Actigraphic sleep-wake patterns and urinary 6-sulfatoxymelatonin excretion in patients with Alzheimer's disease

Protective Effect of the Novel Melatonin Analogue Containing Donepezil Fragment on Memory Impairment via MT/ERK/CREB Signaling in the Hippocampus in a Rat Model of Pinealectomy and Subsequent Aβ1-42 Infusion

A reduction in melatonin function contributes to the acceleration of Alzheimer's disease (AD), and understanding the molecular processes of melatonin-related signaling is critical for intervention in AD progression. Recently, we synthesized a series of melatonin analogues with donepezil fragments and tested them in silico and in vitro. In this study, one of the most potent compounds, 3c, was evaluated in a rat model of pinealectomy (pin) followed by icvAβ1-42 infusion. Melatonin was used as the reference drug. Treatment with melatonin and 3c (10 mg/kg, i.p. for 14 days) had a beneficial effect on memory decline and the concomitant increase in hippocampal Aβ1-42 and pTAU in the pin+icvAβ1-42 rats. Melatonin supplementation facilitated non-amyloidogenic signaling via non-receptor (histone deacetylase sirtuin 1, SIRT1) and receptor-related signaling (MT/ERK/CREB). The hybrid 3c analogue up-regulated the MT1A and MT2B receptors, pERK and pCREB. Our results strongly support the hypothesis that melatonin-related analogues may become a promising drug candidate for Alzheimer's disease therapy.

Circadian disruption and human health

Circadian disruption is pervasive and can occur at multiple organizational levels, contributing to poor health outcomes at individual and population levels. Evidence points to a bidirectional relationship, in that circadian disruption increases disease severity and many diseases can disrupt circadian rhythms. Importantly, circadian disruption can increase the risk for the expression and development of neurologic, psychiatric, cardiometabolic, and immune disorders. Thus, harnessing the rich findings from preclinical and translational research in circadian biology to enhance health via circadian-based approaches represents a unique opportunity for personalized/precision medicine and overall societal well-being. In this Review, we discuss the implications of circadian disruption for human health using a bench-to-bedside approach. Evidence from preclinical and translational science is applied to a clinical and population-based approach. Given the broad implications of circadian regulation for human health, this Review focuses its discussion on selected examples in neurologic, psychiatric, metabolic, cardiovascular, allergic, and immunologic disorders that highlight the interrelatedness between circadian disruption and human disease and the potential of circadian-based interventions, such as bright light therapy and exogenous melatonin, as well as chronotherapy to improve and/or modify disease outcomes.

Melatonin levels in the Alzheimer's disease continuum: a systematic review

Background

The search for new Alzheimer’s disease (AD) cerebrospinal fluid (CSF) and blood biomarkers with potential pathophysiological and clinical relevance continues, as new biomarkers might lead to improved early and differential diagnosis, monitoring of disease progression and might even identify new druggable targets. Melatonin might be an interesting biomarker as an inverse correlation between CSF melatonin levels, and severity of the neuropathology as measured by Braak stages has been described. Melatonin can be measured in different body fluids, such as CSF, blood, saliva and urine.

Objectives

The aim of this systematic review was to review all available studies regarding melatonin levels in different body fluids in the AD continuum and give an extensive overview of reported outcomes.

Methods

We included papers comparing melatonin levels between healthy controls and human patients belonging to the AD continuum. A systematic search of PubMed and Web of Science led to inclusion of 20 full-length English papers following exclusion of duplicates.

Results

This systematic literature search showed that disruptions in melatonin levels occur with age, but also in AD when compared to age-matched controls. Night-time melatonin levels were found to be lower in CSF and blood of AD patients as compared to controls. Literature was not conclusive regarding alterations in blood daytime melatonin levels or regarding saliva melatonin in AD patients. Decreased total and night-time melatonin production has been described in urine of AD patients.

Conclusion

Our systematic review shows evidence for disruptions in (night-time) melatonin levels in AD as compared to age-matched controls. Although more studies are needed to understand the contribution of disruption of the melatonergic system to the pathophysiology of AD, the potential anti-AD effects that have been attributed to melatonin, renders research on this topic relevant for the discovery of potential future treatment effects of melatonin for AD. The use of melatonin as potential blood biomarker for disease progression should also be further investigated.

