Circadian gene methylation in rotating-shift nurses: a cross-sectional study

Early-to-mid pregnancy sleep and circadian markers in relation to birth outcomes: An epigenetics pilot study

Maternal sleep and circadian health during pregnancy are emerging as important predictors of pregnancy outcomes, but examination of potential epigenetic mechanisms is rare. We investigated links between maternal leukocyte DNA methylation of circadian genes and birth outcomes within a pregnancy cohort. Women (n = 96) completed a questionnaire and provided a blood sample at least once during early-to-mid pregnancy (average gestation weeks = 14.2). Leukocyte DNA was isolated and DNA methylation (average percent of methylation) at multiple CpG sites within BMAL1, PER1, and MTNR1B genes were quantified by pyrosequencing. Birth outcomes including gestational age at delivery, birthweight, and head circumference were abstracted from medical charts. Linear regression analyses were run between each CpG site with birth outcomes, adjusting for important confounders. Sleep duration and timing were assessed as secondary exposures. Higher methylation of a CpG site in PER1 was associated with smaller log-transformed head circumference (β=-0.02 with 95% CI -0.02 to 0.01; P, trend = 0.04). Higher methylation of MTNR1B (averaged across sites) was associated with lower log-transformed birthweight (-0.08 with 95% CI -0.16 to -0.01; P, trend = 0.0495). In addition, longer sleep duration was associated with higher birthweight (0.10 with 95% CI 0.02 to 0.18 comparing > 9 h to < 8 h; P, trend = 0.04). This pilot investigation revealed that higher methylation of PER1 and MTNR1B genes, and sleep duration measured in early-to-mid pregnancy were related to birth outcomes.

Absence of the influence of the APOE gene on the incidence of type 2 diabetes mellitus in a cohort of workers: Effect of diet and shift work

BACKGROUND

APOE gene encoded a multifunctional protein in lipid metabolism, also associated with inflammatory markers. Type 2 diabetes (T2D) is a complex metabolic disease related to increased blood glucose, triglycerides and VLDL and associated with different dyslipidaemias. The aim of this study was to analyze whether the APOE genotype could determining the risk of developing T2D in a large cohort of workers.

MATERIAL AND METHODS

Data from the Aragon Workers Health Study (AWHS) (n=4895) were used to investigate the relationship between glycemic levels and APOE genotype. All patients in the AWHS cohort had their blood drawn after an overnight fast and laboratory tests were performed on the same day as the blood drawn. Dietary and physical assessment was assessed by face-to-face interview. APOE genotype was determined by the Sanger sequencing method.

RESULTS

The relationship between APOE genotype and glycemic profile showed that glucose, Hb1Ac, insulin and HOMA levels did not seem to be associated with the APOE genotype (p=0.563, p=0.605, p=0.333 and p=0.276, respectively). In addition, the T2D prevalence did not show an association with the APOE genotype (p=0.354). Along the same lines, blood glucose levels and T2D prevalence did not show association with the APOE allele. Shift work had some effect on the glycaemic profile, showing that night shift workers have significantly lower levels of glucose, insulin and HOMA (p<0.001). However, the APOE genotype did not show difference in the concentration of glycaemic parameters adjusting by sex, age and BMI, work shift and dietary parameters.

CONCLUSION

Glycemic profile and T2D prevalence did not show any significant association with the APOE genotype. Besides, individuals, who worked in non-rotating night shift showed significantly lower glycemic levels, while workers in the morning-afternoon-night shift showed significantly higher values.

Melatonin: A Potential Regulator of DNA Methylation

The pineal gland-derived indoleamine hormone, melatonin, regulates multiple cellular processes, ranging from chronobiology, proliferation, apoptosis, and oxidative damage to pigmentation, immune regulation, and mitochondrial metabolism. While melatonin is best known as a master regulator of the circadian rhythm, previous studies also have revealed connections between circadian cycle disruption and genomic instability, including epigenetic changes in the pattern of DNA methylation. For example, melatonin secretion is associated with differential circadian gene methylation in night shift workers and the regulation of genomic methylation during embryonic development, and there is accumulating evidence that melatonin can modify DNA methylation. Since the latter one impacts cancer initiation, and also, non-malignant diseases development, and that targeting DNA methylation has become a novel intervention target in clinical therapy, this review discusses the potential role of melatonin as an under-investigated candidate epigenetic regulator, namely by modulating DNA methylation via changes in mRNA and the protein expression of DNA methyltransferases (DNMTs) and ten-eleven translocation (TET) proteins. Furthermore, since melatonin may impact changes in the DNA methylation pattern, the authors of the review suggest its possible use in combination therapy with epigenetic drugs as a new anticancer strategy.

