Nutritional and lifestyle correlates of the cancer-protective hormone melatonin

Exploring the Mechanical Perspective of a New Anti-Tumor Agent: Melatonin

Melatonin is a serotonin-derived pineal gland hormone with many biological functions like regulating the sleep-wake cycle, circadian rhythm, menstrual cycle, aging, immunity, and antioxidants. Melatonin synthesis and release are more pronounced during the night, whereas exposure to light decreases it. Evidence is mounting in favor of the therapeutic effects of melatonin in cancer prevention, treatment and delayed onset in various cancer subtypes. Melatonin exerts its anticancer effect through modification of its receptors such as melatonin 1 (MT1), melatonin 2 (MT2), and inhibition of cancer cell proliferation, epigenetic alterations (DNA methylation/demethylation, histone acetylation/deacetylation), metastasis, angiogenesis, altered cellular energetics, and immune evasion. Melatonin performs a significant function in immune modulation and enhances innate and cellular immunity. In addition, melatonin has a remarkable impact on epigenetic modulation of gene expression and alters the transcription of genes. As an adjuvant to cancer therapies, it acts by decreasing the side effects and boosting the therapeutic effects of chemotherapy. Since current treatments produce drug-induced unwanted toxicities and side effects, they require alternate therapies. A recent review article attempts to summarize the mechanistic perspective of melatonin in different cancer subtypes like skin cancer, breast cancer, hepatic cancer, renal cell cancer, non-small cell lung cancer (NSCLC), colon oral, neck, and head cancer. The various studies described in this review will give a firm basis for the future evolution of anticancer drugs.

Influence of pH, temperature, and light on the stability of melatonin in aqueous solutions and fruit juices

The ability to predict melatonin stability during food processing or storage is important. Therefore, the degradation of melatonin in both aqueous solutions and fruit juice samples was investigated. The pH values of aqueous solutions were set over a pH range from 1 to 13 and at four different temperatures (60, 70, 80 and 90 °C). The highest remaining melatonin (C_R) was observed in the lowest pH solution (pH = 1, C_R > 65%). Melatonin concentrations decreased with rising pH levels from pH 4 to 13 during storage time. The thermal degradation rate constant of melatonin (k) values obtained followed the order: k_90°C (0.175) >k_80°C (0.123) >k_70°C (0.082) >k_60°C (0.027). Thermal degradation kinetics followed the first-order reaction model with a high range of coefficients of determination (0.9744 < R² < 0.995). The temperature also affected on melatonin degradation in fruit juices which the degradation rate was increased with the presence of light and high temperature. Our results can be used as guidelines to develop a processing method that predicts melatonin degradation during thermal processing of food products.

Melatonin and health: an umbrella review of health outcomes and biological mechanisms of action

BACKGROUND

Our aims were to evaluate critically the evidence from systematic reviews as well as narrative reviews of the effects of melatonin (MLT) on health and to identify the potential mechanisms of action involved.

METHODS

An umbrella review of the evidence across systematic reviews and narrative reviews of endogenous and exogenous (supplementation) MLT was undertaken. The Oxman checklist for assessing the methodological quality of the included systematic reviews was utilised. The following databases were searched: MEDLINE, EMBASE, Web of Science, CENTRAL, PsycINFO and CINAHL. In addition, reference lists were screened. We included reviews of the effects of MLT on any type of health-related outcome measure.

RESULTS

Altogether, 195 reviews met the inclusion criteria. Most were of low methodological quality (mean -4.5, standard deviation 6.7). Of those, 164 did not pool the data and were synthesised narratively (qualitatively) whereas the remaining 31 used meta-analytic techniques and were synthesised quantitatively. Seven meta-analyses were significant with P values less than 0.001 under the random-effects model. These pertained to sleep latency, pre-operative anxiety, prevention of agitation and risk of breast cancer.

CONCLUSIONS

There is an abundance of reviews evaluating the effects of exogenous and endogenous MLT on health. In general, MLT has been shown to be associated with a wide variety of health outcomes in clinically and methodologically heterogeneous populations. Many reviews stressed the need for more high-quality randomised clinical trials to reduce the existing uncertainties.

