Significant Circadian Rhythm Research Articles

Circadian rhythm of markers of bone turnover in patients with chronic kidney disease

Patients with chronic kidney disease (CKD) have a high risk of bone fractures. A circadian rhythmicity in turnover and mineralization of bone appears to be of importance for bone health. In CKD disturbances in the circadian rhythm of various functions has been demonstrated and indeed the circadian rhythm in the mineral metabolism is disturbed. The aim of the present study was to compare the circadian rhythm of bone turnover markers in ten patients with CKD to ten healthy controls. Bone turnover markers (C-terminal telopeptide of type I collagen, tartrate-resistant acid phosphatase 5b, N-terminal propeptide of type I procollagen, bone alkaline phosphatase and osteocalcin) were measured every third hour for 24 h. All bone turnover markers displayed a significant circadian rhythm in both groups and there were no significant differences in the rhythmicity between the two groups (no group*time interaction). As expected, due to the reduced renal clearance, the overall level of C-terminal telopeptide of type I collagen and osteocalcin was higher in CKD compared to the healthy controls. The present study suggests that disturbances in the circadian rhythm of bone turnover do not explain the metabolic bone disease and increased risk of fractures in CKD.

Dynamics of Erythroferrone Response to Erythropoietin in Rats.

Background: Erythroferrone (ERFE) is a hormone identified recently as a master regulator connecting iron homeostasis and erythropoiesis. Serum ERFE concentrations significantly increase in animals and humans with normal or impaired kidney function after receiving exogenous erythropoiesis-stimulating agents (ESAs), which suggests it might be a predictive factor for erythropoiesis. To evaluate whether ERFE is an early, sensitive biomarker for long-term erythropoietic effects of ESAs, we investigated the relationship between ERFE dynamics and time courses of major erythropoietic responses to ESA treatment. Methods: Healthy rats received single dose and multiple doses (thrice a week for 2 weeks) of recombinant human erythropoietin (rHuEPO) at three dose levels (100, 450, and 1350 IU/kg) intravenously. The rHuEPO and ERFE concentrations in plasma were determined at a series of time points after dosing. Erythropoietic effects including red blood cell count and hemoglobin concentrations were continuously monitored for 24 days (single dose) or 60 days (multiple doses). The expansion of erythroblasts in bone marrow was quantified by flow cytometry analysis. Results: ERFE significantly increased within a few hours and return to baseline at 24 h after rHuEPO treatment. The ERFE response was enhanced after repeated treatment, which was consistent with the observed expansion of erythroblasts in the bone marrow. In addition, the dynamics of ERFE showed double peaks at approximately 2 and 10 h after rHuEPO stimulation, and the ERFE baseline displayed a significant circadian rhythm. There was a strong positive correlation between peak values of short-term ERFE responses and the long-term hemoglobin responses. Conclusion: The stimulated release of ERFE is a rapid process within 24 h. The second peak in the ERFE response to rHuEPO suggests the presence of a feedback mechanism counterregulating the ESA stimulation. The early increase of ERFE at 2 h appears to be a predictor of the hemoglobin response at 14 days after single dose of rHuEPO. Under multiple-dose regimen, the enhanced ERFE responses still correlate with the peak hemoglobin responses. The ERFE baseline also exhibits a circadian rhythm.

Effect of age, daily rhythm and mating on pheromone titres and trapping of Glyphodes pyloalis (Lepidoptera, Crambidae)

AbstractGlyphodes pyloalis (Lepidoptera, Crambidae) is an important pest of mulberry trees in China, and current methods for accurate population monitoring and control of this pest are lacking. The sex pheromone of G. pyloalis in China was re‐identified as E10, E12, Z14‐hexadecenyl acetate (E10E12Z14‐16:Ac) and tentatively E10, E12, E14‐hexadecenyl acetate (E10E12E14‐16:Ac). The emergence began 2 h before the dark period, and the peak emergence was 3 h into scotophase. Analysing the female moth's age from 1–9 days revealed that the titre of sex pheromone E10E12Z14‐16:Ac and E10E12E14‐16:Ac did not change statistically, and the ratio remained constant at 7.19 ± 1.12. The titre of pheromone had a significant circadian rhythm, increasing at 2 h after darkness, peaking at 6–8 h before decreasing, but it was still detected after 4 h into photophase. Mating of G. pyloalis occurred mainly at night, with the highest rate during 3 h into scotophase, which was earlier than the temporal pattern of pheromone titres. 18.1% of unfed moths mated immediately after eclosion during the scotophase. This was lower than what is seen in 1–3‐day‐old moths but similar to 4‐day‐old moth. Mating can occur on the same day after emergence, primarily within 1–4 days. Female moths can release pheromone again 48 h after mating, but the ratio of E10E12Z14‐16:Ac and E10E12E14‐16:Ac was reduced to 5.1 ± 0.73. The trapping of male moths in the field showed a significant circadian rhythm, but significant differences in pheromone trapping in Sichuan Gongxian, Zhejiang Chun'an and Haining, and Jiangsu Wujiang were observed. At the same location, the circadian rhythm of moth trapping showed differences between generations. The trapping of the overwintering generation occurred mostly in the early period of scotophase, while other generations were caught slightly later. Our results contribute to effective pheromone trapping for monitoring and mass trapping to better control G. pyloalis populations.