Association between night shift work and methylation of a subset of immune-related genes

Introduction

Night shift (NS) work has been associated with an increased risk of different conditions characterized by altered inflammatory and immune responses, such as cardio-metabolic and infectious diseases, cancer, and obesity. Epigenetic modifications, such as DNA methylation, might mirror alterations in biological processes that are influenced by NS work.

Methods

The present study was conducted on 94 healthy female workers with different working schedules and aimed at identifying whether NS was associated with plasmatic concentrations of the inflammatory proteins NLRP3 and TNF-alpha, as well as with DNA methylation levels of ten human endogenous retroviral (HERV) sequences, and nine genes selected for their role in immune and inflammatory processes. We also explored the possible role of the body mass index (BMI) as an additional susceptibility factor that might influence the effects of NS work on the tested epigenetic modifications.

Results and discussion

We observed a positive association between NS and NLRP3 levels (p-value 0.0379). Moreover, NS workers retained different methylation levels for ERVFRD-1 (p-value = 0.0274), HERV-L (p-value = 0.0377), and HERV-P (p-value = 0.0140) elements, and for BIRC2 (p-value = 0.0460), FLRT3 (p-value = 0.0422), MIG6 (p-value = 0.0085), and SIRT1 (p-value = 0.0497) genes. We also observed that the BMI modified the relationship between NS and the methylation of ERVE, HERV-L, and ERVW-1 elements. Overall, our results suggest that HERV methylation could pose as a promising biomolecular sensor to monitor not only the effect of NS work but also the cumulative effect of multiple stressors.

Shift work with and without night shifts and breast cancer risk in a cohort study from Finland

OBJECTIVES

To examine the association of shift work with and without night work with breast cancer among women in the public sector.

METHODS

Using the Finnish Public Sector cohort study (N=33 359, mean age of 40.6 years at baseline), we investigated the associations of shift work and potential confounders with incident breast cancer. Exposure to permanent day work or shift work was defined from first two consecutive surveys from 2000, 2004, 2008 or 2012 and past information on exposure in a subcohort (n=20 786). Incident cases of breast cancer (n=1129) were retrieved from the National Cancer Register and the cohort members were followed to the end of 2016. HR and 95% CI from Cox proportional hazard regression models were calculated.

RESULTS

Shift work with and without night shifts was not overall associated with breast cancer. When stratified according to age, both shift work without nights (HR 2.01, 95% CI 1.12 to 3.60) and shift work with nights (OR 2.05, 95% CI 1.04 to 4.01) were associated with an increased risk after a period of 10 years or more follow-up among women aged 50 years or older, when adjusted for age, socioeconomic status, children, smoking, alcohol and body mass index. In a subgroup with past information on exposure to shift work, the increased risk by longer exposure to shift work was not significant.

CONCLUSIONS

This study provides support for an increased risk of breast cancer among elderly shift workers. However, insufficient information on exposure and intensity of night work may attenuate the risk estimates.

Irregular sleep and cardiometabolic risk: Clinical evidence and mechanisms

Sleep regularity is an essential part of the multidimensional sleep health framework. The phenomenon of irregular sleep patterns is widespread in contemporary lifestyles. This review synthesizes clinical evidence to summarize the measures of sleep regularity and discusses the role of different sleep regularity indicators in developing cardiometabolic diseases (coronary heart disease, hypertension, obesity, and diabetes). Existing literature has proposed several measurements to assess sleep regularity, mainly including the standard deviation (SD) of sleep duration and timing, sleep regularity index (SRI), interdaily stability (IS), and social jetlag (SJL). Evidence on associations between sleep variability and cardiometabolic diseases varies depending on the measure used to characterize variability in sleep. Current studies have identified a robust association between SRI and cardiometabolic diseases. In comparison, the association between other metrics of sleep regularity and cardiometabolic diseases was mixed. Meanwhile, the associations of sleep variability with cardiometabolic diseases differ across the population. SD of sleep characteristics or IS may be more consistently associated with HbA1c in patients with diabetes compared with the general population. The association between SJL and hypertension for patients with diabetes was more accordant than in the general population. Interestingly, the age-stratified association between SJL and metabolic factors was observed in the present studies. Furthermore, the relevant literature was reviewed to generalize the potential mechanisms through which irregular sleep increases cardiometabolic risk, including circadian dysfunction, inflammation, autonomic dysfunction, hypothalamic-pituitary-adrenal (HPA) axis disorder, and gut dysbiosis. Health-related practitioners should give more attention to the role of sleep regularity on human cardiometabolic in the future.

