Rs4862705 in the melatonin receptor 1A gene is associated with renal function decline in type 1 diabetes individuals.

Aim: The pathogenesis of chronic diabetes complications has oxidative stress as one of the major elements, and single-nucleotide polymorphisms (SNPs) in genes belonging to antioxidant pathways modulate susceptibility to these complications. Considering that melatonin is a powerful antioxidant compound, our aim was to explore, in a longitudinal cohort study of type 1 diabetes (T1D) individuals, the association of microvascular complications and SNPs in the gene encoding melatonin receptor 1A (MTNR1A). Methods: Eight SNPs in MTNR1A were genotyped in 489 T1D individuals. Besides cross-sectional analyses of SNPs with each one of the microvascular complications (distal polyneuropathy, cardiovascular autonomic neuropathy, retinopathy, and diabetic kidney disease), a longitudinal analysis evaluated the associations of SNPs with renal function decline in 411 individuals followed up for a median of 8 years. In a subgroup of participants, the association of complications with urinary 6-sulfatoxymelatonin (aMT6s) concentration was investigated. Results: The group of individuals with a renal function decline ≥ 5 mL min-1 1.73 m-2 year-1 presented a higher frequency of the A allele of rs4862705 in comparison with nondecliners, even after adjustment for confounding variables (OR = 1.84, 95% CI = 1.20-2.82; p = 0.0046). No other significant associations were found. Conclusions: This is the first study showing an association between a variant in a gene belonging to the melatonin system and renal function decline in the diabetic setting.

Human social isolation and stress: a systematic review of different contexts and recommendations for future studies

Abstract Objectives The emergence of the coronavirus disease 2019 (COVID-19) pandemic and subsequent lockdowns and social distancing measures adopted worldwide raised questions about the possible health effects of human social isolation. Methods We conducted a systematic review on PubMed, Scopus, and Embase electronic databases using terms related to human social isolation - defined as the isolation of an individual from regular routines and usual social contact - and psychological stress, searching for simulated or naturalistic isolation environments. We present the main results, as well as the validity and limitations of each model. PROSPERO registry number: CRD42021241880. Results Despite the diversity of contexts reviewed, some outcomes almost ubiquitously relate to psychological stress, i.e., longer periods, expectation of a longer period, confinement, lack of social interaction, and support. Based on the results, and considering that most studies were not designed for the purpose of understanding isolation itself, we propose a group of recommendations for future experimental or naturalistic research on the topic. Conclusion Evidence on the impact of different situations in which individuals are subjected to social isolation can assist in development of directed preventive strategies to support people under similar circumstances. Such strategies might increase the general public's compliance with social distancing as a non-pharmacological intervention for emerging infectious diseases.

Taking biological rhythms into account: From study design to results reporting.

Numerous physiological and behavioral processes in living organisms exhibit strong rhythmicity and are regulated within a 24-hour cycle. These include locomotor activity and sleep patterns, feeding-fasting cycles, hormone synthesis, body temperature, and even mood and cognitive abilities, all of which are segregated into different phases throughout the day. These processes are governed by the internal timing system, a hierarchical multi-oscillator structure conserved across all organisms, from bacteria to humans. Circadian rhythms have been seen across multiple taxonomic kingdoms. In mammals, a hierarchical internal timing system is comprised of so-called central and periphereal clocks. Although these rhythms are intrinsic, they are under environmental influences, such as seasonal temperature changes, photoperiod variations, and day-night cycles. Recognizing the existence of biological rhythms and their primary external influences is crucial when designing and reporting experiments. Neglecting these physiological variations may result in inconsistent findings and misinterpretations. Thus, here we propose to incorporate biological rhythms into all stages of human and animal research, including experiment design, analysis, and reporting of findings. We also provide a flowchart to support decision-making during the design process, considering biological rhythmicity, along with a checklist outlining key factors that should be considered and documented throughout the study. This comprehensive approach not only benefits the field of chronobiology but also holds value for various other research disciplines. The insights gained from this study have the potential to enhance the validity, reproducibility, and overall quality of scientific investigations, providing valuable guidance for planning, developing, and communicating scientific studies.

Absence of melatonin during development impairs craniofacial and dental onset in rats.

