title: Effects of age and aerobic fitness on myocardial lipid content.
abstract: BACKGROUND
  Aging and sedentary lifestyles lead to cardiac atrophy, ventricular stiffening, and impaired diastolic function. Both conditions are marked by increased adiposity, which can lead to ectopic fat deposition in nonadipocyte tissues including the myocardium. The effect of excess intramyocardial fat on cardiac function in nonobese individuals is unknown.
  
  
  RESULTS
  Cardiac lipid content was measured by magnetic resonance spectroscopy in 153 healthy nonobese subjects with varying fitness levels quantified by peak oxygen uptake during treadmill exercise. Cardiac function (echo) and left ventricular (LV) filling pressures (right heart catheterization) were measured under varying preloads. LV stiffness was calculated from a curve fit of the diastolic portion of the pressure-volume curve. The strongest clinical predictors of lipid content were body mass index (β=+0.03; 95% confidence interval, 0.001-0.06) and peak oxygen uptake (β=-0.02; 95% confidence interval, -0.03 to -0.009; R(2)=0.14; P<0.001). Subjects in the highest quintile had smaller LV end-diastolic volumes (68±13 versus 58±12 mL/m(2); P<0.01) and decreased peak early mitral annular and increased peak late mitral inflow velocities. There were no differences in LV stiffness, but a leftward shift in the pressure-volume curve suggested a less distensible ventricle with increasing myocardial lipid levels. After adjusting for age, fitness, and body mass index, echocardiographic and morphometric differences among groups were attenuated and no longer significant.
  
  
  CONCLUSIONS
  Body mass index and fitness levels are the strongest predictors of myocardial lipid content in nonobese humans. Cardiac lipid content is associated with decreased ventricular distensibility, and it may provide a causal mechanism linking changes in LV function related to age and fitness.
authors.affiliation: Institute for Exercise and Environmental Medicine, Texas Health Prebysterian Hospital, Dallas, TX.
authors.forename: Satyam
authors.initials: S
authors.lastname: Sarma
authors.forename: Graeme
authors.initials: G
authors.lastname: Carrick-Ranson
authors.forename: Naoki
authors.initials: N
authors.lastname: Fujimoto
authors.forename: Beverley
authors.initials: B
authors.lastname: Adams-Huet
authors.forename: Paul S
authors.initials: PS
authors.lastname: Bhella
authors.forename: Jeffrey L
authors.initials: JL
authors.lastname: Hastings
authors.forename: Keri M
authors.initials: KM
authors.lastname: Shafer
authors.forename: Shigeki
authors.initials: S
authors.lastname: Shibata
authors.forename: Kara
authors.initials: K
authors.lastname: Boyd
authors.forename: Dean
authors.initials: D
authors.lastname: Palmer
authors.forename: Edward W
authors.initials: EW
authors.lastname: Szczepaniak
authors.forename: Lidia S
authors.initials: LS
authors.lastname: Szczepaniak
authors.forename: Benjamin D
authors.initials: BD
authors.lastname: Levine
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology*; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test; D005260:Female; D006801:Humans; D008055:Lipids / Q000032:analysis*; D019028:Magnetic Resonance Imaging, Cine; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D008875:Middle Aged; D009206:Myocardium / Q000737:chemistry*; D012016:Reference Values; D013318:Stroke Volume; D016277:Ventricular Function, Left / Q000502:physiology*
chemical_list: D008055:Lipids
keywords: aging; exercise; ventricular remodeling
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