Phase Shifts Of Circadian Rhythms Research Articles

Protective role of melatonin against radiation-induced disruptions in behavior rhythm of zebrafish (danio rerio)

Ionizing radiation, as an increasingly serious environmental pollutant, has aroused widespread public concern. Melatonin, as an indole heterocyclic compound, is known to have anti-inflammatory and antioxidant effects. However, few studies have considered the comprehensive impact of melatonin on radiation damage. In this study, we used zebrafish as experimental materials and employed methods such as acridine orange staining, enzyme-linked immunosorbent assay (ELISA), video tracking for automated behavior analysis, microscope imaging, and real-time fluorescence quantitative analysis. Zebrafish embryos at 2 h post-fertilization (hpf) were treated under four different experimental conditions to assess their growth, development, and metabolic consequences. Our findings indicate that 0.10 Gy gamma radiation significantly augments body length, eye area, spine width, and tail fin length in zebrafish, along with a marked increase in oxidative stress (P < 0.05). Moreover, it enhances cumulative swimming distance, time, and average speed, suggesting elevated activity levels. We observed circadian rhythm phase shifts, peak increases, and cycle shortening, accompanied by abnormal expression of genes pivotal to biological rhythms, exercise, melatonin synthesis, apoptosis/anti-apoptosis, and oxidation/antioxidant balance. The inclusion of melatonin (1 × 10-5 mol/L MLT) ameliorated these radiation-induced anomalies, while its independent effect on zebrafish was negligible. Melatonin can regulate oxidative stress responses, hinders apoptosis responses, and reprogramming the expression of rhythm-related genes in zebrafish embryos after reprogramming radiation stimulation. Overall, our research highlights melatonin's critical role in countering the biological damage inflicted by gamma radiation, proposing its potential as a therapeutic agent in radiation protection.

Investigation of the effect of circadian rhythm on the performances of NBA teams

ABSTRACT Professional athletes competing in the NBA are frequently exposed to time-zone-shifting travels. These time zone changes may cause circadian rhythm (CR) phase shifts and these shifts affect sportive performance. The aim of this study was to investigate the effects of CR phase shifts on the performance of NBA teams. 25016 regular season games across 21 consecutive seasons were included in the CR phase shift calculations. To examine the CR phase shift effect on team performance, teams were divided into three groups regarding Coordinated Universal Time (UTC): the same internal UTC as the local UTC (LS); the internal UTC ahead of the local UTC (LA); and the internal UTC behind the local UTC (LB). With a different approach, teams were divided into another three categories: the same internal UTC as its opponent’s internal UTC (OS); the internal UTC ahead of its opponent’s internal UTC (OA); and the internal UTC behind its opponent’s internal UTC (OB). 24985 game data were used to compare these groups in terms of 25 variables. Statistical analyses were conducted separately for home and away teams. For home games, it was found that LA and OA are the most and LB is the least successful group in winning and scoring performances. For away games, it was determined that LS is the most advantageous group with the best winning percentage. These results revealed that teams from more west may have a CR advantage in regular season home games. However, it is thought that the performance of away teams depends more on travel fatigue than CR phase shifts.

Effects of volatile anesthetics on circadian rhythm in mice: a comparative study of sevoflurane, desflurane, and isoflurane.

Volatile anesthetics affect the circadian rhythm of mammals, although the effects of different types of anesthetics are unclear. Here, we anesthetized mice using several volatile anesthetics at two different times during the day. Our objective was to compare the effects of these anesthetics on circadian rhythm. Male adult C57BL/6J mice were divided into eight groups (n = 8 each) based on the anesthetic (sevoflurane, desflurane, isoflurane, or no anesthesia) and anesthesia time (Zeitgeber time [ZT] 6-12 or ZT18-24). Mice were anesthetized for 6h using a 0.5 minimum alveolar concentration (MAC) dose under constant dark conditions. The difference between the start of the active phase before and after anesthesia was measured as a phase shift. Clock genes were measured by polymerase chain reaction in suprachiasmatic nucleus (SCN) samples removed from mouse brain after anesthesia (n = 8-9 each). Phase shift after anesthesia at ZT6-12 using sevoflurane (- 0.49h) was smaller compared with desflurane (- 1.1h) and isoflurane (- 1.4h) (p < 0.05). Clock mRNA (ZT6-12, p < 0.05) and Per2 mRNA (ZT18-24, p < 0.05) expression were different between the groups after anesthesia. 0.5 MAC sevoflurane anesthesia administered during the late inactive to early active phase has less impact on the phase shift of circadian rhythm than desflurane and isoflurane. This may be due to differences in the effects of volatile anesthetics on the expression of clock genes in the SCN, the master clock of the circadian rhythm.

