The therapeutic or prophylactic effect of exogenous melatonin against depression and depressive symptoms: a systematic review and meta-analysis

Effects of melatonin intake on depression and anxiety in postmenopausal women: a systematic review and meta-analysis of randomised controlled trials

We conducted a systematic review and meta-analysis of randomised controlled trials (RCTs) evaluating the effects of melatonin intake on depression and anxiety in postmenopausal women. To identify RCTs examining the effect of melatonin supplementation on depression and anxiety scores in postmenopausal women, a comprehensive electronic search was conducted via the Cochrane Central Register of Controlled Trials, Science direct, Google Scholar, PubMed, Medline, Scopus and Web of Science databases using the keywords ("melatonin" OR "N-acetyl serotonin") AND ("menopause" OR "climacteric") AND ("depression" OR "anxiety"). The search strategy was applied to articles published between January 2000 and April 2023. The Cochrane tool was used to evaluate the bias risk in RCTs. For the meta-analysis, fixed effect models and random effect models were employed based on heterogeneity. Preferred Reporting Items for Systematic Reviews and Meta-Analysis in Our Study guidelines were followed. Five RCTs were included in the study, with a total sample size of 441 (experimental: 227 and control: 214). When the effect of melatonin use on depression in menopausal women was analysed, it was found that melatonin significantly reduced menopausal depression (SMD - 0.166, CI =  - 0.288/ - 0.045, p < 0.05). When the effect of melatonin use on anxiety in postmenopausal women was analysed, it was found that melatonin significantly improved menopausal anxiety (SMD - 0.806, CI = 1.491/ - 0.120, p < 0.05). Melatonin is promising as a potential treatment to help depression and anxiety in the postmenopausal period. More high-quality studies are needed to determine their safety.

Significance of Melatonin in the Regulation of Circadian Rhythms and Disease Management

Melatonin, the 'hormone of darkness' is a neuronal hormone secreted by the pineal gland and other extra pineal sites. Responsible for the circadian rhythm and seasonal behaviour of vertebrates and mammals, melatonin is responsible for regulating various physiological conditions and the maintenance of sleep, body weight and the neuronal activities of the ocular sites. With its unique amphiphilic structure, melatonin can cross the cellular barriers and elucidate its activities in the subcellular components, including mitochondria. Melatonin is a potential scavenger of oxygen and nitrogen-reactive species and can directly obliterate the ROS and RNS by a receptor-independent mechanism. It can also regulate the pro- and anti-inflammatory cytokines in various pathological conditions and exhibit therapeutic activities against neurodegenerative, psychiatric disorders and cancer. Melatonin is also found to show its effects on major organs, particularly the brain, liver and heart, and also imparts a role in the modulation of the immune system. Thus, melatonin is a multifaceted candidate with immense therapeutic potential and is still considered an effective supplement on various therapies. This is primarily due to rectification of aberrant circadian rhythm by improvement of sleep quality associated with risk development of neurodegenerative, cognitive, cardiovascular and other metabolic disorders, thereby enhancing the quality of life.

Melatonin alters the excitability of mouse cerebellar granule neurons by inhibiting voltage-gated sodium, potassium, and calcium channels

Besides its role in the circadian rhythm, the pineal gland hormone melatonin (MLT) also possesses antiepileptogenic, antineoplastic, and cardioprotective properties, among others. The dosages necessary to elicit beneficial effects in these diseases often far surpass physiological concentrations. Although even high doses of MLT are considered to be largely harmless to humans, the possible side effects of pharmacological concentrations are so far not well investigated. In the present study, we report that pharmacological doses of MLT (3 mM) strongly altered the electrophysiological characteristics of cultured primary mouse cerebellar granule cells (CGCs). Using whole-cell patch clamp and ratiometric Ca2+ imaging, we observed that pharmacological concentrations of MLT inhibited several types of voltage-gated Na+ , K+ , and Ca2+ channels in CGCs independently of known MLT-receptors, altering the character and pattern of elicited action potentials (APs) significantly, quickly and reversibly. Specifically, MLT reduced AP frequency, afterhyperpolarization, and rheobase, whereas AP amplitude and threshold potential remained unchanged. The altered biophysical profile of the cells could constitute a possible mechanism underlying the proposed beneficial effects of MLT in brain-related disorders, such as epilepsy. On the other hand, it suggests potential adverse effects of pharmacological MLT concentrations on neurons, which should be considered when using MLT as a pharmacological compound.

Effect of melatonin in patients with low anterior resection syndrome (MELLARS): a study protocol for a randomised, placebo-controlled, crossover trial

INTRODUCTION

After rectal cancer surgery, a majority of patients suffer from sequelae known as low anterior resection syndrome (LARS). It is a collection of symptoms consisting of flatus and/or stool incontinence, evacuation frequency, re-evacuation and urgency. The circadian hormone, melatonin, has shown to possess anti-inflammatory properties, and in high doses, it reduces bowel movements. The aim of the study is to investigate if locally administered melatonin has an alleviating effect on LARS. Secondarily, the effect of melatonin on bowel movements, other patient-reported symptoms, quality of life, depression, anxiety, sleep disturbances, motilin levels and rectal mucosa histology will be examined.

METHODS AND ANALYSIS

This is a randomised, placebo-controlled, double-blinded, two-period crossover trial. The participants are randomised to 28 days of 25 mg melatonin administered rectally via an enema daily (or placebo) followed by a 28-day washout and then 28 days of placebo (or melatonin). Three participants will be included in an internal feasibility test. They will receive 25 mg of melatonin daily for 28 days. Data from these participants will be used to assess the feasibility of the rectally administered melatonin and to analyse the course of recruitment and outcome measurements. Afterwards, 18 participants will be included in the crossover trial. The severity of the LARS symptoms will be evaluated using the LARS Score on the first and last day of each treatment period.

ETHICS AND DISSEMINATION

The Regional Ethics Committee, the Danish Medicines Agency and the Data and Development Support in Region Zealand approved this study. The study will be performed according to the Helsinki II declaration. Written informed consent will be obtained from all participants. The results of the study will be submitted to peer-reviewed journals for publication and presented at congresses.

TRIAL REGISTRATION NUMBERS

EudraCT Registry (2020-004442-11) and ClinicalTrial.gov Registry (NCT05042700).