Development of a feeding strategy for Haliotis discus hannai ♀ × Haliotis fulgens ♂ hybrids and parental H. discus hannai

The hybrid abalone Haliotis discus hannai ♀ × H. fulgens ♂ (DF) shows obvious growth advantages compared with one of its parents, H. discus hannai (DD); however, the reasons for these advantages are not fully understood. Using a video surveillance system, the current study showed that the feeding behaviors of DD and DF exhibited an obvious circadian rhythm, with significantly more feeding at night by DD and DF than during the day. In addition, the amount of time feeding by DF during the day and at night was significantly higher compared with that of DD, especially at ZT8 (20:00), ZT12 (24:00), ZT16 (04:00), and ZT20 (08:00), with the proportion of time feeding by DF increasing 2.22-, 1.60-, 2.71-, and 2.40-fold compared with those of DD, respectively. The maximum values of pepsase activity in DD and DF, of α-amylase activity in DD, and of alginate lyase activity in DF coincided with the peak feeding period. Relative to the changes in expression levels of neuropeptide Y receptor (NPYR) in the intestine, diurnal changes in NPYR expression levels in cerebral ganglia were consistent with the changes in feeding behavior, being highest at 24:00 h in both DD and DF and then declining. There was no significant difference in the circadian expression levels of cholecystokinin receptor (CCKR) in the cerebral ganglia, whereas, in the intestinal tract, peak CCKR expression levels coincided with its anorexigenic effect; the expression levels of CCKR in the intestinal tract exhibited a significant circadian rhythm in DD. These results explain the growth advantage of DF over DD in terms of feeding behavior and digestive physiology, and support the hypothesis that diurnal changes in feeding-related genes in the nervous and digestive systems are correlated with the initiation of abalone feeding behavior. Our findings also provide guidance for developing a suitable feeding strategy for, and improving the efficiency of, the production of abalone.

Hypomorphic expression of parathyroid Bmal1 disrupts the internal parathyroid circadian clock and increases parathyroid cell proliferation in response to uremia

The molecular circadian clock is an evolutionary adaptation to anticipate recurring changes in the environment and to coordinate variations in activity, metabolism and hormone secretion. Parathyroid hyperplasia in uremia is a significant clinical challenge. Here, we examined changes in the transcriptome of the murine parathyroid gland over 24 hours and found a rhythmic expression of parathyroid signature genes, such as Casr, Vdr, Fgfr1 and Gcm2. Overall, 1455 genes corresponding to 6.9% of all expressed genes had significant circadian rhythmicity. Biological pathway analysis indicated that the circadian clock system is essential for the regulation of parathyroid cell function. To study this, a novel mouse strain with parathyroid gland-specific knockdown of the core clock gene Bmal1 (PTHcre;Bmal1flox/flox) was created. Dampening of the parathyroid circadian clock rhythmicity was found in these knockdown mice, resulting in abrogated rhythmicity of regulators of parathyroid cell proliferation such as Sp1, Mafb, Gcm2 and Gata3, indicating circadian clock regulation of these genes. Furthermore, the knockdown resulted in downregulation of genes involved in mitochondrial function and synthesis of ATP. When superimposed by uremia, these PTHcre;Bmal1flox/flox mice had an increased parathyroid cell proliferative response, compared to wild type mice. Thus, our findings indicate a role of the internal parathyroid circadian clock in the development of parathyroid gland hyperplasia in uremia.

