High social jetlag is correlated with nocturnal inhibition of melatonin production among night workers

Night work can lead to social jetlag (SJL), which can be briefly defined as the difference between social and biological time. In this sense, SJL has been viewed as a proxy for circadian misalignment. Studies have suggested that SJL may modify physiological processes, such as blood pressure, glucose metabolism, cortisol, and melatonin production. Therefore, we aimed to verify the correlation between SJL and nocturnal inhibition of melatonin production estimated by the concentration of its urinary metabolite (6-sulfatoximelatonin). The study included day workers (n = 9) and night workers (n = 13) from a public maternity hospital in the city of São Paulo. A questionnaire was used to obtain sociodemographic data, life habits, working conditions, and the Munich Chronotype Questionnaire (MCTQ_shift) was used to assess chronotype. Urine was collected on workdays and days off to estimate the concentration of 6-sulfatoximelatonin (aMT6s), quantified by the ELISA method. We found SJL 13 times higher for night workers (10.6 h) than day workers (0.8 h). The excretion of aMT6s in night workers was statistically different on workdays as opposed to days off, with the lowest excretion on workdays, as expected. SJL was correlated with the aMT6s's delta between the night off and night on among night workers, indicating that the higher is the SJL, the lower is the melatonin production. As expected, social jetlag was higher among night workers, compared to day workers. Moreover, our findings showed that melatonin concentration is directly correlated with SJL.

0183 Social Jet Lag and Chronotype: Implications for Activity and Rest Rhythm and Light Exposure

Introduction

Social jet lag is associated with contemporary lifestyle with harmful impacts on health, predisposing individuals to obesity, diabetes, cardiovascular diseases and cognitive impairment. Knowing that this condition is influenced by chronotype and that these are reflected in rhythmicity markers, a better understating of mechanisms and factors related to this condition are helpful to raise awareness to the society, to prevent and treat its consequences. Our goal was to evaluate if chronotype has a moderating effect on social jet lag, investigate if activity-rest rhythm could be affected by social jet lag and whether it could be related to nighttime light exposure.

Methods

13 subjects (10 women) aged between 23 and 59 years answered Morningness-Eveningness Questionnaire and record activity and rest rhythm by actimetry.

Results

We observed that chronotype is a predictor of social jet lag (p < 0.05) and eveningness leads to greater social jet lag. Sleep duration and time of sleep offset were higher on free days (p < 0.05) and, as expected, higher activity at night was related to greater social jet lag (p < 0.05). We did not find relation between level and time of exposure to light at night and social jet lag (p ≥ 0.05). None of these differences were chronotype-dependent.

Conclusion

Our work was one of the first that addressed the relationship between social jet lag and a rhythmicity marker, the activity-rest rhythm. We also demonstrated the importance of a better understanding of the evening types, that are more affected by social obligations.

Support

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES), Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) e Associação Fundo de Incentivo à Pesquisa (AFIP).

Melatonin profiles during the third trimester of pregnancy and health status in the offspring among day and night workers: A case series

Successful pregnancy requires adaptation in maternal physiology. During intrauterine life the mother's circadian timing system supports successful birth and postnatal development. Maternal melatonin is important to transmit circadian timing and day length to the fetus. This study aims to describe the third trimester of pregnancy among day (n = 5) and night (n = 3) workers by assessing their melatonin levels in a natural environment. Additionally, we describe the worker's metabolic profiles and compare the health status of the newborns between groups of day and night working mothers. Our results indicate an occurrence of assisted delivery (cesarean and forceps) among night workers. Moreover, the newborns of night workers showed lower Apgar index and breastfeeding difficulty indicating a worse condition to deal with the immediate outside the womb environment. Additionally, there was lower night-time melatonin production among pregnant night workers compared to day workers. These findings may be related to light-induced suppression of melatonin that occurs during night work. We conclude that night work and consequent exposure to light at unconventional times might compromise the success of pregnancy and the health of the newborn. Further studies need to be carried out to monitor pregnancy and newborn health in pregnant night workers.

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There was lower night-time melatonin production among pregnant night workers compared to day workers.

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Night work might compromise the success of pregnancy.

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Night work during pregnancy might compromise the health of the newborn.

Molecular basis of growth hormone daily mRNA and protein synthesis in rats

AIMS

Daily and seasonal rhythms coordinate the endocrine and metabolic functions. The pituitary gland is the master regulator of several endocrine activities, and its function is classically regulated by endocrine signals from its target glands as well as from the hypothalamus. The growth hormone (GH) produced and secreted by the anterior pituitary presents a pulsatile secretion throughout the 24-hour cycle. However, the molecular mechanisms regulating the daily pattern of GH secretion are still unclear. Herein we investigated whether circadian GH mRNA and protein synthesis is modulated by acute adjustments in the stability and expression of GH mRNA.

MAIN METHODS

GH mRNA and protein content were evaluated by real-time PCR and Western blotting, respectively, in pituitary gland of rats euthanized every 3 h during a 24-h period at the Zeitgeber times (ZT3 to ZT24). The GH mRNA poly(A) tail length was determined by RACE-PAT assay.