Chronic Administration of Melatonin: Physiological and Clinical Considerations

Background: Exogenous melatonin is commonly used to treat insomnia, other sleep problems, and numerous medical illnesses, including Alzheimer’s disease, autism spectrum disorder, and mild cognitive impairment in adults and children. There is evolving information regarding issues with the use of chronic melatonin. Methods: The present investigation was a narrative review. Results: Melatonin usage has risen dramatically in recent years. Many countries only allow melatonin prescriptions. In the United States (U.S.), it is classified as a dietary supplement accessible over the counter and can be derived from animals, microorganisms, or, most commonly, made synthetically. No regulatory agency oversees its manufacturing or sale in the U.S. melatonin concentration of marketed preparations varies widely between product labels and manufacturers. Melatonin’s ability to induce sleep is detectable. However, it is modest for most people. Sleep length appears to be less important in sustained-release preparations. The optimal dosage is unknown, and routinely used amounts vary substantially. Melatonin’s short-term negative effects are minimal, resolve at medicine cessation, and do not usually prevent usage overall. Much research on long-term melatonin administration has found no difference between exogenous melatonin and placebo in terms of long-term negative effects. Conclusion: Melatonin at low to moderate dosages (approximately 5–6 mg daily or less) appears safe. Long-term usage appears to benefit certain patient populations, such as those with autism spectrum disorder. Studies investigating potential benefits in reducing cognitive decline and increased longevity are ongoing. However, it is widely agreed that the long-term effects of taking exogenous melatonin have been insufficiently studied and warrant additional investigation.

Current Insights into the Risks of Using Melatonin as a Treatment for Sleep Disorders in Older Adults

Exogenous melatonin is commonly used for sleep disorders in older adults, and its use is increasing over time. It appears to have modest efficacy in treating insomnia and circadian rhythm sleep-wake disorders. Melatonin is commonly perceived to be a safe alternative to other hypnotics and is available without prescription in some jurisdictions. New evidence suggests that endogenous melatonin has pleomorphic effects on multiple organ systems, many of which are poorly understood. This narrative review summarizes the current evidence regarding the safety of melatonin in older adults (defined by age over 65 years). Melatonin appears to have a favorable safety profile in this population, however there is a dearth of evidence regarding the safety of prolonged use. There are several factors which increase the risk of adverse effects of melatonin in older adults, and these should be taken into consideration when prescribing to this population.

Physiological and pharmacological perspectives of melatonin

The pineal gland is a interface between light-dark cycle and shows neuro-endocrine functions. Melatonin is the primary hormone of pineal gland, secreted at night. The night-time melatonin peak regulates the physiological functions at dark. Melatonin has several unique features as it synchronises internal rhythm with daily and seasonal variations, regulates circadian rhythm and sleep-wake cycle. Physiologically melatonin involves in detoxification of free radicals, immune functions, neuro-protection, oncostatic effects, cardiovascular functions, reproduction, and foetal development. The precise functions of melatonin are exhibited by specific receptors. In relation to pathophysiology, impaired melatonin secretion promotes sleep disorder, cancer progression, type-2 diabetes, and neurodegenerative diseases. Several reports have highlighted the therapeutic benefits of melatonin specially related to cancer protection, sleep disorder, psychiatric disorders, and jet lag problems. This review will touch the most of the area of melatonin-oriented health impacts and its therapeutic aspects.

Understanding the basis of major depressive disorder in oncological patients: Biological links, clinical management, challenges, and lifestyle medicine

In recent years, the incidence of different types of cancer and patient survival have been rising, as well as their prevalence. The increase in survival in recent years exposes the patients to a set of stressful factors such as more rigorous follow-up and more aggressive therapeutic regimens that, added to the diagnosis of the disease itself, cause an increase in the incidence of depressive disorders. These alterations have important consequences for the patients, reducing their average survival and quality of life, and for these reasons, special emphasis has been placed on developing numerous screening tests and early recognition of depressive symptoms. Despite that cancer and major depressive disorder are complex and heterogeneous entities, they also share many critical pathophysiological mechanisms, aiding to explain this complex relationship from a biological perspective. Moreover, a growing body of evidence is supporting the relevant role of lifestyle habits in the prevention and management of both depression and cancer. Therefore, the present study aims to perform a thorough review of the intricate relationship between depression and cancer, with a special focus on its biological links, clinical management, challenges, and the central role of lifestyle medicine as adjunctive and preventive approaches to improve the quality of life of these patients.

Tryptophan metabolites in depression: Modulation by gut microbiota

Clinical depression is a multifactorial disorder and one of the leading causes of disability worldwide. The alterations in tryptophan metabolism such as changes in the levels of serotonin, kynurenine, and kynurenine acid have been implicated in the etiology of depression for more than 50 years. In recent years, accumulated evidence has revealed that gut microbial communities, besides being essential players in various aspects of host physiology and brain functioning are also implicated in the etiology of depression, particularly through modulation of tryptophan metabolism. Therefore, the aim of this review is to summarize the evidence of the role of gut bacteria in disturbed tryptophan metabolism in depression. We summed up the effects of microbiota on serotonin, kynurenine, and indole pathway of tryptophan conversion relevant for understanding the pathogenesis of depressive behavior. Moreover, we reviewed data regarding the therapeutic effects of probiotics, particularly through the regulation of tryptophan metabolites. Taken together, these findings can open new possibilities for further improvement of treatments for depression based on the microbiota-mediated modulation of the tryptophan pathway.

Night shift hormone: How does melatonin affect depression?

Melatonin is the main hormone secreted by the pineal gland that modulates the circadian rhythm and mood. Previous studies have shown the therapeutic effects of melatonin, or its important analogue, agomelatine, on depression. In this review study, we aimed to discuss the potential mechanisms of melatonin involved in the treatment of depression. It was noted that disrupted circadian rhythm can lead to depressive state, and melatonin via regulating circadian rhythm shows a therapeutic effect. It was also noted that melatonin induces antidepressant effects via promoting antioxidant system and neurogenesis, and suppressing oxidative stress, neuroinflammation, and apoptosis. The interaction effect between melatonin or agomelatine and serotonergic signaling has a significant effect on depression. It was noted that the psychotropic effects of agomelatine are induced by the synergistic interaction between melatonin and 5-HT_2C receptors. Agomelatine also interacts with glutamatergic signaling in brain regions involved in regulating mood and circadian rhythm. Interestingly, it was concluded that melatonin exerts both pro- and anti-inflammatory effects, depending on the grade of inflammation. It was suggested that synergistic interaction between melatonin and 5-HT_2C receptors may be able to induce therapeutic effects on other psychiatric disorders. Furthermore, dualistic role of melatonin in regulating inflammation is an important point that can be examined at different levels of inflammation in animal models of depression.

The Therapeutic Effect of Exogenous Melatonin on Depressive Symptoms: A Systematic Review and Meta-Analysis

BACKGROUND

Depression-related mortality and morbidity pose growing public health burdens worldwide. Although the therapeutic effect of exogenous melatonin on depression has been investigated, findings remain inconsistent. We conducted this systematic review and meta-analysis to clarify the effectiveness of melatonin in the treatment of depression, including primary and secondary depression symptoms.

METHODS

We searched the online databases of PubMed, EMBASE, and the Cochrane Library for original studies published up to May 2021. We used STATA 14.0 software to synthesize the results of included studies. To evaluate the effectiveness of melatonin, we calculated the standardized mean differences (SMDs) and 95% confidence intervals (CIs) of depression scores between the melatonin and placebo groups.

