title: Endothelin-1 regulates adiponectin gene expression and secretion in 3T3-L1 adipocytes via distinct signaling pathways.
abstract: Adiponectin, which is specifically and highly expressed in adipose tissue, has pleiotropic insulin-sensitizing effects. Endothelin-1 (ET-1) is a potent vasoconstrictive peptide mainly produced by endothelial cells. We previously showed that ET-1 can induce insulin resistance in vitro and in vivo and proposed that it might regulate adiponectin expression and secretion, thus affecting the homeostasis of whole-body energy metabolism. In the present study, we explored the regulatory effects of ET-1 on adiponectin expression and secretion and the underlying mechanisms in 3T3-L1 adipocytes using Northern blotting and ELISA. ET-1 was found to cause a significant time- and dose-dependent decrease in adiponectin expression, and this effect was inhibited by the ET type A receptor (ETAR) antagonist BQ-610 but not by the ETBR antagonist BQ-788. To explore the underlying mechanism, we examined the involvement of the cAMP-dependent protein kinase A-, phospholipase A2-, protein kinase C-, and MAPK-mediated pathways using inhibitors and found that only PD98059 and U0126, inhibitors that blocked MAPK/ERK kinase's ability to activate the ERKs, prevented ET-1-induced down-regulation of adiponectin. Furthermore, acute ET-1 treatment significantly stimulated adiponectin secretion by 3T3-L1 adipocytes, and this effect was inhibited by the ETAR antagonist BQ-610, the inositol-1,4,5-triphosphate receptor blocker 2-APB, and phospholipase C inhibitor U73122, showing that the release of adiponectin stimulated by ET-1 was mediated through the ETAR and the inositol-1,4,5-triphosphate pathway. In conclusion, ET-1 regulates adiponectin expression and secretion by two different signaling pathways in 3T3-L1 adipocytes. These findings suggested that the cardiovascular system affects adipocyte physiology by regulating the expression of adipocytokines and, consequently, energy homeostasis via vasoactive factors, such as ET-1.
authors.affiliation: Department of Physiology, School of Medicine, National Yang-Ming University, and Department of Medical Research and Education, Taipei Veterans General Hospital, Taipei, Taiwan. ccjuan@ym.edu.tw
authors.forename: Chi-Chang
authors.initials: CC
authors.lastname: Juan
authors.forename: Tung-Yueh
authors.initials: TY
authors.lastname: Chuang
authors.forename: Chih-Ling
authors.initials: CL
authors.lastname: Chang
authors.forename: Seng-Wong
authors.initials: SW
authors.lastname: Huang
authors.forename: Low-Tone
authors.initials: LT
authors.lastname: Ho
mesh_terms: D041721:3T3-L1 Cells; D017667:Adipocytes / Q000187:drug effects* / Q000378:metabolism; D052242:Adiponectin / Q000235:genetics* / Q000378:metabolism*; D000818:Animals; D020013:Calcium Signaling / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D019332:Endothelin-1 / Q000494:pharmacology* / Q000502:physiology; D048049:Extracellular Signal-Regulated MAP Kinases / Q000502:physiology; D005786:Gene Expression Regulation / Q000187:drug effects*; D007295:Inositol Phosphates / Q000502:physiology; D051379:Mice; D044022:Receptor, Endothelin A / Q000502:physiology; D015398:Signal Transduction; D013997:Time Factors
chemical_list: D052242:Adiponectin; D019332:Endothelin-1; D007295:Inositol Phosphates; D044022:Receptor, Endothelin A; C052128:inositol 3-phosphate; D048049:Extracellular Signal-Regulated MAP Kinases