Plasma Melatonin Research Articles

Intranasal delivery of paroxetine: A preclinical study on pharmacokinetics, depressive-like behaviour, and neurochemical sex differences

Treatment of major depressive disorder remains a major unmet clinical need. Given the advantages of intranasal administration for targeted brain delivery, the present study aimed at investigating the pharmacokinetics of paroxetine, after its intranasal instillation and assessing its potential therapeutic effect on female and male mice subjected to unpredictable chronic mild stress (UCMS) protocol.IN administration revealed direct nose-to-brain paroxetine delivery but dose- and sex-dependent differences. Pharmacokinetics was nonlinear and paroxetine concentrations were consistently higher in plasma and brain of male mice. Additionally, UCMS decreased animal preference for sucrose in both male and female mice following acute (p < 0.01) and chronic stress (p < 0.05), suggesting anhedonia. Both male and female mice exhibited depressive-like behavior in the forced swimming test. UCMS females displayed a significantly longer immobility time and shorter climbing time than the control group (p < 0.05), while no differences were found between male mice. Two weeks of paroxetine intranasal administration reduced immobility time and lengthened climbing and swimming time, approaching values similar to those observed in the healthy control group. The therapeutic effect was stronger on female mice.Importantly, melatonin plasma levels were significantly decreased in female mice following UCMS (p < 0.05), while males exhibited heightened corticosterone levels. On the other hand, treatment with IN paroxetine significantly increased corticosterone and melatonin levels in both sexes compared to healthy mice (p < 0.05).Intranasal paroxetine delivery undoubtedly ameliorated the behavioral despair, characteristic of depressive-like animals. Despite its efficiency in male and female mice subjected to UCMS, females were more prone to this novel therapeutic strategy.

Effect of clock rhythm on emergence agitation and early postoperative delirium in older adults undergoing thoracoscopic lung cancer surgery: protocol for a prospective, observational, cohort study

IntroductionSurgeries conducted at night can impact patients’ prognosis, and the mechanism may be related to circadian rhythm, which influence normal physiological functions and pathophysiological changes. Melatonin is primarily a circadian hormone with hypnotic and chronobiotic effects, thereby affecting disease outcomes through influencing the expression of inflammatory factors and biochemical metabolism. This study aims to observe the effects of circadian rhythms on emergence agitation and early postoperative delirium of older individuals undergoing thoracoscopic lung cancer surgery and explore the possible regulatory role of melatonin.MethodsThis prospective, observational, cohort study will involve 240 patients. Patients will be routinely divided into three groups based on the time of the surgery: T1 (8:00–14:00), T2 (14:00–20:00) and T3 group (20:00–08:00). The primary outcome will be the incidence of emergence agitation assessed via the Richmond Agitation and Sedation Scale (RASS) in the post-anesthesia care unit (PACU). Secondary outcomes will include the incidence of early postoperative delirium assessed via the Confusion Assessment Method (CAM) on postoperative day 1, pain status assessed via the numerical rating scale (NRS) in the PACU, sleep quality on postoperative day 1 and changes in perioperative plasma melatonin, clock genes and inflammatory factor levels. Postoperative surgical complications, intensive care unit admission and hospital length of stay will also be evaluated.DiscussionThis paper describes a protocol for investigating the effects of circadian rhythms on emergence agitation and early postoperative delirium of older individuals undergoing thoracoscopic lung cancer surgery, as well as exploring the potential regulatory role of melatonin. By elucidating the mechanism by which circadian rhythms impact postoperative recovery, we aim to develop a new approach for achieving rapid recovery during perioperative period.Trial registrationThe study was registered at the Chinese Clinical Trials Registry (ChiCTR2000040252) on November 26, 2020, and refreshed on September 4, 2022.

The role of melatonin deficiency induced by pinealectomy on motor activity and anxiety responses in young adult, middle-aged and old rats.

