ABSTRACT:
This a model from the article:
Inclusion of the glucocorticoid receptor in a hypothalamic pituitary adrenal
axis model reveals bistability.
Gupta S, Aslakson E, Gurbaxani BM, Vernon SD. Theor Biol Med Model
2007 Feb 14;4:8 17300722
,
Abstract:
BACKGROUND: The body's primary stress management system is the hypothalamic
pituitary adrenal (HPA) axis. The HPA axis responds to physical and mental
challenge to maintain homeostasis in part by controlling the body's cortisol
level. Dysregulation of the HPA axis is implicated in numerous stress-related
diseases. RESULTS: We developed a structured model of the HPA axis that includes
the glucocorticoid receptor (GR). This model incorporates nonlinear kinetics of
pituitary GR synthesis. The nonlinear effect arises from the fact that GR
homodimerizes after cortisol activation and induces its own synthesis in the
pituitary. This homodimerization makes possible two stable steady states (low
and high) and one unstable state of cortisol production resulting in bistability
of the HPA axis. In this model, low GR concentration represents the normal
steady state, and high GR concentration represents a dysregulated steady state.
A short stress in the normal steady state produces a small perturbation in the
GR concentration that quickly returns to normal levels. Long, repeated stress
produces persistent and high GR concentration that does not return to baseline
forcing the HPA axis to an alternate steady state. One consequence of increased
steady state GR is reduced steady state cortisol, which has been observed in
some stress related disorders such as Chronic Fatigue Syndrome (CFS).
CONCLUSION: Inclusion of pituitary GR expression resulted in a biologically
plausible model of HPA axis bistability and hypocortisolism. High GR
concentration enhanced cortisol negative feedback on the hypothalamus and forced
the HPA axis into an alternative, low cortisol state. This model can be used to
explore mechanisms underlying disorders of the HPA axis.
This model was taken from the CellML repository
and automatically converted to SBML.
The original model was:
Gupta S, Aslakson E, Gurbaxani BM, Vernon SD. (2007) - version=1.0
The original CellML model was created by:
Catherine Lloyd
c.lloyd@auckland.ac.nz
The University of Auckland
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To cite BioModels Database, please use: Li C, Donizelli M, Rodriguez N, Dharuri H, Endler L, Chelliah V, Li L, He E, Henry A, Stefan MI, Snoep JL, Hucka M, Le Novère N, Laibe C (2010) BioModels Database: An enhanced, curated and annotated resource for published quantitative kinetic models. BMC Syst Biol., 4:92.
Camille Laibe 
