title: Cardiac-specific elevations in thyroid hormone enhance contractility and prevent pressure overload-induced cardiac dysfunction.
abstract: Thyroid hormone (TH) is critical for cardiac development and heart function. In heart disease, TH metabolism is abnormal, and many biochemical and functional alterations mirror hypothyroidism. Although TH therapy has been advocated for treating heart disease, a clear benefit of TH has yet to be established, possibly because of peripheral actions of TH. To assess the potential efficacy of TH in treating heart disease, type 2 deiodinase (D2), which converts the prohormone thyroxine to active triiodothyronine (T3), was expressed transiently in mouse hearts by using the tetracycline transactivator system. Increased cardiac D2 activity led to elevated cardiac T3 levels and to enhanced myocardial contractility, accompanied by increased Ca(2+) transients and sarcoplasmic reticulum (SR) Ca(2+) uptake. These phenotypic changes were associated with up-regulation of sarco(endo)plasmic reticulum calcium ATPase (SERCA) 2a expression as well as decreased Na(+)/Ca(2+) exchanger, beta-myosin heavy chain, and sarcolipin (SLN) expression. In pressure overload, targeted increases in D2 activity could not block hypertrophy but could completely prevent impaired contractility and SR Ca(2+) cycling as well as altered expression patterns of SERCA2a, SLN, and other markers of pathological hypertrophy. Our results establish that elevated D2 activity in the heart increases T3 levels and enhances cardiac contractile function while preventing deterioration of cardiac function and altered gene expression after pressure overload.
authors.affiliation: Heart and Stroke/Richard Lewar Centre and Departments of Physiology and Medicine, University of Toronto, Toronto, ON, Canada M5S 3E2.
authors.forename: Maria Giovanna
authors.initials: MG
authors.lastname: Trivieri
authors.forename: Gavin Y
authors.initials: GY
authors.lastname: Oudit
authors.forename: Rajan
authors.initials: R
authors.lastname: Sah
authors.forename: Benoit-Gilles
authors.initials: BG
authors.lastname: Kerfant
authors.forename: Hui
authors.initials: H
authors.lastname: Sun
authors.forename: Anthony O
authors.initials: AO
authors.lastname: Gramolini
authors.forename: Yan
authors.initials: Y
authors.lastname: Pan
authors.forename: Alan D
authors.initials: AD
authors.lastname: Wickenden
authors.forename: Walburga
authors.initials: W
authors.lastname: Croteau
authors.forename: Gabriella
authors.initials: G
authors.lastname: Morreale de Escobar
authors.forename: Roman
authors.initials: R
authors.lastname: Pekhletski
authors.forename: Donald
authors.initials: D
authors.lastname: St Germain
authors.forename: David H
authors.initials: DH
authors.lastname: Maclennan
authors.forename: Peter H
authors.initials: PH
authors.lastname: Backx
mesh_terms: D000818:Animals; D001794:Blood Pressure / Q000502:physiology; D020013:Calcium Signaling; D000252:Calcium-Transporting ATPases / Q000235:genetics / Q000378:metabolism; D015971:Gene Expression Regulation, Enzymologic; D005838:Genotype; D006321:Heart / Q000502:physiology*; D006331:Heart Diseases / Q000503:physiopathology*; D006706:Homeostasis; D007453:Iodide Peroxidase / Q000235:genetics* / Q000378:metabolism; D009200:Myocardial Contraction / Q000502:physiology*; D051381:Rats; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D013974:Thyroxine / Q000502:physiology*; D014284:Triiodothyronine / Q000502:physiology*; D000097564:Iodothyronine Deiodinase Type II
chemical_list: D000252:Calcium-Transporting ATPases; D007453:Iodide Peroxidase; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D013974:Thyroxine; D014284:Triiodothyronine; D000097564:Iodothyronine Deiodinase Type II