Diurnal Rhythm Research Articles

Association of Rest-Activity Rhythm and Risk of Developing Dementia or Mild Cognitive Impairment in the Middle-Aged and Older Population: Prospective Cohort Study.

The relationship between 24-hour rest-activity rhythms (RARs) and risk for dementia or mild cognitive impairment (MCI) remains an area of growing interest. Previous studies were often limited by small sample sizes, short follow-ups, and older participants. More studies are required to fully explore the link between disrupted RARs and dementia or MCI in middle-aged and older adults. We leveraged the UK Biobank data to examine how RAR disturbances correlate with the risk of developing dementia and MCI in middle-aged and older adults. We analyzed the data of 91,517 UK Biobank participants aged between 43 and 79 years. Wrist actigraphy recordings were used to derive nonparametric RAR metrics, including the activity level of the most active 10-hour period (M10) and its midpoint, the activity level of the least active 5-hour period (L5) and its midpoint, relative amplitude (RA) of the 24-hour cycle [RA=(M10-L5)/(M10+L5)], interdaily stability, and intradaily variability, as well as the amplitude and acrophase of 24-hour rhythms (cosinor analysis). We used Cox proportional hazards models to examine the associations between baseline RAR and subsequent incidence of dementia or MCI, adjusting for demographic characteristics, comorbidities, lifestyle factors, shiftwork status, and genetic risk for Alzheimer's disease. During the follow-up of up to 7.5 years, 555 participants developed MCI or dementia. The dementia or MCI risk increased for those with lower M10 activity (hazard ratio [HR] 1.28, 95% CI 1.14-1.44, per 1-SD decrease), higher L5 activity (HR 1.15, 95% CI 1.10-1.21, per 1-SD increase), lower RA (HR 1.23, 95% CI 1.16-1.29, per 1-SD decrease), lower amplitude (HR 1.32, 95% CI 1.17-1.49, per 1-SD decrease), and higher intradaily variability (HR 1.14, 95% CI 1.05-1.24, per 1-SD increase) as well as advanced L5 midpoint (HR 0.92, 95% CI 0.85-0.99, per 1-SD advance). These associations were similar in people aged <70 and >70 years, and in non-shift workers, and they were independent of genetic and cardiovascular risk factors. No significant associations were observed for M10 midpoint, interdaily stability, or acrophase. Based on findings from a large sample of middle-to-older adults with objective RAR assessment and almost 8-years of follow-up, we suggest that suppressed and fragmented daily activity rhythms precede the onset of dementia or MCI and may serve as risk biomarkers for preclinical dementia in middle-aged and older adults.

Characterisation of the daily rhythm of salivary androgens in healthy women and in women with polycystic ovary syndrome by liquid chromatography-tandem mass spectrometry

Characterisation of the daily rhythm of salivary androgens in healthy women and in women with polycystic ovary syndrome by liquid chromatography-tandem mass spectrometry

102 Circadian patterns of behavior, respiration, rectal temperature, saliva melatonin, cytokine concentrations, and milk immune cells are altered by cooling heat-stressed lactating sows

Abstract Lactating sows are particularly vulnerable to heat stress (HS) due to the increased metabolism from milk production. A greater understanding of HS response could assist in mitigating its detrimental effects on animal production. Two core circadian clock genes were pinpointed in a recent genome study as potential mediators of HS response, indicating the possible alteration of circadian clocks by HS exposure. This study aimed to assess how cooling of lactating sows under natural heat stress conditions in the summer influenced circadian patterns of respiration rate (RR), rectal temperature (RT), behaviors, salivary concentration of cortisol and melatonin, milk cell populations and relative abundance of multiple cytokines in saliva. Lactating sows of mixed parities were divided into two treatment groups: treated with electronic cooling pad (C; n=9) and heat-stressed control (H; n=9). Experiments were conducted during two 48 h periods of increased environmental temperatures from summer heatwaves. During the initial 48 h period, rectal temperature (RT) was monitored every 60 min, rectal temperature (RT) every 30 min, and behaviors of eating, standing, sitting, laying, sleeping, drinking, and nursing every 5 min. Morning milk samples were collected following the completion of the first phase and utilized to categorize and count somatic cells. The second trial was approximately 1 wk later, and during this period saliva samples were collected every 4 h over the 48-h period. Results were analyzed for significant effect of treatments and interaction using periodic regression while circadian patterns were further detected by incorporating a Fourier series model utilizing sine-cosine variables that denote a fit and/or shift in circadian pattern. The analysis revealed that cooling decreased RT and RR while also modifying circadian patterns (P &amp;lt; 0.05). Cooling had no impact on the percentage of time spent in any activity over the 48-h period (P &amp;gt; 0.05). Nevertheless, the daily patterns of eating, standing, and sitting were different between the treatments (P &amp;lt; 0.05). A shift in eating time to later in the day in H sows relative to C sows related to a second rise in RT during the dark phase of the light-dark cycle (P &amp;lt; 0.05). Saliva melatonin concentrations were increased in C sows and circadian pattern altered relative to H (P &amp;lt; 0.05), but there was no effect on salivary cortisol concentrations (P &amp;gt; 0.05). Cooling reduced milk lymphocytes (P &amp;lt; 0.05) and influenced diurnal pattern of saliva cytokines including interleukins (IL) IL-1 alpha, IL-1 beta, IL-10, and IL-15 and transforming growth factor-beta 1. In conclusion, the cooling of heat-stressed sows altered the circadian patterns of physiology, behavior and melatonin, suggesting the need for additional research to investigate whether circadian disruption contributes to reduced production efficiency observed in HS animals.