A systematic review on the role of vitamins, minerals, proteins, and other supplements for the treatment of cachexia in cancer: a European Palliative Care Research Centre cachexia project

We provide a systematic review to support the European Palliative Care Research Collaboration development of clinical guidelines for cancer patients suffering from cachexia. CENTRAL, MEDLINE, PsycINFO, ClinicalTrials.gov, and a selection of cancer journals have been searched up until 15 April 2016. The systematic literature research yielded 4214 publications with 21 of these included in the final evaluation. Regarding minerals, our search identified only one study examining the use of magnesium with no effect on weight loss. As far as vitamins are concerned, vitamin E in combination with omega-3 fatty acids displayed an effect on survival in a single study, vitamin D showed improvement of muscle weakness in prostate cancer patients, and vitamin C supplementation led to an improvement of various quality of life aspects in a sample with a variety of cancer diagnoses. For proteins, a combination therapy of β-hydroxy-β-methylbutyrate (HMB), arginine, and glutamine showed an increase in lean body mass after 4 weeks in a study of advanced solid tumour patients, whereas the same combination did not show a benefit on lean body mass in a large sample of advanced lung and other cancer patients after 8 weeks. L-carnitine led to an increase of body mass index and an increase in overall survival in advanced pancreatic cancer patients. Adverse effects of food supplementation were rare and showed mild intensity. There is not enough solid evidence for the use of minerals, vitamins, proteins, or other supplements in cancer. No serious adverse effects have been reported with dietary supplementation.

The Pathophysiologic Role of Disrupted Circadian and Neuroendocrine Rhythms in Breast Carcinogenesis

Most physiological processes in the brain and body exhibit daily (circadian) rhythms coordinated by an endogenous master clock located in the suprachiasmatic nucleus of the hypothalamus that are essential for normal health and functioning. Exposure to sunlight during the day and darkness at night optimally entrains biological rhythms to promote homeostasis and human health. Unfortunately, a major consequence of the modern lifestyle is increased exposure to sun-free environments during the day and artificial lighting at night. Additionally, behavioral disruptions to circadian rhythms (ie, repeated transmeridian flights, night or rotating shift work, or sleep disturbances) have a profound influence on health and have been linked to a number of pathological conditions, including endocrine-dependent cancers. Specifically, night shift work has been identified as a significant risk factor for breast cancer in industrialized countries. Several mechanisms have been proposed by which shift work-induced circadian disruptions promote cancer. In this review, we examine the importance of the brain-body link through which circadian disruptions contribute to endocrine-dependent diseases, including breast carcinogenesis, by negatively impacting neuroendocrine and neuroimmune cells, and we consider preventive measures directed at maximizing circadian health.

Urinary melatonin concentration and the risk of breast cancer in Nurses' Health Study II

Experimental and epidemiologic data support a protective role for melatonin in breast cancer etiology, yet studies in premenopausal women are scarce. In a case-control study nested within the Nurses' Health Study II cohort, we measured the concentration of melatonin's major urinary metabolite, 6-sulfatoxymelatonin (aMT6s), in urine samples collected between 1996 and 1999 among 600 breast cancer cases and 786 matched controls. Cases were predominantly premenopausal women who were diagnosed with incident breast cancer after urine collection and before June 1, 2007. Using multivariable conditional logistic regression, we computed odds ratios and 95% confidence intervals. Melatonin levels were not significantly associated with total breast cancer risk (for the fourth (top) quartile (Q4) of aMT6s vs. the first (bottom) quartile (Q1), odds ratio (OR) = 0.91, 95% confidence interval (CI): 0.64, 1.28; Ptrend = 0.38) or risk of invasive or in situ breast cancer. Findings did not vary by body mass index, smoking status, menopausal status, or time between urine collection and diagnosis (all Pinteraction values ≥ 0.12). For example, the odds ratio for total breast cancer among women with ≤5 years between urine collection and diagnosis was 0.74 (Q4 vs. Q1; 95% CI: 0.45, 1.20; Ptrend = 0.09), and it was 1.20 (Q4 vs. Q1; 95% CI: 0.72, 1.98; Ptrend = 0.70) for women with >5 years. Our data do not support an overall association between urinary melatonin levels and breast cancer risk.