KEY FINDINGS

We identified two main peaks of GH mRNA level in the pituitary gland of rats; one in the middle of the light-cycle and another in the middle of the dark-cycle. The latter was associated with an increase in pituitary GH protein content. Interestingly, an increment in the poly(A) tail length of the GH transcript was observed in association to reduced migration rate of the GH transcript and increased mRNA content in the dark-cycle period.

SIGNIFICANCE

Our findings provide evidence that changes in the GH mRNA poly(A) length may underlie the circadian pattern of GH mRNA and protein levels in the pituitary gland of rats.

Daily differential expression of melatonin-related genes and clock genes in rat cumulus-oocyte complex: changes after pinealectomy

This study investigated the maturational stage (immature and mature ovaries) differences of mRNA expression of melatonin-forming enzymes (Aanat and Asmt), melatonin membrane receptors (Mt1 and Mt2) and putative nuclear (Rorα) receptors, and clock genes (Clock, Bmal1, Per1, Per2, Cry1, Cry2) in cumulus-oocyte complexes (COC) from weaning Wistar rats. We also examined the effects of pinealectomy and of melatonin pharmacological replacement on the daily expression of these genes in COC. qRT-PCR analysis revealed that in oocytes, the mRNA expression of Asmt, Mt2, Clock, Bmal1, Per2, and Cry1 were higher (P < 0.05) in immature ovaries than in the mature ones. In cumulus cells, the same pattern of mRNA expression for Asmt, Aanat, Rorα, Clock, Per1, Cry1, and Cry2 genes was observed. In oocytes, pinealectomy altered the daily mRNA expression profiles of Asmt, Mt1, Mt2, Clock, Per1, Cry1, and Cry2 genes. In cumulus cells, removal of the pineal altered the mRNA expression profiles of Mt1, Mt2, Rorα, Aanat, Asmt, Clock, Bmal1, Per2, Cry1, and Cry2 genes. Melatonin treatment partially or completely re-established the daily mRNA expression profiles of most genes studied. The mRNA expression of melatonin-related genes and clock genes in rat COC varies with the maturational stage of the meiotic cellular cycle in addition to the hour of the day. This suggests that melatonin might act differentially in accordance with the maturational stage of cumulus/oocyte complex. In addition, it seems that circulating pineal melatonin is very important in the design of the daily profile of mRNA expression of COC clock genes and genes related to melatonin synthesis and action.

Environmental control of biological rhythms: effects on development, fertility and metabolism

Internal temporal organisation properly synchronised to the environment is crucial for health maintenance. This organisation is provided at the cellular level by the molecular clock, a macromolecular transcription-based oscillator formed by the clock and the clock-controlled genes that is present in both central and peripheral tissues. In mammals, melanopsin in light-sensitive retinal ganglion cells plays a considerable role in the synchronisation of the circadian timing system to the daily light/dark cycle. Melatonin, a hormone synthesised in the pineal gland exclusively at night and an output of the central clock, has a fundamental role in regulating/timing several physiological functions, including glucose homeostasis, insulin secretion and energy metabolism. As such, metabolism is severely impaired after a reduction in melatonin production. Furthermore, light pollution during the night and shift work schedules can abrogate melatonin synthesis and impair homeostasis. Chronodisruption during pregnancy has deleterious effects on the health of progeny, including metabolic, cardiovascular and cognitive dysfunction. Developmental programming by steroids or steroid-mimetic compounds also produces internal circadian disorganisation that may be a significant factor in the aetiology of fertility disorders such as polycystic ovary syndrome. Thus, both early and late in life, pernicious alterations of the endogenous temporal order by environmental factors can disrupt the homeostatic function of the circadian timing system, leading to pathophysiology and/or disease.

Melatonin, energy metabolism, and obesity: a review

Melatonin is an old and ubiquitous molecule in nature showing multiple mechanisms of action and functions in practically every living organism. In mammals, pineal melatonin functions as a hormone and a chronobiotic, playing a major role in the regulation of the circadian temporal internal order. The anti-obesogen and the weight-reducing effects of melatonin depend on several mechanisms and actions. Experimental evidence demonstrates that melatonin is necessary for the proper synthesis, secretion, and action of insulin. Melatonin acts by regulating GLUT4 expression and/or triggering, via its G-protein-coupled membrane receptors, the phosphorylation of the insulin receptor and its intracellular substrates mobilizing the insulin-signaling pathway. Melatonin is a powerful chronobiotic being responsible, in part, by the daily distribution of metabolic processes so that the activity/feeding phase of the day is associated with high insulin sensitivity, and the rest/fasting is synchronized to the insulin-resistant metabolic phase of the day. Furthermore, melatonin is responsible for the establishment of an adequate energy balance mainly by regulating energy flow to and from the stores and directly regulating the energy expenditure through the activation of brown adipose tissue and participating in the browning process of white adipose tissue. The reduction in melatonin production, as during aging, shift-work or illuminated environments during the night, induces insulin resistance, glucose intolerance, sleep disturbance, and metabolic circadian disorganization characterizing a state of chronodisruption leading to obesity. The available evidence supports the suggestion that melatonin replacement therapy might contribute to restore a more healthy state of the organism.