Circadian rhythm of salivary and serum urea concentration in alpacas and sheep receiving diets with different levels of protein.

All vertebrates possess a daily rhythm, encompassing a comprehensive set of physiological, cognitive, and behavioral patterns that manifest throughout a 24-hour period. The aim of this study was to compare the effect of crude protein (CP) levels in the diet on the daily rhythm of urea in serum (US) and saliva in alpacas and sheep. Ten alpacas and ten sheep, adult, clinically healthy males, were used; they were maintained in natural light conditions and fed ad libitum with two levels of CP (16 and 7%). Blood and saliva samples were taken every 4h for 48h. A two-way ANOVA was conducted to analyze the parameters, including adjusted mean rhythm (MESOR), amplitude, and acrophase. It was found that both US and saliva urea exhibited circadian rhythms with a peak during the midday (10:59 - 12:16h). The MESOR with low CP diets was higher (P < 0.05) in alpacas. The MESOR of urea levels in saliva was greater (P < 0.05) at the highest level of CP in the diet, with no differences between alpacas and sheep (P > 0.05). The amplitude was greater (P < 0.05) in alpacas and at the high level of CP compared to the low level of CP in the diet. Our findings reveal that both serum and saliva urea levels in alpacas and sheep follow a daily rhythm and the MESOR of US was higher in alpacas when they consume food with low CP content, and this difference disappears when CP levels are increased in the diet.

Two Old Wild-Type Strains of Drosophila melanogaster Can Serve as an Animal Model of Faster and Slower Aging Processes.

Drosophila melanogaster provides a powerful platform to study the physiology and genetics of aging, i.e., the mechanisms underpinnings healthy aging, age-associated disorders, and acceleration of the aging process under adverse environmental conditions. Here, we tested the responses of daily rhythms to age-accelerated factors in two wild-type laboratory-adapted strains, Canton-S and Harwich. On the example of the 24 h patterns of locomotor activity and sleep, we documented the responses of these two strains to such factors as aging, high temperature, carbohydrate diet, and diet with different doses of caffeine-benzoate sodium. The strains demonstrated differential responses to these factors. Moreover, compared to Canton-S, Harwich showed a reduced locomotor activity, larger amount of sleep, faster rate of development, smaller body weight, lower concentrations of main sugars, lower fecundity, and shorter lifespan. It might be recommended to use at least two strains, one with a relatively fast and another with a relatively slow aging process, for the experimental elaboration of relationships between genes, environment, behavior, physiology, and health.

Circadian ABCG2 Expression Influences the Brain Uptake of Donepezil across the Blood-Cerebrospinal Fluid Barrier.

Donepezil (DNPZ) is a cholinesterase inhibitor used for the management of Alzheimer's disease (AD) and is dependent on membrane transporters such as ABCG2 to actively cross brain barriers and reach its target site of action in the brain. Located in the brain ventricles, the choroid plexus (CP) forms an interface between the cerebrospinal fluid (CSF) and the bloodstream, known as the blood-CSF barrier (BCSFB). Historically, the BCSFB has received little attention as a potential pathway for drug delivery to the central nervous system (CNS). Nonetheless, this barrier is presently viewed as a dynamic transport interface that limits the traffic of molecules into and out of the CNS through the presence of membrane transporters, with parallel activity with the BBB. The localization and expression of drug transporters in brain barriers represent a huge obstacle for drug delivery to the brain and a major challenge for the development of therapeutic approaches to CNS disorders. The widespread interest in understanding how circadian clocks modulate many processes that define drug delivery in order to predict the variability in drug safety and efficacy is the next bridge to improve effective treatment. In this context, this study aims at characterizing the circadian expression of ABCG2 and DNPZ circadian transport profile using an in vitro model of the BCSFB. We found that ABCG2 displays a circadian pattern and DNPZ is transported in a circadian way across this barrier. This study will strongly impact on the capacity to modulate the BCSFB in order to control the penetration of DNPZ into the brain and improve therapeutic strategies for the treatment of AD according to the time of the day.