Twenty-four-hour and nocturnal ambulatory blood pressure variability patterns in diabetics and hypothyroid patients: Looking through different temporal windows

ABSTRACT This cross-sectional study attempted to determine the 24-h blood pressure variability (BPV) and nocturnal dipping, through designated temporal windows in diabetic and hypothyroid patients. BPV profiles were examined in the cohorts of 26 diabetics and 27 hypothyroid patients on their prescribed medications. Fifty-seven (57) healthy normotensive subjects were treated as controls. We recorded blood pressure (BP)parameters in each subject over at least two to three consecutive days, using an ambulatory blood pressure monitor (ABPM). We analyzed the data employing A&D software, Cosinor rhythmometry, and SPSS software. Most of the patients displayed a statistically significant circadian rhythm with prominent periodsat 24 h and/or 12 h. The hourly-averaged data in patients exceeded the normal range of BP during the early morning and late afternoon. BP parameters in studied patients were significantly higher than in the controls. The results depicted significant and independent effects of “temporal window” and “disease” on the nocturnal BP profile. Higher BPV and bouts of nocturnal hypotension in diabetic and hypothyroid patients indicate poor BP management. The diagnosis of BP and efficacy of treatment in diabetic and hypothyroid patients could be detected proficiently by ambulatory BP monitoring. Temporal window analysis could be beneficial for tracing nocturnal dipping precisely.

Proof-of-principle demonstration of endogenous circadian system and circadian misalignment effects on human oral microbiota.

Circadian misalignment-the misalignment between the central circadian "clock" and behavioral and environmental cycles (including sleep/wake, fasting/eating, dark/light)-results in adverse cardiovascular and metabolic effects. Potential underlying mechanisms for these adverse effects include alterations in the orogastrointestinal microbiota. However, it remains unknown whether human oral microbiota has endogenous circadian rhythms (i.e., independent of sleep/wake, fasting/eating, and dark/light cycles) and whether circadian misalignment influences oral microbiota community composition. Healthy young individuals [27.3±2.3years (18-35years), 4 men and 2 women, body-mass index range: 18-28kg/m2 ] were enrolled in a stringently controlled 14-day circadian laboratory protocol. This included a 32-h constant routine (CR) protocol (endogenous circadian baseline assessment), a forced desynchrony protocol with four 28-h "days" under ~3lx to induce circadian misalignment, and a post-misalignment 40-h CR protocol. Microbiota assessments were performed on saliva samples collected every 4h throughout both CR protocols. Total DNA was extracted and processed using high-throughput 16S ribosomal RNA gene amplicon sequencing. The relative abundance of specific oral microbiota populations, i.e., one of the five dominant phyla, and three of the fourteen dominant genera, exhibited significant endogenous circadian rhythms. Importantly, circadian misalignment dramatically altered the oral microbiota landscape, such that four of the five dominant phyla and eight of the fourteen dominant genera exhibited significant circadian misalignment effects. Moreover, circadian misalignment significantly affected the metagenome functional content of oral microbiota (inferred gene content analysis), as indicated by changes in specific functional pathways associated with metabolic control and immunity. Collectively, our proof-of-concept study provides evidence for endogenous circadian rhythms in human oral microbiota and show that even relatively short-term experimental circadian misalignment can dramatically affect microbiota community composition and functional pathways involved in metabolism and immune function. These proof-of-principle findings have translational relevance to individuals typically exposed to circadian misalignment, including night shift workers and frequent flyers.

Relationship between physical activity, objective sleep parameters, and circadian rhythm in patients with head and neck cancer receiving chemoradiotherapy: A longitudinal study.

ObjectivesThis study was developed to assess the relationship between physical activity, sleep and circadian rhythm using accelerometer and urine melatonin levels in patients with head and neck cancer (HNC). Also, this study evaluated the changes in physical activity, sleep, and circadian rhythm during the seven‐week course of chemoradiotherapy.MethodsThis longitudinal study recruited 27 participants diagnosed with HNC who were planning to undergo chemoradiotherapy. Accelerometers worn for 3 days during the 1st, 3rd, and 7th weeks of chemoradiotherapy were used to assess physical activity levels (step count and metabolic equivalents [METs]) and sleep quality (total sleep time [TST], sleep onset latency [SOL], and sleep efficiency [SE]). Urine melatonin analysis was conducted using the morning void urine sample on 1st, 3rd, and 7th weeks. The change in variables during the seven weeks and the correlation between them were analyzed.ResultsDuring the seven weeks, trends of reduction in variables of physical activity, sleep and circadian rhythm were observed with significant decrease in step count, TST and melatonin levels. SE was found to have strong negative correlation with physical activity. TST was found to have moderate correlation with SE and step count. The variables of physical activity also showed moderate correlation among them.ConclusionThis study concludes that higher physical activity is associated with poor SE due to increased night‐time activity. There was a significant reduction in physical activity and sleep observed during seven weeks with moderate association between them. The significant circadian rhythm deregulation however showed poor association with the other variables.Level of Evidence: 2b

