Effects of vitamin B12 on plasma melatonin rhythm in humans: Increased light sensitivity phase-advances the circadian clock?

Effects of timed physical exercise were examined on the reentrainment of sleep-wake cycle and circadian rhythms to an 8-h phase-advanced sleep schedule. Seventeen male adults spent 12 days in a temporal isolation facility with dim light conditions (<10 lux). The sleep schedule was phase-advanced by 8 h from their habitual sleep times for 4 days, which was followed by a free-run session for 6 days, during which the subjects were deprived of time cues. During the shift schedule, the exercise group ( n = 9) performed physical exercise with a bicycle ergometer in the early and middle waking period for 2 h each. The control group ( n = 8) sat on a chair at those times. Their sleep-wake cycles were monitored every day by polysomnography and/or weight sensor equipped with a bed. The circadian rhythm in plasma melatonin was measured on the baseline day before phase shift: on the 4th day of shift schedule and the 5th day of free-run. As a result, the sleep-onset on the first day of free-run in the exercise group was significantly phase-advanced from that in the control and from the baseline. On the other hand, the circadian melatonin rhythm was significantly phase-delayed in the both groups, showing internal desynchronization of the circadian rhythms. The sleep-wake cycle resynchronized to the melatonin rhythm by either phase-advance or phase-delay shifts in the free-run session. These findings indicate that the reentrainment of the sleep-wake cycle to a phase-advanced schedule occurs independent of the circadian pacemaker and is accelerated by timed physical exercise.

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Melatonin rhythm and other outputs of the master circadian clock in the desert goat ( Capra hircus ) are entrained by daily cycles of ambient temperature

Journal of Pineal Research ◽

10.1111/jpi.12634 ◽

2020 ◽

Vol 68 (3) ◽

Cited By ~ 1

Author(s):

Hicham Farsi ◽

Driss Harti ◽

Mohamed R. Achaâban ◽

Mohammed Piro ◽

Véronique Raverot ◽

...

Keyword(s):

Ambient Temperature ◽

Circadian Clock ◽

Capra Hircus ◽

Melatonin Rhythm ◽

Daily Cycles

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The Role of Light Sensitivity and Intrinsic Circadian Period in Predicting Individual Circadian Timing

Journal of Biological Rhythms ◽

10.1177/0748730420962598 ◽

2020 ◽

Vol 35 (6) ◽

pp. 628-640 ◽

Cited By ~ 1

Author(s):

Julia E. Stone ◽

Elise M. McGlashan ◽

Nina Quin ◽

Kayan Skinner ◽

Jessica J. Stephenson ◽

...

Keyword(s):

Sensitivity Analysis ◽

Circadian Clock ◽

Response Curve ◽

Mean Absolute Error ◽

Absolute Error ◽

Light Sensitivity ◽

Circadian Period ◽

Interindividual Differences ◽

Circadian Timing ◽

The Mean

There is large interindividual variability in circadian timing, which is underestimated by mathematical models of the circadian clock. Interindividual differences in timing have traditionally been modeled by changing the intrinsic circadian period, but recent findings reveal an additional potential source of variability: large interindividual differences in light sensitivity. Using an established model of the human circadian clock with real-world light recordings, we investigated whether changes in light sensitivity parameters or intrinsic circadian period could capture variability in circadian timing between and within individuals. Healthy participants ( n = 12, aged 18-26 years) underwent continuous light monitoring for 3 weeks (Actiwatch Spectrum). Salivary dim-light melatonin onset (DLMO) was measured each week. Using the recorded light patterns, a sensitivity analysis for predicted DLMO times was performed, varying 3 model parameters within physiological ranges: (1) a parameter determining the steepness of the dose-response curve to light ( p), (2) a parameter determining the shape of the phase-response curve to light ( K), and (3) the intrinsic circadian period ( tau). These parameters were then fitted to obtain optimal predictions of the three DLMO times for each individual. The sensitivity analysis showed that the range of variation in the average predicted DLMO times across participants was 0.65 h for p, 4.28 h for K, and 3.26 h for tau. The default model predicted the DLMO times with a mean absolute error of 1.02 h, whereas fitting all 3 parameters reduced the mean absolute error to 0.28 h. Fitting the parameters independently, we found mean absolute errors of 0.83 h for p, 0.53 h for K, and 0.42 h for tau. Fitting p and K together reduced the mean absolute error to 0.44 h. Light sensitivity parameters captured similar variability in phase compared with intrinsic circadian period, indicating they are viable targets for individualizing circadian phase predictions. Future prospective work is needed that uses measures of light sensitivity to validate this approach.