RESULTS

Our literature search returned 754 publications, among which 19 studies with 1,178 patients (715 women, 463 men; mean age: 56.77 years) met inclusion criteria. Melatonin dosages ranged from 2 to 25 mg per day; treatment durations were between 10 days and 3.5 years. Our synthesized results showed that melatonin was not found significantly beneficial for alleviating depressive symptoms (SMD = -0.17, 95% CI = [-0.38, 0.05]). Subgroup analysis demonstrated that the decrease in depression scores measured with the Beck Depression Inventory (BDI) was significant (SMD = -0.52, 95% CI = [-0.73, -0.31]).

CONCLUSIONS

There is very limited evidence for effects of melatonin on depression.

Role of Melatonin in the Management of Sleep and Circadian Disorders in the Context of Psychiatric Illness

PURPOSE OF REVIEW

We present a review of research on the role of melatonin in the management of sleep and circadian disorders, stressing current overall view of the knowledge across psychiatric disorders.

RECENT FINDINGS

Dysregulation of sleep and circadian rhythms has been established in several psychiatric and neurocognitive disorders for long. Recent research confirms this finding consistently across disorders. The secretion of melatonin in schizophrenia and neurocognitive disorders is reduced due to a smaller volume and enlarged calcification of the pineal gland. On the other hand, melatonin dysregulation in bipolar disorder may be more dynamic and caused by light-sensitive melatonin suppression and delayed melatonin secretion. In both cases, exogenous melatonin seems indicated to correct the dysfunction. However, a very limited number of well-designed trials with melatonin to correct sleep and circadian rhythms exist in psychiatric disorders, and the evidence for efficacy is robust only in autism, attention deficit hyperactivity disorder (ADHD), and neurocognitive disorders. This topic has mainly not been of interest for recent work and well-designed trials with objective circadian parameters are few. Overall, recent studies in psychiatric disorders reported that melatonin can be effective in improving sleep parameters such as sleep onset latency, sleep efficiency, and sleep quality. Recent meta-analysis suggests that optimal dosage and dosing time might be important to maximize the efficacy of melatonin. The knowledge base is sufficient to propose well-designed, larger trials with circadian parameters as inclusion and outcome criteria. Based on the partly fragmentary information, we propose testing efficacy in disorders with neurocognitive etiopathology with later and higher dosing, and affective and anxiety disorders with lower and earlier dosing of melatonin. Melatonin is promising for the correction of sleep and circadian abnormalities in psychiatric disorders. However, research results on its effect are still few and need to be accumulated. For effective use of melatonin, it is necessary to consider the appropriate dosage and administration time, depending on the individual abnormality of sleep and circadian rhythms.

Melatonin: From Neurobiology to Treatment

Melatonin, the major regulator of the sleep/wake cycle, also plays important physiological and pharmacological roles in the control of neuronal plasticity and neuroprotection. Accordingly, the secretion of this hormone reaches the maximal extent during brain development (childhood-adolescence) while it is greatly reduced during aging, a condition associated to altered sleep pattern and reduced neuronal plasticity. Altogether, these properties of melatonin have allowed us to demonstrate in both experimental models and clinical studies the great chronobiotic efficacy and sleep promoting effects of exogenous melatonin. Thus, the prolonged release formulation of melatonin, present as a drug in the pharmaceutical market, has been recently recommended for the treatment of insomnia in over 55 years old subjects.

Exploring the Role of Nutraceuticals in Major Depressive Disorder (MDD): Rationale, State of the Art and Future Prospects

Major depressive disorder (MDD) is a complex and common disorder, with many factors involved in its onset and development. The clinical management of this condition is frequently based on the use of some pharmacological antidepressant agents, together with psychotherapy and other alternatives in most severe cases. However, an important percentage of depressed patients fail to respond to the use of conventional therapies. This has created the urgency of finding novel approaches to help in the clinical management of those individuals. Nutraceuticals are natural compounds contained in food with proven benefits either in health promotion or disease prevention and therapy. A growing interest and economical sources are being placed in the development and understanding of multiple nutraceutical products. Here, we summarize some of the most relevant nutraceutical agents evaluated in preclinical and clinical models of depression. In addition, we will also explore less frequent but interest nutraceutical products which are starting to be tested, also evaluating future roads to cover in order to maximize the benefits of nutraceuticals in MDD.

Effects Of Exogenous Melatonin On Sleep And Circadian Rhythms In Women With Premenstrual Dysphoric Disorder

We previously found normal polysomnographic (PSG) sleep efficiency, increased slow wave sleep (SWS) and a blunted melatonin secretion in women with premenstrual dysphoric disorder (PMDD) compared to controls. Here, we investigated the effects of exogenous melatonin in five patients previously studied. They took 2 mg of slow-release melatonin 1 hour before bedtime during their luteal phase (LP) for three menstrual cycles. At baseline, patients spent every third night throughout one menstrual cycle sleeping in the laboratory. Measures included morning urinary 6-sulfatoxymelatonin (aMt6), PSG sleep, nocturnal core body temperature (CBT), visual analogue scale for mood (VAS-Mood), Prospective Record of the Impact and Severity of Menstrual Symptoms (PRISM), and ovarian hormones. Participants also underwent two 24-hour intensive physiological monitoring (during the follicular phase and LP) in time-isolation/constant conditions to determine 24-hour plasma melatonin and CBT rhythms. The same measures were repeated during their third menstrual cycle of melatonin administration. In the intervention condition compared to baseline, we found increased urinary aMt6 (p<0.001), reduced objective SOL (p=0.01), reduced SWS (p<0.001) and increased Stage 2 sleep (p<0.001). Increased urinary aMt6 was associated with reduced SWS (r=-0.51, p<0.001). Circadian parameters derived from 24-hour plasma melatonin and CBT did not differ between conditions, except for an increased melatonin mesor in the intervention condition (p=0.01). Ovarian hormones were comparable between the conditions (p≥0.28). Symptoms improved in the intervention condition, as measured by the VAS-Mood (p=0.02) and the PRISM (p<0.001). These findings support a role for disturbed melatonergic system in PMDD that can be partially corrected by exogenous melatonin.