Physiological circadian rhythm of cardiac myosin-binding protein C (cMyC) and cardiac troponin

Abstract Introduction Cardiac myosin-binding protein C (cMyC) is a novel protein biomarker of myocardial injury, with a promising role in the triage and risk stratification of patients with cardiac disease. Understanding the physiological diurnal oscillation of cMyC and cardiac troponin is important for the interpretation of single and serial measurements within the biomarker-assisted triage and risk stratification algorithms. Purpose In this study, we aim to assess and compare the physiological diurnal oscillation of cMyC and cardiac troponin cTnT and cTnI. Method Twenty-six consecutive hourly blood samples were drawn between 08.30 am and 09.30 am (+1 day) from normotensive 24 individuals without a recent history of acute myocardial infarction, for the measurement of cMyC, cardiac troponin T (Roche hs-cTnT) and I (Abbott hs-cTnI). Fitted cosinor sine regression model (with R, version 3.6.1) was used to assess the presence and significance of circadian oscillation of the biomarker, and to estimate the respective amplitude and acrophase (the time of peak activity). Amplitude and acrophase were compared across the biomarkers that exhibited significant circadian rhythm. Results Mean age was 72±7. 79% of participants (n=19) were men. All participants were free from renal disease. On population-mean cosinor analysis, hs-cTnI exhibited random diurnal oscillation, whereas significant circadian rhythm was detected for cMyC and hs-cTnT (p=0.015 and <0.001, respectively) (Figure 1). The circadian rhythm of cMyC is characterised by gradually increasing concentrations from early afternoon until early morning (acrophase 03:03 am, 95% CI 01:54–04:26 am) compared to hs-cTnT concentrations which exhibits delayed increase and a later peak (acrophase, 08:01, 95% CI 07:10–08:51 am), p=0.028 for acrophase difference (Figure 1). Diurnal rhythm remained significant after correction for possible posture-induced changes in plasma volume. To allow direct comparison between amplitudes, the measurements of cMyC and hs-TnT were normalised to the respective 08:30 am value, re-fitted cosinor model did not show significant difference between the amplitudes (amplitude ng/L, 0.12, 95% CI 0.07–0.15 vs 0.11, 95% CI 0.08–0.12, for normalised cMyC vs hs-cTnT, respectively; p=0.67). Conclusion Significant circadian rhythm exists for cMyC and hs-cTnT, with 5-hours phase difference between the two biomarkers (cMyC ahead of hs-cTnT). The cause of this rhythmic variation is unknown, but the phase difference is consistent with the previously described disparity in the release of cMyC and cTnT after iatrogenic myocardial injury, raising the possibility of an underlying diurnal variation in myocardial vulnerability. Studies are required to assess the impact of this physiological phenomenon on the performance of the biomarkers within unadjused diagnostic algorithms Funding Acknowledgement Type of funding sources: Foundation. Main funding source(s): British Heart FoundationStichting de Weijerhorst

Comparative Study of the Feeding Characteristics and Digestion Physiology of Haliotis discus hannai and Haliotis gigantea

Abalone (Haliotis spp.) are typical nocturnal creatures but Haliotis discus hannai is bold and active in the nighttime whereas H. gigantea tends to be timid and inactive. In this study, we quantified and compared differences in movement, feeding, and digestive physiology between H. discus hannai and H. gigantea as well as the potential molecular mechanisms on the basis of video observations and expression levels of genes related to feeding regulation. The feeding behaviors of both species were characterized by significant circadian rhythms (P < 0.05). However, the distance moved and the cumulative duration of movement were 2.61 and 1.94 times higher, respectively, in H. discus hannai than in H. gigantea over the 24-h cycle. The cumulative duration of feeding by H. discus hannai was only 1.15 times that by H. gigantea, but the feeding time as a percentage of the cumulative duration of movement (FTP) was up to 94.6% for H. gigantea and only 56.0% for H. discus hannai. The peaks for α-amylase activity and NPF expression levels in both species as well as the peak OX2R expression level in H. gigantea occurred during 20:00–00:00 h. By contrast, the peaks for alginate lyase activity and NPYR expression levels in H. discus hannai occurred at 16:00 h, when the FTP was significantly higher for H. discus hannai than for H. gigantea. These initial findings quantify specific behavior parameters and thus provide a reference for the selection of appropriate feeding strategies and the proliferation of abalone via bottom sowing.

