Gene-Environment Interactions of Circadian-Related Genes for Cardiometabolic Traits

The association between breakfast frequency and diabetes incidence in middle-aged women: Results from the MTC study

BACKGROUND AND AIMS

Breakfast consumption could have a synchronizer role in chronobiological functions. Across observational studies, the assessment of breakfast frequency consumption is heterogeneous, therefore consensus on the relation between of weekly frequency of breakfast consumption and the risk of diabetes is unclear. We examined the relation between weekly breakfast frequency consumption and the incidence of diabetes in middle-age women.

METHODS AND RESULTS

Since baseline (2006-2008) we prospectively followed 71,373 women from the Mexican Teachers' Cohort. Participants were classified according to breakfast consumption frequency of 0, 1-3, 4-6, or 7 days/week. Diabetes was identified by self-report and clinical-administrative databases. We used Cox proportional hazards multivariable models to estimate hazard ratios (HR) and 95% confidence intervals (CI) for breakfast frequency and diabetes adjusting for covariates. Stratified analyses were performed for age, birth weight, ethnicity, and physical activity. We identified 3613 new diabetes cases between baseline and 2014. The prevalence of daily breakfast consumers was 25%. The median follow-up was 2.2 years, interquartile range 1.8-3.8 years. Relative to women who skipped breakfast, those who consumed breakfast every day had a 12% lower risk of diabetes (multivariable HR = 0.88; 95% CI 0.78, 0.99; p-trend = 0.0018). One additional day per week of breakfast was associated with a lower risk of diabetes (HR = 0.98; 95% CI 0.97, 0.99). In stratified analysis, the observed inverse relation appeared to be stronger in women aged ≥40 years and in indigenous women.

CONCLUSIONS

Breakfast frequency was inversely associated with the incidence of diabetes independently of lifestyle factors. Regular breakfast consumption may be a potential component of diabetes prevention.

Association Between Accelerometer-Measured Irregular Sleep Duration and Type 2 Diabetes Risk: A Prospective Cohort Study in the UK Biobank

OBJECTIVE

To evaluate the association between irregular sleep duration and incident diabetes in a U.K. population over 7 years of follow-up.

RESEARCH DESIGN AND METHODS

Among 84,421 UK Biobank participants (mean age 62 years) who were free of diabetes at the time of providing accelerometer data in 2013-2015 and prospectively followed until May 2022, sleep duration variability was quantified by the within-person SD of 7-night accelerometer-measured sleep duration. We used Cox proportional hazard models to estimate hazard ratios (HRs) for incident diabetes (identified from medical records, death register, and/or self-reported diagnosis) according to categories of sleep duration SD.

RESULTS

There were 2,058 incident diabetes cases over 622,080 person-years of follow-up. Compared with sleep duration SD ≤ 30 min, the HR (95% CI) was 1.15 (0.99, 1.33) for 31-45 min, 1.28 (1.10, 1.48) for 46-60 min, 1.54 (1.32, 1.80) for 61-90 min, and 1.59 (1.33, 1.90) for ≥91 min, after adjusting for age, sex, and race. We found a nonlinear relationship (P nonlinearity 0.0002), with individuals with a sleep duration SD of >60 vs. ≤60 min having 34% higher diabetes risk (95% CI 1.22, 1.47). Further adjustment for lifestyle, comorbidities, environmental factors, and adiposity attenuated the association (HR comparing sleep duration SD of >60 vs. ≤60 min: 1.11; 95% CI 1.01, 1.22). The association was stronger among individuals with lower diabetes polygenic risk score (PRS; P interaction ≤ 0.0264) and longer sleep duration (P interaction ≤ 0.0009).

CONCLUSIONS

Irregular sleep duration was associated with higher diabetes risk, particularly in individuals with a lower diabetes PRS and longer sleep duration.

MTNR1B genotype and effects of carbohydrate quantity and dietary glycaemic index on glycaemic response to an oral glucose load: the OmniCarb trial

AIMS/HYPOTHESIS

A type 2 diabetes-risk-increasing variant, MTNR1B (melatonin receptor 1B) rs10830963, regulates the circadian function and may influence the variability in metabolic responses to dietary carbohydrates. We investigated whether the effects of carbohydrate quantity and dietary glycaemic index (GI) on glycaemic response during OGTTs varied by the risk G allele of MTNR1B-rs10830963.

METHODS

This study included participants (n=150) of a randomised crossover-controlled feeding trial of four diets with high/low GI levels and high/low carbohydrate content for 5 weeks. The MTNR1B-rs10830963 (C/G) variant was genotyped. Glucose response during 2 h OGTT was measured at baseline and the end of each diet intervention.

RESULTS

Among the four study diets, carrying the risk G allele (CG/GG vs CC genotype) of MTNR1B-rs10830963 was associated with the largest AUC of glucose during 2 h OGTT after consuming a high-carbohydrate/high-GI diet (β 134.32 [SE 45.69] mmol/l × min; p=0.004). The risk G-allele carriers showed greater increment of glucose during 0-60 min (β 1.26 [0.47] mmol/l; p=0.008) or 0-90 min (β 1.10 [0.50] mmol/l; p=0.028) after the high-carbohydrate/high-GI diet intervention, but not after consuming the other three diets. At high carbohydrate content, reducing GI levels decreased 60 min post-OGTT glucose (mean -0.67 [95% CI: -1.18, -0.17] mmol/l) and the increment of glucose during 0-60 min (mean -1.00 [95% CI: -1.67, -0.33] mmol/l) and 0-90 min, particularly in the risk G-allele carriers (pinteraction <0.05 for all).

CONCLUSIONS/INTERPRETATION

Our study shows that carrying the risk G allele of MTNR1B-rs10830963 is associated with greater glycaemic responses after consuming a diet with high carbohydrates and high GI levels. Reducing GI in a high-carbohydrate diet may decrease post-OGTT glucose concentrations among the risk G-allele carriers.

Dietary carbohydrate types, genetic predisposition, and risk of adult-onset asthma: A longitudinal cohort study

We aimed to investigate the longitudinal associations among carbohydrate intake types, genetic predisposition, and risk adult onset asthma (AOA). A dataset of 96,487 participants from UK Biobank was included with 1830 cases of incident AOA during an average follow-up of 9.68 years. Participants with the highest intake of total sugar, free sugar, and fiber intake, as compared to those with the lowest intake of total sugar, free sugar, and fiber intake, showed a 17 % and 22 % increased risk of incident AOA, and a 16 % decreased risk of AOA, respectively. Substitution of 5 % energy from free sugars with 5 % energy from non-free sugars was associated with a significantly lower risk of AOA (Hazard Ratio [HR] = 0.93, 95 % Confidence Interval [CI]: 0.88, 0.99). Participants with high genetic risk and the highest intake of free sugar showed a 112 % (HR = 2.12, 95%CI: 1.68, 2.68) increased risk of incident AOA. Participants with low genetic risk and highest intake of fiber showed a 50 % (HR = 0.50, 95%CI: 0.39, 0.64) reduced risk of AOA. This study highlights the critical role of carbohydrate types in AOA prevention, with an emphasis on reduced free sugar, moderate non-free sugar, and increased fiber intake.

A systematic review of variations in circadian rhythm genes and type 2 diabetes

BACKGROUND

Type 2 diabetes is a chronic disease that has severe individual and societal consequences, which is forecast to worsen in the future. A new field of investigation is variations in circadian rhythm genes, in conjunction with diet and sleep variables, associations with, and effects on, type 2 diabetes development.

OBJECTIVE

This systematic review aimed to analyse all current literature regarding circadian rhythm gene variations and type 2 diabetes, and explore their interplay with diet and sleep variables on type 2 diabetes outcomes. This review was registered with PROSPERO (CRD42021259682).

