the CFTR-dependent cerebrovascular effects of SAH and may alter the therapeutic efficacy of lumacaftor compared to males.

FUNDING

Brain Aneurysm Foundation, Heart and Stroke Foundation and Ted Rogers Centre for Heart Research.

Recent advances in understanding the kidney circadian clock mechanism

Circadian rhythms are endogenous biological oscillations that regulate various physiological processes in organisms, including kidney function. The kidney plays a vital role in maintaining homeostasis by regulating water and electrolyte balance, blood pressure, and excretion of metabolic waste products, all of which display circadian rhythmicity. For this reason, studying the circadian regulation of the kidney is important, and the time of day is a biological and experimental variable that must be considered. Over the past decade, considerable progress has been made in understanding the molecular mechanisms underlying circadian regulation within the kidney. In this review, the current knowledge regarding circadian rhythms in the kidney is explored, focusing on the molecular clock machinery, circadian control of renal functions, and the impact of disrupted circadian rhythms on kidney health. In addition, parameters that should be considered and future directions are outlined in this review.

High-throughput phenotyping to characterise range use behaviour in broiler chickens

A key characteristic of free-range chicken farming is to enable chickens to spend time outdoors. However, each chicken may use the available areas for roaming in variable ways. To check if, and how, broilers use their outdoor range at an individual level, we need to reliably characterise range use behaviour. Traditional methods relying on visual scans require significant time investment and only provide discontinuous information. Passive RFID (Radio Frequency Identification) systems enable tracking individually tagged chickens' when they go through pop-holes; hence, they only provide partial information on the movements of individual chickens. Here, we describe a new method to measure chickens' range use and test its reliability on three ranges each containing a different breed. We used an active RFID system to localise chickens in their barn, or in one of nine zones of their range, every 30 seconds and assessed range-use behaviour in 600 chickens belonging to three breeds of slow- or medium-growing broilers used for outdoor production (all <40 g daily weight gain). From those real-time locations, we determined five measures to describe daily range use: time spent in the barn, number of outdoor accesses, number of zones visited in a day, gregariousness (an index that increases when birds spend time in zones where other birds are), and numbers of zone changes. Principal Component Analyses (PCAs) were performed on those measures, in each production system, to create two synthetic indicators of chickens' range use behaviour. The first two PCA axes represented over 90% of the variance of the five measures and were both consistent over time and correlated with independent visual scans. Contributions of the five measures to the PCAs were similar among breeds, except for the correlation between the number of outdoor accesses and the four other measures. PC1 correlated with time spent inside the barn and zone changes frequency, whilst PC2 was explained by exploration of the range. Taken together, PC1 and PC2 indicators showed that range use increased with age, outdoor temperature (in spring), and did not differ between males and females. Importantly, daily scores for both indicators were repeatable among individuals - particularly in PC1 - showing inter-individual variability on range-use. The characterisation of broiler behaviour around their range with these reliable and repeatable indicators provides novel tools to help understand individual variations of range-use in free-range farming.

Gender perspective on the association between liver enzyme markers and non-alcoholic fatty liver disease: insights from the general population

Objective

Every distinct liver enzyme biomarker exhibits a strong correlation with non-alcoholic fatty liver disease (NAFLD). This study aims to comprehensively analyze and compare the associations of alanine aminotransferase (ALT), aspartate aminotransferase (AST), and gamma-glutamyl transferase (GGT) with NAFLD from a gender perspective.

Methods

This study was conducted on 6,840 females and 7,411 males from the NAGALA cohort. Multivariable logistic regression analysis was used to compare the associations between liver enzyme markers and NAFLD in both genders, recording the corresponding adjusted odds ratios (ORs) and 95% confidence intervals (CIs). Receiver operating characteristic (ROC) curves were used to evaluate the accuracy of individual liver enzyme markers and different combinations of them in identifying NAFLD.

