A new concept for melatonin deficit: on pineal calcification and melatonin excretion

Intracranial calcifications associated with factors related and unrelated to atherosclerosis in older people: A community dwelling cohort study

The cause of intracranial calcification is not fully understood. The aim of the current study was to identify factors associated with intracranial calcification and to determine whether these factors differ in calcification of different sites. A total of 404 community-dwelling people aged 65 or older were included in the study. All subjects underwent brain computed tomography (CT), blood tests, and a Mini-Mental State Examination (MMSE). Intracranial calcifications were scored using CT. Stepwise regression analysis was performed to examine factors associated with intracranial calcification, with each calcification score used as a dependent variable. Independent variables included age, gender, hemoglobin A1c (HbA1c), dyslipidemia, estimated glomerular filtration rate (eGFR), blood pressure, body mass index (BMI), smoking, serum iron, ferritin, and intact parathyroid hormone (PTH). Stepwise regression analysis detected male gender as a predictor of pineal gland calcification and intact PTH as a predictor of basal ganglia calcification. Age and lifestyle diseases were identified as predictors of calcification of the falx cerebri, internal carotid arteries, and vertebral arteries. These results indicate that the mechanisms of calcifications of the pineal gland and basal ganglia might differ from that of artery calcification, and that causes of intracranial calcification might be classified using factors that are and are not related to atherosclerosis.

Melatonin suppression by light involves different retinal photoreceptors in young and older adults

Age-related sleep and circadian rhythm disturbances may be due to altered nonvisual photoreception. Here, we investigated the temporal dynamics of light-induced melatonin suppression in young and older individuals. In a within-subject design study, young and older participants were exposed for 60 min (0030-0130 at night) to nine narrow-band lights (range: 420-620 nm). Plasma melatonin suppression was calculated at 15, 30, 45, and 60 min time intervals. Individual spectral sensitivity of melatonin suppression and photoreceptor contribution were predicted for each interval and age group. In young participants, melanopsin solely drove melatonin suppression at all time intervals, with a peak sensitivity at 485.3 nm established only after 15 min of light exposure. Conversely, in older participants, spectral light-driven melatonin suppression was best explained by a more complex model combining melanopsin, S-cone, and M-cone functions, with a stable peak (~500 nm) at 30, 45, and 60 min of light exposure. Aging is associated with a distinct photoreceptor contribution to melatonin suppression by light. While in young adults melanopsin-only photoreception is a reliable predictor of melatonin suppression, in older individuals this process is jointly driven by melanopsin, S-cone, and M-cone functions. These findings offer new prospects for customizing light therapy for older individuals.

Comparative study of calcification in human choroid plexus, pineal gland, and habenula

Choroid plexus, pineal gland, and habenula tend to accumulate physiologic calcifications (concrements) over a lifetime. However, until now the composition and causes of the intracranial calcifications remain unclear. The detailed analysis of concrements has been done by us using X-ray diffraction analysis (XRD), X-ray diffraction topography (XRDT), micro-CT, X-ray phase-contrast tomography (XPCT), as well as histology and immunohistochemistry (IHC). By combining physical (XRD) and biochemical (IHC) methods, we identified inorganic (hydroxyapatite) and organic (vimentin) components of the concrements. Via XPCT, XRDT, histological, and IHC methods, we assessed the structure of concrements within their appropriate tissue environment in both two and three dimensions. The study found that hydroxyapatite was a major component of all calcified depositions. It should be noted, however, that the concrements displayed distinctive characteristics corresponding to each specific structure of the brain. As a result, our study provides a basis for assessing the pathological and physiological changes that occur in brain structure containing calcifications.

Human Pineal Gland Involutionary Process: New Findings

In this work, we report preliminary results about the involution of the human pineal gland involution. The detailed analysis of pineal structure was done on autopsy material of 77 persons in age 27-96 using x-ray phase-contrast tomography, histology, and immunohistochemistry. Our study suggests that the pineal gland alteration in older adults may be more profound than has been reported to date. We identified and described a new form of pineal gland involution that eventually led to the total degradation of the pineal gland. To our knowledge, this study is the first to report on the complete replacement of pineal gland parenchyma with connective tissue in older adults.

Cross-sectional analysis of potential risk factors of the pineal gland calcification

The Pineal gland (PG) is the site of production of melatonin as an important central hormone in the body. It is not known yet whether PG calcification (PGC) is an age-associated physiological process or a pathologic condition caused by lifestyle-factors and metabolic-dysregulations.Here, we performed a cross-sectional analysis on 586 patients referred to have Computed Tomographic (CT) scans (above 15 years old), in the Ali Ebne Abi Taleb hospital radiology center in 2017-2018. Based on the CT-scans of the brain, the presence of PGC was recorded and a score of scale 0 to 6 (PGC_score) was calculated for its intensity based on the volume and the Hounsfield units of the calcified pineal. Logistic and ordered logistic regression tests were employed to determine potential risk factor of PGC and higher PGC_score, respectively, testing the factors age, sex, history of cardiovascular and metabolic diseases, smoking and opioid use. We found male sex (OR: 2.30 (95% CI:1.39-3.82) and smoking cigarettes (OR: 4.47 (95% CI:1.01-19.78)) as the main potential risk factors for the pineal gland calcification. For PGC_score, we found age to be dose-dependently associated with PGC_score only in patients aged below 63 (p-trend < 0.001). Stratifying for age, in patients < 63 years old, we found age, male sex (positive association) and dyslipidemia (negative association) as the main significantly associated factors of PGC_score. On the contrary, in patients aged >  = 63, cigarette smoking was the only significantly associated factor of higher PGC_score.In conclusion, our results indicate that at ages below 63, age, male sex and blood lipid are the main associated factors of higher PGC, but at ages above that, the lifestyle factor smoking is significantly associated with higher pineal gland calcification.

Association between Water Fluoride Levels and Low Birth Weight: National Health and Nutrition Examination Survey (NHANES) 2013-2016

Background: Excessive fluoride consumption affects reproductive and child health. We examined the association between levels of fluoride in drinking water and birth weight, in the National Health and Nutrition Examination Survey 2013−2016, after adjusting for known risk factors Low Birth Weight (LBW) including age, smoking, and socio-demographic variables including education, food security, health care access, and health status. Methods: The study included 7147 and 6858 women with complete birth weight and water fluoride data, respectively. Linear regression models evaluated the association between water fluoride and birth weight across racial/ethnic groups. The odds of delivering an LBW infant (<2500 g) compared to an infant weighing ≥ 2500 g, as well as the odds of delivering a Very Low Birth Weight (VLBW, <1500 g) infant compared to an LBW infant were explored in separate logistic regression models. Results: Women with LBW infants were exposed to significantly higher levels of water fluoride compared to those with normal birth weight infants. Our findings suggest a significant association between excess water fluoride exposure (>0.7 ppm) and LBW weight in Hispanic women, independent of established LBW risk factors. In logistic regression models, Hispanic women exposed to increased levels of water fluoride were 1.5 times more likely to give birth to an LBW infant and 3.5 more likely to give birth to a VLBW infant. Conclusion: Taken together, these findings can inform public health education strategies that highlight water fluoride as a potential risk factor during pregnancy in Hispanic women. More research is needed to confirm these findings.

