Uncoupling of the sympathetic nervous system and the hypothalamic-pituitary-adrenal axis in inflammatory bowel disease?

In inflammatory diseases such as Crohn's disease (CD) and ulcerative colitis (UC), one would expect that TNF or IL-6 stimulates the hypothalamus, which activates the hypothalamus-autonomic nervous system (HANS) axis and the hypothalamic-pituitary-adrenal (HPA) axis in a parallel fashion. The study was initiated in order to investigate the parallelism of the HANS and HPA axes. We measured a typical marker of the HANS axis (neuropeptide Y, NPY) and of the HPA axis (serum cortisol). Plasma NPY was positively correlated with serum cortisol in control subjects (R(Rank)=0.259, p=0.026), which is a sign for the parallel activation of the two axes in healthy subjects. However, serum cortisol was not correlated with plasma NPY in CD or UC patients. In the active CD or UC, inclusion of patients with and without prior prednisolone therapy revealed a negative correlation between the serum cortisol and plasma NPY (CD: R(Rank)=-0.285, p<0.05; UC: R(Rank)=-0.510, p<0.01). This study demonstrates that the two stress axes seem to act in a parallel fashion in control subjects but are uncoupled in IBD patients. Uncoupling of these two axes may be partly due to prior corticosteroid therapy, whereas inverse coupling is a result of simultaneous corticosteroid therapy. It is discussed how the uncoupling of the two anti-inflammatory stress axes can appear.