Distinct modes of melatonin secretion in normal men

Effects of High-Intensity Interval Training on Melatonin Function and Cellular Lymphocyte Apoptosis in Sedentary Middle-Aged Men

Background: Physical performance increased by controlled interventions of high-intensity intermittent training (HIIT); however, little is known about their influence as anti-aging and antioxidant effects, or their role in mitochondrial biogenesis. Purpose: This study aimed to determine the effects of HIIT for 12 weeks on melatonin function, lymphocyte cell apoptosis, oxidative stress on aging, and physical performance. Methods: Eighty healthy male subjects aged 18-65 years randomly participated in a HIIT-exercise training program for 12 weeks. Anthropometric analysis, cardiovascular fitness, total antioxidant capacity (TAC), lymphocyte count and apoptosis, and serum melatonin and cytochrome c oxidase (COX), were estimated for all subjects before and after HIIT-exercise training. HIIT training was performed in subjects for 12 weeks. Results: Data analysis showed a significant increase in the expression levels of the melatonin hormone (11.2 ± 2.3, p < 0.001), TAC (48.7 ± 7.1, p < 0.002), COX (3.7 ± 0.75, p < 0.001), and a higher percentage of lymphocyte apoptosis (5.2 ± 0.31, p < 0.003). In addition, there was an improvement in fitness scores (W; 196.5 ± 4.6, VO₂max; 58.9 ± 2.5, p < 0.001), adiposity markers (p < 0.001); BMI, WHtR, and glycemic control parameters (p < 0.01); FG, HbA1c (%), FI, and serum C-peptide were significantly improved following HIIT intervention. Both melatonin and lymphocyte apoptosis significantly correlated with the studied parameters, especially TAC and COX. Furthermore, the correlation of lymphocyte apoptosis with longer exercise duration was significantly associated with increased serum melatonin following exercise training. This association supports the mechanistic role of melatonin in promoting lymphocyte apoptosis either via the extrinsic mediator pathway or via inhibition of lymphocyte division in the thymus and lymph nodes. Additionally, the correlation between melatonin, lymphocyte apoptosis, TAC, and COX activities significantly supports their role in enhancing physical performance. Conclusions: The main findings of this study were that HIIT exercise training for 12 weeks significantly improved adiposity markers, glycemic control parameters, and physical performance of sedentary older adult men. In addition, melatonin secretion, % of lymphocyte apoptosis, COX activities, and TAC as biological aging markers were significantly increased following HIIT exercise training interventions for 12 weeks. The use of HIIT exercise was effective in improving biological aging, which is adequate for supporting chronological age, especially regarding aging problems. However, subsequent studies are required with long-term follow-up to consider HIIT as a modulator for several cardiometabolic health problems in older individuals with obesity.

Prognostic roles of sleep electroencephalography pattern and circadian rhythm biomarkers in the recovery of consciousness in patients with coma: a prospective cohort study

OBJECTIVE

To investigate the potential prognostic value of sleep electroencephalography (EEG) pattern and serum circadian rhythm biomarkers in the recovery of consciousness in patients at the acute stage of coma.

METHODS

A prospective observational study which included 75 patients with coma was conducted. Twenty-four-hour continuous polysomnography (PSG) was performed to determine the sleep EEG pattern according to the modified Valente's Grade (mVG) that we proposed. Serum levels of melatonin and orexin-A at four consecutive time points during the PSG were examined. Patients were then followed for one month to determine their level of consciousness. Multivariate logistic regression analysis was performed to examine associations between demographics, aetiology, baseline clinical features (pupillary and corneal reflex, and neuron-specific enolase [NSE]), clinical scores (Glasgow Coma Scale-Motor Response [GCS-M], Full Outline of Unresponsiveness [FOUR] scale, Acute Physiology and Chronic Health Evaluation II [APACHE II] scale), mVG, serum circadian biomarkers, and recovery of consciousness within one month.

RESULTS

Within one month of enrolment, 34 patients regained consciousness and 36 patients remained non-conscious. Spearman rank correlation revealed a significant association between mVG and state of consciousness after one month. Significant variation in serum melatonin or orexin-A was not detected in either the conscious or non-conscious groups. Hypoxic aetiology, APACHE II, and mVG were independently associated with recovery of consciousness within one month.