A genome-wide association study for melatonin secretion

Melatonin exerts a wide range of effects among various tissues and organs. However, there is currently no study to investigate the genetic determinants of melatonin secretion. Here, we conducted a genome-wide association study (GWAS) for melatonin secretion using morning urine 6-hydroxymelatonin sulfate-to-creatinine ratio (UMCR). We initially enrolled 5000 participants from Taiwan Biobank in this study. After excluding individuals that did not have their urine collected in the morning, those who had history of neurological or psychiatric disorder, and those who failed to pass quality control, association of single nucleotide polymorphisms with log-transformed UMCR adjusted for age, sex and principal components of ancestry were analyzed. A second model additionally adjusted for estimated glomerular filtration rate (eGFR). A total of 2373 participants underwent the genome-wide analysis. Five candidate loci associated with log UMCR (P value ranging from 6.83 × 10−7 to 3.44 × 10−6) encompassing ZFHX3, GALNT15, GALNT13, LDLRAD3 and intergenic between SEPP1 and FLJ32255 were identified. Similar results were yielded with further adjustment for eGFR. Interestingly, the identified genes are associated with circadian behavior, neuronal differentiation, motor disorders, anxiety, and neurodegenerative diseases. We conducted the first GWAS for melatonin secretion and identified five candidate genetic loci associated with melatonin level. Replication and functional studies are needed in the future.

Running on Empty: Of Hypopinealism and Human Seasonality

The pineal hormone melatonin is the natural transducer of the environmental light-dark signal to the body. Although the responsiveness to photoperiod is well-conserved in humans, only about 25 percent of the human population experiences seasonal changes in behavior. As a consequence, humans seem to have adapted-at least partly-to the seasonal changes in day length. The aim of the study was to demonstrate that the individual melatonin deficit marker DOC (degree of pineal calcification) is related to variation of seasonal phenomena in humans. Out of 3,011 patients in which cranial computer tomography (cCT) was performed for diagnostic reasons, 97 consecutive "healthy" subjects (43 female, 54 male; age 18-68 yrs, mean ± SD: 35.0 ± 13.1) were included. Exclusion criteria were pathological finding in cCT, acute/chronic illness including alcohol/drug abuse, shift work, and medication, which are known to influence melatonin excretion. The degree of pineal calcification (DOC) was semiquantitatively determined using the previously validated method. The Seasonal Pattern Assessment Questionnaire (SPAQ) was performed in a telephone interview. Twenty-six subjects fulfilled the criteria for seasonal affective disorder (SAD) or subsyndromal (S) SAD. Seasonality was more pronounced in women than in men (SPAQ seasonality score: 7.8 ± 4.0 vs. 4.9 ± 4.5; p = 0.001) and negatively and significantly associated with age (r = -0.178; p = 0.04). The subjective sleep length significantly varied between seasons (one-way repeated measures ANOVA: F = 45.75; p < 0.0001), with sleep during winter being 53 min (±70 min) longer than during summer. Controlling for age, the total seasonality score was negatively and significantly associated with DOC (r₉₄ = -0.214; p = 0.036). Data confirm earlier studies with respect to distribution of seasonality with sex and age. The survival of seasonality in the sleep length of people living in an urban environment underlines functionality of the circadian timing system in modern societies. Moreover, data confirm for the first time that diminished experience of seasonality in behavior is associated with a reduced individual capacity to produce melatonin.

Melatonin and Phytomelatonin: Chemistry, Biosynthesis, Metabolism, Distribution and Bioactivity in Plants and Animals-An Overview

Melatonin is a ubiquitous indolamine, largely investigated for its key role in the regulation of several physiological processes in both animals and plants. In the last century, it was reported that this molecule may be produced in high concentrations by several species belonging to the plant kingdom and stored in specialized tissues. In this review, the main information related to the chemistry of melatonin and its metabolism has been summarized. Furthermore, the biosynthetic pathway characteristics of animal and plant cells have been compared, and the main differences between the two systems highlighted. Additionally, in order to investigate the distribution of this indolamine in the plant kingdom, distribution cluster analysis was performed using a database composed by 47 previously published articles reporting the content of melatonin in different plant families, species and tissues. Finally, the potential pharmacological and biostimulant benefits derived from the administration of exogenous melatonin on animals or plants via the intake of dietary supplements or the application of biostimulant formulation have been largely discussed.

[The effect of long-term beta-blockers on melatonin secretion, sleep quality, and vascular brain damage]

Circadian rhythm of pineal melatonin production is paced by the thalamus suprachiasmatic nucleus (SCN) depending on the lighting conditions via signal transduction to pinealocytes beta-receptors. Melatonin is a natural regulator of many physiological processes, and the decrease of its synthesis leads to various diseases, in particular, insomnia and metabolic disorders. It is known that administration of beta-blockers reduces melatonin production, but the data showing clinical significance of melatonin reduction associated with beta-blockers administration are still contradictory.

OBJECTIVE

The influence of long-term administration of beta-blockers to melatonin synthesis, sleep quality and vascular brain damage.

MATERIALS AND METHODS

The main study group included 114 patients, aged 47-83, with cardiovascular diseases, who were under a complex therapy with long-term administration of beta-blockers. The comparison group included 110 patients with cardiovascular diseases, similar in age and sex, who did not receive beta-blockers in their complex therapy. The circadian dynamics of melatonin synthesis was observed by excretion of 6-sulfatoxymelatonin (6-SM), the major metabolite of melatonin, in three urinary samples (day, evening, night). All the patients underwent night polysomnography to assess the severity of sleep disorders. The severity of vascular brain damage was assessed using magnetic resonance imaging.

RESULTS

The analyses showed large variability in individual values of 6-SM circadian excretion of patients with cardiovascular diseases (from 0.9 to 133 μg/24h with a mid-point 16.8 μg/24h). A considerable decrease of 6-SM circadian excretion is detected in the group of patients taking beta-blockers comparing to those not Me [q 25; q 75]: 12.8 [6.2; 21.1] and 24.0 [12.5; 41.5] μg/24h, respectively (p<0.001), with no differences in sleep values and severity of vascular brain damage. Comparing subgroups of patients with 6-SM circadian excretion lower and higher than 16.8 μg/24h showed a significant increase of sleep latency, decrease of rapid eye movement sleep (REM sleep), increasing number of gliosis foci in white matter of the brain with higher values of leptin, leptin/adiponectin ratio and glycohemoglobin in the group of patients with 6-SM circadian excretion ≤16.8 μg/24h.

CONCLUSION

A low level of endogenous melatonin is a risk factor for development of sleep structure and quality disorders, vascular white matter brain damages with a higher risk for metabolic disorders. Long-term beta-blockers administration decrease endogenous melatonin synthesis to 50% increasing the risk for insomnia and vascular brain damage, mostly in patients with lower initial level of 6-SM circadian excretion.: melatonin, 6-sulfatoxymelatonin, beta-blockers, insomnia, vascular white matter brain damage, leptin, adiponectin.

