Mechanisms of Action of Dehydroepiandrosterone

Dehydroepiandrosterone (3 beta-hydroxy-5-androsten-17-one, DHEA) and its sulfated metabolite DHEA-S are the most abundant steroids in circulation and decline with age. Rodent studies have shown that DHEA has a wide variety of effects on liver, kidney, adipose, reproductive tissues, and central nervous system/neuronal function. The mechanisms by which DHEA and DHEA-S impart their physiological effects may be direct actions on plasma membrane receptors, including a DHEA-specific, G-protein-coupled receptor in endothelial cells; various neuroreceptors, e.g., aminobutyric-acid-type A, N-methyl-D-aspartate (NMDA), and sigma-1 (S1R) receptors; by binding steroid receptors: androgen and estrogen receptors (ARs, ER alpha, or ER beta); or by their metabolism to more potent sex steroid hormones, e.g., testosterone, dihydrotestosterone, and estradiol, which bind with higher affinity to ARs and ERs. DHEA inhibits voltage-gated T-type calcium channels. DHEA activates peroxisome proliferator-activated receptor (PPAR alpha) and CAR by a mechanism apparently involving PP2A, a protein phosphatase dephosphorylating PPAR alpha and CAR to activate their transcriptional activity. We review our recent study showing DHEA activated GPER1 (G-protein-coupled estrogen receptor 1) in HepG2 cells to stimulate miR-21 transcription. This chapter reviews some of the physiological, biochemical, and molecular mechanisms of DHEA and DHEA-S activity.