CONCLUSION

Sleep EEG structure, hypoxic aetiology, and APACHE II can independently predict recovery of consciousness in patients with acute coma. Taken together, we encourage neurologists to use sleep elements to assess patients with acute coma.

Melatonin secretion is impaired in women with preeclampsia and an abnormal circadian blood pressure rhythm

Non-dipping circadian blood pressure (BP) is a common finding in preeclampsia, accompanied by adverse outcomes. Melatonin plays pivotal role in biological circadian rhythms. This study investigated the relationship between melatonin secretion and circadian BP rhythm in preeclampsia. Cases were women with preeclampsia treated between January 2006 and June 2007 in the University Hospital of Larissa. Volunteers with normal pregnancy, matched for chronological and gestational age, served as controls. Twenty-four hour ambulatory BP monitoring was applied. Serum melatonin and urine 6-sulfatoxymelatonin levels were determined in day and night time samples by enzyme-linked immunoassays. Measurements were repeated 2 months after delivery. Thirty-one women with preeclampsia and 20 controls were included. Twenty-one of the 31 women with preeclampsia were non-dippers. Compared to normal pregnancy, in preeclampsia there were significantly lower night time melatonin (48.4 ± 24.7 vs. 85.4 ± 26.9 pg/mL, p<0.001) levels. Adjustment for circadian BP rhythm status ascribed this finding exclusively to non-dippers (p<0.01). Two months after delivery, in 11 of the 21 non-dippers both circadian BP and melatonin secretion rhythm reappeared. In contrast, in cases with retained non-dipping status (n=10) melatonin secretion rhythm remained impaired: daytime versus night time melatonin (33.5 ± 13.0 vs. 28.0 ± 13.8 pg/mL, p=0.386). Urinary 6-sulfatoxymelatonin levels were, overall, similar to serum melatonin. Circadian BP and melatonin secretion rhythm follow parallel course in preeclampsia, both during pregnancy and, at least 2 months after delivery. Our findings may be not sufficient to implicate a putative therapeutic effect of melatonin, however, they clearly emphasize that its involvement in the pathogenesis of a non-dipping BP in preeclampsia needs intensive further investigation.

Acute increase in urinary 6-sulfatoximelatonin after clomipramine, as a predictive measure for emotional improvement

Nocturnal melatonin pineal output is triggered by sympathetic outflow. Antidepressants that block norepinephrine neuronal uptake should increase pineal function. This can be monitored by measuring 6-sulfatoximelatonin (aMT6s), the main melatonin metabolite, in the urine. In this study, we compared the excretion of aMT6s before (baseline), one, and 21 days after administration of clomipramine to healthy subjects (n = 32). At the end of treatment, subjects were divided into responders (n = 12) and non-responders (n = 20) according to the improvement in their emotional state in three out of four domains (interpersonal tolerance, efficiency, well-being and feeling different from the usual self). There was no difference in aMT6s before clomipramine between responders and non-responders in any of the time intervals analysed (06:00-12:00, 12:00-18:00, 18:00-24:00 and 24:00-06:00 hours). At day one, but not at day 21, the fraction of aMT6s excreted during the time interval 24:00-06:00, relative to the total amount excreted by each subject per day, was significantly higher (P = 0.0287) than baseline (0.57 +/- 0.04) in responders. No significant difference was observed in non-responders. The increase in pineal function induced by clomipramine was restricted to day one, indicating that long-lasting adaptation restores pineal function. In addition, the day one increase in aMT6s was significantly increased only in the responders group, raising the possibility that the blocking of neuronal uptake is predictive of emotional improvement.

Acupressure on the extra 1 acupoint: the effect on bispectral index, serum melatonin, plasma beta-endorphin, and stress

BACKGROUND

Acupressure on the "extra 1" point decreases bispectral index (BIS) values and stress.

