A novel model of the hypothalamic-pituitary-adrenal axis is presented. The axis is an endocrine system responsible for coping with stress and it is likely to be involved in depression. The dynamics of the system is studied and existence, uniqueness and positivity of the solution and the existence of an attracting trapping region are proved. The model is calibrated and compared to data for healthy and depressed subjects. A sensitivity analysis resulting in a set of identifiable physiological parameters is provided. A subset is selected for parameter estimation and a reduced version of the model is stated and an approximated version is discussed. The model is physiologically based, thus parameters are representative for gland functions or elimination processes. Hence the model may be used for pointing out pathologies by parameter estimation and hypothesis testing whereby it may be used as an objective and refined method for diagnosing depression and suggesting individual treatment protocols. Finally, the method may inspire pharmaceutical companies to develop target specific psychopharmaca for more effective and individual treatment.
Integrated Inflammatory Stress (ITIS) ModelBangsgaard, Elisabeth O.; Hjorth, Poul G.; Olufsen, Mette S.; Mehlsen, Jesper; Ottesen, Johnny T.
Published in: Bulletin of Mathematical BiologyLink to article, DOI: 10.1007/s11538-017-0293-2
Publication date: 2017
Document VersionPublisher's PDF, also known as Version of record Abstract During the last decade, there has been an increasing interest in the coupling between the acute inflammatory response and the Hypothalamic-Pituitary-Adrenal (HPA) axis. The inflammatory response is activated acutely by pathogen-or damagerelated molecular patterns, whereas the HPA axis maintains a long-term level of the stress hormone cortisol which is also anti-inflammatory. A new integrated model of the interaction between these two subsystems of the inflammatory system is proposed and coined the integrated inflammatory stress (ITIS) model. The coupling mechanisms describing the interactions between the subsystems in the ITIS model are formulated based on biological reasoning and its ability to describe clinical data. The ITIS model is calibrated and validated by simulating various scenarios related to endotoxin (LPS) exposure. The model is capable of reproducing human data of tumor necrosis factor alpha, adrenocorticotropic hormone (ACTH) and cortisol and suggests that repeated LPS injections lead to a deficient response. The ITIS model predicts that the most extensive response to an LPS injection in ACTH and cortisol concentrations is observed in the early hours of the day. A constant activation results in elevated levels of the variables in the model while a prolonged change of the oscillations in ACTH and
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.