Chronobiology in the endocrine system

Spexin acts as a novel glucose-lowering factor in grass carp (Ctenopharyngodon idella)

At present, the physiological roles of various hormones in fish glucose metabolism have been elucidated. Spexin, a 14-amino acids polypeptide, is highly conserved in many species and has functions such as reducing body weight and improving insulin resistance. In this paper, the open reading frame (ORF) of spx21 in grass carp (Ctenopharyngodon idella) was cloned, and the tissue distribution of spx1 and spx2, their direct and indirect regulatory effects on glucose metabolism of grass carp were investigated. The ORF of spx2 gene in grass carp was 279 bp in length. Moreover, spx1 was highly expressed in the adipose tissue, while spx2 was highly expressed in the brain. In vitro, SPX1 and SPX2 showed opposite effects on the glycolytic pathway in the primary hepatocytes. In vivo, intraperitoneal injection of SPX1 and SPX2 significantly reduced serum glucose levels and increased hepatopancreas glycogen contents. Meanwhile, SPX1 and SPX2 promoted the expression of key genes of glycolysis (pk) and glycogen synthesis (gys) in the hepatopancreas at 3 h post injection. As for indirect effects, 1000 nM SPX1 and SPX2 significantly increased insulin-mediated liver type phosphofructokinase (pfkla) mRNA expression and enhanced the inhibitory effects of insulin on glucose-6-phosphatase (g6pase), phosphoenolpyruvate carboxykinase (pepck), glycogen phosphorylase L (pygl) mRNA expression. Our results show that SPX1 and SPX2 have similar indirect effects on the regulation of glucose metabolism that enhance insulin activity, but they exhibit opposite roles in terms of direct effects.

Alterations in Circadian Rhythms, Sleep, and Physical Activity in COVID-19: Mechanisms, Interventions, and Lessons for the Future

Although the world is acquitting from the throes of COVID-19 and returning to the regularity of life, its effects on physical and mental health are prominently evident in the post-pandemic era. The pandemic subjected us to inadequate sleep and physical activities, stress, irregular eating patterns, and work hours beyond the regular rest-activity cycle. Thus, perturbing the synchrony of the regular circadian clock functions led to chronic psychiatric and neurological disorders and poor immunological response in several COVID-19 survivors. Understanding the links between the host immune system and viral replication machinery from a clock-infection biology perspective promises novel avenues of intervention. Behavioral improvements in our daily lifestyle can reduce the severity and expedite the convalescent stage of COVID-19 by maintaining consistent eating, sleep, and physical activity schedules. Including dietary supplements and nutraceuticals with prophylactic value aids in combating COVID-19, as their deficiency can lead to a higher risk of infection, vulnerability, and severity of COVID-19. Thus, besides developing therapeutic measures, perpetual healthy practices could also contribute to combating the upcoming pandemics. This review highlights the impact of the COVID-19 pandemic on biological rhythms, sleep-wake cycles, physical activities, and eating patterns and how those disruptions possibly contribute to the response, severity, and outcome of SARS-CoV-2 infection.

Sleep promotes T-cell migration towards CCL19 via growth hormone and prolactin signaling in humans

Sleep strongly supports the formation of adaptive immunity, e.g., after vaccination. However, the underlying mechanisms remain largely obscure. Here we show in healthy humans that sleep compared to nocturnal wakefulness specifically promotes the migration of various T-cell subsets towards the chemokine CCL19, which is essential for lymph-node homing and, thus, for the initiation and maintenance of adaptive immune responses. Migration towards the inflammatory chemokine CCL5 remained unaffected. Incubating the cells with plasma from sleeping participants likewise increased CCL19-directed migration, an effect that was dependent on growth hormone and prolactin signaling. These findings show that sleep selectively promotes the lymph node homing potential of T cells by increasing hormonal release, and thus reveal a causal mechanism underlying the supporting effect of sleep on adaptive immunity in humans.

Chrono-Endocrinology in Clinical Practice: A Journey from Pathophysiological to Therapeutic Aspects

This review was aimed at collecting the knowledge on the pathophysiological and clinical aspects of endocrine rhythms and their implications in clinical practice, derived from the published literature and from some personal experiences on this topic. We chose to review, according to the PRISMA guidelines, the results of original and observational studies, reviews, meta-analyses and case reports published up to March 2024. Thus, after summarizing the general aspects of biological rhythms, we will describe the characteristics of several endocrine rhythms and the consequences of their disruption, paying particular attention to the implications in clinical practice. Rhythmic endocrine secretions, like other physiological rhythms, are genetically determined and regulated by a central hypothalamic CLOCK located in the suprachiasmatic nucleus, which links the timing of the rhythms to independent clocks, in a hierarchical organization for the regulation of physiology and behavior. However, some environmental factors, such as daily cycles of light/darkness, sleep/wake, and timing of food intake, may influence the rhythm characteristics. Endocrine rhythms are involved in important physiological processes and their disruption may cause several disorders and also cancer. Thus, it is very important to prevent disruptions of endocrine rhythms and to restore a previously altered rhythm by an early corrective chronotherapy.

Subarachnoid Haemorrhage Incidence Pattern Analysis with Circular Statistics

Knowledge about biological rhythms of diseases may not only help in understanding the pathophysiology of diseases but can also help health service policy makers and emergency department directors to allocate resources efficiently. Aneurysmal subarachnoid haemorrhage (SAH) has high rates of morbidity and mortality. The incidence of SAH has been attributed to patient-related factors such as characteristics of aneurysms, smoking, and hypertension. There are studies showing that the incidence of aneurysmal SAH appears to behave in periodic fashions over long time periods. However, there are inconsistencies in the literature regarding the impact of chronobiological factors such as circadian, seasonal, and lunar cycle factors on the occurrence of SAH. In this study, we focused on the analysis of a temporal pattern of SAH (infradian rhythms) with a novel approach using circular statistical methods. We aimed to see whether there is a circular pattern for the occurrence of SAH at all and if so, whether it can be related to known temporal patterns based on available literature. Our study did not support the notion that aneurysmal subarachnoid haemorrhages occur on any specific day in a cycle with specific lengths up to 365 days including specific weekdays, full moon, equinoxes, and solstices. Hence, we found no relationship between SAH incidence and timing. Study in larger populations using similar circular statistical methods is suggested.

Chrono-nutrition for hypertension

Despite the advancement in blood pressure (BP) lowering medications, uncontrolled hypertension persists, underscoring a stagnation of effective clinical strategies. Novel and effective lifestyle therapies are needed to prevent and manage hypertension to mitigate future progression to cardiovascular and chronic kidney diseases. Chrono-nutrition, aligning the timing of eating with environmental cues and internal biological clocks, has emerged as a potential strategy to improve BP in high-risk populations. The aim of this review is to provide an overview of the circadian physiology of BP with an emphasis on renal and vascular circadian biology. The potential of Chrono-nutrition as a lifestyle intervention for hypertension is discussed and current evidence for the efficacy of time-restricted eating is presented.

The Physiological and Pharmacological Significance of the Circadian Timing of the HPA Axis: A Mathematical Modeling Approach

As a potent endogenous regulator of homeostasis, the circadian time-keeping system synchronizes internal physiology to periodic changes in the external environment to enhance survival. Adapting endogenous rhythms to the external time is accomplished hierarchically with the central pacemaker located in the suprachiasmatic nucleus (SCN) signaling the hypothalamus-pituitary-adrenal (HPA) axis to release hormones, notably cortisol, which help maintain the body's circadian rhythm. Given the essential role of HPA-releasing hormones in regulating physiological functions, including immune response, cell cycle, and energy metabolism, their daily variation is critical for the proper function of the circadian timing system. In this review, we focus on cortisol and key fundamental properties of the HPA axis and highlight their importance in controlling circadian dynamics. We demonstrate how systems-driven, mathematical modeling of the HPA axis complements experimental findings, enhances our understanding of complex physiological systems, helps predict potential mechanisms of action, and elucidates the consequences of circadian disruption. Finally, we outline the implications of circadian regulation in the context of personalized chronotherapy. Focusing on the chrono-pharmacology of synthetic glucocorticoids, we review the challenges and opportunities associated with moving toward personalized therapies that capitalize on circadian rhythms.