METHODOLOGY

Embase and Pubmed were searched on 6/8/2021/11/8/2021 for studies of all designs, including participants from both sexes, all ethnicities, ages, and geographic locations. Participants with risk alleles/genotypes were compared with the wildtype regarding type 2 diabetes outcomes. Studies risk of bias were scored according to the risk of bias in non-randomised studies - interventions/exposures criteria.

RESULTS

In total, 31 studies were found (association n  =  29/intervention n  =  2) including >600,000 participants from various ethnicities, sexes, and ages. Variations in the melatonin receptor 1B, brain and muscle arnt-like 1 and period circadian regulator (PER) genes were consistently associated with type 2 diabetes outcomes.

CONCLUSIONS

Individuals with variations in melatonin receptor 1B, brain and muscle arnt-like 1 and PER may be at higher risk of type 2 diabetes. Further research is needed regarding other circadian rhythm genes. More longitudinal studies and randomised trials are required before clinical recommendations can be made.

Waking Up to the Importance of Sleep in Type 2 Diabetes Management: A Narrative Review

For the first time, the latest American Diabetes Association/European Association for the Study of Diabetes (ADA/EASD) consensus guidelines have incorporated a growing body of evidence linking health outcomes associated with type 2 diabetes to the movement behavior composition over the whole 24-h day. Of particular note, the importance of sleep as a key lifestyle component in the management of type 2 diabetes is promulgated and presented using three key constructs: quantity, quality, and timing (i.e., chronotype). In this narrative review we highlight some of the key evidence justifying the inclusion of sleep in the latest consensus guidelines by examining the associations of quantity, quality, and timing of sleep with measures of glycemia, cardiovascular disease risk, and mortality. We also consider potential mechanisms implicated in the association between sleep and type 2 diabetes and provide practical advice for health care professionals about initiating conversations pertaining to sleep in clinical care. In particular, we emphasize the importance of measuring sleep in a free-living environment and provide a summary of the different methodologies and targets. In summary, although the latest ADA/EASD consensus report highlights sleep as a central component in the management of type 2 diabetes, placing it, for the first time, on a level playing field with other lifestyle behaviors (e.g., physical activity and diet), the evidence base for improving sleep (beyond sleep disorders) in those living with type 2 diabetes is limited. This review should act as a timely reminder to incorporate sleep into clinical consultations, ongoing diabetes education, and future interventions.

Attention to Innate Circadian Rhythm and the Impact of Its Disruption on Diabetes

Novel strategies are required to reduce the risk of developing diabetes and/or clinical outcomes and complications of diabetes. In this regard, the role of the circadian system may be a potential candidate for the prevention of diabetes. We reviewed evidence from animal, clinical, and epidemiological studies linking the circadian system to various aspects of the pathophysiology and clinical outcomes of diabetes. The circadian clock governs genetic, metabolic, hormonal, and behavioral signals in anticipation of cyclic 24-hour events through interactions between a "central clock" in the suprachiasmatic nucleus and "peripheral clocks" in the whole body. Currently, circadian rhythmicity in humans can be subjectively or objectively assessed by measuring melatonin and glucocorticoid levels, core body temperature, peripheral blood, oral mucosa, hair follicles, rest-activity cycles, sleep diaries, and circadian chronotypes. In this review, we summarized various circadian misalignments, such as altered light-dark, sleep-wake, rest-activity, fasting-feeding, shift work, evening chronotype, and social jetlag, as well as mutations in clock genes that could contribute to the development of diabetes and poor glycemic status in patients with diabetes. Targeting critical components of the circadian system could deliver potential candidates for the treatment and prevention of type 2 diabetes mellitus in the future.

Circadian misalignment in obesity: The role for time-restricted feeding

BACKGROUND AND AIMS

The epidemic of obesity is associated with a substantial, complex and escalating burden of disease. Dietary and lifestyle interventions provide the mainstay of management; however, obesity is multifactorial and challenging to address clinically. Disrupted circadian behaviours, including late eating, are associated with obesity. Time-restricted feeding (TRF), the confinement of calorie intake to a temporal 'eating window', has received growing interest as a weight-loss intervention. Benefits are purported to arise from the fasting period and strengthened circadian metabolism. However, the current evidence-base for TRF is small-scale, limited, and there has been little evaluation of circadian schedule. This research aims to enable evidence-based conclusions regarding circadian-aligned TRF as a weight-loss intervention in obesity.

METHODS

A systematic three-tranche search strategy was conducted within PubMed. Included studies were critically evaluated. Search tranches scoped: interventional evidence for TRF; evidence linking meal timing, obesity and metabolic function; and evidence linking circadian function, obesity, and dysmetabolism. Results were summarised in a narrative analysis.

RESULTS

A total of 30 studies were included. From small-scale and short-term evidence, TRF was consistently associated with improved weight, glycaemic and anthropometric outcomes versus baseline or control. Good adherence and safety, and consistency of results between studies, were notable. Earlier ('circadian-aligned') eating was associated with greater diet-induced thermogenesis, and improved weight loss and glycaemic outcomes. Limited evidence suggested meaningful correlations between circadian clock function and obesity/metabolic risk.

CONCLUSIONS

Circadian-aligned TRF may present a promising intervention for weight loss and metabolic benefits in obese/overweight individuals.

Development and validation of a multivariable genotype-informed gestational diabetes prediction algorithm for clinical use in the Mexican population: insights into susceptibility mechanisms

INTRODUCTION

Gestational diabetes mellitus (GDM) is underdiagnosed in Mexico. Early GDM risk stratification through prediction modeling is expected to improve preventative care. We developed a GDM risk assessment model that integrates both genetic and clinical variables.

RESEARCH DESIGN AND METHODS

Data from pregnant Mexican women enrolled in the 'Cuido mi Embarazo' (CME) cohort were used for development (107 cases, 469 controls) and data from the 'Mónica Pretelini Sáenz' Maternal Perinatal Hospital (HMPMPS) cohort were used for external validation (32 cases, 199 controls). A 2-hour oral glucose tolerance test (OGTT) with 75 g glucose performed at 24-28 gestational weeks was used to diagnose GDM. A total of 114 single-nucleotide polymorphisms (SNPs) with reported predictive power were selected for evaluation. Blood samples collected during the OGTT were used for SNP analysis. The CME cohort was randomly divided into training (70% of the cohort) and testing datasets (30% of the cohort). The training dataset was divided into 10 groups, 9 to build the predictive model and 1 for validation. The model was further validated using the testing dataset and the HMPMPS cohort.

RESULTS

Nineteen attributes (14 SNPs and 5 clinical variables) were significantly associated with the outcome; 11 SNPs and 4 clinical variables were included in the GDM prediction regression model and applied to the training dataset. The algorithm was highly predictive, with an area under the curve (AUC) of 0.7507, 79% sensitivity, and 71% specificity and adequately powered to discriminate between cases and controls. On further validation, the training dataset and HMPMPS cohort had AUCs of 0.8256 and 0.8001, respectively.

CONCLUSIONS

We developed a predictive model using both genetic and clinical factors to identify Mexican women at risk of developing GDM. These findings may contribute to a greater understanding of metabolic functions that underlie elevated GDM risk and support personalized patient recommendations.

Association between triglyceride glucose index and sleep disorders: results from the NHANES 2005-2008

BACKGROUND

To determine the association between sleep disorders and Triglyceride glucose index.

METHODS

A cross-sectional analysis of the 2005 to 2008 National Health and Nutrition Examination Survey (NHANES) was performed. The 2005 to 2008 NHANES national household survey for adults ≥ 20 years was examined for the sleep disorders.TyG index: ln [triglyceride (mg/ dL) × fasting blood glucose (mg/dL)/2].Multivariable logistic and linear regression models were used to explore the association between the TyG index and sleep disorders.