OBJECTIVE: Herein, we evaluated pinealectomy-induced melatonin absence to determine its effects on craniofacial and dental development in the offspring. DESIGN: Female Wistar rats in three groups, i.e., intact pregnant rats, pinealectomized pregnant rats (PINX), and pinealectomized pregnant rats subjected to oral melatonin replacement therapy, were crossed 30 days after surgery. The heads of 7-day-old pups were harvested for cephalometric and histological analyses, and maxillae and incisors were collected for mRNA expression analysis. RESULTS: The PINX pups exhibited a reduction in neurocranial and facial parameters such as a decrease in alveolar bone area, incisor size and proliferation, and an increase in odontoblasts and the dentin layer. Based on incisor mRNA expression analysis, we found that Dmp1 expression was upregulated, whereas Col1a1 expression was downregulated. Maxillary mRNA expression revealed that Rankl expression was upregulated, whereas that of Opn and Osx was downregulated. CONCLUSION: Our results demonstrated that the absence of maternal melatonin during early life could affect dental and maxillary development in offspring, as well as delay odontogenesis and osteogenesis in maxillary tissues. CLINICAL RELEVANCE: Our findings suggest that disruptions or a lack of melatonin during pregnancy may cause changes in craniofacial and dental development, at least in animal experiments; however, in humans, these feedings are still poorly understood, and thus careful evaluations of melatonin levels in humans need to be investigated in craniofacial alterations.

Melatonin Synthesis Enzymes Activity: Radiometric Assays for AANAT, ASMT, and TPH.

Melatonin is synthesized and secreted by the pineal gland in mammals. Its synthesis is triggered at night by norepinephrine released in the interstices of the gland. This nocturnal production is dependent on the transcription, translation, and/or activation of the enzymes arylalkylamine-N-acetyltransferase (AANAT), acetylserotonin O-methyltransferase (ASMT), and tryptophan hydroxylase (TPH). In this chapter, the methodology for the analysis of AANAT, ASMT, and TPH activities by radiometric assays will be presented. Several papers were published by our group utilizing these methodologies, evaluating the enzymes modulation by voltage-gated calcium channels, angiotensin II, insulin, anhydroecgonine methyl ester (AEME, crack-cocaine product), ethanol, monosodium glutamate (MSG), signaling pathways such as NFkB, and pathophysiological conditions such as diabetes.

Pinealectomy in Rats.

The pinealectomy technique consists of the surgical removal of the superficial pineal gland. This procedure allows the ablation of circulating indoles produced by this gland. Withdrawal of systemic melatonin, a pineal hormone, affects animal circadian rhythms and induces several physiological changes that are the subject of many investigations. In this chapter, we describe the pinealectomy protocol adapted to rats. We describe the animal placement on the stereotaxic fixation system, and the procedure for the pineal gland removal and animal recovery from surgery.

Pineal Microdialysis.

Pineal microdialysis is characterized by the real-time monitoring of melatonin, neurotransmitters, metabolites, and other compounds released by the pineal gland throughout 24 h. It is a technique with great advantages that allows in vivo study of the ongoing pineal gland metabolism. In this chapter, we describe the entire process of pineal microdialysis that includes probe manufacturing, surgical procedure for its implantation, and the sample collection process.

Pineal Gland Culture.

Pineal gland secretes the hormone melatonin at night with a circadian rhythm. The synthesis and secretion of melatonin are stimulated at night by norepinephrine released by sympathetic postganglionic neurons projecting from the superior cervical ganglia. Norepinephrine simultaneously activates α- and ß-adrenoceptors, triggering melatonin synthesis.To study the regulation of melatonin production and secretion, it is very convenient to use an ex vivo preparation. Thus, it is possible to keep intact pineal glands in culture and to study the actions of agonists, antagonists, modulators, toxic agents, etc., in melatonin synthesis. Artificial melatonin synthesis stimulation in vitro is usually achieved by using a ß-adrenergic agonist alone or in association with an α-adrenergic agonist. In this chapter, the methodology of cultured pineal glands will be described. Several papers were published by our group using this methodology, approaching the role played in melatonin synthesis control by angiotensin II and IV, insulin, glutamate, voltage-gated calcium channels, anhydroecgonine methyl ester (AEME, crack-cocaine product), monosodium glutamate (MSG), signaling pathways like NFkB, pathophysiological conditions like diabetes, etc.

