Association between urinary 6-sulfatoxymelatonin excretion and arterial stiffness in the general elderly population: the HEIJO-KYO cohort

Effects of melatonin on blood pressure, arterial stiffness and quality of life in postmenopausal women: A randomized controlled trial

OBJECTIVES

Studies suggest that melatonin may promote cardiovascular protection. Previous trials have primarily been performed on co-morbid patients. Little information exist on the effect in postmenopausal women with general good health.

DESIGN, PARTICIPANTS AND INTERVENTION

In a double-blinded placebo-controlled study, we randomized 41 postmenopausal women to either 10 mg melatonin per day or placebo for 3 months.

OUTCOME MEASURES

Outcomes of the trial was changes in blood pressure, pulse wave velocity (PWV), and quality of sleep evaluated by Pittsburgh Sleep Quality Index (PSQI).

RESULTS

Thirty-nine women completed the study. Mean age was 63 years (range 55-75 years). Over the 3 months of the trial, PWV did not differ between groups: Placebo 1.1% (IQR -2.1;9.9) vs. melatonin 0.0% (IQR-9.8;4.1), p = 0.43). The were no significant differences in blood pressure bewteen melatonin and placebo group. Both groups had a pour quality of sleep at baseline (placebo: PSQI 6.0 (IQR 3.3; 8.8) vs. melatonin PSQI 6.0 (IQR 3.0; 10.0), p = 0.94), which did not change in response to treatment.

CONCLUSION

In healthy postmenopausal women, supplementation with 10 mg melatonin was well-tolerated, but we did not observe any significant improvements in pulse wave velocity, blood pressure or quality of sleep compared with placebo.

Effects of a violet-excitation light-emitting diode on melatonin secretion and sleepiness: preliminary findings from a randomized controlled trial

STUDY OBJECTIVES

A new type of lighting using violet-excitation light-emitting diodes (LEDs) with an action spectrum centered at approximately 405 nm was developed. Although violet-excitation LEDs can reduce melatonin suppression compared with blue-excitation LEDs, no studies have compared the effects of violet-excitation LEDs with those of blue-excitation LEDs on melatonin suppression. This study was designed to compare the effects of violet-excitation LEDs with those of blue-excitation LEDs on melatonin suppression, psychomotor vigilance, and sleepiness.

METHODS

Sixteen healthy Japanese males aged 20-39 years were exposed to violet- and blue-excitation LEDs for 3 hours in a crossover randomized manner. The primary outcome was changes in salivary melatonin levels compared with the baseline levels. The secondary outcomes were changes in psychomotor vigilance and the Karolinska Sleepiness Scale. Melatonin suppression was calculated from the difference in the area under the curves between the baseline and intervention.

RESULTS

Of the 16 participants, 15 completed the measurements. The baseline characteristics did not differ significantly between the 2 groups. After adjusting for age, a difference of 16.28 pg/mL in mean melatonin suppression was observed between the violet- and blue-excitation LED groups (-2.15 pg/mL vs -18.43 pg/mL; P = .006). The overall melatonin suppression by violet-excitation LEDs was 48.6% smaller than that by blue-excitation LEDs. No significant differences in psychomotor vigilance and sleepiness were observed between the 2 groups.

CONCLUSIONS

Melatonin suppression in healthy Japanese males exposed to violet-excitation LEDs was significantly smaller than that in those exposed to blue-excitation LEDs. Our preliminary findings indicate that violet-excitation LEDs may have the potential to reduce the magnitude of blue-excitation LED-induced melatonin suppression.

CITATION

Mitsui K, Saeki K, Sun M, Yamagami Y, Tai Y, Obayashi K. Effects of a violet-excitation light-emitting diode on melatonin secretion and sleepiness: preliminary findings from a randomized controlled trial. J Clin Sleep Med. 2024;20(1):101-109.