RESULTS

A total of 4,029 patients were included. Higher TyG index is significantly associated with elevated sleep disorders in U.S. adults. TyG was moderately correlated with HOMA-IR (Spearman r = 0.51). TyG was associated with higher odds of sleep disorders(adjusted OR [aOR],1.896; 95% CI, 1.260 2.854), Sleep apnea (aOR, 1.559; 95% CI, 0.660 3.683), Insomnia(aOR, 1.914;95% CI, 0.531 6.896), and Restless legs (aOR, 7.759; 95% CI,1.446 41.634).

CONCLUSIONS

In this study, our result shown that population with higher TyG index are significantly more likely to have sleep disorders in U.S. adults.

Nuclear Receptor NR1D1 Regulates Abdominal Aortic Aneurysm Development by Targeting the Mitochondrial Tricarboxylic Acid Cycle Enzyme Aconitase-2

BACKGROUND

Metabolic disorder increases the risk of abdominal aortic aneurysm (AAA). NRs (nuclear receptors) have been increasingly recognized as important regulators of cell metabolism. However, the role of NRs in AAA development remains largely unknown.

METHODS

We analyzed the expression profile of the NR superfamily in AAA tissues and identified NR1D1 (NR subfamily 1 group D member 1) as the most highly upregulated NR in AAA tissues. To examine the role of NR1D1 in AAA formation, we used vascular smooth muscle cell (VSMC)-specific, endothelial cell-specific, and myeloid cell-specific conditional Nr1d1 knockout mice in both AngII (angiotensin II)- and CaPO₄-induced AAA models.

RESULTS

Nr1d1 gene expression exhibited the highest fold change among all 49 NRs in AAA tissues, and NR1D1 protein was upregulated in both human and murine VSMCs from AAA tissues. The knockout of Nr1d1 in VSMCs but not endothelial cells and myeloid cells inhibited AAA formation in both AngII- and CaPO₄-induced AAA models. Mechanistic studies identified ACO2 (aconitase-2), a key enzyme of the mitochondrial tricarboxylic acid cycle, as a direct target trans-repressed by NR1D1 that mediated the regulatory effects of NR1D1 on mitochondrial metabolism. NR1D1 deficiency restored the ACO2 dysregulation and mitochondrial dysfunction at the early stage of AngII infusion before AAA formation. Supplementation with αKG (α-ketoglutarate, a downstream metabolite of ACO2) was beneficial in preventing and treating AAA in mice in a manner that required NR1D1 in VSMCs.

CONCLUSIONS

Our data define a previously unrecognized role of nuclear receptor NR1D1 in AAA pathogenesis and an undescribed NR1D1-ACO2 axis involved in regulating mitochondrial metabolism in VSMCs. It is important that our findings suggest αKG supplementation as an effective therapeutic approach for AAA treatment.

Gene-environment interaction between circadian clock gene polymorphisms and job stress on the risk of sleep disturbances

RATIONALE

Sleep disturbances was associated with numerous adverse health outcomes. Many studies have reported that long-term exposure to job stress can lead to sleep disturbances, which may be influenced by genetic and environmental factors.

OBJECTIVES

This cross-sectional study investigated whether circadian clock gene polymorphisms modulated the influence of job stress on sleep disturbances in a Chinese Han population, which to our best knowledge has not been explored.

METHODS

The Effort-Reward Imbalance (ERI) scale and the Pittsburgh Sleep Quality Index (PSQI) were both used to access job stress and sleep disturbances. The SNaPshot SNP assay was carried out by screening for circadian clock gene polymorphisms in every participant. Interactions associated with sleep disturbances were assessed by linear hierarchical regression analysis and SPSS macros (PROCESS).

RESULTS

Linear hierarchical regression analysis showed that job stress was significantly related to sleep disturbances. Likewise, our study found a significant effect of PER2 rs2304672 polymorphisms on sleep disturbances (p < 0.01), after controlling for confounding factors. In addition, the PER2 rs2304672 genotype modulated the relationship between job stress and sleep disturbances (β = 0.414, p = 0.007). Interestingly, further analysis of the results of the PER2 gene rs2304672 × job stress interaction showed that rs2304672 G-allele carriers had a high-risk effect on sleep disturbances under high job stress.

CONCLUSIONS

Our results suggest that the PER2 rs2304672 polymorphism may modulate the influence of job stress on sleep disturbances. These findings contribute to the field of sleep disturbances prevention and treatment.

Chronotype: A Tool to Screen Eating Habits in Polycystic Ovary Syndrome?

Polycystic ovary syndrome (PCOS) is the most common endocrine disorders in women of reproductive age, whose lifestyle approach is an essential part of the treatment. Recently, chronotype, i.e., a trait that determines individual’s circadian preference in behavioral and biological rhythms, has been reported to play a role in determining nutrition preferences and the risk of developing chronic diseases. Thus, the aim of this study was to investigate if chronotype categories (morning, evening, and neither) could be used as tool to screen eating habits in women with PCOS. In this observational cross-sectional study, we assessed anthropometric measurements, lifestyle habits, chronotype categories, adherence to the Mediterranean Diet, dietary pattern, and metabolic parameters in 112 women with PCOS. Chronotype was classified as morning in 27.7%, evening in 42.9%, and neither in 29.5% of subjects. Women with PCOS with evening chronotype showed significantly higher percentages of grade I (p = 0.003) and grade II obesity (p = 0.001), did less regular exercise (p < 0.001), and most of them were smokers (p < 0.001) compared to those with neither and morning chronotypes. Women with PCOS with evening chronotype were significantly more insulin resistant (Homeostatic Model Assessment of Insulin Resistance (HoMA-IR) cut off > 2.5) than other two chronotypes (p < 0.001). Women with PCOS with evening chronotype had the lowest PREvención con DIetaMEDiterránea (PREDIMED) score, consumed more calories (p < 0.001), total (p < 0.001) and simple carbohydrates (p < 0.001), total fat (p < 0.001) and saturated fatty acids (p < 0.001), polyunsaturated fatty acids (p < 0.001) and n-6 polyunsaturated fatty acids (p < 0.001), and less fiber (p < 0.001) than women with PCOS with other chronotypes. In addition, women with PCOS with evening chronotype consumed less extra virgin olive oil (p = 0.001), legumes (p = 0.038), fish/seafood (p < 0.001), and tree nuts (p = 0.041) than women with PCOS of the other two chronotype categories and less red wine (p < 0.001) and more red/processed meat (p < 0.001) than women with PCOS with morning chronotype. In conclusion, in women with PCOS, evening chronotype has been associated with a most severe insulin resistance and unhealthiest eating habits. Thus, chronotype assessment could be an effective tool to screen the eating habits, and more generally the lifestyle, of women with PCOS.

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.

What do we really know about the safety and efficacy of melatonin for sleep disorders?

Melatonin is a hormonal product of the pineal gland, a fact that is often forgotten. Instead it is promoted as a dietary supplement that will overcome insomnia, as an antioxidant and as a prescription only drug in most countries outside the United States of America and Canada. The aim of this review is to step back and highlight what we know about melatonin following its discovery 60 years ago. What is the role of endogenous melatonin; what does melatonin do to sleep, body temperature, circadian rhythms, the cardiovascular system, reproductive system, endocrine system and metabolism when administered to healthy subjects? When used as a drug/dietary supplement, what safety studies have been conducted? Can we really say melatonin is safe when it has not been systematically studied and many studies show interactions with a wide range of physiological processes? Finally the results of studies investigating the efficacy of melatonin as a drug to alleviate insomnia are critically evaluated. In summary, melatonin is an endogenous pineal gland hormone with specific physiological functions in animals and humans, with its primary role in humans to maintain synchrony of sleep with the day/night cycle. When administered as a drug it affects a wide range of physiological systems and has clinically important drug interactions. With respect to efficacy for treating sleep disorders, melatonin can advance the time of sleep onset but the effect is modest and variable. In children with neurodevelopmental disabilities melatonin appears to have the greatest impact on sleep onset but little effect on sleep efficiency.

