Effect of light therapy on salivary melatonin in seasonal affective disorder

Circadian, hormonal, and sleep rhythms: effects on cancer progression implications for treatment

Circadian, hormonal, and sleep rhythm disruptions are commonly experienced concerns among cancer patients throughout the cancer care continuum. This review aims to summarize the existing literature on circadian, hormonal, and sleep rhythms in the oncological population, focusing on circadian disruption and physiological and psychological abnormalities, disease progression, and chronomodulated treatment approaches. The findings demonstrate that subjectively and objectively measured circadian rhythm disruption is associated with adverse mental health and disease outcomes in patients with cancer. Chronomodulated chemotherapy, light therapy, cognitive behavioral therapy for insomnia, and physical activity have shown evidence of effectiveness in improving sleep, and occasionally, disease outcomes.

Depressive mood and circadian rhythms disturbances as outcomes of seasonal affective disorder treatment: A systematic review

BACKGROUND

The present systematic review was aimed at critically summarizing the evidence about interventions focused on circadian rhythms and mood symptoms in seasonal affective disorder (SAD).

METHODS

A systematic search of the electronic databases PUBMED, PsycINFO and Web of Science was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement. Original papers reporting data about the effects of treatments on both mood and circadian rhythms disturbances in SAD patients were considered for inclusion. The quality of the evidence provided by the eligible studies was assessed using the Revised Cochrane Risk of Bias Tool (RoB 2.0) and the Cochrane Risk of Bias in Non-Randomized Studies of Interventions Tool (ROBINS-I).

RESULTS

Forty papers were deemed eligible for the systematic review. The evidence of treatment outcomes referring to circadian disturbances was not robust. Despite this, bright light therapy (BLT) demonstrates to phase-advance delayed rhythms and to improve sleep-wake disorders. As for mood symptoms, both BLT and selective serotonin reuptake inhibitors (SSRIs) show evidence of efficacy. The possible connection between improvements of mood symptoms and changes in circadian outcomes seems controversial.

LIMITATIONS

The included studies presented considerable methodological heterogeneity, small sample sizes and non-optimal sample selection.

CONCLUSIONS

The effectiveness of BLT in depressive symptoms and circadian disturbances of SAD was outlined by the present systematic review. The evidence about other biological and pharmacological treatments, although promising, should be replicated. A multifactorial etiopathogenesis could explain the heterogeneous clinical presentations of SAD and the complex link between mood and circadian symptoms.

Melatonin for the treatment of irritable bowel syndrome

Irritable bowel syndrome (IBS) is a common disorder characterized by recurrent abdominal pain or discomfort, in combination with disturbed bowel habits in the absence of identifiable organic cause. Melatonin (N-acetyl-5-methoxytryptamine) is a hormone produced by the pineal gland and also large number by enterochromaffin cells of the digestive mucosa. Melatonin plays an important part in gastrointestinal physiology which includes regulation of gastrointestinal motility, local anti-inflammatory reaction as well as moderation of visceral sensation. Melatonin is commonly given orally. It is categorized by the United States Food and Drug Administration as a dietary supplement. Melatonin treatment has an extremely wide margin of safety though it may cause minor adverse effects, such as headache, rash and nightmares. Melatonin was touted as a potential effective candidate for IBS treatment. Putative role of melatonin in IBS treatment include analgesic effects, regulator of gastrointestinal motility and sensation to sleep promoter. Placebo-controlled studies in melatonin suffered from heterogeneity in methodology. Most studies utilized 3 mg at bedtime as the standard dose of trial. However, all studies had consistently showed improvement in abdominal pain, some showed improvement in quality of life of IBS patients. Melatonin is a relatively safe drug that possesses potential in treating IBS. Future studies should focus on melatonin effect on gut mobility as well as its central nervous system effect to elucidate its role in IBS patients.

Qualitative analysis of therapeutic light effects on global function in Alzheimer's disease

The occurrence of Alzheimer's disease (AD) is growing, with 68% of cases occurring in women. Declines in global function exacerbated by reversal of day-night patterns, disturbed sleep-wake rhythms, and excessive daytime sleepiness make managing AD difficult. In this study, the authors examined the effect and duration of effect of therapeutic light on sleep, rest-activity, and global function in women with AD using mixed methods in a two-group experimental design with repeated measures on one factor. Twenty women with AD were randomized to experimental or control conditions. Blue-green or dim red light was delivered via cap visor in the morning. Results of the qualitative analysis of serial interviews with family and facility caregivers regarding perceived effect of light on global function are presented. Themes emerged in both groups with respect to cognition and psychosocial function. Future studies with larger samples using quantitative measures of global function are warranted to verify findings.