Physiological and pharmacological perspectives of melatonin

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

Melatonin Supplementation for Six Weeks Had No Effect on Arterial Stiffness and Mitochondrial DNA in Women Aged 55 Years and Older with Insomnia: A Double-Blind Randomized Controlled Study

Melatonin is a hormone produced in the pineal gland that controls sleep and circadian rhythm. Some studies have reported antioxidant and anti-inflammatory effects of melatonin that could benefit cardiometabolic function; however, there is a lack of evidence to support these assertions. The aim of this study was to investigate whether melatonin has beneficial effects on arterial stiffness and mitochondrial deoxyribonucleic acid (DNA) in humans. Methods: This study was designed as a double-blind randomized controlled study. Thirty-eight healthy women aged 55 years and older were enrolled. All had insomnia (Pittsburgh Sleep Quality Index (PSQI) ≥ 5), not treated with any medications, for at least three months before enrollment. Subjects were divided into a melatonin and a placebo group according to melatonin supplementation. The melatonin group took 2 mg melatonin every night for six weeks. The cardio–ankle vascular index (CAVI) was used as an indicator of arterial stiffness. After six weeks, CAVI, mitochondrial DNA (mtDNA) copy number in white blood cells (WBCs), and other metabolic indices, such as homeostasis model assessment of insulin resistance (HOMA-IR), were checked. Results: Sleep quality index using PSQI was improved in the melatonin group from a score of 11 to 8 (p = 0.01), but did not change significantly in the control group. However, there was no significant intergroup difference in PSQI. Systolic blood pressure (SBP) decreased in the melatonin group from 135 to 128 mmHg (p = 0.015), while remaining stable in the placebo group. Right CAVI, mitochondrial DNA copy number, and HOMA-IR were not altered in either group. There were no intergroup differences in CAVI, mtDNA, HOMA-IR, or SBP between baseline and week six. Conclusions: We found no evidence that melatonin supplementation improved cardiometabolic parameters like arterial stiffness, mtDNA, or insulin resistance compared to the placebo between baseline and week six. Sleep quality was improved in the melatonin group. Further research, including longer-term studies with higher doses of melatonin, is warranted.

Decreased melatonin secretion in patients with glaucoma: Quantitative association with glaucoma severity in the LIGHT study

Glaucoma may be associated with circadian disruption due to its association with a loss of intrinsically photosensitive retinal ganglion cells. Clinical evidence demonstrating an association between glaucoma and circadian disruption is limited, and no large-scale studies have been performed. The purpose of this cross-sectional study was to determine whether the presence and severity of glaucoma is correlated with the urinary 6-sulfatoxymelatonin levels as a circadian rhythm parameter. We measured the level of urinary 6-sulfatoxymelatonin excretion (UME) in 118 glaucoma patients and 395 control participants without glaucoma. The UME in the glaucoma group was significantly lower than that of the control group without glaucoma (3.05 and 3.24 log ng/mg creatinine, respectively; P = .010). Next, we examined association of the severity of glaucoma and melatonin levels. In stratification analysis of the glaucoma groups, multivariable linear regression analyses adjusted for potential confounders indicated significantly lower UME by 0.30 log ng/mg creatinine in patients with functional severe glaucoma (visual field mean deviation ≤ -6 dB) compared with mild glaucoma (mean deviation > -6 dB; P = .040) and lower UME by 0.05 log ng/mg creatinine with each 10 μm thinning of the circumpapillary retinal nerve fiber layer thickness as the index of structural severity of glaucoma (P = .011). In conclusion, significant association between glaucoma and lower urinary 6-sulfatoxymelatonin was found. In addition, patients with functional and structural severe glaucoma were significantly associated with lower urinary 6-sulfatoxymelatonin levels. Our results indicate the possibility of a circadian disruption in patients with glaucoma.

Diabetes and atherothrombosis: The circadian rhythm and role of melatonin in vascular protection

Obesity-related euglycaemic insulin resistance clusters with cardiometabolic risk factors, contributing to the development of both type 2 diabetes and cardiovascular disease. An increased thrombotic tendency in diabetes stems from platelet hyperactivity, enhanced activity of prothrombotic coagulation factors and impaired fibrinolysis. Furthermore, a low-grade inflammatory response and increased oxidative stress accelerate the atherosclerotic process and, together with an enhanced thrombotic environment, result in premature and more severe cardiovascular disease. The disruption of circadian cycles in man secondary to chronic obesity and loss of circadian cues is implicated in the increased risk of developing diabetes and cardiovascular disease. Levels of melatonin, the endogenous synchronizer of circadian rhythm, are reduced in individuals with vascular disease and those with deranged glucose metabolism. The anti-inflammatory, antihypertensive, antioxidative and antithrombotic activities of melatonin make it a potential therapeutic agent to reduce the risk of vascular occlusive disease in diabetes. The mechanisms behind melatonin-associated reduction in procoagulant response are not fully known. Current evidence suggests that melatonin inhibits platelet aggregation and might affect the coagulation cascade, altering fibrin clot structure and/or resistance to fibrinolysis. Large-scale clinical trials are warranted to investigate the effects of modulating the circadian clock on insulin resistance, glycaemia and cardiovascular outcome.

