Maternal and Early-Life Circadian Disruption Have Long-Lasting Negative Consequences on Offspring Development and Adult Behavior in Mice

Energetic demands regulate sleep-wake rhythm circuit development

Sleep and feeding patterns lack strong daily rhythms during early life. As diurnal animals mature, feeding is consolidated to the day and sleep to the night. In Drosophila, circadian sleep patterns are initiated with formation of a circuit connecting the central clock to arousal output neurons; emergence of circadian sleep also enables long-term memory (LTM). However, the cues that trigger the development of this clock-arousal circuit are unknown. Here, we identify a role for nutritional status in driving sleep-wake rhythm development in Drosophila larvae. We find that in the 2nd instar larval period (L2), sleep and feeding are spread across the day; these behaviors become organized into daily patterns by the 3rd instar larval stage (L3). Forcing mature (L3) animals to adopt immature (L2) feeding strategies disrupts sleep-wake rhythms and the ability to exhibit LTM. In addition, the development of the clock (DN1a)-arousal (Dh44) circuit itself is influenced by the larval nutritional environment. Finally, we demonstrate that larval arousal Dh44 neurons act through glucose metabolic genes to drive onset of daily sleep-wake rhythms. Together, our data suggest that changes to energetic demands in developing organisms trigger the formation of sleep-circadian circuits and behaviors.

Energetic Demands Regulate Sleep-Wake Rhythm Circuit Development

Sleep and feeding patterns lack strong daily rhythms during early life. As diurnal animals mature, feeding is consolidated to the day and sleep to the night. In Drosophila, circadian sleep patterns are initiated with formation of a circuit connecting the central clock to arousal output neurons; emergence of circadian sleep also enables long-term memory (LTM). However, the cues that trigger the development of this clock-arousal circuit are unknown. Here, we identify a role for nutritional status in driving sleep-wake rhythm development in Drosophila larvae. We find that in the 2nd instar larval period (L2), sleep and feeding are spread across the day; these behaviors become organized into daily patterns by the 3rd instar larval stage (L3). Forcing mature (L3) animals to adopt immature (L2) feeding strategies disrupts sleep-wake rhythms and the ability to exhibit LTM. In addition, the development of the clock (DN1a)-arousal (Dh44) circuit itself is influenced by the larval nutritional environment. Finally, we demonstrate that larval arousal Dh44 neurons act through glucose metabolic genes to drive onset of daily sleep-wake rhythms. Together, our data suggest that changes to energetic demands in developing organisms trigger the formation of sleep-circadian circuits and behaviors.

Sleep and circadian rhythms during pregnancy, social disadvantage, and alterations in brain development in neonates

Pregnant women in poverty may be especially likely to experience sleep and circadian rhythm disturbances, which may have downstream effects on fetal neurodevelopment. However, the associations between sleep and circadian rhythm disturbances, social disadvantage during pregnancy, and neonatal brain structure remains poorly understood. The current study explored the association between maternal sleep and circadian rhythm disturbances during pregnancy and neonatal brain outcomes, examining sleep and circadian rhythm disturbances as a mediator of the effect of social disadvantage during pregnancy on infant structural brain outcomes. The study included 148 mother-infant dyads, recruited during early pregnancy, who had both actigraphy and neuroimaging data. Mothers' sleep was assessed throughout their pregnancy using actigraphy, and neonates underwent brain magnetic resonance imaging in the first weeks of life. Neonatal structural brain outcomes included cortical gray matter, subcortical gray matter, and white matter volumes along with a measure of the total surface area of the cortex. Neonates of mothers who experienced greater inter-daily deviations in sleep duration had smaller total cortical gray and white matter volumes and reduced cortical surface areas. Neonates of mothers who had higher levels of circadian misalignment and later sleep timing during pregnancy showed smaller subcortical gray matter volumes. Inter-daily deviations in sleep duration during pregnancy mediated the association between maternal social disadvantage and neonatal structural brain outcomes. Findings highlight the importance of regularity and rhythmicity in sleep schedules during pregnancy and bring to light the role of chronodisruption as a potential mechanism underlying the deleterious neurodevelopmental effects of prenatal adversity. RESEARCH HIGHLIGHTS: Social disadvantage was associated with sleep and circadian rhythm disturbances during pregnancy, including later sleep schedules, increased variability in sleep duration, circadian misalignment, and a higher proportion of the sleep period spent awake. Maternal sleep and circadian rhythm disturbances during pregnancy were associated with decreased brain volume and reduced cortical surface area in neonates. Maternal inter-daily deviations in sleep duration during pregnancy mediated the association between social disadvantage and neonatal brain volume and cortical surface area.

Maternal circadian rhythm disruption affects neonatal inflammation via metabolic reprograming of myeloid cells

Disruption of circadian rhythm during pregnancy produces adverse health outcomes in offspring; however, the role of maternal circadian rhythms in the immune system of infants and their susceptibility to inflammation remains poorly understood. Here we show that disruption of circadian rhythms in pregnant mice profoundly aggravates the severity of neonatal inflammatory disorders in both male and female offspring, such as necrotizing enterocolitis and sepsis. The diminished maternal production of docosahexaenoic acid (DHA) and the impaired immunosuppressive function of neonatal myeloid-derived suppressor cells (MDSCs) contribute to this phenomenon. Mechanistically, DHA enhances the immunosuppressive function of MDSCs via PPARγ-mediated mitochondrial oxidative phosphorylation. Transfer of MDSCs or perinatal supplementation of DHA relieves neonatal inflammation induced by maternal rhythm disruption. These observations collectively demonstrate a previously unrecognized role of maternal circadian rhythms in the control of neonatal inflammation via metabolic reprograming of myeloid cells.

Ontogeny of the circadian system: a multiscale process throughout development

The 24 h (circadian) timing system develops in mammals during the perinatal period. It carries out the essential task of anticipating daily recurring environmental changes to identify the best time of day for each molecular, cellular, and systemic process. Although significant knowledge has been acquired about the organization and function of the adult circadian system, relatively little is known about its ontogeny. During the perinatal period, the circadian system progressively gains functionality under the influence of the early environment. This review explores current evidence on the development of the circadian clock in mammals, highlighting the multilevel complexity of the process and the importance of gaining a better understanding of its underlying biology.

Circadian Regulation of the Neuroimmune Environment Across the Lifespan: From Brain Development to Aging

Circadian clocks confer 24-h periodicity to biological systems, to ultimately maximize energy efficiency and promote survival in a world with regular environmental light cycles. In mammals, circadian rhythms regulate myriad physiological functions, including the immune, endocrine, and central nervous systems. Within the central nervous system, specialized glial cells such as astrocytes and microglia survey and maintain the neuroimmune environment. The contributions of these neuroimmune cells to both homeostatic and pathogenic demands vary greatly across the day. Moreover, the function of these cells changes across the lifespan. In this review, we discuss circadian regulation of the neuroimmune environment across the lifespan, with a focus on microglia and astrocytes. Circadian rhythms emerge in early life concurrent with neuroimmune sculpting of brain circuits and wane late in life alongside increasing immunosenescence and neurodegeneration. Importantly, circadian dysregulation can alter immune function, which may contribute to susceptibility to neurodevelopmental and neurodegenerative diseases. In this review, we highlight circadian neuroimmune interactions across the lifespan and share evidence that circadian dysregulation within the neuroimmune system may be a critical component in human neurodevelopmental and neurodegenerative diseases.