Pathophysiology of depression: role of sleep and the melatonergic system

Profound disturbances in sleep architecture occur in major depressive disorders (MDD) and in bipolar affective disorders. Reduction in slow wave sleep, decreased latency of rapid eye movement (REM) sleep and abnormalities in the timing of REM/non-REM sleep cycles have all been documented in patients with MDD. It is thus evident that an understanding of the basic mechanisms of sleep regulation is essential for an analysis of the pathophysiology of depressive disorders. The suprachiasmatic nucleus (SCN), which functions as the body's master circadian clock, plays a major role in the regulation of the sleep/wakefulness rhythm and interacts actively with the homeostatic processes that regulate sleep. The control of melatonin secretion by the SCN, the occurrence of high concentrations of melatonin receptors in the SCN, and the suppression of electrical activity in the SCN by melatonin all underscore the major influence which this neurohormone has in regulating the sleep/wake cycle. The transition from wakefulness to high sleep propensity is associated with the nocturnal rise of endogenous melatonin secretion. Various lines of evidence show that depressed patients exhibit disturbances in both the amplitude and shape of the melatonin secretion rhythm and that melatonin can improve the quality of sleep in these patients. The choice of a suitable antidepressant that improves sleep quality is thus important while treating a depressive disorder. The novel antidepressant agomelatine, which combines the properties of a 5-HT(2C) antagonist and a melatonergic MT(1)/MT(2) receptor agonist, has been found very effective for resetting the disturbed sleep/wake cycle and in improving the clinical status of MDD. Agomelatine has also been found useful in treating sleep problems and improving the clinical status of patients suffering from seasonal affective disorder.

Effects of exogenous melatonin and tryptophan on fecal shedding of E. coli O157:H7 in cattle

Fecal prevalence of Escherichia coli O157 in ruminants is highest in the summer decreasing to very low levels in the winter. We hypothesize that this seasonal variation is a result of physiological responses within the host animal to changing day-length. To determine the effects of melatonin (MEL) on fecal shedding of E. coli O157:H7 in cattle, eight crossbred beef steers identified as shedding E. coli O157:H7, were allotted to treatment: control or MEL (0.5 mg/kg body weight (BW); 1x) administered orally daily for 7 days. After a 5-day period of no treatment, a second MEL dose (5.0 mg/kg BW; 10x) was administered daily for 4 days. Fecal samples were collected daily for qualification of E. coli O157:H7. No differences (P > 0.10) were observed in the percentage of E. coli O157:H7 positive fecal samples in steers receiving the 1x MEL dose, however the 10x dose decreased (P = 0.05) the percentage of fecal samples E. coli O157:H7 positive. Serum MEL concentrations were higher in the 1x, but not 10x, treated animals compared to control animals. Although it is difficult to explain, this may be a result of decreasing day-length increasing serum melatonin concentrations that may have masked any treatment effect on serum melatonin. In a second similar experiment, a second group of cattle (heifers and steers) were administered tryptophan (TRP) over a 17-day experimental period (5 g/head/day for 10 days followed by 10 g/head/day for 7 days). Tryptophan had no effect (P > 0.20) on the percentage of fecal samples positive for E. coli O157. Serum TRP (P < 0.05), but not MEL (P > 0.20), concentrations were elevated in TRP-treated animals. The decrease in the number of positive fecal samples observed in the first experiment, may be related to gastrointestinal MEL, affected by the 10x, but not 1x MEL dose.

Melatonin as a modulator of the ileal brake mechanism

OBJECTIVE

The gastrointestinal tract represents the most important extrapineal source of melatonin. Intestinal melatonin release is induced by the ileal passage of nutrients and could play a part in the control of postprandial gut motility. The specific aim of this study was to determine the putative role of melatonin in the "ileal brake" reflex, an important mechanism released by ileal lipids that regulates the gastric emptying of chyme.