Time-restricted eating for chronodisruption-related chronic diseases

The circadian timing system enables organisms to adapt their physiology and behavior to the cyclic environmental changes including light-dark cycle or food availability. Misalignment between the endogenous circadian rhythms and external cues is known as chronodisruption and is closely associated with the development of metabolic and gastrointestinal disorders, cardiovascular diseases, and cancer. Time-restricted eating (TRE, in human) is an emerging dietary approach for weight management. Recent studies have shown that TRE or time-restricted feeding (TRF, when referring to animals) has several beneficial health effects, which, however, are not limited to weight management. This review summarizes the effects of TRE/TRF on regulating energy metabolism, gut microbiota and homeostasis, development of cardiovascular diseases and cancer. Furthermore, we will address the role of circadian clocks in TRE/TRF and propose ways to optimize TRE as a dietary strategy to obtain maximal health benefits.

Enhancing precision in human neuroscience

Human neuroscience has always been pushing the boundary of what is measurable. During the last decade, concerns about statistical power and replicability - in science in general, but also specifically in human neuroscience - have fueled an extensive debate. One important insight from this discourse is the need for larger samples, which naturally increases statistical power. An alternative is to increase the precision of measurements, which is the focus of this review. This option is often overlooked, even though statistical power benefits from increasing precision as much as from increasing sample size. Nonetheless, precision has always been at the heart of good scientific practice in human neuroscience, with researchers relying on lab traditions or rules of thumb to ensure sufficient precision for their studies. In this review, we encourage a more systematic approach to precision. We start by introducing measurement precision and its importance for well-powered studies in human neuroscience. Then, determinants for precision in a range of neuroscientific methods (MRI, M/EEG, EDA, Eye-Tracking, and Endocrinology) are elaborated. We end by discussing how a more systematic evaluation of precision and the application of respective insights can lead to an increase in reproducibility in human neuroscience.

Risk taking for potential losses but not gains increases with time of day

Humans exhibit distinct risk preferences when facing choices involving potential gains and losses. These preferences are believed to be subject to neuromodulatory influence, particularly from dopamine and serotonin. As neuromodulators manifest circadian rhythms, this suggests decision making under risk might be affected by time of day. Here, in a large subject sample collected using a smartphone application, we found that risky options with potential losses were increasingly chosen over the course of the day. We observed this result in both a within-subjects design (N = 2599) comparing risky options chosen earlier and later in the day in the same individuals, and in a between-subjects design (N = 26,720) showing our effect generalizes across ages and genders. Using computational modelling, we show this diurnal change in risk preference reflects a decrease in sensitivity to increasing losses, but no change was observed in the relative impacts of gains and losses on choice (i.e., loss aversion). Thus, our findings reveal a striking diurnal modulation in human decision making, a pattern with potential importance for real-life decisions that include voting, medical decisions, and financial investments.

Physiological Rhythms and Biological Variation of Biomolecules: The Road to Personalized Laboratory Medicine

The concentration of biomolecules in living systems shows numerous systematic and random variations. Systematic variations can be classified based on the frequency of variations as ultradian (<24 h), circadian (approximately 24 h), and infradian (>24 h), which are partly predictable. Random biological variations are known as between-subject biological variations that are the variations among the set points of an analyte from different individuals and within-subject biological variation, which is the variation of the analyte around individuals’ set points. The random biological variation cannot be predicted but can be estimated using appropriate measurement and statistical procedures. Physiological rhythms and random biological variation of the analytes could be considered the essential elements of predictive, preventive, and particularly personalized laboratory medicine. This systematic review aims to summarize research that have been done about the types of physiological rhythms, biological variations, and their effects on laboratory tests. We have searched the PubMed and Web of Science databases for biological variation and physiological rhythm articles in English without time restrictions with the terms “Biological variation, Within-subject biological variation, Between-subject biological variation, Physiological rhythms, Ultradian rhythms, Circadian rhythm, Infradian rhythms”. It was concluded that, for effective management of predicting, preventing, and personalizing medicine, which is based on the safe and valid interpretation of patients’ laboratory test results, both physiological rhythms and biological variation of the measurands should be considered simultaneously.

Advances in circadian clock regulation of reproduction

The mammalian circadian clock is an endogenously regulated oscillator that is synchronized with solar time and cycle within a 24-h period. The circadian clock exists not only in the suprachiasmatic nucleus (SCN) of the hypothalamus, a central pacemaker of the circadian clock system, but also in numerous peripheral tissues known as peripheral circadian oscillators. The SCN and peripheral circadian oscillators mutually orchestrate the diurnal rhythms of various physiological and behavioral processes in a hierarchical manner. In the past two decades, peripheral circadian oscillators have been identified and their function has been determined in the mammalian reproductive system and its related endocrine glands, including the hypothalamus, pituitary gland, ovaries, testes, uterus, mammary glands, and prostate gland. Increasing evidence indicates that both the SCN and peripheral circadian oscillators play discrete roles in coordinating reproductive processes and optimizing fertility in mammals. The present study reviews recent evidence on circadian clock regulation of reproductive function in the hypothalamic-pituitary-gonadal axis and reproductive system. Additionally, we elucidate the effects of chronodisruption (as a result of, for example, shift work, jet lag, disrupted eating patterns, and sleep disorders) on mammalian reproductive performance from multiple aspects. Finally, we propose potential behavioral changes or pharmaceutical strategies for the prevention and treatment of reproductive disorders from the perspective of chronomedicine. Conclusively, this review will outline recent evidence on circadian clock regulation of reproduction, providing novel perspectives on the role of the circadian clock in maintaining normal reproductive functions and in diseases that negatively affect fertility.

Perspectives of colon-specific drug delivery in the management of morning symptoms of rheumatoid arthritis

Rheumatoid arthritis is a chronic condition that is characterized by joint pain and inflammation. It is an autoimmune disorder in which the body tissues are erroneously attacked by the immune system of the host itself. It has been evident that rheumatoid arthritis symptoms follow a 24 h circadian rhythm and exhibit high thresholds of pain, functional disability, and stiffness predominantly early in the morning. Colon-specific drug delivery systems can be utilized in the formulations to be used in the treatment of rheumatoid arthritis. The colon-specific drug delivery system has shown promising results in the treatment of different diseases at the colonic site like Crohn's disease, ulcerative colitis, colon cancer, etc. The colon-specific drug delivery is capable of delivering the formulation at the predetermined location and predetermined time. The early morning symptoms of rheumatoid arthritis like pain and inflammation can be treated using the various approaches of the colon-specific drug delivery system because it will lead to patient compliance as the patient will not require administering the formulation immediately after waking up in the morning. This review also explains the immunological factors which may trigger rheumatoid arthritis in human beings. It further explores conventional approaches like pH-dependant, microorganisms-driven, pressure-controlled, and time-dependant formulations. By employing two or more conventional approaches given above the various novel approaches have been designed to eliminate the drawbacks of individual techniques.

