Impact of Endogenous and Exogenous Alterations of Glucocorticoids on the Derangement of Clock-related Genes in Peripheral Mononuclear Cells

Abstract
Circadian clock genes regulate the physiological sensitivity to rhythmic release of glucocorticoids (GCs). In turn, GCs have reciprocal effects on circadian system. Conditions affected by hyper- or hypocortisolism are characterized by a loss of circadian rhythmicity. Loss or impairment of circadian rhythms have been reportedly associated with malignancies and an increased incidence of infectious diseases, suggesting a role of immune function alterations. Adrenal insufficiency (AI) requires life-long glucocorticoid replacement. Conventional therapies fail to mimic the endogenous cortisol circadian rhythm. Objective of this study was to evaluate the effect of the timing of GC administration on circadian gene expression in peripheral blood mononuclear cells (PBMCs) of AI patients from DREAM trial. Patients were randomly assigned to continue their multiple daily doses, or switch to an equivalent dose of once-daily modified-release hydrocortisone, and compared to healthy controls. Circadian genes in PBMC were analyzed by quantitative by real-time qRT-PCR using predesigned 96-well panel SYBR® Green Circadian rhythms (SAB Target List) H96 (Bio-Rad, PrimePCR®). Compared to healthy controls, 19 of the 68 genes were found differentially expressed in AI patients at baseline, 18 of which were restored to control levels 12 week after switching therapy, comprising: ARNTL, CLOCK, PER3, TIMELESS, AANAT, CAMK2D, CREB1, CREB3, MAPK1, WEE1, PRF1. Changes in WEE1, PRF1 and PER3 expression correlated with change in clinical outcomes including glycated hemoglobin, inflammatory monocytes and CD16+ NK cells, suggesting that the extent of reprogramming of circadian gene expression can be linked to the magnitude of improvement in clinically measurable outcomes. In conclusionAIpatients on standard therapy exhibit a dysregulation of circadian genes in PBMCs. The once-daily administration reconditions peripheral tissue gene expression to levels close to healthy controls, and correlates with clinical improvement.