Gestational Early-Time Restricted Feeding Results in Sex-Specific Glucose Intolerance in Adult Male Mice

The timing of food intake is a novel dietary component that impacts health. Time-restricted feeding (TRF), a form of intermittent fasting, manipulates food timing. The timing of eating may be an important factor to consider during critical periods, such as pregnancy. Nutrition during pregnancy, too, can have a lasting impact on offspring health. The timing of food intake has not been thoroughly investigated in models of pregnancy, despite evidence that interest in the practice exists. Therefore, using a mouse model, we tested body composition and glycemic health of gestational early TRF (eTRF) in male and female offspring from weaning to adulthood on a chow diet and after a high-fat, high-sucrose (HFHS) diet challenge. Body composition was similar between groups in both sexes from weaning to adulthood, with minor increases in food intake in eTRF females and slightly improved glucose tolerance in males while on a chow diet. However, after 10 weeks of HFHS, male eTRF offspring developed glucose intolerance. Further studies should assess the susceptibility of males, and apparent resilience of females, to gestational eTRF and assess mechanisms underlying these changes in adult males.

Loss of sleep when it is needed most - Consequences of persistent developmental sleep disruption: A scoping review of rodent models

Sleep is an essential component of development. Developmental sleep disruption (DSD) impacts brain maturation and has been associated with significant consequences on socio-emotional development. In humans, poor sleep during infancy and adolescence affects neurodevelopmental outcomes and may be a risk factor for the development of autism spectrum disorder (ASD) or other neuropsychiatric illness. Given the wide-reaching and enduring consequences of DSD, identifying underlying mechanisms is critical to best inform interventions with translational capacity. In rodents, studies have identified some mechanisms and neural circuits by which DSD causes later social, emotional, sensorimotor, and cognitive changes. However, these studies spanned methodological differences, including different developmental timepoints for both sleep disruption and testing, different DSD paradigms, and even different rodent species. In this scoping review on DSD in rodents, we synthesize these various studies into a cohesive framework to identify common neural mechanisms underlying DSD-induced dysfunction in brain and behavior. Ultimately, this review serves the goal to inform the generation of novel translational interventions for human developmental disorders featuring sleep disruption.

Circadian Disruption and Mental Health: The Chronotherapeutic Potential of Microbiome-Based and Dietary Strategies

Mental illness is alarmingly on the rise, and circadian disruptions linked to a modern lifestyle may largely explain this trend. Impaired circadian rhythms are associated with mental disorders. The evening chronotype, which is linked to circadian misalignment, is a risk factor for severe psychiatric symptoms and psychiatric metabolic comorbidities. Resynchronization of circadian rhythms commonly improves psychiatric symptoms. Furthermore, evidence indicates that preventing circadian misalignment may help reduce the risk of psychiatric disorders and the impact of neuro-immuno-metabolic disturbances in psychiatry. The gut microbiota exhibits diurnal rhythmicity, as largely governed by meal timing, which regulates the host's circadian rhythms. Temporal circadian regulation of feeding has emerged as a promising chronotherapeutic strategy to prevent and/or help with the treatment of mental illnesses, largely through the modulation of gut microbiota. Here, we provide an overview of the link between circadian disruption and mental illness. We summarize the connection between gut microbiota and circadian rhythms, supporting the idea that gut microbiota modulation may aid in preventing circadian misalignment and in the resynchronization of disrupted circadian rhythms. We describe diurnal microbiome rhythmicity and its related factors, highlighting the role of meal timing. Lastly, we emphasize the necessity and rationale for further research to develop effective and safe microbiome and dietary strategies based on chrononutrition to combat mental illness.

Voluntary Wheel Running Exercise Does Not Attenuate Circadian and Cardiac Dysfunction Caused by Conditional Deletion of Bmal1

Circadian misalignment occurs with age, jet lag, and shift work, leading to maladaptive health outcomes including cardiovascular diseases. Despite the strong link between circadian disruption and heart disease, the cardiac circadian clock is poorly understood, prohibiting identification of therapies to restore the broken clock. Exercise is the most cardioprotective intervention identified to date and has been suggested to reset the circadian clock in other peripheral tissues. Here, we tested the hypothesis that conditional deletion of core circadian gene Bmal1 would disrupt cardiac circadian rhythm and function and that this disruption would be ameliorated by exercise. To test this hypothesis, we generated a transgenic mouse with spatial and temporal deletion of Bmal1 only in adult cardiac myocytes (Bmal1 cardiac knockout [cKO]). Bmal1 cKO mice demonstrated cardiac hypertrophy and fibrosis concomitant with impaired systolic function. This pathological cardiac remodeling was not rescued by wheel running. While the molecular mechanisms responsible for the profound cardiac remodeling are unclear, it does not appear to involve activation of the mammalian target of rapamycin (mTOR) signaling or changes in metabolic gene expression. Interestingly, cardiac deletion of Bmal1 disrupted systemic rhythms as evidenced by changes in the onset and phasing of activity in relationship to the light/dark cycle and by decreased periodogram power as measured by core temperature, suggesting cardiac clocks can regulate systemic circadian output. Together, we suggest a critical role for cardiac Bmal1 in regulating both cardiac and systemic circadian rhythm and function. Ongoing experiments will determine how disruption of the circadian clock causes cardiac remodeling in an effort to identify therapeutics to attenuate the maladaptive outcomes of a broken cardiac circadian clock.

Maternal melatonin treatment rescues endocrine, inflammatory, and transcriptional deregulation in the adult rat female offspring from gestational chronodisruption

Introduction

Gestational chronodisruption impact maternal circadian rhythms, inhibiting the nocturnal increase of melatonin, a critical hormone that contributes to maternal changes adaptation, entrains circadian rhythms, and prepares the fetus for birth and successful health in adulthood. In rats, we know that gestational chronodisruption by maternal chronic photoperiod shifting (CPS) impaired maternal melatonin levels and resulted in long-term metabolic and cardiovascular effects in adult male offspring. Here, we investigated the consequences of CPS on mother and adult female offspring and explored the effects of melatonin maternal supplementation. Also, we tested whether maternal melatonin administration during gestational chronodisruption rescues maternal circadian rhythms, pregnancy outcomes, and transcriptional functions in adult female offspring.