Heterogenous electrophysiological responses of functionally distinct striatal subregions to circadian and sleep-related homeostatic processes.

Basal ganglia (BG) are a set of subcortical nuclei that are involved in the control of a wide variety of motor, cognitive, and affective behaviors. Although many behavioral abnormalities associated with BG dysfunction overlap with the clinical picture precipitated by the lack of sleep, the impact of sleep alterations on neuronal activity in BG is unknown. Using wild-type C57BI mice, we investigated the circadian and sleep-related homeostatic modulation of neuronal activity in the three functional subdivisions of the striatum (i.e. sensorimotor, associative, and limbic striatum). We found no circadian modulation of activity in both ventral and dorsomedial striatum while the dorsolateral striatum displayed a significant circadian rhythm with increased firing rates during the subjective dark, active phase. By combining neuronal activity recordings with electroencephalogram (EEG) recordings, we found a strong modulation of neuronal activity by the nature of vigilance states with increased activity during wakefulness and rapid eye movement sleep relative to nonrapid eye movement sleep in all striatal subregions. Depriving animals of sleep for 6 h induced significant, but heterogenous alterations in the neuronal activity across striatal subregions. Notably, these alterations lasted for up to 48 h in the sensorimotor striatum and persisted even after the normalization of cortical EEG power densities. Our results show that vigilance and sleep states as well as their disturbances significantly affect neuronal activity within the striatum. We propose that these changes in neuronal activity underlie both the well-established links between sleep alterations and several disorders involving BG dysfunction as well as the maladaptive changes in behavior induced in healthy participants following sleep loss.

The endogenous circadian system worsens asthma at night independent of sleep and other daily behavioral or environmental cycles

Asthma often worsens at night. To determine if the endogenous circadian system contributes to the nocturnal worsening of asthma, independent of sleep and other behavioral and environmental day/night cycles, we studied patients with asthma (without steroid use) over 3 wk in an ambulatory setting (with combined circadian, environmental, and behavioral effects) and across the circadian cycle in two complementary laboratory protocols performed in dim light, which separated circadian from environmental and behavioral effects: 1) a 38-h "constant routine," with continuous wakefulness, constant posture, 2-hourly isocaloric snacks, and 2) a 196-h "forced desynchrony" incorporating seven identical recurring 28-h sleep/wake cycles with all behaviors evenly scheduled across the circadian cycle. Indices of pulmonary function varied across the day in the ambulatory setting, and both laboratory protocols revealed significant circadian rhythms, with lowest function during the biological night, around 4:00 AM, uncovering a nocturnal exacerbation of asthma usually unnoticed or hidden by the presence of sleep. We also discovered a circadian rhythm in symptom-based rescue bronchodilator use (β2-adrenergic agonist inhaler) whereby inhaler use was four times more likely during the circadian night than day. There were additive influences on asthma from the circadian system plus sleep and other behavioral or environmental effects. Individuals with the lowest average pulmonary function tended to have the largest daily circadian variations and the largest behavioral cycle effects on asthma. When sleep was modeled to occur at night, the summed circadian, behavioral/environmental cycle effects almost perfectly matched the ambulatory data. Thus, the circadian system contributes to the common nocturnal worsening of asthma, implying that internal biological time should be considered for optimal therapy.