Human Social Isolation and Stress: A Systematic Review of Different Contexts and Recommendations for Future Studies.

OBJECTIVES: The emergence of COVID-19 pandemic and subsequent lockdowns and social distancing measures adopted worldwide raised questions about the possible health effects of human social isolation. METHODS: We conducted a systematic review on PubMed, Scopus and Embase electronic databases using terms related to human social isolation - defined as the isolation of an individual from regular routines and usual social contact - and psychological stress, searching for simulated or naturalistic isolation environments. We present the main results, as well as the validity and limitations of each model. PROSPERO registry number: CRD42021241880. RESULTS: Despite the diversity of contexts reviewed, some outcomes almost ubiquitously relate to psychological stress, i.e. longer periods, expectation of a longer period, confinement, lack of social interaction and support. Based on the results, considering that most studies were not designed for the purpose of understanding isolation itself, we propose a group of recommendations for future experimental or naturalistic research on the topic. CONCLUSION: Evidence on the impact of different situations in which individuals are subjected to social isolation can assist in the development of directed preventive strategies to support people under similar circumstances. Such strategies might increase the compliance of the general public to social distancing as a non-pharmacological intervention for emerging infectious diseases.

The Crosstalk between Melatonin and Sex Steroid Hormones.

Melatonin, an indolamine mainly released from the pineal gland, is associated with many biological functions, namely, the modulation of circadian and seasonal rhythms, sleep inducer, regulator of energy metabolism, antioxidant, and anticarcinogenic. Although several pieces of evidence also recognize the influence of melatonin in the reproductive physiology, the crosstalk between melatonin and sex hormones is not clear. Here, we review the effects of sex differences in the circulating levels of melatonin and update the current knowledge on the link between sex hormones and melatonin. Furthermore, we explore the effects of melatonin on gonadal steroidogenesis and hormonal control in females. The literature review shows that despite the strong evidence that sex differences impact on the circadian profiles of melatonin, reports are still considerably ambiguous, and these differences may arise from several factors, like the use of contraceptive pills, hormonal status, and sleep deprivation. Furthermore, there has been an inconclusive debate about the characteristics of the reciprocal relationship between melatonin and reproductive hormones. In this regard, there is evidence for the role of melatonin in gonadal steroidogenesis brought about by research that shows that melatonin affects multiple transduction pathways that modulate Sertoli cell physiology and consequently spermatogenesis, and also estrogen and progesterone production. From the outcome of our research, it is possible to conclude that understanding the correlation between melatonin and reproductive hormones is crucial for the correction of several complications occurring during pregnancy, like preeclampsia, and for the control of climacteric symptoms.

Quasi-Experimental study of effects of lighting on rest, activity and melatonin in postpartum women.

OBJECTIVES: to compare the parameters of the activity/rest cycle of early postpartum breastfeeding women under a controlled and uncontrolled long wavelength ray light regimen. METHODS: quasi-experimental study with breastfeeding women and their babies during postnatal rooming-in, São Paulo, Brazil. Participants were allocated to either an experimental (intervention) or a comparison group. The intervention involved exposure of the woman in a controlled room with artificial long wavelength ray light at night. Each woman's level of 6-sulfatoxymelatonin at 24 hours and activity/rest times was analyzed. RESULTS: the mean activity/rest times of women in the experimental and comparison groups were similar. The mean percentages of total load of 6-sulfatoxymelatonin during the day and night were similar (p=0.09). At 24 hours, the experimental group presented a significantly lower mean percentage of total load compared to the comparison group (p=0.04). CONCLUSIONS: women who stayed in the room with long-wavelength artificial light showed no difference in activity/rest and 6-sulfatoxymelatonin levels in the early postpartum period.

Melatonin regulates maternal pancreatic remodeling and B-cell function during pregnancy and lactation.