Longitudinal associations of diurnal rest-activity rhythms with fatigue, insomnia, and health-related quality of life in survivors of colorectal cancer up to 5 years post-treatment

BackgroundThere is a growing population of survivors of colorectal cancer (CRC). Fatigue and insomnia are common symptoms after CRC, negatively influencing health-related quality of life (HRQoL). Besides increasing physical activity and decreasing sedentary behavior, the timing and patterns of physical activity and rest over the 24-h day (i.e. diurnal rest-activity rhythms) could also play a role in alleviating these symptoms and improving HRQoL. We investigated longitudinal associations of the diurnal rest-activity rhythm (RAR) with fatigue, insomnia, and HRQoL in survivors of CRC.MethodsIn a prospective cohort study among survivors of stage I-III CRC, 5 repeated measurements were performed from 6 weeks up to 5 years post-treatment. Parameters of RAR, including mesor, amplitude, acrophase, circadian quotient, dichotomy index, and 24-h autocorrelation coefficient, were assessed by a custom MATLAB program using data from tri-axial accelerometers worn on the upper thigh for 7 consecutive days. Fatigue, insomnia, and HRQoL were measured by validated questionnaires. Confounder-adjusted linear mixed models were applied to analyze longitudinal associations of RAR with fatigue, insomnia, and HRQoL from 6 weeks until 5 years post-treatment. Additionally, intra-individual and inter-individual associations over time were separated.ResultsData were available from 289 survivors of CRC. All RAR parameters except for 24-h autocorrelation increased from 6 weeks to 6 months post-treatment, after which they remained relatively stable. A higher mesor, amplitude, circadian quotient, dichotomy index, and 24-h autocorrelation were statistically significantly associated with less fatigue and better HRQoL over time. A higher amplitude and circadian quotient were associated with lower insomnia. Most of these associations appeared driven by both within-person changes over time and between-person differences in RAR parameters. No significant associations were observed for acrophase.ConclusionsIn the first five years after CRC treatment, adhering to a generally more active (mesor) and consistent (24-h autocorrelation) RAR, with a pronounced peak activity (amplitude) and a marked difference between daytime and nighttime activity (dichotomy index) was found to be associated with lower fatigue, lower insomnia, and a better HRQoL. Future intervention studies are needed to investigate if restoring RAR among survivors of CRC could help to alleviate symptoms of fatigue and insomnia while enhancing their HRQoL.Trial registrationEnCoRe study NL6904 (https://www.onderzoekmetmensen.nl/).

Abstract PO2-07-01: Predicted Circadian-related Transcription Factors in Human Breast Cell Lines–A key to understanding breast cancer pathology?

Abstract Studies show that disrupted circadian clocks are associated with breast and other forms of cancer. However, the pathways and cell processes linking broken circadian clocks to breast cancer are still mostly unknown. In this study, we conducted a reanalysis of mRNA expression in breast cell lines, specifically MCF10a (a fibrocystic cell line) and MCF7 (a metastatic adenocarcinoma cell line). To achieve this, we utilized microarray data obtained from Gutierrez et al. in 2016, specifically the datasets GSE76370, GSE76368, and GSE76369. First, Metacycle, an R statistical package employing a cosine fitting algorithm, was used to identify circadian-oscillations in mRNA expression from both cell lines. MetaCycle (Wu et al., 2016) analysis produced an amplitude, phase, and period value for each circadian gene. Following the analysis, we conducted principal component analysis on the Metacycle output to identify any outlier genes. Subsequently, hierarchical clustering analysis was employed to group these outlier genes based on their oscillating expression levels, with the purpose of identifying clusters that exhibited similar period and phase patterns. We hypothesized that genes found in the same cluster would share common transcription factors that would drive and synchronize the expression of those genes. We tested this hypothesis and found that genes with the same circadian pattern did indeed share common transcription factor binding sites, using Ciiider 3.0 (Gearing et al, 2019), an internet-based tool for predicting and analyzing transcription factor binding sites. We found 96 genes grouped into 6 clusters for MCF10a, and 92 genes grouped into 6 for MCF7 cell lines. Arid3A binding sites were highly enriched across MCF7 and MCF10a. In MCF10a, where circadian oscillations were more pronounced, Sox5 binding sites were highly enriched for cluster 1, Meis1 was enriched for cluster 2, and Arid3A was enriched in clusters 3-6, in combination with other transcription factors. In MCF7, a different set of genes showed circadian-like oscillating expression patterns. However, these different genes showed enrichment of Arid3A across all clusters. Since Arid3A binding sites were found in genes involved in all of the MCF7 clusters, and found in four of the six clusters in MCF10a, further work is needed in understanding the additional regulatory mechanisms that shift the phase and period of the oscillations of these groups of genes. In addition, more work needs to be done to study the role of these transcription factors in cancer progression and basic cell processes. Most of these transcription factors are known to be related to breast or other forms of cancer. Though this list is not complete, some of the more enriched transcription factor binding sites include Arid3A, Meis1, Znf354c, in MCF10a and in MCF7 they include Arid3A, Znf354c, Nfatc2, and Ahr:Arnt. The most enriched transcription factor amongst these circadian-like genes is Arid3A. Arid3A is an H3K9me3 demethylase and may impact regulation of other genes through demethylation. Suppression of Arid3A is associated with leukemia. Meis1 is also implicated in leukemia and tumor growth, as well as sleep disorders. Arnt splice variants are also associated with breast cancer. Future research is needed to determine if these transcription factors are important for circadian-like control. Our in silico results suggest that genes found in the same clusters share their respective transcription factors that regulate the expression of these circadian-like genes. Citation Format: Yocanxóchitl Perfecto-Avalos, Janice Yoo, Cinthya Saravia Heyman, Princess Jemeala Deranamie, John Tran, Sean-Patrick Scott. Predicted Circadian-related Transcription Factors in Human Breast Cell Lines–A key to understanding breast cancer pathology? [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO2-07-01.