Sleep in Normal Aging, Homeostatic and Circadian Regulation and Vulnerability to Sleep Deprivation

In the context of geriatric research, a growing body of evidence links normal age-related changes in sleep with many adverse health outcomes, especially a decline in cognition in older adults. The most important sleep alterations that continue to worsen after 60 years involve sleep timing, (especially early wake time, phase advance), sleep maintenance (continuity of sleep interrupted by numerous awakenings) and reduced amount of sigma activity (during non-rapid eye movement (NREM) sleep) associated with modifications of sleep spindle characteristics (density, amplitude, frequency) and spindle-Slow Wave coupling. After 60 years, there is a very clear gender-dependent deterioration in sleep. Even if there are degradations of sleep after 60 years, daytime wake level and especially daytime sleepiness is not modified with age. On the other hand, under sleep deprivation condition, older adults show smaller cognitive impairments than younger adults, suggesting an age-related lower vulnerability to extended wakefulness. These sleep and cognitive age-related modifications would be due to a reduced homeostatic drive and consequently a reduced sleep need, an attenuation of circadian drive (reduction of sleep forbidden zone in late afternoon and wake forbidden zone in early morning), a modification of the interaction of the circadian and homeostatic processes and/or an alteration of subcortical structures involved in generation of circadian and homeostatic drive, or connections to the cerebral cortex with age. The modifications and interactions of these two processes with age are still uncertain, and still require further investigation. The understanding of the respective contribution of circadian and homeostatic processes in the regulation of neurobehavioral function with aging present a challenge for improving health, management of cognitive decline and potential early chronobiological or sleep-wake interventions.

Modulation of aqueous humor melatonin levels by yellow-filter and its protective effect on lens

Melatonin is mainly secreted by the pineal gland, and it is also produced by various ocular structures such as the lens. It has been recently demonstrated that melatonin ocular synthesis can be induced by blocking the blue component of white light by means of filters. Melatonin exhibits antioxidant properties that can be useful to face light-induced oxidative stress as well as oxidative events associated to ocular pathologies like cataracts. Moreover, as oxidative stress is a main event in cataract development, changes in melatonin levels could happen and be relevant in the progression of this pathology, a subject that remains uncertain. The goal of this work was to analyze the ability of a short wavelength light blocking (yellow) filter to modulate endogenous melatonin concentration and the antioxidant and cytoprotective actions induced by yellow filter's use in lens. Furthermore, we evaluated the potential changes in aqueous humor melatonin concentration from patients with cataracts. In human lens epithelial cells, white light-emitting diode (LED) light challenge reduced melatonin secretion, protein levels of the enzymes involved in melatonin synthesis (hydroxyindole-O-methyltransferase and unphosphorylated and phosphorylated forms of arylalkylamine N-acetyltransferase) and cell viability whereas increased reactive oxygen species production. Yellow filter exposure precluded melatonin secretion reduction and protected cells from oxidative damage. Consistent with cataract patient's results, significantly lower levels of melatonin were observed in aqueous humor of alloxan-induced diabetic cataract rabbits as compared to those of control rabbits. In contrast, aqueous humor melatonin levels of diabetic cataract animals maintaining in cages covered with a yellow filter resembled control values. This recovery seems to be mediated by the induction of melatonin biosynthetic enzymes protein expression. Yellow filter also preserved Nrf2 lens protein expression and superoxide dismutase protein levels and activity in diabetic animals. Modulation of endogenous ocular melatonin concentration using blocking filters might be a promising approach to prevent premature lens opacification.

Exploratory assessment of pineal gland volume, composition, and urinary 6-sulfatoxymelatonin levels on prostate cancer risk

INTRODUCTION

Melatonin levels are partially driven by the parenchyma volume of the pineal gland. Low urinary levels of 6-sulfatoxymelatonin have been associated with increased risk of advanced prostate cancer, but the relationship between pineal gland volume and composition and prostate cancer risk has not been examined.

MATERIALS AND METHODS

We utilized data from 864 men from the AGES-Reykjavik Study with complete pineal gland volumes and urinary 6-sulfatoxymelatonin measurements. Pineal parenchyma, calcification, and cyst volumes were calculated from brain magnetic resonance imaging. Levels of 6-sulfatoxymelatonin were assayed from prediagnostic urine samples. We calculated Pearson correlation coefficients between parenchyma volume and urinary 6-sulfatoxymelatonin levels. We used Cox proportional hazards regression to calculate multivariable hazard ratios (HRs) and 95% confidence intervals (95% CIs) comparing prostate cancer risk across parenchyma volume tertiles and across categories factoring in parenchyma volume, gland composition, and urinary 6-sulfatoxymelatonin level.

RESULTS

Parenchyma volume was moderately correlated with urinary 6-sulfatoxymelatonin level (r = .24; p < .01). There was no statistically significant association between parenchyma volume tertile and prostate cancer risk. Men with high parenchyma volume, pineal cysts and calcifications, and low urinary 6-sulfatoxymelatonin levels had almost twice the risk of total prostate cancer as men with low parenchyma volume, no pineal calcifications or cysts, and low urinary 6-sulfatoxymelatonin levels (HR: 1.98; 95% CI: 1.02, 3.84; p: .04).

CONCLUSIONS

Although parenchyma volume is not associated with prostate cancer risk, pineal gland composition and other circadian dynamics may influence risk for prostate cancer. Additional studies are needed to examine the interplay of pineal gland volume, composition, and melatonin levels on prostate cancer risk.

Is there any relationship between autism and pineal gland volume?

Purpose

Abnormalities in melatonin physiology and circadian rhythm are detected in patients with autism. Melatonin is produced predominantly in the pineal gland and the amount of melatonin released is proportional to the pineal gland volume. This study aimed to examine whether the pineal gland volume in children with autism is different from that in healthy children.

Material and methods

Brain magnetic resonance images (MRI) of 120 paediatric patients with autism and 82 control paediatric subjects were examined; pineal parenchymal volume (PPV), pineal cyst rate (PCR), and total pineal gland volume (TPGV) were measured using a multimodality viewer (MMV), but only the TPGVs were measured using a tumour tracking (TT) method. Measurements were taken by 2 separate radiologists.

Results

In patients with autism, the PPV and TPGV according to MMV, and the TPGV according to TT were significantly lower, and the PCR was significantly higher. Moreover, the ratio of PPV to TPGV was significantly lower in the autism patient group. In both groups, the TPGVs were significantly lower in the autism patient group than the controls among all age groups.

Conclusions

Our study was the first to examine TPGVs in detail in paediatric patients with autism using 2 different methods. Low PPV-TPGV and high PCR have been observed in autism. This study also provides comparable reference values for pineal gland size in healthy children or autistic children aged 2-17 years. These results show promising potential for further research to understand the relationship between autism pathogenesis and the pineal gland.

Fluoride exposure and duration and quality of sleep in a Canadian population-based sample

BACKGROUND

Fluoride from dietary and environmental sources may concentrate in calcium-containing regions of the body such as the pineal gland. The pineal gland synthesizes melatonin, a hormone that regulates the sleep-wake cycle. We examined associations between fluoride exposure and sleep outcomes among older adolescents and adults in Canada.