Methods

Female rats raised and maintained in photoperiod 12:12 light: dark were mated and separated into three groups: (a) Control photoperiod 12:12 (LD); (b) CPS photoperiod; and (c) CPS+Mel mothers supplemented with melatonin in the drinking water throughout gestation. In the mother, we evaluated maternal circadian rhythms by telemetry and pregnancy outcomes, in the long-term, we study adult female offspring by evaluating endocrine and inflammatory markers and the mRNA expression of functional genes involved in adrenal, cardiac, and renal function.

Results

In the mothers, CPS disrupted circadian rhythms of locomotor activity, body temperature, and heart rate and increased gestational length by almost 12-h and birth weight by 12%, all of which were rescued by maternal melatonin administration. In the female offspring, we found blunted day/night differences in circulating levels of melatonin and corticosterone, abnormal patterns of pro-inflammatory cytokines Interleukin-1a (IL1a), Interleukin-6 (IL6), and Interleukin-10 (IL10); and differential expression in 18 out of 24 adrenal, cardiac, and renal mRNAs evaluated.

Conclusion

Maternal melatonin contributed to maintaining the maternal circadian rhythms in mothers exposed to CPS, and the re-establishing the expression of 60% of the altered mRNAs to control levels in the female offspring. Although we did not analyze the effects on kidney, adrenal, and heart physiology, our results reinforce the idea that altered maternal circadian rhythms, resulting from exposure to light at night, should be a mechanism involved in the programming of Non-Communicable Diseases.

Association between maternal shift work during pregnancy child overweight and metabolic outcomes in early childhood

Background

Previous studies found that maternal shift work during pregnancy was associated with many reproductive hazards, including small for gestational age, preterm birth, stillbirth, and neurodevelopmental impairment. Some studies also showed that these children are more likely to become overweight in early childhood. However, the association with metabolic factors, such as insulin resistance and dyslipidemia, was less studied. Hence, we aimed to understand better the relationship between maternal shift work during pregnancy and the risk of childhood overweight and metabolic outcomes. Confounding factors were also discussed, including diet, exercise, and demographical factors.

Methods

We enrolled pregnant women before delivery in the Taiwan Birth Panel Study (TBPS) II conducted between 2010 and 2012, and followed the children of these participants in 2018. The objective of this study is to investigate the influence of prenatal and postnatal factors on infant and early childhood health. During the follow-up in 2018, we checked children's demographic data, obtained blood specimens, and checked their blood sugar, blood insulin, and lipid profiles. Structured questionnaires were used to evaluate demographic data. Multiple linear and logistic regressions were used to examine the associations between maternal shift work during pregnancy and child overweight, metabolic disorders, such as HOMA-IR, and lipid profiles.

Results

In this study, we included 407 mother-children pairs with different work shifts (350 day workers and 57 shift workers), and a sub-population without underweight children was also created (290 day workers and 47 shift workers). Shift work during pregnancy was associated with a higher Homeostasis Model Assessment-Insulin Resistance index (HOMA-IR) and a higher odds ratio for overweight in children born from mothers doing shift work during pregnancy after adjustment. The findings were attenuated when we investigated the effect of shift work before pregnancy.

Conclusion

Our study suggested that maternal shift work during pregnancy was associated with child overweight and insulin resistance in early childhood.

Circadian Regulation of Hormonal Timing and the Pathophysiology of Circadian Dysregulation

Circadian rhythms are endogenously generated, daily patterns of behavior and physiology that are essential for optimal health and disease prevention. Disruptions to circadian timing are associated with a host of maladies, including metabolic disease and obesity, diabetes, heart disease, cancer, and mental health disturbances. The circadian timing system is hierarchically organized, with a master circadian clock located in the suprachiasmatic nucleus (SCN) of the anterior hypothalamus and subordinate clocks throughout the CNS and periphery. The SCN receives light information via a direct retinal pathway, synchronizing the master clock to environmental time. At the cellular level, circadian rhythms are ubiquitous, with rhythms generated by interlocking, autoregulatory transcription-translation feedback loops. At the level of the SCN, tight cellular coupling maintains rhythms even in the absence of environmental input. The SCN, in turn, communicates timing information via the autonomic nervous system and hormonal signaling. This signaling couples individual cellular oscillators at the tissue level in extra-SCN brain loci and the periphery and synchronizes subordinate clocks to external time. In the modern world, circadian disruption is widespread due to limited exposure to sunlight during the day, exposure to artificial light at night, and widespread use of light-emitting electronic devices, likely contributing to an increase in the prevalence, and the progression, of a host of disease states. The present overview focuses on the circadian control of endocrine secretions, the significance of rhythms within key endocrine axes for typical, homeostatic functioning, and implications for health and disease when dysregulated. © 2022 American Physiological Society. Compr Physiol 12: 1-30, 2022.

Fragmented day-night cycle induces reduced light avoidance, excessive weight gain during early development, and binge-like eating during adulthood in mice

Fragmented day-night (FDN) cycles are environments in which multiple periods of light and dark alternate across a 24 h period. Exposure to FDN cycles disrupts circadian rhythms, resulting in period lengthening and alterations to mood in mice. A constant light environment, which also induces period lengthening, is linked to mood and metabolic disturbances and disruption to the development of the circadian clock. This study aims to determine how exposure to the FDN cycle impacts development in mice, with the hypothesis that there would be similar and adverse effects as observed in constant light conditions. Our study used CD-1 mice reared under the FDN cycle compared to the commonly used 12 h light: 12 h dark consolidated day-night cycle. During the first week of development, mouse pups reared under the FDN cycle gained bodyweight at a faster rate and did not avoid aberrant light exposure in comparison to 12:12 LD reared mouse pups. Developmental exposure to the FDN cycle lasted two weeks, and then mice were transferred to the 12:12 LD cycle, where after 2 weeks, bodyweight was similar between FDN reared and 12:12 LD reared mice at 1-month and 2-months old. When re-exposed to the FDN cycle during adulthood, FDN reared pups exhibited binge-like eating behaviors and reduced light avoidance. This study shows that the unnatural distribution of light and dark across the 24 h day can cause disruptions during early development that can reappear during adulthood when placed in the same stressful light-dark environment as adults.

Evening blue-light exposure, maternal glucose, and infant birthweight

Maternal-fetal consequences of exposure to blue-wavelength light are poorly understood. This study tested the hypothesis that evening blue-light exposure is associated with maternal fasting glucose and infant birthweight. Forty-one pregnant women (body mass index = 32.90 ± 6.35 kg/m² ; 24-39 years old; 16 with gestational diabetes mellitus [GDM]) wore actigraphs for 7 days, underwent polysomnography, and completed study questionnaires during gestational week 30 ± 3.76. Infant birthweight (n = 41) and maternal fasting glucose (n = 30; range = 16-36 weeks) were recorded from the mothers' medical charts. Blue-light exposure was obtained from Actiwatch-Spectrum recordings. Adjusted and unadjusted linear regression analyses were performed to determine sleep characteristics associated with maternal fasting glucose and infant-birthweight. The mean fasting mid- to late-gestation glucose was 95.73 ± 24.68 mg/dl and infant birthweight was 3271 ± 436 g. In unadjusted analysis, maternal fasting glucose was associated with blue-light exposure (β = 3.82, p = 0.03). In the final model of multiple linear regression for fasting glucose, evening blue-light exposure (β = 4.00, p = 0.01) remained significant after controlling for gestational weight gain, parity, sleep duration, and GDM. Similarly, blue-light exposure was associated with infant birthweight (69.79, p = 0.006) in the unadjusted model, and remained significant (β = 70.38, p = 0.01) after adjusting for weight gain, wakefulness after sleep onset, gestational age at delivery, and GDM. Higher blue-light exposure in pregnancy is associated with higher fasting glucose and infant birthweight. Reduced use of electronic devices before bedtime is a modifiable behavior.