The regulation of circadian entrainment in mice by the adenosine the A 2A /A 1 receptor antagonist CT1500.

Circadian entrainment in mice relies primarily on photic cues that trigger the transcription of the core clock genes Period1/2 in the suprachiasmatic nucleus (SCN), thus aligning the phase of the clock with the dawn/dusk cycle. It has been shown previously that this pathway is directly regulated by adenosine signalling and that adenosine A2A/A1 receptor antagonists can both enhance photic entrainment and phase shift circadian rhythms of wheel-running behaviour in mice. In this study, we tested the ability of CT1500, a clinically safe adenosine A2A/A1 receptor antagonist to effect circadian entrainment. We show that CT1500 lengthens circadian period in SCN ex vivo preparations. Furthermore, we show in vivo that a single dose of CT1500 enhances re-entrainment to a shifted light dark cycle in a dose-dependent manner in mice and also phase shifts the circadian clock under constant dark with a clear time-of-day related pattern. The phase response curve shows CT1500 causes phase advances during the day and phase delays at dusk. Finally, we show that daily timed administration of CT1500 can entrain the circadian clock to a 24h rhythm in free-running mice. Collectively, these data support the use of CT1500 in the treatment of disorders of circadian entrainment.

A light-induced small G-protein gem limits the circadian clock phase-shift magnitude by inhibiting voltage-dependent calcium channels.

Calcium signaling is pivotal to the circadian clockwork in the suprachiasmatic nucleus (SCN), particularly in rhythm entrainment to environmental light-dark cycles. Here, we show that a small G-protein Gem, an endogenous inhibitor of high-voltage-activated voltage-dependent calcium channels (VDCCs), is rapidly induced by light in SCN neurons via the calcium (Ca2+)-mediated CREB/CRE transcriptional pathway. Gem attenuates light-induced calcium signaling through its interaction with VDCCs. The phase-shift magnitude of locomotor activity rhythms by light, at night, increases in Gem-deficient (Gem-/-) mice. Similarly, in SCN slices from Gem-/- mice, depolarizing stimuli induce larger phase shifts of clock gene transcription rhythms that are normalized by the application of an L-type VDCC blocker, nifedipine. Voltage-clamp recordings from SCN neurons reveal that Ca2+ currents through L-type channels increase in Gem-/- mice. Our findings suggest that transcriptionally activated Gem feeds back to suppress excessive light-evoked L-type VDCC activation, adjusting the light-induced phase-shift magnitude to an appropriate level in mammals.

Methods to Assess Melatonin Receptor-Mediated Phase-Shift and Re-entrainment of Rhythmic Behaviors in Mouse Models.

The neurohormone melatonin facilitates entrainment of biological rhythms to environmental light-dark conditions as well as phase-shifts of circadian rhythms in constant conditions via activation of the MT1 and/or MT2 receptors expressed within the suprachiasmatic nucleus of the hypothalamus. The efficacy of melatonin and related agonists to modulate biological rhythms can be assessed using two well-validated mouse models of rhythmic behaviors. These models serve as predictive measures of therapeutic efficacy for treatment of circadian phase disorders caused by internal (e.g., clock gene mutations, blindness, depression, seasonal affective disorder) or external (e.g., shift work, travel across time zones) causes in humans. Here we provide background and detailed protocols for quantitative assessment of the magnitude and efficacy of melatonin receptor ligands inmouse circadian phase-shift and re-entrainment paradigms. The utility of these models in the discovery of novel therapeutics acting on melatonin receptors will also be discussed.

Aging disrupts the temporal organization of antioxidant defenses in theheart of male ratsand phase shifts circadian rhythms of systolic blood pressure.

