title: Exercise training improves cardiac function-related gene levels through thyroid hormone receptor signaling in aged rats.
abstract: Exercise training improves the aging-induced downregulation of myosin heavy chain (MHC) and sarcoplasmic reticulum (SR) Ca(2+)-ATPase, which participate in the regulation of cardiac contraction and relaxation. Thyroid hormone receptor (TR), a transcriptional activator, affected the regulation of gene expression of MHC and SR Ca(2+)-ATPase. We hypothesized that myocardial TR signaling contributes to a molecular mechanism of exercise training-induced improvement of MHC and SR Ca(2+)-ATPase genes with cardiac function in old age. We investigated whether TR signaling and gene expression of MHC and SR Ca(2+)-ATPase in the aged heart are affected by exercise training, using the hearts of sedentary young rats (4 mo old), sedentary aged rats (23 mo old), and trained aged rats (23 mo old, swimming training for 8 wk). Trained aged rats showed improvement in cardiac function. Expression of TR-alpha1 and TR-beta1 proteins in the heart were significantly lower in sedentary aged rats than in sedentary young rats and were significantly higher in trained aged rats than in sedentary aged rats. The activity of TR DNA binding to the transcriptional regulatory region in the alpha-MHC and SR Ca(2+)-ATPase genes and the mRNA and protein expression of alpha-MHC and SR Ca(2+)-ATPase in the heart and plasma 3,3'-triiodothyronine and thyroxine levels were altered in association with changes in the myocardial TR protein levels. These findings suggest that exercise training improves the aging-induced downregulation of myocardial TR signaling-mediated transcription of MHC and SR Ca(2+)-ATPase genes, thereby contributing to the improvement of cardiac function in trained aged hearts.
authors.affiliation: Cardiovascular Division, Department of Internal Medicine, Institute of Clinical Medicine, University of Tsukuba, Tsukuba, Ibaraki 305-8575, Japan.
authors.forename: Motoyuki
authors.initials: M
authors.lastname: Iemitsu
authors.forename: Takashi
authors.initials: T
authors.lastname: Miyauchi
authors.forename: Seiji
authors.initials: S
authors.lastname: Maeda
authors.forename: Takumi
authors.initials: T
authors.lastname: Tanabe
authors.forename: Masakatsu
authors.initials: M
authors.lastname: Takanashi
authors.forename: Mitsuo
authors.initials: M
authors.lastname: Matsuda
authors.forename: Iwao
authors.initials: I
authors.lastname: Yamaguchi
mesh_terms: D000375:Aging / Q000502:physiology*; D000818:Animals; D000252:Calcium-Transporting ATPases / Q000235:genetics; D004247:DNA / Q000378:metabolism; D015870:Gene Expression / Q000502:physiology*; D006321:Heart / Q000502:physiology*; D008297:Male; D009206:Myocardium / Q000378:metabolism; D018995:Myosin Heavy Chains / Q000235:genetics; D010805:Physical Conditioning, Animal; D020033:Protein Isoforms / Q000235:genetics; D017434:Protein Structure, Tertiary / Q000502:physiology; D051381:Rats; D017208:Rats, Wistar; D011988:Receptors, Thyroid Hormone / Q000502:physiology*; D012519:Sarcoplasmic Reticulum / Q000201:enzymology; D015398:Signal Transduction / Q000502:physiology*; D013550:Swimming; D037021:Thyroid Hormone Receptors alpha / Q000378:metabolism; D037042:Thyroid Hormone Receptors beta / Q000378:metabolism; D013974:Thyroxine / Q000097:blood; D014284:Triiodothyronine / Q000097:blood
chemical_list: D020033:Protein Isoforms; D011988:Receptors, Thyroid Hormone; D037021:Thyroid Hormone Receptors alpha; D037042:Thyroid Hormone Receptors beta; D014284:Triiodothyronine; D004247:DNA; D018995:Myosin Heavy Chains; D000252:Calcium-Transporting ATPases; D013974:Thyroxine