The Association between Fasting Glucose and Sugar Sweetened Beverages Intake Is Greater in Latin Americans with a High Polygenic Risk Score for Type 2 Diabetes Mellitus

Chile is one of the largest consumers of sugar-sweetened beverages (SSB) world-wide. However, it is unknown whether the effects from this highly industrialized food will mimic those reported in industrialized countries or whether they will be modified by local lifestyle or population genetics. Our goal is to evaluate the interaction effect between SSB intake and T2D susceptibility on fasting glucose. We calculated a weighted genetic risk score (GRSw) based on 16 T2D risk SNPs in 2828 non-diabetic participants of the MAUCO cohort. SSB intake was categorized in four levels using a food frequency questionnaire. Log-fasting glucose was regressed on SSB and GRSw tertiles while accounting for socio-demography, lifestyle, obesity, and Amerindian ancestry. Fasting glucose increased systematically per unit of GRSw (β = 0.02 ± 0.006, p = 0.00002) and by SSB intake (β[cat4] = 0.04 ± 0.01, p = 0.0001), showing a significant interaction, where the strongest effect was observed in the highest GRSw-tertile and in the highest SSB consumption category (β = 0.05 ± 0.02, p = 0.02). SNP-wise, SSB interacted with additive effects of rs7903146 (TCF7L2) (β = 0.05 ± 0.01, p = 0.002) and with the G/G genotype of rs10830963 (MTNRB1B) (β = 0.19 ± 0.05, p = 0.001). Conclusions: The association between SSB intake and fasting glucose in the Chilean population without diabetes is modified by T2D genetic susceptibility.

Ischemic Stroke and Sleep: The Linking Genetic Factors

This review summarizes the available data about genetic factors which can link ischemic stroke and sleep. Sleep patterns (subjective and objective measures) are characterized by heritability and comprise up to 38-46%. According to Mendelian randomization analysis, genetic liability for short sleep duration and frequent insomnia symptoms is associated with ischemic stroke (predominantly of large artery subtype). The potential genetic links include variants of circadian genes, genes encoding components of neurotransmitter systems, common cardiovascular risk factors, as well as specific genetic factors related to certain sleep disorders.

Type 2 diabetes is associated with the MTNR1B gene, a genetic bridge between circadian rhythm and glucose metabolism, in a Turkish population

Type 2 diabetes (T2D) is a complicated public health problem in Turkey as well as worldwide. Genome-wide approaches have been guiding in very challenging situations, such as the elucidation of genetic variations underlying complex diseases such as T2D. Despite intensive studies worldwide, few studies have determined the genetic susceptibility to T2D in Turkish populations. In this study, we investigated the effect of genes that are strongly associated with T2D in genome-wide association (GWA) studies, including MTNR1B, CDKAL1, THADA, ADAMTS9 and ENPP1, on T2D and its characteristic traits in a Turkish population. In 824 nonobese individuals (454 T2D patients and 370 healthy individuals), prominent variants of these GWA genes were genotyped by real-time PCR using the LightSNiP Genotyping Assay System. The SNP rs1387153 C/T, which is located 28 kb upstream of the MTNR1B gene, was significantly associated with T2D and fasting blood glucose levels (P < 0.05). The intronic SNP rs10830963 C/G in the MTNR1B gene was not associated with T2D, but it was associated with fasting blood glucose, HbA1C and LDL levels (P < 0.05). The other important GWA loci investigated in our study were not found to be associated with T2D or its traits. Only the SNP rs1044498 (A/C variation) in the ENPP1 gene was determined to be related to fasting blood glucose (P < 0.05). Our study suggests, consistent with the literature, that the MTNR1B locus, which has a prominent role in glucose regulation, is associated with T2D development by affecting blood glucose levels in our population.

Genetics of Sleep and Insights into Its Relationship with Obesity

Considerable recent advancements in elucidating the genetic architecture of sleep traits and sleep disorders may provide insight into the relationship between sleep and obesity. Despite the considerable involvement of the circadian clock in sleep and metabolism, few shared genes, including FTO, were implicated in genome-wide association studies (GWASs) of sleep and obesity. Polygenic scores composed of signals from GWASs of sleep traits show largely null associations with obesity, suggesting lead variants are unique to sleep. Modest genome-wide genetic correlations are observed between many sleep traits and obesity and are largest for snoring.Notably, U-shaped positive genetic correlations with body mass index (BMI) exist for both short and long sleep durations. Findings from Mendelian randomization suggest robust causal effects of insomnia on higher BMI and, conversely, of higher BMI on snoring and daytime sleepiness. Bidirectional effects between sleep duration and daytime napping with obesity may also exist. Limited gene-sleep interaction studies suggest that achieving favorable sleep, as part of a healthy lifestyle, may attenuate genetic predisposition to obesity, but whether these improvements produce clinically meaningful reductions in obesity risk remains unclear. Investigations of the genetic link between sleep and obesity for sleep disorders other than insomnia and in populations of non-European ancestry are currently limited. Expected final online publication date for the Annual Review of Nutrition, Volume 41 is September 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Association between MTNR1B polymorphisms and obesity in African American: findings from the Jackson Heart Study

BACKGROUND

Melatonin is a hormone that is secreted at night by the pineal gland. It exerts its function by binding to the MT1 and MT2 receptors, which are encoded by the MTNR1A and MTNR1B genes, respectively. Previous studies reveal that MTNR1B variants are associated with insulin secretion impairments and an increased body mass index (BMI) in individuals of European and Asian ancestries. Obesity is highly prevalent in the US and disproportionately affects African Americans. Here, we hypothesized that common single nucleotide polymorphisms (SNPs) imputed in 1000 Genomes in the MTNR1B gene are associated with adiposity in African American adult men and women and that the association is modified by insomnia.

METHODS

We used an additive genetic model to describe the association between the adiposity traits (BMI and waist circumference) and selected MTNR1B variants in 3,029 Jackson Heart Study participants, with an average age of 55.13 ± 12.84 years, and 62% were women. We regressed the adiposity measures on the estimated allelic or genotypic dosage at every selected SNP and adjusted for age, sex, population stratification, and insomnia. Thirty common SNPs, spanning the MTNR1B gene, with a minor allele frequency ≥ 5%, a call rate ≥ 90%, a Hardy-Weinberg equilibrium p value > 10-6, were available for the analysis.

RESULTS

The allele T of rs76371840 was associated with adiposity (OR = 1.47 [1.13-1.82]; PFDR-adjusted = 0.0499), and the allele A of rs8192552 showed a significant association with waist circumference (β = 0.023 ± 0.007; PFDR-adjusted = 0.0077) after correcting for multiple testing. When insomnia was included in the adiposity analysis model, the following four variants became significantly associated with adiposity: rs6483208; rs4388843; rs4601728; and rs12804291.

CONCLUSIONS

Our data indicate that polymorphisms in the MTNR1B gene are associated with obesity traits in African Americans. To the best of our knowledge, this is the first study to explore the effect of insomnia on the association between the circadian MTNR1B genetic variants and metabolic traits in an African American sample population. We observed that insomnia affected the association between the MTNR1B variants and adiposity.

Genetically Guided Mediterranean Diet for the Personalized Nutritional Management of Type 2 Diabetes Mellitus

The current consensus for the prevention and management of type 2 diabetes mellitus (T2DM) is that high-quality diets and adherence to a healthy lifestyle provide significant health benefits. Remarkably, however, there is little agreement on the proportions of macronutrients in the diet that should be recommended to people suffering from pre-diabetes or T2DM. We herein discuss emerging evidence that underscores the importance of gene-diet interactions in the improvement of glycemic biomarkers in T2DM. We propose that we can achieve better glycemic control in T2DM patients by coupling Mediterranean diets to genetic information as a predictor for optimal diet macronutrient composition in a personalized manner. We provide evidence to support this concept by presenting a case study of a T2DM patient who achieved rapid glycemic control when adhered to a personalized, genetically-guided Mediterranean Diet.