Does Patient-Applied Testosterone Replacement Therapy Pose Risk for Blood Pressure Elevation? Circadian Medicine Perspectives

We reviewed medication package inserts, US Food and Drug Administration (FDA) reports, and journal publications concerning the 10 nonbiosimilar patient-applied (PA) testosterone (T) replacement therapies (TRTs) for intraday serum T patterning and blood pressure (BP) effects. Blood T concentration is circadian rhythmic in young adult eugonadal males, being highest around awakening and lowest before bedtime. T level and 24 h variation are blunted in primary and secondary hypogonadism. Utilized as recommended, most PA-TRTs achieve nonphysiologic T 24 h patterning. Only Androderm^® , an evening PA transdermal patch, closely replicates the normal T circadian rhythmicity. Accurate determination of risk for BP elevation and hypertension (HTN) by PA-TRTs is difficult due to limitations of office BP measurements (OBPM) and suboptimal methods and endpoints of ambulatory BP monitoring (ABPM). OBPM is subject to "White Coat" pressor effect resulting in unrepresentative BP values plus masked normotension and masked HTN, causing misclassification of approximately 45% of trial participants, both before and during treatment. Change in guideline-recommended diagnostic thresholds over time causes misclassification of an additional approximately 15% of participants. ABPM is improperly incorporated into TRT safety trials. It is done for 24 h rather than preferred 48 h; BP is oversampled during wakefulness, biasing derived 24 h mean values; 24 h mean systolic and diastolic BP (SBP, DBP) are inappropriate primary outcomes, because of not being best predictors of risk for major acute cardiovascular events (MACE); "daytime" and "nighttime" BP means referenced to clock time are reported rather than biologically relevant wake-time and sleep-time BP means; most importantly, asleep SBP mean and dipping, strongest predictors of MACE, are disregarded. © 2022 American Physiological Society. Compr Physiol 12: 1-20, 2022.

Gastrointestinal tract-based implicit measures for cognition, emotion and behavior

Implicit physiological measures such as heart rate and skin conductance convey information about someone's cognitive or affective state. Currently, gastrointestinal (GI) tract-based markers are not yet considered while both the organs involved as well as the microbiota populating the GI tract are bidirectionally connected to the brain and have a relation to emotion, cognition and behavior. This makes GI tract-based measures relevant and interesting, especially because the relation may be causal, and because they have a different timescale than current physiological measures. This perspective paper (1) presents the (mechanistic) involvement of the GI tract and its microbiota in emotion, cognition and behavior; (2) explores the added value of microbiome-based implicit measures as complementary to existing measures; and (3) sets the priorities to move forward. Five potential measures are proposed and discussed in more detail: bowel movement, short-chain fatty acids, tyrosine and tryptophan, GI tract flora composition, and cytokine levels. We conclude (1) that the involvement of the GI tract in emotion, cognition and behavior is undisputed, (2) that GI tract-based implicit measures are still in a conceptual phase of development but show potential and (3) that the first step to bring this field forward is to start validation studies in healthy humans and that are designed in the context of implicit measurements.

Blood hormones and suicidal behaviour: A systematic review and meta-analysis

This study was to evaluate the relationship between blood hormone levels and suicidal behaviour. We reviewed Web of Science, PubMed and Embase for literature published up to 10 April 2022. Studies were restricted to English-language articles. Studies measuring blood hormone levels in suicidal and non-suicidal subjects were eligible. Standardized mean differences (SMDs) were applied to evaluate group differences. Overall, 57 studies were eligible, of which 51 evaluated suicide attempts, and 9 assessed suicidal ideation. Random-effects meta-analysis indicated that levels of thyrotropin stimulating hormone (TSH) (SMD = 0.50; 95% CI, 0.27-0.72), leptin (SMD = -1.16; 95% CI, -1.94 to -0.38) and dehydroepiandrosterone sulfate (DHEAS) (SMD = -0.67; 95% CI, -1.13 to -0.21) were related to suicide attempts, whereas progesterone levels (SMD = 0.22; 95% CI, 0.03-0.41) were related to suicidal ideation. This analysis offers evidence linking abnormalities of blood hormones with suicidal behaviour, which may be essential for identifying individuals with suicide attempts and suicidal ideation. Large prospective studies are needed for further clarification of roles of hormones in suicidal behaviour.

HBM4EU Chromates Study: Urinary Metabolomics Study of Workers Exposed to Hexavalent Chromium

Exposure to hexavalent chromium Cr(VI) may occur in several occupational activities, placing workers in many industries at risk for potential related health outcomes. Untargeted metabolomics was applied to investigate changes in metabolic pathways in response to Cr(VI) exposure. We obtained our data from a study population of 220 male workers with exposure to Cr(VI) and 102 male controls from Belgium, Finland, Poland, Portugal and the Netherlands within the HBM4EU Chromates Study. Urinary metabolite profiles were determined using liquid chromatography mass spectrometry, and differences between post-shift exposed workers and controls were analyzed using principal component analysis. Based on the first two principal components, we observed clustering by industrial chromate application, such as welding, chrome plating, and surface treatment, distinct from controls and not explained by smoking status or alcohol use. The changes in the abundancy of excreted metabolites observed in workers reflect fatty acid and monoamine neurotransmitter metabolism, oxidative modifications of amino acid residues, the excessive formation of abnormal amino acid metabolites and changes in steroid and thyrotropin-releasing hormones. The observed responses could also have resulted from work-related factors other than Cr(VI). Further targeted metabolomics studies are needed to better understand the observed modifications and further explore the suitability of urinary metabolites as early indicators of adverse effects associated with exposure to Cr(VI).

Gut Seasons: Photoperiod Effects on Fecal Microbiota in Healthy and Cafeteria-Induced Obese Fisher 344 Rats

Gut microbiota and biological rhythms are emerging as key factors in the modulation of several physiological and metabolic processes. However, little is known about their interaction and how this may affect host physiology and metabolism. Several studies have shown oscillations of gut microbiota that follows a circadian rhythmicity, but, in contrast, variations due to seasonal rhythms have not been sufficiently investigated yet. Thus, the goal of this study was to investigate the impact of different photoperiods, which mimic seasonal changes, on fecal microbiota composition and how this interaction affects diet-induced obesity development. To this aim, Fisher 344 male rats were housed under three photoperiods (L6, L12 and L18) and fed with standard chow diet or cafeteria diet (CAF) for 9 weeks. The 16S ribosomal sequencing of collected fecal samples was performed. The photoperiod exposure significantly altered the fecal microbiota composition under L18, especially in CAF-fed rats. Moreover, these alterations were associated with changes in body weight gain and different fat parameters. These findings suggest a clear impact of seasonal rhythms on gut microbiota, which ultimately translates into different susceptibilities to diet-induced obesity development. This is the first time to our knowledge that the photoperiod impact on gut microbiota composition has been described in an obesity context although further studies are needed in order to elucidate the mechanisms involved.

Potential effects of shift work on skin autoimmune diseases

Shift work is associated with systemic chronic inflammation, impaired host and tumor defense and dysregulated immune responses to harmless antigens such as allergens or auto-antigens. Thus, shift workers are at higher risk to develop a systemic autoimmune disease and circadian disruption with sleep impairment seem to be the key underlying mechanisms. Presumably, disturbances of the sleep-wake cycle also drive skin-specific autoimmune diseases, but epidemiological and experimental evidence so far is scarce. This review summarizes the effects of shift work, circadian misalignment, poor sleep, and the effect of potential hormonal mediators such as stress mediators or melatonin on skin barrier functions and on innate and adaptive skin immunity. Human studies as well as animal models were considered. We will also address advantages and potential pitfalls in animal models of shift work, and possible confounders that could drive skin autoimmune diseases in shift workers such as adverse lifestyle habits and psychosocial influences. Finally, we will outline feasible countermeasures that may reduce the risk of systemic and skin autoimmunity in shift workers, as well as treatment options and highlight outstanding questions that should be addressed in future studies.