Особливості добового профілю артеріального тиску у хворих на цукровий діабет залежно від ендотеліальної дисфункції

Актуальність. Цукровий діабет (ЦД) — захворювання, що супроводжується оксидативним стресом, хронічним неспецифічним запаленням, пошкодженням судинної стінки, ендотеліальною дисфункцією. Особливістю перебігу артеріальної гіпертензії у хворих на ЦД є більш раннє формування діабетичної хвороби нирок (ДХН). Сьогодні здійснюється пошук маркерів ендотеліальної дисфункції, що дозволять виявляти ДХН на ранніх стадіях, коли зміни в нирках потенційно оборотні. Метою роботи було дослідити показники добового профілю артеріального тиску у хворих на ЦД та визначити їх взаємозв’язки з показниками швидкості клубочкової фільтрації й ендотеліальної функції за рівнем показників TGF-β1 (transforming growth factor beta-1 — трансформуючий фактор росту бета-1) та VCAM-1 (vascular cell adhesion molecule 1 — васкулярна молекула судинної адгезії 1). Матеріали та методи. У дослідження включені 124 хворі на ЦД, із них 66 пацієнтів із ЦД 1-го типу, 58 — із ЦД 2-го типу. Результати. Рівні показників ендотеліальної функції TGF-β1 та VCAM-1 у хворих на ЦД 1-го та 2-го типів кількісно залежали від показника швидкості клубочкової фільтрації. Між показниками ендотеліальної функції TGF-β1, VCAM-1 та показниками добового моніторування артеріального тиску виявлені сильні та середньої сили кореляційні зв’язки, у зв’язку з чим комплекс показників добового моніторування артеріального тиску та наявність ендотеліальної дисфункції можна вважати ранніми ознаками прогресування ДХН. Висновки. Для добового профілю артеріального тиску у хворих на ЦД на ранніх стадіях діабетичної нефропатії характерне вірогідне порушення циркадних ритмів. Недостатнє нічне зниження артеріального тиску у хворих на ЦД 1-го та 2-го типу характеризує наявність прогресування діабетичної нефропатії за показниками добового індексу артеріального тиску.

Circadian rhythm and time-of-day-effects of (anti)oxidant biomarkers for epidemiological studies

Various biomarkers of oxidative stress and redox status have been used in a number of clinical and epidemiological studies related to diseases and conditions that involve disturbances of the redox balance. However, a comprehensive study of diurnal variations of a set of biomarkers has not been conducted so far. Therefore, the aim of this study is to investigate circadian rhythm and time-of-day-effects of a set of frequently used biomarkers of oxidative stress, redox and antioxidant status in serum/plasma. These biomarkers include Reactive Oxygen Metabolites (ROM), Biological Antioxidant Potency (BAP), Total Thiols in Proteins (TTP), high-sensitive C-Reactive Protein (CRP) and Uric Acid (UA). During a 24-hr study, blood sampling was conducted 6 times at 4-hr intervals. The presence of circadian rhythm was analyzed with CircWave analysis, whereas the effect of time was analyzed with Repeated Measures ANOVA (RM-ANOVA). Thereby, the main focus was on the time points in working hours (8, 12 and 16 hr), which are used frequently in practice. Of all investigated biomarkers, only TTP in males demonstrated statistically significant circadian rhythm (p = 0.040). A statistically significant effect between all six time points with RM-ANOVA was observed for ROM, TTP and UA in both genders, and for BAP in females only. No statistically significant differences were observed between the time points 8 hr and 12 hr for any of the biomarkers that were assessed in our study. In conclusion, diurnal variations in some of the studied biomarkers that we demonstrate here should be taken into account when designing and conducting clinical and epidemiological studies. It is advised to standardize the time of sampling with a preference in the morning hours.

Locomotor activity rhythm in catfish Heteropneustes fossilis as a function of shoal size under different light regimens

ABSTRACT The information on the circadian characteristics of catfish in shoals is scanty. We examined the circadian locomotor activity rhythm of catfish Heteropneustes fossilis either singly housed (SS1) or in shoals of four (SS4) and six (SS6) under different light regimens. We carried out the study sequentially under LD1 (12:12), constant darkness (DD), LD2, continuous light (LL), LD3, and DL (12:12). Each condition was for at least 10–12 consecutive days. We analyzed the time-series data by employing Cosinor rhythmometry to detect circadian rhythm characteristics in locomotor activity at a fixed time window with a τ = 24 h. Results indicated that singly housed or shoals exhibited statistically significant (p < .001) circadian rhythm in locomotor activity under LD conditions with a higher activity level during the dark phase. Further, we observed free-running rhythms in locomotor activity under DD and LL, irrespective of the shoal sizes. In phase inverse DL, both singly housed and shoals demonstrated higher activity in the dark phase. The two-way ANOVA results revealed a significant effect of the factor ‘light regimen’ on amplitude and acrophase; the factor ‘shoal size’ produced a statistically significant impact on the mesor only. Both shoals showed significantly higher mesor than singly housed fish. The circadian amplitude declined under constant conditions of DD and LL. The locomotor activity rhythm exhibited a free-running pattern with a τFR greater than 24 h under both DD and LL conditions. We conclude that light is a more prominent factor for the entrainment of circadian activity in catfish H. fossilis. However, the extent of social aggregation (shoal size) has little or no effects on the characteristics of circadian locomotor activity rhythm in H. fossilis.

