Melatonin References

Endocrine. 2005; 27(2):179-88 (ISSN: 0969-711X)

Blask DE; Dauchy RT; Sauer LA
Laboratory of Chrono-Neuroendocrine Oncology, Bassett Research Institute, Cooperstown, NY 13326, USA. david.blask@basset.org

Physiological and pharmacological blood concentrations of melatonin inhibit tumorigenesis in a variety of in vivo and in vitro experimental models of neoplasia. Evidence indicates that melatonin's anticancer effects are exerted via inhibition of cell proliferation and a stimulation of differentiation and apoptosis. A new mechanism by which physiological and pharmacological blood levels of melatonin inhibit cancer growth in vivois via a melatonin-induced suppression of tumor linoleic acid (LA) uptake and its metabolism to the important mitogenic signaling molecule 13-hydroxyoctadecadienoic acid (13-HODE). Melatonin suppresses cAMP formation and inhibits tumor uptake of LA and its metabolism to 13-HODE via a melatonin receptor-mediated mechanism in both tissue-isolated rat hepatoma 7288 CTC and human breast cancer xenografts.

It has been postulated that in industrialized societies, light at night, by suppressing melatonin production, poses a new risk for the development of breast cancer and, perhaps, other cancers as well. In support of this hypothesis, light during darkness suppresses nocturnal melatonin production and stimulates the LA metabolism and growth of rat hepatoma and human breast cancer xenografts. Nocturnal dietary supplementation with melatonin, at levels contained in a melatonin-rich diet, inhibits rat hepatoma growth via the mechanisms described above. The nocturnal melatonin signal organizes tumor metabolism and growth within circadian time structure that can be further reinforced by appropriately timed melatonin supplementation. Dietary melatonin supplementation working in concert with the endogenous melatonin signal has the potential to be a new preventive/therapeutic strategy to optimize the host/cancer balance in favor of host survival and quality of life.

Adv Exp Med Biol. 1999; 467:217-26 (ISSN: 0065-2598)

Maestroni GJ
Istituto Cantonale Di Patologia, Center For Experimental Pathology, Locarno, Switzerland. icpcps@guest.cscs.ch

Maintenance of health depends on the ability to respond appropriately to environmental stressors via reciprocal interactions between the body and the brain. In this context, it is well recognized that the pineal hormone melatonin (MLT) plays an important role. T-helper cells bear G-protein-coupled MLT cell membrane receptors and, perhaps, MLT nuclear receptors. Activation of MLT receptors enhances the release of T-helper cell cytokines, such as gamma-interferon and interleukin-2 (IL-2), as well as activation of novel opioid cytokines which crossreact immunologically with both interleukin-4 and dynorphin B. MLT has been reported also to enhance the production of interleukin-1, interleukin-6 and interleukin-12 in human monocytes. These mediators may counteract secondary immunodeficiencies, protect mice against lethal viral and bacterial diseases, synergize with IL-2 against cancer and influence hematopoiesis. Hematopoiesis is influenced by MLT-induced-opioids (MIO) acting on kappa 1-opioid receptors present on bone marrow macrophages.

Clinically, MLT could amplify the anti-tumoral activity of low dose IL-2, induce objective tumor regression, and prolong progression-free time and overall survival. MLT seems to be required for the effectiveness of low dose IL-2 in those neoplasias that are generally resistant to IL-2 alone. Similar findings were obtained in a study in which MLT was combined with gamma-interferon in metastatic renal cell carcinoma. In addition, MLT in combination with low-dose IL-2 was able to neutralize the surgery-induced lymphocytopenia in cancer patients. IL-2 treatment in patients results in activation of the immune system and creates the most suitable biological background for MLT.

The finding that MLT stimulates IL-12 production from human monocytes only if incubated in presence of IL-2 further supports this concept. On the other hand, high concentrations of MLT have been found in human breast cancer tissue. The MLT concentration, which was 3 orders of magnitude higher than that present in the plasma, correlated positively with good prognostic markers such as estrogen receptor status and nuclear grade. Whether this relates to the immunoneuroendocrine action of MLT remains to be established. Clinical studies are needed on the effect of MLT in combination with IL-2 or other cytokines in cancer patients and viral diseases including HIV-infected patients.