The influence of specific aspects of occupational stress on security guards' health and work ability: detailed extension of a previous study

In our earlier study of security guards, we showed that higher occupational stress was associated with health impairments (metabolic syndrome, diabetes, hypertension, cardiovascular diseases) and work disability. The aim of this study was to further explore the association of specific occupational stressors with health impairments and work disability parameters in 399 Serbian male security guards (aged 25–65 years). Ridge linear regression analysis revealed that, after controlling for age, body mass index, and smoking status, professional stressors including high demands, strictness, conflict/uncertainty, threat avoidance and underload were significant positive predictors of fasting glucose, triglycerides, total and LDL cholesterol, blood pressure, heart rate, Framingham cardiovascular risk score, and temporary work disability. The security profession is in expansion worldwide, and more studies are needed to establish precise health risk predictors, since such data are generally lacking.

Determination of genetic changes of Rev-erb beta and Rev-erb alpha genes in Type 2 diabetes mellitus by next-generation sequencing

BACKGROUND

The nuclear receptors Rev-erb alpha and Rev-erb beta are transcription factors that regulate the function of genes in glucose and lipid metabolism, and they also form a link between circadian rhythm and metabolism. We evaluated the variations in Rev-erb alpha and Rev-erb beta genes together with biochemical parameters as risk factors in type 2 diabetic (T2DM) patients.

METHODS

Molecular analyses of Rev-erb alpha and Rev-erb beta genes were performed on genomic DNA by using next-generation sequencing in 42 T2DM patients (21 obese and 21 non-obese) and 66 healthy controls.

RESULTS

We found 26 rare mutations in the study groups, including 13 missense mutations, 9 silent mutations, 3 5'UTR variations, and a 3'UTR variation, of which 9 were novel variations (5 missense and 3 silent and 1 5'UTR). Six common variations were also found in the Rev-erb genes; Rev-erb beta Chr3:24003765 A > G, Rev-erb beta rs924403442 (Chr3:24006717) G > T, Rev-erb alpha Chr17:38253751 T > C, Rev-erb alpha rs72836608 C > A, Rev-erb alpha rs2314339 C > T and Rev-erb alpha rs2102928 C > T. Of these, Rev-erb beta Chr3:24003765 A > G was a novel missense mutation (p.Q197R), while others were identified as intronic variants. T2DM patients with Rev-erb beta rs924403442 T allele had lower body surface area (BSA) than noncarriers (GG genotype) (p = 0.039). Rev-erb alpha rs72836608 A allele and Rev-erb alpha rs2314339 CC genotype were associated with decreased serum HDL-cholesterol levels in T2DM patients (p = 0.025 and p = 0.027, respectively). In our study, different effects of Rev-erbs polymorphisms were found according to gender and presence of obesity. Rev-erb alpha rs72836608 (C > A) and rs2314339 (C > T) and Rev-erb alpha rs2102928 (C > T) were associated with low HDL-C levels in male T2DM patients. In female patients, Rev-erb alpha rs2102928 (C > T) was associated with high microalbuminuria and Rev-erb beta rs9244403442 G > T was associated with low HDL and high BSA values. In addition, Rev-erb alpha Chr17: 38,253,751 (T > C), rs72836608 (C > A), and rs2314339 (C > T) and Rev-erb beta Chr3:24003765 (A > G) were associated with increased serum GGT levels in obese T2DM patients. In non-obese patients, Rev-erbs SNPs had no effect on serum GGT levels.

CONCLUSION

Our findings indicate that variations in the Rev-erb alpha and Rev-erb beta genes can affect metabolic changes in T2DM and these effects may vary depending on gender and obesity.

Interaction of polymorphisms in APOA4-APOA5-ZPR1-BUD13 gene cluster and sleep duration on 5-year lipid changes in middle aged and older Chinese

STUDY OBJECTIVES

Lipid profiles are influenced by both genetic and environmental factors. Genetic variants in the APOA4-APOA5-ZPR1-BUD13 gene cluster and aberrant sleep duration were independently identified to be associated with lipids in previous studies. We aimed to investigate whether sleep duration modified the genetic associations with longitudinal lipids changes.

METHODS

Four single nucleotide polymorphisms (SNPs), rs17119975, rs651821, rs7396835, and rs964184 in the APOA4-APOA5-ZPR1-BUD13 gene cluster were genotyped among 8648 apparently healthy subjects from the Dongfeng-Tongji (DFTJ) cohort. Information on sleep duration was obtained by questionnaires. Changes in total cholesterol, triglyceride, high-density lipoprotein cholesterol (HDL-c), low-density lipoprotein cholesterol (LDL-c), were evaluated from baseline to 5-year follow-up.

RESULTS

After multivariate adjustments, we found that rs651821 and weighted genetic risk score (GRS) were significantly associated with increased triglyceride, and the genetic association with triglyceride change consistently strengthened across sleep duration categories. The differences in triglyceride changes per increment of risk allele for rs651821 were 0.028 (SE = 0.017, p = 0.112), 0.051 (SE = 0.009, p < 0.001), and 0.064 (SE = 0.016, p < 0.001) in individuals with sleep duration ≤7, >7-<9, and ≥9 h, respectively (p interaction = 0.031). The GRS also showed a significant interaction with sleep duration categories for triglyceride change (p interaction = 0.010). In addition, all of the four SNPs and GRS were inversely related to HDL-c changes.

CONCLUSIONS

Longer sleep duration might exacerbate the adverse effects of SNPs in APOA4-APOA5-ZPR1-BUD13 gene cluster on 5-year triglyceride changes.

A circadian rhythm-related MTNR1B genetic variant (rs10830963) modulate body weight change and insulin resistance after 9 months of a high protein/low carbohydrate vs a standard hypocaloric diet

BACKGROUND & AIMS

The risk allele (G) of rs10830963 in the melatonin receptor 1 B (MTNR1B) gene presents an association with biochemical parameters and obesity. We study the effect of this SNP on insulin resistance and weight loss secondary to two hypocaloric diets.

METHODS

270 obese subjects were randomly allocated during 9 months (Diet HP: a high protein/low carbohydrate vs. Diet S: a standard severe hypocaloric diets). Anthropometric parameters, fasting blood glucose, C-reactive protein (CRP), insulin concentration, insulin resistance (HOMA-IR), lipid profile and adipocytokines levels were measured. Genotype of MTNR1B gene polymorphism (rs10830963) was evaluated.

RESULTS

All adiposity parameters, systolic blood pressure and leptin levels decreased in all subjects after both diets. This improvement of adiposity parameters was higher in non-G allele carriers than G allele carriers. After weight loss with Diet HP, (CC vs. CG + GG at 9 months); total cholesterol (delta: -9.9 ± 2.4 mg/dl vs. -4.8 ± 2.2 mg/dl:p < 0.05), LDL-cholesterol (delta: -8.3 ± 1.9 mg/dl vs. -5.1 ± 2.2 mg/dl: p < 0.05), insulin (delta: -4.7 ± 0.8 UI/L vs. -0.9 ± 1.0 UI/L: p < 0.05), triglycerides (delta: -17.7 ± 3.9 mg/dl vs. -6.1 ± 2.8 mg/dl: p < 0.05) and HOMA IR (delta: -0.8 ± 0.2 units vs. -0.2 ± 0.1 units: p < 0.05) improved only in no G allele carriers. After weight loss with Diet S in non G allele carriers, insulin levels (delta (CC vs. CG + GG): -3.4 ± 0.6 UI/L vs. -1.2 ± 0.4 UI/L: p < 0.05), triglycerides (delta: -29.2 ± 3.4 mg/dl vs. -8.2 ± 3.8 mg/dl: p < 0.05), HOMA-IR (delta (CC vs. CG + GG): -1.1 ± 0.2 units vs. -0.1 ± 0.1 units: p < 0.05), total cholesterol (delta: -15.9 ± 7.4 mg/dl vs. -5.8 ± 2.9 mg/dl:ns) and LDL-cholesterol (delta: -13.7 ± 5.9 mg/dl vs. -6.0 ± 2.9 mg/dl: ns) decreased, too.