METHODS

We investigated the BIS, melatonin, beta-endorphin, and verbal stress score values before, after 10 min of acupressure application on the extra 1 point, on a sham point, after no acupressure, and 1 h after completion of each intervention in 12 volunteers.

RESULTS

The BIS and verbal stress score values were decreased after acupressure on the extra 1 point (P = 0.0001 and P = 0.008, respectively), but melatonin and beta-endorphin did not change.

CONCLUSION

Acupressure on the extra 1 point has no effect on melatonin and beta-endorphin levels.

Melatonin and immunomodulation: connections and potential clinical applications

Melatonin is the main hormone secreted by the pineal gland in the human brain. It has a strong impact on the sleep-wake cycle and is considered a general modulator of the human circadian rhythm. Apart from these well-established properties, melatonin possesses immunomodulatory, antioxidative and antiinflammatory properties. The potential ability of this hormone to act synergistically with several cytokines by enhancing their antitumoral activity and dramatically decreasing their adverse effects has placed melatonin among the new and promising agents in cancer immunotherapy. The use of the neurohormone alone or in combination with cytokines and traditional chemotherapeutic drugs is currently under vigorous investigation. Experimental and clinical trials have already depicted some of the immunomodulatory and antitumor effects of melatonin, delineating the need for further research in this field.

The basic physiology and pathophysiology of melatonin

Melatonin is a methoxyindole synthesized and secreted principally by the pineal gland at night under normal environmental conditions. The endogenous rhythm of secretion is generated by the suprachiasmatic nuclei and entrained to the light/dark cycle. Light is able to either suppress or synchronize melatonin production according to the light schedule. The nycthohemeral rhythm of this hormone can be determined by repeated measurement of plasma or saliva melatonin or urine sulfatoxymelatonin, the main hepatic metabolite. The primary physiological function of melatonin, whose secretion adjusts to night length, is to convey information concerning the daily cycle of light and darkness to body physiology. This information is used for the organisation of functions, which respond to changes in the photoperiod such as the seasonal rhythms. Seasonal rhythmicity of physiological functions in humans related to possible alteration of the melatonin message remains, however, of limited evidence in temperate areas in field conditions. Also, the daily melatonin secretion, which is a very robust biochemical signal of night, can be used for the organisation of circadian rhythms. Although functions of this hormone in humans are mainly based on correlative observations, there is some evidence that melatonin stabilises and strengthens coupling of circadian rhythms, especially of core temperature and sleep-wake rhythms. The circadian organisation of other physiological functions could depend on the melatonin signal, for instance immune, antioxidative defences, hemostasis and glucose regulation. Since the regulating system of melatonin secretion is complex, following central and autonomic pathways, there are many pathophysiological situations where the melatonin secretion can be disturbed. The resulting alteration could increase predisposition to disease, add to the severity of symptoms or modify the course and outcome of the disorder.

The effects of nocturnal life on endocrine circadian patterns in healthy adults

We observed the 24-hour patterns of endocrine in medical students who lived either a diurnal life or nocturnal life. Nocturnal life was designed by skipping their breakfast but consuming much (>50% of their daily food intake) in the evening and at night with the sleep from 0130 h to 0830 h the next morning. After 3 weeks in the experimental life, the 24-hour plasma concentrations of melatonin, leptin, glucose and insulin were measured every three hours. Both plasma melatonin and leptin showed peaks at 0300 h in the diurnal lifestyle group, and the night peaks decreased in the nocturnal lifestyle group. The changes in the patterns of melatonin and leptin were highly consistent with that of night-eating syndrome (NES). Plasma glucose increased after all meals in both groups. Its concentration maintained a high level in the nocturnal lifestyle group between midnight and early morning while insulin secretion decreased markedly during this period. Furthermore, the strong association between glucose and insulin in the diurnal lifestyle group after meals was damaged in the nocturnal lifestyle group. It was suggested that nocturnal life leads to the impairment of insulin response to glucose. Taking these results together, nocturnal life is likely to be one of the risk factors to health of modern people, including NES, obesity and diabetes.

