Endocrine Abstracts

Objective: Various effects of glucocorticoids occur in brown adipose tissue depending on their duration of action. As a result of exposure to glucocorticoids, thermogenesis and oxygen use in brown fat tissue are reduced in animal studies. In this study, we aimed to compare the levels of UCP1 (uncoupling protein 1), Irisin, BMP 7 (bone morpogenic protein), PRDM16, which are brown addipose tissue markers, between patients with Cushing’s disease and healthy controls

Methods: This study included 48 patients with Cushing’s disease and 40 non diabetic controls who met the inclusion criteria. Cushing syndrome was ruled out by performing 1 mg dexamethasone suppression test to individuals in the control group. Fasting blood samples were analyzed by Enzyme-Linked Immunosorbent Assay method for UCP1, Irisin, BMP 7 and PRDM 16. Demographic and clinical information was also recorded.

Results: There were 11 men (22.9%), 37 women (77.1%) in the patient group; 9 men (22.5%) and 31 women (77.5%) in the control group. Body mass index was 31.29 ± 5.76 kg/m² in the patient group, and 33.42 ± 3.11 kg/m² in the control group (P < 0,05). HbA1c and triglyceride levels were statistically significantly higher in patient group than in the control group (P < 0,05). PRDM16, Irisin, BMP7, UCP1 levels were not significantly different between the two groups (P > 0,05). Macroadenoma was detected in 19 (40.4%) patients and microadenoma in 28 (59.6%) patients in the Cushing disease group. Mean irisin, PRDM16 and BMP7 levels were similar in microadenoma and macroadenoma groups (P > 0,05). However, UCP1 was significantly higher in microadenoma group than macroadenoma group (P <0.05). There was a positive correlation between serum cortisol (morning and midnight cortisol ) with irisin (P < 0.05), but no correlation with other markers (P > 0.05). Also a positive correlation was observed between urine free cortisol and UCP1 levels (P < 0.05).

Conclusion: Short term exogenous glucocorticoid administration showed decreased levels of brown adipose tissue markers in animal studies. Opposite of this in our study, there was no difference between the patient and control groups in terms of brown adipose tissue markers. However,in patients with Cushing’s disease, UCP 1 and BMP7 were significantly correlated with increased cortisol levels. This finding may suggest that, prolonged exposure of high levels of endogenous cortisol causes loss of adipose tissue functionality by creating invivo resistance. It is obvious that detailed studies are needed to explain the effects of chronic cortisol exposure.