Sleep Disturbances After General Anesthesia: Current Perspectives

The purpose of this article is to review (1) sleep mechanism under general anesthesia, harmful effects of postoperative sleep disturbances; (2) risk factors associated with postoperative sleep disturbances; (3) measures to prevent and improve postoperative sleep disturbances. General anesthesia changes the postoperative sleep structure especially in elderly patients after major surgery and results in a high incidence rate of sleep disturbances. Sleep disturbances produce harmful effects on postoperative patients and lead to a higher risk of delirium, more cardiovascular events, and poorer recovery. Some researchers do propose non-pharmacological treatments such as attention to environmental and psychological factors, application of electroacupuncture (EA) technology and pharmacological treatments are helpful, but larger high-quality clinical trials with longer following-up are needed to further investigate the efficacy and safety.

Pineal gland dysfunction in Alzheimer's disease: relationship with the immune-pineal axis, sleep disturbance, and neurogenesis

Alzheimer’s disease (AD) is a globally common neurodegenerative disease, which is accompanied by alterations to various lifestyle patterns, such as sleep disturbance. The pineal gland is the primary endocrine organ that secretes hormones, such as melatonin, and controls the circadian rhythms. The decrease in pineal gland volume and pineal calcification leads to the reduction of melatonin production. Melatonin has been reported to have multiple roles in the central nervous system (CNS), including improving neurogenesis and synaptic plasticity, suppressing neuroinflammation, enhancing memory function, and protecting against oxidative stress. Recently, reduced pineal gland volume and pineal calcification, accompanied by cognitive decline and sleep disturbances have been observed in AD patients. Here, I review current significant evidence of the contribution of pineal dysfunction in AD to the progress of AD neuropathology. I suggest new insights to understanding the relationship between AD pathogenesis and pineal gland function.

[Disturbances in melatonin secretion and the efficacy of replacement therapy in sleep disorders]

The review presents data on the dependence of endogenous melatonin synthesis on the time of day, age, pineal gland size, lighting conditions, administration of beta-blockers and a number of other medications. The results of studies on parasecretion and efficacy of exogenous melatonin use in sleep-wake cycle disturbances, insomnia, neurodegeneration, diabetes mellitus and oncological diseases are discussed.

Self-awakening improves alertness in the morning and during the day after partial sleep deprivation

The ability to awaken at a predetermined time without an alarm is known as self-awakening. Self-awakening improves morning alertness by eliminating sleep inertia; however, the effects of self-awakening on daytime alertness and alertness that has deteriorated as a result of sleep loss are unknown. The aim of this study was to determine the effects of self-awakening on both morning and daytime alertness after partial sleep deprivation. Fifteen healthy males without the habit of self-awakening participated in a cross-over trial including forced awakening and self-awakening conditions. In each condition, participants' sleep was restricted to 5 h per night in their homes for 4 consecutive days. They completed a psychomotor vigilance task and subjective ratings of sleepiness immediately upon awakening each morning. On the fourth day, participants completed subjective ratings of sleepiness, a psychomotor vigilance task and sleep latency tests in the laboratory seven times at 1-h intervals during the day. The response speed on the psychomotor vigilance task, in the morning and during the day, was higher in the self-awakening than the forced awakening condition. Our results showed that self-awakening improved alertness (assessed by response speeds) by reducing sleep inertia and alleviated daytime sleepiness heightened by partial sleep deprivation.

Melatonin: buffering the immune system

Melatonin modulates a wide range of physiological functions with pleiotropic effects on the immune system. Despite the large number of reports implicating melatonin as an immunomodulatory compound, it still remains unclear how melatonin regulates immunity. While some authors argue that melatonin is an immunostimulant, many studies have also described anti-inflammatory properties. The data reviewed in this paper support the idea of melatonin as an immune buffer, acting as a stimulant under basal or immunosuppressive conditions or as an anti-inflammatory compound in the presence of exacerbated immune responses, such as acute inflammation. The clinical relevance of the multiple functions of melatonin under different immune conditions, such as infection, autoimmunity, vaccination and immunosenescence, is also reviewed.