Aging is one of the main risk factors for cardiovascular diseases, and oxidative stress is a key element responsible for the development of age-related pathologies. In addition, the alteration of circadian rhythms also contributes to cardiovascular pathology, but the underlying mechanisms are not well defined. We investigated the aging consequences on the temporal patterns of antioxidant defenses, the molecular clock machinery, and the blood pressure, in the heart of male rats maintained under constant darkness (free running) conditions. Male Holtzman rats from young adult (3-month-old) and older (22-month-old) groups were maintained under constant darkness (12-h dark:12-h dark, DD) condition during fifteen days before the experiment. After the DD period, heart ventricle samples were isolated every 4-h throughout a 24-h period. We observed circadian rhythms of catalase (CAT) and glutathione peroxidase (GPx) mRNA expression, as well as ultradian rhythms of Nrf2 mRNA levels, in the heart of young adult rats. We also found circadian oscillations of CAT and GPx enzymatic activities, reduced glutathione (GSH) and BMAL1 protein in the same group. Interestingly, aging abolished the rhythms of CAT and GPx enzymatic activities, phase-shifted the rhythm's acrophases of GSH and BMAL1 protein levels and turned circadian the ultradian oscillation of Nrf2 expression. Moreover, aging phase-shifted the circadian pattern of systolic blood pressure. In conclusion, aging modifies the temporal organization of antioxidant defenses and blood pressure, probably, as a consequence of a disruption in the circadian rhythm of the clock's transcriptional regulator, BMAL1, in heart.

Desflurane anesthesia shifts the circadian rhythm phase depending on the time of day of anesthesia

Desflurane is one of the most frequently used inhalational anesthetics in clinical practice. A circadian rhythm phase-shift after general anesthesia with sevoflurane or isoflurane has been reported in mice, but few studies have reported this effect with desflurane. In the present study, we examined the rest/activity rhythm of mice by counting the number of running wheel rotations, and we found that desflurane anesthesia caused a phase shift in the circadian rhythm that was dependent on the time of day of anesthesia. We also found that desflurane anesthesia altered the relative mRNA expression of four major clock genes (Per2, Bmal, Clock, and Cry1) in the suprachiasmatic nucleus (SCN). These results are important for elucidating the effects of desflurane on the SCN, which is the master clock for the mammalian circadian rhythm. Further studies on the relationship between anesthesia and circadian rhythm may lead to the prevention and treatment of postoperative complications related to circadian rhythms.

Circadian rhythm phase shifts caused by timed exercise vary with chronotype.

BACKGROUNDThe circadian system entrains behavioral and physiological rhythms to environmental cycles, and modern lifestyles disrupt this entrainment. We investigated a timed exercise intervention to phase shift the internal circadian rhythm.METHODSIn 52 young, sedentary adults, dim light melatonin onset (DLMO) was measured before and after 5 days of morning (10 hours after DLMO; n = 26) or evening (20 hours after DLMO; n = 26) exercise. Phase shifts were calculated as the difference in DLMO before and after exercise.RESULTSMorning exercise induced phase advance shifts (0.62 ± 0.18 hours) that were significantly greater than phase shifts from evening exercise (-0.02 ± 0.18 hours; P = 0.01). Chronotype also influenced the effect of timed exercise. For later chronotypes, both morning and evening exercise induced phase advances (0.54 ± 0.29 hours and 0.46 ±0.25 hours, respectively). In contrast, earlier chronotypes had phase advances from morning exercise (0.49 ± 0.25 hours) but had phase delays from evening exercise (-0.41 ± 0.29 hours).CONCLUSIONLate chronotypes - those who experience the most severe circadian misalignment - may benefit from phase advances induced by exercise in the morning or evening, but evening exercise may exacerbate circadian misalignment in early chronotypes. Thus, personalized exercise timing prescription, based on chronotype, could alleviate circadian misalignment in young adults.TRIAL REGISTRATIONTrial registration can be found at www.clinicaltrials.gov (NCT04097886).FUNDINGFunding was supplied by NIH grants UL1TR001998 and TL1TR001997, the Barnstable Brown Diabetes and Obesity Center, the Pediatric Exercise Physiology Laboratory Endowment, the Arvle and Ellen Turner Thacker Research Fund, and the University of Kentucky.