EXERCISE AS MEDICINE; CHRONOTHERAPY IN HYPERTENSION MANAGEMENT

Objective: Adequate blood pressure regulation is a critical target in the management of hypertension and CVD. Circadian rhythms are increasingly recognized for their impacts on health outcomes including vascular function and metabolism. We posited that optimized exercise combined with chronotherapy will lead to meaningful improvements in BP, vascular health, and cardiovascular outcomes by coordinating the timing of interventions with diurnal rhythms. Design and method: Our studies, funded by National Institute of Health (NIH), are focused on ambulatory BP monitoring (ABPM) to capture circadian variations in BP, including nocturnal BP and morning surge. In particular, the project focuses on the efficacy of physical activity to improve nocturnal BP. We are using a 48-hr period of ABPM to reliably access nocturnal BP, which has not been implemented in other exercise studies focusing on ambulatory BP, in addition to measuring sleep with actigraphy. Given nocturnal BP is recognized as a strong indicator of cardiovascular health and outcomes, examining how interventions modify this ambulatory BP outcome is needed to understand the effect of the intervention on health and future risk. Results: Our preliminary data on all non-Hispanic 22 female subjects included 7 African Americans with average age of 68 and average BMI of 30.6. Mean seated BP (all BP values reported in mm of Hg) was 135/73 while awake BP from ABPM was 135/76 and awake central BP (calculated with device using a proprietary algorithm) was 126/78. Mean asleep BP determined from analysis of wrist actigraphy data was 117/61 and mean asleep central BP was 112/64. Mean nocturnal BP (calculated by average of the 4 lowest systolic blood pressure measures during the asleep period, waiting at least 1 hour after going to bed) was 116.7/61.6. Average nocturnal systolic dip was 30.4 and nocturnal diastolic dip was 14.4 with percentage nocturnal dips at 20.3% and 14.2% respectively. Conclusions: In our preliminary results, we found that evening exercise as chronotherapy in hypertensive post-menopausal patients showed significant nocturnal dipping of blood pressure.

Differential Responses of Spinal Microglia to Low-Dose LPS Delivered in the Daily Rest vs Active Phase

Virtually all lung and neural disorders are associated with systemic and/or neuro-inflammation. Neuro-inflammation impairs important forms of neuroplasticity associated with cognitive and spinal motor learning ( e.g., respiratory motor plasticity). Microglia are resident CNS innate immune cells that regulate diverse processes including neuroinflammation and multiple forms of neuroplasticity via neuron-microglia interactions. Brain microglia exhibit profound diurnal rhythms in their response to pro-inflammatory stimuli, such as toll-like receptor 4 (TLR4) activation. Although hippocampal microglia develop a pro-inflammatory phenotype in response to TLR4 activation during the daily rest phase, little is known concerning spinal microglial responses to inflammatory stimuli across the daily rest/active cycle. Thus, we tested the hypothesis that ventral spinal microglia near the phrenic motor nucleus differentially respond to low-dose systemic lipopolysaccharide (LPS) delivered in the rest (12PM) vs active (12AM) phase. Specifically, we investigated microglial responses to systemic inflammation induced by low-dose LPS (0.1mg/kg, i.p.) in 2 populations of adult Sprague-Dawley rats (both 3-6 months old): 1) SD wildtype and 2) SD rats with humanized neuro-neutral apolipoprotein 3 (h APOE3) knock-in. All rats received intrapleural Cholera toxin B (CtB) injections 2 weeks prior to harvest to identify phrenic motor neurons. Twenty-four hours post-LPS or vehicle (0.9% saline), rats were perfused with 1X PBS and fixed with 4% PFA. Spinal tissues containing the phrenic motor nucleus (cervical 3-6) were harvested and dehydrated in 30% sucrose for immunohistochemistry. Activated microglia near phrenic motor neurons were visualized with an Iba-1 antibody and quantified and phenotyped based on morphology. Since no differences in microglia were found between wildtype and h APOE3 rats, data were combined into a single group for analyses. In vehicle-treated rats, robust Iba-1 staining near phrenic motor neurons was observed in the active, but not rest phase. In contrast, Iba-1 staining in LPS treated rats was elevated only when LPS was administered in the rest (not active) phase. After rest-phase LPS injections, microglial cell bodies were larger and had more processes compared to rest-phase controls. In the active phase, spinal microglia were similar between vehicle and LPS injected rats. Thus, spinal microglia exhibit a profound diurnal rhythm in (morphological) responses to systemic inflammation ( i.e. LPS). Further studies are needed to identify specific molecules driving time-of-day differences in spinal microglial responses to pro-inflammatory stimuli. Nevertheless, these findings increase our understanding of how diurnal rhythms impact cellular responses to physiological challenges, such as inflammation. Further, our results yield clues concerning diurnal variations in phrenic motor plasticity, since reciprocal phrenic motor neuron/microglial communication is an important regulator of phrenic motor plasticity. NIH R01HL148030 (GSM), NIH R01HL149800 (GSM), NIH T32HL134621-5 (ABM). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