Effects of melatonin on DNA damage induced by cyclophosphamide in rats

The antioxidant and free radical scavenger properties of melatonin have been well described in the literature. In this study, our objective was to determine the protective effect of the pineal gland hormone against the DNA damage induced by cyclophosphamide (CP), an anti-tumor agent that is widely applied in clinical practice. DNA damage was induced in rats by a single intraperitoneal injection of CP (20 or 50 mg/kg). Animals received melatonin during the dark period for 15 days (1 mg/kg in the drinking water). Rat bone marrow cells were used for the determination of chromosomal aberrations and of formamidopyrimidine DNA glycosylase enzyme (Fpg)-sensitive sites by the comet technique and of Xpf mRNA expression by qRT-PCR. The number (mean ± SE) of chromosomal aberrations in pinealectomized (PINX) animals treated with melatonin and CP (2.50 ± 0.50/100 cells) was lower than that obtained for PINX animals injected with CP (12 ± 1.8/100 cells), thus showing a reduction of 85.8% in the number of chromosomal aberrations. This melatonin-mediated protection was also observed when oxidative lesions were analyzed by the Fpg-sensitive assay, both 24 and 48 h after CP administration. The expression of Xpf mRNA, which is involved in the DNA nucleotide excision repair machinery, was up-regulated by melatonin. The results indicate that melatonin is able to protect bone marrow cells by completely blocking CP-induced chromosome aberrations. Therefore, melatonin administration could be an alternative and effective treatment during chemotherapy.

197 EXPRESSION OF MELATONIN-RELATED GENES IN RAT CUMULUS–OOCYTE COMPLEXES

Melatonin is a hormone usually associated with the modulation of circadian rhythms and the regulation of seasonal reproductive function. There is evidence that melatonin acts directly on the regulation of ovary function. The mRNA expression of melatonin membrane receptors genes was detected in mammalian and non-mammalian ovaries. In spite of melatonin receptors and Asmt (limiting enzyme in melatonin biosynthesis) genes being present in cattle cumulus–oocyte complexes (COC), no information regarding rat COC has been reported. The aim of this study was to investigate the expression of melatonin receptor (Mt2) and melatonin synthesis enzyme (Asmt) genes at different meiotic cell cycle stages in COC from 27-day-old female rats. All the procedures involving animals were approved by the Animal Care Committee of the Institute of Biomedical Sciences. To obtain germinal vesicle (GV) immature COC from ovarian follicles, rats were treated with 20 IU equine chorionic gonadotropin (eCG) for induction of follicular development and killed by euthanasia 48 h later. To obtain COC at MII oocyte stage from oviducts, rats were injected with 20 IU of eCG and 48 h later with 20 IU of human chorionic gonadotropin (hCG), and then killed after 14 to 16 h. The oocytes in COC were separated from their cumulus cells by repeated pipetting through a narrow-bore pipette in culture medium. Oocytes and cumulus cells total RNA were isolated using a Trizol reagent (Invitrogen Corp., Carlsbad, CA, USA). Pools of 80 COC per cDNA sample were used. Quantitative real-time PCR (qRT-PCR) was performed (7500 Real-Time PCR System; Applied Biosystems Inc., Foster City, CA, USA) with 25-µL reactions containing 2 µL of cDNA (10 ng µL–1), SYBR green (Power SYBR Green; Applied Biosystems Inc.), and 400 nM specific intron-spanning primers. A set of 10-fold serial dilutions of each internal standard (102 to 106 copies/2 µL) was used to generate a standard curve. Transcript numbers were determined by the system software and normalized using the geometric mean calculated from the reference genes: Actb and Rpl37a. All the results were plotted as the mean ± SEM, and 4 replicates were performed. Unpaired t-test was used to evaluate the cell type (oocyte v. cumulus cells) differences. The qRT-PCR analyses revealed the presence of transcripts of the Mt2 gene only in oocytes from immature (GV) and mature (MII) COC. At both maturational stages, the copy numbers for Asmt in oocytes were significantly higher than in cumulus cells. The results confirm the presence of the Asmt gene in rat COC and suggest the possible involvement of these cells on melatonin biosynthesis. The presence of Mt2 transcript in immature and mature oocytes also suggests the potentially important role of melatonin in regulating the rat meiotic cellular cycle. Research supported by FAPESP.

Is there enough information to calculate the financial benefits of ergonomics projects?

Many authors studied work situations and, mainly, ergonomics projects concerning the financial benefit point of view. At the same time seems to be little information available concerning these financial benefits in manufacturing companies' processes. The aim of this article is to identify if there enough information available within a company to quantify the financial benefits of an ergonomic project. The study was applied on two manufacturing companies, one in Brazil and other in Portugal. A literature review based checklist and a manager interview was applied on each company in order to identify if the information was available and how were been used. The two companies have revealed a good quantity of available information regarding ergonomics benefit calculation. The interviews showed that managers are not aware of the financial savings possibility with investments in ergonomics projects.