Circadian clock gene expression in brain regions of Alzheimer 's disease patients and control subjects

Circadian oscillators have been observed throughout the rodent brain. In the human brain, rhythmic expression of clock genes has been reported only in the pineal gland, and little is known about their expression in other regions. The investigators sought to determine whether clock gene expression could be detected and whether it varies as a function of time of day in the bed nucleus of the stria terminalis (BNST) and cingulate cortex, areas known to be involved in decision making and motivated behaviors, as well as in the pineal gland, in the brains of Alzheimer's disease (AD) patients and aged controls. Relative expression levels of PERIOD1 (PER1 ), PERIOD2 (PER2), and Brain and muscle Arnt-like protein-1 (BMAL1) were detected by quantitative PCR in all 3 brain regions. A harmonic regression model revealed significant 24-h rhythms of PER1 in the BNST of AD subjects. A significant rhythm of PER2 was found in the cingulate cortex and BNST of control subjects and in all 3 regions of AD patients. In controls, BMAL1 did not show a diurnal rhythm in the cingulate cortex but significantly varied with time of death in the pineal and BNST and in all 3 regions for AD patients. Notable differences in the phase of clock gene rhythms and phase relationships between genes and regions were observed in the brains of AD compared to those of controls. These results indicate the presence of multiple circadian oscillators in the human brain and suggest altered synchronization among these oscillators in the brain of AD patients.

Sleep-wake changes and cognition in neurodegenerative disease

With the increasing aging population, neurodegenerative disorders will become more common in clinical practice. These disorders involve multiple pathophysiological mechanisms that differentially affect cognition, mood, and physical functions. Possibly due to the involvement of common underlying neurobiological circuits, sleep and/or circadian (sleep-wake) changes are also common in this disease group. Of significance, sleep-wake changes are often a prodromal feature and are predictive of cognitive decline, psychiatric symptoms, quality of life, need for institutional care, and caregiver burden. Unfortunately, in neurodegenerative disease, few studies have included detailed polysomnography or neuropsychological assessments although some data indicate that sleep and neurocognitive features are related. Further studies are also required to address the effects of pharmacological and nonpharmacological treatments on cognitive functioning. Such research will hopefully lead to targeted early intervention approaches for cognitive decline in older people.

Photoimmunomodulation and melatonin

The seasons, and daily physical rhythms can have a profound effect on the physiology of the living organism, which includes immune status. The immune system can be influenced by a variety of signals and one of them is photic stimulus. Light may regulate the immunity through the neuroendocrine system leading to the most recent branch of research the "Photoimmunomodulation". Mammals perceive visible light (400-700 nm) through some specialized photoreceptors located in retina like retinal ganglion cells (RGC). This photic signal is then delivered to the visual cortex from there to the suprachiasmatic nucleus (SCN) of the hypothalamic region. Melatonin--one of the universally accepted chronobiotic molecule secreted by the pineal gland is now emerging as one of the most effective immunostimulatory compound in rodents and as oncostatic molecule at least in human. Its synthesis decreases with light activation along with norepinephrine and acetylcholine. The changes in level of melatonin may lead to alterations (stimulatory/inhibitory) in immune system. The evidences for the presence of melatonin receptor subtypes on lymphoid tissues heralded the research area about mechanism of action for melatonin. Further, melatonin receptor subtypes-MT1 and MT2 was noted on pars tuberalis, SCN and on lymphatic tissues suggesting a direct action of melatonin in modulation of immunity by photoperiod as well. The nuclear receptors (ROR, RZR etc.) of melatonin are known for its free radical scavenging actions and might be indirectly controlling the immune function.