Circadian Misalignment and Bipolar Disorder

The circadian rhythm is a periodic and continuous change caused by the light/dark cycle as the Earth rotates around its own axis in a 24- hour cycle. The circadian clock system regulates the 24-hour daily rhythms of human physiology and behavior such as the sleep/wake cycle, body temperature, hormone secretion, and mood. The influence of circadian rhythm on the body and mind is obvious, but considerable research has not dealt with its effects on human disease, especially on mental illnesses. However, several recent studies have shown that circadian misalignment may play an important role in the pathogenesis of bipolar disorder. Evidence for circadian rhythm misalignment in bipolar disorder suggests that circadian rhythm phase shift is a key pathophysiologic mechanism. Keywords: Circadian rhythm; Bipolar disorder; Pathogenesis

Light- and temperature-entrainable circadian clock in soybean development.

In plants, the spatiotemporal expression of circadian oscillators provides adaptive advantages in diverse species. However, the molecular basis of circadian clock in soybean is not known. In this study, we used soybean hairy roots expression system to monitor endogenous circadian rhythms and the sensitivity of circadian clock to environmental stimuli. We discovered in experiments with constant light and temperature conditions that the promoters of clock genes GmLCLb2 and GmPRR9b1 drive a self-sustained, robust oscillation of about 24-h in soybean hairy roots. Moreover, we demonstrate that circadian clock is entrainable by ambient light/dark or temperature cycles. Specifically, we show that light and cold temperature pulses can induce phase shifts of circadian rhythm, and we found that the magnitude and direction of phase responses depends on the specific time of these two zeitgeber stimuli. We obtained a quadruple mutant lacking the soybean gene GmLCLa1, LCLa2, LCLb1, and LCLb2 using CRISPR, and found that loss-of-function of these four GmLCL orthologs leads to an extreme short-period circadian rhythm and late-flowering phenotype in transgenic soybean. Our study establishes that the morning-phased GmLCLs genes act constitutively to maintain circadian rhythmicity and demonstrates that their absence delays the transition from vegetative growth to reproductive development.

Functional D-box sequences reset the circadian clock and drive mRNA rhythms

The circadian clock drives gene expression rhythms, leading to daily changes in physiology and behavior. In mammals, Albumin D-site-Binding Protein (DBP) rhythmically activates transcription of various genes through a DNA cis-element, D-box. The DBP-dependent transactivation is repressed by competitive binding of E4BP4 to the D-box. Despite the elaborate regulation, physiological roles of the D-box in the circadian clockwork are still elusive. Here we identified 1490 genomic regions recognized commonly by DBP and E4BP4 in the mouse liver. We comprehensively defined functional D-box sequences using an improved bioinformatics method, MOCCS2. In RNA-Seq analysis of E4bp4-knockout and wild type liver, we showed the importance of E4BP4-mediated circadian repression in gene expression rhythms. In addition to the circadian control, we found that environmental stimuli caused acute induction of E4BP4 protein, evoking phase-dependent phase shifts of cellular circadian rhythms and resetting the clock. Collectively, D-box-mediated transcriptional regulation plays pivotal roles in input and output in the circadian clock system.