MATERIAL AND METHODS

Under general anaesthesia rats were fitted with ileal cannula exteriorized at the back of the neck. After a 1-week recovery, experiments were performed in conscious fasted animals. Rats were fed by gavage 1.5 ml casein hydrolyse plus 0.05% phenol red and either saline or Intralipid were continuously infused (2 ml/h) into the ileum. Gastric emptying was measured 50 min after ingestion by gastric lavage and determination of phenol red by spectrophotometry. The effects of melatonin (1 mg/kg) and melatonin antagonist S-22153 (dose-response study 0.2-25 mg/kg) were tested versus vehicle in paired experiments at 1-week intervals.

RESULTS

Ileal infusion of lipids delayed gastric emptying. During ileal infusion of lipids, melatonin antagonist S-22153, but not melatonin, potentiated the delay in gastric emptying induced by the ileal brake mechanism. The inhibition of gastric emptying induced by S-22153 was dose related. Neither melatonin nor S-22153 had noticeable effects on gastric emptying during ileal infusion of saline.

CONCLUSIONS

Our data suggest that melatonin, released in response to ileal lipids, exerts a modulatory influence that decreases the inhibitory effects of the ileal brake on gastric emptying of nutrients.

Light treatment of mood disorders

In 1981, seven patients with nonseasonal depression were treated with bright white light in 1982, bright artificial light was used to treat a manic-depressive patient with a seasonal mood cycle. In the last 20 years, a plethora of studies have further defined the depressive populations, who are responsive to light treatment; the optimal timing, intensity, spectral frequency, and duration of treatment; its comparison with other pharmacological interventions; predictors of response; side-effect profiles; viable placebo-control conditions; alternative devices and forms of administration; potential mechanisms and anatomical pathways mediating light's physiological effects; and its application to other disorders and subsyndromaI states. These studies have been conducted across multiple countries with surprisingly consistent results. Further work is needed, as highlighted in this review, to clarify the specific mechanism of action in subtypes of depressive disorders and differential age and gender effects. Although the majority of work in this area is relatively new, it behooves the reader to remember that Solomon, almost 3000 years ago, wrote in Ecclesiastes: "Truly the light is sweet and a pleasant thing it is for the eyes to behold the sun" (11:7).

Food intake inhibition by melatonin in goldfish (Carassius auratus)

Feeding regulation by monoamines, neuropeptides and certain hormones has been studied in fish, but a possible role of melatonin is unknown. The purpose of the present study was to investigate the effects of melatonin on food intake in goldfish. Fishes were housed in 12L:12D and injected with different doses of either melatonin or 2-iodomelatonin. Two routes of administration, intracerebroventricular and intraperitoneal injections, and two times of the daily photocycle, midday and midnight, were tested. Food intake was measured at 2, 5 and 8 h postinjection. Melatonin and its analog, 2-iodomelatonin intracerebroventricularly injected had no effect on food intake at any time. However, intraperitoneal injections of both indoleamines significantly reduced food intake at different postinjection times. The inhibitory effect of melatonin was blocked by intraperitoneal administration of its antagonist, luzindole. These results demonstrate the in vivo efficiency of luzindole as melatonin antagonist, and thus provide a useful experimental tool to investigate melatonin functions. In conclusion, both melatonin and its agonist 2-iodomelatonin administered peripherally, inhibit food intake in goldfish, and this inhibitory effect appears to be mediated via luzindole-sensitive melatonin receptors. Our results strongly suggest that melatonin is involved in the peripheral satiety mechanisms in goldfish.

Circadian variation of portal, arterial and venous blood levels of melatonin in pigs and its relationship to food intake and sleep

Circadian levels of melatonin were determined in the hepatic portal vein, cranial vena cava, and the lower aorta of ten juvenile pigs. Blood was sampled every hour for a total of 24 hr via temporary cannulas introduced into blood vessels under anesthesia. No peak levels of melatonin were found in the mid-scotophase, but hepatic portal concentrations peaked at 06.00 hr. Overall levels of melatonin were highest in the hepatic portal vein (range 35-65 pg/mL), followed by an artery (range 30-55 pg/mL) and the vena cava (range 25-35 pg/mL). Levels of melatonin exhibit strong variation between individual pigs, but generally the average levels from all three sources follow each other's time course. However, on occasion, melatonin levels in the hepatic portal vein varied independently from the levels in the vena cava. Large portal peaks were usually preceded by a feeding period and were associated with a subsequent period of sleep. The data indicate that: 1) there is no clear circadian rhythm of melatonin in the peripheral blood of pigs, 2) relatively little melatonin is metabolized during the first liver passage, 3) food intake may elevate melatonin levels in the hepatic portal vein, and 4) increased levels of melatonin originated in the gastrointestinal tract may induce sleep.