Clin Endocrinol (Oxf). 1998; 49(2):179-83 (ISSN: 0300-0664)

Wikner J; Hirsch U; Wetterberg L; Röjdmark S
Karolinska Institute, Endocrinology Section, Department of Internal Medicine, Stockholm Söder Hospital.

OBJECTIVE: Most patients with fibromyalgic syndrome (FMS) complain of sleep disturbances, fatigue, and pain. These symptoms might be a consequence of changed melatonin (MT) secretion, since MT is known to have sleep promoting properties. Moreover, serum concentrations of two MT precursors (tryptophan and serotonin)--affecting both sleep and pain perception--appear to be low in patients with FMS. Therefore, the objective of this investigation was to study whether serum MT (s-MT) level is also low in these patients. DESIGN: Eight patients with FMS and 8 healthy sex-, BMI-, and age-matched controls were included in the study. s-MT concentrations were determined every second hour between 1800 and 0800 h. Urine was collected between 2200 and 0700 h for determination of urinary MT excretion.

To evaluate total MT secretion between 1800 and 0800 h and MT secretion during the hours of darkness (between 23 and 07 h) individual MT areas under the curve (AUC) were calculated and expressed as group means. RESULTS: The FMS patients had a 31% lower MT secretion than healthy subjects during the hours of darkness (MT AUC 2300-0700 h (mean +/- SEM): 1.70 +/- 0.17 vs 2.48 +/- 0.38 nmol/l; P < 0.05). Also the s-MT peak value was significantly lower in the patient group: 0.28 +/- 0.03 vs 0.44 +/- 0.06 nmol/l; P < 0.05). CONCLUSION: Patients with fibromyalgic syndrome have a lower melatonin secretion during the hours of darkness than healthy subjects. This may contribute to impaired sleep at night, fatigue during the day, and changed pain perception.

Mutat Res. 2003; 539(1-2):1-8 (ISSN: 0027-5107)

Liu X; Zhao J; Zheng R
School of Life Sciences, Lanzhou University, 730000 Lanzhou, PR China.

The purpose of this study was to assess DNA damage of tumor-associated lymphocytes (TALs) in malignant pleural effusion (MPE), the total antioxidant capacity (TAC) of plasma and MPE from patients with carcinoma, and DNA repair effect of melatonin. TAC of plasma was measured in 28 cancer patients with MPE and in 33 healthy persons, and also TAC of MPE supernatant was measured in these patients. DNA damages of peripheral blood mononuclear cells (PBMCs) and of TALs were assessed using comet assay. The TAC of plasma was remarkably lower in cancer patients (8.41+/-1.78 U/ml) than that in healthy persons (10.52+/-1.64 U/ml, P<0.001).

The TAC of MPE supernatant (6.34+/-1.57 U/ml) was significantly lower than that of plasma in cancer patients (8.41+/-1.78 U/ml, P<0.001). The comet percentage of PBMCs was higher in cancer patients (16.8+/-7.9) than that in healthy persons (10.4+/-4.9, P<0.01). Within cancer patients, the comet percentage of TALs (41.9+/-11.7) was significantly higher than that of PBMCs (16.8+/-7.9, P<0.001). A negative correlation was observed between the TAC of MPE supernatant and the comet percentage of TALs in patients (r=-0.538, P<0.01). After treatment with melatonin, comet percentage of TALs declined significantly from 42.6+/-12.8 to 27.1+/-9.9 (P<0.001). These data show that lower TAC of MPE supernatant may be related to higher degree of DNA damage of TALs and that melatonin may facilitate the repair of the damaged DNA.

J Clin Endocrinol Metab. 1988; 66(3):648-52 (ISSN: 0021-972X)

Waldhauser F; Weiszenbacher G; Tatzer E; Gisinger B; Waldhauser M; Schemper M; Frisch H
Department of Pediatrics, University of Vienna, Austria.

The available data on potential alterations in serum melatonin (MLT) levels during a human lifetime are fragmentary and inconsistent. We, therefore, measured day- and nighttime serum MLT concentrations in 367 subjects (210 males and 157 females), aged 3 days to 90 yr. Blood samples were collected between 0730 and 1000 h and between 2300 and 0100 h. Serum MLT levels were measured by RIA. The mean nighttime serum MLT concentration was low during the first 6 months of life, i.e. 27.3 +/- 5.4 (+/- SE) pg/mL (0.12 +/- 0.02 nmol/L). It then increased to a peak value at 1-3 yr of age [329.5 +/- 42.0 pg/mL; (1.43 +/- 0.18 nmol/L)], and it was considerably lower [62.5 +/- 9.0 pg/mL; (0.27 +/- 0.04 nmol/L)] in individuals aged 15-20 yr. During the following decades serum MLT declined moderately until old age (70-90 yr of age), i.e. 29.2 +/- 6.1 pg/mL (0.13 +/- 0.03 nmol/L).