METHODS

We used population-based data from Cycle 3 (2012-2013) of the Canadian Health Measures Survey. Participants were aged 16 to 79 years and 32% lived in communities supplied with fluoridated municipal water. Urinary fluoride concentrations were measured in spot samples and adjusted for specific gravity (UF_SG; n = 1303) and water fluoride concentrations were measured in tap water samples among those who reported drinking tap water (n = 1016). We used multinomial and ordered logistic regression analyses (using both unweighted and survey-weighted data) to examine associations of fluoride exposure with self-reported sleep outcomes, including sleep duration, frequency of sleep problems, and daytime sleepiness. Covariates included age, sex, ethnicity, body mass index, chronic health conditions, and household income.

RESULTS

Median (IQR) UF_SG concentration was 0.67 (0.63) mg/L. Median (IQR) water fluoride concentration was 0.58 (0.27) mg/L among participants living in communities supplied with fluoridated municipal water and 0.01 (0.06) mg/L among those living in non-fluoridated communities. A 0.5 mg/L higher water fluoride level was associated with 34% higher relative risk of reporting sleeping less than the recommended duration for age [unweighted: RRR = 1.34, 95% CI: 1.03, 1.73; p = .026]; the relative risk was higher, though less precise, using survey-weighted data [RRR = 1.96, 95% CI: 0.99, 3.87; p = .05]. UF_SG was not significantly associated with sleep duration. Water fluoride and UF_SG concentration were not significantly associated with frequency of sleep problems or daytime sleepiness.

CONCLUSIONS

Fluoride exposure may contribute to sleeping less than the recommended duration among older adolescents and adults in Canada.

Pineal volume reduction in patients with mild cognitive impairment who converted to Alzheimer's disease

AIM

Pineal parenchymal volume (PPV) reduction is one of the predisposing factors for Alzheimer's disease (AD). Therefore, PPV could be used as a predictor of developing AD in clinical settings. We investigated whether PPV in patients with mild cognitive impairment (MCI) was correlated with conversion of these patients to AD.

METHODS

A total of 237 patients with MCI underwent brain magnetic resonance imaging. A two-sample t-test was used to compare PPV at baseline in MCI patients who converted to AD (MCI-C) with those who did not convert (MCI-NC). Logistic regression analysis with forced entry was used to identify predictors of AD, with variables of PPV, age, sex, education, APOE-ε4 alleles, Mini Mental State Examination score, and total intracranial volume at baseline. Two-way repeated-measures analysis of variance was conducted to compare PPV at baseline and at the last examination in the MCI-C and MCI-NC groups.

RESULTS

PPV in the MCI-C group was significantly lower than that in the MCI-NC group. In logistic regression analysis, two independent predictors of AD were identified: Mini Mental State Examination and PPV. Two-way repeated-measures analysis of variance revealed a significant group effect, but no time effect.

CONCLUSION

The pineal volume is a predictor of AD conversion, and pineal volume reduction in AD starts early when patients are still in the MCI stage. Thus, pineal volume reduction might be useful as a predictor of developing AD in clinical settings.

Investigation of the human pineal gland 3D organization by X-ray phase contrast tomography

Pineal gland (PG) is a part of the human brain epithalamus that plays an important role in sleep, circadian rhythm, immunity, and reproduction. The calcium deposits and lesions in PG interfere with normal function of the organ and can be associated with different health disorders including serious neurological diseases. At the moment, the detailed mechanisms of PG calcifications and PG lesions formation as well as their involvement in pathological processes are not fully understood. The deep and comprehensive study of the structure of the uncut human PG with histological details, poses a stiff challenge to most imaging techniques, due to low spatial resolution, low visibility or to exceedingly aggressive sample preparation. Here, we investigate the whole uncut and unstained human post-mortem PGs by X-ray phase contrast tomography (XPCT). XPCT is an advanced 3D imaging technique, that permits to study of both soft and calcified tissue of a sample at different scales: from the whole organ to cell structure. In our research we simultaneously resolved 3D structure of parenchyma, vascular network and calcifications. Moreover, we distinguished structural details of intact and degenerated PG tissue. We discriminated calcifications with different structure, pinealocytes nuclei and the glial cells processes. All results were validated by histology. Our research clear demonstrated that XPCT is a potential tool for the high resolution 3D imaging of PG morphological features. This technique opens a new perspective to investigate PG dysfunction and understand the mechanisms of onset and progression of diseases involving the pineal gland.

Mechanisms of Fluoride Toxicity: From Enzymes to Underlying Integrative Networks

Fluoride has been employed in laboratory investigations since the early 20th century. These studies opened the understanding of fluoride interventions to fundamental biological processes. Millions of people living in endemic fluorosis areas suffer from various pathological disturbances. The practice of community water fluoridation used prophylactically against dental caries increased concern of adverse fluoride effects. We assessed the publications on fluoride toxicity until June 2020. We present evidence that fluoride is an enzymatic poison, inducing oxidative stress, hormonal disruptions, and neurotoxicity. Fluoride in synergy with aluminum acts as a false signal in G protein cascades of hormonal and neuronal regulations in much lower concentrations than fluoride acting alone. Our review shows the impact of fluoride on human health. We suggest focusing the research on fluoride toxicity to the underlying integrative networks. Ignorance of the pluripotent toxic effects of fluoride might contribute to unexpected epidemics in the future.

Fluoride and Pineal Gland

The pineal gland is an endocrine gland whose main function is the biosynthesis and secretion of melatonin, a hormone responsible for regulating circadian rhythms, e.g., the sleep/wake cycle. Due to its exceptionally high vascularization and its location outside the blood–brain barrier, the pineal gland may accumulate significant amounts of calcium and fluoride, making it the most fluoride-saturated organ of the human body. Both the calcification and accumulation of fluoride may result in melatonin deficiency.

Melatonin-Measurement Methods and the Factors Modifying the Results. A Systematic Review of the Literature

Melatonin plays an important role in regulating the sleep-wake cycle and adaptation to environmental changes. Concentration measurements in bioliquids such as serum/plasma, saliva and urine are widely used to assess peripheral rhythm. The aim of the study was to compare methods and conditions of determinations carried out with the identification of factors potentially affecting the measurements obtained. We have identified a group of modifiable and unmodifiable factors that facilitate data interpretation. Knowledge of modifiers allows you to carefully plan the test protocol and then compare the results. There is no one universal sampling standard, because the choice of method and biofluid depends on the purpose of the study and the research group.

Urinary Excretion of 6-Sulfatoxymelatonin, the Main Metabolite of Melatonin, and Mortality in Stable Outpatient Renal Transplant Recipients

Melatonin is a multifaceted hormone which rises upon the onset of darkness. Pineal synthesis of melatonin is known to be disturbed in patients with end-stage renal disease, but it is not known if its production is restored to normal after successful renal transplantation. We hypothesized that urinary excretion of 6-sulfatoxymelatonin, the major metabolite of melatonin, is lower in renal transplant recipients (RTRs) compared to healthy controls and that this is associated with excess mortality. Urinary 6-sulfatoxymelatonin was measured via LC-MS/MS in 701 stable outpatient RTRs and 285 healthy controls. Median urinary 6-sulfatoxymelatonin in RTR was 13.2 nmol/24 h, which was 47% lower than in healthy controls. Urinary 6-sufatoxymelatonin appeared undetectable in the majority of 36 RTRs with diabetic nephropathy as primary renal disease. Therefore, this subgroup was excluded from further analyses. Of the remaining 665 RTRs, during 5.4 years of follow-up, 110 RTRs died, of whom 38 died due to a cardiovascular cause. In Cox-regression analyses, urinary 6-sulfatoxymelatonin was significantly associated with all-cause mortality (0.60 (0.44–0.81), p = 0.001) and cardiovascular mortality (0.49 (0.29–0.84), p = 0.009), independent of conventional risk factors and kidney function parameters. Based on these results, evaluation and management of melatonin metabolism could be considered for improvement of long-term outcomes in RTRs.

