title: Dihydrotestosterone regulating apolipoprotein M expression mediates via protein kinase C in HepG2 cells.
abstract: BACKGROUND
  Administration of androgens decreases plasma concentrations of high-density lipid cholesterol (HDL-C). However, the mechanisms by which androgens mediate lipid metabolism remain unknown. This present study used HepG2 cell cultures and ovariectomized C57BL/6 J mice to determine whether apolipoprotein M (ApoM), a constituent of HDL, was affected by dihydrotestosterone (DHT).
  
  
  METHODS
  HepG2 cells were cultured in the presence of either DHT, agonist of protein kinase C (PKC), phorbol-12-myristate-13-acetate (PMA), blocker of androgen receptor flutamide together with different concentrations of DHT, or DHT together with staurosporine at different concentrations for 24 hrs. Ovariectomized C57BL/6 J mice were treated with DHT or vehicle for 7d or 14d and the levels of plasma ApoM and livers ApoM mRNA were measured. The mRNA levels of ApoM, ApoAI were determined by real-time RT-PCR. ApoM and ApoAI were determined by western blotting analysis.
  
  
  RESULTS
  Addition of DHT to cell culture medium selectively down-regulated ApoM mRNA expression and ApoM secretion in a dose-dependent manner. At 10 nM DHT, the ApoM mRNA levels were about 20% lower than in untreated cells and about 40% lower at 1000 nM DHT than in the control cells. The secretion of ApoM into the medium was reduced to a similar extent. The inhibitory effect of DHT on ApoM secretion was not blocked by the classical androgen receptor blocker flutamide but by an antagonist of PKC, Staurosporine. Agonist of PKC, PMA, also reduced ApoM. At 0.5 μM PMA, the ApoM mRNA levels and the secretion of ApoM into the medium were about 30% lower than in the control cells. The mRNA expression levels and secretion of another HDL-associated apolipoprotein AI (ApoAI) were not affected by DHT. The levels of plasma ApoM and liver ApoM mRNA of DHT-treated C57BL/6 J mice were lower than those of vehicle-treated mice.
  
  
  CONCLUSIONS
  DHT directly and selectively down-regulated the level of ApoM mRNA and the secretion of ApoM by protein kinase C but independently of the classical androgen receptor.
authors.affiliation: Department of Cardiovascular Surgery, Affiliated Shanghai 1st People’s Hospital, Shanghai Jiaotong University, Shanghai 210008, People's Republic of China.
authors.forename: Ye
authors.initials: Y
authors.lastname: Yi-zhou
authors.forename: Cao
authors.initials: C
authors.lastname: Bing
authors.forename: Li
authors.initials: L
authors.lastname: Ming-qiu
authors.forename: Wang
authors.initials: W
authors.lastname: Wei
authors.forename: Wang
authors.initials: W
authors.lastname: Ru-xing
authors.forename: Rui
authors.initials: R
authors.lastname: Jun
authors.forename: Wei
authors.initials: W
authors.lastname: Liu-yan
authors.forename: Jing
authors.initials: J
authors.lastname: Zhao-hui
authors.forename: Ji
authors.initials: J
authors.lastname: Yong
authors.forename: Jiao
authors.initials: J
authors.lastname: Guo qing
authors.forename: Zou
authors.initials: Z
authors.lastname: Jian
mesh_terms: D000818:Animals; D001053:Apolipoproteins / Q000096:biosynthesis / Q000097:blood / Q000378:metabolism; D000075243:Apolipoproteins M; D008076:Cholesterol, HDL / Q000378:metabolism; D013196:Dihydrotestosterone / Q000378:metabolism / Q000494:pharmacology; D015536:Down-Regulation; D015870:Gene Expression / Q000187:drug effects; D056945:Hep G2 Cells; D006801:Humans; D050356:Lipid Metabolism / Q000187:drug effects*; D054834:Lipocalins / Q000096:biosynthesis / Q000097:blood / Q000378:metabolism; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D010703:Phorbol Esters / Q000494:pharmacology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*; D012333:RNA, Messenger / Q000096:biosynthesis / Q000378:metabolism; D011944:Receptors, Androgen / Q000378:metabolism
chemical_list: C400523:APOM protein, human; D001053:Apolipoproteins; D000075243:Apolipoproteins M; D008076:Cholesterol, HDL; D054834:Lipocalins; D010703:Phorbol Esters; D012333:RNA, Messenger; D011944:Receptors, Androgen; D013196:Dihydrotestosterone; C032974:12-O-retinoylphorbol-13-acetate; D011493:Protein Kinase C