Resource scarcity but not maternal separation provokes unpredictable maternal care sequences in mice and both upregulate Crh-associated gene expression in the amygdala

Early life adversity (ELA) is a major risk factor for the development of pathology, including anxiety disorders. Neurodevelopmental and behavioral outcomes following ELA are multifaceted and are influenced heavily by the type of adversity experienced and sex of the individual experiencing ELA. It remains unclear what properties of ELA portend differential neurobiological risk and the basis of sex-differences for negative outcomes. Predictability of the postnatal environment has emerged as being a core feature supporting development, with the most salient signals deriving from parental care. Predictability of parental care may be a distinguishing feature of different forms of ELA, and the degree of predictability afforded by these manipulations may contribute to the diversity of outcomes observed across models. Further, questions remain as to whether differing levels of predictability may contribute to differential effects on neurodevelopment and expression of genes associated with risk for pathology. Here, we tested the hypothesis that changes in maternal behavior in mice would be contingent on the type of ELA experienced, directly comparing predictability of care in the limited bedding and nesting (LBN) and maternal separation (MS) paradigms. We then tested whether the predictability of the ELA environment altered the expression of corticotropin-releasing hormone (Crh), a sexually-dimorphic neuropeptide that regulates threat-related learning, in the amygdala of male and female mice. The LBN manipulation reliably increased the entropy of maternal care, a measure that indicates lower predictability between sequences of dam behavior. LBN and MS rearing similarly increased the frequency of nest sorties and licking of pups but had mixed effects on other aspects of dam-, pup-, and nest-related behaviors. Increased expression of Crh-related genes was observed in pups that experienced ELA, with gene expression measures showing a significant interaction with sex and type of ELA manipulation. Specifically, MS was associated with increased expression of Crh-related genes in males, but not females, and LBN primarily increased expression of these genes in females, but not males. The present study provides evidence for predictability as a distinguishing feature of models of ELA and demonstrates robust consequences of these differing experience on sex-differences in gene expression critically associated with stress responding and sex differences in risk for pathology.

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Type of early life adversity differentially altered quantity of maternal behavior.

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Limited bedding and nesting increased unpredictable dam behavior.

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Amygdalar Crh expression in male and female pups were dependent on the type rearing.

The hidden link between circadian entropy and mental health disorders

The high overlapping nature of various features across multiple mental health disorders suggests the existence of common psychopathology factor(s) (p-factors) that mediate similar phenotypic presentations across distinct but relatable disorders. In this perspective, we argue that circadian rhythm disruption (CRD) is a common underlying p-factor that bridges across mental health disorders within their age and sex contexts. We present and analyze evidence from the literature for the critical roles circadian rhythmicity plays in regulating mental, emotional, and behavioral functions throughout the lifespan. A review of the literature shows that coarse CRD, such as sleep disruption, is prevalent in all mental health disorders at the level of etiological and pathophysiological mechanisms and clinical phenotypical manifestations. Finally, we discuss the subtle interplay of CRD with sex in relation to these disorders across different stages of life. Our perspective highlights the need to shift investigations towards molecular levels, for instance, by using spatiotemporal circadian "omic" studies in animal models to identify the complex and causal relationships between CRD and mental health disorders.

Impact of Chronic Prenatal Stress on Maternal Neuroendocrine Function and Embryo and Placenta Development During Early-to-Mid-Pregnancy in Mice

Psychological stress, both leading up to and during pregnancy, is associated with increased risk for negative pregnancy outcomes. Although the neuroendocrine circuits that link the stress response to reduced sexual motivation and mating are well-described, the specific pathways by which stress negatively impacts gestational outcomes remain unclear. Using a mouse model of chronic psychological stress during pregnancy, we investigated 1) how chronic exposure to stress during gestation impacts maternal reproductive neuroendocrine circuitry, and 2) whether stress alters developmental outcomes for the fetus or placenta by mid-pregnancy. Focusing on the stress-responsive neuropeptide RFRP-3, we identified novel contacts between RFRP-3-immunoreactive (RFRP-3-ir) cells and tuberoinfundibular dopaminergic neurons in the arcuate nucleus, thus providing a potential pathway linking the neuroendocrine stress response directly to pituitary prolactin production and release. However, neither of these cell populations nor circulating levels of pituitary hormones were affected by chronic stress. Conversely, circulating levels of steroid hormones relevant to gestational outcomes (progesterone and corticosterone) were altered in chronically-stressed dams across gestation, and those dams were qualitatively more likely to experience delays in fetal development. Together, these findings suggest that, up until at least mid-pregnancy, mothers appear to be relatively resilient to the effects of elevated glucocorticoids on reproductive neuroendocrine system function. We conclude that understanding how chronic psychological stress impacts reproductive outcomes will require understanding individual susceptibility and identifying reliable neuroendocrine changes resulting from gestational stress.

Early life circadian rhythm disruption in mice alters brain and behavior in adulthood

Healthy sleep supports robust development of the brain and behavior. Modern society presents a host of challenges that can impair and disrupt critical circadian rhythms that reinforce optimal physiological functioning, including the proper timing and consolidation of sleep. While the acute effects of inadequate sleep and disrupted circadian rhythms are being defined, the adverse developmental consequences of disrupted sleep and circadian rhythms are understudied. Here, we exposed mice to disrupting light–dark cycles from birth until weaning and demonstrate that such exposure has adverse impacts on brain and behavior as adults. Mice that experience early-life circadian disruption exhibit more anxiety-like behavior in the elevated plus maze, poorer spatial memory in the Morris Water Maze, and impaired working memory in a delayed match-to-sample task. Additionally, neuron morphology in the amygdala, hippocampus and prefrontal cortex is adversely impacted. Pyramidal cells in these areas had smaller dendritic fields, and pyramidal cells in the prefrontal cortex and hippocampus also exhibited diminished branching orders. Disrupted mice were also hyperactive as adults, but otherwise exhibited no alteration in adult circadian locomotor rhythms. These results highlight that circadian disruption early in life may have long lasting and far-reaching consequences for the development of behavior and the brain.