Alterations of sleep quality and circadian rhythm genes expression in elderly thyroid nodule patients and risks associated with thyroid malignancy

To study the alterations of sleep quality and circadian rhythm genes expressions upon elderly thyroid nodule patients, the risk factors associated with thyroid malignancies, and the potential relationship involved. The elderly people enrolled in our study were divided into three groups according to the thyroid histopathology: malignant nodule group, benign nodule group, and normal group, and the clinical data and sleep quality were collected. Among the patients of surgery, 56 fresh thyroid tissues were collected for real-time PCR, immunohistochemistry and western blotting analysis of CLOCK, BMAL1, CRYs and PERs. Poor sleep quality, sleep latency and daytime dysfunction were the independent risk factors of malignant nodule after adjusted by other impacts. The expression levels of CLOCK, BMAL1 and PER2 in thyroid malignant group were significantly higher than benign and normal groups, while CRY2 was decreased, p < 0.05. In addition, CLOCK and BMAL1 protein levels were positively correlated with PSQI of corresponding patients and CRY2 was negatively correlated. Circadian rhythm genes mainly altered in malignant nodules, and sleep disorders may be involved in the occurrence of elderly thyroid malignancy through the high expressions of CLOCK and BMAL1, and low expression of CRY2.

Chronothyroidology: Chronobiological Aspects in Thyroid Function and Diseases

Chronobiology is the scientific discipline which considers biological phenomena in relation to time, which assumes itself biological identity. Many physiological processes are cyclically regulated by intrinsic clocks and many pathological events show a circadian time-related occurrence. Even the pituitary–thyroid axis is under the control of a central clock, and the hormones of the pituitary–thyroid axis exhibit circadian, ultradian and circannual rhythmicity. This review, after describing briefly the essential principles of chronobiology, will be focused on the results of personal experiences and of other studies on this issue, paying particular attention to those regarding the thyroid implications, appearing in the literature as reviews, metanalyses, original and observational studies until 28 February 2021 and acquired from two databases (Scopus and PubMed). The first input to biological rhythms is given by a central clock located in the suprachiasmatic nucleus (SCN), which dictates the timing from its hypothalamic site to satellite clocks that contribute in a hierarchical way to regulate the physiological rhythmicity. Disruption of the rhythmic organization can favor the onset of important disorders, including thyroid diseases. Several studies on the interrelationship between thyroid function and circadian rhythmicity demonstrated that thyroid dysfunctions may affect negatively circadian organization, disrupting TSH rhythm. Conversely, alterations of clock machinery may cause important perturbations at the cellular level, which may favor thyroid dysfunctions and also cancer.

Gestational diabetes, environmental temperature and climate factors - From epidemiological evidence to physiological mechanisms

Gestational diabetes (GDM) is a common metabolic complication of pregnancy that is generally asymptomatic in its clinical course, although it is potentially associated with a wide range of both maternal and foetal complications. The population prevalence of GDM varies widely, depending on the clinical diagnostic criteria, ethnicity, demographics and background prevalence of type 2 diabetes. Climate variability and environmental temperature have recently come to the forefront as potential direct or indirect determinants of human health. The association between GDM and environmental temperature is complex, and studies have often reported conflicting findings. Epidemiologic studies have shown a direct relation between rising environmental temperature and the risk of both GDM and impaired beta cell function. Seasonal trends in the prevalence of GDM have been reported in several populations, with a higher prevalence in summer months. Multiple mechanisms have been proposed to explain the GDM-temperature correlation. A growing body of evidence supports a link between temperature, energy expenditure and adipose tissue metabolism. Brown adipose tissue thermogenesis, induced by cold temperatures, improves insulin sensitivity. Further biological explanations for the GDM-temperature correlation lie in potential association with low vitamin D levels, which varies according to sunshine exposure. Observational studies are also complicated by lifestyle factors, such as diet and physical activity, that could exhibit seasonal variation. In this review article, we provide a systematic overview of available epidemiological evidence linking environmental temperature and gestational diabetes. Furthermore, the physiological mechanisms that give biological plausibility to association between GDM and temperature are explored. As future climate patterns could drive global changes in GDM prevalence, this knowledge has important implications for both clinicians and researchers.

Circadian Effects of Drug Responses

Circadian rhythms describe physiological systems that repeat themselves with a cycle of approximately 24 h. Our understanding of the cellular and molecular origins of these oscillations has improved dramatically, allowing us to appreciate the significant role these oscillations play in maintaining physiological homeostasis. Circadian rhythms allow living organisms to predict and efficiently respond to a dynamically changing environment, set by repetitive day/night cycles. Since circadian rhythms underlie almost every aspect of human physiology, it is unsurprising that they also influence the response of a living organism to disease, stress, and therapeutics. Therefore, not only do the mechanisms that maintain health and disrupt homeostasis depend on our internal circadian clock, but also the way drugs are perceived and function depends on these physiological rhythms. We present a holistic view of the therapeutic process, discussing components such as disease state, pharmacokinetics, and pharmacodynamics, as well as adverse reactions that are critically affected by circadian rhythms. We outline challenges and opportunities in moving toward personalized medicine approaches that explore and capitalize on circadian rhythms for the benefit of the patient.

Adropin as a potential mediator of the metabolic system-autonomic nervous system-chronobiology axis: Implementing a personalized signature-based platform for chronotherapy

Adropin is a peptide hormone, which plays a role in energy homeostasis and controls glucose and fatty acid metabolism. Its levels correlate with changes in carbohydrate-lipid metabolism, metabolic diseases, central nervous system function, endothelial function and cardiovascular disease. Both metabolic pathways and adropin are regulated by the circadian clocks. Here, we review the roles of the autonomic nervous system and circadian rhythms in regulating metabolic pathways and energy homeostasis. The beneficial effects of chronotherapy in various systems are discussed. We suggest a potential role for adropin as a mediator of the metabolic system-autonomic nervous system axis. We discuss the possibility of establishing an individualized adropin and circadian rhythm-based platform for implementing chronotherapy, and variability signatures for improving the efficacy of adropin-based therapies are discussed.

Circadian rhythms and the HPA axis: A systems view

The circadian timing system comprises a network of time-keeping clocks distributed across a living host whose responsibility is to allocate resources and distribute functions temporally to optimize fitness. The molecular structures generating these rhythms have evolved to accommodate the rotation of the earth in an attempt to primarily match the light/dark periods during the 24-hr day. To maintain synchrony of timing across and within tissues, information from the central clock, located in the suprachiasmatic nucleus, is conveyed using systemic signals. Leading among those signals are endocrine hormones, and while the hypothalamic-pituitary-adrenal axis through the release of glucocorticoids is a major pacesetter. Interestingly, the fundamental units at the molecular and physiological scales that generate local and systemic signals share critical structural properties. These properties enable time-keeping systems to generate rhythmic signals and allow them to adopt specific properties as they interact with each other and the external environment. The purpose of this review is to provide a broad overview of these structures, discuss their functional characteristics, and describe some of their fundamental properties as these related to health and disease. This article is categorized under: Immune System Diseases > Computational Models Immune System Diseases > Biomedical Engineering.

Cell Autonomous Circadian Systems and Their Relation to Inflammation

All living beings on earth have an important mechanism of 24-h periodicity, which controls their physiology, metabolism, and behavior. In humans, 24-h periodicity is regulated by the superchiasmatic nucleus (SCN) through external and environmental cues. Peripheral organs demonstrate circadian rhythms and circadian clock functions, and these are also observed in cultured cell lines. Every cell contains a CLOCK: BMAL1 loop for the generation of circadian rhythms. In this review, we focused on cell autonomous circadian rhythms in immune cells, the inflammatory diseases caused by disruption of circadian rhythms in hormones, and the role of clock genes in inflammatory diseases.