Melatonin and Depression: A Translational Perspective From Animal Models to Clinical Studies

Daily rhythm of melatonin synchronizes the body to the light/dark environmental cycle. Several hypotheses have been raised to understand the intersections between melatonin and depression, in which changes in rest-activity and sleep patterns are prominent. This review describes key experimental and clinical evidence that link melatonin with the etiopathology and symptomatology of depressive states, its role in the follow up of therapeutic response to antidepressants, as well as the clinical evidence of melatonin as MDD treatment. Melatonin, as an internal temporal cue contributing to circadian organization and best studied in the context of circadian misalignment, is also implicated in neuroplasticity. The monoaminergic systems that underly MDD and melatonin production overlap. In addition, the urinary metabolite 6-sulfatoxymelatonin (aMT6) has been proposed as biomarker for antidepressant responders, by revealing whether the blockage of noradrenaline uptake has taken place within 24 h from the first antidepressant dose. Even though animal models show benefits from melatonin supplementation on depressive-like behavior, clinical evidence is inconsistent vis-à-vis prophylactic or therapeutic benefits of melatonin or melatonin agonists in depression. We argue that the study of melatonin in MDD or other psychiatric disorders must take into account the specificities of melatonin as an integrating molecule, inextricably linked to entrainment, metabolism, immunity, neurotransmission, and cell homeostasis.

Effects of exogenous melatonin on sleep quality and menopausal symptoms in menopausal women: a systematic review and meta-analysis of randomized controlled trials

IMPORTANCE

Because of the bothersome symptoms during women's menopausal period and the severe side effects of hormone therapy, it is meaningful to find new breakthroughs in improving menopausal women's quality of life.

OBJECTIVE

We performed a systematic review and meta-analysis of randomized controlled trials (RCTs) evaluating melatonin intake on the improvement of sleep quality, general menopausal symptom, mood states, as well as interaction of estradiol levels and body mass index (BMI) in menopausal women.

EVIDENCE REVIEW

We used the search terms "melatonin" together with "menopause" or "post-menopause" or "peri-menopause" in multiple databases online including PubMed, Web of Science, Embase, Clinical trial, Cochrane Library, and China National Knowledge Infrastructure from the first publication year to October 2020. Interesting data included characteristics of the study design, study participants, intervention, and outcome measures. Risk of biases in RCTs was evaluated with the Cochrane tool. Fixed-effect models and random-effect models were used for meta-analysis according to heterogeneity. Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines were followed in our study.

FINDINGS

Eight cohorts (n = 812) evaluating the effects of melatonin in menopausal women were included. Melatonin was used in every study with differences existing in dose (1 mg - 5 mg) and duration (3 to 12 mo). Improved physical symptoms (standard mean difference [SMD] -0.376; 95% CI, -0.599 to -0.153, P = 0.001) merged in four RCTs. Melatonin treatment resulted in no benefits to sleep quality (SMD -0.659; 95% CI, -1.535 to 0.217, P = 0.141) and general menopause symptoms (SMD -0.625; 95% CI, -1.354 to 0.105, P = 0.093) in four and three RCTs, respectively. More specifically, melatonin did not solve the psychological (SMD -0.026; 95% CI, -0.372 to 0.321, P = 0.884, I2 = 70.3%), sexual (SMD -0.661; 95% CI, -1.416 to 0.093, P = 0.086) and vasomotor (SMD -0.256; 95% CI, -0.701 to 0.188, P = 0.258) issues. No significant changes were observed in anxiety (SMD 0.018; 95% CI, -0.519 to 0.556, P = 0.946), depression (SMD 0.133; 95% CI, -0.435 to 0.702, P = 0.646), BMI (weighted mean difference 0.029 kg/m2; 95% CI, -0.183 to 0.240, P = 0.790) or estradiol levels (weighted mean difference 0.016 pg/mL; 95% CI, -1.220 to 1.252, P = 0.980).

CONCLUSIONS

Melatonin seems to improve physical symptoms in menopausal women, but the general menopausal symptoms, sleep quality, mood state, estradiol levels, and BMI did not improve under melatonin intervention. However, multiple large-scale clinical randomized trials are needed to validate our conclusions.

Agomelatine, A Potential Multi-Target Treatment Alternative for Insomnia, Depression, and Osteoporosis in Postmenopausal Women: A Hypothetical Model

Insomnia, which is associated with menopausal depression, is a common symptom of menopause. Both symptoms have a common etiology, and can affect each other significantly. Pharmacological interventions, including hypnotics and antidepressants, and non-pharmacological therapies are generally administered in clinical practice for insomnia treatment. As another menopausal disorder, osteoporosis is described as a disease of low bone mineral density (BMD), affecting nearly 200 million women worldwide. Postmenopausal osteoporosis is common among middle-aged women. Since postmenopausal osteoporosis mainly results from low estrogen levels, menopausal hormone therapy (HT) is considered the first-line option for the prevention of osteoporosis during the menopausal period. However, almost no study has evaluated novel treatments for the combined prevention of insomnia, depression, and osteoporosis. Hence, it is necessary to develop new multi-target strategies for the treatment of these disorders to improve the quality of life during this vulnerable period. Melatonin is the major regulator of sleep, and it has been suggested to be safe and effective for bone loss therapy by MT-2 receptor activity. As a result, we hypothesize that agomelatine, an MT-1 and MT-2 receptor agonist and 5-HT_2C receptor antagonist, holds promise in the combined treatment of insomnia, depression, and osteoporosis in middle-aged women during menopause.

Insights into Potential Targets for Therapeutic Intervention in Epilepsy

Epilepsy is a chronic brain disease that affects approximately 65 million people worldwide. However, despite the continuous development of antiepileptic drugs, over 30% patients with epilepsy progress to drug-resistant epilepsy. For this reason, it is a high priority objective in preclinical research to find novel therapeutic targets and to develop effective drugs that prevent or reverse the molecular mechanisms underlying epilepsy progression. Among these potential therapeutic targets, we highlight currently available information involving signaling pathways (Wnt/β-catenin, Mammalian Target of Rapamycin (mTOR) signaling and zinc signaling), enzymes (carbonic anhydrase), proteins (erythropoietin, copine 6 and complement system), channels (Transient Receptor Potential Vanilloid Type 1 (TRPV1) channel) and receptors (galanin and melatonin receptors). All of them have demonstrated a certain degree of efficacy not only in controlling seizures but also in displaying neuroprotective activity and in modifying the progression of epilepsy. Although some research with these specific targets has been done in relation with epilepsy, they have not been fully explored as potential therapeutic targets that could help address the unsolved issue of drug-resistant epilepsy and develop new antiseizure therapies for the treatment of epilepsy.

Melatonin mitigates hippocampal and cognitive impairments caused by prenatal irradiation

Formation of new neurons and glial cells in the brain is taking place in mammals not only during prenatal embryogenesis but also during adult life. As an enhancer of oxidative stress, ionizing radiation represents a potent inhibitor of neurogenesis and gliogenesis in the brain. It is known that the pineal hormone melatonin is a potent free radical scavenger and counteracts inflammation and apoptosis in brain injuries. The aim of our study was to establish the effects of melatonin on cells in the hippocampus and selected forms of behaviour in prenatally irradiated rats. The male progeny of irradiated (1 Gy of gamma rays; n = 38) and sham-irradiated mothers (n = 19), aged 3 weeks or 2 months, were used in the experiment. Melatonin was administered daily in drinking water (4 mg/kg b. w.) to a subset of animals from each age group. Prenatal irradiation markedly suppressed proliferative activity in the dentate gyrus in both age groups. Melatonin significantly increased the number of proliferative BrdU-positive cells in hilus of young irradiated animals, and the number of mature NeuN-positive neurons in hilus and granular cell layer of the dentate gyrus in these rats and in CA1 region of adult irradiated rats. Moreover, melatonin significantly improved the spatial memory impaired by irradiation, assessed in Morris water maze. A significant correlation between the number of proliferative cells and cognitive performances was found, too. Our study indicates that melatonin may decrease the loss of hippocampal neurons in the CA1 region and improve cognitive abilities after irradiation.