Tea combats circadian rhythm disorder syndrome via the gut-liver-brain axis: potential mechanisms speculated

Circadian rhythm is an intrinsic mechanism developed by organisms to adapt to external environmental signals. Nowadays, owing to the job and after-work entertainment, staying up late - Circadian rhythm disorders (CRD) are common. CRD is linked to the development of fatty liver, type 2 diabetes, and chronic gastroenteritis, which affecting the body's metabolic and inflammatory responses via multi-organ crosstalk (gut-liver-brain axis, etc.). However, studies on the mechanisms of multi-organ interactions by CRD are still weak. Current studies on therapeutic agents for CRD remain inadequate, and phytochemicals have been shown to alleviate CRD-induced syndromes that may be used for CRD-therapy in the future. Tea, a popular phytochemical-rich beverage, reduces glucolipid metabolism and inflammation. But it is immature and unclear in the mechanisms of alleviation of CRD-mediated syndrome. Here, we have analyzed the threat of CRD to hosts and their offspring' health from the perspective of the "gut-liver-brain" axis. The potential mechanisms of tea in alleviating CRD were further explored. It might be by interfering with bile acid metabolism, tryptophan metabolism, and G protein-coupled receptors, with FXR, AHR, and GPCR as potential targets. We hope to provide new perspectives on the role of tea in the prevention and mitigation of CRD.HighlightsThe review highlights the health challenges of CRD via the gut-liver-brain axis.CRD research should focus on the health effects on healthy models and its offspring.Tea may prevent CRD by regulating bile acid, tryptophan, and GPCR.Potential targets for tea prevention and mitigation of CRD include FXR, AHR and GPCR.A comprehensive assessment mechanism for tea in improving CRD should be established.

Effects of lighting patterns in pubertal development and metabolism of female wistar rats

Modern lifestyle is characterized by constant exposure to artificial light, which is associated with alterations in biological rhythms, abnormalities to reproductive cycles and metabolic changes. In this study, we aimed to evaluate the effects of four different lighting patterns on puberty timing and on possible metabolic changes in female Wistar rats. Additionally, we developed a machine learning algorithm to automatically classify the stages of the estrous cycle. Adult Wistar rats mated during a week at a photoperiod station where they were exposed to combined red-green-blue lights (RGB) during the photoperiod that varied its spectral composition (i.e., variable color temperature) during the day (RGB-v; N = 14), RGB during the photoperiod with a fixed light color temperature (RGB-f; N = 13) during the whole photoperiod; constant darkness (DD; N = 13) and constant fixed light (LL; N = 15). Experiments were performed only on female litters from postnatal day (PND) 22 to 50. Body weight, puberty onset, estrous cyclicity and serum metabolic parameters were measured. We also collected pictures of vaginal smears to create a dataset of 15,936 images to construct an automatic classifier based on convolutional neural networks. No significant differences were found in the age of vaginal opening; however, the RGB-v group showed a significantly lower number of complete and consecutives cycles. Also, the RGB-f group showed the first complete estrous cycle significantly earlier than the RGB-v group. Female rats housed in LL condition presented significantly lower mean body weight from PND 33 to PDN 47 compared to the other groups. Furthermore, higher levels of plasma triglycerides were found in the DD group compared to RGB-f and RGB-v. HDL levels were significantly lower in RGB-v compared to RGB-f and LL groups. Total cholesterol was significantly lower in RGB-v compared to all groups. Visceral fat was significantly higher in RGB-f compared to the LL group. These results suggest that both changes in photoperiod and lighting quality affect pubertal development and alter lipid profiles and visceral fat accumulation.

Maternal intermittent fasting during pregnancy: a translational research challenge for an important clinical scenario

In volume 135, issue 11 of Clinical Science, Alkhalefah et al. report that, in pregnant rats, repeated, cyclic fasting, mimicking the fasting experienced by observant Muslim pregnant women during Ramadan, alters placental amino acid transport and increases the incidence of low birth weight. Though Muslim women are exempt, many observe Ramadan: >500 million fetuses worldwide may be exposed to Ramadan fasting in each generation, and low birth weight increases the risk of developing chronic disease in the future adult. Several mechanisms, including altered circadian rhythm, maternal stress, undernutrition or compensatory overeating at the breaking of fast, could, in theory, impact fetal growth during Ramadan. Limitations of the experimental model obviously prevent direct extrapolation to humans. Whether Ramadan fasting indeed affect fetal growth therefore remains unclear, as there is no clear-cut evidence from epidemiological studies. The paper illustrates the need to design further case-controlled studies in large cohorts of women who fasted at various stages of pregnancy, compared to appropriately matched women who did not fast, as well as more experimental studies focused on this issue of public health relevance.

Disruption of circadian rhythm and risk of autism spectrum disorder: role of immune-inflammatory, oxidative stress, metabolic and neurotransmitter pathways

Circadian rhythms in most living organisms are regulated by light and synchronized to an endogenous biological clock. The circadian clock machinery is also critically involved in regulating and fine-tuning neurodevelopmental processes. Circadian disruption during embryonic development can impair crucial phases of neurodevelopment. This can contribute to neurodevelopmental disorders like autism spectrum disorder (ASD) in the offspring. Increasing evidence from studies showing abnormalities in sleep and melatonin as well as genetic and epigenetic changes in the core elements of the circadian pathway indicate a pivotal role of circadian disruption in ASD. However, the underlying mechanistic basis through which the circadian pathways influence the risk and progression of ASD are yet to be fully discerned. Well-recognized mechanistic pathways in ASD include altered immune-inflammatory, nitro oxidative stress, neurotransmission and synaptic plasticity, and metabolic pathways. Notably, all these pathways are under the control of the circadian clock. It is thus likely that a disrupted circadian clock will affect the functioning of these pathways. Herein, we highlight the possible mechanisms through which aberrations in the circadian clock might affect immune-inflammatory, nitro-oxidative, metabolic pathways, and neurotransmission, thereby driving the neurobiological sequelae leading to ASD.

Disruption of paternal circadian rhythm affects metabolic health in male offspring via nongerm cell factors

Circadian rhythm synchronizes each body function with the environment and regulates physiology. Disruption of normal circadian rhythm alters organismal physiology and increases disease risk. Recent epidemiological data and studies in model organisms have shown that maternal circadian disruption is important for offspring health and adult phenotypes. Less is known about the role of paternal circadian rhythm for offspring health. Here, we disrupted circadian rhythm in male mice by night-restricted feeding and showed that paternal circadian disruption at conception is important for offspring feeding behavior, metabolic health, and oscillatory transcription. Mechanistically, our data suggest that the effect of paternal circadian disruption is not transferred to the offspring via the germ cells but initiated by corticosterone-based parental communication at conception and programmed during in utero development through a state of fetal growth restriction. These findings indicate paternal circadian health at conception as a newly identified determinant of offspring phenotypes.