The role of circadian clock genes in mental disorders

The study of molecular clock mechanisms in psychiatric disorders is gaining significant interest due to data suggesting that a misalignment between the endogenous circadian system and the sleep-wake cycle might contribute to the clinical status of patients suffering from a variety of psychiatric disorders. Sleep disturbances in major depressive disorder (MDD) are characterized by increased sleep latency, poorer sleep efficiency, reduced latency to the first rapid eye movement (REM) sleep episode, and early-morning awakening, but there is little data to indicate a role of circadian clock genes in MDD. There is also relatively little information regarding the role of clock genes in anxiety. In contrast, a significant amount of evidence gathered in bipolar disorder (BPD) patients suggests a circadian rhythm disorder, namely an advanced circadian rhythm and state-dependent alterations of REM sleep latency. Most research on the role of clock genes in BPD has focused on polymorphisms of CLOCK, but the lithium target GSK3 may also play a significant role. A circadian phase shift is also theorized to contribute to the pathophysiology of winter seasonal affective disorder (SAD). Certain allelic combinations of NPAS2, PER3, and BMAL1 appear to contribute to the risk of SAD. In chronic shizophrenia, disturbances of sleep including insomnia and reduced sleep efficiency have been observed. Genetic studies have found associations with CLOCK, PER1, PER3, and TIMELESS. Sleep and circadian changes associated with dementia due to Alzheimer's disease suggest a functional change in the circadian master clock, which is supported by postmortem studies of clock gene expression in the brain.

Pineal calcification in Alzheimer's disease: an in vivo study using computed tomography

Melatonin has been postulated to have diverse properties, acting as an antioxidant, a neuroprotector, or a stabilizer within the circadian timing system, and is thus thought to be involved in the aging process and Alzheimer's disease (AD). We used computed tomography to determine the degree of pineal calcification (DOC), an intra-individual melatonin deficit marker, as well as the size of uncalcified pineal tissue, in 279 consecutive memory clinic outpatients (AD: 155; other dementia: 25; mild cognitive impairment: 33; depression: 66) and 37 age-matched controls. The size of uncalcified pineal tissue in patients with AD (mean 0.15 cm(2) [S.D. 0.24]) was significantly smaller than in patients with other types of dementia (0.26 [0.34]; P=0.038), with depression (0.28 [0.34]; P=0.005), or in controls (0.25 [0.31]; P=0.027). Additionally, the DOC in patients with AD (mean 76.2% [S.D. 26.6]) was significantly higher than in patients with other types of dementia (63.7 [34.7]; P=0.042), with depression (60.5 [33.8]; P=0.001), or in controls (64.5 [30.6]; P=0.021). These two findings may reflect two different aspects of melatonin in AD. On the one hand, the absolute amount of melatonin excretion capability, as indicated by uncalcified pineal volume, refers to the antioxidant properties of melatonin. On the other hand, the relative reduction in melatonin production capability in the individual, as indicated by DOC, refers to the circadian properties of melatonin.

Melatonin

Melatonin is a ubiquitous molecule and widely distributed in nature, with functional activity occurring in unicellular organisms, plants, fungi and animals. In most vertebrates, including humans, melatonin is synthesized primarily in the pineal gland and is regulated by the environmental light/dark cycle via the suprachiasmatic nucleus. Pinealocytes function as 'neuroendocrine transducers' to secrete melatonin during the dark phase of the light/dark cycle and, consequently, melatonin is often called the 'hormone of darkness'. Melatonin is principally secreted at night and is centrally involved in sleep regulation, as well as in a number of other cyclical bodily activities. Melatonin is exclusively involved in signaling the 'time of day' and 'time of year' (hence considered to help both clock and calendar functions) to all tissues and is thus considered to be the body's chronological pacemaker or 'Zeitgeber'. Synthesis of melatonin also occurs in other areas of the body, including the retina, the gastrointestinal tract, skin, bone marrow and in lymphocytes, from which it may influence other physiological functions through paracrine signaling. Melatonin has also been extracted from the seeds and leaves of a number of plants and its concentration in some of this material is several orders of magnitude higher than its night-time plasma value in humans. Melatonin participates in diverse physiological functions. In addition to its timekeeping functions, melatonin is an effective antioxidant which scavenges free radicals and up-regulates several antioxidant enzymes. It also has a strong antiapoptotic signaling function, an effect which it exerts even during ischemia. Melatonin's cytoprotective properties have practical implications in the treatment of neurodegenerative diseases. Melatonin also has immune-enhancing and oncostatic properties. Its 'chronobiotic' properties have been shown to have value in treating various circadian rhythm sleep disorders, such as jet lag or shift-work sleep disorder. Melatonin acting as an 'internal sleep facilitator' promotes sleep, and melatonin's sleep-facilitating properties have been found to be useful for treating insomnia symptoms in elderly and depressive patients. A recently introduced melatonin analog, agomelatine, is also efficient for the treatment of major depressive disorder and bipolar affective disorder. Melatonin's role as a 'photoperiodic molecule' in seasonal reproduction has been established in photoperiodic species, although its regulatory influence in humans remains under investigation. Taken together, this evidence implicates melatonin in a broad range of effects with a significant regulatory influence over many of the body's physiological functions.

