Effects of circadian disruption on physiology and pathology: from bench to clinic (and back)

Nested within the hypothalamus, the suprachiasmatic nuclei (SCN) represent a central biological clock that regulates daily and circadian (i.e., close to 24 h) rhythms in mammals. Besides the SCN, a number of peripheral oscillators throughout the body control local rhythms and are usually kept in pace by the central clock. In order to represent an adaptive value, circadian rhythms must be entrained by environmental signals or zeitgebers, the main one being the daily light?dark (LD) cycle. The SCN adopt a stable phase relationship with the LD cycle that, when challenged, results in abrupt or chronic changes in overt rhythms and, in turn, in physiological, behavioral, and metabolic variables. Changes in entrainment, both acute and chronic, may have severe consequences in human performance and pathological outcome. Indeed, animal models of desynchronization have become a useful tool to understand such changes and to evaluate potential treatments in human subjects. Here we review a number of alterations in circadian entrainment, including jet lag, social jet lag (i.e., desynchronization between body rhythms and normal time schedules), shift work, and exposure to nocturnal light, both in human subjects and in laboratory animals. Finally, we focus on the health consequences related to circadian/entrainment disorders and propose a number of approaches for the management of circadian desynchronization.Fil: Chiesa, Juan José. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Duhart, José Manuel. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Casiraghi, Leandro Pablo. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Paladino, Natalia. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Bussi, Ivana Leda. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Golombek, Diego Andrés. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Screen use, blue light and sleep

Veel Nederlanders gebruiken lichtgevende schermen in de avond: het gebruik is het hoogst onder adolescenten (13-18 jaar) en volwassenen. Vaak neemt het gebruik in de avond ook aanzienlijke tijd in beslag (meer dan twee uur). Dit onderzoek bevestigt eerdere bevindingen dat frequent of langdurig schermgebruik in de avond samenhangt met verstoorde slaap. Bewustwording van het gebruik is dan ook belangrijk, voornamelijk wanneer een computer, smartphone of tablet in het uur voor het slapen gaan wordt gebruikt. Dit blijkt uit onderzoek van het RIVM, in samenwerking met het Amsterdam Medisch Centrum, het Nederlands Herseninstituut en Lifelines. Hierin is voor het eerst in Nederland het schermgebruik van kinderen en adolescenten (8-18 jaar) in de avond uitgebreid in kaart gebracht in samenhang met slaap. Het blijkt dat de groep die dagelijks of langdurig gebruikmaakt van een of meerdere schermen (computer, smartphone en/of tablet) tot 40 minuten korter slaapt dan de groep die dit niet, of korter, doet. De kortere slaapduur komt voornamelijk doordat deze kinderen en adolescenten later gaan slapen. Van de kinderen (8-13 jaar) gebruikt 22% dagelijks een scherm in de avond. Onder adolescenten (13-18 jaar) is dit 83%. Adolescenten die dagelijks een scherm gebruiken in het uur voor het slapen, hebben meer slaapklachten, zoals later in slaap vallen, korter slapen en 's nachts wakker worden. Ook vermelden zij meer symptomen van slaaptekort overdag, zoals moeite om wakker te blijven. Deze klachten verminderden bij adolescenten die als experiment een week lang geen scherm gebruikten of tijdens het schermgebruik een oranje bril droegen die het blauwe licht blokkeert. In de afgelopen jaren zijn steeds meer lichtgevende schermen ontwikkeld: niet alleen tv's maar ook computers, laptops, tablets en smartphones. De recent ontwikkelde schermen zenden meer blauw licht uit dan de traditionele bronnen, omdat zij gebruikmaken van led-technologie. Bekend is dat blauw licht invloed heeft op onze biologische klok, en daarmee de slaap kan verstoren. Door een structureel slaaptekort kunnen mensen zich slechter concentreren en minder goed presteren. Ook kunnen gezondheidsproblemen ontstaan. Vervolgonderzoek is nodig om te bepalen of beschikbare (ingebouwde) blauwlichtfilters op apparaten de effecten op slaap kunnen verminderen.Use of light-emitting screens during the evening is very common among Dutch adults (=18 years), adolescents (13-18 years) and children (8-13 years). This use frequently occurs during a long period of time during the evening (over 2 hours), in particular by adolescents. The current study further shows, in line with previous research, that frequent or long term use of light-emitting screens during the evening is associated with disturbed sleep. More awareness is needed, in particular regarding use of computers, smartphones and/or tablet from one hour until going to sleep. This is evident from research conducted by RIVM in collaboration with Amsterdam Medical Centre, Netherlands Institute for Neuroscience, and Lifelines. In this study, use of light-emitting screens among Dutch children and adolescents was elaborately investigated. Results show that children and adolescents who daily or on average for more than 2 hours per evening use an light-emitting screen (computer, smartphone, and/or tablet) sleep up to 40 minutes shorter compared to children who do not daily use an screen or for a shorter duration. Among children 22% uses a screen daily, whereas this is 83% among adolescents. Adolescents who use an light-emitting screen daily in the hour before going to sleep, have more sleep complaints such as: a longer latency to fall asleep, shorter sleep duration and more frequent waking up during the night. They also have more symptoms of sleep deprivation during the day, such as having trouble staying awake. These complaints were reduced among adolescents who, during an experimental study, were not using screens for one week during the evening, or where using orange tinted glasses that block blue light. The past years several light-emitting screens have been developed: in addition to the television that has been around several decades, we now have computers, laptops, tablets and smartphones. In particular, the recent developed screens that use light-emitting diodes (leds) as a light source emit more blue light compared to more traditional light sources. It is known that blue light during the evening influences our biological clock and can disturb sleep. A chronic sleep disturbance can cause concentration problems, reduced performance at school or work and can cause health problems. An important topic for further research is to investigate if the available blue light filters on devices can reduce the observed effects on sleep.NVW

Circadian clocks and insulin resistance

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