title: The Circadian System: A Regulatory Feedback Network of Periphery and Brain.
abstract: Circadian rhythms are generated by the autonomous circadian clock, the suprachiasmatic nucleus (SCN), and clock genes that are present in all tissues. The SCN times these peripheral clocks, as well as behavioral and physiological processes. Recent studies show that frequent violations of conditions set by our biological clock, such as shift work, jet lag, sleep deprivation, or simply eating at the wrong time of the day, may have deleterious effects on health. This infringement, also known as circadian desynchronization, is associated with chronic diseases like diabetes, hypertension, cancer, and psychiatric disorders. In this review, we will evaluate evidence that these diseases stem from the need of the SCN for peripheral feedback to fine-tune its output and adjust physiological processes to the requirements of the moment. This feedback can vary from neuronal or hormonal signals from the liver to changes in blood pressure. Desynchronization renders the circadian network dysfunctional, resulting in a breakdown of many functions driven by the SCN, disrupting core clock rhythms in the periphery and disorganizing cellular processes that are normally driven by the synchrony between behavior and peripheral signals with neuronal and humoral output of the hypothalamus. Consequently, we propose that the loss of synchrony between the different elements of this circadian network as may occur during shiftwork and jet lag is the reason for the occurrence of health problems.
authors.affiliation: Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Ciudad Universitaria, Mexico; Netherlands Institute for Neuroscience, an Institute of the Royal Netherlands Academy of Arts and Sciences, Amsterdam, The Netherlands;
authors.forename: Frederik N
authors.initials: FN
authors.lastname: Buijs
authors.affiliation: Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Ciudad Universitaria, Mexico;
authors.forename: Luis
authors.initials: L
authors.lastname: León-Mercado
authors.affiliation: Departamento de Anatomía, Facultad de Medicina, Universidad Autónoma de México, Ciudad Universitaria, Mexico.
authors.forename: Mara
authors.initials: M
authors.lastname: Guzmán-Ruiz
authors.affiliation: Departamento de Anatomía, Facultad de Medicina, Universidad Autónoma de México, Ciudad Universitaria, Mexico.
authors.forename: Natali N
authors.initials: NN
authors.lastname: Guerrero-Vargas
authors.affiliation: Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Ciudad Universitaria, Mexico; Department of Psychiatry and Behavioral Neuroscience, Division of Bipolar Disorder Research, University of Cincinnati, Cincinnati, Ohio; and.
authors.forename: Francisco
authors.initials: F
authors.lastname: Romo-Nava
authors.affiliation: Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Ciudad Universitaria, Mexico; ruudbuijs@gmail.com.
authors.forename: Ruud M
authors.initials: RM
authors.lastname: Buijs
mesh_terms: D000818:Animals; D001519:Behavior / Q000502:physiology*; D057906:Circadian Clocks / Q000502:physiology*; D002940:Circadian Rhythm / Q000502:physiology*; D006801:Humans; D007031:Hypothalamus / Q000502:physiology*; D009424:Nervous System Physiological Phenomena; D013493:Suprachiasmatic Nucleus / Q000502:physiology*