The Integrated Stress Response Regulates Diurnal Rhythms in Liver Metabolism

Disruptions in biological rhythms are associated with the development of metabolic diseases. General control nonderepressible 2 (GCN2), a primary sensor of amino acid insuffciency and activator of the integrated stress response (ISR), plays an integral role in liver metabolism. The objective of this work was to examine the impact of feeding a low protein quality (LPQ) diet on diurnal rhythms in liver metabolism. We hypothesized that activation of the ISR by GCN2 maintains metabolic rhythms within the liver during LPQ feeding. To address our objective, wild type (WT) and whole body Gcn2 knockout (GCN2KO) mice were housed in total darkness and provided free access to either a Control or a LPQ diet (devoid of leucine) for 8-days and then killed at 2 circadian time (CT) points 12-hours apart (CT3, CT15). WT mice fed a Control diet showed oscillations in hepatic ISR activation that were lost in the livers of GCN2KO mice. Diurnal patterns in the liver transcriptome including genes regulating triglyceride metabolism were also dampened in GCN2KO mice. WT mice fed LPQ showed increased hepatic ISR activation and greater abundance of ISR target genes relative to Control only at CT15 (p&lt;0.05 by two factor ANOVA). GCN2KO mice fed LPQ failed to show oscillations in ISR activation and instead displayed reductions in liver intracellular amino acids alongside significant upregulation of genes encoding gluconeogenesis and amino acid catabolism at CT15 (q&lt;0.05, Log2FC&gt;1). In conclusion, GCN2 is required for diurnal ISR activation and execution in the liver. LPQ feeding increases hepatic ISR activation in a time dependent manner. Sensing of LPQ by GCN2 is necessary for the maintenance of rhythms in liver macronutrient metabolism. NIH DK109714, Pilot award from the NJ IFNH Center for Human Nutrition, Exercise, and Metabolism (NExT). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Virulence is associated with daily rhythms in the within-host replication of the malaria parasite Plasmodium chabaudi.

Most malaria (Plasmodium spp.) parasite species undergo asexual replication synchronously within the red blood cells of their vertebrate host. Rhythmicity in this intraerythrocytic developmental cycle (IDC) enables parasites to maximise exploitation of the host and align transmission activities with the time of day that mosquito vectors blood feed. The IDC is also responsible for the major pathologies associated with malaria, and plasticity in the parasite's rhythm can confer tolerance to antimalarial drugs. Both the severity of infection (virulence) and synchrony of the IDC vary across species and between genotypes of Plasmodium; however, this variation is poorly understood. The theory predicts that virulence and IDC synchrony are negatively correlated, and we tested this hypothesis using two closely related genotypes of the rodent malaria model Plasmodium chabaudi that differ markedly in virulence. We also test the predictions that, in response to perturbations to the timing (phase) of the IDC schedule relative to the phase of host rhythms (misalignment), the virulent parasite genotype recovers the correct phase relationship faster, incurs less fitness losses and so hosts benefit less from misalignment when infected with a virulent genotype. Our predictions are partially supported by results suggesting that the virulent parasite genotype is less synchronous in some circumstances and recovers faster from misalignment. While hosts were less anaemic when infected by misaligned parasites, the extent of this benefit did not depend on parasite virulence. Overall, our results suggest that interventions to perturb the alignment between the IDC schedule, and host rhythms and increase synchrony between parasites within each IDC, could alleviate disease symptoms. However, virulent parasites, which are better at withstanding conventional antimalarial treatment, would also be intrinsically better able to tolerate such interventions.

AgRP Neurons Encode Circadian Feeding Time

Food intake follows a predictable daily pattern and synchronizes metabolic rhythms. Neurons expressing Agouti-related protein (AgRP) read out physiological energetic state and elicit feeding, but the regulation of these neurons across daily timescales is poorly understood. Using a combination of neuron-dynamics measurements and timed optogenetic activation in mice, we show that daily AgRP-neuron activity was not fully consistent with existing models of homeostatic regulation. Instead of operating as deprivation counter, AgRP-neuron activity primarily followed the circadian rest-activity cycle through a process that required an intact suprachiasmatic nucleus (SCN) and synchronization by light. Imposing novel feeding patterns through time-restricted food access or periodic AgRP-neuron stimulation was suffcient to resynchronize the daily AgRP-neuron activity rhythm and drive anticipatory-like behavior through a process that required DMHPDYN neurons. These results indicate that AgRP-neurons integrate time-of-day information of past feeding experience with current metabolic needs to predict circadian feeding time. This work is supported by NIH to D.A. R01DK126740. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Prolonged Blue Light Exposure Does Not Elicit Adverse Changes to Physical Activity in Male Mice