Aging affects anxiety levels in rats while the pineal gland, via its hormone melatonin, could modulate their inherited life "clock." The present study aimed to explore the impact of plasma melatonin deficiency on anxiety responses and the possible involvement of the hypothalamic-pituitary-adrenocortical (HPA) axis and heat shock proteins (Hsp) 70 and 90 in the frontal cortex (FC) and the hippocampus in young adult, middle-aged and elderly rats with pinealectomy. Melatonin deficiency induced at different life stages did not affect the lifespan of rats. Pinealectomy abolished the circadian rhythm of motor activity, measured for 48h in the actimeter, in young adult but not in middle-aged rats. Pinealectomy reduced the motor activity of the young adult rats during the dark phase and impaired the diurnal activity variations of old rats. The same generations (3- and 18month-old rats with pinealectomy) had lower anxiety levels than the matched sham groups, measured in three tests: elevated-plus maze, light-dark test, and novelty-suppressed feeding test. While the activity of the HPA axis remained intact in young adult and middle-aged rats with melatonin deficiency, a high baseline corticosterone level and blunted stress-induced mechanism of its release were detected in the oldest rats. Age-associated reduced Hsp 70 and 90 levels in the FC but not in the hippocampus were detected. Pinealectomy diminished the expression of Hsp 70 in the FC of middle-aged rats compared to the matched sham rats. Our results suggest that while melatonin hormonal dysfunction impaired the motor activity in the actimeter and emotional behavior in young adult and elderly rats, the underlying pathogenic mechanism in these generations might be different and needs further verification.

Metabolomics study reveals blood biomarkers for early diagnosis of chronic kidney disease and IgA nephropathy: A retrospective cross-sectional study

Background and aimsChronic kidney disease (CKD) causes low quality of life and alarming morbidity and mortality. The crucial to retard CKD progression is to diagnose early for timely treatment. IgA nephropathy (IgAN) is a typical CKD and the most common glomerulonephritis. Both CKD and IgAN lack accurate and sensitive blood biomarkers for early diagnosis. Here we report the potential of plasma biomarkers for early diagnosis of CKD and IgAN. Materials and methodsPlasma levels of metabolites derived from tryptophan were quantified with an LC-MS/MS-based metabolomics for two cohorts. Based on the predictive probability of each metabolite, multivariate models including logistic regression and random forest were used to establish the early diagnostic biomarkers for CKD and IgAN. ResultsThe plasma melatonin diagnosed early CKD (stages Ⅰ−Ⅱ) with an accuracy exceeding 95%, and a panel of melatonin and tryptophan achieved a remarkable 100% accuracy in diagnosing early CKD. Furthermore, indole-3-lactic acid had an excellent ability to distinguish IgAN among CKD patients. Based on the CKD screening and IgAN diagnosis primarily contributed by melatonin and indole-3-lactic acid, early IgAN could be diagnosed with an accuracy of over 85%. ConclusionsThis study provides promising plasma biomarkers for early diagnosis of CKD and IgAN.

Effects of acute hypothyroidism on plasma melatonin and Aanat and Asmt expression in the pineal gland and gonads of rats.

The reproductive system is tightly regulated by environmental and physiological signals. Melatonin, known as the hormone of darkness, plays a crucial role in regulating both the circadian and reproductive systems in mammals. Hypothyroidism is a key endocrine disorder that harms the reproductive system. Despite many studies on melatonin's effects on the reproductive system, there is conflicting information regarding melatonin synthesis modulation in hypothyroidism. The objective of this study was to investigate the modulation of plasma melatonin levels and gene expression of Aanat and Asmt in the pineal gland and gonads of rats with hypothyroidism at different times of the day. Female and male Wistar rats were divided into control and hypothyroid groups. Hypothyroidism was induced using propylthiouracil (PTU) for 15 days, rats were euthanized six hours after lights on (ZT6), before lights off (ZT11.5), and six hours after lights off (ZT18). Free thyroxine (FT4) and melatonin were quantified in plasma, and gene expressions of melatonin synthesizing enzymes (Aanat and Asmt) were measured in pineal and sexual organs (testis and ovary). Also, morphological analysis was performed in sexual organs. The results reveal some disparities between the sexes. Hypothyroidism reduced antral and primary follicles in the ovary, and reduced the weight of testis, epididymis, and prostate. In relation to gene expression, we observed a reduction in Aanat expression in the pineal gland during the light phase (ZT6), and in males, this reduction occurred during the dark phase (ZT18). Regarding Asmt expression, there was a decrease in females also during the dark phase (ZT18). In the gonads, there was an increase in expression in both sexes at ZT11.5. Additionally, it was interesting to observe the association between FT4 levels and Asmt expression in the gonads. This study showed that acute hypothyroidism can affect components of the melatonergic system in gonads, particularly gene expression of melatonin synthesis enzymes (Aanat and Asmt) contributing to changes in reproduction organs during disease progression. These findings enhance our understanding of melatonin synthesis in the reproductive system during hypothyroidism, showing distinct responses in male and female rats, and suggest that hypothyroidism affects the circadian rhythmicity of melatonin synthesis in a sex-dependent manner.

Insufficient Plasma Melatonin and Its Association With Neuropsychiatric Impairments in Patients With T2DM.