Carbaryl Modulates Chronobiological Behaviors via Melatonin Receptors

Humans are exposed to low levels of carbaryl and other carbamate insecticides found in household products, food, and water due to persistent and widespread use. Environmental and occupational exposure to carbamate pesticides is linked to metabolic disorders and sleep apnea, though it is not clear which biological targets contribute to disease pathology (Montgomery et al. 2008; James‐Todd et al., 2016; Baumert et al. 2017). Carbaryl binds to MT1 and MT2 G protein‐coupled receptors with varying efficacies and potencies as demonstrated by our team via in‐silico molecular modeling and in‐vitro bioassays (Popovska‐Gorevski et al. 2017; Jones et al. 2017 EB Abst; Glatfelter et al. 2017 EB Abst). We hypothesize that carbaryl may produce alterations in circadian rhythms through interactions with melatonin receptors that could contribute to the aforementioned disease symptomology, progression, and/or pathologies. Previous in‐vitro (1–100μM) and ex‐vivo (10 mg/kg, i.p.) experiments demonstrated specificity for competition of carbaryl for 2‐[125I]‐iodomelatonin binding to brain melatonin receptors and its ability to reach target brain areas controlling circadian rhythms in‐vivo (e.g. suprachiasmatic nucleus: SCN; Glatfelter et al. 2017 EB Abs). We tested the ability of carbaryl (10 mg/kg, i.p.) to phase shift onset of circadian running wheel activity when given at circadian time (CT) 10 (CT12 = onset of running wheel activity in constant dark) for 3 days in wild‐type C3H/HeN (C3H) mice. Our results indicate that carbaryl (0.81h ± 0.1; n=12; p&lt;0.0001) and positive control melatonin (3mg/kg s.c.; 0.97h ± 0.2; n=4; p&lt;0.001) significantly phase advance running wheel activity onset compared to vehicle (0.03h ± 0.04; n=7) treated controls (F2,20=18.46; p&lt;0.05; Dunnet's Post Test). In the same paradigm, carbaryl (10 mg/kg i.p.) given 10 hrs before onset of running wheel activity in constant dark at CT 2 showed a phase delay (−1.2h ± 0.11; n=14; p&lt;0.0001) similar to positive control melatonin (3mg/kg s.c. 1.3h ± 0.14; n=4; p&lt;0.001) compared to vehicle (−0.12h ± 0.02; n=19) treated controls (F2,34=75.96; p&lt;0.05; Dunnet's Post Test). These data demonstrate that carbaryl has the same periods of circadian sensitivity for phase shift at CT2 &amp; CT10 as melatonin (Benloucif &amp; Dubocovich 1996). A dose response curve for carbaryl (0.01 – 10 mg/kg i.p.) to phase advance circadian running wheel activity rhythms at CT10 reveals an ED50 value of 0.019 mg/kg, i.p. which is similar in magnitude to melatonin (ED50=0.024 mg/kg s.c. Dubocovich et al. 1998). Carbaryl (10 mg/kg i.p.) did not phase advance circadian running wheel activity rhythms in C3H MT1KO mice (−0.04h ± 0.04; n=18; n.s.) at CT10 compared to vehicle controls (−0.04h ± 0.03; n=19; t=0.12; n.s.) suggesting an MT1 dependent mechanism. We conclude that carbaryl phase shifts circadian activity rhythms via activation of MT1 melatonin receptors suggesting environmental or occupational exposure to this insecticide in the tested dose range could influence disease pathologies via modulation of circadian biology.Support or Funding InformationSupported by ES 023684 and UB Jacobs School of Medicine funds to MLD and RVR.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Human circadian phase-response curves for exercise.

Key points Exercise elicits circadian phase‐shifting effects, but additional information is needed.The phase–response curve describing the magnitude and direction of circadian rhythm phase shifts, depending on the time of the zeigeber (time cue) stimulus, is the most fundamental chronobiological tool for alleviating circadian misalignment and related morbidity.Fifty‐one older and 48 young adults followed a circadian rhythms measurement protocol for up to 5.5 days, and performed 1 h of moderate treadmill exercise for 3 consecutive days at one of eight times of the day/night.Temporal changes in the phase of 6‐sulphatoxymelatonin (aMT6s) were measured from evening onset, cosine acrophase, morning offset and duration of excretion. Significant phase–response curves were established for aMT6 onset and acrophase with large phase delays from 7:00 pm to 10:00 pm and large phase advances at both 7:00 am and from 1:00 pm to 4:00 pm. Delays or advances would be desired, for example, for adjustment to westward or eastward air travel, respectively.Along with known synergism with bright light, the above PRCs with a second phase advance region (afternoon) could support both practical and clinical applications. Although bright light is regarded as the primary circadian zeitgeber, its limitations support exploring alternative zeitgebers. Exercise elicits significant circadian phase‐shifting effects, but fundamental information regarding these effects is needed. The primary aim of the present study was to establish phase–response curves (PRCs) documenting the size and direction of phase shifts in relation to the circadian time of exercise. Aerobically fit older (n = 51; 59–75 years) and young adults (n = 48; 18–30 years) followed a 90 min laboratory ultrashort sleep–wake cycle (60 min wake/30 min sleep) for up to 5½ days. At the same clock time on three consecutive days, each participant performed 60 min of moderate treadmill exercise (65–75% of heart rate reserve) at one of eight times of day/night. To describe PRCs, phase shifts were measured for the cosine‐fitted acrophase of urinary 6‐sulphatoxymelatonin (aMT6s), as well as for the evening rise, morning decline and change in duration of aMT6s excretion. Significant PRCs were found for aMT6s acrophase, onset and duration, with peak phase advances corresponding to clock times of 7:00 am and from 1:00 pm to 4:00 pm, delays from 7:00 pm to 10:00 pm, and minimal shifts around 4:00 pm and 2:00 am. There were no significant age or sex differences. The amplitudes of the aMT6s onset and acrophase PRCs are comparable to expectations for bright light of equal duration. The phase advance to afternoon exercise and the exercise‐induced PRC for change in aMT6s duration are novel findings. The results support further research exploring additive phase‐shifting effects of bright light and exercise and health benefits.