The effects of melatonin supplementation on mental health, metabolic and genetic profiles in patients under methadone maintenance treatment

This investigation was designed to determine the effect of melatonin supplementation on mental health parameters, metabolic and genetic profiles in patients under methadone maintenance treatment (MMT). This randomized, double-blind, placebo-controlled, clinical trial was conducted among 54 patients under MMT. Participants were randomly allocated to receive either 10 mg melatonin (2 melatonin capsules, 5 mg each) (n = 26) or placebo (n = 28) once a day, 1 hour before bedtime for 12 weeks. Melatonin supplementation significantly decreased Pittsburgh Sleep Quality Index (β -4.08; 95 percent CI, -5.51, -2.65; P < 0.001), Beck Depression Inventory index (β -5.46; 95% CI, -8.92, -2.00; P = 0.003) and Beck Anxiety Inventory index (β -3.87; 95% CI, -5.96, -1.77; P = 0.001) and significantly increased International Index of Erectile Functions (β 5.59; 95% CI, 1.76, 9.42; P = 0.005) compared with the placebo. Subjects who received melatonin supplements had significantly lower serum insulin levels (β -2.53; 95% CI, -4.48, -0.59; P = 0.01), homeostasis model of assessment-insulin resistance (β -0.56; 95% CI, -1.03, -0.09; P = 0.01) and higher quantitative insulin sensitivity check index (β 0.01; 95% CI, 0.004, 0.02; P = 0.009) and HDL-cholesterol levels (β 3.71; 95% CI, 1.77, 5.64; P = 0.002) compared to placebo. Additionally, melatonin intake resulted in a significant reduction in serum high sensitivity C-reactive protein (β -0.15; 95% CI, -0.27, -0.02; P = 0.02), malondialdehyde (β -0.31; 95% CI, -0.57, -0.05; P = 0.02) and protein carbonyl (β -0.06; 95% CI, -0.09, -0.04; P < 0.001). This trial indicated that taking melatonin supplements for 12 weeks by patients under MMT had beneficial effects on their mental health metabolic profiles.

Perspectives in affective disorders: Clocks and sleep

Mood disorders are often characterised by alterations in circadian rhythms, sleep disturbances and seasonal exacerbation. Conversely, chronobiological treatments utilise zeitgebers for circadian rhythms such as light to improve mood and stabilise sleep, and manipulations of sleep timing and duration as rapid antidepressant modalities. Although sleep deprivation ("wake therapy") can act within hours, and its mood-elevating effects be maintained by regular morning light administration/medication/earlier sleep, it has not entered the regular guidelines for treating affective disorders as a first-line treatment. The hindrances to using chronotherapeutics may lie in their lack of patentability, few sponsors to carry out large multi-centre trials, non-reimbursement by medical insurance and their perceived difficulty or exotic "alternative" nature. Future use can be promoted by new technology (single-sample phase measurements, phone apps, movement and sleep trackers) that provides ambulatory documentation over long periods and feedback to therapist and patient. Light combinations with cognitive behavioural therapy and sleep hygiene practice may speed up and also maintain response. The urgent need for new antidepressants should hopefully lead to reconsideration and implementation of these non-pharmacological methods, as well as further clinical trials. We review the putative neurochemical mechanisms underlying the antidepressant effect of sleep deprivation and light therapy, and current knowledge linking clocks and sleep with affective disorders: neurotransmitter switching, stress and cortico-limbic reactivity, clock genes, cortical neuroplasticity, connectomics and neuroinflammation. Despite the complexity of multi-system mechanisms, more insight will lead to fine tuning and better application of circadian and sleep-related treatments of depression.

Multilevel Interactions of Stress and Circadian System: Implications for Traumatic Stress

The dramatic fluctuations in energy demands by the rhythmic succession of night and day on our planet has prompted a geophysical evolutionary need for biological temporal organization across phylogeny. The intrinsic circadian timing system (CS) represents a highly conserved and sophisticated internal "clock," adjusted to the 24-h rotation period of the earth, enabling a nyctohemeral coordination of numerous physiologic processes, from gene expression to behavior. The human CS is tightly and bidirectionally interconnected to the stress system (SS). Both systems are fundamental for survival and regulate each other's activity in order to prepare the organism for the anticipated cyclic challenges. Thereby, the understanding of the temporal relationship between stressors and stress responses is critical for the comprehension of the molecular basis of physiology and pathogenesis of disease. A critical loss of the harmonious timed order at different organizational levels may affect the fundamental properties of neuroendocrine, immune, and autonomic systems, leading to a breakdown of biobehavioral adaptative mechanisms with increased stress sensitivity and vulnerability. In this review, following an overview of the functional components of the SS and CS, we present their multilevel interactions and discuss how traumatic stress can alter the interplay between the two systems. Circadian dysregulation after traumatic stress exposure may represent a core feature of trauma-related disorders mediating enduring neurobiological correlates of trauma through maladaptive stress regulation. Understanding the mechanisms susceptible to circadian dysregulation and their role in stress-related disorders could provide new insights into disease mechanisms, advancing psychochronobiological treatment possibilities and preventive strategies in stress-exposed populations.

Therapeutic spectrum of interferon-β in ischemic stroke

Ischemic stroke is devastating and a major cause of morbidity and mortality worldwide. To date, only clot retrieval devices and/or intravenous tissue plasminogen activators (tPA) have been approved by the US-FDA for the treatment of acute ischemic stroke. Therefore, there is an urgent need to develop an effective treatment for stroke that can have limited shortcomings and broad spectrum of applications. Interferon-beta (IFN-β), an endogenous cytokine and a key anti-inflammatory agent, contributes toward obviating deleterious stroke outcomes. Therefore, exploring the role of IFN-β may be a promising alternative approach for stroke intervention in the future. In the present review, we have discussed about IFN-β along with its different mechanistic roles in ischemic stroke. Furthermore, therapeutic approaches targeting the inflammatory cascade with IFN-β therapy that may be helpful in improving stroke outcome are also discussed.

