title: Testosterone and DHEA activate the glucose metabolism-related signaling pathway in skeletal muscle.
abstract: Circulating dehydroepiandrosterone (DHEA) is converted to testosterone or estrogen in the target tissues. Recently, we demonstrated that skeletal muscles are capable of locally synthesizing circulating DHEA to testosterone and estrogen. Furthermore, testosterone is converted to 5alpha-dihydrotestosterone (DHT) by 5alpha-reductase and exerts biophysiological actions through binding to androgen receptors. However, it remains unclear whether skeletal muscle can synthesize DHT from testosterone and/or DHEA and whether these hormones affect glucose metabolism-related signaling pathway in skeletal muscles. We hypothesized that locally synthesized DHT from testosterone and/or DHEA activates glucose transporter-4 (GLUT-4)-regulating pathway in skeletal muscles. The aim of the present study was to clarify whether DHT is synthesized from testosterone and/or DHEA in cultured skeletal muscle cells and whether these hormones affect the GLUT-4-related signaling pathway in skeletal muscles. In the present study, the expression of 5alpha-reductase mRNA was detected in rat cultured skeletal muscle cells, and the addition of testosterone or DHEA increased intramuscular DHT concentrations. Addition of testosterone or DHEA increased GLUT-4 protein expression and its translocation. Furthermore, Akt and protein kinase C-zeta/lambda (PKC-zeta/lambda) phosphorylations, which are critical in GLUT-4-regulated signaling pathways, were enhanced by testosterone or DHEA addition. Testosterone- and DHEA-induced increases in both GLUT-4 expression and Akt and PKC-zeta/lambda phosphorylations were blocked by a DHT inhibitor. Finally, the activities of phosphofructokinase and hexokinase, main glycolytic enzymes, were enhanced by testosterone or DHEA addition. These findings suggest that skeletal muscle is capable of synthesizing DHT from testosterone, and that DHT activates the glucose metabolism-related signaling pathway in skeletal muscle cells.
authors: Graduate School of Comprehensive Human Sciences, University of Tsukuba, Tsukuba, Ibaraki, Japan.
authors: Koji
authors: K
authors: Sato
authors: Motoyuki
authors: M
authors: Iemitsu
authors: Katsuji
authors: K
authors: Aizawa
authors: Ryuichi
authors: R
authors: Ajisaka
mesh_terms: D013741:3-Oxo-5-alpha-Steroid 4-Dehydrogenase / Q000378:metabolism; D000818:Animals; D003687:Dehydroepiandrosterone / Q000494:pharmacology*; D013196:Dihydrotestosterone / Q000378:metabolism; D005947:Glucose / Q000378:metabolism*; D051275:Glucose Transporter Type 4 / Q000096:biosynthesis / Q000235:genetics; D007527:Isoenzymes / Q000378:metabolism; D018482:Muscle, Skeletal / Q000187:drug effects*; D032446:Myoblasts / Q000187:drug effects; D051058:Oncogene Protein v-akt / Q000096:biosynthesis / Q000235:genetics; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism; D021381:Protein Transport / Q000187:drug effects; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction / Q000187:drug effects*; D013739:Testosterone / Q000494:pharmacology*; D000099293:Protein Kinase C-lambda; D000099221:Protein Kinase C zeta
chemical_list: D013741:3-Oxo-5-alpha-Steroid 4-Dehydrogenase; D003687:Dehydroepiandrosterone; D013196:Dihydrotestosterone; D005947:Glucose; D051275:Glucose Transporter Type 4; D007527:Isoenzymes; D051058:Oncogene Protein v-akt; D011493:Protein Kinase C; D013739:Testosterone; D000099293:Protein Kinase C-lambda; D000099221:Protein Kinase C zeta