Purpose: Type 2 diabetes mellitus (T2DM) is associated with multiple neuropsychiatric impairments, including cognitive dysfunction, and melatonin (MLT) plays a crucial role in maintaining normal neuropsychiatric functions. This study is aimed at investigating the change in plasma MLT levels and its association with neuropsychiatric impairments in T2DM patients. Methods: One hundred twenty-six T2DM patients were recruited, and their demographics and clinical data were collected. Apart from the plasma glycated hemoglobin (HbA1c) levels and other routine metabolic indicators, the plasma concentrations of MLT, C-reactive protein (CRP), Interleukin 6 (IL-6), soluble myeloid triggered receptor 1 (sTREM 1), and receptor 2 (sTREM 2) were measured. Moreover, the executive function and depressive tendency were evaluated via the Behavior Rating Inventory of Executive Function-Adult Version (BRIEF-A) and the Epidemiological Research Center Depression Scale (CES-D), respectively. Result: Compared with the low HbA1c group, the T2DM patients in the high HbA1c group presented lower plasma MLT levels but higher plasma concentrations of inflammatory biomarker levels, together with higher scores in the BRIEF-A and CES-D scales. Moreover, results of the Pearson correlation test showed that the plasma MLT levels were negatively correlated with the BRIEF-A and CES-D scores, as well as plasma concentrations of HbA1c and inflammatory indications, indicating that MLT may mediate their neuroinflammation and neuropsychiatric impairments. Furthermore, the ROC curve results indicated that plasma MLT levels have a predictive effect on executive impairment and depressive status in T2DM patients. Conclusion: MLT levels decreased in patients with T2DM and were associated with neuropsychiatric impairments and inflammatory status, and MLT might be developed as a therapeutic agent and predictive indicator for T2DM-associated executive impairment and depression status.

Melatonin suppression by light involves different retinal photoreceptors in young and older adults.

Age-related sleep and circadian rhythm disturbances may be due to altered nonvisual photoreception. Here, we investigated the temporal dynamics of light-induced melatonin suppression in young and older individuals. In a within-subject design study, young and older participants were exposed for 60 min (0030-0130 at night) to nine narrow-band lights (range: 420-620 nm). Plasma melatonin suppression was calculated at 15, 30, 45, and 60 min time intervals. Individual spectral sensitivity of melatonin suppression and photoreceptor contribution were predicted for each interval and age group. In young participants, melanopsin solely drove melatonin suppression at all time intervals, with a peak sensitivity at 485.3 nm established only after 15 min of light exposure. Conversely, in older participants, spectral light-driven melatonin suppression was best explained by a more complex model combining melanopsin, S-cone, and M-cone functions, with a stable peak (~500 nm) at 30, 45, and 60 min of light exposure. Aging is associated with a distinct photoreceptor contribution to melatonin suppression by light. While in young adults melanopsin-only photoreception is a reliable predictor of melatonin suppression, in older individuals this process is jointly driven by melanopsin, S-cone, and M-cone functions. These findings offer new prospects for customizing light therapy for older individuals.

Role of salivary and plasma melatonin levels in oral squamous cell carcinoma

Objectives: The present research aims to look into the variations in levels of plasma and saliva melatonin with the sleep-wake cycle in healthy individuals and its correlation with the levels in oral squamous cell carcinoma (OSCC) patients and to explore the possibility of the use of plasma and saliva, as reliable, minimally-invasive/ non-invasive, and biofluids for measuring the levels of melatonin as biomarkers for the diagnosis of OSCC. Material and Methods: This comparative case–control prospective study was conducted on histopathologically proven 10 patients suffering from OSCC (Group II) and 10 healthy individuals (Group I) belonging to the age group of 25–65 years. The antecubital fossa region was used to draw peripheral venous blood, which was then centrifuged, and the plasma was kept at −200C. Using the passive drool technique, approximately 5 mL of unstimulated saliva samples were obtained, and the samples were kept at −200C. Both the samples were assayed as early as possible. Results: The result obtained was that the salivary and plasma melatonin levels were much higher during evening hours than morning interval in the healthy group (Group I). A similar trend was shown in Group II, compared to patients with OSCC, healthy patients have much higher levels of melatonin in their saliva and plasma. Conclusion: Hence, we conclude that the evaluation of the salivary melatonin level of patients suffering from OSCC may be considered reliable as well as non-invasive methods in the early diagnosis of OSCC. Saliva may be considered more advantageous over plasma for being non-invasive, less technique sensitive procedure, and having good patient compliance.