Investigating the relationship between melatonin patterns and methylation in circadian genes among day shift and night shift workers

OBJECTIVES

Mechanisms underlying the carcinogenicity of night shift work remain uncertain. One compelling yet understudied cancer mechanism may involve altered DNA methylation in circadian genes due to melatonin secretion patterns. The objective of this study was to explore the relationship between melatonin secretion patterns and circadian gene methylation among day and night shift workers.

METHODS

Female healthcare employees (n=38 day workers, n=36 night shift workers) for whom we had urinary 6-sulfatoxymelatonin secretion data from a previous study were recontacted. New blood samples were collected and used to measure methylation levels at 1150 CpG loci across 22 circadian genes using the Illumina Infinium MethylationEPIC beadchip. Linear regression was used to examine the association between melatonin (acrophase and mesor) and M values for each CpG site (false discovery rate, q=0.2), while testing for effect modification by shift work status.

RESULTS

Among night shift workers, a higher mesor (24 hours of mean production of melatonin) was associated with increased methylation in the body of RORA (q=0.02) and decreased methylation in the putative promoter region of MTNR1A (q=0.03). Later acrophase (ie, time of peak concentration) was associated with increased methylation in the putative promoter region of MTNR1A (q=0.20) and decreased methylation in the body of PER3 (q=0.20). No associations were identified among day workers.

CONCLUSIONS

In conclusion, patterns in melatonin secretion were associated with differential circadian gene methylation among night shift workers. Melatonin and alteration of DNA methylation in circadian genes may be one pathway towards increased cancer risk, although larger-scale studies examining multiple time points are needed.

DNA methylation of circadian genes and markers of cardiometabolic risk in female hospital workers: An exploratory study

Night shift work has been linked to increased risk of cardiovascular disease (CVD); however, the underlying mechanisms remain unclear. A compelling yet understudied mechanism involves differential DNA methylation of circadian genes. To investigate the relevance of this mechanism, we conducted an exploratory cross-sectional study of 74 female hospital personnel (38 day workers, 36 night shift workers). Sociodemographic, lifestyle, and health characteristics as well as shift work status and history were determined through self-report. Fasting blood samples were collected to measure markers of cardiometabolic risk and DNA was extracted to measure DNA methylation of 1150 cytosine-guanine (CpG) sites across 22 circadian genes. Associations between methylation levels at individual CpG sites (β-values) and markers of cardiometabolic risk were analyzed while considering effect modification by shift work status. The false discovery rate was applied to account for multiple comparisons (q ≤ 0.20). Two CpG sites [cg06758649 (CRY1) and cg06899802 (CSNK1A1)] were differentially associated with waist circumference and body mass index by shift work status, and eight CpG sites [cg26103512 (CSNK1D), cg03941313 (CSNK1E), cg18217763 (CSNK1E), cg16682686 (DEC1), cg12061096 (RORA), cg10133825 (RORA), cg19652148 (RORA), and cg22904654 (RORA)] were differentially associated with LDL cholesterol concentration by shift work status (all q ≤ 0.20). Our findings suggest that the relationship between DNA methylation of circadian genes and cardiometabolic risk differs by day and night shift worker status, which may contribute to mechanisms of increased risk of CVD observed among night shift workers.

Exploring the impact of night shift work on methylation of circadian genes

Night shift work is associated with increased breast cancer risk, but the molecular mechanisms are not well-understood. The objective of this study was to explore the relationship between night shift work parameters (current status, duration/years, and intensity) and methylation in circadian genes as a potential mechanism underlying the carcinogenic effects of night shift work. A cross-sectional study was conducted among 74 female healthcare employees (n = 38 day workers, n = 36 night shift workers). The Illumina Infinium MethylationEPIC beadchip was applied to DNA extracted from blood samples to measure methylation using a candidate gene approach at 1150 CpG loci across 22 circadian genes. Linear regression models were used to examine the association between night shift work parameters and continuous methylation measurements (β-values) for each CpG site. The false-discovery rate (q = 0.2) was used to account for multiple comparisons. Compared to day workers, current night shift workers demonstrated hypermethylation in the 5'UTR region of CSNK1E (q = 0.15). Individuals that worked night shifts for ≥10 years exhibited hypomethylation in the gene body of NR1D1 (q = 0.08) compared to those that worked <10 years. Hypermethylation in the gene body of ARNTL was also apparent in those who worked ≥3 consecutive night shifts a week (q = 0.18). These findings suggest that night shift work is associated with differential methylation in core circadian genes, including CSNK1E, NR1D1 and ARNTL. Future, larger-scale studies with long-term follow-up and detailed night shift work assessment are needed to confirm and expand on these findings.