The trophoblast clock controls transport across placenta in mice

In mammals, 24-h rhythms of physiology and behavior are organized by a body-wide network of clock genes and proteins. Despite the well-known function of the adult circadian system, the roles of maternal, fetal and placental clocks during pregnancy are poorly defined. In the mature mouse placenta, the labyrinth zone (LZ) is of fetal origin and key for selective nutrient and waste exchange. Recently, clock gene expression has been detected in LZ and other fetal tissues; however, there is no evidence of a placental function controlled by the LZ clock. Here, we demonstrate that specifically the trophoblast layer of the LZ harbors an already functional clock by late gestation, able to regulate in a circadian manner the expression and activity of the xenobiotic efflux pump, ATP-binding cassette sub-family B member 1 (ABCB1), likely gating the fetal exposure to drugs from the maternal circulation to certain times of the day. As more than 300 endogenous and exogenous compounds are substrates of ABCB1, our results might have implications in choosing the maternal treatment time when aiming either maximal/minimal drug availability to the fetus/mother.

Light Environment Influences Developmental Programming of the Metabolic and Visual Systems in Mice

Purpose

Light is a salient cue that can influence neurodevelopment and the immune system. Light exposure out of sync with the endogenous clock causes circadian disruption and chronic disease. Environmental light exposure may contribute to developmental programming of metabolic and neurological systems but has been largely overlooked in Developmental Origins of Health and Disease (DOHaD) research. Here, we investigated whether developmental light exposure altered programming of visual and metabolic systems.

Methods

Pregnant mice and pups were exposed to control light (12:12 light:dark) or weekly light cycle inversions (circadian disruption [CD]) until weaning, after which male and female offspring were housed in control light and longitudinally measured to evaluate differences in growth (weight), glucose tolerance, visual function (optomotor response), and retinal function (electroretinogram), with and without high fat diet (HFD) challenge. Retinal microglia and macrophages were quantified by positive Iba1 and CD11b immunofluorescence.

Results

CD exposure caused impaired visual function and increased retinal immune cell expression in adult offspring. When challenged with HFD, CD offspring also exhibited altered retinal function and sex-specific impairments in glucose tolerance.

Conclusions

Overall, these findings suggest that the light environment contributes to developmental programming of the metabolic and visual systems, potentially promoting a pro-inflammatory milieu in the retina and increasing the risk of visual disease later in life.

Beginning to See the Light: Lessons Learned From the Development of the Circadian System for Optimizing Light Conditions in the Neonatal Intensive Care Unit

The circadian timing system optimizes health by temporally coordinating behavior and physiology. During mammalian gestation, fetal circadian rhythms are synchronized by the daily fluctuations in maternal body temperature, hormones and nutrients. Circadian disruption during pregnancy is associated with negative effects on developmental outcomes in the offspring, highlighting the importance of regular and robust 24-h rhythms over gestation. In the case of preterm birth (before 37 weeks of gestation), maternal cues no longer synchronize the neonate's circadian system, which may adversely affect the neonate. There is increasing evidence that introducing robust light-dark cycles in the Neonatal Intensive Care Unit has beneficial effects on clinical outcomes in preterm infants, such as weight gain and hospitalization time, compared to infants exposed to constant light or constant near-darkness. However, the biological basis for these effects and the relationship with the functional and anatomical development of the circadian system is not fully understood. In this review, we provide a concise overview of the effects of light-dark cycles on clinical outcomes of preterm neonates in the NICU and its alignment with the development of the circadian system.

Loss of circadian protection against influenza infection in adult mice exposed to hyperoxia as neonates

Adverse early-life exposures have a lasting negative impact on health. Neonatal hyperoxia that is a risk factor for bronchopulmonary dysplasia confers susceptibility to influenza A virus (IAV) infection later in life. Given our previous findings that the circadian clock protects against IAV, we asked if the long-term impact of neonatal hyperoxia vis-à-vis IAV infection includes circadian disruption. Here, we show that neonatal hyperoxia abolishes the clock-mediated time of day protection from IAV in mice, independent of viral burden through host tolerance pathways. We discovered that the lung intrinsic clock (and not the central or immune clocks) mediated this dysregulation. Loss of circadian protein, Bmal1, in alveolar type 2 (AT2) cells recapitulates the increased mortality, loss of temporal gating, and other key features of hyperoxia-exposed animals. Our data suggest a novel role for the circadian clock in AT2 cells in mediating long-term effects of early-life exposures to the lungs.

Feto-Maternal Crosstalk in the Development of the Circadian Clock System

The circadian (24 h) clock system adapts physiology and behavior to daily recurring changes in the environment. Compared to the extensive knowledge assembled over the last decades on the circadian system in adults, its regulation and function during development is still largely obscure. It has been shown that environmental factors, such as stress or alterations in photoperiod, disrupt maternal neuroendocrine homeostasis and program the offspring’s circadian function. However, the process of circadian differentiation cannot be fully dependent on maternal rhythms alone, since circadian rhythms in offspring from mothers lacking a functional clock (due to SCN lesioning or genetic clock deletion) develop normally. This mini-review focuses on recent findings suggesting that the embryo/fetal molecular clock machinery is present and functional in several tissues early during gestation. It is entrained by maternal rhythmic signals crossing the placenta while itself controlling responsiveness to such external factors to certain times of the day. The elucidation of the molecular mechanisms through which maternal, placental and embryo/fetal clocks interact with each other, sense, integrate and coordinate signals from the early life environment is improving our understanding of how the circadian system emerges during development and how it affects physiological resilience against external perturbations during this critical time period.

Challenging the Integrity of Rhythmic Maternal Signals Revealed Gene-Specific Responses in the Fetal Suprachiasmatic Nuclei

During fetal stage, maternal circadian system sets the phase of the developing clock in the suprachiasmatic nuclei (SCN) via complex pathways. We addressed the issue of how impaired maternal signaling due to a disturbed environmental light/dark (LD) cycle affects the fetal SCN. We exposed pregnant Wistar rats to two different challenges - a 6-h phase shift in the LD cycle on gestational day 14, or exposure to constant light (LL) throughout pregnancy - and detected the impact on gene expression profiles in 19-day-old fetuses. The LD phase shift, which changed the maternal SCN into a transient state, caused robust downregulation of expression profiles of clock genes (Per1, Per2, and Nr1d1), clock-controlled (Dbp) genes, as well as genes involved in sensing various signals, such as c-fos and Nr3c1. Removal of the rhythmic maternal signals via exposure of pregnant rats to LL abolished the rhythms in expression of c-fos and Nr3c1 in the fetal SCN. We identified c-fos as the gene primarily responsible for sensing rhythmic maternal signals because its expression profile tracked the shifted or arrhythmic maternal SCN clock. Pathways related to the maternal rhythmic behavioral state were likely not involved in driving the c-fos expression rhythm. Instead, introduction of a behavioral rhythm to LL-exposed mothers via restricted feeding regime strengthened rhythm in Vip expression in the fetal SCN. Our results revealed for the first time that the fetal SCN is highly sensitive in a gene-specific manner to various changes in maternal signaling due to disturbances of environmental cycles related to the modern lifestyle in humans.

