title: Characterization of 5α-reductase activity and isoenzymes in human abdominal adipose tissues.
abstract: The substrate for the generation of 5α-dihydrotestosterone (DHT) is either androstenedione (4-dione) which is first converted to androstanedione and then to DHT through 17-oxoreductase activity, or testosterone, which is directly converted to DHT. Three 5α-reductase isoenzymes have been characterized and designated as types 1, 2 and 3 (SRD5A1, 2 and 3).
  
  
  
  To define the predominant source of local DHT production in human adipose tissues, identify 5α-reductase isoenzymes and test their impact on preadipocyte differentiation.
  
  
  
  Cultures of omental (OM) and subcutaneous (SC) preadipocytes were treated for 0, 6 or 24h with 30nM (14)C-4-dione or (14)C-testosterone, with and without 500nM 5α-reductase inhibitors 17-N,N-diethylcarbamoyl-4-methyl-4-aza-5-androstan-3-one (4-MA) or finasteride. Protein level and mRNA abundance of 5α-reductase isoenzymes/transcripts were examined in whole SC and OM adipose tissue. HEK-293 cells stably transfected with 5α-reductase type 1, 2 or 3 were used to test 5α-reductase inhibitors. We also assessed the impact of 5α-reductase inhibitors on preadipocyte differentiation.
  
  
  
  Over 24h, DHT formation from 4-dione increased gradually (p<0.05) and was significantly higher compared to that generated from testosterone (p<0.001). DHT formation from both 4-dione and testosterone was blocked by both 5α-reductase inhibitors. In whole adipose tissue from both fat compartments, SRD5A3 was the most highly expressed isoenzyme followed by SRD5A1 (p<0.001). SRD5A2 was not expressed. In HEK-293 cells, 4-MA and finasteride inhibited activity of 5α-reductases types 2 and 3 but not type 1. In preadipocyte cultures where differentiation was inhibited by 4-dione (p<0.05, n=7) or testosterone (p<0.05, n=5), the inhibitors 4-MA and finasteride abolished these effects.
  
  
  
  Although 4-dione is the main source of DHT in human preadipocytes, production of this steroid by 5α-reductase isoenzymes mediates the inhibitory effect of both 4-dione and testosterone on preadipocyte differentiation.
authors: Endocrinology and Nephrology, CHU de Québec Medical Center, Québec, Canada; Department of Biochemistry, Faculty of Veterinary Medicine, Zagazig University, Zagazig, Egypt.
authors: Mohamed
authors: M
authors: Fouad Mansour
authors: Endocrinology and Nephrology, CHU de Québec Medical Center, Québec, Canada; Québec Heart and Lung Institute Research Center, Laval University, Québec, Canada.
authors: Mélissa
authors: M
authors: Pelletier
authors: Endocrinology and Nephrology, CHU de Québec Medical Center, Québec, Canada; Québec Heart and Lung Institute Research Center, Laval University, Québec, Canada; School of Nutrition, Laval University, Québec, Canada. Electronic address: andre.tchernof@crchudequebec.ulaval.ca.
authors: André
authors: A
authors: Tchernof
mesh_terms: D013741:3-Oxo-5-alpha-Steroid 4-Dehydrogenase / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D050153:Abdominal Fat / Q000166:cytology / Q000201:enzymology* / Q000378:metabolism; D050156:Adipogenesis; D000735:Androstenedione / Q000378:metabolism; D002478:Cells, Cultured; D013196:Dihydrotestosterone / Q000378:metabolism; D015870:Gene Expression; D057809:HEK293 Cells; D006801:Humans; D008297:Male; D008565:Membrane Proteins / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D008875:Middle Aged; D012333:RNA, Messenger / Q000235:genetics
chemical_list: D008565:Membrane Proteins; D012333:RNA, Messenger; D013196:Dihydrotestosterone; D000735:Androstenedione; D013741:3-Oxo-5-alpha-Steroid 4-Dehydrogenase; C548467:SRD5A1 protein, human; C548468:SRD5A2 protein, human; C548469:SRD5A3 protein, human
keywords: 5α-reductase; Adipose tissue; Androstenedione; Dihydrotestosterone; Testosterone