The endocrine pancreas of pregnant rats shows evident plasticity, which allows the morphological structures to return to the nonpregnant state right after delivery. Furthermore, it is well-known the role of melatonin in the maintenance of the endocrine pancreas and its tropism. Studies indicate increasing nocturnal serum concentrations of maternal melatonin during pregnancy in both humans and rodents. The present study investigated the role of melatonin on energy metabolism and in pancreatic function and remodeling during pregnancy and early lactation in rats. The results confirm that the absence of melatonin during pregnancy impairs glucose metabolism. In addition, there is a dysregulation in insulin secretion at various stages of the development of pregnancy and an apparent failure in the glucose-stimulated insulin secretion during the lactation period, evidencing the role of melatonin on the regulation of insulin secretion. This mechanism seems not to be dependent on the antioxidant effect of melatonin and probably dependent on MT2 receptors. We also observed changes in the mechanisms of death and cell proliferation at the end of pregnancy and beginning of lactation, crucial periods for pancreatic remodeling. The present observations strongly suggest that both functionality and remodeling of the endocrine pancreas are impaired in the absence of melatonin and its adequate replacement, mimicking the physiological increase seen during pregnancy, is able to reverse some of the damage observed. Thus, we conclude that pineal melatonin is important to metabolic adaptation to pregnancy and both the functionality of the beta cells and the remodeling of the pancreas during pregnancy and early lactation, ensuring the return to nonpregnancy conditions.

The effects of melatonin daily supplementation to aged rats on the ability to withstand cold, thermoregulation and body weight.

AIMS: Investigate the role of melatonin on the regulation of body temperature in aged animals that have impaired melatonin production. MATERIAL AND METHODS: Aged Male Wistar rats were randomly assigned to the following groups: 1) control (vehicle added to the water bottles during the dark phase) and 2) melatonin-treated (10 mg/kg melatonin added to the water bottles during the dark phase). Before and after 16 weeks of vehicle or melatonin treatment, control group and melatonin-treated animals were acutely exposed to 18 °C for 2 h for an acute cold challenge and thermal images were obtained using an infrared camera. After 16 weeks, animals were euthanized and brown and beige adipocytes were collected for analysis of genes involved in the thermogenesis process by real-time PCR, and the uncoupling protein expression was evaluated by immunoblotting. Browning intensity of beige adipocytes were quantified by staining with hematoxylin-eosin. KEY FINDINGS: Chronic melatonin supplementation induced a minor increase in body mass and increased the animal's thermogenic potential in the cold acute challenge. Brown and beige adipocytes acted in a coordinated and complementary way to ensure adequate heat production. SIGNIFICANCE: Melatonin plays an important role in the thermoregulatory mechanisms, ensuring greater capacity to withstand cold and, also, participating in the regulation of energy balance.

Maternal pineal melatonin in gestation and lactation physiology, and in fetal development and programming.

Pregnancy and lactation are reproductive processes that rely on physiological adaptations that should be timely and adequately triggered to guarantee both maternal and fetal health. Pineal melatonin is a hormone that presents daily and seasonal variations that synchronizes the organism's physiology to the different demands across time through its specific mechanisms and ways of action. The reproductive system is a notable target for melatonin as it actively participates on reproductive physiology and regulates the hypothalamus-pituitary-gonads axis, influencing gonadotropins and sexual hormones synthesis and release. For its antioxidant properties, melatonin is also vital for the oocytes and spermatozoa quality and viability, and for blastocyst development. Maternal pineal melatonin blood levels increase during pregnancy and triggers the maternal physiological alterations in energy metabolism both during pregnancy and lactation to cope with the energy demands of both periods and to promote adequate mammary gland development. Moreover, maternal melatonin freely crosses the placenta and is the only source of this hormone to the fetus. It importantly times the conceptus physiology and influences its development and programing of several functions that depend on neural and brain development, ultimately priming adult behavior and energy and glucose metabolism. The present review aims to explain the above listed melatonin functions, including the potential alterations observed in the progeny gestated under maternal chronodisruption and/or hypomelatoninemia.