Daily rhythms in endocrine factors of the somatotropic axis and their receptors in gilthead sea bream (Sparus aurata) larvae

Living organisms have adapted to environmental oscillations in light and temperature through evolving biological clocks. Biological rhythms are pervasive at all levels of the endocrine system, including the somatotropic (growth) axis. The objective of the present research was to study the existence of daily rhythms on the somatotropic axis of a marine teleost species, specifically, the gilthead sea bream (Sparus aurata). Larvae of S. aurata at 30 dph (days post hatching), kept under a 9 L:15D (light-dark) photoperiod, were collected every 3 h throughout a 36 h cycle. The expression of the following somatotropic axis genes was analyzed by quantitative PCR: pituitary adenylate cyclase-activating polypeptide 1 (adcyap1), prepro-somatostatin-1 (pss1), growth hormone (gh), growth hormone receptor types 1 and 2 (ghr1 and ghr2, respectively), insulin-like growth factor 1 (igf1) and igf1 receptor a (igf1ra). All genes displayed significant differences among time points and, with the exception of adcyap1, all showed statistically significant daily rhythms. The acrophases of gh, ghr1, ghr2, igf1 and igf1ra were located around the end of the dark phase, between ZT19:44 and ZT0:48 h, whereas the highest expression levels of adcyap1 occurred at ZT18 h. On the other hand, the acrophase of pss1, an inhibitor of Gh secretion, was located at ZT10:16 h, hence it was shifted by several hours with respect to the other genes. The present results provide the first thorough description of somatotropic axis rhythms in gilthead sea bream. Such knowledge provides insights into the role of rhythmic regulation of the Gh/Igf1 axis system in larval growth and metabolism, and it can also improve the implementation of more species-specific feeding regimes.

Control-Oriented Model With Intra-Patient Variations for an Artificial Pancreas

In this work, a low-order model designed for glucose regulation in Type 1 Diabetes Mellitus (T1DM) is obtained from the UVA/Padova metabolic simulator. It captures not only the nonlinear behavior of the glucose-insulin system, but also intra-patient variations related to daily insulin sensitivity ( S_I) changes. To overcome the large inter-subject variability, the model can also be personalized based on a priori patient information. The structure is amenable for linear parameter varying (LPV) controller design, and represents the dynamics from the subcutaneous insulin input to the subcutaneous glucose output. The efficacy of this model is evaluated in comparison with a previous control-oriented model which in turn is an improvement of previous models. Both models are compared in terms of their open- and closed-loop differences with respect to the UVA/Padova model. The proposed model outperforms previous T1DM control-oriented models, which could potentially lead to more robust and reliable controllers for glycemia regulation.

Diel variation in cortisol, glucose, lactic acid and antioxidant system of black sea bass Centropristis striata under natural photoperiod

Diel rhythm in activity of antioxidant enzymes, as well as contents of glutathione and lipid peroxides, has been intensively investigated in Mammalia and Aves, however, the relevant studies about fish are few. In the present study, we examined variation in contents of cortisol, glucose and lactic acid in plasma of black sea bass Centropristis striata under natural photoperiod during a 24-h period. In addition, variation in activity of antioxidant enzymes, such as superoxide dismutase (SOD), glutathione peroxidase (GSH-PX), catalase (CAT) and glutathione reductase (GR) as well as contents of total glutathione (T-GSH), reduced glutathione (GSH), oxidized glutathione (GSSG) and malondialdehyde (MDA) in liver and plasma of the fish were also determined. The plasma and liver samples were collected from the test fish at 3 h intervals during a 24-h cycle, with the first sampling time set at 03:00 h. No significant differences were found in glucose content and activities of GSH-PX and GR in plasma, as well as activities of SOD and GR in liver among different sampling times. In contrast, apparent variation was observed in contents of cortisol, lactic acid and MDA in plasma, activities of SOD and CAT in plasma, contents of MDA, T-GSH, GSH and GSSG in liver and activities of GSH-PX and CAT in liver between different sampling times. Moreover, contents of cortisol and MDA in plasma, SOD activity in plasma, and contents of MDA, GSH and GSSG in liver exhibited circadian rhythm, and their acrophases occurred at 06:08 h, 18:38 h, 15:09 h, 09:57 h, 23:36 h and 07:30 h, respectively. The present study indicates that some physiological parameters relating to stress response, such as cortisol and MDA contents in plasma, MDA, GSH and GSSG contents in liver and SOD activity in plasma changed at different time throughout a day in black sea bass. Therefore, caution should be taken when evaluating stress response in fish with these physiological parameters measured at different times.

The Behavioral Biology of Teams: Multidisciplinary Contributions to Social Dynamics in Isolated, Confined, and Extreme Environments

Teams in isolated, confined, and extreme (ICE) environments face many risks to behavioral health, social dynamics, and team performance. Complex long-duration ICE operational settings such as spaceflight and military deployments are largely closed systems with tightly coupled components, often operating as autonomous microsocieties within isolated ecosystems. As such, all components of the system are presumed to interact and can positively or negatively influence team dynamics through direct or indirect pathways. However, modern team science frameworks rarely consider inputs to the team system from outside the social and behavioral sciences and rarely incorporate biological factors despite the brain and associated neurobiological systems as the nexus of input from the environment and necessary substrate for emergent team dynamics and performance. Here, we provide a high-level overview of several key neurobiological systems relevant to social dynamics. We then describe several key components of ICE systems that can interact with and on neurobiological systems as individual-level inputs influencing social dynamics over the team life cycle-specifically food and nutrition, exercise and physical activity, sleep/wake/work rhythms, and habitat design and layout. Finally, we identify opportunities and strategic considerations for multidisciplinary research and development. Our overarching goal is to encourage multidisciplinary expansion of team science through (1) prospective horizontal integration of variables outside the current bounds of team science as significant inputs to closed ICE team systems and (2) bidirectional vertical integration of biology as the necessary inputs and mediators of individual and team behavioral health and performance. Prospective efforts to account for the behavioral biology of teams in ICE settings through an integrated organizational neuroscience approach will enable the field of team science to better understand and support teams who work, live, serve, and explore in extreme environments.

Chronopharmacology of glucocorticoids

Glucocorticoids influence a wide array of metabolic, anti-inflammatory, immunosuppressive, and cognitive signaling processes, playing an important role in homeostasis and preservation of normal organ function. Synthesis is regulated by the hypothalamic-pituitary-adrenal (HPA) axis of which cortisol is the primary glucocorticoid in humans. Synthetic glucocorticoids are important pharmacological agents that augment the anti-inflammatory and immunosuppressive properties of endogenous cortisol and are widely used for the treatment of asthma, Crohn's disease, and rheumatoid arthritis, amongst other chronic conditions. The homeostatic activity of cortisol is disrupted by the administration of synthetic glucocorticoids and so there is interest in developing treatment options that minimize HPA axis disturbance while maintaining the pharmacological effects. Studies suggest that optimizing drug administration time can achieve this goal. The present review provides an overview of endogenous glucocorticoid activity and recent advances in treatment options that have further improved patient safety and efficacy with an emphasis on chronopharmacology.