Nighttime transpirational cooling enabled by circadian regulation of stomatal conductance is related to stomatal anatomy and leaf morphology in rice.

Rice genotypes with larger stomata maintain higher nocturnal stomatal conductance, thus having lower nocturnal leaf temperature via transpirational cooling. Incomplete night stomatal closure has been widely observed, but the mechanisms and functions of nocturnal stomatal conductance (gs,n) are not fully understood. Stomatal anatomy, leaf morphology, gs,n and nocturnal leaf temperature (Tleaf,n) were measured in 30 Oryza genotypes. Nocturnal leaf conductance (gn) showed a significant circadian rhythm; it gradually increased by 58% from 20:30 to 04:30. Contrary to cuticular conductance (gcut), gs,n was highly correlated with gn. Moreover, gs,n accounted for 76% of gn. Tleaf,n was significantly lower than the air temperature, and was negatively correlated with both gs,n and nocturnal transpiration rate (En). gs,n was positively correlated with stomatal size, intervein distance between major veins (IVDmajor), leaf thickness (LT), individual leaf area (LA), and leaf width (LW). It was also found negatively correlated with stomatal density. Reversely, Tleaf,n was negatively correlated with stomatal size, IVDmajor, intervein distance between minor veins, LA and LW. Tleaf,n presented a positive correlation with stomatal density. This study highlights the importance of stomatal anatomy and leaf morphology on regulating gs,n and Tleaf,n. The underlying mechanisms to the determinants of gs,n and the physiological and ecological functions of the Tleaf,n regulation on rice growth and production were carefully discussed.

Peripheral immune circadian variation, synchronisation and possible dysrhythmia in established type 1 diabetes

Aims/hypothesisThe circadian clock influences both diabetes and immunity. Our goal in this study was to characterise more thoroughly the circadian patterns of immune cell populations and cytokines that are particularly relevant to the immune pathology of type 1 diabetes and thus fill in a current gap in our understanding of this disease.MethodsTen individuals with established type 1 diabetes (mean disease duration 11 years, age 18–40 years, six female) participated in a circadian sampling protocol, each providing six blood samples over a 24 h period.ResultsDaily ranges of population frequencies were sometimes large and possibly clinically significant. Several immune populations, such as dendritic cells, CD4 and CD8 T cells and their effector memory subpopulations, CD4 regulatory T cells, B cells and cytokine IL-6, exhibited statistically significant circadian rhythmicity. In a comparison with historical healthy control individuals, but using shipped samples, we observed that participants with type 1 diabetes had statistically significant phase shifts occurring in the time of peak occurrence of B cells (+4.8 h), CD4 and CD8 T cells (~ +5 h) and their naive and effector memory subsets (~ +3.3 to +4.5 h), and regulatory T cells (+4.1 h). An independent streptozotocin murine experiment confirmed the phase shifting of CD8 T cells and suggests that circadian dysrhythmia in type 1 diabetes might be an effect and not a cause of the disease.Conclusions/interpretationFuture efforts investigating this newly described aspect of type 1 diabetes in human participants are warranted. Peripheral immune populations should be measured near the same time of day in order to reduce circadian-related variation.Graphical abstract

Locomotor activity rhythm of catfish Heteropneustes fossilis are prominently regulated by light-dark cues

It is interesting to explore, the circadian locomotor activity rhythm of dark adapted fishes. Therefore, it is aimed to investigate the circadian locomotor activity rhythm of catfish, Heteropneustes fossilis under different light regi-mens- light-dark condition LD 12:12, constant dark condition DD, constant light LL and dark-light condition DL 12:12 in both male and female. The study was conducted sequentially under LD 12: 12 (LON 0500 and LOFF 1700) and thereafter under the DD, LL and DL each for at least 10-12 consecutive days. The locomotor activity was monitored using Stanford Chronobiology Kit at a fixed period of 24 h. The three rhythm parameters obtained were Mesor (M, rhythm-adjusted 24-h average), amplitude (A) and acrophase (peak, Ø). All fish exhibited a statistically significant (p&lt;0.001) circadian rhythm in locomo-tor activity under all light regimens LD, DD, LL and DL. The circadian ampli-tude was significantly declined under constant DD and LL. A significant shift was displayed in the circadian acrophase in all fish under each photic re-gimes LD, DD, LL and DL. The effect of light condition on M, A and Ø was sig-nificant, while gender imposed no effect. Chi-square periodogram revealed τ &gt; 24 h in locomotor activity of most of the replicates under DD and LL. The respective study suggests that the endogenous circadian clocks in catfish H.fossilis are weakly expressed under constant conditions and requires light-dark LD or dark- light DL cues to generate/express the circadian rhythm in locomotor activity.