Melatonin and Parkinson Disease: Current Status and Future Perspectives for Molecular Mechanisms

Parkinson disease (PD) is a chronic and neurodegenerative disease with motor and nonmotor symptoms. Multiple pathways are involved in the pathophysiology of PD, including apoptosis, autophagy, oxidative stress, inflammation, α-synuclein aggregation, and changes in the neurotransmitters. Preclinical and clinical studies have shown that melatonin supplementation is an appropriate therapy for PD. Administration of melatonin leads to inhibition of some pathways related to apoptosis, autophagy, oxidative stress, inflammation, α-synuclein aggregation, and dopamine loss in PD. In addition, melatonin improves some nonmotor symptom in patients with PD. Limited studies, however, have evaluated the role of melatonin on molecular mechanisms and clinical symptoms in PD. This review summarizes what is known regarding the impact of melatonin on PD in preclinical and clinical studies.

Fluoride exposure and sleep patterns among older adolescents in the United States: a cross-sectional study of NHANES 2015-2016

BACKGROUND

Fluoride from environmental sources accumulates preferentially in the pineal gland which produces melatonin, the hormone that regulates the sleep-wake cycle. However, the effects of fluoride on sleep regulation remain unknown. This population-based study examined whether chronic low-level fluoride exposure is associated with sleep patterns and daytime sleepiness among older adolescents in the United States (US).

METHOD

This cross-sectional study utilized data from the National Health and Nutrition Examination Survey (2015-2016). We analyzed data from adolescents who had plasma fluoride (n = 473) and water fluoride (n = 419) measures and were not prescribed medication for sleep disorders. Relationships between fluoride exposure and self-reported sleep patterns or daytime sleepiness were examined using survey-weighted linear, binomial logistic or multinomial logistic regression after covariate adjustment. A Holm-Bonferroni correction accounted for multiple comparisons.

RESULTS

The average age of adolescents was 17 years (range = 16-19). Median (IQR) water and plasma fluoride concentrations were 0.27 (0.52) mg/L and 0.29 (0.19) μmol/L respectively. An IQR increase in water fluoride was associated with 1.97 times higher odds of reporting symptoms suggestive of sleep apnea (95% CI: 1.27, 3.05; p = 0.02), a 24 min later bedtime (B = 0.40, 95% CI: 0.10, 0.70; p = 0.05), a 26 min later morning wake time (B = 0.43, 95% CI: 0.13, 0.73; p = 0.04), and among males, a 38% reduction in the odds of reporting snoring (95% CI: 0.45, 0.87, p = 0.03).

CONCLUSIONS

Fluoride exposure may contribute to changes in sleep cycle regulation and sleep behaviors among older adolescents in the US. Additional prospective studies are warranted to examine the effects of fluoride on sleep patterns and determine critical windows of vulnerability for potential effects.

Pineal gland abnormality in major depressive disorder

Patients with major depressive disorder (MDD) often have circadian rhythm alteration and sleep disturbance. The pineal gland regulates the circadian rhythm and sleep by the secretion of melatonin neurohormone. However, the relationship between pineal abnormality and MDD remains elusive. 50 patients with MDD and 35 gender- and age-matched healthy controls underwent high-resolution structural MRI. Pineal parenchymal volume (PPV) was measured manually. Inter-group differences in prevalence of pineal cyst and PPV were examined. In addition, we investigated the correlations between PPV and symptom severity as well as sleep variables in the patient group. Compared to healthy controls, patients with MDD had a higher prevalence of pineal cyst. Moreover, patients had significantly decreased PPV relative to controls. However, no significant correlations were observed between PPV and symptom severity as well as sleep variables. Our findings suggest that pineal abnormality may play a critical role in depression.

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

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

Melatonin in Synaptic Impairments of Alzheimer's Disease

Alzheimer's disease (AD) underlies dementia for millions of people worldwide with no effective treatment. The dementia of AD is thought stem from the impairments of the synapses because of their critical roles in cognition. Melatonin is a neurohormone mainly released by the pineal gland in a circadian manner and it regulates brain functions in various manners. It is reported that both the melatonin deficit and synaptic impairments are present in the very early stage of AD and strongly contribute to the progress of AD. In the mammalian brains, the effects of melatonin are mainly relayed by two of its receptors, melatonin receptor type 1a (MT1) and 1b (MT2). To have a clear idea on the roles of melatonin in synaptic impairments of AD, this review discussed the actions of melatonin and its receptors in the stabilization of synapses, modulation of long-term potentiation, as well as their contributions in the transmissions of glutamatergic, GABAergic and dopaminergic synapses, which are the three main types of synapses relevant to the synaptic strength. The synaptic protective roles of melatonin in AD treatment were also summarized. Regarding its protective roles against amyloid-β neurotoxicity, tau hyperphosphorylation, oxygenation, inflammation as well as synaptic dysfunctions, melatonin may be an ideal therapeutic agent against AD at early stage.

Pineal gland and schizophrenia: A systematic review and meta-analysis

Melatonin (MLT), the main hormone of the pineal gland (PG), is assumed to support initiation and maintenance of sleep, and a stable sleep-wake cycle, exerting antioxidative and neuroprotective actions. Evidence demonstrates that sleep and circadian rhythm abnormalities are very common in schizophrenia patients. Some imaging studies suggest structural abnormalities of the PG in these patients as well. We aimed to critically appraise the literature on PG imaging and melatonin secretion in schizophrenia patients, in comparison to matched healthy controls, and to review placebo-controlled trials of add-on exogenous MLT treatment in schizophrenia patients. In this systematic review, twenty-nine studies were included. Meta-analytical evaluation of data was possible only for MLT secretion finding that midnight plasma levels were significantly reduced in individuals with schizophrenia as compared to healthy controls (Hedge`s g = 1.32, p < 0.01). Imaging studies demonstrated greater prevalence of enlarged calcifications (>1 cm) of the PG (2 out of 2 computed tomography studies) and smaller PG volume (2 out of 3 magnetic resonance studies) compared with healthy controls. Anatomic and functional abnormalities of the PG were not associated with duration of illness or with treatment factors, maybe suggesting them to be primary characteristics of the disease and genetically based. Add-on MLT treatment leads to a modest improvement of objective and subjective sleep quality, of metabolic adverse effects of antipsychotics, and of tardive dyskinesia symptoms in schizophrenia patients. It remains to be established whether MLT treatment in prodromal phases of the disease could prevent neurostructural abnormalities.

Sundown Syndrome in Older Persons: A Scoping Review

OBJECTIVES

To map comprehensive investigations of the sundown syndrome (SS), highlighting its key definition and associated characteristics.