Behavioural Parameters of Circadian Rhythm Are Not Correlated with Dim Light Melatonin Onset: An Observational Study on Healthy Volunteers.

Dim light melatonin onset (DLMO) is considered the most reliable marker of the circadian rhythm phase in humans. DLMO may moderately correlate with sleep onset and sleep offset time. There are no sufficient data about the correlations between DLMO and clinical scales assessing sleep quality and daytime symptoms of poor night sleep. The aim of the study was to determine the association between DLMO and basic sleep parameters from actigraphy and sleep diaries, as well as the association between DLMO and the following insomnia clinical scales: the Athens Insomnia Scale (AIS), Insomnia Severity Index (ISI), Epworth Sleepiness Scale (ESS), and chronotype questionnaires: Morningness-Eveningness Questionnaire (MEQ) and Composite Scale of Morningness (CSM). Participants of the study were healthy volunteers. Sleep parameters were measured by sleep diaries and actigraphy, and the following clinical scales: the AIS, ISI, and ESS, and chronotype questionnaires: MEQ and CSM. DLMO was calculated based on plasma melatonin concentration. The blood samples were collected hourly at five time points between 20:00 and 00:00 during the session in dim red light (<50 lux). Melatonin concertation was determined by LC-MS/MS. Twenty-one volunteers participated in the study. DLMO was calculated in 12 participants. There was a significant correlation between DLMO and ISI (r = 0.60, p = 0.038) and ESS (r = 0.61, p = 0.034). The correlation coefficient between the DLMO and the AIS was also high, however insignificant (r = 0.57, p = 0.054). There were no significant correlations between DLMO and chronotype scales MEQ and CSM. DLMO did not correlate with sleep onset and sleep offset; however, DLMO correlated with the Sleep Fragmentation Index (SFI) (r = 0.67, p = 0.017). DLMO is associated with poorer sleep maintenance, a stronger feeling of insomnia, and sleepiness during the day. Simultaneously, chronotype pattern and circadian rhythm parameters do not correlate with DLMO. Biological circadian rhythm does not reflect the real-life sleep-wake rhythm, indicating that the lifestyle is more often disconnected from the biological clock.

Plasma melatonin night‐time peak levels and 24‐hour area under the curve profile seem higher in AD patients with epileptiform activity than in those without

AbstractBackgroundPlasma melatonin levels drop in elderly, which might become more pronounced in Alzheimer’s disease (AD) as compared to controls.(1) Melatonin can serve as a potential biomarker for AD, given the inverse correlation between cerebrospinal fluid (CSF) melatonin levels and severity of neuropathology (Braak stages).(2) Due to suggested antiepileptic effects(6), melatonin can potentially slow down disease progression as epileptiform activity may contribute to AD disease progression.(3‐5). We here present a preliminary interim analysis of an ongoing study.Aims1. To evaluate melatonin’s potential as biomarker for AD by comparing blood melatonin levels between patients with mild cognitive impairment (MCI) and dementia due to AD and preclinical AD subjects.2. To study the link between melatonin levels and epileptiform activity in AD.MethodsAll subjects underwent a neuropsychological examination, and lumbar puncture for analysis of core AD CSF biomarkers or amyloid brain PET. Subjects belonging to the AD continuum (dementia [n = 7]; MCI [n = 4]; preclinical AD [n = 1]) were diagnosed according to the NIA‐AA research criteria. A subset of subjects (n = 6) underwent 50‐minute magnetoencephalography to detect epileptiform activity. Blood samples were taken multiple times during a 24‐hour period, in in‐hospital controlled circumstances, and were analysed by use of liquid chromatography‐mass spectrometry.ResultsAD patients with epileptiform activity (n = 2) tended to have a higher melatonin 24‐hour area under the curve (AUC) and peak concentration (AUC 517.9pg/ml.h [+/‐140.1pg/ml.h] versus 204.5pg/ml.h [+/‐115.5pg/ml.h]; peak 65.4pg/ml [+/‐14.6pg/ml] versus 25.8pg/ml [+/‐17.5pg/ml]) than AD patients without (n = 4) (p = 0.064 for both; MWU test). There was no statistical difference regarding the melatonin 24‐hour plasma AUC or peak levels between patients with dementia, MCI, preclinical AD subjects (p = 0.760 for both; Kruskall‐Wallis test). We have to interpret these data with caution since sample sizes are still small and more patients are being recruited.ConclusionOn the basis of very preliminary data, 24‐hour plasma melatonin profile and peak plasma melatonin concentration tended to be higher in AD patients with epileptiform activity than in those without. Whether this could be a potential compensatory mechanism against epileptiform activity in AD or whether melatonin could rather have pro‐epileptic effects, remains to be elucidated in future research.

