Bonmati-Carrion, M., Arguelles-Prieto, R., Martinez-Madrid, M., Reiter, R., Hardeland, R., Rol, M., et al. (2014). Protecting the Melatonin Rhythm through Circadian Healthy Light Exposure. IJMS, 15(12), 23448–23500.
Abstract: Currently, in developed countries, nights are excessively illuminated (light at night), whereas daytime is mainly spent indoors, and thus people are exposed to much lower light intensities than under natural conditions. In spite of the positive impact of artificial light, we pay a price for the easy access to light during the night: disorganization of our circadian system or chronodisruption (CD), including perturbations in melatonin rhythm. Epidemiological studies show that CD is associated with an increased incidence of diabetes, obesity, heart disease, cognitive and affective impairment, premature aging and some types of cancer. Knowledge of retinal photoreceptors and the discovery of melanopsin in some ganglion cells demonstrate that light intensity, timing and spectrum must be considered to keep the biological clock properly entrained. Importantly, not all wavelengths of light are equally chronodisrupting. Blue light, which is particularly beneficial during the daytime, seems to be more disruptive at night, and induces the strongest melatonin inhibition. Nocturnal blue light exposure is currently increasing, due to the proliferation of energy-efficient lighting (LEDs) and electronic devices. Thus, the development of lighting systems that preserve the melatonin rhythm could reduce the health risks induced by chronodisruption. This review addresses the state of the art regarding the crosstalk between light and the circadian system.
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Cornean, R. E., Margescu, M., & Simionescu, B. (2015). Disruption of the Cyrcadian System and Obesity. Jurnalul Pediatrului, XVIII(Supplement 3), 38–42.
Abstract: Disruption of the cyrcadian system is a relatively new concept incriminated as being responsible for obesity, cardiovascular involvement, cognitive impairment, premature aging and last but not least, cancer. Because obesity is undoubtedly assimilated today to the medical conditions related to the disruption of the normal chronobiology, this paper presents the pivotal role of chronodisruption in the neuroendocrine control of appetite among these patients.
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Dominoni, D. (2015). The effects of light pollution on biological rhythms of birds: an integrated, mechanistic perspective. J. of Ornith., 156(1), 409–418.
Abstract: Light pollution is considered a threat for biodiversity given the extent to which it can affect a vast number of behavioral and physiological processes in several species. This comes as no surprise as light is a fundamental, environmental cue through which organisms time their daily and seasonal activities, and alterations in the light environment have been found to affect profoundly the synchronization of the circadian clock, the endogenous mechanism that tracks and predicts variation in the external light/dark cycles. In this context, birds have been one of the most studied animal taxa, but our understanding of the effects of light pollution on the biological rhythms of avian species is mostly limited to behavioral responses. In order to understand which proximate mechanisms may be affected by artificial lights, we need an integrated perspective that focuses on light as a physiological signal, and especially on how photic information is perceived, decoded, and transmitted through the whole body. The aim of this review is to summarize the effects of light pollution on physiological and biochemical mechanisms that underlie changes in birds’ behavior, highlighting the current gaps in our knowledge and proposing future research avenues.
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Erren, T. C., Morfeld, P., Foster, R. G., Reiter, R. J., Gross, J. V., & Westermann, I. K. (2016). Sleep and cancer: Synthesis of experimental data and meta-analyses of cancer incidence among some 1 500 000 study individuals in 13 countries. Chronobiol Int, 33(4), 325–350.
Abstract: Sleep and its impact on physiology and pathophysiology are researched at an accelerating pace and from many different angles. Experiments provide evidence for chronobiologically plausible links between chronodisruption and sleep and circadian rhythm disruption (SCRD), on the one hand, and the development of cancer, on the other. Epidemiological evidence from cancer incidence among some 1 500 000 study individuals in 13 countries regarding associations with sleep duration, napping or “poor sleep” is variable and inconclusive. Combined adjusted relative risks (meta-RRs) for female breast cancer, based on heterogeneous data, were 1.01 (95% CI: 0.97-1.06). Meta-RRs for cancers of the colorectum and of the lung in women and men and for prostate cancer were 1.08 (95% CI: 1.03-1.13), 1.11 (95% CI: 1.00-1.22) and 1.05 (95% CI: 0.83-1.33), respectively. The significantly increased meta-RRs for colorectal cancer, based on homogeneous data, warrant targeted study. However, the paramount epidemiological problem inhibiting valid conclusions about the associations between sleep and cancer is the probable misclassification of the exposures to facets of sleep over time. Regarding the inevitable conclusion that more research is needed to answer How are sleep and cancer linked in humans? we offer eight sets of recommendations for future studies which must take note of the complexity of multidirectional relationships.
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Reiter, R. J., Rosales-Corral, S., Coto-Montes, A., Antonio Boga, J., Tan, D. X., Davis, J. M., et al. (2011). The photoperiod, circadian regulation and chronodisruption: the requisite interplay between the suprachiasmatic nuclei and the pineal and gut melatonin. Journal of Physiology and Pharmacology, 62, 269–274.
Abstract: Biological rhythms are essential for optimal health (1, 2). Throughout the course of human evolution, hominids were exposed to regularly alternating periods of light and dark during every 24-hour period. This evolutionary period, which for humans may have lasted for three million or more years, allowed species to take advantage of the light:dark cycle to adjust their physiology and to synchronize it with the prevailing light:dark environment. To take advantage of this information, vertebrates, including hominids, evolved a group of neurons to monitor the photoperiodic environment and to adjust organismal, organ and cellular function accordingly.
This paired group of light-responsive neurons is located in the mediobasal preoptic area at the diencephalic-telencephalic junction just anterior to the hypothalamus. Since these neurons lie immediately above the decussating axons of the optic nerve, i.e., the optic chiasma, they are named the suprachiasmatic nuclei (SCN) (3, 4). The SCN orchestrate all known circadian rhythms in vertebrates and are referred to as the master biological clock or the central rhythm generator.
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