Quasi-Experimental study of effects of lighting on rest, activity and melatonin in postpartum women / Estudo Quasi-Experimental dos efeitos da iluminação no repouso, atividade e melatonina em puérperas / Estudio cuasiexperimental de los efectos de la iluminación em reposo, actividad y melatonina em mujeres posparto

ABSTRACT Objectives: to compare the parameters of the activity/rest cycle of early postpartum breastfeeding women under a controlled and uncontrolled long wavelength ray light regimen. Methods: quasi-experimental study with breastfeeding women and their babies during postnatal rooming-in, São Paulo, Brazil. Participants were allocated to either an experimental (intervention) or a comparison group. The intervention involved exposure of the woman in a controlled room with artificial long wavelength ray light at night. Each woman's level of 6-sulfatoxymelatonin at 24 hours and activity/rest times was analyzed. Results: the mean activity/rest times of women in the experimental and comparison groups were similar. The mean percentages of total load of 6-sulfatoxymelatonin during the day and night were similar (p=0.09). At 24 hours, the experimental group presented a significantly lower mean percentage of total load compared to the comparison group (p=0.04). Conclusions: women who stayed in the room with long-wavelength artificial light showed no difference in activity/rest and 6-sulfatoxymelatonin levels in the early postpartum period.

RESUMO Objetivos: comparar os parâmetros do ciclo de atividade/descanso de puérperas lactantes no início do pós-parto sob regime de iluminação com raios de comprimento de onda longo controlado e descontrolado. Métodos: estudo quase-experimental com lactantes e seus bebês em alojamento conjunto, São Paulo, Brasil. Os participantes foram alocados para grupos experimental (intervenção) ou de comparação. A intervenção consistia na exposição em uma sala controlada com iluminação artificial de raios de comprimento de onda longo à noite. Foram analisados os horários de atividade/repouso (horas) e nível de 6-sulfatoximelatonina em 24 horas. Resultados: a atividade média e os tempos de repouso das mulheres nos grupos experimental e comparação foram semelhantes. Os percentuais médios de volume total de 6-sulfatoximelatonina durante o dia e a noite foram semelhantes (p=0,09). Em 24 horas, o grupo experimental apresentou percentual médio significantemente menor de volume total em relação ao grupo comparação (p=0,04). Conclusões: as mulheres que permaneceram no quarto com luz artificial de comprimento de onda longa não apresentaram diferenças nos níveis de atividade/repouso e 6-sulfatoximelatonina no início do período pós-parto.

RESUMEN Objetivos: comparar parámetros del ciclo actividad/descanso en madres lactantes en posparto temprano bajo régimen lumínico de rayos de longitud de onda larga controlado y no controlado. Métodos: estudio cuasiexperimental con madres lactantes y sus bebés, São Paulo, Brasil. Las participantes fueron asignadas a grupos experimental (intervención) y comparación, consistente en exposición en habitación controlada con luz artificial de rayos de longitud de onda larga durante la noche. Se analizaron tiempos de actividad/descanso (horas) y nivel de 6-sulfatoximelatonina a las 24 horas. Resultados: actividad media y tiempos de descanso fueron similares en grupos comparación e intervención. Porcentajes promedio de volumen total de 6-sulfatoximelatonina durante día y noche resultaron similares (p=0,09). A las 24 horas, el grupo intervención presentó porcentaje promedio de volumen total significantemente menor comparado con grupo comparación (p=0,04). Conclusiones: las mujeres expuestas a luz artificial de longitud de onda larga no mostraron diferencias en niveles actividad/descanso y 6-sulfatoximelatonina durante el posparto temprano.

Melatonin deficiency decreases brown adipose tissue acute thermogenic capacity of in rats measured by 18F-FDG PET.

OBJECTIVE: Melatonin has been shown to increase brown adipose tissue (BAT) mass, which can lead to important metabolic effects, such as bodyweight reduction and glycemic improvement. However, BAT mass can only be measured invasively and. The gold standard for non-invasive measurement of BAT activity is positron emission tomography with 2-deoxy-2-[fluorine-18] fluoro-d-glucose (18F-FDG PET). There is no study, to our knowledge, that has evaluated if melatonin influences BAT activity, measured by this imaging technique in animals. METHODS: Three experimental groups of Wistar rats (control, pinealectomy, and pinealectomy replaced with melatonin) had an 18F-FDG PET performed at room temperature and after acute cold exposure. The ratio of increased BAT activity after cold exposure/room temperature was called "acute thermogenic capacity" (ATC) We also measured UCP-1 mRNA expression to correlate with the 18F-FDG PET results. RESULTS: Pinealectomy led to reduced acute thermogenic capacity, compared with the other groups, as well as reduced UCP1 mRNA expression. CONCLUSION: Melatonin deficiency impairs BAT response when exposed to acute cold exposure. These results can lead to future studies of the influence of melatonin on BAT, in animals and humans, without needing an invasive evaluation of BAT.