Melatonin in Alzheimer's disease and other neurodegenerative disorders

Increased oxidative stress and mitochondrial dysfunction have been identified as common pathophysiological phenomena associated with neurodegenerative disorders such as Alzheimer's disease (AD), Parkinson's disease (PD) and Huntington's disease (HD). As the age-related decline in the production of melatonin may contribute to increased levels of oxidative stress in the elderly, the role of this neuroprotective agent is attracting increasing attention. Melatonin has multiple actions as a regulator of antioxidant and prooxidant enzymes, radical scavenger and antagonist of mitochondrial radical formation. The ability of melatonin and its kynuramine metabolites to interact directly with the electron transport chain by increasing the electron flow and reducing electron leakage are unique features by which melatonin is able to increase the survival of neurons under enhanced oxidative stress. Moreover, antifibrillogenic actions have been demonstrated in vitro, also in the presence of profibrillogenic apoE4 or apoE3, and in vivo, in a transgenic mouse model. Amyloid-β toxicity is antagonized by melatonin and one of its kynuramine metabolites. Cytoskeletal disorganization and protein hyperphosphorylation, as induced in several cell-line models, have been attenuated by melatonin, effects comprising stress kinase downregulation and extending to neurotrophin expression. Various experimental models of AD, PD and HD indicate the usefulness of melatonin in antagonizing disease progression and/or mitigating some of the symptoms. Melatonin secretion has been found to be altered in AD and PD. Attempts to compensate for age- and disease-dependent melatonin deficiency have shown that administration of this compound can improve sleep efficiency in AD and PD and, to some extent, cognitive function in AD patients. Exogenous melatonin has also been reported to alleviate behavioral symptoms such as sundowning. Taken together, these findings suggest that melatonin, its analogues and kynuric metabolites may have potential value in prevention and treatment of AD and other neurodegenerative disorders.

The Use of Chronobiotics in the Resynchronization of the Sleep–wake Cycle

Treatment of circadian rhythm disorders, whether precipitated by intrinsic factors (e.g., sleep disorders, blindness, mental disorders, aging) or by extrinsic factors (e.g., shift work, jet-lag) has led to the development of a new type of agents called 'chronobiotics', among which melatonin is the prototype. The term 'chronobiotic' defines as a substance capable of shifting the phase of the circadian time system thus re-entraining circadian rhythms. Melatonin administration synchronizes the sleep-wake cycle in blind people and in individuals suffering from delayed sleep phase syndrome or jet lag, as well in shift-workers. The effect of melatonin on sleep is probably the consequence of increasing sleep propensity (by inducing a fall in body temperature) and of a synchronizing effect on the circadian clock (chronobiotic effect). We successfully employed the timely use of three factors (melatonin treatment, exposure to light, physical exercise) to hasten the resynchronization after transmeridian flights comprising 12-13 time zones, from an average of 8-10 days to about 2 days. Daily melatonin production decreases with age, and in several pathologies, attaining its lowest values in Alzheimer's dementia patients. About 45% of dementia patients have severe disruptions in their sleep-wakefulness cycle. Both in aged subjects having very minimal sleep disorders as well as in demented patients with a very severe disorganization of the sleep-wake cycle, melatonin treatment reduced the variability of sleep onset and restored sleep.

