title: Adiponectin is required for cardiac MEF2 activation during pressure overload induced hypertrophy.
abstract: Cardiomyocyte (CM) hypertrophy and increased heart mass in response to pressure overload are associated with hyper-activation of the myocyte enhancer factor-2 (MEF2) family of transcriptional regulators, and concomitant initiation of the fetal gene program. Adiponectin, an adipokine that is reduced in individuals with obesity and diabetes, has been characterized both as a negative regulator or permissive factor in cardiac hypertrophy. We therefore sought to analyze temporal regulation of MEF2 activity in response to pressure overload (PO) and changes in adiponectin status. To address this we crossed a well characterized transgenic MEF2 "sensor" mouse (MEF2-lacZ) with adiponectin null mice (Ad-KO) to create compound MEF2 lacZ/Ad-KO mice. Initially, we established that transverse aortic banding induced PO in wild-type (WT) mice increased heart mass and CM hypertrophy from 1 to 4weeks following surgery, indicated by increased CM diameter and heart weight/tibia length ratio. This was associated with cardiac dysfunction determined by echocardiography. Hypertrophic changes and dysfunction were observed in Ad-KO mice 4weeks following surgery. MEF2 lacZ activity and endogenous ANF mRNA levels, used as indicators of hypertrophic gene activation, were both robustly increased in WT mice after MTAB but attenuated in the Ad-KO background. Furthermore, activation of the pro-hypertrophic molecule p38 was increased following MTAB surgery in WT mice, but not in Ad-KO animals, and treatment of primary isolated CM with recombinant adiponectin induced p38 phosphorylation in a time dependent manner. Adiponectin also increased MEF2 activation in primary cardiomyocytes, an effect attenuated by p38 MAPK inhibition. In conclusion, our data indicate that robust hypertrophic MEF2 activation in the heart in vivo requires a background of adiponectin signaling and that adiponectin signaling in primary isolated CM directly enhances MEF2 activity through activation of p38 MAPK. We conclude that adiponectin is required for full induction of cardiomyocyte MEF2 activation, thus contributing to the myocardial hypertrophic gene expression program in response to PO.
authors.affiliation: Department of Biology, York University, Toronto, Canada.
authors.forename: Keith
authors.initials: K
authors.lastname: Dadson
authors.affiliation: Department of Biology, York University, Toronto, Canada.
authors.forename: Subat
authors.initials: S
authors.lastname: Turdi
authors.affiliation: Department of Biology, York University, Toronto, Canada.
authors.forename: Sarah
authors.initials: S
authors.lastname: Hashemi
authors.affiliation: Department of Biology, York University, Toronto, Canada.
authors.forename: Jianzhong
authors.initials: J
authors.lastname: Zhao
authors.affiliation: Department of Physiology, University of Toronto, Toronto, Ontario, Canada; Department of Medicine, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Nazar
authors.initials: N
authors.lastname: Polidovitch
authors.affiliation: Department of Physiology, University of Toronto, Toronto, Ontario, Canada; Department of Medicine, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Sanja
authors.initials: S
authors.lastname: Beca
authors.affiliation: Department of Physiology, University of Toronto, Toronto, Ontario, Canada; Department of Medicine, University of Toronto, Toronto, Ontario, Canada; Peter Munk Cardiac Centre and the Division of Cardiology, University Health Network,Toronto, Ontario, Canada.
authors.forename: Peter H
authors.initials: PH
authors.lastname: Backx
authors.affiliation: Department of Biology, York University, Toronto, Canada.
authors.forename: John C
authors.initials: JC
authors.lastname: McDermott
authors.affiliation: Department of Biology, York University, Toronto, Canada. Electronic address: gsweeney@yorku.ca.
authors.forename: Gary
authors.initials: G
authors.lastname: Sweeney
mesh_terms: D052242:Adiponectin / Q000235:genetics* / Q000378:metabolism; D000818:Animals; D006332:Cardiomegaly / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D005786:Gene Expression Regulation; D006801:Humans; D064326:MEF2 Transcription Factors / Q000235:genetics* / Q000378:metabolism; D051379:Mice; D008822:Mice, Transgenic; D032383:Myocytes, Cardiac / Q000378:metabolism / Q000473:pathology; D011312:Pressure; D015398:Signal Transduction; D048051:p38 Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism
chemical_list: D052242:Adiponectin; D064326:MEF2 Transcription Factors; D048051:p38 Mitogen-Activated Protein Kinases
keywords: Adiponectin; Cardiomyocyte; Hypertrophy; Myocyte enhancer factor-2 (MEF-2); Pressure overload