Pathophysiology of Depression: Molecular Regulation of Melatonin Homeostasis - Current Status

Circadian rhythm alterations resulting in disturbed sleep and disturbed melatonin secretion are flagship features of depression. Melatonin, known as a hormone of darkness, is secreted by the pineal gland located near to the center of the brain between the two hemispheres. Melatonin has an antidepressant effect by maintaining the body's circadian rhythm, by regulating the pattern of expression of the clock genes in the suprachiasmatic nucleus (SCN) and modifying the key genes of serotoninergic neurotransmission that are linked with a depressive mood. Melatonin is produced via the metabolism of serotonin in two steps which are catalyzed by serotonin N-acetyltransferase (SNAT) and acetylserotonin-O-methyltransferase (ASMT). Serotonin, SNAT, and ASMT are key melatonin level regulation factors. Melatonin acts mainly on the MT1 and MT2 receptors, which are present in the SCN, to regulate physiological and neuroendocrine functions including circadian entrainment, referred to as a chronobiotic effect. Although melatonin has been known about and refereed to for almost 50 years, the relationship between melatonin and depression is still not clear. In this review, we summarize current knowledge about the genetic and epigenetic regulation of enzymes involved in melatonin synthesis and metabolism as potential features of depression pathophysiology and treatment. Confirmation that melatonin metabolism in peripheral blood partially reflects a disorder in the brain could be a breakthrough in the standardization of measurements of melatonin level for the development of treatment standards, finding new therapeutic targets, and elaborating simple noninvasive clinical tests.

Mitochondrial Agents for Bipolar Disorder

Background

Bipolar disorder is a chronic and often debilitating illness. Current treatment options (both pharmaco- and psychotherapy) have shown efficacy, but for many leave a shortfall in recovery. Advances in the understanding of the pathophysiology of bipolar disorder suggest that interventions that target mitochondrial dysfunction may provide a therapeutic benefit.

Methods

This review explores the current and growing theoretical rationale as well as existing preclinical and clinical data for those therapies aiming to target the mitochondrion in bipolar disorder. A Clinicaltrials.gov and ANZCTR search was conducted for complete and ongoing trials on mitochondrial agents used in psychiatric disorders. A PubMed search was also conducted for literature published between January 1981 and July 2017. Systematic reviews, randomized controlled trials, observational studies, case series, and animal studies with an emphasis on agents affecting mitochondrial function and its role in bipolar disorder were included. The search was augmented by manually searching the references of key papers and related literature. The results were presented as a narrative review.

Results

Mitochondrial agents offer new horizons in mood disorder treatment. While some negative effects have been reported, most compounds are overall well tolerated and have generally benign side-effect profiles.

Conclusions

The study of neuroinflammation, neurodegeneration, and mitochondrial function has contributed the understanding of bipolar disorder's pathophysiology. Agents targeting these pathways could be a potential therapeutic strategy. Future directions include identification of novel candidate mitochondrial modulators as well as rigorous and well-powered clinical trials.

Cytokine alterations and cognitive impairment in major depressive disorder: From putative mechanisms to novel treatment targets

Overwhelming evidence indicates the involvement of immune-inflammatory processes in the pathophysiology of major depressive disorder (MDD). Peripheral cytokine alterations serve as one of most consistently reported indices of subthreshold inflammatory state observed in MDD. Although cytokines cannot pass directly through the blood-brain barrier, a number of transport mechanisms have been reported. In addition, peripheral cytokines may impact central nervous system via downstream effectors of their biological activity. Animal model studies have provided evidence that cytokines might impact cognitive performance through direct and indirect effects on long-term potentiation, neurogenesis and synaptic plasticity. Therefore, it has been hypothesized that cytokine alterations might contribute to cognitive impairment that is widely observed in MDD and persists beyond episodes of acute relapse in the majority of patients. Although several studies have provided that peripheral cytokine alterations might be related to cognitive deficits in patients with MDD, the quality of evidence still leaves much to be desired due to methodological heterogeneity and limitations. In this article, we provide an overview of studies investigating the association between peripheral cytokine alterations and cognitive performance in MDD, discuss underlying mechanisms and neural substrates. Finally, we propose possible treatment targets related to cytokine alterations taking into account existing evidence for antidepressant efficacy of anti-inflammatory pharmacological treatment modalities.

Circadian Rhythm Disturbances in Mood Disorders: Insights into the Role of the Suprachiasmatic Nucleus

Circadian rhythm disturbances are a common symptom among individuals with mood disorders. The suprachiasmatic nucleus (SCN), in the ventral part of the anterior hypothalamus, orchestrates physiological and behavioral circadian rhythms. The SCN consists of self-sustaining oscillators and receives photic and nonphotic cues, which entrain the SCN to the external environment. In turn, through synaptic and hormonal mechanisms, the SCN can drive and synchronize circadian rhythms in extra-SCN brain regions and peripheral tissues. Thus, genetic or environmental perturbations of SCN rhythms could disrupt brain regions more closely related to mood regulation and cause mood disturbances. Here, we review clinical and preclinical studies that provide evidence both for and against a causal role for the SCN in mood disorders.

Melatonin Augments the Effects of Fluoxetine on Depression-Like Behavior and Hippocampal BDNF-TrkB Signaling

Depression is a debilitating psychiatric disorder with a huge socioeconomic burden, and its treatment relies on antidepressants including selective serotonin reuptake inhibitors (SSRIs). Recently, the melatonergic system that is closely associated with the serotonergic system has been implicated in the pathophysiology and treatment of depression. However, it remains unknown whether combined treatment with SSRI and melatonin has synergistic antidepressant effects. In this study, we applied a sub-chronic restraint stress paradigm, and evaluated the potential antidepressant effects of combined fluoxetine and melatonin in adult male mice. Sub-chronic restraint stress (6 h/day for 10 days) induced depression-like behavior as shown by deteriorated fur state, increased latency to groom in the splash test, and increased immobility time in the forced-swim test. Repeated administration of either fluoxetine or melatonin at 10 mg/kg during stress exposure failed to prevent depression-like phenotypes. However, combined treatment with fluoxetine and melatonin at the selected dose attenuated stress-induced behavioral abnormalities. Moreover, we found that the antidepressant effects of combined treatment were associated with the normalization of brain-derived neurotrophic factor (BDNF)-tropomyosin receptor kinase B (TrkB) signaling in the hippocampus, but not in the prefrontal cortex. Our findings suggest that combined fluoxetine and melatonin treatment exerts synergistic antidepressant effects possibly by restoring hippocampal BDNF-TrkB signaling.