Cosinor-rhythmometry for 24-h urinary sodium, potassium, creatinine excretion in the Chinese adult population.

Background:The low accuracy of equations predicting 24-h urinary sodium excretion using a single spot urine sample contributed to the misclassification of individual sodium intake levels. The application of single spot urine sample is limited by a lack of representativity of urinary sodium excretion, possibly due to the circadian rhythm in urinary excretion. This study aimed to explore the circadian rhythm, characteristics, and parameters in a healthy young adult Chinese population as a theoretical foundation for developing new approaches.Methods:Eighty-five participants (mean age 32.4 years) completed the 24-h urine collection by successively collecting each of the single-voided specimens within 24 h. The concentrations of the urinary sodium, potassium, and creatinine for each voided specimen were measured. Cosinor analysis was applied to explore the circadian rhythm of the urinary sodium, potassium, and creatinine excretion. The excretion per hour was computed for analyzing the change over time with repeated-measures analysis of variance and a cubic spline model.Results:The metabolism of urinary sodium, potassium, and creatinine showed different patterns of circadian rhythm, although the urinary sodium excretion showed non-significant parameters in the cosinor model. A significant circadian rhythm of urinary creatinine excretion was observed, while the circadian rhythm of sodium was less significant than that of potassium. The circadian rhythm of urinary sodium and creatinine excretion showed synchronization to some extent, which had a nocturnal peak and fell to the lowest around noon to afternoon. In contrast, the peak of potassium was observed in the morning and dropped to the lowest point in the evening. The hourly urinary excretion followed a similar circadian rhythm.Conclusion:It is necessary to consider the circadian rhythm of urinary sodium, potassium, and creatinine excretion in adults while exploring the estimation model for 24-h urinary sodium excretion using spot urine.

Chronotoxicity of Semen Strychni is associated with circadian metabolism and transport in mice.

We aimed to determine the circadian responses of mice to Semen Strychni and to investigate the role of pharmacokinetics in generating chronotoxicity. Total extract of Semen Strychni was administered by oral gavage to wild-type (WT) and Bmal1-/- (a circadian clock-deficient model) mice at different circadian time points for toxicity (including survival) and pharmacokinetic characterization. Nephrotoxicity and neurotoxicity were evaluated by measuring plasma creatinine and creatine kinase BB (CK-BB), respectively. Drug metabolism and transport assays were performed using liver/intestine microsomes and everted gut sacs, respectively. Semen Strychni nephrotoxicity and neurotoxicity as well as animal survival displayed significant circadian rhythms (the highest level of toxicity was observed at ZT18 and the lowest level at ZT2 to ZT6). According to pharmacokinetic experiments, herb dosing at ZT18 generated higher plasma concentrations (and systemic exposure) of strychnine and brucine (two toxic constituents) compared with ZT6 dosing. This was accompanied by reduced formation of both dihydroxystrychnine and strychnine glucuronide (two strychnine metabolites) at ZT18. Bmal1 ablation sensitized mice to Semen Strychni-induced toxicity (with increased levels of plasma creatinine and CK-BB) and abolished the time dependency of toxicity. Metabolism of Semen Strychni (strychnine and brucine) in the liver and intestine microsomes of WT mice was more extensive at ZT6 than at ZT18. These time differences in hepatic and intestinal metabolism were lost in Bmal1-/- mice. Additionally, the intestinal efflux transport of Semen Strychni (strychnine and brucine) was more extensive at ZT6 than ZT18 in WT mice. However, the time-varying transport difference was abolished in Bmal1-/- mice. Circadian responses of mice to Semen Strychni are associated with time-varying efflux transport and metabolism regulated by the circadian clock (Bmal1). Our findings may have implications for optimizing phytotherapy with Semen Strychni via timed delivery.