The circadian rhythm in adult attention-deficit/hyperactivity disorder: current state of affairs

Adults with ADHD often have sleep problems that are caused by a delay of their internal circadian rhythm system. Such individuals are often typified as 'evening' or 'night' persons. This review focuses on the link between ADHD symptoms and the evening typology through multiple pathways. Etiology of the internal circadian rhythm system, the genetic basis for evening typology, overlap between ADHD symptoms and evening preference and risk factors for various chronic health conditions, including metabolic syndrome and cancer, are discussed. The treatment perspectives to reset the delayed rhythm in adults with ADHD involve psychoeducation on sleep hygiene, melatonin in the afternoon or evening and bright light therapy in the morning.

Urinary levels of melatonin and risk of postmenopausal breast cancer: women's health initiative observational cohort

BACKGROUND

Results from prospective studies on the association between urinary levels of melatonin and risk of postmenopausal breast cancer have been mixed. Several although not all studies have found lower urinary levels of melatonin in women who developed breast cancer compared with cancer-free women.

METHODS

We examined the association between urinary levels of melatonin and breast cancer risk in postmenopausal women in a case-control study nested in the Women's Health Initiative Observational Cohort. Levels of 6-sulfatoxymelatonin were measured in first morning voids from 258 women who later developed breast cancer and from 515 matched controls. Multivariable conditional logistic regression was used to calculate ORs and 95% confidence intervals (CI).

RESULTS

Fully adjusted risk estimates of breast cancer, relative to the lowest quartile level of creatinine-adjusted melatonin, were 1.07 (95% CI, 0.67-1.71), 1.26 (95% CI, 0.79-2.01), and 1.25 (95% CI, 0.78-2.02) for women in the second, third, and highest quartile (Ptrend = 0.27). Comparable results for cases diagnosed less than four years after urinary collection and matched controls were 1.0, 1.25 (95% CI, 0.51-3.06), 1.85 (95% CI, 0.75-4.57), and 1.94 (95% CI, 0.75-5.03; Ptrend = 0.11). Melatonin levels and breast cancer were not associated in cases diagnosed four or more years after urinary collection and matched controls (Ptrend = 0.89).

CONCLUSIONS

We found no evidence that higher urinary levels of melatonin are inversely associated with breast cancer risk in postmenopausal women.

IMPACT

Accumulating discrepancies in results across studies warrant further exploration.

First-morning urinary melatonin and breast cancer risk in the Guernsey Study

It has been hypothesized that suppressed nocturnal melatonin production is associated with an increased risk of breast cancer, but results from several small prospective studies of the association have been inconclusive. We examined the association between nocturnal melatonin and breast cancer risk in a case-control study nested within the Guernsey III Study, a British prospective cohort study (1977-2009). Concentrations of 6-sulfatoxymelatonin were measured in prediagnostic first-morning urine samples from 251 breast cancer cases and 727 matched controls. Conditional logistic regression models were used to calculate odds ratios for breast cancer in relation to 6-sulfatoxymelatonin level. No significant association was found between 6-sulfatoxymelatonin level and breast cancer risk, either overall (for highest third vs. lowest, multivariable-adjusted odds ratio = 0.90, 95% confidence interval: 0.61, 1.33) or by menopausal status. However, in a meta-analysis of all published prospective data, including 1,113 cases from 5 studies, higher 6-sulfatoxymelatonin levels were associated with lower breast cancer risk (for highest fourth vs. lowest, odds ratio = 0.81, 95% confidence interval: 0.66, 0.99). In summary, we found no evidence that 6-sulfatoxymelatonin level in a first-morning urine sample was associated with breast cancer risk among British women. However, overall the published data suggest a modest inverse association between melatonin levels and breast cancer risk. Further data are needed to confirm this association.