CONCLUSIONS

our study detected a relationship of rs10830963 variant of MTNR1B gene with adiposity changes, cholesterol changes and insulin resistance modification induced by two different hypocaloric during 9 months.

Sleep Apnea and Sleep Habits: Relationships with Metabolic Syndrome

Excess visceral adiposity is a primary cause of metabolic syndrome and often results from excess caloric intake and a lack of physical activity. Beyond these well-known etiologic factors, however, sleep habits and sleep apnea also seem to contribute to abdominal obesity and metabolic syndrome: Evidence suggests that sleep deprivation and behaviors linked to evening chronotype and social jetlag affect eating behaviors like meal preferences and eating times. When circadian rest and activity rhythms are disrupted, hormonal and metabolic regulations also become desynchronized, and this is known to contribute to the development of metabolic syndrome. The metabolic consequences of obstructive sleep apnea syndrome (OSAS) also contribute to incident metabolic syndrome. These observations, along with the first sleep intervention studies, have demonstrated that sleep is a relevant lifestyle factor that needs to be addressed along with diet and physical activity. Personalized lifestyle interventions should be tested in subjects with metabolic syndrome, based on their specific diet and physical activity habits, but also according to their circadian preference. The present review therefore focuses (i) on the role of sleep habits in the development of metabolic syndrome, (ii) on the reciprocal relationship between sleep apnea and metabolic syndrome, and (iii) on the results of sleep intervention studies.

Role of metabolic syndrome and its components as mediators of the genetic effect on type 2 diabetes: A family-based study in China

BACKGROUND

Metabolic syndrome (MetS) share a genetic basis with type 2 diabetes (T2D). However, whether MetS and its components mediate genetic susceptibility to T2D is not completely understood.

METHODS

We assessed the effects of MetS and its components on associations T2D and 18 genome-wide association studies-identified variants using a two-stage strategy based on parametric models involving 7110 Chinese participants (2436 were T2D patients) across 2885 families. Multilevel logistic regression was used to account for the intrafamilial correlation.

RESULTS

Metabolic syndrome significantly mediated the effect of a melatonin receptor 1B (MTNR1B) polymorphism on T2D risk (OR of average causal mediation effect [OR_ACME ] 1.004; 95% confidence interval [CI] 1.001-1.008; P = 0.018). In addition, low high-density lipoprotein cholesterol (HDL-C) levels mediated the genetic effects of MTNR1B (OR_ACME 1.012; 95% CI 1.007-1.015; P < 0.001), solute carrier family 30 member 8 (SLC30A8; OR_ACME 1.001; 95% CI 1.000-1.007; P < 0.040), B-cell lymphoma/leukemia 11A (BCL11A; OR_ACME 1.009; 95% CI 1.007-1.016; P < 0.001), prospero homeobox 1 (PROX1; OR_ACME 1.005; 95% CI 1.003-1.011; P < 0.001) and a disintegrin and metallopeptidase with thrombospondin type 1 motif 9 (ADAMTS9; OR_ACME 1.006; 95% CI 1.001-1.009; P = 0.022), whereas increased fasting blood glucose (FBG) significantly mediated the genetic effect of BCL11A (OR_ACME 1.017; 95% CI 1.003-1.021; P = 0.012).

CONCLUSIONS

This study provides evidence that MetS and two of its components (HDL-C, FBG) may be involved in mediating the genetic predisposition to T2D, which emphasize the importance of maintaining normal HDL-C and FBG levels.

Dietary-fat effect of the rs10830963 polymorphism in MTNR1B on insulin resistance in response to 3 months weight-loss diets

BACKGROUND & AIMS

The risk allele (G) of rs10830963 in the melatonin receptor 1 B (MTNR1B) gene presents an association with obesity. We study the effect of this SNP on cardiovascular risk factors and weight loss secondary to 2hypocaloric diets.

METHODS

361 obese subjects were randomly allocated during 3 months (Diet M - high monounsaturated fat hypocaloric diet vs. Diet P - high polyunsaturated fat hypocaloric diet). Anthropometric parameters, fasting blood glucose, C-reactive protein (CRP), insulin concentration, insulin resistance (HOMA-IR), lipid profile and adipocytokines levels were measured. Genotype of MTNR1B gene polymorphism (rs10830963) was evaluated.

RESULTS

All anthropometric parameters, systolic blood pressure and leptin levels decreased in all subjects after both diets. This improvement of anthropometric parameters was higher in non G allele carriers than G allele carriers. After dietary intervention with Diet M, (CC vs. CG + GG); total cholesterol (delta: -10.4 ± 2.1mg/dl vs. -6.4 ± 1.2mg/dl: P <.05), LDL-cholesterol (delta:-7.1 ± 0.9mg/dl vs. -2.8 ± 0.8mg/dl: P <.05), insulin (delta:-3.0 ± 0.8 UI/L vs. -2.0 ± 1.0 UI/L: P<.05) and HOMA-IR (delta:-3.4 ± 1.0 units vs. -2.9 ± 0.9 units: P<.05) improved in no G allele carriers. After Diet P, in the group of subjects without G allele CC, insulin levels (delta: -2.9 ± 1.0 UI/L vs. -0.6 ± 0.2 UI/L: P <.05) and HOMA-IR (delta (CC vs. CG + GG): -0.8 ± 0.2 units vs. -0.4 ± 0.3 units: P <.05) decreased, too.

CONCLUSIONS

Our study detected a relationship of rs10830963 MTNR1B SNP with body weight loss and insulin resistance modification induced by 2different hypocaloric. Only monounsaturated enriched hypocaloric diet and in no-G allele carriers showed a significant effect on lipoproteins.

DNA Methylation of Five Core Circadian Genes Jointly Contributes to Glucose Metabolism: A Gene-Set Analysis in Monozygotic Twins

The timing of daily fluctuations in blood glucose is tightly controlled by the circadian rhythm. DNA methylation accompanies the circadian clock, and aberrant DNA methylation has been associated with circadian disruption and hyperglycemia. However, the precise role of circadian genes methylation in glucose metabolism is unknown. Using a gene-set approach in monozygotic (MZ) twin pairs, we examined the joint effect of 77 CpGs in five core circadian genes (CLOCK, BMAL1, PER1, PER2, PER3) on glucose-related traits in 138 middle-aged, male-male MZ twins (69 pairs). DNA methylation was quantified by bisulfite pyrosequencing. We first conducted matched twin pair analysis to examine the association of single CpG methylation with glucose metabolism. We then performed gene-based and gene-set analyses by the truncated product method to examine the combined effect of DNA methylation at multiple CpGs in a gene or all five circadian genes as a pathway on glucose metabolism. Of the 77 assayed CpGs, only one site was individually associated with insulin resistance at FDR < 0.05. However, the joint effect of DNA methylation in all five circadian genes together showed a significant association with glucose metabolism. Our results may unravel a biological mechanism through which circadian rhythm regulates blood glucose, and highlight the importance of testing the joint effect of multiple CpGs in epigenetic analysis.

