The effects of exercise training and caloric restriction on the cardiac oxytocin natriuretic peptide system in the diabetic mouse
Authors Broderick TL, Jankowski M, Gutkowska J
Received 21 June 2016
Accepted for publication 18 November 2016
Published 11 January 2017 Volume 2017:10 Pages 27—36
Checked for plagiarism Yes
Review by Single-blind
Peer reviewers approved by Dr Lucy Goodman
Peer reviewer comments 4
Editor who approved publication: Professor Ming-Hui Zou
Tom L Broderick,1 Marek Jankowski,2 Jolanta Gutkowska2
1Department of Physiology, Laboratory of Diabetes and Exercise Metabolism, Midwestern University, Glendale, AZ, USA; 2Department of Medicine, Laboratory of Cardiovascular Biochemistry, Centre Hospitalier de l‘Université de Montréal-Hôtel-Dieu, Montréal, QC, Canada
Background: Regular exercise training (ET) and caloric restriction (CR) are the frontline strategies in the treatment of type 2 diabetes mellitus with the aim at reducing cardiometabolic risk. ET and CR improve body weight and glycemic control, and experimental studies indicate that these paradigms afford cardioprotection. In this study, the effects of combined ET and CR on the cardioprotective oxytocin (OT)–natriuretic peptide (NP) system were determined in the db/db mouse, a model of type 2 diabetes associated with insulin resistance, hyperglycemia, and obesity.
Methods: Five-week-old male db/db mice were assigned to the following groups: sedentary, ET, and ET + CR. Nonobese heterozygote littermates served as controls. ET was performed on a treadmill at moderate intensity, and CR was induced by reducing food intake by 30% of that consumed by sedentary db/db mice for a period of 8 weeks.
Results: After 8 weeks, only ET + CR, but not ET, slightly improved body weight compared to sedentary db/db mice. Regardless of the treatment, db/db mice remained hyperglycemic. Hearts from db/db mice demonstrated reduced expression of genes linked to the cardiac OT–NP system. In fact, compared to control mice, mRNA expression of GATA binding protein 4 (GATA4), OT receptor, OT, brain NP, NP receptor type C, and endothelial nitric oxide synthase (eNOS) was decreased in hearts from sedentary db/db mice. Both ET alone and ET + CR increased the mRNA expression of GATA4 compared to sedentary db/db mice. Only ET combined with CR produced increased eNOS mRNA and protein expression.
Conclusion: Our data indicate that enhancement of eNOS by combined ET and CR may improve coronary endothelial vasodilator dysfunction in type 2 diabetes but did not prevent the downregulation of cardiac expression in the OT–NP system, possibly resulting from the sustained hyperglycemia and obesity in diabetic mice.
Keywords: running, diabetes, GATA4, oxytocin, natriuretic peptides, db/db
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