Effect of oral melatonin treatment on insulin resistance and diurnal blood pressure variability in night shift workers. A double-blind, randomized, placebo-controlled study

BackgroundNight shift work is associated with sleep disturbances, obesity, and cardiometabolic diseases. Disruption of the circadian clock system has been suggested to be an independent cause of type 2 diabetes and cardiovascular disease in shift workers. We aimed to improve alignment of circadian timing with social and environmental factors with administration of melatonin. MethodsIn a randomized, placebo-controlled, prospective study, we analysed the effects of 2 mg of sustained-release melatonin versus placebo on glucose tolerance, insulin resistance indices, sleep quality, circadian profiles of plasma melatonin and cortisol, and diurnal blood pressure profiles in 24 rotating night shift workers during 12 weeks of treatment, followed by 12 weeks of wash-out. In a novel design, the time of melatonin administration (at night or in the morning) depended upon the shift schedule. We also compared the baseline profiles of the night shift (NS) workers with 12 healthy non-night shift (NNS)-working controls. ResultsWe found significantly impaired indices of insulin resistance at baseline in NS versus NNS (p < 0.05), but no differences in oral glucose tolerance tests nor in the diurnal profiles of melatonin, cortisol, or blood pressure. Twelve weeks of melatonin treatment did not significantly improve insulin resistance, nor did it significantly affect diurnal blood pressure or melatonin and cortisol profiles. Melatonin administration, however, caused a significant improvement in sleep quality which was significantly impaired in NS versus NNS at baseline (p < 0.001). ConclusionsRotating night shift work causes mild-to-moderate impairment of sleep quality and insulin resistance. Melatonin treatment at bedtime improves sleep quality, but does not significantly affect insulin resistance in rotating night shift workers after 12 weeks of administration.

Involvement of Plasma Melatonin in Medication-Overuse Headache: A Cross-Sectional Study.

Patients with medication-overuse headache (MOH) are often complicated with anxiety, depression, and sleep disorders and are associated with dependence behavior and substance abuse. Melatonin has physiological properties including analgesia, regulation of circadian rhythms, soporific, and antidepressant and affects drug preference and addiction. This study aimed to investigate the role of melatonin in MOH compared with episodic migraine (EM) and healthy controls and to verify the relationship between plasma melatonin levels and psychiatric symptoms. Thirty patients affected by MOH, 30 patients with EM, and 30 matched healthy controls were enrolled. All subjects completed a detailed headache questionnaire and scales including the Hospital Anxiety and Depression Scale (HADS), the Pittsburgh Sleep Quality Index, the Leeds Dependence Questionnaire. Melatonin levels in plasma samples were measured by enzyme immunoassay method. The levels of plasma melatonin were significantly different among 3 groups of subjects (MOH, 7.74 [5.40-9.89]; EM, 9.79 [8.23-10.62]; Control, 10.16 [8.60-17.57]; H = 13.433; P = 0.001). Significantly lower levels of melatonin were found in MOH patients compared with healthy controls ( P = 0.001). The level of plasma melatonin inversely correlated with the scores of HADS-Anxiety ( r = -0.318, P = 0.002), HADS-Depression ( r = -0.368, P < 0.001), Pittsburgh Sleep Quality Index ( r = -0.303, P = 0.004), and Leeds Dependence Questionnaire ( r = -0.312, P = 0.003). This study innovatively detects the plasma melatonin levels in MOH patients and explores the association between melatonin levels and psychiatric symptoms. Melatonin may be potential complementary therapy in the treatment of MOH considering its comprehensive role in multiple aspects of MOH.

Plasma melatonin concentration during the early post-partum period in Thoroughbred mares and their foals.

The authors aimed to determine the plasma melatonin concentration in mares and their new-born foals in the early post-partum period. Blood samples were collected from the jugular vein of 53 mare-foal pairs within twelve hours after parturition. Plasma melatonin levels were measured by ELISA. The melatonin concentration, adjusted for the moment of parturition using a generalised linear model, was34.58 pg mL-1 in mares. It was significantly lower (27.63 pg mL-1) in the new-born foals. However, the melatonin concentration declined differently by the end of the twelve hours, it decreased less in theoffspring than in the mothers. An artificial light supplementation at the end of gestation reduced the melatonin concentration both in mares and their foals by about 10 pg mL-1, compared to the controls. An elevated melatonin production may be related to preparation of mares for parturition and ensures the chances of survival of offspring, therefore the melatonin may reach its peak at the moment of foalingregardless of its actual time. The effect of low melatonin concentration in new-born foals might be associated with the foal's health and subsequent performance. The need to monitor the melatonin concentration in the offspring justifies further studies.

