The role adipose tissue in development of insulin resistance and other metabolic disorders in patients with pheochromocytoma

Pheochromocytoma and functional paraganglioma (PPGL) are rare neuroendocrine tumors characterized by catecholamines overproduction, which give a rise to disorders of glucose, lipid, and energy metabolism. The role of adipose tissue in these processes remains unclear. Our aim was to determine the gene expression profile in subcutaneous and visceral adipose tissue of patients with PPGL focusing on endocrine functions of adipose tissue, occurrence of brown (BAT) and beige adipose tissue (BeAT), all in connection with other measured metabolic and energy parameters and levels of circulating adipokines. We demonstrate signs of UCP1-dependent norepinephrine induced thermogenesis connected with overexpression of DIO2 in retroperitoneal VAT of PPGL and higher expression of key transcriptional factors of brown/beige adipogenesis, namely PPARGC1α, CEBPB and PRDM16. However, classic murine BAT or BeAT gene signature in VAT of PPGL was not detected. In subcutaneous adipose tissue (SAT) of PPGL we found signs of possible BeAT transformation, however without simultaneously undergoing UCP1-dependent thermogenesis. We also demonstrate that patients with PPGL have higher serum levels of FGF21 compared to healthy controls and these levels do not differ from obese patients. Furthermore, successful tumor removal..