This biphasic MLT decline follows 2 exponential functions with different slopes (from age 1-20 yr: r = -0.56; P less than 0.001; y = 278.7 X e -0.09x; from age 20-90 yr: r = -0.44; P less than 0.001; y = 84.8 X e -0.017x). The decrease in nocturnal serum MLT in children and adolescents (1-20 yr) correlated with the increase in body weight (r = -0.54; P less than 0.001) and body surface area (r = -0.71; P less than 0.001). At a later age (20-90 yr) there was no correlation among these variables. Daytime serum MLT levels were low and no age-related alterations were found. This study revealed major age-related alterations in nocturnal serum MLT levels. The negative correlation between serum MLT and body weight in childhood and adolescence is evidence that expansion of body size is responsible for the huge MLT decrease during that period. The moderate decline at older ages must derive from other factors.

J Neural Transm. 2005; 112(3):349-58 (ISSN: 0300-9564)

Sofic E; Rimpapa Z; Kundurovic Z; Sapcanin A; Tahirovic I; Rustembegovic A; Cao G
Neuroscience Laboratory, Jean Mayer USDA Human Nutrition Research Center on Aging, Tufts University, Boston, MA, USA. esofic@pmf.unsa.ba

The aim of this study was to elucidate the antioxidant behaviour of melatonin (M) and determine its activity-structure relationship. M or 5-metoxy-N acetyltriptamine is a neurohormone secreted by the pineal gland, which plays a proven role in maintaining sleep-wake rhythms. The antioxidant capacity of M was analysed using the oxygen radical absorbance capacity (ORAC) assay. Furthermore, spectral measurements for aerobic photolytic reaction of neutral red (NR) and degree of inhibition of photolysis with M, glutathione (GSH), ascorbic acid (AA) and vitamin E analogue Trolox were studied at room temperature 25 degrees C, using visible (VIS) and ultra-violet (UV) radiations. In the ORAC assay 2,2-azobis (2-amidino-propane)dihydrochloride (AAPH) a peroxyl radical generator, ROO degrees ; H2O2-Cu2+, mainly a hydroxyl radical generator, degrees OH; and Cu2+ a transition metal were used.

Although some studies indicated that M is a powerful antioxidant, no one has compared its antioxidant capacities with GSH, E-vitamin and AA, using three free radical (FR) generators in an assay which utilizes an area-under curve technique and thus combines both inhibition time and inhibition degree of FR action by an antioxidant into a single quantity. In the current study, we used ORAC assay with three FR generators. The assay is based on propensity of the fluorescence emitted by the protein beta-phycoerythrin (beta-PE) from porphyridium cruentum to be quenched when exposed to FR action. M in our experiments acted as a universal antioxidant against ROO degrees and degrees OH radicals. Also, M served as an antioxidant in the presence of Cu2+. M, which is a lipid-soluble compound, was a twice more powerful antioxidant than vitamin E, and four times than AA or GSH. Furthermore, M inhibited aerobic photolysis of NR photoinduced with VIS and UV rays faster and more effectively, than AA, GSH or vitamin E. AA with NR, under aerobic conditions during irradiation with VIS and UV acted as a pro-oxidant. M may be the premier molecule to protect the cells from oxidative stress.

J Pineal Res. 1998; 25(3):177-83 (ISSN: 0742-3098)

Jean-Louis G; von Gizycki H; Zizi F
Department of Psychiatry, University of California, San Diego, USA. gjeanlouis@ucsd.edu

The effects of immediate-release melatonin on circadian rest-activity profiles, cognition, and mood were investigated in ten elderly individuals with self-reported sleep-wake disturbances. Melatonin (6 mg), administered 2 hr before habitual bedtime, enhanced the rest-activity rhythm and improved sleep quality as observed in a reduction in sleep onset latency and in the number of transitions from sleep to wakefulness. However, total sleep time was not significantly increased nor was wake within sleep significantly reduced. The ability to remember previously learned items improved along with a significant reduction in depressed moods. No side effects or contraindications were reported by any of our participants during the 10 day trials. These data suggest that melatonin can safely improve some aspects of sleep, memory, and mood in the elderly in short-term use.