Pineal Calcification, Melatonin Production, Aging, Associated Health Consequences and Rejuvenation of the Pineal Gland

The pineal gland is a unique organ that synthesizes melatonin as the signaling molecule of natural photoperiodic environment and as a potent neuronal protective antioxidant. An intact and functional pineal gland is necessary for preserving optimal human health. Unfortunately, this gland has the highest calcification rate among all organs and tissues of the human body. Pineal calcification jeopardizes melatonin's synthetic capacity and is associated with a variety of neuronal diseases. In the current review, we summarized the potential mechanisms of how this process may occur under pathological conditions or during aging. We hypothesized that pineal calcification is an active process and resembles in some respects of bone formation. The mesenchymal stem cells and melatonin participate in this process. Finally, we suggest that preservation of pineal health can be achieved by retarding its premature calcification or even rejuvenating the calcified gland.

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

CONTEXT

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

OBJECTIVE

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

DESIGN AND PARTICIPANTS

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

MEASURES

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

RESULTS

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

CONCLUSIONS

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

How does healthy aging impact on the circadian clock?

Circadian rhythms are recurring patterns in a host of physiological and other parameters that recur with periods of near 24 h. These rhythms reflect the temporal organization of an organism's homeostatic control systems and as such are key processes in ensuring optimal physiological performance. Dysfunction of circadian processes is linked with adverse health conditions. In this review we highlight the evidence that normal, healthy aging is associated with changes in the circadian system; we examine the molecular mechanisms through which such changes may arise, discuss whether more robust circadian function is a predictor of longevity and highlight the role of circadian rhythms in age-related diseases. Overall, the literature shows that aging is associated with marked changes in circadian processes, both at the behavioral and molecular levels, and the molecular mechanisms through which such changes arise remain to be elucidated, but may involve inflammatory process, redox homeostasis and epigenetic modifications. Understanding the nature of age-related circadian dysfunction will allow for the design of chronotherapeutic intervention strategies to attenuate circadian dysfunction and thus improve health and quality of life.

Higher melatonin secretion is associated with lower leukocyte and platelet counts in the general elderly population: the HEIJO-KYO cohort

Circulating white blood cell (WBC) and platelet (PLT) counts are widely available and inexpensive cellular biomarkers of systemic inflammation and have been associated with a risk of cardiovascular disease, cancer, and mortality. Melatonin may reduce systemic inflammation through its direct and indirect antioxidative effect; however, the associations of melatonin secretion with systemic inflammation remain unclear. In this cross-sectional study on 1088 elderly individuals (mean age, 71.8 years), we measured overnight urinary 6-sulfatoxymelatonin excretion (UME) and WBC and PLT counts as indices of melatonin secretion and systemic inflammation, respectively. UME was naturally log-transformed for linear regression models because of skewed distribution (median, 6.8 μg; interquartile range, 4.1-10.6 μg). Univariate models revealed that higher log-transformed UME levels were significantly associated with lower WBC and PLT counts (P = 0.046 and 0.018). After adjusting for potential confounding factors significantly associated with WBC or PLT counts, higher log-transformed UME levels were significantly associated with lower WBC and PLT counts (WBC: β, -0.143; 95% confidence interval, -0.267 to -0.020; P = 0.023; PLT: β, -6.786; 95% confidence interval, -12.047 to -1.525; P = 0.012). Furthermore, the adjusted mean differences in WBC and PLT counts between the lowest and highest UME tertile groups were 0.225 × 10(9) /L and 9.480 × 10(9) /L, respectively. In conclusion, melatonin secretion was significantly and inversely associated with WBC and PLT counts in the general elderly population. The associations were independent of several major causes of systemic inflammation, including aging, obesity, smoking, hypertension, diabetes, and physical inactivity.