Melatonin, immune function and aging

Aging is associated with a decline in immune function (immunosenescence), a situation known to correlate with increased incidence of cancer, infectious and degenerative diseases. Innate, cellular and humoral immunity all exhibit increased deterioration with age. A decrease in functional competence of individual natural killer (NK) cells is found with advancing age. Macrophages and granulocytes show functional decline in aging as evidenced by their diminished phagocytic activity and impairment of superoxide generation. There is also marked shift in cytokine profile as age advances, e.g., CD3+ and CD4+ cells decline in number whereas CD8+ cells increase in elderly individuals. A decline in organ specific antibodies occurs causing reduced humoral responsiveness. Circulating melatonin decreases with age and in recent years much interest has been focused on its immunomodulatory effect. Melatonin stimulates the production of progenitor cells for granulocytes-macrophages. It also stimulates the production of NK cells and CD4+ cells and inhibits CD8+ cells. The production and release of various cytokines from NK cells and T-helper lymphocytes also are enhanced by melatonin. Melatonin presumably regulates immune function by acting on the immune-opioid network, by affecting G protein-cAMP signal pathway and by regulating intracellular glutathione levels. Melatonin has the potential therapeutic value to enhance immune function in aged individuals and in patients in an immunocompromised state.

Melatonin and sleep in aging population

The neurohormone melatonin is released from the pineal gland in close association with the light-dark cycle. There is a temporal relationship between the nocturnal rise in melatonin secretion and the 'opening of the sleep gate' at night. This association, as well as the sleep promoting effect of exogenous melatonin, implicates the pineal product in the physiological regulation of sleep. Aging is associated with a significant reduction in sleep continuity and quality. A decreased production of melatonin with age is documented in a majority of studies. Diminished nocturnal melatonin secretion with severe disturbances in sleep/wake rhythm has been consistently reported in Alzheimer's disease (AD). A recent survey on the effects of melatonin in sleep disturbances, including all age groups, failed to document significant and clinically meaningful effects of exogenous melatonin on sleep quality, efficiency and latency. However, in clinical trials involving elderly insomniacs and AD patients suffering from sleep disturbances exogenous melatonin has repeatedly been found to be effective in improving sleep. The results indicate that exogenous melatonin is more effective to promote sleep in the presence of a diminished production of endogenous melatonin. A MT1/MT2 receptor analog of melatonin (ramelteon) has recently been introduced as a new type of hypnotics with no evidence of abuse or dependence.

Role of melatonin in neurodegenerative diseases

The pineal product melatonin has remarkable antioxidant properties. It scavenges hydroxyl, carbonate and various organic radicals, peroxynitrite and other reactive nitrogen species. Melatonyl radicals formed by scavenging combine with and, thereby, detoxify superoxide anions in processes terminating the radical reaction chains. Melatonin also enhances the antioxidant potential of the cell by stimulating the synthesis of antioxidant enzymes like superoxide dismutase, glutathione peroxidase and glutathione reductase, and by augmenting glutathione levels. The decline in melatonin production in aged individuals has been suggested as one of the primary contributing factors for the development of age-associated neurodegenerative diseases, e.g., Alzheimer's disease. Melatonin has been shown to be effective in arresting neurodegenerative phenomena seen in experimental models of Alzheimer's disease, Parkinsonism and ischemic stroke. Melatonin preserves mitochondrial homeostasis, reduces free radical generation, e.g., by enhancing mitochondrial glutathione levels, and safeguards proton potential and ATP synthesis by stimulating complex I and IV activities. Therapeutic trials with melatonin have been effective in slowing the progression of Alzheimer's disease but not of Parkinson's disease. Melatonin's efficacy in combating free radical damage in the brain suggests that it may be a valuable therapeutic agent in the treatment of cerebral edema after traumatic brain injury.

Sleep disorders in Alzheimer's disease and other dementias

Patients with dementias, such as Alzheimer's disease (AD), often have nocturnally disrupted sleep. Clinically, this may present as agitation during the nighttime hours, which may affect as many as a quarter of AD patients during some stage of their illness. Sleep disturbance in AD may be multifactorial and involve sleep-disordered breathing and disrupted chronobiology, both often characterized by excessive daytime napping. Polysomnographically, AD patients show decreased rapid eye movement (REM) sleep in proportion to the extent of their dementia; some evidence suggests that cholinesterase inhibitors, commonly used pharmacologic agents for cognitive loss in AD, may increase REM sleep measures. Unfortunately, such agents may also induce insomnia and vivid dreams. There have been no randomized clinical trials of sedative-hypnotic medications specifically targeted at AD patients with sleep problems. Evidence suggests that sedative-hypnotics, such as benzodiazepine site-specific agonists, may have a role in some cases, whereas atypical antipsychotics may be necessary in other cases. There are also reports of successful interventions with nonpharmacologic options (eg, exercise, illumination). The utility of melatonin as a hypnotic in this population appears equivocal.