Results

Liver enzyme markers ALT, AST, and GGT were all independently associated with NAFLD and exhibited significant gender differences (All P-interaction<0.05). In both genders, ALT exhibited the most significant association with NAFLD, with adjusted standardized ORs of 2.19 (95% CI: 2.01-2.39) in males and 1.60 (95% CI: 1.35-1.89) in females. Additionally, ROC analysis showed that ALT had significantly higher accuracy in identifying NAFLD than AST and GGT in both genders (Delong P-value < 0.05), and the accuracy of ALT in identifying NAFLD in males was higher than that in females [Area under the ROC curve (AUC): male 0.79, female 0.77]. Furthermore, out of the various combinations of liver enzymes, ALT+GGT showed the highest accuracy in identifying NAFLD in both genders, with AUCs of 0.77 (95% CI: 0.75-0.79) in females and 0.79 (95% CI: 0.78-0.81) in males.

Conclusion

Our study revealed significant gender differences in the associations of the three commonly used liver enzyme markers with NAFLD. In both genders, the use of ALT alone may be the simplest and most effective tool for screening NAFLD, especially in males.

Association between disruption of circadian activity rhythms and obesity

This cross-sectional study aimed to elucidate the association between disruption of circadian activity rhythms and obesity-related indices. This study included 69 older participants (male, n = 36; female, n = 33), and disruption of circadian activity rhythms in daily life was assessed using the cosinor method based on physical activity data. The daily physical activity data were fitted to a cosine curve to estimate the peak phase (acrophase), and the difference in the peak phase (time) for each day was determined. The standard deviation (SD) of the mean peak phase differences over 6 days was obtained. The higher the SD value, the more disturbed the circadian rhythm of activity. Based on the calculated values, the samples were divided into tertiles (small, medium, and large). A significant positive correlation was found between Log SD and body fat percentage on the disruption of circadian activity rhythms and obesity-related indices. In addition, positive associations were observed among body mass, body mass index, and Log SD. However, these associations were not observed in women. These results suggest that disruption of circadian activity rhythms is associated with obesity-related indices and may differ according to sex.

Diurnal differences in urine flow in healthy young men in a light-controlled environment: a randomized crossover design

BACKGROUND

Older men often experience nocturnal urination difficulties, reflected by diurnal differences in maximum urine flow (Qmax). Since lower urinary tract symptoms and pathological comorbidities are frequent in older men, it remains unclear whether this diurnal variation is a physiological or pathological phenomenon. Our aim was to quantify the diurnal variability of Qmax in healthy young participants under varying daylight conditions in a stable environment to discern potential underlying causes of nocturnal urination difficulties.

METHODS

Twenty-one healthy young men were recruited in a 4-day study utilizing daytime (08:00-18:00) exposure with two light conditions in randomized order: dim (< 50 lx) or bright (~2500 lx). Day 1 was for acclimation, and urine flow was assessed from day 2. The participants urinated ad libitum during day 2 and then at fixed 3-4-h intervals thereafter (days 3-4). Regular urination Qmax at late night (04:00) on day 4 was compared with the nearest voided volume during daytime of day 3 (mDay).

RESULTS

Morning Qmax scores (after bed-11:00) on day 2 were significantly lower than evening (17:00-before pre-sleep) in bright conditions and those of daytime (11:00-17:00), evening (17:00-before pre-sleep), and pre-sleep in dim conditions. Pre-sleep Qmax during the ad libitum period was significantly higher in dim than bright conditions. Late-night Qmax values (04:00) on day 4 were significantly lower than Qmax scores of mDay on day 3 in both light conditions.

CONCLUSIONS

Healthy young men had a clear diurnal Qmax difference that decreased during late night and morning. In addition, the pre-sleep Qmax values in dim daylight were significantly higher than in bright daylight. Taken together, we conclude that late-night and morning decreases in Qmax are an instinctive physiological phenomenon in humans, and the diurnal difference of Qmax can be influenced by daylight conditions.