Sleep parameters assessed by actigraphy in Fabry's disease patients: a proof-of-concept.

BACKGROUND: In a previous study developed by our group, we identified a phase inversion in 6-sulfatoxymelatonin - melatonin metabolite in urine - daily profile in Fabry's disease patients. Since melatonin is an endogenous marker, it could also be accompanied by behavioral changes in sleep-wake cycle, which impairs the overall patient's life quality. OBJECTIVE: In this study, we evaluated sleep-wake cycle in Fabry disease patients. We hypothesized that patients would have increased daytime naps, given our previous results for urinary 6-sulfatoxymelatonin. PATIENTS/METHODS: This was a cross-sectional and case-control study, performed between October 2016 and May 2017. Volunteers recorded activity and rest rhythm by actigraphy and answered Pittsburgh Sleep Quality Index (PSQI). From actigraphy data, we calculated sleep parameters: sleep latency, wake after sleep onset, sleep (WASO) efficiency, awakenings index (PSQI), and the amount and duration of daytime naps. We included 16 Fabry disease patients with biochemical and molecular diagnosis and 10 control individuals matched by age and gender. RESULTS: We did not observe significant differences for any of the parameters analyzed (p > 0.05). However, evaluating the magnitude of the effect, we found that patients dozed, on average, about 42 min longer (d = 0.9 - large effect size) than control group. CONCLUSIONS: This is a preliminary study, a proof-of-concept, and our results indicate that changes in melatonin secretion phase may have behavioral consequences in sleep-wake cycle, with longer duration of daytime naps.

New insights into the function of melatonin and its role in metabolic disturbances.

INTRODUCTION: Melatonin is a pineal hormone that has acquired several unique modes of regulating the physiological effects in mammals due to its characteristic phylogenetic history. While melatonin exhibits immediate nocturnal effects, it also has next-day prospective effects that take place in the absence of this hormone. Besides that, the daily repetition and the annual variation in the duration of its synthesis determine its circadian and seasonal effects that characterize melatonin as a chronobiotic, a molecule that encodes time to the internal environment. Additionally, it presents transgenerational effects that are important for fetal programming, leading to a balanced energy metabolism in the adult life. AREAS COVERED: Physiology, pathophysiology and therapeutic value of melatonin in metabolism and metabolic disorders. EXPERT OPINION: The typical mechanisms of action of melatonin (immediate, prospective, chronobiotic and transgenerational) should be considered to adequately understand its physiological effects on the regulation of metabolism in humans and, as a result, to understand the metabolic pathophysiological consequences caused by its synthesis and/or signaling disturbances. That points to the importance of a broader understanding of melatonin actions, besides the classical endocrinological point of view, that would allow the clinician/research to proper interpret its role in health maintenance.

Melatonin Increases Brown Adipose Tissue Volume and Activity in Patients With Melatonin Deficiency: A Proof-of-Concept Study.

Melatonin, a pineal hormone synthesized at night, is critical for the synchronization of circadian and seasonal rhythms, being a key regulator of energy metabolism in many animal species. Although studies in humans are lacking, several reports, mainly on hibernating animals, demonstrated that melatonin supplementation and a short photoperiod increase brown adipose tissue (BAT) mass. The present proof-of-concept study is the first, to our knowledge, to evaluate BAT in patients with melatonin deficiency (radiotherapy or surgical removal of pineal gland) before and after daily melatonin (3 mg) replacement for 3 months. All four studied patients presented increased BAT volume and activity measured by positron emission tomography-MRI. We also found an improvement in total cholesterol and triglyceride blood levels without significant effects on body weight, liver fat, and HDL and LDL levels. Albeit not statistically significant, fasting insulin levels and HOMA of insulin resistance decreased in all four patients. The present results show that oral melatonin replacement increases BAT volume and activity and improves blood lipid levels in patients with melatonin deficiency, suggesting that melatonin is a possible BAT activator. Future studies are warranted because hypomelatoninemia is usually present in aging and appears as a result of light-at-night exposure and/or the use of ß-blocker drugs.