Color plays a role in human and animal circadian rhythm patterns, behaviors, and emotional responses. Environments containing blue colors improve information storage in humans and reproductive success in animals; however, environments containing blue light influence behavioral and emotional responses in rodents and humans in adverse ways. Exposure to blue light alters sleeping patterns, induces the stress response, and elicits depressive behaviors. These initial responses then affect awake time functionality and productivity. Under normal physiological conditions, mice, when provided access to an in-cage running wheel, exhibit high levels of nocturnal physical activity behavior. It is unknown if this nocturnal behavior changes after prolonged blue light exposure. Therefore, this project's hypothesis is wheel running utilization decreases after exposure to blue light during the diurnal restful period in the normally nocturnal mouse. The purpose of this study was to expose mice to overhead blue LED lights during the daytime rest period and to examine nighttime physical activity patterns. Daily wheel running distance, duration, and speed monitoring in C57BL/6j male mice (n=12) occurred for 21 days. During the second week of the study, an experimental group (n=6) underwent blue light-emitting diode (LED) light exposure, and a control group (n=6) experienced white LED light exposure at the same intensity. The lights were on a 12-hour light/dark cycle at full brightness during the exposure period. Differences in wheel running distance, duration, and speed following exposure to blue LED light were assessed via individual two-way (group by phase of study) ANOVAs. Blue LED light exposure did not appear to affect average daily wheel running distance [F=0.42, p=0.57], duration [F=0.79, p=0.42], or speed [F=0.08, p=0.87]. Following exposure to blue LED light during the restful diurnal period, wheel running remained stable. This lack of effect indicates that mechanisms may exist to protect mice from the adverse effects associated with blue light exposure, especially as it pertains to participating in routine physical activity. These postulated mechanisms may allow robust participation in physical activity-related behaviors in these animals and represent a potential biological regulator that could aid in mitigating the adverse effects of blue light exposure experienced in humans. All funding for this research was provided by the Union University Department of Biology. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Adrenal circadian clock protein BMAL1 regulates aldosterone and renal excretory function in a sex- and time-dependent manner

BMAL1 is a core circadian clock protein that is important for circadian rhythms of physiological function, as well as maintaining physiological homeostasis, including aspects of kidney function. Global Bmal1 knockout (KO) male mice exhibit loss of diurnal rhythm of renal sodium (Na) excretion in response to a normal or high salt diet. However, renal Na excretion rhythm remained intact in kidney-specific Bmal1 KO male mice. The adrenal gland synthesizes hormones, such as aldosterone, which influence renal electrolyte handling. The role of adrenal BMAL1 in the regulation of renal function remains unknown. The study objective was to test the hypothesis that adrenal BMAL1 is required for normal rhythms of aldosterone and renal Na handling. Male and female adrenal-specific aldosterone synthase Cre positive (AS) Bmal1 KO and littermate Cre negative, floxed control mice ( n=5-9/genotype) were acclimated to metabolic cages for 3 days then samples were collected for three days with mice on a normal salt diet followed by 7 days on a low salt diet to challenge the mice to stimulate aldosterone production. Twelve-hour food intake was measured, and urine samples were collected to measure night/day patterns in renal Na balance. Urinary aldosterone excretion was measured by ELISA. Both day and night urinary aldosterone excretion were increased following a low salt diet in control and KO male mice (ANOVA main effect of diet, p&lt;0.05). Male AS Bmal1 KO mice displayed a significant increase in day urinary aldosterone excretion following a normal and low salt diet (ANOVA main effect of genotype, p=0.0230), with a trend for an increase in night urinary aldosterone excretion ( p=0.0571). Interestingly, these genotype effects were not seen in female AS Bmal1 KO mice. Urinary aldosterone was increased following a low salt diet in female mice, but only during the nighttime in control and KO mice ( p=0.0205). Sex differences were also observed in renal Na balance, where Na balance was more positive during the day in male, but not female, AS Bmal1 KO vs. control mice (ANOVA main effect of genotype, p=0.0282). Together, these data suggest adrenal BMAL1 is required for normal rhythms of aldosterone and renal Na balance in a sex-dependent manner. Future work will investigate whether the changes in aldosterone contribute to changes in renal Na balance. This work was supported by the American Heart Association (Postdoctoral FellowshipP0240441 to H.C.; Established Investigator Award 19EIA34660135 to M.G), theRobert and Mary Cade Professorship in Physiology (to M.G.) and the NIH(F32DK121424 to G.R.C.). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Can the Assessment of the Circadian Rhythm of Pain Be Shortened? A Study of Community-Dwelling Participants with Chronic Pain.

