Competitive and compensatory effects of androgen signaling and glucocorticoid signaling

Abstract

Androgens and glucocorticoids have competitive and compensatory effects in several physiological and pathophysiological processes. Although blood androgen levels affect blood glucocorticoid levels and vice versa, it does not fully explain the relationship between the effects of androgens and glucocorticoids. Androgens and glucocorticoids exert their functions through binding to androgen receptor (AR) and glucocorticoid receptor (GR), respectively. AR homodimer and GR homodimer bind to the androgen response element (ARE) and glucocorticoid response element (GRE), respectively, where they positively or negatively regulate transcription. AR/GR heterodimer can also form but whether it has a physiological role is unclear. Notably, some ARE/GRE sites are recognized by both AR and GR. This review focuses on the functional interventions between androgen signaling and glucocorticoid signaling in target cells that are involved in muscle atrophy, lipid metabolism in adipocytes and hepatocytes, and pancreatic β-cell death. Androgens and glucocorticoids exert opposite effects by differentially regulating key genes (e.g., insulin-like growth factor-1, atrogin-1, and thioredoxin-interacting protein) involved in these physiological processes. We also review functional compensation between these steroids in the development of castration-resistant prostate cancer in which glucocorticoids compensate for the castration-induced loss of AR function by activating key genes (e.g., serum/glucocorticoid-regulated kinase 1). The gene expressions regulated by androgens and glucocorticoids are regulated through at least three different mechanisms in target cells: (i) regulation of applicable ligand levels by modulation of steroid metabolite enzyme levels, (ii) regulation of each other's receptor levels, and (iii) competitive binding between AR and GR on ARE/GRE sites. Recent findings shed light on the complicated relationship between androgen signaling and glucocorticoid signaling in various cellular processes.