Immunoregulatory role of melatonin in cancer

Melatonin is a ubiquitous indole amine that plays a fundamental role in the regulation of the biological rhythm. Disrupted circadian rhythm alters the expression of clock genes and deregulates oncogenes, which finally promote tumor development and progression. An evidence supporting this notion is the higher risk of developing malignancies among night shift workers. Circadian secretion of the pineal hormone also synchronizes the immune system via a reciprocal association that exists between the immune system and melatonin. Immune cells are capable of melatonin biosynthesis in addition to the expression of its receptors. Melatonin induces big changes in different immune cell proportions, enhances their viability and improves immune cell metabolism in the tumor microenvironment. These effects might be directly mediated by melatonin receptors or indirectly through alterations in hormonal and cytokine release. Moreover, melatonin induces apoptosis in tumor cells via the intrinsic and extrinsic pathways of apoptosis, while it protectsthe immune cells. In general, melatonin has a profound impact on immune cell trafficking, cytokine production and apoptosis induction in malignant cells. On such a basis, using melatonin and resynchronization of sleep cycle may have potential implications in immune function enhancement against malignancies, which will be the focus of the present paper.

Seasonal differences in rhythmicity of salivary cortisol in healthy adults

The existence of seasonal changes in secretion of stress hormones and inflammatory mediators by humans is not certain. Here, we aimed to determine whether concentrations of cortisol and IL-6 displayed seasonal rhythmicity. The study was performed in Poznań, Poland (52°N, 16°E) in 7 healthy female volunteers (age 22.6 ± 0.8 yr). Samples of whole mixed unstimulated saliva were collected in winter (February) and summer (June) at 2-h intervals over a 24-h period and analyzed for cortisol and IL-6 by immunoassays. During each season, the subjects answered questionnaires related to their sleeping habits, food intake, physical activity, and perceived seasonality. It turned out that salivary concentrations of cortisol followed a daily rhythm both in winter and summer, as determined by a cosine analysis. However, compared with the winter season, a midline-estimating statistic of rhythm in the summer was significantly higher. Moreover, the rhythm acrophase occurred ~4 h later in the summer than in the winter, whereas the amplitudes did not differ. These fluctuations did not correspond to sleeping habits, food and fluid intake, physical exercise, and the self-assessed chronotype. However, the individuals with higher scores on the seasonal affective disorder scale showed a tendency toward lower relative cortisol amplitude in the summer. In contrast to cortisol, salivary IL-6 concentration did not display daily rhythmicity, and its concentrations did not differ significantly between the seasons. In conclusion, in the summer, cortisol level in saliva is elevated, and its circadian pattern of secretion is shifted. The causes for these alterations do not seem to be related to lifestyle and thus remain to be established.

Emergency management of adrenal insufficiency in children: advocating for treatment options in outpatient and field settings

Adrenal insufficiency (AI) remains a significant cause of morbidity and mortality in children with 1 in 200 episodes of adrenal crisis resulting in death. The goal of this working group of the Pediatric Endocrine Society Drug and Therapeutics Committee was to raise awareness on the importance of early recognition of AI, to advocate for the availability of hydrocortisone sodium succinate (HSS) on emergency medical service (EMS) ambulances or allow EMS personnel to administer patient's HSS home supply to avoid delay in administration of life-saving stress dosing, and to provide guidance on the emergency management of children in adrenal crisis. Currently, hydrocortisone, or an equivalent synthetic glucocorticoid, is not available on most ambulances for emergency stress dose administration by EMS personnel to a child in adrenal crisis. At the same time, many States have regulations preventing the use of patient's home HSS supply to be used to treat acute adrenal crisis. In children with known AI, parents and care providers must be made familiar with the administration of maintenance and stress dose glucocorticoid therapy to prevent adrenal crises. Patients with known AI and their families should be provided an Adrenal Insufficiency Action Plan, including stress hydrocortisone dose (both oral and intramuscular/intravenous) to be provided immediately to EMS providers and triage personnel in urgent care and emergency departments. Advocacy efforts to increase the availability of stress dose HSS during EMS transport care and add HSS to weight-based dosing tapes are highly encouraged.

Dietary Intake of Energy and Nutrients from Breakfast and Risk of Stroke in The Japanese Population: The Circulatory Risk in Communities Study (CIRCS)

Aims: The frequency of breakfast intake has been reported to be inversely associated with the risk of cardiovascular events; however, it is uncertain what the impact of the energy and nutrient intakes from breakfast are. We assessed the association between these intakes from breakfast and the risk of stroke prospectively.

Methods: In a baseline survey of four Japanese communities between 1981 and 1990, we enrolled 3 248 residents (1 662 men and 1 586 women) aged 40–59 years who were free from stroke and heart disease and who responded to the 24-hour dietary recall survey. We assessed the dietary intake at breakfast, lunch, dinner, and other times separately.

Results: During the median 25-year follow-up, 230 individuals (147 men and 83 women) developed stroke. After adjustment for age, community, other dietary intakes, and lifestyle and physiological factors, the multivariable-adjusted hazard ratios (95% confidence intervals) of intracerebral hemorrhage for the highest versus lowest quartiles of energy intake from breakfast were 0.38 (0.15–0.99) in men and 1.36 (0.36–5.10) in women. For the major nutrients, a higher saturated or monounsaturated fat intake at breakfast was associated with a reduced risk of intracerebral hemorrhage in men, and remained statistically significant after further adjustment for intake of other major nutrients from breakfast.

Conclusions: A higher intake of energy from breakfast, primarily saturated or monounsaturated fat, was associated with a reduced risk of intracerebral hemorrhage in Japanese men.

The associations of daylight and melatonin receptor 1B gene rs10830963 variant with glycemic traits: the prospective PPP-Botnia study

BACKGROUND

Seasonal variation in glucose metabolism might be driven by changes in daylight. Melatonin entrains circadian regulation and is directly associated with daylight. The relationship between melatonin receptor 1B gene variants with glycemic traits and type 2 diabetes is well established. We studied if daylight length was associated with glycemic traits and if it modified the relationship between melatonin receptor 1B gene rs10830963 variant and glycemic traits.

MATERIALS

A population-based sample of 3422 18-78-year-old individuals without diabetes underwent an oral glucose tolerance test twice, an average 6.8 years (SD = 0.9) apart and were genotyped for rs10830963. Daylight data was obtained from the Finnish Meteorological Institute.

RESULTS

Cross-sectionally, more daylight was associated with lower fasting glucose, but worse insulin sensitivity and secretion at follow-up. Longitudinally, individuals studied on lighter days at follow-up than at baseline showed higher glucose values during the oral glucose tolerance test and lower Corrected Insulin Response at follow-up. GG genotype carriers in the rs10830963 became more insulin resistant during follow-up if daylight length was shorter at follow-up than at baseline.

CONCLUSIONS

Our study shows that individual glycemic profiles may vary according to daylight, MTNR1B genotype and their interaction. Future studies may consider taking daylight length into account. Key messages In Western Finland, the amount daylight follows an extensive annual variation ranging from 4 h 44 min to 20 h 17 min, making it ideal to study the associations between daylight and glycemic traits. Moreover, this allows researchers to explore if the relationship between the melatonin receptor 1B gene rs10830963 variant and glycemic traits is modified by the amount of daylight both cross-sectionally and longitudinally. This study shows that individuals, who participated in the study on lighter days at the follow-up than at the baseline, displayed to a greater extent worse glycemic profiles across the follow-up. Novel findings from the current study show that in the longitudinal analyses, each addition of the minor G allele of the melatonin receptor 1B gene rs10830963 was associated with worsening of fasting glucose values and insulin secretion across the 6.8-year follow-up. Importantly, this study shows that in those with the rs10830963 GG genotype, insulin sensitivity deteriorated the most significantly across the 6.8-year follow-up if the daylight length on the oral glucose tolerance testing date at the follow-up was shorter than at the baseline. Taken together, the current findings suggest that the amount of daylight may affect glycemic traits, especially fasting glucose and insulin secretion even though the effect size is small. The association can very according to the rs10830963 risk variant. Further research is needed to elucidate the mechanisms behind these associations.