Depressive-like behavior is elevated among offspring of parents exposed to dim light at night prior to mating

Rates of major depressive disorder (MDD) have steadily increased over the past 50 years. Many factors have been implicated in the etiology of depressive disorders and environmental influences are being increasingly recognized. The increase in depression rates has coincided with increased artificial nighttime lighting. Exposure to light at night (LAN) has been associated with increased depressive-like behavior in rodents and decreased mood in humans. However, relatively little is known on the multigenerational effects of dLAN on affect. In this study, we exposed adult male and female Siberian hamsters (Phodopus sungorus) to either DARK (0lx) or dim LAN (5lx) for 9 weeks, then paired animals in a full factorial design; all animals were thereafter housed in dark nights. Offspring were gestated and reared in dark nights, then tested in adulthood for depressive-like behaviors and hippocampal expression of glucocorticoid (GR) and melatonin (MT1) receptor expression. Maternal exposure to dLAN decreased sucrose preference, time to first float bout in the Porsolt swim test, and GR expression in the hippocampus. Paternal exposure to dLAN increased time spent floating, and increased hippocampal GR expression. Overall, our results suggest that chronic exposure of parents to light at night has multigenerational effects on offspring depressive-like behavior. If these results pertain to humans, then our data suggest that LAN may contribute to the rapidly rising rates of major depressive disorder in industrialized and developing countries.

The effect of MElatonin on Depressive symptoms, Anxiety, CIrcadian and Sleep disturbances in patients after acute coronary syndrome (MEDACIS): study protocol for a randomized controlled trial

BACKGROUND

Depression following acute coronary syndrome (ACS) constitutes a serious and debilitating problem. Approximately one in five patients will develop significant depression following ACS and less severe depressive symptoms are even more frequent. Furthermore, anxiety symptoms and sleep-wake disturbances are frequent. The objective of the MEDACIS trial is to investigate whether prophylactic treatment with melatonin has a preventive effect on depression, depressive and anxiety symptoms, sleep, and circadian disturbances following ACS.

METHODS/DESIGN

"The effect of MElatonin and Depressive symptoms, Anxiety, CIrcadian and Sleep disturbances in patients after acute coronary syndrome" trial (MEDACIS) is a multicenter, double-blinded, placebo-controlled, randomized clinical trial. A total of 240 patients with ACS and no depressive symptoms will be included in the trial for treatment with either 25 mg melatonin or placebo for a 12-week period. Development and severity of depressive symptoms will be evaluated using Major Depression Inventory every 2 weeks with the purpose of investigating the potential preventive effect of melatonin on depressive symptoms.

DISCUSSION

Previously, only selective serotonin reuptake inhibitors (SSRIs) have been investigated in a primary preventive setup in patients following ACS. However, SSRIs are associated with several side effects. An ideal intervention would constitute the highest degree of prevention of depressive symptoms with the lowest risk of side effects. In this regard, melatonin may have advantages due to its low toxicity as well as its proven anxiolytic and hypnotic effects.

TRIAL REGISTRATION

ClinicalTrials.gov, Identifier: NCT02451293 . Registered on 12 May 2015. EudraCT nr. 2015-002116-32.

Quality and clarity in systematic review abstracts: an empirical study

BACKGROUND

Systematic review (SR) abstracts are important for disseminating evidence syntheses to inform medical decision making. We assess reporting quality in SR abstracts using PRISMA for Abstracts (PRISMA-A), Cochrane Handbook, and Agency for Healthcare Research & Quality guidance.

METHODS

We evaluated a random sample of 200 SR abstracts (from 2014) comparing interventions in the general medical literature. We assessed adherence to PRISMA-A criteria, problematic wording in conclusions, and whether "positive" studies described clinical significance.

RESULTS

On average, abstracts reported 60% of PRISMA-A checklist items (mean 8.9 ± 1.7, range 4 to 12). Eighty percent of meta-analyses reported quantitative measures with a confidence interval. Only 49% described effects in terms meaningful to patients and clinicians (e.g., absolute measures), and only 43% mentioned strengths/limitations of the evidence base. Average abstract word count was 274 (SD 89). Word count explained only 13% of score variability. PRISMA-A scores did not differ between Cochrane and non-Cochrane abstracts (mean difference 0.08, 95% confidence interval -1.16 to 1.00). Of 275 primary outcomes, 48% were statistically significant, 32% were not statistically significant, and 19% did not report significance or results. Only one abstract described clinical significance for positive findings. For "negative" outcomes, we identified problematic simple restatements (20%), vague "no evidence of effect" wording (9%), and wishful wording (8%).

CONCLUSIONS

Improved SR abstract reporting is needed, particularly reporting of quantitative measures (for meta-analysis), easily interpretable units, strengths/limitations of evidence, clinical significance, and clarifying whether negative results reflect true equivalence between treatments. Copyright © 2016 John Wiley & Sons, Ltd.

Mindfulness meditation for insomnia: A meta-analysis of randomized controlled trials

BACKGROUND

Insomnia is a widespread and debilitating condition that affects sleep quality and daily productivity. Although mindfulness meditation (MM) has been suggested as a potentially effective supplement to medical treatment for insomnia, no comprehensively quantitative research has been conducted in this field. Therefore, we performed a meta-analysis on the findings of related randomized controlled trials (RCTs) to evaluate the effects of MM on insomnia.

METHODS

Related publications in PubMed, EMBASE, the Cochrane Library and PsycINFO were searched up to July 2015. To calculate the standardized mean differences (SMDs) and 95% confidence intervals (CIs), we used a fixed effect model when heterogeneity was negligible and a random effect model when heterogeneity was significant.

RESULTS

A total of 330 participants in 6 RCTs that met the selection criteria were included in this meta-analysis. Analysis of overall effect revealed that MM significantly improved total wake time and sleep quality, but had no significant effects on sleep onset latency, total sleep time, wake after sleep onset, sleep efficiency, total wake time, ISI, PSQI and DBAS. Subgroup analyses showed that although there were no significant differences between MM and control groups in terms of total sleep time, significant effects were found in total wake time, sleep onset latency, sleep quality, sleep efficiency, and PSQI global score (absolute value of SMD range: 0.44-1.09, all p<0.05).

CONCLUSIONS

The results suggest that MM may mildly improve some sleep parameters in patients with insomnia. MM can serve as an auxiliary treatment to medication for sleep complaints.

Potential pleiotropic beneficial effects of adjuvant melatonergic treatment in posttraumatic stress disorder

Loss of circadian rhythmicity fundamentally affects the neuroendocrine, immune, and autonomic system, similar to chronic stress and may play a central role in the development of stress-related disorders. Recent articles have focused on the role of sleep and circadian disruption in the pathophysiology of posttraumatic stress disorder (PTSD), suggesting that chronodisruption plays a causal role in PTSD development. Direct and indirect human and animal PTSD research suggests circadian system-linked neuroendocrine, immune, metabolic and autonomic dysregulation, linking circadian misalignment to PTSD pathophysiology. Recent experimental findings also support a specific role of the fundamental synchronizing pineal hormone melatonin in mechanisms of sleep, cognition and memory, metabolism, pain, neuroimmunomodulation, stress endocrinology and physiology, circadian gene expression, oxidative stress and epigenetics, all processes affected in PTSD. In the current paper, we review available literature underpinning a potentially beneficiary role of an add-on melatonergic treatment in PTSD pathophysiology and PTSD-related symptoms. The literature is presented as a narrative review, providing an overview on the most important and clinically relevant publications. We conclude that adjuvant melatonergic treatment could provide a potentially promising treatment strategy in the management of PTSD and especially PTSD-related syndromes and comorbidities. Rigorous preclinical and clinical studies are needed to validate this hypothesis.

