Peripheral clock system circadian abnormalities in Cushing’s disease

ABSTRACT

In Cushing’s syndrome, the cortisol rhythm is impaired and can be associated with the disruption in the rhythmic expression of clock genes. In this study, we evaluated the expression of CLOCK, BMAL1, CRY1, CRY2, PER1, PER2, PER3 genes in peripheral blood leukocytes of healthy individuals (n = 13) and Cushing’s disease (CD) patients (n = 12). Participants underwent salivary cortisol measurement at 0900 h and 2300 h. Peripheral blood samples were obtained at 0900 h, 1300 h, 1700 h, and 2300 h for assessing clock gene expression by qPCR. Gene expression circadian variations were evaluated by the Cosinor method. In healthy controls, a circadian variation in the expression of CLOCK, BMAL1, CRY1, PER2, and PER3 was observed, whereas the expression of PER1 and CRY2 followed no specific pattern. The expression of PER2 and PER3 in healthy leukocytes presented a late afternoon acrophase, similarly to CLOCK, whereas CRY1 showed night acrophase, similarly to BMAL1. In CD patients, the circadian variation in the expression of clock genes was lost, along with the abolition of cortisol circadian rhythm. However, CRY2 exhibited a circadian variation with acrophase during the dark phase in patients. In conclusion, our data suggest that Cushing’s disease, which is characterized by hypercortisolism, is associated with abnormalities in the circadian pattern of clock genes. Higher expression of CRY2 at night outlines its putative role in the cortisol circadian rhythm disruption.

KEYWORDS:

• circadian rhythm
• clock genes
• clock system
• Cushing’s disease
• Cushing’s syndrome
• glucocorticoid
• adrenal

Acknowledgements

We thank José Roberto Silva, Rogério Lenotti Zuliani, Renata Sicchieri Pugliesi, and Wendy Turatti for technical assistance; the post-doc Ana Carolina Bueno for scientific advice; and Professor Rodrigo Tocantins Calado for the English revision of the manuscript.

Disclosure of Interest

The authors report no conflict of interest.

Additional information

Funding

This research was supported by grants from the São Paulo Research Foundation (FAPESP) [grants no. 2014/03989-6 and 2016/2644-1] and the National Council of Technological and Scientific Development (Conselho Nacional de Desenvolvimento Científico e Tecnológico-CNPq) [grant no. 150983/2015-8].