A cross-sectional analysis of light at night, neighborhood sociodemographics and urinary 6-sulfatoxymelatonin concentrations: implications for the conduct of health studies

BACKGROUND

There is accumulating evidence that circadian disruption, mediated by alterations in melatonin levels, may play an etiologic role in a wide variety of diseases. The degree to which light-at-night (LAN) and other factors can alter melatonin levels is not well-documented. Our primary objective was to evaluate the degree to which estimates of outdoor environmental LAN predict 6-sulftoxymelatonin (aMT6s), the primary urinary metabolite of melatonin. We also evaluated other potential behavioral, sociodemographic, and anthropomorphic predictors of aMT6s.

METHODS

Study participants consisted of 303 members of the California Teachers Study who provided a 24-hour urine specimen and completed a self-administered questionnaire in 2000. Urinary aMT6s was measured using the Bühlmann ELISA. Outdoor LAN levels were estimated from satellite imagery data obtained from the U.S. Defense Meteorological Satellite Program's (DMSP) Operational Linescan System and assigned to study participants' geocoded residential address. Information on other potential predictors of aMT6s was derived from self-administered surveys. Neighborhood socioeconomic status (SES) was based on U.S. Census block group data.

RESULTS

Lower aMT6s levels were significantly associated with older age, shorter nights, and residential locations in lower SES neighborhoods. Outdoor sources of LAN estimated using low-dynamic range DMSP data had insufficient variability across urban neighborhoods to evaluate. While high-dynamic range DMSP offered much better variability, it was not significantly associated with urinary aMT6s.

CONCLUSIONS

Future health studies should utilize the high-dynamic range DMSP data and should consider other potential sources of circadian disruption associated with living in lower SES neighborhoods.

Therapeutic applications of melatonin

Melatonin is a methoxyindole synthesized within the pineal gland. The hormone is secreted during the night and appears to play multiple roles within the human organism. The hormone contributes to the regulation of biological rhythms, may induce sleep, has strong antioxidant action and appears to contribute to the protection of the organism from carcinogenesis and neurodegenerative disorders. At a therapeutic level as well as in prevention, melatonin is used for the management of sleep disorders and jet lag, for the resynchronization of circadian rhythms in situations such as blindness and shift work, for its preventive action in the development of cancer, as additive therapy in cancer and as therapy for preventing the progression of Alzheimer's disease and other neurodegenerative disorders.

Associations of urinary 6-sulfatoxymelatonin with demographics, body mass, sex steroids, and lifestyle factors in preschool Japanese children

PURPOSE

We aimed to assess the associations of sex, age, body mass, sex steroid hormones, and lifestyle factors with the levels of melatonin in young children.

METHODS

This study followed a cross-sectional design and was conducted two preschools in Japan. Subjects were 235 boys and 203 girls, aged 3-6 years. Information related to demographics, body mass, and lifestyle factors was obtained from parent-administered questionnaires. The levels of 6-sulfatoxymelatonin and dehydroepiandrosterone in first-void morning urine were measured by radioimmunoassay. Urinary estrone, estradiol, testosterone, and 5-androstene-3β, 17α diol levels were measured by liquid chromatography-electrospray ionization tandem mass spectrometry.

RESULTS

The creatinine-corrected 6-sulfatoxymelatonin levels and the estimated value of 6-sulfatoxymelatonin excretion were higher in girls than in boys. After adjustments for age, the creatinine-corrected 6-sulfatoxymelatonin was negatively associated with weight and body mass index among boys and with weight and height among girls. However, the estimated value of 6-sulfatoxymelatonin excretion was not associated with any indices of body mass. No significant relationships of urinary sex steroids, light exposure at night, sleep time, sedentary lifestyles, or passive smoking with urinary 6-sulfatoxymelatonin were observed.

CONCLUSIONS

Our findings suggest that melatonin levels depend on sex and body size among young healthy children. Our results should be confirmed in future researches.

Melatonin: the smart killer: the human trophoblast as a model

Melatonin has both the ability to induce intrinsic apoptosis in tumor cells while it inhibits it in non-tumor cells. Melatonin kills tumor cells through induction of reactive oxygen species generation and activation of pro-apoptotic pathways. In contrast, melatonin promotes the survival of non-tumor cells due to its antioxidant properties and the inhibition of pro-apoptotic pathways. In primary human villous trophoblast, a known pseudo-tumorigenic tissue, melatonin promotes the survival through inhibition of the Bax/Bcl-2 pathway while in BeWo choriocarcinoma cell line melatonin induces permeabilization of the mitochondrial membrane leading to cellular death. These findings suggest that the trophoblast is a good model to study the differential effects of melatonin on the intrinsic apoptosis pathway. This review describes the differential effects of melatonin on the intrinsic apoptosis pathway in tumor and non-tumor cells and presents the trophoblast as a novel model system in which to study these effects of melatonin.