DESIGN

Scoping review of published articles on SS in PubMed, OVID, EMBASE, Scopus, CINAHL, and Science Direct.

SETTING

Post-acute and long-term health care settings.

PARTICIPANTS

Older adults aged ≥60 years.

MEASURES

Articles must present primary data on specific SS behavior, with explicit psychopathological and quantitative outcomes; and/or evening disruptive behavior.

RESULTS

From a total number of 460 articles focusing on psychopathology and standardized outcomes of SS, 23 were retained for the final analysis (n = 1210 subjects). The mean age of participants was 63.2 years, and slightly more participants were women. The samples were recruited by convenience from long-term care facilities and tertiary outpatient clinics. The frequency of SS varied from 2% to 82%, without evident difference between genders and race/ethnicity. Generally, the sundown episode occurred during later daytime, when psychomotor alterations and cognitive disturbance manifested repeatedly. The symptomatic manifestations of SS were heterogeneous across the studies. Demographic risk factors were inconsistent. Although some authors have viewed cognitive impairment as a substantive predisposing factor to SS, others supported SS as a predictor of looming cognitive decline. The disrupted circadian rhythm was the most accepted pathophysiology. To date, clinical trials to guide the management of SS with specific pharmacologic and nonpharmacologic approaches are scant.

CONCLUSIONS AND IMPLICATIONS

SS can be viewed as a cyclic delirium-like condition affecting the older population around the sunset hour that may last for a few hours. The scarcity of comprehensive studies makes it difficult to determine whether and to what extent it can represent a distinct disease, a prodromal stage of dementia, or an epiphenomenon of incipient or worsening dementia. Extensive gathering of clinical data from multiple health care settings, using uniform measurement tools, is much needed.

Fluoride Exposure in Early Life as the Possible Root Cause of Disease In Later Life

Fluoride, one of the most celebrated ingredients for the prevention of dental caries in the 20th century, has also been controversial for its use in dentifrices and other applications. In the current review, we have concentrated primarily on early-life exposure to fluoride and how it may affect the various organs. The most recent controversial aspects of fluoride are related to toxicity of the developing brain and how it may possibly result in the decrease of intelligence quotient (IQ), autism, and calcification of the pineal gland. In addition, it has been reported to have possible effects on bone and thyroid glands. If nutritional stress is applied during a critical period of growth and development, the organ(s) and/or body will never recover once they pass through the critical period. For example, if animals are force-fed during experiments, they will simply get fat but never reach the normal size. Although early-life fluoride exposure causing fluorosis is well reported in the literature, the dental profession considers it primarily as an esthetic rather than a serious systemic problem. In the current review, we wanted to raise the possibility of future disease as a result of early-life exposure to fluoride. It is not currently known how fluoride will become a cause of future disease. Studies of other nutritional factors have shown that the effects of early nutritional stress are a cause of disease in later life.

Evaluation of human pineal gland acetylserotonin O-methyltransferase immunoreactivity in suicide: A preliminary study

Disorders of the serotonergic system are especially known to be present in the neurobiology of suicidal behavior. Studies investigating melatonin levels show that changes in pineal gland functions may also play a role in the pathogenesis of suicide. However, to our knowledge, there are no studies evaluating the activity of pinealocytes responsible for melatonin synthesis in suicide. This preliminary study aimed to investigate the relationship among pinealocyte, acetylserotonin O-methyltransferase (ASMT) immunoreactivity, and suicide. Samples of pineal gland, cerebrospinal fluid, blood, and urine were obtained from 21 suicide and 21 non-suicide cases on which medicolegal autopsies were performed. Expression of ASMT in human pineal gland was evaluated by immunohistochemical methods. A scoring system was used to define the anti-ASMT-positive staining in the sections. Enzyme-linked immunosorbent assays were employed to assess serum and cerebrospinal fluid melatonin levels and blood and urine noradrenaline levels. The ASMT-immunopositive pinealocyte count was observed to be lower in suicide cases compared to the non-suicide cases. With the exception of two cases (with moderate staining), all graded scores were 3 (strong staining) in non-suicide group, whereas scores were 1 (mild staining) or 2 (moderate staining) in the suicide group. Melatonin levels in the blood were lower among the suicide victims. These results support decreased pineal gland activity in suicide. However, further studies are needed to assess whether these changes are related to a psychiatric disorder.

New perspectives on the role of melatonin in human sleep, circadian rhythms and their regulation

In mammals, a central circadian clock, located in the suprachiasmatic nuclei (SCN) of the hypothalamus, tunes the innate circadian physiological rhythms to the ambient 24 h light-dark cycle to invigorate and optimize the internal temporal order. The SCN-activated, light-inhibited production of melatonin conveys the message of darkness to the clock and induces night-state physiological functions, for example, sleep/wake blood pressure and metabolism. Clinically meaningful effects of melatonin treatment have been demonstrated in placebo-controlled trials in humans, particularly in disorders associated with diminished or misaligned melatonin rhythms, for example, circadian rhythm-related sleep disorders, jet lag and shift work, insomnia in children with neurodevelopmental disorders, poor (non-restorative) sleep quality, non-dipping nocturnal blood pressure (nocturnal hypertension) and Alzheimer's disease (AD). The diminished production of melatonin at the very early stages of AD, the role of melatonin in the restorative value of sleep (perceived sleep quality) and its sleep-anticipating effects resulting in attenuated activation of certain brain networks are gaining a new perspective as the role of poor sleep quality in the build-up of β amyloid, particularly in the precuneus, is unravelled. As a result of the recently discovered relationship between circadian clock, sleep and neurodegeneration, new prospects of using melatonin for early intervention, to promote healthy physical and mental ageing, are of prime interest in view of the emerging link to the aetiology of Alzheimer's disease. LINKED ARTICLES: This article is part of a themed section on Recent Developments in Research of Melatonin and its Potential Therapeutic Applications. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v175.16/issuetoc.

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

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

Sleep disorders in children with incidental pineal cyst on MRI: a pilot study

INTRODUCTION

For several years, pineal cysts have been considered an incidental finding on brain MRI's even though research and case reports have shown a possible association of pineal cysts with headaches and sleep disturbances. This pilot study aims to evaluate sleep disorders in school-age children with an incidental pineal cyst in an otherwise normal brain MRI.

METHOD

Children aged 6-12 years, who were referred for evaluation of headaches, tics, or syncope, and had an incidental pineal cyst on an otherwise normal brain MRI were included and compared to a control group of children with the same referral reasons but with a normal MRI and to a cohort of normal controls. The Sleep Disturbance Scale for Children (SDSC) was administered to the parents. Exclusion criteria included use of medications that affect sleep, seizures, brain abnormalities, tumors, or comorbid medical conditions that affect sleep.

RESULTS

Eighteen children (11 females) with pineal cysts, 19 children with normal MRI, and 100 age- and sex-matched controls were included in our study. There were statistically significant differences in the total SDSC score (with a difference of 10 between the median scores) and in two of the six domains of this scale. Children with pineal cysts scored significantly higher in the domains of disorders of excessive sleepiness and disorders of initiating and maintaining sleep than the two control groups. The scores in these two domains correlated significantly with the size of the cyst.

