Hemin restores ACTH-induced glucocorticoid response in insulin-resistant rats

The sustained consumption of sucrose-rich diet has deleterious effects on the adrenal cortex, impairing its steroidogenic capacity. As hemin treatment has been shown to exert cytoprotective effects (e.g., by heme oxygenase 1 induction), our main goal was to analyze the adrenocortical function in rats treated with diet and hemin. Male Wistar rats fed standard chow and 30% sucrose in the drinking water (SRD) for 12 weeks ad libitum were injected with hemin for the last 2 weeks of treatment. mRNA and proteins were analyzed by real-time polymerase chain reaction, western blot or immunofluorescence, and corticosterone levels were assessed by radioimmunoassay. A decrease in lipid peroxides and an increase in the activity of catalase were detected in the SRD + H group. Moreover, pro-inflammatory markers (TNF-α, IL1β, CXCL10, NOS2, NALP3 and MCP1), IBA1+/ED1+ cells and NFκβ activation were still elevated in tissues from SRD + H-treated rats, whereas an increase in markers of macrophages with the M2-phenotype (ARG1, MRC1 and TGFβ) was also shown. Activation of ER stress in SRD-treated rats (CHOP, XBP1s and P58IPK) and the induction of apoptosis (TUNEL and the BAX/BCL2 mRNA ratio) were also attenuated by hemin. Finally, ACTH-stimulated glucocorticoid production, significantly decreased in SRD-treated rats, was upregulated by hemin. The consumption of SRD involves exposure of tissues to a higher metabolic load that could generate oxidative stress and a pro-inflammatory state. Deleterious consequences of these processes could account for the significant decrease in the ACTH-induced corticosterone output from the gland. By correcting these effects, hemin treatment was able to restore the hormone-induced adrenocortical response.