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

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

The circadian phase of antenatal glucocorticoid treatment affects the risk of behavioral disorders

During pregnancy, maternal endocrine signals drive fetal development and program the offspring's physiology. A disruption of maternal glucocorticoid (GC) homeostasis increases the child's risk of developing psychiatric disorders later in life. We here show in mice, that the time of day of antenatal GC exposure predicts the behavioral phenotype of the adult offspring. Offspring of mothers receiving GCs out-of-phase compared to their endogenous circadian GC rhythm show elevated anxiety, impaired stress coping, and dysfunctional stress-axis regulation. The fetal circadian clock determines the vulnerability of the stress axis to GC treatment by controlling GC receptor (GR) availability in the hypothalamus. Similarly, a retrospective observational study indicates poorer stress compensatory capacity in 5-year old preterm infants whose mothers received antenatal GCs towards the evening. Our findings offer insights into the circadian physiology of feto-maternal crosstalk and assign a role to the fetal clock as a temporal gatekeeper of GC sensitivity.

Effects of sleep modulation during pregnancy in the mother and offspring: Evidences from preclinical research

Disturbed sleep during gestation may lead to adverse outcomes for both mother and child. Animal research plays an important role in providing insights into this research field by enabling ethical and methodological requirements that are not possible in humans. Here, we present an overview and discuss the main research findings related to the effects of prenatal sleep deprivation in animal models. Using systematic review approaches, we retrieved 42 articles dealing with some type of sleep alteration. The most frequent research topics in this context were maternal sleep deprivation, maternal behaviour, offspring behaviour, development of sleep-wake cycles in the offspring, hippocampal neurodevelopment, pregnancy viability, renal physiology, hypertension and metabolism. This overview indicates that the number of basic studies in this field is growing, and provides biological plausibility to suggest that sleep disturbances might be detrimental to both mother and offspring by promoting increased risk at the behavioural, hormonal, electrophysiological, metabolic and epigenetic levels. More studies on the effects of maternal sleep deprivation are needed, in light of their major translational perspective.

Epigenetic Regulation of Circadian Rhythm and Its Possible Role in Diabetes Mellitus

This review aims to summarize the knowledge about the relationship between circadian rhythms and their influence on the development of type 2 diabetes mellitus (T2DM) and metabolic syndrome. Circadian rhythms are controlled by internal molecular feedback loops that synchronize the organism with the external environment. These loops are affected by genetic and epigenetic factors. Genetic factors include polymorphisms and mutations of circadian genes. The expression of circadian genes is regulated by epigenetic mechanisms that change from prenatal development to old age. Epigenetic modifications are influenced by the external environment. Most of these modifications are affected by our own life style. Irregular circadian rhythm and low quality of sleep have been shown to increase the risk of developing T2DM and other metabolic disorders. Here, we attempt to provide a wide description of mutual relationships between epigenetic regulation, circadian rhythm, aging process and highlight new evidences that show possible therapeutic advance in the field of chrono-medicine which will be more important in the upcoming years.

Circadian rhythmicity of body temperature and metabolism

This article reviews the literature on the circadian rhythms of body temperature and whole-organism metabolism. The two rhythms are first described separately, each description preceded by a review of research methods. Both rhythms are generated endogenously but can be affected by exogenous factors. The relationship between the two rhythms is discussed next. In endothermic animals, modulation of metabolic activity can affect body temperature, but the rhythm of body temperature is not a mere side effect of the rhythm of metabolic thermogenesis associated with general activity. The circadian system modulates metabolic heat production to generate the body temperature rhythm, which challenges homeothermy but does not abolish it. Individual cells do not regulate their own temperature, but the relationship between circadian rhythms and metabolism at the cellular level is also discussed. Metabolism is both an output of and an input to the circadian clock, meaning that circadian rhythmicity and metabolism are intertwined in the cell.

Light and Circadian Signaling Pathway in Pregnancy: Programming of Adult Health and Disease

Light is a crucial environmental signal that affects elements of human health, including the entrainment of circadian rhythms. A suboptimal environment during pregnancy can increase the risk of offspring developing a wide range of chronic diseases in later life. Circadian rhythm disruption in pregnant women may have deleterious consequences for their progeny. In the modern world, maternal chronodisruption can be caused by shift work, jet travel across time zones, mistimed eating, and excessive artificial light exposure at night. However, the impact of maternal chronodisruption on the developmental programming of various chronic diseases remains largely unknown. In this review, we outline the impact of light, the circadian clock, and circadian signaling pathways in pregnancy and fetal development. Additionally, we show how to induce maternal chronodisruption in animal models, examine emerging research demonstrating long-term negative implications for offspring health following maternal chronodisruption, and summarize current evidence related to light and circadian signaling pathway targeted therapies in pregnancy to prevent the development of chronic diseases in offspring.

Pineal Neurosteroids: Biosynthesis and Physiological Functions

Similar to the adrenal glands, gonads, and placenta, vertebrate brains also produce various steroids, which are known as "neurosteroids." Neurosteroids are mainly synthesized in the hippocampus, hypothalamus, and cerebellum; however, it has recently been discovered that in birds, the pineal gland, a photosensitive region in the brain, produces more neurosteroids than other brain regions. A series of experiments using molecular and biochemical techniques have found that the pineal gland produces various neurosteroids, including sex steroids, de novo from cholesterol. For instance, allopregnanolone and 7α-hydroxypregnenolone are actively produced in the pineal gland, unlike in other brain regions. Pineal 7α-hydroxypregnenolone, an up-regulator of locomotion, enhances locomotor activity in response to light stimuli in birds. Additionally, pineal allopregnanolone acts on Purkinje cells in the cerebellum and prevents neuronal apoptosis within the developing cerebellum in juvenile birds. Furthermore, exposure to light during nighttime hours can cause loss of diurnal variations of pineal allopregnanolone synthesis during early posthatch life, eventually leading to cerebellar Purkinje cell death in juvenile birds. In light of these new findings, this review summarizes the biosynthesis and physiological functions of pineal neurosteroids. Given that the circadian rhythms of individuals in modern societies are constantly interrupted by artificial light exposure, these findings in birds, which are excellent model diurnal animals, may have direct implications for addressing problems regarding the mental health and brain development of humans.