Exp Gerontol. 2001; 36(2):297-310 (ISSN: 0531-5565)

Bellipanni G; Bianchi P; Pierpaoli W; Bulian D; Ilyia E
Menopause Center, Madonna delle Grazie Health Institute, Velletri, Rome, Italy.

In aging humans, night levels of melatonin (MEL) decline progressively. Also thyroid and gonadal functions decline during aging while gonadotropins (luteotropic hormone (LH) and follicle stimulating hormone (FSH)) steadily increase. A desynchronization of pineal circadian cyclicity as expressed by the progressive decrease of the MEL night peak may be permissively linked to the onset and progression of menopause. We studied the effects of exogenous, evening administration of MEL on the level of hormones which are known to be involved in the genesis and progression of menopause. Perimenopausal and menopausal women from 42 to 62years of age with no pathology or medication were selected. MEL was measured in saliva to divide them into low, medium and high-MEL patients. Half of them took 3mg MEL and half of them Placebo at bedtime (10-12p.m.) in a fully randomized and double-blind fashion. Three and six months later blood was taken for determination of pituitary (LH, FSH), ovarian, and thyroid hormones I(T3 and T4).

All women taking MEL with low basal level of MEL and/or Placebo for three and six months showed a significant increase in levels of thyroid hormones. Before initiation of the study, a negative correlation was found in all women between LH, FSH and basal MEL levels. Within six months of treatment, MEL produced a significant diminution of LH in the younger women (43 to 49year-old), while no effect was seen in the older women (50-62years old). A decrement of FSH was observed in MEL-treated women with low basal MEL levels. In addition, most MEL-treated women reported a general improvement of mood and a significant mitigation of depression. MEL decline during aging may thus signal the derangement of pineal and pituitary-controlled ovarian cyclicity and the progressive quenching of fertility in women. These findings seem to show a recovery of pituitary and thyroid functions in MEL-treated women, towards a more juvenile pattern of regulation.

Endocrinology. 1999; 140(2):1009-12 (ISSN: 0013-7227)

Rasmussen DD; Boldt BM; Wilkinson CW; Yellon SM; Matsumoto AM VA Puget Sound Health Care System, and Department of Medicine, University of Washington, Seattle 98195, USA. drasmuss@u.washington.edu

Human and rat pineal melatonin secretion decline with aging, whereas visceral fat and plasma insulin levels increase. Melatonin modulates fat metabolism in some mammalian species, so these aging-associated melatonin, fat and insulin changes could be functionally related. Accordingly, we investigated the effects of daily melatonin supplementation to male Sprague-Dawley rats, starting at middle age (10 months) and continuing into old age (22 months). Melatonin was added to the drinking water (92% of which was consumed at night) at a dosage (4 microg/ml) previously reported to attenuate the aging-associated decrease in survival rate in male rats, as well as at a 10-fold lower dosage. The higher dosage produced nocturnal plasma melatonin levels in middle-aged rats which were 15-fold higher than in young (4 months) rats; nocturnal plasma melatonin levels in middle-aged rats receiving the lower dosage were not significantly different from young or middle-aged controls. Relative (% of body wt) retroperitoneal and epididymal fat, as well as plasma insulin and leptin levels, were all significantly increased at middle age when compared to young rats. All were restored within 10 weeks to youthful (4 month) levels in response to both dosages of melatonin.

Continued treatment until old age maintained suppression of visceral (retroperitoneal + epididymal) fat levels. Plasma corticosterone and total thyroxine (T4) levels were not significantly altered by aging or melatonin treatment. Plasma testosterone, insulin-like growth factor I (IGF-I) and total triiodothyronine (T3) decreased by middle age; these aging-associated decreases were not significantly altered by melatonin treatment. Thus, visceral fat, insulin and leptin responses to melatonin administration may be independent of marked changes in gonadal, thyroid, adrenal or somatotropin regulation. Since increased visceral fat is associated with increased insulin resistance, diabetes, and cardiovascular disease, these results suggest that appropriate melatonin supplementation may potentially provide prophylaxis or therapy for some prominent pathologies associated with aging.