Sleep deprivation soon after recovery from synthetic torpor enhances tau protein dephosphorylation in the rat brain.

Neuronal Tau protein hyperphosphorylation (PPtau) is a hallmark of tauopathic neurodegeneration. However, a reversible brain PPtau occurs in mammals during either natural or "synthetic" torpor (ST), a transient deep hypothermic state that can be pharmacologically induced in rats. Since in both conditions a high sleep pressure builds up during the regaining of euthermia, the aim of this work was to assess the possible role of post-ST sleep in PPtau dephosphorylation. Male rats were studied at the hypothermic nadir of ST, and 3-6h after the recovery of euthermia, after either normal sleep (NS) or total sleep deprivation (SD). The effects of SD were studied by assessing: (i) deep brain temperature (Tb); (ii) immunofluorescent staining for AT8 (phosphorylated Tau) and Tau-1 (non-phosphorylated Tau), assessed in 19 brain structures; (iii) different phosphorylated forms of Tau and the main cellular factors involved in Tau phospho-regulation, including pro- and anti-apoptotic markers, assessed through western blot in the parietal cortex and hippocampus; (iv) systemic factors which are involved in natural torpor; (v) microglia activation state, by considering morphometric variations. Unexpectedly, the reversibility of PPtau was more efficient in SD than in NS animals, and was concomitant with a higher Tb, higher melatonin plasma levels, and a higher frequency of the microglia resting phenotype. Since the reversibility of ST-induced PPtau was previously shown to be driven by a latent physiological molecular mechanism triggered by deep hypothermia, short-term SD soon after the regaining of euthermia seems to boost the possible neuroprotective effects of this mechanism.

THU611 Circadian Misalignment Of Melatonin Secretion In Adrenal Insufficiency (AI)

Abstract Disclosure: M. Darji: None. S. Pannain: None. S. Sam: None. E. Van Cauter: None. E.C. Hanlon: None. Background: Despite glucocorticoid replacement, the mortality risk of AI remains markedly elevated. Under normal conditions, the circadian rhythm of endogenous cortisol levels is a major internal synchronizing signal between central and peripheral circadian clocks. There is increasing evidence indicating that circadian misalignment has a host of adverse effects, including increased cardio-metabolic risk. The present study aimed to assess circadian function in AI patients, as compared to individually-matched healthy subjects, under controlled laboratory conditions. The 24-h profile of melatonin, normally secreted exclusively at night, was used as the marker of central circadian timing. The 24-h profile of leptin was used as a marker of peripheral circadian function. Methods: Plasma cortisol, melatonin, and leptin were measured over a 24-h period every 30-60 minutes under controlled light-dark, sleep-wake and dietary conditions. A best-fit curve was calculated for each individual hormonal profile using a locally weighted nonlinear regression procedure with a window of 4 hours. The peak and the nadir were defined as the maximum and minimum of the best-fit curve, respectively. The amplitude was defined as half of the difference between the peak and the nadir. Sleep was polygraphically recorded. During daytime hours, the participants completed validated questionnaires assessing Vigor, Mood and Sleepiness. Results: Complete data sets were obtained in 15 AI patients (12 women; age: 47.9 ±12.5 years, BMI: 26.6 ± 12.5 kg/m2; mean ± SD). Twelve AI patients were on hydrocortisone treatment (total dose range: 20 to 40mg/day, number of doses: 1-5 /day) and 3 were on prednisone treatment. Controls (n=15, 12 women) were aged 48.5 ±14.5 years with BMI of 26.5 ± 5.4 kg/m2. The amplitude of the cortisol profile was wider in AI patients, relative to controls, with a higher morning peak and an extended and lower nocturnal nadir. Unexpectedly, we observed a marked difference in the melatonin profile in AI patients as compared to controls. A daytime phase of elevated melatonin levels, culminating prior to lights off while the patients were awake, was detected in 9 of the 15 AI patients. The nocturnal elevation persisted with a similar amplitude to that observed in controls but was advanced by 1-2 hours. The 24-h leptin profile was similar in the two groups. The presence of a daytime melatonin peak in AI patients was associated with lower ratings of vigor and mood, and higher ratings of sleepiness. Conclusion: Glucocorticoid treatment to replace the endogenous levels and circadian rhythmicity of cortisol in AI may impact central circadian timing, resulting in daytime, in addition to nighttime, release of melatonin. This finding suggests that exogenous cortisol replacement that does not mimic a normal 24-h rhythm, may cause central circadian dysfunction and contribute to alterations in mood, vigor and sleepiness. Presentation: Thursday, June 15, 2023