Off the Clock: From Circadian Disruption to Metabolic Disease

Circadian timekeeping allows appropriate temporal regulation of an organism’s internal metabolism to anticipate and respond to recurrent daily changes in the environment. Evidence from animal genetic models and from humans under circadian misalignment (such as shift work or jet lag) shows that disruption of circadian rhythms contributes to the development of obesity and metabolic disease. Inappropriate timing of food intake and high-fat feeding also lead to disruptions of the temporal coordination of metabolism and physiology and subsequently promote its pathogenesis. This review illustrates the impact of genetically or environmentally induced molecular clock disruption (at the level of the brain and peripheral tissues) and the interplay between the circadian system and metabolic processes. Here, we discuss some mechanisms responsible for diet-induced circadian desynchrony and consider the impact of nutritional cues in inter-organ communication, with a particular focus on the communication between peripheral organs and brain. Finally, we discuss the relay of environmental information by signal-dependent transcription factors to adjust the timing of gene oscillations. Collectively, a better knowledge of the mechanisms by which the circadian clock function can be compromised will lead to novel preventive and therapeutic strategies for obesity and other metabolic disorders arising from circadian desynchrony.

Joint Analysis of Multiple Interaction Parameters in Genetic Association Studies

With growing human genetic and epidemiologic data, there has been increased interest for the study of gene-by-environment (G-E) interaction effects. Still, major questions remain on how to test jointly a large number of interactions between multiple SNPs and multiple exposures. In this study, we first compared the relative performance of four fixed-effect joint analysis approaches using simulated data, considering up to 10 exposures and 300 SNPs: (1) omnibus test, (2) multi-exposure and genetic risk score (GRS) test, (3) multi-SNP and environmental risk score (ERS) test, and (4) GRS-ERS test. Our simulations explored both linear and logistic regression while considering three statistics: the Wald test, the Score test, and the likelihood ratio test (LRT). We further applied the approaches to three large sets of human cohort data (n = 37,664), focusing on type 2 diabetes (T2D), obesity, hypertension, and coronary heart disease with smoking, physical activity, diets, and total energy intake. Overall, GRS-based approaches were the most robust, and had the highest power, especially when the G-E interaction effects were correlated with the marginal genetic and environmental effects. We also observed severe miscalibration of joint statistics in logistic models when the number of events per variable was too low when using either the Wald test or LRT test. Finally, our real data application detected nominally significant interaction effects for three outcomes (T2D, obesity, and hypertension), mainly from the GRS-ERS approach. In conclusion, this study provides guidelines for testing multiple interaction parameters in modern human cohorts including extensive genetic and environmental data.

Circadian clocks and insulin resistance

Insulin resistance is a main determinant in the development of type 2 diabetes mellitus and a major cause of morbidity and mortality. The circadian timing system consists of a central brain clock in the hypothalamic suprachiasmatic nucleus and various peripheral tissue clocks. The circadian timing system is responsible for the coordination of many daily processes, including the daily rhythm in human glucose metabolism. The central clock regulates food intake, energy expenditure and whole-body insulin sensitivity, and these actions are further fine-tuned by local peripheral clocks. For instance, the peripheral clock in the gut regulates glucose absorption, peripheral clocks in muscle, adipose tissue and liver regulate local insulin sensitivity, and the peripheral clock in the pancreas regulates insulin secretion. Misalignment between different components of the circadian timing system and daily rhythms of sleep-wake behaviour or food intake as a result of genetic, environmental or behavioural factors might be an important contributor to the development of insulin resistance. Specifically, clock gene mutations, exposure to artificial light-dark cycles, disturbed sleep, shift work and social jet lag are factors that might contribute to circadian disruption. Here, we review the physiological links between circadian clocks, glucose metabolism and insulin sensitivity, and present current evidence for a relationship between circadian disruption and insulin resistance. We conclude by proposing several strategies that aim to use chronobiological knowledge to improve human metabolic health.

Melatonin receptor 1B gene rs10830963 polymorphism, depressive symptoms and glycaemic traits

BACKGROUND

The association between depression and type 2 diabetes is bidirectional. Underlying biological determinants remain elusive. We examined whether a common melatonin receptor 1B gene diabetes risk variant rs10830963 influenced the associations between depressive symptoms and glycaemic traits.

MATERIALS

The Prevalence, Prediction and Prevention of Diabetes-Botnia Study participants (n = 4,455) with no diabetes who underwent an oral glucose tolerance test were genotyped for rs10830963 and completed the Mental Health Inventory on depressive symptoms.

RESULTS

The rs10830963 did not influence significantly the associations between depressive symptoms and glycaemic traits. Yet, the addition of each copy of the minor G allele of the rs1080963 and higher depressive symptoms were both, independent of each other, associated significantly with higher glucose response (glucose area under the curve), higher insulin resistance (Insulin Sensitivity Index) and lower insulin secretion (Disposition Index). Depressive symptoms, but not rs1080963, were also significantly associated with higher fasting insulin, insulin area under the curve and insulin resistance (Homeostasis Model Assessment, Homeostasis Model Assessment-2); rs1080963, but not depressive symptoms, was significantly associated with higher fasting glucose and lower Corrected Insulin Response.

CONCLUSIONS

Our study shows that the diabetes risk variant rs10830963 does not contribute to the known comorbidity between depression and type 2 diabetes. Key messages The association between depression and type 2 diabetes is bidirectional. We tested whether a common variant rs10830963 in the gene encoding Melatonin Receptor 1B influences the known association between depressive symptoms and glycaemic traits in a population-based sample from Western Finland. The MTNR1B genetic diabetes risk variant rs10830963 does not contribute to the known comorbidity between depression and type 2 diabetes. Depressive symptoms and rs10830963 are associated with a worse glycaemic profile independently of each other.

Rotating night shift work and adherence to unhealthy lifestyle in predicting risk of type 2 diabetes: results from two large US cohorts of female nurses

OBJECTIVES

To prospectively evaluate the joint association of duration of rotating night shift work and lifestyle factors with risk of type 2 diabetes risk, and to quantitatively decompose this joint association to rotating night shift work only, to lifestyle only, and to their interaction.

DESIGN

Prospective cohort study.

SETTING

Nurses' Health Study (1988-2012) and Nurses' Health Study II (1991-2013).

PARTICIPANTS

143 410 women without type 2 diabetes, cardiovascular disease, or cancer at baseline.

EXPOSURES

Rotating night shift work was defined as at least three night shifts per month in addition to day and evening shifts in that month. Unhealthy lifestyles included current smoking, physical activity levels below 30 minutes per day at moderate to vigorous intensity, diet in the bottom three fifths of the Alternate Healthy Eating Index score, and body mass index of 25 or above.

MAIN OUTCOME MEASURES

Incident cases of type 2 diabetes were identified through self report and validated by a supplementary questionnaire.

RESULTS

During 22-24 years of follow-up, 10 915 cases of incident type 2 diabetes occurred. The multivariable adjusted hazard ratios for type 2 diabetes were 1.31 (95% confidence interval 1.19 to 1.44) per five year increment of duration of rotating night shift work and 2.30 (1.88 to 2.83) per unhealthy lifestyle factor (ever smoking, low diet quality, low physical activity, and overweight or obesity). For the joint association of per five year increment rotating night shift work and per unhealthy lifestyle factor with type 2 diabetes, the hazard ratio was 2.83 (2.15 to 3.73) with a significant additive interaction (P for interaction <0.001). The proportions of the joint association were 17.1% (14.0% to 20.8%) for rotating night shift work alone, 71.2% (66.9% to 75.8%) for unhealthy lifestyle alone, and 11.3% (7.3% to 17.3%) for their additive interaction.

CONCLUSIONS

Among female nurses, both rotating night shift work and unhealthy lifestyle were associated with a higher risk of type 2 diabetes. The excess risk of rotating night shift work combined with unhealthy lifestyle was higher than the addition of risk associated with each individual factor. These findings suggest that most cases of type 2 diabetes could be prevented by adhering to a healthy lifestyle, and the benefits could be greater in rotating night shift workers.