A new melatonin oral delivery platform based on orodispersible films containing solid lipid microparticles

An innovative delivery system for melatonin, based on the incorporation of solid lipid microparticles in orodispersible films (ODFs) made of maltodextrin, was designed and developed. Lipid microparticles at two different melatonin concentrations (10 and 20% w/w) were produced by the spray congealing technology using two different lipid carrier (tristearin and hydrogenated castor oil) and characterized in terms of size, solid state, drug loading and drug release pattern. Tristearin microparticles were discarded due to a polymorphic modification of the carrier. The incorporation of hydrogenated castor oil microparticles in ODFs by using the casting method did not alter significantly the shape and dimension of the microparticles and the mechanical properties (elasticity and strength) of the films, which remained acceptable for manufacturing and handling. The in vitro release studies performed in saliva, gastric and intestinal simulated media on ODFs containing melatonin loaded in hydrogenated castor oil microparticles revealed the possibility to combine with an immediate release of the drug and a sustained release over at least 5 h period. In conclusion, the proposed drug delivery system maintains the advantages of ODFs, i.e. the suitability to be swallowed without water, and permits the tuning of drug release according to the clinical needs by modulating the ratio of free and microencapsulated drug in the ODF.

Relation of Different Components of Climate with Human Pituitary-Thyroid Axis and FT3/FT4 Ratio: A Study on Euthyroid and SCH Subjects in Two Different Seasons

BACKGROUND

Various changes in thyroid hormones (TH) and thyroid-stimulating hormone (TSH) level were observed in different seasons among euthyroid and hypothyroid subjects living in areas with an extreme temperature difference between summer and winter.

OBJECTIVES

This study aims at finding the effect of temperate climate on the seasonal variations of TSH and TH in euthyroid and subclinical hypothyroidism (SCH) subjects and at evaluating if the test season has an effect on the number of subjects diagnosed as SCH. It basically focuses on the relation of different components of climate with TH and TSH.

METHOD

In a prospective study on 152 healthy (euthyroid) volunteers and 25 SCH subjects, the serum hormone levels (TSH, FT4, and FT3) were measured in both the summer and winter seasons and correlated with all the climate components using Pearson's correlation coefficient. The effect of duration of outdoor exposure on hormone levels was compared using a paired sample t-test (P < 0.05).

RESULTS

Small but statistically significant increased FT3 level and decreased FT4 level were observed during the winter season in euthyroid and SCH subjects, respectively. There was a significant negative correlation between FT3 and FT3/FT4 ratio with temperature and sunshine duration and a positive correlation with humidity and atmospheric pressure. A positive correlation was found between FT4 and sunshine duration.

CONCLUSION

The climate components contributed to the slight variance in hormone levels in different seasons, and the effect was mostly on peripheral conversion of FT4 to FT3 rather than the pituitary-thyroid axis leading to slightly higher FT3 in winter. Seasonal variation does not affect the diagnosis of SCH cases.

Role of the Circadian Clock in the Metabolic Syndrome and Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) is the most common chronic liver disease in industrialized nations and is strongly associated with the metabolic syndrome. The prevalence of NAFLD continues to rise along with the epidemic of the metabolic syndrome. Metabolic homeostasis is linked to the circadian clock (rhythm), with multiple signaling pathways in organs regulated by circadian clock genes, and recent studies of circadian clock gene functions suggest that disruption of the circadian rhythm is associated with significant morbidity and mortality, including the metabolic syndrome. In the industrialized world, various human behaviors and activities such as work and eating patterns, jet lag, and sleep deprivation interfere with the circadian rhythm, leading to perturbations in metabolism and development of the metabolic syndrome. In this review, we discuss how disruption of the circadian rhythm is associated with various metabolic conditions that comprise the metabolic syndrome and NAFLD.

Melatonin as a Hormone: New Physiological and Clinical Insights

Melatonin is a ubiquitous molecule present in almost every live being from bacteria to humans. In vertebrates, besides being produced in peripheral tissues and acting as an autocrine and paracrine signal, melatonin is centrally synthetized by a neuroendocrine organ, the pineal gland. Independently of the considered species, pineal hormone melatonin is always produced during the night and its production and secretory episode duration are directly dependent on the length of the night. As its production is tightly linked to the light/dark cycle, melatonin main hormonal systemic integrative action is to coordinate behavioral and physiological adaptations to the environmental geophysical day and season. The circadian signal is dependent on its daily production regularity, on the contrast between day and night concentrations, and on specially developed ways of action. During its daily secretory episode, melatonin coordinates the night adaptive physiology through immediate effects and primes the day adaptive responses through prospective effects that will only appear at daytime, when melatonin is absent. Similarly, the annual history of the daily melatonin secretory episode duration primes the central nervous/endocrine system to the seasons to come. Remarkably, maternal melatonin programs the fetuses' behavior and physiology to cope with the environmental light/dark cycle and season after birth. These unique ways of action turn melatonin into a biological time-domain-acting molecule. The present review focuses on the above considerations, proposes a putative classification of clinical melatonin dysfunctions, and discusses general guidelines to the therapeutic use of melatonin.

Intake of an Obesogenic Cafeteria Diet Affects Body Weight, Feeding Behavior, and Glucose and Lipid Metabolism in a Photoperiod-Dependent Manner in F344 Rats

We previously demonstrated that chronic exposure to different photoperiods induced marked variations in several glucose and lipid metabolism-related parameters in normoweight Fischer 344 (F344) rats. Here, we examined the effects of the combination of an obesogenic cafeteria diet (CAF) and the chronic exposure to three different day lengths (L12, 12 h light/day; L18, 18 h light/day; and L6, 6 h light/day) in this rat strain. Although no changes were observed during the first 4 weeks of adaptation to the different photoperiods in which animals were fed a standard diet, the addition of the CAF for the subsequent 7 weeks triggered profound physiologic and metabolic alterations in a photoperiod-dependent manner. Compared with L12 rats, both L6 and L18 animals displayed lower body weight gain and cumulative food intake in addition to decreased energy expenditure and locomotor activity. These changes were accompanied by differences in food preferences and by a sharp upregulation of the orexigenic genes Npy and Ghsr in the hypothalamus, which could be understood as a homeostatic mechanism for increasing food consumption to restore body weight control. L18 rats also exhibited higher glycemia than the L6 group, which could be partly attributed to the decreased pAkt2 levels in the soleus muscle and the downregulation of Irs1 mRNA levels in the gastrocnemius muscle. Furthermore, L6 animals displayed lower whole-body lipid utilization than the L18 group, which could be related to the lower lipid intake and to the decreased mRNA levels of the fatty acid transporter gene Fatp1 observed in the soleus muscle. The profound differences observed between L6 and L18 rats could be related with hepatic and muscular changes in the expression of circadian rhythm-related genes Cry1, Bmal1, Per2, and Nr1d1. Although further research is needed to elucidate the pathophysiologic relevance of these findings, our study could contribute to emphasize the impact of the consumption of highly palatable and energy dense foods regularly consumed by humans on the physiological and metabolic adaptations that occur in response to seasonal variations of day length, especially in diseases associated with changes in food intake and preference such as obesity and seasonal affective disorder.

Where in the world? Latitude, longitude and season contribute to the complex co-ordinates determining cortisol levels

OBJECTIVE

Cortisol is a critical stress hormone with circadian rhythms synchronized by light. There are seasonal differences in expression of pro-inflammatory genes and in some diseases moderated by glucocorticoids. As light changes with season and with latitude and longitude, we assessed changes in population cortisol associated with these parameters.

DESIGN

Retrospective data audit.