Clin Rheumatol. 2000; 19(1):9-13 (ISSN: 0770-3198)

Citera G; Arias MA; Maldonado-Cocco JA; Lazaro MA; Rosemffet MG; Brusco LI; Scheines EJ; Cardinalli DP
Rheumatology Section, Instituto de Rehabilitacion Psicofosica and Department of Physiology, Facultad de Medicina, Universidad de Buenos Aires, Argentina.

The aim of the study was to determine the possible effect of melatonin treatment on disturbed sleep, fatigue and pain symptoms observed in fibromyalgia (FM) patients. Twenty-one consecutive patients with FM were included in an open 4-week-duration pilot study. Before and after treatment with melatonin 3 mg at bedtime, patients were evaluated using tender point count by palpation of 18 classic anatomical regions, pain score in four predesignated areas, pain severity on a 10 cm visual analogue scale (VAS), sleep disturbances, fatigue, depression, anxiety, and patient and physician global assessments, also by a VAS. Urine 6-sulphatoxymelatonin levels (aMT-6S) were measured in the patients and 20 age- and sex-matched controls. Nineteen patients completed the study. One patient withdrew because of migraine and another was lost to follow-up.

At day 30, median values for the tender point count and severity of pain at selected points, patient and physician global assessments and VAS for sleep significantly improved with melatonin treatment. Other variables improved but did not reach statistical significance. Adverse events were mild and transient. Lower levels of aMT-6S were found in FM patients compared with normal median controls (+/-SD, 9.16 +/- 7.9 microg/24 h vs 16.8 +/- 12.8 microg/24 h) (p = 0.06). Although this is an open study, our preliminary results suggest that melatonin can be an alternative and safe treatment for patients with FM. Double-blind placebo controlled studies are needed.

Neuro Endocrinol Lett. 2001; 22(2):121-7 (ISSN: 0172-780X)

Ostrowska Z; Kos-Kudla B; Marek B; Swietochowska E; Garski J
Department of Clinical Biochemistry, Silesian Medical Academy, Pl. Traugutta 2, 41-800 Zabrze, Poland.

BACKGROUND: Few experimental and clinical studies show that melatonin (MEL) can play a significant part to modulate circadian bone metabolism. On this basis it was suggested that MEL secretion which altered during 24-h in obese women could be of importance to regulate bony mass defect after menopause. OBJECTIVE: The aim of the study was to prove if there were any connection between changes in 24-h profile of serum MEL levels and circadian metabolism of type I collagen in postmenopausal women with visceral obesity. METHODS: The relationship of 24-h profile of salivary MEL and circadian metabolism of type I collagen (as assessed by measuring saliva concentrations of carboxyterminal propeptide of type I procollagen--PICP and cross-linked carboxyterminal telopeptide of type I collagen--ICTP) was investigated in 26 women with visceral obesity (33.5 < BMI < 42.1 kg/m(2)) and 18 healthy volunteers with correct body mass (21 < BMI < 24.5 kg/m(2); 0.73 < WHR < 0.76).

The specimens were collected at subjects' home at 3 h intervals during a 24 h span. The age range of all subjects was 52-60 years. RESULTS: In all the obese women studied a tendency to suppress circadian levels of tested biochemical markers of bone metabolism was observed (especially regarding ICTP); those alterations were accompanied by substantial increment in MEL concentrations during the day. Significant and negative correlation was found between values of acrophase MEL and PICP rhythms and both amplitude and acrophase of MEL and ICTP rhythms. CONCLUSION: Our results confirm hypothesis that alterations in MEL concentrations might have a protective effect against postmenopausal loss of bone mass.

J Bone Miner Res. 2002; 17(7):1219-29 (ISSN: 0884-0431)

Koyama H; Nakade O; Takada Y; Kaku T; Lau KH
Musculoskeletal Disease Center, Jerry L. Pettis Memorial Veterans Affairs Medical Center, Loma Linda, California 92357, USA.