Macronutrient-specific effect of the MTNR1B genotype on lipid levels in response to 2 year weight-loss diets

Compelling evidence indicates that lipid metabolism is in partial control of the circadian system. In this context, it has been reported that the melatonin receptor 1B (MTNR1B) genetic variant influences the dynamics of melatonin secretion, which is involved in the circadian system as a chronobiotic. The objective was to analyze whether the MTNR1B rs10830963 genetic variant was related to changes in lipid levels in response to dietary interventions with different macronutrient distribution in 722 overweight/obese subjects from the POUNDS Lost trial. We did not find a significant association between the MTNR1B genotype and changes in lipid metabolism. However, dietary fat intake significantly modified genetic effects on 2 year changes in total and LDL cholesterol (P interaction = 0.006 and 0.001, respectively). In the low-fat diet group, carriers of the sleep disruption G allele (minor allele) showed a greater reduction of total cholesterol (β ± SE = -5.78 ± 2.88 mg/dl, P = 0.04) and LDL cholesterol (β ± SE = -7.19 ± 2.37 mg/dl, P = 0.003). Conversely, in the high-fat diet group, subjects carrying the G allele evidenced a smaller decrease in total cholesterol (β ± SE = 5.81 ± 2.65 mg/dl, P = 0.03) and LDL cholesterol (β ± SE = 5.23 ± 2.21 mg/dl, P = 0.002). Subjects carrying the G allele of the circadian rhythm-related MTNR1B variant may present a bigger impact on total and LDL cholesterol when undertaking an energy-restricted low-fat diet.

Gene-Diet Interaction and Precision Nutrition in Obesity

The rapid rise of obesity during the past decades has coincided with a profound shift of our living environment, including unhealthy dietary patterns, a sedentary lifestyle, and physical inactivity. Genetic predisposition to obesity may have interacted with such an obesogenic environment in determining the obesity epidemic. Growing studies have found that changes in adiposity and metabolic response to low-calorie weight loss diets might be modified by genetic variants related to obesity, metabolic status and preference to nutrients. This review summarized data from recent studies of gene-diet interactions, and discussed integration of research of metabolomics and gut microbiome, as well as potential application of the findings in precision nutrition.

Circadian Rhythm and Sleep Disruption: Causes, Metabolic Consequences, and Countermeasures

Circadian (∼24-hour) timing systems pervade all kingdoms of life and temporally optimize behavior and physiology in humans. Relatively recent changes to our environments, such as the introduction of artificial lighting, can disorganize the circadian system, from the level of the molecular clocks that regulate the timing of cellular activities to the level of synchronization between our daily cycles of behavior and the solar day. Sleep/wake cycles are intertwined with the circadian system, and global trends indicate that these, too, are increasingly subject to disruption. A large proportion of the world's population is at increased risk of environmentally driven circadian rhythm and sleep disruption, and a minority of individuals are also genetically predisposed to circadian misalignment and sleep disorders. The consequences of disruption to the circadian system and sleep are profound and include myriad metabolic ramifications, some of which may be compounded by adverse effects on dietary choices. If not addressed, the deleterious effects of such disruption will continue to cause widespread health problems; therefore, implementation of the numerous behavioral and pharmaceutical interventions that can help restore circadian system alignment and enhance sleep will be important.

Sleep, circadian dysrhythmia, obesity and diabetes

Synchrony of biological processes with environmental cues developed over millennia to match growth, reproduction and senescence. This entails a complex interplay of genetic, metabolic, chemical, light, hormonal and hedonistic factors across life forms. Sleep is one of the most prominent rhythms where such a match is established. Over the past 100 years or so, it has been possible to disturb the synchrony between sleep-wake cycle and environmental cues. Development of electric lights, shift work and continual accessibility of the internet has disrupted this match. As a result, many non-communicable diseases such as obesity, insulin resistance, type 2 diabetes, coronary artery disease and malignancies have been attributed in part to such disruption. In this presentation a review is made of the origin and evolution of sleep studies, the pathogenic mediators for such asynchrony, clinical evidence and relevance and suggested management options to deal with the disturbances.

Nutrigenetics and Nutrimiromics of the Circadian System: The Time for Human Health

Even though the rhythmic oscillations of life have long been known, the precise molecular mechanisms of the biological clock are only recently being explored. Circadian rhythms are found in virtually all organisms and affect our lives. Thus, it is not surprising that the correct running of this clock is essential for cellular functions and health. The circadian system is composed of an intricate network of genes interwined in an intrincated transcriptional/translational feedback loop. The precise oscillation of this clock is controlled by the circadian genes that, in turn, regulate the circadian oscillations of many cellular pathways. Consequently, variations in these genes have been associated with human diseases and metabolic disorders. From a nutrigenetics point of view, some of these variations modify the individual response to the diet and interact with nutrients to modulate such response. This circadian feedback loop is also epigenetically modulated. Among the epigenetic mechanisms that control circadian rhythms, microRNAs are the least studied ones. In this paper, we review the variants of circadian-related genes associated to human disease and nutritional response and discuss the current knowledge about circadian microRNAs. Accumulated evidence on the genetics and epigenetics of the circadian system points to important implications of chronotherapy in the clinical practice, not only in terms of pharmacotherapy, but also for dietary interventions. However, interventional studies (especially nutritional trials) that include chronotherapy are scarce. Given the importance of chronobiology in human health such studies are warranted in the near future.

Common type 2 diabetes risk variant in MTNR1B worsens the deleterious effect of melatonin on glucose tolerance in humans

AIMS

The common MTNR1B genetic variant rs10830963 is associated with an increased risk of type 2 diabetes (T2D). To date, no experimental study has tested the effect of the MTNR1B variant on glucose metabolism in humans during exposure of the melatonin receptors to their ligand. The aim of this study was to investigate whether this MTNR1B variant influenced the effect of melatonin (5mg) on glucose tolerance assessed by an oral glucose tolerance test (OGTT; 75 g) at different times of the day (morning and evening) as compared to a placebo.

METHODS

Seventeen normoglycemic women (24 ± 6 years; BMI 23.0 ± 3.3 kg/m(2)) completed the study (11 carriers of the risk allele [CG] and 6 noncarriers [CC]).

RESULTS

The effect of melatonin on glucose tolerance depended on the genotype. In the morning, the effect of melatonin (melatonin-placebo) on the glucose area under the curve (AUC) above baseline differed significantly (P=0.036) between the carriers and noncarriers. This effect of melatonin in the carriers was six times as large as that in the noncarriers. The MTNR1B SNP explained over one-quarter (26%) of the inter-individual differences in the effect of melatonin on glucose AUC. However, in the evening, the effect of melatonin on glucose AUC of the carriers and noncarriers did not differ significantly (P>0.05).

CONCLUSIONS

MTNR1B rs10830963 risk variant worsens the effect of melatonin on glucose tolerance, suggesting the importance of genotyping and personalized recommendations, especially in people consuming food when melatonin levels are elevated. Large-scale studies in vulnerable populations are necessary to translate these results into real-world, clinically relevant recommendations.

The Rotterdam Study: 2016 objectives and design update

The Rotterdam Study is a prospective cohort study ongoing since 1990 in the city of Rotterdam in The Netherlands. The study targets cardiovascular, endocrine, hepatic, neurological, ophthalmic, psychiatric, dermatological, otolaryngological, locomotor, and respiratory diseases. As of 2008, 14,926 subjects aged 45 years or over comprise the Rotterdam Study cohort. The findings of the Rotterdam Study have been presented in over 1200 research articles and reports (see www.erasmus-epidemiology.nl/rotterdamstudy ). This article gives the rationale of the study and its design. It also presents a summary of the major findings and an update of the objectives and methods.