title: Left ventricular mechanical dysfunction in diet-induced obese mice is exacerbated during inotropic stress: a cine DENSE cardiovascular magnetic resonance study.
abstract: BACKGROUND
  Obesity is a risk factor for cardiovascular disease. There is evidence of impaired left ventricular (LV) function associated with obesity, which may relate to cardiovascular mortality, but some studies have reported no dysfunction. Ventricular function data are generally acquired under resting conditions, which could mask subtle differences and potentially contribute to these contradictory findings. Furthermore, abnormal ventricular mechanics (strains, strain rates, and torsion) may manifest prior to global changes in cardiac function (i.e., ejection fraction) and may therefore represent more sensitive markers of cardiovascular disease. This study evaluated LV mechanics under both resting and stress conditions with the hypothesis that the LV mechanical dysfunction associated with obesity is exacerbated with stress and manifested at earlier stages of disease compared to baseline.
  
  
  METHODS
  C57BL/6J mice were randomized to a high-fat or control diet (60 %, 10 % kcal from fat, respectively) for varying time intervals (n = 7 - 10 subjects per group per time point, 100 total; 4 - 55 weeks on diet). LV mechanics were quantified under baseline (resting) and/or stress conditions (40 μg/kg/min continuous infusion of dobutamine) using cine displacement encoding with stimulated echoes (DENSE) with 7.4 ms temporal resolution on a 7 T Bruker ClinScan. Peak strain, systolic strain rates, and torsion were quantified. A linear mixed model was used with Benjamini-Hochberg adjustments for multiple comparisons.
  
  
  RESULTS
  Reductions in LV peak longitudinal strain at baseline were first observed in the obese group after 42 weeks, with no differences in systolic strain rates or torsion. Conversely, reductions in longitudinal strain and circumferential and radial strain rates were seen under inotropic stress conditions after only 22 weeks on diet. Furthermore, stress cardiovascular magnetic resonance (CMR) evaluation revealed supranormal values of LV radial strain and torsion in the obese group early on diet, followed by later deficits.
  
  
  CONCLUSIONS
  Differences in left ventricular mechanics in obese mice are exacerbated under stress conditions. Stress CMR demonstrated a broader array of mechanical dysfunction and revealed these differences at earlier time points. Thus, it may be important to evaluate cardiac function in the setting of obesity under stress conditions to fully elucidate the presence of ventricular dysfunction.
authors: Saha Cardiovascular Research Center, University of Kentucky, Lexington, KY, USA. chaggerty3@gatech.edu.|Department of Pediatrics, University of Kentucky, Lexington, KY, USA. chaggerty3@gatech.edu.|Geisinger Health System, Institute for Advanced Application, 100 North Academy Avenue, Danville, PA, 17822, USA. chaggerty3@gatech.edu.
authors: Christopher M
authors: CM
authors: Haggerty
authors: Saha Cardiovascular Research Center, University of Kentucky, Lexington, KY, USA. acma242@g.uky.edu.|Department of Pediatrics, University of Kentucky, Lexington, KY, USA. acma242@g.uky.edu.
authors: Andrea C
authors: AC
authors: Mattingly
authors: College of Medicine, University of Kentucky, Lexington, KY, USA. s.kramer@uky.edu.
authors: Sage P
authors: SP
authors: Kramer
authors: Department of Physiology, University of Kentucky, Lexington, KY, USA. cassi.binkley@uky.edu.|Geisinger Health System, Institute for Advanced Application, 100 North Academy Avenue, Danville, PA, 17822, USA. cassi.binkley@uky.edu.
authors: Cassi M
authors: CM
authors: Binkley
authors: Saha Cardiovascular Research Center, University of Kentucky, Lexington, KY, USA. ljing@geisinger.edu.|Department of Pediatrics, University of Kentucky, Lexington, KY, USA. ljing@geisinger.edu.|Geisinger Health System, Institute for Advanced Application, 100 North Academy Avenue, Danville, PA, 17822, USA. ljing@geisinger.edu.
authors: Linyuan
authors: L
authors: Jing
authors: Saha Cardiovascular Research Center, University of Kentucky, Lexington, KY, USA. jdsuever@geisinger.edu.|Department of Pediatrics, University of Kentucky, Lexington, KY, USA. jdsuever@geisinger.edu.|Geisinger Health System, Institute for Advanced Application, 100 North Academy Avenue, Danville, PA, 17822, USA. jdsuever@geisinger.edu.
authors: Jonathan D
authors: JD
authors: Suever
authors: Department of Biomedical Engineering, University of Kentucky, Lexington, KY, USA. david.k.powell@uky.edu.
authors: David K
authors: DK
authors: Powell
authors: Department of Biostatistics, University of Kentucky, Lexington, KY, USA. rjcharn2@aol.com.
authors: Richard J
authors: RJ
authors: Charnigo
authors: Departments of Biomedical Engineering and Radiology, University of Virginia, Charlottesville, VA, USA. FHE6B@hscmail.mcc.virginia.edu.
authors: Frederick H
authors: FH
authors: Epstein
authors: Saha Cardiovascular Research Center, University of Kentucky, Lexington, KY, USA. bkf@gatech.edu.|Department of Pediatrics, University of Kentucky, Lexington, KY, USA. bkf@gatech.edu.|Department of Physiology, University of Kentucky, Lexington, KY, USA. bkf@gatech.edu.|Department of Biomedical Engineering, University of Kentucky, Lexington, KY, USA. bkf@gatech.edu.|Geisinger Health System, Institute for Advanced Application, 100 North Academy Avenue, Danville, PA, 17822, USA. bkf@gatech.edu.
authors: Brandon K
authors: BK
authors: Fornwalt
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D002316:Cardiotonic Agents / Q000008:administration & dosage*; D059305:Diet, High-Fat; D004195:Disease Models, Animal; D004280:Dobutamine / Q000008:administration & dosage*; D007262:Infusions, Intravenous; D016014:Linear Models; D019028:Magnetic Resonance Imaging, Cine; D008297:Male; D008810:Mice, Inbred C57BL; D009200:Myocardial Contraction / Q000187:drug effects*; D009765:Obesity / Q000150:complications*; D011237:Predictive Value of Tests; D012307:Risk Factors; D013314:Stress, Mechanical; D013312:Stress, Physiological; D013997:Time Factors; D054159:Torsion, Mechanical; D018487:Ventricular Dysfunction, Left / Q000175:diagnosis* / Q000209:etiology / Q000503:physiopathology; D016277:Ventricular Function, Left / Q000187:drug effects*
chemical_list: D002316:Cardiotonic Agents; D004280:Dobutamine