Impact of seasons on an individual's chronotype: current perspectives.

Diurnal preference, or chronotype, determined partly by genetics and modified by age, activity, and the environment, defines the time of day at which one feels at his/her best, when one feels sleepy, and when one would prefer to start his/her day. Chronotype affects the phase relationship of an individual’s circadian clock with the environment such that morning types have earlier-phased circadian rhythms than evening types. The phases of circadian rhythms are synchronized to the environment on a daily basis, undergoing minor adjustments of phase each day. Light is the most potent time cue for phase-shifting circadian rhythms, but the timing and amount of solar irradiation vary dynamically with season, especially with increasing distance from the equator. There is evidence that chronotype is modified by seasonal change, most likely due to the changes in the light environment, but interindividual differences in photoperiod responsiveness mean that some people are more affected than others. Differences in circadian light sensitivity due to endogenous biological reasons and/or previous light history are responsible for the natural variation in photoperiod responsiveness. Modern lifestyles that include access to artificial light at night, temperature-controlled environments, and spending much less time outdoors offer a buffer to the environmental changes of the seasons and may contribute to humans becoming less responsive to seasons.

Investigating daily fatigue scores during two-week offshore day shifts

ObjectivesThis study examined daily scores of fatigue and circadian rhythm markers over two-week offshore day shift periods. MethodsA prospective cohort study among N = 60 offshore day-shift workers working two-week offshore shifts was conducted. Offshore day shifts lasted from 07:00 – 19:00 h. Fatigue was measured objectively with pre- and post-shift scores of the 3-minute psychomotor vigilance tasks (PVT-B) parameters (reaction times, number of lapses, errors and false starts) and subjectively with pre- and post-shift Karolinska Sleepiness Scale (KSS) ratings. Evening saliva samples were collected on offshore days 2,7 and 13 to measure circadian rhythm markers such as dim-light melatonin onset times and cortisol. Generalized and linear mixed model analyses were used to examine daily fatigue scores over time. ResultsComplete data from N = 42 offshore day shift workers was analyzed. Daily parameters of objective fatigue, PVT-B scores (reaction times, average number of lapses, errors and false starts), remained stable over the course of the two-week offshore day shifts. Daily subjective post-shift fatigue scores significantly increased over the course of the two-week offshore shifts. Each day offshore was associated with an increased post-shift subjective fatigue score of 0.06 points (95%CI: .03 - .09 p < .001). No significant statistical differences in subjective pre-shift fatigue scores were found. Neither a circadian rhythm phase shift of melatonin nor an effect on the pattern and levels of evening cortisol was found. ConclusionDaily parameters of objective fatigue scores remained stable over the course of the two-week offshore day shifts. Daily subjective post-shift fatigue scores significantly increased over the course of the two-week offshore shifts. No significant changes in circadian rhythm markers were found. Increased post-shift fatigue scores, especially during the last days of an offshore shift, should be considered and managed in (offshore) fatigue risk management programs and fatigue risk prediction models.

Nobiletin protects against insulin resistance and disorders of lipid metabolism by reprogramming of circadian clock in hepatocytes

ScopeCircadian clock plays a principal role in orchestrating our daily physiology and metabolism, and their perturbation can evoke metabolic diseases such as fatty liver and insulin resistance. Nobiletin (NOB) has been demonstrated to possess antitumor and neuroprotective activities. The objective of the current study is to determine potential effects of NOB on modulating the core clock gene Bmal1 regarding ameliorating glucolipid metabolic disorders. ResultsOur results revealed that NOB partially reverse the relatively shallow daily oscillations of circadian clock genes and reset phase-shifting circadian rhythms in primary hepatocytes under metabolic disorders conditions. Importantly, NOB was found to be effective at amplifying glucose uptake via stimulating IRS-1/AKT signaling pathway, as well as blunting palmitate-induced lipogenesis in HepG2 cells via modulating AMPK-Sirt1 signaling pathway and key enzymes of de novo lipogenesis in a Bmal1-dependent manner. NOB attenuated palmitate-stimulated excessive secretions of ROS, restored the depletions of mitochondrial membrane potential, which is similar to the recovery in expressions of mitochondrial respiration complex I-IV. ConclusionThis study is the first to provide compelling evidences that NOB prevent cellular glucolipid metabolic imbalance and mitochondrial function in a Bmal1-dependent manner. Overall, NOB may serve as a nutritional preventive strategy in recovering metabolic disorders relevant to circadian clock.