Assessment of plasma melatonin profile in summer anestrous buffaloes exhibiting differential fertility following melatonin implants treatment

Plasma melatonin vis-a-vis anestrus or estrus status of buffaloes during summer or winter season (n=50 in each group) suggested its impact on reproductive axis as plasma melatonin activity tended to be higher (P&gt;0.05) in buffaloes exhibiting estrus compared to their anestrous counterparts irrespective of season. The differential reproductive status of these buffaloes was confirmed by history as well as differences (P&lt;0.05) in diameter of largest follicle and luteal profile. Further, for evaluating the impact of melatonin treatment during summer season on reproductive axis, 132 anestrous buffaloes were subcutaneously inserted 2x4 mm absorbable slow-release melatonin implants (18 mg/50 kg b wt) at the base of left ear and 60 buffaloes were used as control. In these buffaloes, ovarian ultrasonography and jugular vein blood sampling was carried out at 7-day interval till day 35 post-treatment or till ovulation, whichever was earlier. Control and implanted buffaloes were subjected to artificial insemination (AI) at overt or induced estrus followed by pregnancy diagnosis at day 90 post-AI. In treatment group, an increase (P&lt;0.05) in plasma melatonin was recorded in all the buffaloes, exhibiting differential fertility status, during post-treatment study period compared to their pre-treatment and control group values. However, within treatment group, there was no difference (P&gt;0.05) in plasma melatonin between ovulatory or non-ovulatory as well as between pregnant or non-pregnant counterparts. Moreover, plasma melatonin within control buffaloes remained similar (P&gt;0.05) throughout the study period irrespective of differential exhibition of fertility. It can be concluded that factors other than circulating melatonin are also involved in the display of differential fertility in terms of initiation of ovarian cyclicity/ovulation or ability to conceive in summer anestrous buffaloes.

Melatonin-Mediated Inhibitory Effect on Hyperimmune Status of Acquired Aplastic Anemia

To evaluate the expression level of melatonin and its effects on immune function in aplastic anemia (AA) patients. The enzyme-linked immunosorbent assay (ELISA) was used to detect the plasma levels of melatonin in AA patients, and the correlation between melatonin levels and laboratory indexs was analyzed. The activation, proliferation, and apoptosis of T cells from AA patients were analyzed by flow cytometry with or without melatonin in vitro. The plasma levels of melatonin in AA patients were significantly lower compared with healthy controls (HC) (12.23 pg/ml vs 20.04 pg/ml, P < 0.01), while the plasma melatonin levels of AA patients in remission group after immunosuppressive therapy (IST) were significantly higher than those in non-remission group (29.16 pg/ml vs 11.73 pg/ml, P =0.04). Moreover, the melatonin levels were positively correlated with platelets (r =0.49), the absolute reticulocyte count (r =0.45), and the percentage of neutrophils (r =0.43). Meanwhile, there was a negative correlation between melatonin levels and the percentages of lymphocytes (r =-0.45). The expressions of CD25 and CD69 in both CD4+ and CD8+ T cells from AA patients were remarkably inhibited by melatonin in vitro (all P < 0.05). When cultured with melatonin, the proliferation rates of both CD4+ and CD8+ T cells from AA patients were markedly suppressed (P =0.01 andP < 0.01). The plasma levels of melatonin were decreased in AA patients, which might play an important role in the mechanism of immunological abnormalities. The hyperimmune status of AA patients could be partially ameliorated by melatonin in vitro.

Differential responses to artificial photoperiods of the rising and falling phases of human melatonin rhythm are consistent with a dual oscillator hypothesis.