PER3 polymorphisms and their association with prostate cancer risk in Japanese men

Introduction

Prostate cancer (PCa) is one of the most common cancers affecting men globally. Although PER3 has been suggested as a risk factor for cancer development, there are few reports elucidating the relationship between PER3 and PCa. We investigated the association between PER3 polymorphisms (rs2640908 and VNTR) and susceptibility to PCa in the Japanese population.

Methods

Eighty three patients with PCa and 122 controls participated in this study. We analyzed rs2640908 and VNTR polymorphisms by using PCR-Restriction Fragment Length Polymorphism (PCR-RFLP).

Results

Compared to the C/C genotype with the rs2640908 polymorphism, the T/T (OR: 0.35, 95% CI: 0.15-0.81, P = 0.02) and C/T + T/T (OR: 0.46, 95% CI: 0.24-0.88, P = 0.02) genotypes had a significantly lower risk of PCa. TT (OR: 0.29, 95% CI: 0.10-0.77, P = 0.02) and CT + TT (OR: 0.47, 95% CI: 0.23-0.97, P = 0.04) also had significant protection against PCa in the smoker group. Significantly, we observed an association between smoking and rs2640908 polymorphism in this study. However, no association between the VNTR polymorphisms and PCa was detected.

Conclusions

Our results suggest that PER3 rs2640908 polymorphisms influence an individual's susceptibility to PCa.

Adolescent sleep timing and dietary patterns in relation to DNA methylation of core circadian genes: a pilot study of Mexican youth

Mistimed sleep/wake and eating patterns put shift workers at increased risk for cardiometabolic disease, and epigenetic modification of circadian genes has been proposed as a mechanism. Although not as extreme as shift workers, adolescents often have delayed sleep timing and irregular eating patterns. The aim was to assess whether sleep midpoints - median of bed and wake time - and dietary patterns in adolescents were associated with DNA methylation of circadian genes. The study population included 142 Mexican youth (average age of 14.0 (SD = 2.0) years, 49% male). Average sleep midpoint over weekdays was estimated with actigraphy. Diet was assessed with a semi-quantitative food frequency questionnaire, and three dietary patterns were derived from principal component analysis, a Plant-based & lean proteins pattern, a Meat & starchy pattern, and an Eggs, milk & refined grain pattern. DNA methylation was quantified in blood leukocytes with the Infinium MethylationEPIC BeadChip, and data from 548 CpG sites within 12 circadian genes were examined. Linear regression analyses, adjusted for sex, age, and % monocytes, showed that later sleep timing was associated with higher DNA methylation of several circadian genes, notably with RORB, PER1, CRY2, and NR1D1. Each of the dietary patterns examined was also related to circadian gene DNA methylation, but the Eggs, milk & refined grain pattern ('breakfast' pattern) had the clearest evidence of relationships with circadian genes, with inverse associations (lower DNA methylation) across all 12 genes. Findings suggest that timing-related sleep and eating behaviours among adolescents could result in epigenetic modification of clock genes.

Sleep duration and fragmentation in relation to leukocyte DNA methylation in adolescents

STUDY OBJECTIVES

Sleep deprivation and low sleep quality are widespread among adolescents, and associate with obesity risk. Plausible mediators include diet and physical activity. Another potential interrelated pathway, as yet unexplored in adolescents, could involve epigenetic modification of metabolism genes.

METHODS

In a cohort of 351 Mexico City adolescents (47% male; mean [SD] age = 14 [2] years), 7-day actigraphy was used to assess average sleep duration, sleep fragmentation, and movement index. DNA isolated from blood leukocytes was bisulfite-converted, amplified, and pyrosequenced at four candidate regions. Linear mixed models evaluated sex-stratified associations between sleep characteristics (split into quartiles [Q]) and DNA methylation of each region, adjusted for potential confounders.