This study evaluated if melatonin would increase bone mass in mice. Four groups of 4-week-old male ddy mice received daily injections of vehicle or 1, 5, or 50 mg/kg of melatonin, respectively, for 4 weeks. Treatment with 5 mg/kg per day or 50 mg/kg per day of melatonin significantly increased bone mineral density (BMD; by 36%, p < 0.005) and bone mass (bone volume per tissue volume [BV/TV] by 49%, p < 0.01, and trabecular thickness [Tb.Th] by 19%, p < 0.05). This treatment significantly reduced bone resorption parameters (i.e., osteoclast surface [Oc.S/bone surface [BS]] by 74%,p < 0.05, and osteoclast number [N.Oc/BS] by 76%,p < 0.005) but did not increase histomorphometric bone formation parameters (i.e., bone formation rate [BFR/ BS], mineral apposition rate [MAR], and osteoid volume [OV/TV]), indicating that melatonin increases bone mass predominantly through suppression of bone resorption. Melatonin (1-500 microM) in vitro caused dose-dependent reduction (p < 0.001 for each) in the number and area of resorption pits formed by osteoclasts derived from bone marrow cells but not those formed by isolated rabbit osteoclasts.

Because RANKL increases, while osteoprotegerin (OPG) serves as a soluble decoy receptor for RANKL to inhibit osteoclast formation and activity, the effect of melatonin on the expression of RANKL and OPG in mouse MC3T3-E1 osteoblastic cells was investigated. Melatonin (5-500 microM) increased in a dose-dependent manner and reduced the mRNA level of RANKL and both mRNA and protein levels of OPG in MC3T3-E1 cells (p < 0.001 for each). In summary, these findings indicated for the first time that melatonin at pharmacologic doses in mice causes an inhibition of bone resorption and an increase in bone mass. These skeletal effects probably were caused by the melatonin-mediated down-regulation of the RANKL-mediated osteoclast formation and activation

Support Care Cancer. 2002; 10(2):110-6 (ISSN: 0941-4355)

Lissoni P U.O. di Oncologia Medica e Radioterapia, Ospedale S. Gerardo dei Tintori, 20052 Monza (MI), Italy. oncologia@genie.it

Melatonin (MLT) is the main hormone released from the pineal gland and has proved to have physiological antitumor activity. MLT has been shown to exert anticancer activity through several biological mechanisms: antiproliferative action, stimulation of anticancer immunity, modulation of oncogene expression, and anti-inflammatory, anti-oxidant and anti-angiogenic effects. Several experimental studies have shown that MLT may inhibit cancer cell growth, and preliminary clinical studies seem to confirm its anticancer property in humans. In addition, MLT may have other biological effects, which could be useful in the palliative therapy of cancer, namely anticachectic, anti-asthenic and thrombopoietic activities. On this basis, the present clinical investigation was performed in an attempt at better definition of the therapeutic properties of MLT in human neoplasms. In a first clinical study, we evaluated the effects of MLT in a group of 1,440 patients with untreatable advanced solid tumors, who received supportive care alone or supportive care plus MLT. In a second study, we evaluated the influence of MLT on the efficacy and toxicity of chemotherapy in a group of 200 metastatic patients with chemotherapy-resistant tumor histotype, who were randomized to receive chemotherapy alone or chemotherapy plus MLT. In both studies, MLT was given orally at 20 mg/day during the dark period of the day.

The frequency of cachexia, asthenia, thrombocytopenia and lymphocytopenia was significantly lower in patients treated with MLT than in those who received supportive care alone. Moreover, the percentage of patients with disease stabilization and the percentage 1-year survival were both significantly higher in patients concomitantly treated with MLT than in those treated with supportive care alone. The objective tumor response rate was significantly higher in patients treated with chemotherapy plus MLT than in those treated with chemotherapy alone. Moreover, MLT induced a significant decline in the frequency of chemotherapy-induced asthenia, thrombocytopenia, stomatitis, cardiotoxicity and neurotoxicity. These clinical results demonstrate that the pineal hormone MLT may be successfully administered in medical oncology in the supportive care of untreatable advanced cancer patients and for the prevention of chemotherapy-induced toxicity.

Chronobiol Int. 2001; 18(1):99-107 (ISSN: 0742-0528)

Cugini P; Touitou Y; Bogdan A; Auzby A; Pellegrino AM; Fontana S; Vacca K; Siena GD; Di Rosa R; Zannella FP; Zannella P; Zannella A; Sepe FA; Sepe L
Department of Clinical Sciences, University of Rome La Sapienza, Italy.