Characterization of nocturnal ultradian rhythms of melatonin in children with growth hormone-dependent and independent growth delay

To assess the existence of a possible nocturnal ultradian rhythm of melatonin in children, we analyzed 28 pediatric patients (mean age, 9.08 +/- 2.2 yr) with GH-dependent and GH-independent growth delay. Plasma melatonin was measured by RIA in children sampled every 30 min between 2100-0900 h. Statistical analysis consisted of cluster analysis to examine the presence of peaks and troughs. The pattern of melatonin levels was related to the cause of growth delay, although the means of the nocturnal concentrations of melatonin were similar in all children. Interestingly, children with a GH deficit showed a nearly normal melatonin profile, whereas children with normal GH values but abnormal growth displayed atypical profiles of melatonin. The results also prove the existence of an ultradian rhythm of melatonin in most of the patients studied. The ultradian rhythm of melatonin in children was characterized by irregular interburst intervals, thus differing from the rhythm previously described in adults that had an almost constant pulse frequency. Moreover, the existence of low and high melatonin producers was revealed in the study, a feature unrelated to the cause of growth delay. The group of children with a GH deficit showed the lowest values of integrated melatonin production and of the area of peaks and troughs. These results prove that children exhibit an ultradian rhythm of melatonin like that in adults. Whereas it is not clear whether the episodic production of melatonin is required for its biological actions, the existence of irregular pulses may reflect endocrine influences at this age and/or the immaturity of the intrinsic pulse generator.

Estimation of frequently sampled nocturnal melatonin production in humans by deconvolution analysis: evidence for episodic or ultradian secretion

In order to investigate nocturnal melatonin production and clearance rates, we applied deconvolution analysis to plasma melatonin concentration time series obtained every 20 min for 12 hr from 20:00 h to 08:00 h in two groups of healthy subjects at rest (group 1, 12 male subjects, 22-26 yr; group 2, ten female subjects, 31-42 yr). The estimated melatonin production rate from group 1 (0.55 +/- 0.21 microg/kg/night) was significantly higher than that of group 2 (0.26 +/- 0.19 microg/kg/night), as well as the mass of melatonin released per burst (275 +/- 110 vs. 145 +/- 130 pg/mL for groups 1 and 2, respectively), the amplitude of secretory bursts (7.8 +/- 3.2 vs. 4.7 +/- 3.5 pg/mL/min), and the pulsatile melatonin production rate (2.76 +/- 1.14 vs. 1.27 +/- 0.97 ng/mL/night). These differences could reflect alterations related to age and or gender. No differences were observed between the two groups in the secretory burst half-duration and frequency and the interburst interval. Melatonin production rates, as estimated by deconvolution analysis, are in agreement with other independent estimates, especially the isotopic method, and disclose an ultradian rhythmicity.

The onset of increased melatonin secretion after the onset of darkness in sheep depends on the photoperiod

In sheep, melatonin secretion occurs rapidly after the onset of darkness, but the interval fluctuates according to different authors. The aim of this study was to determine this interval in sheep subjected to a long or a short photoperiod. Blood samples were taken at the right jugular vein every 100 s for 1 hr after the onset of darkness. The experiment was repeated on three consecutive days either in long (LD 16:8) or in short photoperiod (LD 8:16) on the same animals. Melatonin secretion was found to begin within 11 min under long photoperiod and 20 min under short period. It can be concluded that the onset of melatonin secretion depends on the duration of the photoperiod.

Nocturnal plasma melatonin profile and melatonin kinetics during infusion in status migrainosus

The plasma melatonin profile was significantly disturbed (phase-shift of the maximum melatonin level) in four out of six female sufferers from status migrainosus, compared with nine healthy controls. The number of secretion peaks was similar in both groups. A nocturnal 20 micrograms melatonin infusion (from 21.00 to 01.00 h) evoked plasma melatonin levels slightly higher than a physiological secretion peak. During infusion, the episodes of secretion were reinforced and the endogenous plasma profile was phase-advanced in two patients displaying a phase-delay. These data suggest impaired pineal function in migraine. In the absence of side effects of melatonin infusion, the relief of certain migraine symptoms described by our patients might support a controlled trial of melatonin in migraine.