This study aimed to juxtapose the circadian rhythm of pain with the conventional 7-day assessment and ascertain the feasibility of condensing the evaluation of the circadian rhythm of pain into a 3-day timeframe. Seventy-three patients with pain persisting for a minimum of 3 months and a numerical rating scale (NRS) score of ≥2 were recruited from three medical centers. The circadian patterns of pain were appraised over a 7-day period by quantifying the intensity of pain at six temporal junctures each day using a 10-cm visual analog scale (VAS). Cluster analysis was performed using six standardized variables derived from the VAS score of each participant at six designated time points to identify cohorts with analogous circadian rhythms of pain. The clusters were discerned for the 7- and 3-day assessments (Tuesday-Thursday, Friday-Sunday, and Sunday-Tuesday), according to the research objectives. Cohen's kappa coefficient was calculated to gauge the intra-observer variability to assess the consistency between the outcomes of the cluster analysis for the 7-day assessment and each of the 3-day assessments. The highest Cohen's kappa coefficient was observed for the 3-day evaluation spanning from Friday to Sunday, indicating a substantial concordance with the results of the 7-day assessment. Our results suggest that it may be prudent to consider implementing a condensed 3-day evaluation of the circadian rhythm of pain that is tailored to individual characteristics. This approach will allow a better understanding of the diurnal rhythms of chronic pain in patients and implement more targeted and specific pain management strategies. Furthermore, it will contribute to increased patient satisfaction through early intervention.

Cold exposure increases circulating fibroblast growth factor 21 in the evening in males and females.

Cold exposure is linked to cardiometabolic benefits. Cold activates brown adipose tissue (BAT), increases energy expenditure, and induces secretion of the hormones fibroblast growth factor 21 (FGF21) and growth differentiation factor 15 (GDF15). The cold-induced increase in energy expenditure exhibits a diurnal rhythm in men. Therefore, we aimed to investigate the effect of cold exposure on serum FGF21 and GDF15 levels in humans and whether cold-induced changes in FGF21 and GDF15 levels differ between morning and evening in males and females. In this randomized cross-over study, serum FGF21 and GDF15 levels were measured in healthy lean males (n = 12) and females (n = 12) before, during, and after 90 min of stable cold exposure in the morning (07:45 h) and evening (19:45 h) with a 1-day washout period in between. Cold exposure increased FGF21 levels in the evening compared to the morning both in males (+61% vs -13%; P < 0.001) and in females (+58% vs +8%; P < 0.001). In contrast, cold exposure did not significantly modify serum GDF15 levels, and no diurnal variation was found. Changes in FGF21 and GDF15 levels did not correlate with changes in cold-induced energy expenditure in the morning and evening. Cold exposure increased serum FGF21 levels in the evening, but not in the morning, in both males and females. GDF15 levels were not affected by cold exposure. Thus, this study suggests that the timing of cold exposure may influence cold-induced changes in FGF21 levels but not GDF15 levels and seems to be independent of changes in energy expenditure.

Does Chronotype Influence Diurnal Changes in Cardiovascular Disease Risk Factors? A Preliminary Analysis

Introduction: Humans experience diurnal fluctuations in the prevalence of cardiovascular events which is likely an output of endogenous circadian influence. Relatedly, vascular endothelial cell function, measured by conduit artery responsiveness to hyperemia during a flow-mediated dilation test, is supposed to follow a diurnal rhythm that is moderated by an individual’s chronotype. We therefore sought to examine the extent to which diurnal changes in other cardiovascular risk factors, such as blood pressure, cardiac chronotropy, and circulating blood leukocytes, were related to chronotype in humans. A moderating influence of chronotype on diurnal changes in the aforementioned parameters was hypothesized given prior research associating a preference for evening wakefulness with an adverse cardiometabolic phenotype. Methods: All data are presented as mean ± standard deviation. This abstract includes secondary data from a preliminary sample of 16 young (19 ± 2 years), healthy males and females. Participants completed a Munich Chronotype Questionnaire (MCQ) to quantify diurnal preference for morning or evening activity. The corrected mid-sleep time on free days (MSFSC) was calculated from the MCQ and interpreted to represent an index for morning or evening chronotype. Participants attended data collection sessions in the morning (09:16 ± 01:27 hh:mm) and again in the evening (16:19 ± 00:31 hh:mm) under resting conditions for the quantification of blood pressure and enumeration of circulating leukocytes from venous blood. Results: The sample included in this analysis had a slight preference for evening wakefulness (MSFSC = 04:58 ± 01:17 hh:mm). A significant and robust diurnal variation was found among circulating venous leukocytes (P &lt; 0.001) which measured higher in the afternoon (2.06×106 ± 3.67×105 cells/mL blood) than morning (1.61×106 ± 4.68×105 cells/mL blood). The diurnal variation in circulating venous leukocytes was independent (β = -9.87×104; R2 = 0.19; P = 0.186) of individual chronotype, as were individual diurnal changes of all other hemodynamic parameters included in this analysis (all P &gt; 0.05). More participants will be recruited to satisfy statistical power for primary outcomes. Discussion: These preliminary results from healthy, young adults indicate that individual disposition towards morning or evening wakefulness may not exert a profound influence over diurnal changes in several cardiovascular disease risk factors under resting conditions. Funding Sources: The study was funded by the Natural Sciences and Engineering Research Council of Canada (DG: 20011033) held by Dr. MJM). JMC and MIB were supported by Ontario Graduate Scholarships. JCS was supported by the Natural Sciences and Engineering Research Council of Canada Graduate Scholarships – Master’s. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Bmal1 Knockout in Rats Results in Hydrocephalus and Behavioral Defects