The study investigates the circadian rhythm (CR) of urinary 6-sulphatoxy-melatonin (aMT6s) in long-living (longevous) subjects and their progeny. The aim is to detect whether or not the melatonin CR is a physiological feature associated with healthy longevity. The aMT6s CR was investigated in 10 longevous subjects, 8 of their children and 9 of their grandchildren, all in good health. Control data were obtained respectively from 13 adult subjects and 9 young subjects, in good health, but characterized by a negative family history for longevity. All the subjects were born and living in the same city. The study was performed in the summer of 1996. The aMT6s CR was found to persist in longevous subjects, being characterized by a lower mesor and amplitude.

The aMT6s CR was found not to show properties consistently different in children and grandchildren as compared respectively to their adult and young controls. Because of its preservation in longevous subjects, it can be argued that the melatonin CR is a physiological feature associated with healthy longevity. Because of the comparability of aMT6s CR in children and grandchildren, with respect to their controls without a positive family history of longevity, it can be argued that the melatonin CR is not a marker that can be used for an earlier identification of the candidates for longevity.

J Biol Rhythms. 1997; 12(5):457-66 (ISSN: 0748-7304)

Voultsios A; Kennaway DJ; Dawson D
Department of Obstetrics and Gynaecology, University of Adelaide Medical School, South Australia.

There are many situations in which it would be useful to know the phase state of the biological clock. It is recognized that measurement of melatonin levels can provide this information, but traditionally blood has been used for the analysis, and there are many problems in extending the measurements into the home or field situations. The aim of this study was to develop and validate a salivary melatonin radioimmunoassay and to compare results obtained against a plasma assay for determining the onset of melatonin secretion. The assay developed was sensitive (4.3 pM) and required only 200 microliters of sample. A rhythm in melatonin was detected in saliva, peaking at approximately 120 pM or 30% of the plasma levels. Using an objective criterion for determining the onset of secretion (mean +/- 2 standard deviations of three daytime samples), the time of onset was shown to exhibit low intraindividual variability (coefficient of variation = 1.5%-4.3%).

The time of onset determined using saliva was significantly correlated with the plasma onset (r = .70, p < .05). The onsets determined were 22:30 h +/- 22 min for the saliva and 21:50 h +/- 16 min for plasma for 17 subjects. Similarly, the acrophases of the saliva and plasma melatonin rhythms were significantly correlated. Neither posture alone nor changes in posture affected the calculation of the onset of melatonin secretion using the saliva approach. Very high saliva flow rates induced by citric acid resulted in lower melatonin concentrations compared to the gentle chewing on parafin film. These results firmly establish the use of salivary melatonin measurements for phase typing of the melatonin rhythm in humans.

J Physiol. 2004; 561(Pt 1):339-51 (ISSN: 0022-3751)

Rajaratnam SM; Middleton B; Stone BM; Arendt J; Dijk DJ School of Biomedical and Molecular Sciences, University of Surrey, UK. shantha.rajaratnam@med.monash.edu.au

The rhythm of plasma melatonin originating from the pineal gland and driven by the circadian pacemaker located in the suprachiasmatic nucleus is closely associated with the circadian (approximately 24 h) variation in sleep propensity and sleep spindle activity in humans. We investigated the contribution of melatonin to variation in sleep propensity, structure, duration and EEG activity in a protocol in which sleep was scheduled to begin during the biological day, i.e. when endogenous melatonin concentrations are low. The two 14 day trials were conducted in an environmental scheduling facility. Each trial included two circadian phase assessments, baseline sleep and nine 16 h sleep opportunities (16.00-08.00 h) in near darkness. Eight healthy male volunteers (24.4 +/- 4.4 years) without sleep complaints were recruited, and melatonin (1.5 mg) or placebo was administered at the start of the first eight 16 h sleep opportunities.

During melatonin treatment, sleep in the first 8 h of the 16 h sleep opportunities was increased by 2 h. Sleep per 16 h was not significantly different and approached asymptotic values of 8.7 h in both conditions. The percentage of rapid eye movement (REM) sleep was not affected by melatonin, but the percentage of stage 2 sleep and sleep spindle activity increased, and the percentage of stage 3 sleep decreased. During the washout night, the melatonin-induced advance in sleep timing persisted, but was smaller than on the preceding treatment night and was consistent with the advance in the endogenous melatonin rhythm. These data demonstrate robust, direct sleep-facilitating and circadian effects of melatonin without concomitant changes in sleep duration, and support the use of melatonin in the treatment of sleep disorders in which the circadian melatonin rhythm is delayed relative to desired sleep time.