Association of Iron Status and Intake During Pregnancy with Neuropsychological Outcomes in Children Aged 7 Years: The Prospective Birth Cohort Infancia y Medio Ambiente (INMA) Study

Early iron status plays an important role in prenatal neurodevelopment. Iron deficiency and high iron status have been related to alterations in child cognitive development; however, there are no data about iron intake during pregnancy with other environmental factors in relation to long term cognitive functioning of children. The aim of this study is to assess the relationship between maternal iron status and iron intake during pregnancy and child neuropsychological outcomes at 7 years of age. We used data from the INMA Cohort population-based study. Iron status during pregnancy was assessed according to serum ferritin levels, and iron intake was assessed with food frequency questionnaires. Working memory, attention, and executive function were assessed in children at 7 years old with the N-Back task, Attention Network Task, and the Trail Making Test, respectively. The results show that, after controlling for potential confounders, normal maternal serum ferritin levels (from 12 mg/L to 60 mg/L) and iron intake (from 14.5 mg/day to 30.0 mg/day), respectively, were related to better scores in working memory and executive functioning in offspring. Since these functions have been associated with better academic performance and adaptation to the environment, maintaining a good state of maternal iron from the beginning of pregnancy could be a valuable strategy for the community.

Light-at-night exposure affects brain development through pineal allopregnanolone-dependent mechanisms

The molecular mechanisms by which environmental light conditions affect cerebellar development are incompletely understood. We showed that circadian disruption by light-at-night induced Purkinje cell death through pineal allopregnanolone (ALLO) activity during early life in chicks. Light-at-night caused the loss of diurnal variation of pineal ALLO synthesis during early life and led to cerebellar Purkinje cell death, which was suppressed by a daily injection of ALLO. The loss of diurnal variation of pineal ALLO synthesis induced not only reduction in pituitary adenylate cyclase-activating polypeptide (PACAP), a neuroprotective hormone, but also transcriptional repression of the cerebellar Adcyap1 gene that produces PACAP, with subsequent Purkinje cell death. Taken together, pineal ALLO mediated the effect of light on early cerebellar development in chicks.

Maternal antenatal daytime sleepiness and child neuropsychiatric and neurocognitive development

BACKGROUND

The prevalence of sleep problems among pregnant women is over 50%, and daytime sleepiness is among the most common sleep problems. Previous studies have associated antenatal sleep problems with adverse maternal health and neonatal outcomes, but the consequences of antenatal sleep problems and particularly daytime sleepiness on child psychological development have not been assessed prospectively.

METHODS

In this prospective cohort study including 111 mother-child dyads, we examined the associations of maternal daytime sleepiness during pregnancy, assessed at 17 and 28 weeks of gestation using the Epworth Sleepiness Scale, with child neuropsychiatric problems and neuropsychological development, assessed with mother-rated questionnaires and individually administered neuropsychological tests, at child age 2.6-5.7 years (mean = 4.3 years).

RESULTS

Independently of sociodemographic and perinatal covariates and maternal depressive and anxiety symptoms during and/or after pregnancy, maternal antenatal daytime sleepiness was associated with increased total [unstandardized regression coefficient (B) = 0.25 standard deviation (s.d.) units; 95% confidence interval (CI) 0.01-0.48] and internalizing (B = 0.25 s.d.s: 95% CI 0.01-0.49) psychiatric problems and ADHD symptoms (B = 0.27 s.d.s: 95% CI 0.04-0.50) in children, and with poorer executive function, particularly in the areas of attention, working memory and inhibitory control (B = -0.39 s.d.s: 95% CI -0.69 to -0.10).

CONCLUSIONS

Maternal antenatal daytime sleepiness carries adverse consequences for offspring psychological development. The assessment of sleep problems may be an important addition to standard antenatal care.

Maternal circadian disruption is associated with variation in placental DNA methylation

Circadian disruption is a common environmental and occupational exposure with public health consequences, but not much is known about whether circadian disruption affects in utero development. We investigated whether maternal circadian disruption, using night shift work as a proxy, is associated with variations in DNA methylation patterns of placental tissue in an epigenome-wide association study (EWAS) of night shift work. Here, we compared cytosine-guanosine dinucleotide (CpG) specific methylation genome-wide of placental tissue (measured with the Illumina 450K array) from participants (n = 237) in the Rhode Island Child Health Study (RICHS) who did (n = 53) and did not (n = 184) report working the night shift, using robust linear modeling and adjusting for maternal age, pre-pregnancy smoking, infant sex, maternal adversity, and putative cell mixture. Statistical analyses were adjusted for multiple comparisons and results presented with Bonferroni or Benjamini and Hochberg (BH) adjustment for false discovery rate. Night shift work was associated with differential methylation in placental tissue, including CpG sites in the genes NAV1, SMPD1, TAPBP, CLEC16A, DIP2C, FAM172A, and PLEKHG6 (Bonferroni-adjusted p<0.05). CpG sites within NAV1, MXRA8, GABRG1, PRDM16, WNT5A, and FOXG1 exhibited the most hypomethylation, while CpG sites within TDO2, ADAMTSL3, DLX2, and SERPINA1 exhibited the most hypermethylation (BH q<0.10). Functional analysis indicated GO-terms associated with cell-cell adhesion and enriched GWAS results for psoriasis. Night shift work was associated with differential methylation of the placenta, which may have implications for fetal health and development. This is the first study to examine the epigenetic impacts of night shift exposure, as a proxy for circadian disruption, on placental methylation in humans, and, while results should be interpreted with caution, suggests circadian disruption may have epigenetic impacts.

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

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

Rhythms of life: circadian disruption and brain disorders across the lifespan

Many processes in the human body - including brain function - are regulated over the 24-hour cycle, and there are strong associations between disrupted circadian rhythms (for example, sleep-wake cycles) and disorders of the CNS. Brain disorders such as autism, depression and Parkinson disease typically develop at certain stages of life, and circadian rhythms are important during each stage of life for the regulation of processes that may influence the development of these disorders. Here, we describe circadian disruptions observed in various brain disorders throughout the human lifespan and highlight emerging evidence suggesting these disruptions affect the brain. Currently, much of the evidence linking brain disorders and circadian dysfunction is correlational, and so whether and what kind of causal relationships might exist are unclear. We therefore identify remaining questions that may direct future research towards a better understanding of the links between circadian disruption and CNS disorders.

Perinatal Programming of Circadian Clock-Stress Crosstalk

An intact communication between circadian clocks and the stress system is important for maintaining physiological homeostasis under resting conditions and in response to external stimuli. There is accumulating evidence for a reciprocal interaction between both-from the systemic to the molecular level. Disruption of this interaction by external factors such as shiftwork, jetlag, or chronic stress increases the risk of developing metabolic, immune, or mood disorders. From experiments in rodents, we know that both systems maturate during the perinatal period. During that time, exogenous factors such as stress or alterations in the external photoperiod may critically affect-or program-physiological functions later in life. This developmental programming process has been attributed to maternal stress signals reaching the embryo, which lastingly change gene expression through the induction of epigenetic mechanisms. Despite the well-known function of the adult circadian system in temporal coordination of physiology and behavior, the role of maternal and embryonic circadian clocks during pregnancy and postnatal development is still poorly defined. A better understanding of the circadian-stress crosstalk at different periods of development may help to improve stress resistance and devise preventive and therapeutic strategies against chronic stress-associated disorders.