Determination of melatonin in pharmaceutical formulations and human plasma by gas chromatography-electron impact mass spectrometry

A simple and reliable method for gas chromatography-mass spectrometry (GC-MS) has been developed for the determination of melatonin in commercially available tablet formulations and human plasma. The dissolution of the tablets in ethyl acetate was simply obtained by sonication. The filtrate of the resultant solution, after concentration, was derivatized with pentafluoropropionic anhydride (PFPA) and analysed by GC-MS using splitless injection. The linear response range for melatonin was 5-250 ng on column. The same method can be used, with minor modifications, for the determination of melatonin in spiked human plasma in the range 50-1000 pg/mL plasma.

Determination of melatonin in rat pineal, plasma and retina by high-performance liquid chromatography with electrochemical detection

A sensitive method for the routine measurement of endogenous melatonin (MEL) in pineal, retina and plasma rat tissues has been developed using reversed-phase high-performance liquid chromatography with electrochemical detection. Quantification limit for MEL was 0.2 ng/mg protein in pineal, 15 pg/ml in plasma and 2.0 pg/mg protein in retina. To improve both MEL quantification and the reproducibility of the assay, an internal standard was used when an extraction in organic solvent was required, in contrast with other available chromatographic methods. MEL values and the circadian profile obtained in this study from both rat pineal and plasma agree with those reported previously. This method allows MEL detection in mammal retina, particularly in rat, where MEL levels are very low.

Prediction of nocturnal plasma melatonin from morning urinary measures

A growing literature indicates that blood levels of the hormone melatonin may have important implications for human health and well-being. Melatonin is synthesized and released into the general circulation at night, however, and it is seldom feasible to draw blood samples at night in epidemiological studies. There is some evidence that levels of urinary melatonin and of 6-sulfatoxymelatonin (aMT6s), the major metabolite of melatonin, accurately reflect nocturnal plasma melatonin. If this is the case, urinary assays could be powerful tools for epidemiological studies. A laboratory-based study was performed to examine the relationships between nocturnal plasma melatonin, morning urinary melatonin, and morning urinary aMT6s levels in 78 men. The relationship between total nocturnal plasma melatonin and both urinary aMT6s corrected for creatinine and urinary melatonin is significant. Combining the two urinary measures accounts for 72% of the variance in total plasma melatonin. Peak nocturnal plasma melatonin also was significantly related to urinary melatonin and to aMT6s. The urinary measures show good sensitivity and specificity in identifying individual differences in nocturnal plasma melatonin levels. These results support the inclusion of morning urine samples to assess the contribution of the hormone melatonin in occupational or residential studies involving healthy, young men.

Melatonin concentrations in serum and tissues of porcine gastrointestinal tract and their relationship to the intake and passage of food

Melatonin concentrations were determined in serum and 10 segments of the gastrointestinal tract (GIT) of 48 pigs (100 kg weight). The animals were fasted for 30 hr and then sacrificed 0, 1, 2, 5, 10, and 20 hr after refeeding. Peak amount of gastric digesta (2,428 g) and ileum digesta (850 g) were observed 1 hr and 5 hr, after refeeding, respectively. Conversely, colon content reached a minimal weight (726 g) at 2 hr after refeeding. Serum levels of melatonin increased from 3.4 pg/ml to 15.5 pg/ml (peak 5 hr after refeeding). Melatonin levels in GIT tissues before refeeding varied from 23.8 pg/g (stomach-fundus) to 62.1 pg/g (rectum). Increasingly higher levels of melatonin were detected in the distal segments of the GIT. Higher melatonin levels after refeeding were observed in most GIT tissues except the rectum. In most tissues, peak melatonin values were detected 5 hr after refeeding. A significant change in weight of digesta across time (P < 0.05) was detected in the stomach, ileum, and cecum. Similar changes in melatonin levels across time were found in most tissues except the esophagus, stomach (cardia and pylorus), and rectum. Adjacent GIT tissues exhibited similar (P < 0.05) melatonin levels. The GIT melatonin levels correlated best with the variation of digesta weight in the ileum. In addition, the increase of serum melatonin levels correlated best with the increase of GIT melatonin levels in the distal part of the GIT. Our results suggest that melatonin produced in the ileum, cecum, and colon may contribute significantly to the short-term increase of serum melatonin levels observed after refeeding.