Intestinal microbial circadian rhythms drive sex differences in host immunity and metabolism

Circadian rhythms dynamically regulate sex differences in metabolism and immunity, and circadian disruption increases the risk of metabolic disorders. We investigated the role of sex-specific intestinal microbial circadian rhythms in host metabolism using germ-free and conventionalized mice and manipulation of dietary-derived fat, fiber, and microbiota-accessible carbohydrates. Our findings demonstrate that sex differences in circadian rhythms of genes involved in immunity and metabolism depend on oscillations in microbiota, microbial metabolic functions, and microbial metabolites. Further, we show that consuming an obesogenic, high-fat, low-fiber diet produced sex-specific changes in circadian rhythms in microbiota, metabolites, and host gene expression, which were linked to sex differences in the severity of metabolic dysfunction. Our results reveal that microbial circadian rhythms contribute to sex differences in immunity and metabolism and that dietary factors can entrain new circadian rhythms and modify the magnitude of sex differences in host-microbe circadian dynamics.

Sex-specific differences in the circadian pattern of action potential firing by rat suprachiasmatic nucleus vasopressin neurons

The suprachiasmatic nucleus (SCN) of the hypothalamus serves as the master circadian clock in mammals. Most SCN neurons express the inhibitory neurotransmitter GABA (gamma amino butyric acid) along with a peptide cotransmitter. Notably, the neuropeptides vasopressin (VP) and vasoactive intestinal peptide (VIP) define two prominent clusters within the SCN: those located in the ventral core (VIP) and those forming the dorsomedial "shell" of the nucleus (VP). Axons emerging from VP neurons in the shell are thought to mediate much of the SCN's output to other brain regions as well as VP release into the cerebrospinal fluid (CSF). Previous work has shown that VP release by SCN neurons is activity dependent and SCN VP neurons fire action potentials at a higher rate during the light phase. Accordingly, CSF VP levels are higher during daytime. Interestingly, the amplitude of the CSF VP rhythm is greater in males than females, suggesting the existence of sex differences in the electrical activity of SCN VP neurons. Here we investigated this hypothesis by performing cell-attached recordings from 1070 SCN VP neurons across the entire circadian cycle in both sexes of transgenic rats that express green fluorescent protein (GFP) driven by the VP gene promoter. Using an immunocytochemical approach we confirmed that >60% of SCN VP neurons display visible GFP. Recordings in acute coronal slices revealed that VP neurons display a striking circadian pattern of action potential firing, but the characteristics of this activity cycle differ in males and females. Specifically, neurons in males reached a significantly higher peak firing frequency during subjective daytime compared to females and the acrophase occurred ~1 h earlier in females. Peak firing rates in females were not significantly different at various phases of the estrous cycle.

Therapeutic Aspects of Circadian Rhythms

Circadian rhythms are ubiquitous endogenous rhythms with a period of approximately twenty-four hours [...].

Acute exposure to artificial light at night alters hippocampal vascular structure in mice

The structure and function of the cardiovascular system are modulated across the day by circadian rhythms, making this system susceptible to circadian rhythm disruption. Recent evidence demonstrated that short-term exposure to a pervasive circadian rhythm disruptor, artificial light at night (ALAN), increased inflammation and altered angiogenic transcripts in the hippocampi of mice. Here, we examined the effects of four nights of ALAN exposure on mouse hippocampal vascular networks. To do this, we analyzed 2D and 3D images of hippocampal vasculature and hippocampal transcriptomic profiles of mice exposed to ALAN. ALAN reduced vascular density in the CA1 and CA2/3 of female mice and the dentate gyrus of male mice. Network structure and connectivity were also impaired in the CA2/3 of female mice. These results demonstrate the rapid and potent effects of ALAN on cerebrovascular networks, highlighting the importance of ALAN mitigation in the context of health and cerebrovascular disease.