CONCLUSION

School-age children with pineal cysts have significantly increased levels of sleepiness and difficulty with sleep initiation and maintenance.

Daytime Sleep Disturbance in Night Shift Work and the Role of PERIOD3

STUDY OBJECTIVES

Recent evidence indicates that daytime sleep disturbance associated with night shift work may arise from both circadian misalignment and sleep reactivity to stress. This presents an important clinical challenge because there are limited means of predicting and distinguishing between the two mechanisms, and the respective treatments differ categorically; however, there is support that a polymorphism in the PERIOD3 gene (PER3) may indicate differences in vulnerability to daytime sleep disturbance in shift workers.

METHODS

We recruited 30 fixed night shift workers for laboratory assessments of circadian misalignment (dim light melatonin onset), sleep reactivity to stress (Ford Insomnia Response to Stress Test), daytime sleep disturbance (daytime Insomnia Severity Index), and PER3 genotype (PER3^4/4, PER3^5/-). The two mechanisms for daytime sleep disturbance (circadian misalignment and sleep reactivity to stress) were compared between PER3 genotypes.

RESULTS

Disturbed daytime sleep in the PER3^4/4 group was more likely related to sleep reactivity to stress, whereas disturbed sleep in the PER3^5/- group was more likely related to circadian misalignment. Exploratory analyses also revealed a blunted melatonin amplitude in the PER3^4/4 genotype group.

CONCLUSIONS

This study provides further evidence for multiple mechanisms (ie, circadian misalignment versus sleep reactivity to stress) associated with daytime sleep disturbances in shift workers. Additionally, it provides the new finding that PER3 genotype may play an important role in individual vulnerability to the different mechanisms of daytime sleep disturbance in night shift workers.

N,N-dimethyltryptamine and the pineal gland: Separating fact from myth

The pineal gland has a romantic history, from pharaonic Egypt, where it was equated with the eye of Horus, through various religious traditions, where it was considered the seat of the soul, the third eye, etc. Recent incarnations of these notions have suggested that N,N-dimethyltryptamine is secreted by the pineal gland at birth, during dreaming, and at near death to produce out of body experiences. Scientific evidence, however, is not consistent with these ideas. The adult pineal gland weighs less than 0.2 g, and its principal function is to produce about 30 µg per day of melatonin, a hormone that regulates circadian rhythm through very high affinity interactions with melatonin receptors. It is clear that very minute concentrations of N,N-dimethyltryptamine have been detected in the brain, but they are not sufficient to produce psychoactive effects. Alternative explanations are presented to explain how stress and near death can produce altered states of consciousness without invoking the intermediacy of N,N-dimethyltryptamine.

Prevalence of pineal gland calcification as an incidental finding in patients referred for implant dental therapy

PURPOSE

Pineal gland calcification has been proposed to play a role in the pathogenesis of Alzheimer disease. This study evaluated the prevalence and extent of pineal gland calcification in cone-beam computed tomography (CBCT) scans of patients referred for dental implant therapy who could possibly be a vulnerable group for this condition.

MATERIALS AND METHODS

A retrospective evaluation of 500 CBCT scans was conducted. Scans that showed the area where the pineal gland was located were included. The scans were initially screened by a single observer to record the prevalence and extent of calcification. Six weeks following the completion of the study, another investigator randomly reviewed and selected 50 scans to investigate inter-observer variation, which was evaluated using reliability analysis statistics. The prevalence and measurements of the calcifications were reported using descriptive statistics. The chi-square test was used to compare the prevalence between males and females.

RESULTS

The prevalence of pineal gland calcification was 58.8%. There was no statistically significant correlation between age and the extent of the calcification. The prevalence of calcification was 58.6% in females and 59.0% in males. The average anteroposterior measurement was 3.73±1.63 mm, while the average mediolateral measurement was 3.47±1.31 mm. The average total calcified area was 9.79±7.59 mm².

CONCLUSION

The prevalence of pineal gland calcification was high in patients undergoing implant therapy. While not all pineal gland calcifications lead to neurodegenerative disorders, they should be strongly considered in the presence of any symptoms as a reason to initiate further investigations.

The clock is ticking. Ageing of the circadian system: From physiology to cell cycle

The circadian system is the responsible to organise the internal temporal order in relation to the environment of every process of the organisms producing the circadian rhythms. These rhythms have a fixed phase relationship among them and with the environment in order to optimise the available energy and resources. From a cellular level, circadian rhythms are controlled by genetic positive and negative auto-regulated transcriptional and translational feedback loops, which generate 24h rhythms in mRNA and protein levels of the clock components. It has been described about 10% of the genome is controlled by clock genes, with special relevance, due to its implications, to the cell cycle. Ageing is a deleterious process which affects all the organisms' structures including circadian system. The circadian system's ageing may produce a disorganisation among the circadian rhythms, arrhythmicity and, even, disconnection from the environment, resulting in a detrimental situation to the organism. In addition, some environmental conditions can produce circadian disruption, also called chronodisruption, which may produce many pathologies including accelerated ageing. Finally, some strategies to prevent, palliate or counteract chronodisruption effects have been proposed to enhance the circadian system, also called chronoenhancement. This review tries to gather recent advances in the chronobiology of the ageing process, including cell cycle, neurogenesis process and physiology.

Mechanisms of Melatonin in Alleviating Alzheimer's Disease

Alzheimer's disease (AD) is a chronic, progressive and prevalent neurodegenerative disease characterized by the loss of higher cognitive functions and an associated loss of memory. The thus far "incurable" stigma for AD prevails because of variations in the success rates of different treatment protocols in animal and human studies. Among the classical hypotheses explaining AD pathogenesis, the amyloid hypothesis is currently being targeted for drug development. The underlying concept is to prevent the formation of these neurotoxic peptides which play a central role in AD pathology and trigger a multispectral cascade of neurodegenerative processes post-aggregation. This could possibly be achieved by pharmacological inhibition of β- or γ-secretase or stimulating the nonamyloidogenic α-secretase. Melatonin the pineal hormone is a multifunctioning indoleamine. Production of this amphiphilic molecule diminishes with advancing age and this decrease runs parallel with the progression of AD which itself explains the potential benefits of melatonin in line of development and devastating consequences of the disease progression. Our recent studies have revealed a novel mechanism by which melatonin stimulates the nonamyloidogenic processing and inhibits the amyloidogenic processing of β-amyloid precursor protein (βAPP) by stimulating α -secretases and consequently down regulating both β- and γ-secretases at the transcriptional level. In this review, we discuss and evaluate the neuroprotective functions of melatonin in AD pathogenesis, including its role in the classical hypotheses in cellular and animal models and clinical interventions in AD patients, and suggest that with early detection, melatonin treatment is qualified to be an anti-AD therapy.