Melatonin and neurotrophins NT-3, BDNF, NGF in patients with varying levels of depression severity

BACKGROUND

Disrupted circadian rhythm of melatonin secretion in depression shows a relationship with the exacerbation of inflammatory processes. Proinflammatory mechanisms of depression are sustained by oxidative stress. This contributes to melatonin deficiency and to the malfunction of the defense mechanisms in the brain. Disrupted melatonin secretion in depression may have an influence on the concentrations of neurotrophic factors (NF), such as neurotrophin-3 (NT-3), brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF). Disturbance in neurotrophin release may affect synaptic plasticity and cause exacerbation of neurodegenerative processes in the central nervous system. The aim of this study was to assess the concentrations of melatonin and NF of the brain in patients with varying levels of depression severity.

METHOD

160 males and females were enrolled in the study, 120 of whom were diagnosed with various types of depression. The control group comprised 40 healthy individuals. At 3:00a.m. all patients had salivary melatonin concentrations determined utilizing a competitive enzyme immunoassay technique (ELISA). In addition, at 7:00a.m. all patients had serum neurotrophin (NT-3, BDNF, NGF) concentrations determined by means of ELISA.

RESULTS

The highest melatonin secretion was observed at 3:00a.m. in severely depressed females. In the groups with mild and moderate depression, melatonin secretion at 3:00a.m. was comparable between males and females. In addition, a decrease in the concentrations of neurotrophins was revealed in patients at all levels of depression severity.

CONCLUSION

Melatonin may be a significant marker of depression severity. Melatonin and NF in depressed patients show neuroprotective effects.

Time-dependent miR-16 serum fluctuations together with reciprocal changes in the expression level of miR-16 in mesocortical circuit contribute to stress resilient phenotype in chronic mild stress - An animal model of depression

MicroRNAs (miRNAs) are involved in stress-related pathologies. However, the molecular mechanisms underlying stress resilience are elusive. Using chronic mild stress (CMS), an animal model of depression, we identified animals exhibiting a resilient phenotype. We investigated serum levels of corticosterone, melatonin and 376 mature miRNAs to find peripheral biomarkers associated with the resilient phenotype. miR-16, selected during screening step, was assayed in different brain regions in order to find potential relationship between brain and peripheral alterations in response to stress. Two CMS experiments that lasted for 2 and 7 consecutive weeks were performed. During both CMS procedures, sucrose consumption levels were significantly decreased in anhedonic-like animals (p<0.0001) compared with unstressed animals, whereas the drinking profiles of resilient rats did not change despite the rats being stressed. Serum corticosterone measurements indicated that anhedonic-like animals had blunted hypothalamic-pituitary-adrenal (HPA) axis activity, whereas resilient animals exhibited dynamic responses to stress. miRNA profiling revealed that resilient animals had elevated serum levels of miR-16 after 7 weeks of CMS (adjusted p-value<0.007). Moreover, resilient animals exhibited reciprocal changes in miR-16 expression level in mesocortical pathway after 2 weeks of CMS (p<0.008). A bioinformatic analysis showed that miR-16 regulates genes involved in the functioning of the nervous system in both humans and rodents. Resilient animals can actively cope with stress on a biochemical level and miR-16 may contribute to a "stress-resistant" behavioral phenotype by pleiotropic modulation of the expression of genes involved in the function of the nervous system.

MT1 and MT2 Melatonin Receptors: A Therapeutic Perspective

Melatonin, or 5-methoxy-N-acetyltryptamine, is synthesized and released by the pineal gland and locally in the retina following a circadian rhythm, with low levels during the day and elevated levels at night. Melatonin activates two high-affinity G protein-coupled receptors, termed MT1 and MT2, to exert beneficial actions in sleep and circadian abnormality, mood disorders, learning and memory, neuroprotection, drug abuse, and cancer. Progress in understanding the role of melatonin receptors in the modulation of sleep and circadian rhythms has led to the discovery of a novel class of melatonin agonists for treating insomnia, circadian rhythms, mood disorders, and cancer. This review describes the pharmacological properties of a slow-release melatonin preparation (i.e., Circadin®) and synthetic ligands (i.e., agomelatine, ramelteon, tasimelteon), with emphasis on identifying specific therapeutic effects mediated through MT1 and MT2 receptor activation. Discovery of selective ligands targeting the MT1 or the MT2 melatonin receptors may promote the development of novel and more efficacious therapeutic agents.

Physiological Levels of Melatonin Relate to Cognitive Function and Depressive Symptoms: The HEIJO-KYO Cohort

CONTEXT

In contrast with randomized controlled trials, observational studies have suggested that physiological levels of melatonin are reduced in patients with dementia or depression, but the relationship has not been evaluated in large populations.

OBJECTIVE

The objective was to determine the relationships between physiological levels of melatonin and cognitive function and depressive symptoms.

DESIGN AND PARTICIPANTS

A cohort of 1105 community-dwelling elderly individuals was enrolled in this cross-sectional study (mean age, 71.8 ± 7.1 y).

MEASURES

Urinary 6-sulfatoxymelatonin excretion (UME) and Mini-Mental State Examination (MMSE; n = 935) and Geriatric Depression Scale (GDS; n = 1097) scores were measured as indices of physiological melatonin levels, cognitive function, and depressive symptoms, respectively.

RESULTS

With increases in UME quartiles, the prevalence of cognitive impairment (MMSE score ≤ 26) and depressed mood (GDS score ≥ 6) significantly decreased (P for trend = .003 and .012, respectively). In multivariate logistic regression models, after adjusting for confounders such as age, gender, socioeconomic status, physical activity, and sleep/wake cycles, higher UME levels were significantly associated with lower odds ratios (ORs) for cognitive impairment and depressed mood (ORs: Q1 = 1.00; Q2 = 0.88 and 0.76; Q3 = 0.66 and 0.85; Q4 = 0.67 and 0.53; P for trend = .023 and .033, respectively). In addition, the highest UME group showed a significantly lower OR for depressed mood than the lowest UME group (Q4 vs Q1: OR, 0.53; 95% confidence interval, 0.32-0.89; P = .033). UME levels above the median value were significantly associated with a lower OR for cognitive impairment, even after further adjustment for depressive symptoms (OR = 0.74; 95% confidence interval, 0.55-0.99; P = .043).

CONCLUSIONS

Significant associations of higher physiological melatonin levels with lower prevalence of cognitive impairment and depressed mood were revealed in a large general elderly population. The association between physiological melatonin levels and cognitive function was independent of depressive symptoms.