title: Time-of-day-dependent adaptation of the HPA axis to predictable social defeat stress.
abstract: In modern societies, the risk of developing a whole array of affective and somatic disorders is associated with the prevalence of frequent psychosocial stress. Therefore, a better understanding of adaptive stress responses and their underlying molecular mechanisms is of high clinical interest. In response to an acute stressor, each organism can either show passive freezing or active fight-or-flight behaviour, with activation of sympathetic nervous system and the hypothalamus-pituitary-adrenal (HPA) axis providing the necessary energy for the latter by releasing catecholamines and glucocorticoids (GC). Recent data suggest that stress responses are also regulated by the endogenous circadian clock. In consequence, the timing of stress may critically affect adaptive responses to and/or pathological effects of repetitive stressor exposure. In this article, we characterize the impact of predictable social defeat stress during daytime versus nighttime on bodyweight development and HPA axis activity in mice. While 19 days of social daytime stress led to a transient reduction in bodyweight without altering HPA axis activity at the predicted time of stressor exposure, more detrimental effects were seen in anticipation of nighttime stress. Repeated nighttime stressor exposure led to alterations in food metabolization and reduced HPA axis activity with lower circulating adrenocorticotropic hormone (ACTH) and GC concentrations at the time of predicted stressor exposure. Our data reveal a circadian gating of stress adaptation to predictable social defeat stress at the level of the HPA axis with impact on metabolic homeostasis underpinning the importance of timing for the body's adaptability to repetitive stress.
authors.affiliation: University of LübeckChronophysiology Group, Medical Department 1, Lübeck, Germany.
authors.forename: C E
authors.initials: CE
authors.lastname: Koch
authors.affiliation: University of WürzburgBiocenter, Theodor-Boveri-Institute, Neurobiology and Genetics, Würzburg, Germany.
authors.forename: M S
authors.initials: MS
authors.lastname: Bartlang
authors.affiliation: University of LübeckChronophysiology Group, Medical Department 1, Lübeck, Germany.
authors.forename: J T
authors.initials: JT
authors.lastname: Kiehn
authors.affiliation: Department of Behavioral and Molecular NeurobiologyUniversity of Regensburg, Regensburg, Germany.
authors.forename: L
authors.initials: L
authors.lastname: Lucke
authors.affiliation: University of LübeckChronophysiology Group, Medical Department 1, Lübeck, Germany.
authors.forename: N
authors.initials: N
authors.lastname: Naujokat
authors.affiliation: University of WürzburgBiocenter, Theodor-Boveri-Institute, Neurobiology and Genetics, Würzburg, Germany.
authors.forename: C
authors.initials: C
authors.lastname: Helfrich-Förster
authors.affiliation: Department of Behavioral and Molecular NeurobiologyUniversity of Regensburg, Regensburg, Germany henrik.oster@uksh.de Stefan.Reber@uniklinikulm.de.
authors.forename: S O
authors.initials: SO
authors.lastname: Reber
authors.affiliation: University of LübeckChronophysiology Group, Medical Department 1, Lübeck, Germany henrik.oster@uksh.de Stefan.Reber@uniklinikulm.de.
authors.forename: H
authors.initials: H
authors.lastname: Oster
mesh_terms: D000222:Adaptation, Physiological; D000324:Adrenocorticotropic Hormone / Q000502:physiology; D000818:Animals; D001127:Arginine Vasopressin / Q000235:genetics / Q000502:physiology; D002940:Circadian Rhythm / Q000502:physiology*; D003346:Corticotropin-Releasing Hormone / Q000235:genetics / Q000502:physiology; D004734:Energy Metabolism; D005938:Glucocorticoids / Q000502:physiology; D006801:Humans; D007030:Hypothalamo-Hypophyseal System / Q000503:physiopathology*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D023421:Models, Animal; D010913:Pituitary-Adrenal System / Q000503:physiopathology*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D013315:Stress, Psychological / Q000503:physiopathology*
chemical_list: D005938:Glucocorticoids; D012333:RNA, Messenger; D001127:Arginine Vasopressin; D000324:Adrenocorticotropic Hormone; D003346:Corticotropin-Releasing Hormone
keywords: HPA axis; circadian gating of stress responses; energy homeostasis; social defeat stress