Pineal Gland Volume Assessed by MRI and Its Correlation with 6-Sulfatoxymelatonin Levels among Older Men

The pineal gland produces the hormone melatonin, and its volume may influence melatonin levels. We describe an innovative method for estimating pineal volume in humans and present the association of pineal parenchyma volume with levels of the primary melatonin metabolite, 6-sulfatoxymelatonin. We selected a random sample of 122 older Icelandic men nested within the AGES-Reykjavik cohort and measured their total pineal volume, their parenchyma volume, and the extent of calcification and cysts. For volume estimations we used manual segmentation of magnetic resonance images in the axial plane with simultaneous side-by-side view of the sagittal and coronal plane. We used multivariable adjusted linear regression models to estimate the association of pineal parenchyma volume and baseline characteristics, including 6-sulfatoxymelatonin levels. We used logistic regression to test for differences in first morning urinary 6-sulfatoxymelatonin levels among men with or without cystic or calcified glands. The pineal glands varied in volume, shape, and composition. Cysts were present in 59% of the glands and calcifications in 21%. The mean total pineal volume measured 207 mm(3) (range 65-536 mm(3)) and parenchyma volume 178 mm(3) (range 65-503 mm(3)). In multivariable-adjusted models, pineal parenchyma volume was positively correlated with 6-sulfatoxymelatonin levels (β = 0.52, p < 0.001). Levels of 6-sulfatoxymelatonin did not differ significantly by presence of cysts or calcification. By using an innovative method for pineal assessment, we found pineal parenchyma volume to be positively correlated with 6-sulfatoxymelatonin levels, in line with other recent studies.

Associations of pineal volume, chronotype and symptom severity in adults with attention deficit hyperactivity disorder and healthy controls

The pineal gland, as part of the human epithalamus, is the main production site of peripheral melatonin, which promotes the modulation of sleep patterns, circadian rhythms and circadian preferences (morningness vs. eveningness). The present study analyses the pineal gland volume (PGV) and its association with circadian preferences and symptom severity in adult ADHD patients compared to healthy controls. PGV was determined manually using high-resolution 3T MRI (T1-magnetization prepared rapid gradient echo) in medication free adult ADHD patients (N=74) compared to healthy controls (N=86). Moreover, the Morningness-Eveningness Questionnaire (MEQ), the ADHD Diagnostic Checklist and the Wender-Utah Rating Scale were conducted. PGV differed between both groups (patients: 59.9±33.8mm(3); healthy controls: 71.4±27.2mm(3), P=0.04). In ADHD patients, more eveningness types were revealed (patients: 29%; healthy controls: 17%; P=0.05) and sum scores of the MEQ were lower (patients: 45.8±11.5; healthy controls 67.2±10.1; P<0.001). Multiple regression analyses indicated a positive correlation of PGV and MEQ scores in ADHD (β=0.856, P=0.003) but not in healthy controls (β=0.054, P=0.688). Patients' MEQ scores (β=-0.473, P=0.003) were negatively correlated to ADHD symptoms. The present results suggest a linkage between the PGV and circadian preference in adults with ADHD and an association of the circadian preference to symptom severity. This may facilitate the development of new chronobiological treatment approaches for the add-on treatment in ADHD.

A Review of Melatonin, Its Receptors and Drugs

After a Turkish scientist took Nobel Prize due to his contributions to understand clock genes, melatonin, closely related to these genes, may begin to shine. Melatonin, a hormone secreted from the pineal gland at night, plays roles in regulating sleep-wake cycle, pubertal development and seasonal adaptation. Melatonin has antinociceptive, antidepressant, anxiolytic, antineophobic, locomotor activity-regulating, neuroprotective, anti-inflammatory, pain-modulating, blood pressure-reducing, retinal, vascular, anti-tumor and antioxidant effects. It is related with memory, ovarian physiology, and osteoblast differentiation. Pathologies associated with an increase or decrease in melatonin levels are summarized in the review. Melatonin affects by four mechanisms: 1) Binding to melatonin receptors in plasma membrane, 2) Binding to intracellular proteins such as calmoduline, 3) Binding to Orphan nuclear receptors, and 4) Antioxidant effect. Receptors associated with melatonin are as follows: 1) Melatonin receptor type 1a: MT1 (on cell membrane), 2) Melatonin receptor type 1b: MT2 (on cell membrane), 3) Melatonin receptor type 1c (found in fish, amphibians and birds), 4) Quinone reductase 2 enzyme (MT3 receptor, a detoxification enzyme), 5) RZR/RORα: Retinoid-related Orphan nuclear hormone receptor (with this receptor, melatonin binds to the transcription factors in nucleus), and 6) GPR50: X-linked Melatonin-related Orphan receptor (it is effective in binding of melatonin to MT1). Melatonin agonists such as ramelteon, agomelatine, circadin, TIK-301 and tasimelteon are introduced and side effects will be discussed. In conclusion, melatonin and related drugs is a new and promising era for medicine. Melatonin receptors and melatonin drugs will take attention with greater interest day by day in the future.

Melatonin rhythms in renal transplant recipients with sleep-wake disturbances

We assessed salivary melatonin levels in renal transplant (RTx) recipients who participated in a randomised, multicentre wait-list controlled trial on the effect of bright light therapy on their sleep and circadian rhythms. A large proportion of RTx recipients in our cohort had unexpectedly low melatonin values, which precluded calculation of the dim-light melatonin onset (DLMO) as a circadian marker. Thus, the aim of this post hoc analysis was to describe the melatonin profile of home-dwelling RTx recipients diagnosed with sleep-wake disturbances (SWDs). The participants were characterised by means of sleep questionnaires, validated psychometric instruments [Pittsburgh sleep quality Index (PSQI), Epworth sleepiness scale (ESS), Morningness-Eveningness Questionnaire (MEQ) and Depression, Anxiety and Stress Scale (DASS)] in addition to melatonin assay in saliva. Data were analysed with descriptive statistics and group comparisons made with appropriate post hoc tests. RTx recipients [n = 29 (aged 54.83 ± 13.73, transplanted 10.62 ± 6.84 years ago)] were retrospectively grouped into two groups: RTx recipients whose dim light melatonin onset (DLMO) could be calculated (n = 11) and those whose DLMO could not be calculated (n = 18). RTx recipients having a measurable DLMO had a number of differences from those without DLMO: they were younger [46.4 ± 14.9 compared to 60.0 ± 10.3 (p = .007)], had higher haemoglobin values [135.36 ± 12.01 versus 122.82 ± 11.56 (p = .01)], less anxiety [4 (0;8) versus 12 (6.5;14) (p = .021)] and a better overall sense of coherence [SOC Score: 71.09 ± 12.78 versus 56.28 ± 15.48 (p = 0.013)]. These results suggest that RTx recipients whose DLMO could be calculated have less health impairments, underlying the relevance of a stable circadian system.

Chronic fluorosis: The disease and its anaesthetic implications

Chronic fluorosis is a widespread disease-related to the ingestion of high levels of fluoride through water and food. Prolonged ingestion of fluoride adversely affects the teeth, bones and other organs and alters their anatomy and physiology. Fluoride excess is a risk factor in cardiovascular disease and other major diseases, including hypothyroidism, diabetes and obesity. Although anaesthesiologists may be aware of its skeletal and dental manifestations, other systemic manifestations, some of which may impact anaesthetic management are relatively unknown. Keeping this in mind, the topic of chronic fluorosis was hand searched from textbooks, scientific journals and electronically through Google, PubMed and other scientific databases. This article concentrates on the effect of chronic fluorosis on various organ systems, its clinical features, diagnosis and the anaesthetic implications of the disease.