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0433 Targeting Light Sensitivity Parameters to Optimize Circadian Phase Predictions

SLEEP ◽

10.1093/sleep/zsaa056.430 ◽

2020 ◽

Vol 43 (Supplement_1) ◽

pp. A166-A166

Author(s):

J E Stone ◽

E M McGlashan ◽

S W Cain ◽

A J Phillips

Keyword(s):

Sensitivity Analysis ◽

Circadian Clock ◽

Mean Absolute Error ◽

Light Response ◽

Absolute Error ◽

Light Sensitivity ◽

Model Parameters ◽

Circadian Period ◽

Individual Level ◽

Circadian Phase

Abstract Introduction Existing models of the human circadian clock accurately predict phase at group-level but not at individual-level. Interindividual variability in light sensitivity is not currently accounted for in these models and may be a practical approach to improving individual-level predictions. Using the gold-standard predictive model, we (i) identified whether varying light sensitivity parameters produces meaningful changes in predicted phase in field conditions; and (ii) tested whether optimizing parameters can significantly improve accuracy of circadian phase prediction. Methods Healthy participants (n=12, 7 women, aged 18-26) underwent continuous light and activity monitoring for 3 weeks (Actiwatch Spectrum). Salivary dim light melatonin onset (DLMO) was measured each week. A model of the human circadian clock and its response to light was used to predict the three weekly DLMO times using the individual’s light data. A sensitivity analysis was performed varying three model parameters within physiological ranges: (i) amplitude of the light response [p]; (ii) advance vs. delay bias of the light response [K]; and (iii) intrinsic circadian period [tau]. These parameters were then fitted using least squares estimation to obtain optimal predictions of DLMO for each individual. Accuracy was compared between optimized parameters and default parameters. Results The default model predicted DLMO with mean absolute error of 1.02h. Sensitivity analysis showed the average range of variation in predicted DLMOs across participants was 0.65h for p, 4.28h for K and 3.26h for tau. Fitting parameters independently, we found mean absolute error of 0.85h for p, 0.71h for K and 0.75h for tau. Fitting p and K together reduced mean absolute error to 0.57h. Conclusion Light sensitivity parameters capture similar or greater variability in phase as intrinsic circadian period, indicating they are a viable option for individualising circadian phase predictions. Future prospective work is needed using measures of light sensitivity to validate this approach. Support N/A

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A Chronobiological Study of Melatonin, Cortisol Growth Hormone and Prolactin Secretion in Cluster Headache

Cephalalgia ◽

10.1046/j.1468-2982.1984.0404213.x ◽

1984 ◽

Vol 4 (4) ◽

pp. 213-220 ◽

Cited By ~ 115

Author(s):

Guy Chazot ◽

Bruno Claustrat ◽

Jocelyne Brun ◽

Daniel Jordan ◽

Geneviève Sassolas ◽

...

Keyword(s):

Growth Hormone ◽

Cluster Headache ◽

Prolactin Secretion ◽

Temporal Organization ◽

Plasma Prolactin ◽

Melatonin Rhythm ◽

Plasma Melatonin ◽

Sleep Recording ◽

Plasma Gh ◽

Headache Patients

The temporal organization of plasma melatonin. cortisol. growth hormone (GH) and prolactin secretion was examined in healthy rested controls and in patients suffering from episodic cluster headache. Eleven patients with typical cluster headache (10 men, 1 female) and 8 male controls were studied over a 24–h period: blood was collected at 2–h intervals during the day and at l-h intervals at night. Plasma melatonin. cortisol, GH and prolactin levels were determined by radioimmunoassay. Most of the cluster headache patients showed a decrease in nocturnal melatonin secretion and the melatonin rhythm was even completely abolished in one patient. Chronobiological analysis of the cluster headache patients' 24–h plasma melatonin profile showed a significant decrease in amplitude and mesor: these were 58.7 pg/ml and 34.4 pg/ml respectively in control subjects, versus 18.7 pg/ml and 17.6 pg/ml for the patients. In addition. patients showed a significant phase-advance in their melatonin rhythm For cortisol, the rhythm appeared slightly blunted in the cluster headache group and was significantly phase-advanced. The plasma prolactin profile showed no significant alteration, but for plasma GH the nocturnal peak was advanced in some patients: in the absence of sleep recording, however, no conclusion could be drawn. Results from this study suggest a neuroendocrine dysregulation in cluster headache in the endogenous clock which controls the pineal rhythmicity.

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