Naloxone’s Effect on Activity-Induced Phase Shifts of Circadian Rhythms

Vigorous running in a novel exercise wheel by hamsters during the subjective day results in large (about 3 hr) phase advances of their circadian rhythms. We administered the opiate receptor antagonist naloxone at 10 mg/kg and 20 mg/kg (i.p.) and found that at 20 mg/kg it significantly reduced phase shifts. This dose of naloxone also reduced the amount of running shown by hamsters in the novel wheel. At the 20 mg/kg dose, the reduced amount of running resulted in smaller phase shifts. The results are consistent with the hypothesis that nonphotic phase shifts are linked to exercise and arousal in hamsters. However, because high amounts of running were accompanied by phase shifting in animals whose opiate receptors were blocked, the results provide no evidence that the rewarding nature of running in rodents is an important causal factor in nonphotic phase shifting beyond its role in promoting running.

368 - Circadian Rhythm Estimator Using Adaptive Notch Filter and Its Application to Locomotor Activity of Drosophila Melanogaster

The traditional method of circadian rhythm estimation is based on a double actogram that provides phase estimation on a daily basis, but not continuously and also fails to effectively filter noise. Our goal is to develop a circadian rhythm estimator that accurately and continuously estimates circadian phase while filtering noise. The estimator is a modified Adaptive Notch Filter (ANF), which is commonly used in signal processing. Drosophila Activity Monitor boxes house Drosophila fruit flies previously entrained to the same phase and contain sensors that measure the activity of flies. The actogram and ANF convert the raw data to a phase response curve (PRC), which describes the relationship between a stimuli (light) and circadian rhythm phase shift. White noise-corrupted data was also introduced to determine filtering effects. The PRC obtained from the actogram and ANF methods were nearly identical and also matched with literature values. With noise-corrupted data, the ANF PRC had an average error of 0.57 hours while the actogram PRC’s average error was 1.84 hours. The modified ANF is shown to be a valid and accurate method of modeling circadian rhythm continuously. The ANF was also able to successfully reject noise and the error against noise was very small compared to that of the actogram. Continuous circadian phase estimation allows more complex study of human circadian rhythm and further opens the possibility of personalized circadian rhythm estimation and light therapy.

Daily NO rhythms in peripheral clocks in aging male Wistar rats: protective effects of exogenous melatonin.

In mammals suprachiasmatic nucleus (SCN), acts as a light entrainable master clock and by generation of temporal oscillations regulates the peripheral organs acting as autonomous clocks resulting in overt behavioral and physiological rhythms. SCN also controls synthesis and release of melatonin (hormonal message for darkness) from pineal. Nitric Oxide (NO) acts as an important neurotransmitter in generating the phase shifts of circadian rhythms and participates in sleep-wake processes, maintenance of vascular tone as well as signalling and regulating inflammatory processes. Aging is associated with disruption of circadian timing system and decline in endogenous melatonin leading to several physiological disorders. Here we report the effect of aging on NO daily rhythms in various peripheral clocks such as kidney, intestine, liver, heart, lungs and testis. NO levels were measured at zeitgeber time (ZT) 0, 6, 12 and 18 in these tissues using Griess assay in male Wistar rats. Aging resulted in alteration of NO levels as well as phase of NO in both 12 and 24 months groups. Correlation analysis demonstrated loss of stoichiometric interaction between the various peripheral clocks with aging. Age induced alterations in NO daily rhythms were found to be most significant in liver and, interestingly least in lungs. Neurohormone melatonin, an endogenous synchroniser and an antiaging agent decreases with aging. We report further differential restoration with exogenous melatonin administration of age induced alterations in NO daily rhythms and mean levels in kidney, intestine and liver and the stoichiometric interactions between the various peripheral clocks.