Protective effect of melatonin against chlorophyll degradation during the senescence of barley leaves

Melatonin (N-acetyl-5-methoxytryptamine) is a highly conserved molecule whose presence is not exclusive to the animal kingdom. Indeed, numerous studies have demonstrated its presence in plants, where the possible role(s) of this indoleamine is (are) under active investigation. The present work aims to further our knowledge in this respect and presents the results of a study of the effect that melatonin has on foliar senescence. Barley leaves treated with melatonin solutions clearly slowed down the senescence process, as estimated from the chlorophyll lost in leaves. This effect of melatonin was concentration dependent, with an optimal response being obtained at 1 mm melatonin, after 48 hr of incubation in darkness. The already known effects of the phytohormones, kinetin, and abscisic acid, were also assayed. Of the phytohormone and melatonin combinations assayed, 1 mm melatonin presented the best protection against senescence. The levels of endogenous melatonin in control leaves were measured by liquid chromatography with fluorescence detection and in leaves treated with different exogenous melatonin concentrations (to demonstrate the absorption capacity of leaves). The possible physiological implications of this newly revealed action of melatonin in foliar senescence are discussed.

Distribution of melatonin in different zones of lupin and barley plants at different ages in the presence and absence of light

In animals, melatonin (N-acetyl-5-methoxytryptamine) has several physiological roles, mostly related with circadian and seasonal rhythms. In 1995, it was detected in a variety of edible plants, and it is known that melatonin from plant foods is absorbed from the gastrointestinal tract and incorporated in the blood stream. This indoleamine also crosses the blood-brain barrier and the placenta, being incorporated at the subcellular level. The possibility of modulating blood melatonin levels in mammals and avians through the ingestion of plant foodstuffs seems to be an interesting prospect. However, data concerning the melatonin content of edible plants are scarce and have not been contrasted. Obtained with very different analytical techniques, in some cases inappropriate, the quantitative data show a high degree of variation. Possibly for the first time in plants, we have used liquid chromatography with time-of-flight/mass spectrometry to identify melatonin. This sophisticated technique, combined with the more commonly used liquid chromatography with fluorescence detection for melatonin quantification, has permitted us to describe the distribution of this compound in different organs and zones in plants. Also, changes in melatonin levels with age and the possible influence of a light/dark photoperiod or constant darkness on its levels are studied. The proposal, applied here to lupin (Lupinus albus L.) and barley (Hordeum vulgare L.), may also serve as a model for application to other plant foodstuffs.

Therapeutic potential of melatonin agonists

Melatonin, a hormone secreted by the pineal gland, has been successfully employed to improve sleep in both normal patients and insomniacs, and for the treatment of circadian rhythm sleep disorders. Melatonergic MT₁ and MT₂ receptors exist in high concentrations in the suprachiasmatic nucleus of the hypothalamus and have been shown to be instrumental for the sleep-promoting and circadian rhythm-regulating effects of melatonin. A lack of consistency among reports on the therapeutic efficacy of melatonin has been attributed to differences in melatonin's bioavailability and the short half-life of the hormone. In view of the need for longer acting melatonergic agonists that improve sleep efficiency without causing drug abuse or dependency, ramelteon (Rozerem™, Takeda) was developed. Ramelteon, which acts via MT₁/MT₂ melatonergic agonism, has been found clinically effective for improving total sleep time and sleep efficiency in insomniacs. Agomelatine (Valdoxan™, Servier) is another MT₁/MT₂ melatonergic agonist that also displays antagonist activity at 5-HT_2C serotonin receptors. Agomelatine has been found effective in treating depression and sleep disorders in patients with major depressive disorder. A slow-release preparation of melatonin (Circadin™, Neurim) has been shown to be effective in treating sleep disorders in the elderly population.