Nocturnal 6-sulfatoxymelatonin excretion in insomnia and its relation to the response to melatonin replacement therapy

PURPOSE

Melatonin, which is produced by the pineal gland at night, is an endogenous sleep regulator. Both sleep disorders and impaired melatonin production are common among the elderly. We examined the excretion of the major melatonin metabolite 6-sulfatoxymelatonin in insomnia patients aged >or=55 years and its relation with the subsequent response to melatonin therapy.

METHODS

We studied 517 insomnia patients, along with 29 age-matched and 30 younger healthy volunteers. Nocturnal urinary 6-sulfatoxymelatonin excretion was assessed between 10 pm and 10 am. Three hundred and ninety-six of the insomnia patients were treated for 2 weeks with placebo and for 3 weeks with 2 mg per night of controlled-release melatonin, of which 372 provided complete datasets. Clinical response, assessed with the Leeds Sleep Evaluation Questionnaire, was defined as an improvement of 10 mm or more on the visual analog scales.

RESULTS

Mean (+/- SD) 6-sulfatoxymelatonin excretion was lower in the insomnia patients (9.0 +/- 8.3 microg per night) than in volunteers of the same age (18.1 +/- 12.7 microg per night, P <0.05) and in younger volunteers (24.2 +/- 11.9 microg per night, P <0.05). About 30% of patients (112/372) excreted <or=3.5 microg of sulfatoxymelatonin per night, which is considered to be lower than normal for this age group. These "low excretors" had a significantly higher response to melatonin replacement therapy (58% [65/112] vs. 47% [122/260], P <0.05).

CONCLUSION

Low nocturnal melatonin production is associated with insomnia in patients aged 55 years or older, and identifies patients who are somewhat more likely to respond to melatonin replacement.

Effect of melatonin on changes in locomotor activity rhythm of Syrian hamsters injected with beta amyloid peptide 25-35 in the suprachiasmatic nuclei

1. Alzheimer's disease is associated with circadian rhythm disturbances, probably because of beta amyloid-induced neuronal damage of hypothalamic suprachiasmatic nuclei (SCN). 2. Since there is no published study on the circadian consequences of injecting beta amyloid peptide in experimental animals, one objective of the present study was to examine circadian locomotor activity in Syrian hamsters injected with beta amyloid peptide 25-35 into both SCN. 3. Because one of the proposed therapies for circadian alterations in dementia is the administration of melatonin, a chronobiotic agent with antioxidant properties, the preventive effect of melatonin on the circadian changes produced by beta amyloid microinjection into SCN was also assessed. 4. Wheel running activity was recorded by using the Dataquest III system in male golden hamsters kept under 14:10 light-dark photoperiods. Animals received microinjections of beta amyloid peptide 25-35 (100 microM solution, 1 microL) or saline in each SCN. Only those animals with neuronal lesions larger than 10% of SCN after beta amyloid injection were considered for further analysis. 5. To assess the effect of melatonin on beta-amyloid peptide activity, melatonin was given in the drinking water (25 microg/mL) starting 15 days in advance to the microinjection of beta amyloid peptide into SCN. 6. Beta amyloid-treated hamsters exhibited a significant phase advance of onset of running activity of about 22 min as compared to saline-injected animals. They also showed a significantly greater variability in onset time of wheel running activity, mainly evident from 6 to 15 days of treatment. 7. Melatonin administration in the drinking water prevented the phase advance of onset time and the increased variability of onset time brought about by beta amyloid peptide. 8. The results support the existence of a neuroprotective effect of melatonin on beta amyloid-induced circadian changes in hamsters.