RESULTS

Mean sleep duration was 8.5 [0.8] hours for boys and 8.7 [1] hours for girls. There were sex-specific associations between sleep duration and LINE-1 (long interspersed nuclear element) methylation. Boys with longer sleep duration (Q4) had lower LINE-1 methylation than boys in the 3rd quartile reference category, while girls with both longer and shorter sleep duration had higher LINE-1 methylation compared to Q3. Longer sleep duration was associated with higher H19 methylation among girls (comparing highest to third quartile, -0.9% [-2.2, 0.5]; p, trend = 0.047). Sleep fragmentation was inversely associated with peroxisome proliferator-activated receptor alpha (PPARA) methylation among girls (comparing highest to lowest fragmentation quartile, 0.9% [0.1 to 1.8]). Girls also showed an inverse association between sleep fragmentation and hydroxysteroid (11-beta) dehydrogenase 2 (HSD11B2; Q4 to Q1, 0.6% [-1.2%, 0%]).

CONCLUSIONS

Sleep duration and fragmentation in adolescents show sex-specific associations with leukocyte DNA methylation patterns of metabolism genes.

Molecular and epigenetic markers as promising tools to quantify the effect of occupational exposures and the risk of developing non-communicable diseases

Non-communicable diseases (NCDs) are chronic diseases that are by far the leading cause of death in the world. Many occupational hazards, together with social, economic and demographic factors, have been associated to NCDs development. Genetic susceptibility or environmental exposures alone are not usually sufficient to explain the pathogenesis of NCDs, but can be integrated in a more complex scenario that can result in pathological phenotypes. Epigenetics is a crucial component of this scenario, as its changes are related to specific exposures, therefore potentially able to display the effects of environment on the genome, filling the gap between genetic asset and environment in explaining disease development. To date, the most promising biomarkers have been assessed in occupational cohorts as well as in case/control studies and include DNA methylation, histone modifications, microRNA expression, extracellular vesicles, telomere length, and mitochondrial alterations.

A different methylation profile of circadian genes promoter in breast cancer patients according to clinicopathological features

One of the supposed mechanisms that may lead to breast cancer (BC) is an alteration of circadian gene expression and DNA methylation. We undertook an integrated approach to identify methylation pattern of core circadian promoter regions in BC patients with regard to clinical features. We performed a quantitative methylation-specific real-time PCR analysis of a promoter methylation profile in 107 breast tumor and matched non-tumor tissues. A panel of circadian genes CLOCK, BMAL1, PERIOD (PER1, 2, 3), CRYPTOCHROME (CRY1, 2) and TIMELESS as well as their association with clinicopathological characteristics were included in the analysis. Three out of the eight analyzed genes exhibited marked hypermethylation (PER1, 2, 3), whereas CLOCK, BMAL1, CRY2 showed significantly lower promoter CpG methylation in the BC tissues when compared to the non-tumor tissues. Among variously methylated genes we found an association between the elevated methylation level of PERs promoter region and molecular subtypes, histological subtypes and tumor grading of BC. Methylation status may be associated with a gene expression level of circadian genes in BC patients. An aberrant methylation pattern in circadian genes in BC may provide information that could be used as novel biomarkers in clinics and molecular epidemiology as well as play an important role in BC etiology.

Impact of shift work on the diurnal cortisol rhythm: a one-year longitudinal study in junior physicians

Background

Cumulative epidemiological evidence suggests that shift work exerts harmful effects on human health. However, the physiological mechanisms are not well understood. This study aimed to examine the impact of shift work on the dysregulation of the hypothalamic-pituitary-adrenal axis, i.e. diurnal cortisol rhythm.

Methods

Seventy physicians with a mean age 30 years participated in this one-year longitudinal study. Working schedules, either shift work or regular schedules with day shift, were assessed at baseline. Salivary cortisol samples were collected on two consecutive regular working days, four times a day (including waking, + 4 h, + 8 h, and + 16 h), at both baseline and the one-year follow-up. The diurnal cortisol decline (slope) and total cortisol concentration (area under the curve, AUC) were calculated.

Results

After adjusting for cortisol secretion at baseline and numerous covariates, shift work at baseline significantly predicted a steeper slope (p < 0.01) and a larger AUC (p < 0.05) of diurnal cortisol rhythm at follow-up in this sample of physicians. In particular, waking cortisol at follow-up was significantly higher among those engaged in shift work than day shift (p < 0.01).

Conclusions

Our findings support the notion that shift work changes the diurnal cortisol pattern, and is predictive of increased cortisol secretion consequently in junior physicians.