PATIENTS

Populations across 4 states of Australia over 3 years.

MEASUREMENTS

Serum cortisol levels, age, gender, time of collection, sunrise time, season and location were determined.

RESULTS

In 4 geographically separate populations (n = 84 937), sunrise time and time of sample collection were the most important factors influencing median cortisol. Over 2 hours in the morning cortisol could decrease by up to 76 nmol/L, and for each hour that sunrise time advanced there was up to 6.9% increase in cortisol. A cyclic seasonal pattern of cortisol was confirmed each year in all populations with autumn/winter cortisol highest compared to spring/summer with differences of up to 44 nmol/L. There was less change in cortisol in latitudes closer to the equator but cortisol progressively increased from 25 to 30°S of the equator. In more southerly latitudes, seasonal cortisol variation also increased, and over the entire latitude range, there was up to 50 nmol/L change in cortisol. Longitude variation within a time zone had a minimal effect on median cortisol.

CONCLUSIONS

Location, time of year and time of day are important influences on population cortisol levels. Elevated autumn/winter morning cortisol levels are likely due to sampling closer to the circadian peak due to later sunrise time. Understanding how the environment can influence cortisol levels may further our knowledge of physiology and disease.

Chronic treatment with dexamethasone alters clock gene expression and melatonin synthesis in rat pineal gland at night

BACKGROUND

Melatonin is a neuroendocrine hormone that regulates many functions involving energy metabolism and behavior in mammals throughout the light/dark cycle. It is considered an output signal of the central circadian clock, located in the suprachiasmatic nucleus of the hypothalamus. Melatonin synthesis can be influenced by other hormones, such as insulin and glucocorticoids in pathological conditions or during stress. Furthermore, glucocorticoids appear to modulate circadian clock genes in peripheral tissues and are associated with the onset of metabolic diseases. In the pineal gland, the modulation of melatonin synthesis by clock genes has already been demonstrated. However, few studies have shown the effects of glucocorticoids on clock genes expression in the pineal gland.

RESULTS

We verified that rats treated with dexamethasone (2 mg/kg body weight, intraperitoneal) for 10 consecutive days, showed hyperglycemia and pronounced hyperinsulinemia during the dark phase. Insulin sensitivity, glucose tolerance, melatonin synthesis, and enzymatic activity of arylalkylamine N-acetyltransferase, the key enzyme of melatonin synthesis, were reduced. Furthermore, we observed an increase in the expression of Bmal1, Per1, Per2, Cry1, and Cry2 in pineal glands of rats treated with dexamethasone.

CONCLUSION

These results show that chronic treatment with dexamethasone can modulate both melatonin synthesis and circadian clock expression during the dark phase.

Drug delivery systems for programmed and on-demand release

With the advancement in medical science and understanding the importance of biodistribution and pharmacokinetics of therapeutic agents, modern drug delivery research strives to utilize novel materials and fabrication technologies for the preparation of robust drug delivery systems to combat acute and chronic diseases. Compared to traditional drug carriers, which could only control the release of the agents in a monotonic manner, the new drug carriers are able to provide a precise control over the release time and the quantity of drug introduced into the patient's body. To achieve this goal, scientists have introduced "programmed" and "on-demand" approaches. The former provides delivery systems with a sophisticated architecture to precisely tune the release rate for a definite time period, while the latter includes systems directly controlled by an operator/practitioner, perhaps with a remote device triggering/affecting the implanted or injected drug carrier. Ideally, such devices can determine flexible release pattern and intensify the efficacy of a therapy via controlling time, duration, dosage, and location of drug release in a predictable, repeatable, and reliable manner. This review sheds light on the past and current techniques available for fabricating and remotely controlling drug delivery systems and addresses the application of new technologies (e.g. 3D printing) in this field.

Biological variables influencing the estimation of reference limits

Reference limits (RLs) are required to evaluate laboratory results for medical decisions. The establishment of RL depends on the pre-analytical and the analytical conditions. Furthermore, biological characteristics of the sub-population chosen to provide the reference samples may influence the RL. The most important biological preconditions are gender, age, chronobiological influences, posture, regional and ethnic effects. The influence of these components varies and is often neglected. Therefore, a list of biological variables is collected from the literature and their influence on the estimation of RL is discussed. Biological preconditions must be specified if RL are reported as well for directly as for indirectly estimated RL. The influence of biological variables is especially important if RL established by direct methods are compared with those derived from indirect techniques. Even if these factors are not incorporated into the estimation of RL, their understanding can assist the interpretation of laboratory results of an individual.

The Exposure to Different Photoperiods Strongly Modulates the Glucose and Lipid Metabolisms of Normoweight Fischer 344 Rats

Seasonal variations in day length trigger clear changes in the behavior, growth, food intake, and reproductive status of photoperiod-sensitive animals, such as Fischer 344 rats. However, there is little information about the effects of seasonal fluctuations in day length on glucose and lipid metabolisms and their underlying mechanisms in this model. To gain knowledge on these issues, three groups of male Fischer 344 rats were fed with a standard diet and exposed to different photoperiods for 14 weeks: normal photoperiod (L12, 12 h light/day), long photoperiod (L18, 18 h light/day), and short photoperiod (L6, 6 h light/day). A multivariate analysis carried out with 239 biometric, serum, hepatic and skeletal muscle parameters revealed a clear separation among the three groups. Compared with L12 rats, L6 animals displayed a marked alteration of glucose homeostasis and fatty acid uptake and oxidation, which were evidenced by the following observations: (1) increased circulating levels of glucose and non-esterified fatty acids; (2) a sharp down-regulation of the phosphorylated Akt2 levels, a downstream post-receptor target of insulin, in both the soleus and gastrocnemius muscles; (3) decreased expression in the soleus muscle of the glucose metabolism-related microRNA-194 and lower mRNA levels of the genes involved in glucose metabolism (Irs1, soleus, and Glut2, liver), β-oxidation (Had and Cpt1β, soleus) and fatty acid transport (Cd36, soleus, and liver). L18 animals also displayed higher blood glucose levels than L12 rats and profound changes in other glucose and lipid metabolism-related parameters in the blood, liver, and skeletal muscles. However, the mechanisms that account for the observed effects were less evident than those reported in L6 animals. In conclusion, exposure to different photoperiods strongly modulated glucose and lipid metabolisms in normoweight rats. These findings emphasize the relevance of circannual rhythms in metabolic homeostasis regulation and suggest that Fischer 344 rats are a promising animal model with which to study glucose- and lipid-related pathologies that are influenced by seasonal variations, such as obesity, cardiovascular disease and seasonal affective disorder.

Preparation, Characterization and In Vitro / In Vivo Evaluation of Oral Time-Controlled Release Etodolac Pellets

The objective of this study was to prepare time-controlled release etodolac pellets to facilitate drug administration according to the body's biological rhythm, optimize the drug's desired effects, and minimize adverse effects. The preparation consisted of three laminal layers from center to outside: the core, the swelling layer, and the insoluble polymer membrane. Factors influenced the core and the coating films were investigated in this study. The core pellets formulated with etodolac, lactose, and sodium carboxymethyl starch (CMS-Na) were prepared by extrusion-spheronization and then coated by a fluidized bed coater. Croscarmellose sodium (CC-Na) was selected as the swelling agent, and ethyl cellulose (EC) as the controlled release layer. The prepared pellets were characterized by scanning electron microscopy and evaluated by a dissolution test and a pharmacokinetic study. Compared with commercial available capsules, pharmacokinetics studies in beagle dogs indicated that the prepared pellets release the drug within a short period of time, immediately after a predetermined lag time. A good correlation between in vitro dissolution and in vivo absorption of the pellets was exhibited in the analysis.