Chronotherapy in dentistry: A scoping review

The circadian clock modulates almost all vital aspects of our physiology and metabolism, including processes relevant to dentistry, such as healing, inflammation and nociception. Chronotherapy is an emerging field aiming to improve therapeutic efficacy and decrease adverse effects on health outcomes. This scoping review aimed to systematically map the evidence underpinning chronotherapy in dentistry and to identify gaps in knowledge. We conducted a systematic scoping search using four databases (Medline, Scopus, CINAHL and Embase). We identified 3908 target articles screened by two blinded reviewers, and only original animal and human studies investigating the chronotherapeutic use of drugs or interventions in dentistry were included. Of the 24 studies included, 19 were human studies and five were animal studies. Chrono-radiotherapy and chrono-chemotherapy reduced treatment side effects and improved therapeutic response, leading to higher survival rates in cancer patients. Animal studies reported that tooth movement and periodontal tissue response to orthodontic forces follow a diurnal rhythm that might influence bone metabolism. Profound and prolonged local anesthesia could be achieved when injected in the evening. Although the overall quality of the included studies was low, chronotherapy applications in dentistry seem to have favourable outcomes, especially in head and neck cancer treatments.

Chemotherapy delivery time affects treatment outcomes of female patients with diffuse large B cell lymphoma

BACKGROUNDChronotherapy is a drug intervention at specific times of the day to optimize efficacy and minimize adverse effects. Its value in hematologic malignancy remains to be explored, in particular in adult patients.METHODSWe performed chronotherapeutic analysis using 2 cohorts of patients with diffuse large B cell lymphoma (DLBCL) undergoing chemotherapy with a dichotomized schedule (morning or afternoon). The effect of a morning or afternoon schedule of rituximab plus cyclophosphamide, doxorubicin, vincristine, and prednisone (R-CHOP) on survival and drug tolerability was evaluated in a survival cohort (n = 210) and an adverse event cohort (n = 129), respectively. Analysis of about 14,000 healthy individuals followed to identify the circadian variation in hematologic parameters.RESULTSBoth progression-free survival (PFS) and overall survival (OS) of female, but not male, patients were significantly shorter when patients received chemotherapy mostly in the morning (PFS HR 0.357, P = 0.033; and OS HR 0.141, P = 0.032). The dose intensity was reduced in female patients treated in the morning (cyclophosphamide 10%, P = 0.002; doxorubicin 8%, P = 0.002; and rituximab 7%, P = 0.003). This was mainly attributable to infection and neutropenic fever: female patients treated in the morning had a higher incidence of infections (16.7% vs. 2.4%) and febrile neutropenia (20.8% vs. 9.8%) as compared with those treated in the afternoon. The sex-specific chronotherapeutic effects can be explained by the larger daily fluctuation of circulating leukocytes and neutrophils in female than in male patients.CONCLUSIONIn female DLBCL patients, R-CHOP treatment in the afternoon can reduce toxicity while it improves efficacy and survival outcome.FUNDINGNational Research Foundation of Korea (NRF) grant funded by the Korean government (grant number NRF-2021R1A4A2001553), Institute for Basic Science IBS-R029-C3, and Human Frontiers Science Program Organization Grant RGY0063/2017.

The Ventral Tegmental Area and Nucleus Accumbens as Circadian Oscillators: Implications for Drug Abuse and Substance Use Disorders

Circadian rhythms convergently evolved to allow for optimal synchronization of individuals’ physiological and behavioral processes with the Earth’s 24-h periodic cycling of environmental light and temperature. Whereas the suprachiasmatic nucleus (SCN) is considered the primary pacemaker of the mammalian circadian system, many extra-SCN oscillatory brain regions have been identified to not only exhibit sustainable rhythms in circadian molecular clock function, but also rhythms in overall region activity/function and mediated behaviors. In this review, we present the most recent evidence for the ventral tegmental area (VTA) and nucleus accumbens (NAc) to serve as extra-SCN oscillators and highlight studies that illustrate the functional significance of the VTA’s and NAc’s inherent circadian properties as they relate to reward-processing, drug abuse, and vulnerability to develop substance use disorders (SUDs).