Circadian rhythms drive many aspects of physiology including brain water homeostasis with increased cerebral spinal fluid flow and brain parenchyma clearance during periods of sleep. Our group has previously reported maintained diurnal rhythms in blood pressure and renal function in rats lacking the core clock gene, ARNTL, or Bmal1. However, we have also observed a robust increase in brain water content and blood brain barrier permeability in knockout rats compared to wildtype (WT) controls. Patients with normal pressure hydrocephaly (NPH) display a triad of symptoms including memory dysfunction, gait disturbances, and urinary incontinence. We hypothesized that the Bmal1 knockout (Bmal1 KO) rat has behavioral symptoms similar to those seen in NPH patients. In an initial series of behavioral tests, we utilized open field and rotarod testing to measure exploratory behavior and locomotion. Following a training trial, male and female rats were tested over 4 different trials performed on sequential days. In 10 minute open field tests, Bmal1 KO rats had a trend toward decreased total movement compared to WT (1980 ± 185 vs 2369 ± 144 cm; p = 0.1430; n = 5 and 6 respectively). Anxiety-like behavior was pronounced in the Bmal1 KO rats compared to WT as evidenced by lower frequency of entries (3.6 ± 0.7 vs 11.0 ± 2.0 entries; p = 0.0098) and decreased time spent (8.0 ± 2.4 vs 25.4 ± 5.6 seconds; p = 0.0261) in the center zone of the open field. Rotarod testing of ramps from 0 to 16.5 cm/s over 5 minutes uncovered a strong trend towards decreased average distance ran (937 ± 256 vs 1540.0 ± 176 cm; p = 0.0775) and max velocity achieved (11.1 ± 1.5 vs 14.5 ± 0.8 cm/s; p = 0.0666) in Bmal1 KO compared to WT. Bmal1 KO rats also had more falling events on the rotarod compared to WT (0.95 ± 0.04 vs 0.73 ± 0.6 falls/trial; p = 0.0098). These findings indicate that in addition to the overt hydrocephalus phenotype of Bmal1KO rats and increased blood brain barrier permeability, lack of Bmal1 induces behavioral and locomotor symptoms similar to those seen in human patients with NPH. We propose that the Bmal1 KO rat can serve as a pre-clinical model for NPH and other forms of hydrocephalus and will shed light on mechanisms of altered central fluid flow that are present in many neurodegenerative diseases associated with aging. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

ACCURACY AND BLOOD PRESSURE THRESHOLD CONTROL ANALYSIS OF UNATTENDED AUTOMATED OFFICE BLOOD PRESSURE MEASUREMENT: A CROSS-SECTIONAL STUDY BASED ON MULTICENTER POPULATIONS

Objective: The emergence of unattended automated office blood pressure (u-AOBP) measurement, facilitated by the flourishing development of electronic blood pressure monitors, has been proposed as a potential alternative or complementary approach for assessing patients’ blood pressure status within clinical settings. However, robust evidence is lacking to determine its application in diagnosing hypertension within the clinical practice in China. This study aims to compare u-AOBP values with standard office blood pressure data, assess the correlation between u-AOBP and diagnostic thresholds. Design and method: The study involved participants recruited from October 2023 to February 2024 in three hospitals: People's Hospital of Gongyi City in Henan Province, Nangong City Hospital in Hebei Province, and Fuwai Hospital of the Chinese Academy of Medical Sciences. Standardized validated upper arm blood pressure monitors were used to measure blood pressure. Baseline demographic data, anthropometric measurements, u-AOBP, and standard office blood pressure data were collected, along with additional examination results, including echocardiograms and 24-hour ambulatory blood pressure monitoring. Results: 1. The difference between u-AOBP and awake dynamic average blood pressure was 1.34 mmHg (95% confidence interval: 0.88-3.55 mmHg), and the difference was not statistically significant (P = 0.236). 2. The optimal cutoff values for diagnosing elevated blood pressure using u-AOBP, determined by ROC curve analysis based on awake dynamic blood pressure measurements, were 130.75/83.75 mmHg (sensitivity 89.73%, specificity 27.27%). 3. In participants with a dipper blood pressure diurnal rhythm, there was no statistically significant difference between standard office blood pressure and u-AOBP measurements (P &gt; 0.05). However, in the group including non-dipper rhythm participants, standard office blood pressure was higher than u-AOBP by 5.84/4.98 mmHg (P &lt; 0.05). Conclusions: 1. Unattended automated blood pressure measurements can reduce, but not eliminate, the white coat effect, with an optimal cutoff value for diagnosing elevated blood pressure determined as 130.75/83.75 mmHg. 2. In individuals with a normal dipper blood pressure diurnal rhythm, standardized u-AOBP values are equivalent to standard office blood pressure.