Circadian rhythms and sleep-wake cycles were measured in volunteers staying singly in temporal isolation unit where they were exposed to artificial short and long light-dark (LD) cycles for 7 days. The long day consisted of 16-h light and 8-h dark (LD 16:8) and the short day consisted of 8-h light and 16-h dark (LD 8:16). During the light period, bright light of approximately 5,000 lux was given from the ceiling and during the dark period there was no illumination. Sleep was monitored by bed sensors, wrist actiwatch, and polysomnography (PSG) on the first and last nights of the schedule. Sleep length was significantly longer under LD 8:16 than under LD 16:8 and the sleep quality estimated by PSG was worse under LD 8:16 than under LD 16:8, which were comparable to natural seasonality in sleep. The circadian rhythm in plasma melatonin was measured in dim light (10 lux) before and after the LD exposures. The nocturnal melatonin secretion (NMS) was significantly longer after LD 8:16 than after LD 16:8 due to differential phase shifts of the rising and falling phases of NMS. After LD 8:16, the falling phase was much advanced than the rising phase, whereas after LD 16:8 the rising phase was much delayed than the falling phase, resulting in the NMS compression. These results indicate that the light sensitivity in terms of phase shifting is different in the two circadian phases, supporting a dual oscillator hypothesis with different phase-response curves for light in the human circadian system.NEW & NOTEWORTHY The present study demonstrated differential light responsiveness of the rising and falling phases of nocturnal melatonin secretion in human subjects exposed to artificial long (LD 16:8) and short days (LD 8:16) and suggested the involvement of different oscillators under these phases. The findings well mimicked the seasonality of the circadian rhythms in nature and consisted with the evening/morning dual oscillator hypothesis proposed originally for nocturnal rodents, providing a new concept for the human circadian system.

Association between the plasma concentration of melatonin and behavioral temperament in horses

Aggression in horses may engender serious accidents during riding and non-riding activities. Hence, predicting the temperament of horses is essential for selecting suitable horses and ensuring safety during activity. In certain animals, such as hamsters, plasma melatonin concentrations have been correlated with aggressive behavior. However, whether this relationship applies to horses remains unclear. To address this research gap, this study aimed to evaluate differences in the plasma melatonin concentrations among horses of different breeds, ages, and sexes and examine the correlation between plasma melatonin concentrations and the temperament of the horses, including docility, affinity, dominance, and trainability. Blood samples from 32 horses were collected from the Horse Industry Complex Center of Jeonju Kijeon College. The docility, affinity, dominance, and trainability of the horses were assessed by three professional trainers who were well-acquainted with the horses. Plasma melatonin concentrations were measured using an enzyme-linked immunosorbent assay. The consequent values were compared between the horses of different breeds, ages, and sexes using three-way analysis of variance and least significant difference post hoc test. Linear regression analysis was employed to identify the relationship between plasma melatonin concentrations and docility, affinity, dominance, and trainability. The results showed that the plasma melatonin concentrations significantly differed with breeds in Thoroughbred and cold-blooded horses. However, there were no differences in the plasma melatonin concentrations between the horse ages and sexes. Furthermore, plasma melatonin concentrations did not exhibit a significant correlation with the ranking of docility, affinity, dominance, and trainability.

Melatonin attenuates sepsis-induced acute kidney injury by promoting mitophagy through SIRT3-mediated TFAM deacetylation

ABSTRACT A growing number of studies have shown that melatonin is a potent agonist of SIRT3 (sirtuin 3) and effectively protects mitochondria, suggesting melatonin as a promising therapeutic drug to treat sepsis-induced acute kidney injury (SAKI). In this study, we first included 48 sepsis patients for cross-sectional analysis and the result revealed that plasma melatonin levels are inversely proportional to the mitochondrial injury of renal tubular epithelial cells and directly proportional to the acute kidney injury recovery in sepsis patients. We further explored the effects of exogenous melatonin on SAKI and its mechanism in animal model of cecal ligation and puncture-treated mice, and cellular model of LPS-challenged HK-2 cells. The results demonstrate that the protective effect of melatonin on the progression of SAKI depends on SIRT3 activation as well as mitophagic flux. Mechanistically, TFAM (transcription factor A, mitochondrial)-K154 site deacetylation via SIRT3 is indispensable for melatonin-enhanced mitophagic flux on SAKI. Together, our study unveils a previously unappreciated mechanism of melatonin as agonists of SIRT3 to hold promise for treatment of patients with SAKI. Abbreviations AKI: acute kidney injury; ATP: adenosine triphosphate; BUN: blood urea nitrogen; CLP: cecal ligation and puncture; eGFR: estimated glomerular filtration rate; H&E: hematoxylin and eosin staining; LCN2/NGAL: lipocalin 2; LPS: lipopolysaccharide; LTL: lotus tetragonolobus lectin; mKeima: mitochondria-targeted Keima; mtDNA: mitochondrial DNA; PAS: periodic acid – Schiff staining; RTECs: renal tubular epithelial cells; SAKI: sepsis-induced acute kidney injury; Scr: serum creatinine; SIRT3: sirtuin 3; TFAM: transcription factor A, mitochondrial; TMRE: tetramethylrhodamine.