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Effects of Food Restriction on Systolic Mechanical Behavior of the Ventricular Pump in Middle-aged and Senescent Rats

^a Departments of Physiology, College of Medicine, National Taiwan University, Taipei, Taiwan
^b Departments of Internal Medicine, College of Medicine, National Taiwan University, Taipei, Taiwan

Kuo-Chu Chang, Department of Physiology, College of Medicine, National Taiwan University, No. 1, Sec. 1, Jen-Ai Rd., Taipei, Taiwan E-mail: kcchang{at}ha.mc.ntu.edu.tw.

Decision Editor: John A. Faulkner, PhD

Previous work from our laboratory has revealed that the intrinsic contractility of the left ventricle is depressed in rats at 24 months, and the ventricular internal resistance shows declines with age. The aim of this study was to determine whether food restriction (FR) delays the development of age-related changes in left ventricular (LV) contractility and internal resistance. Male Fischer 344 rats that began FR at the ages of 12 and 18 months were fed on alternate days for 6 months and compared with age-matched ad libitum (AL)-fed rats. Rats studied at the ages of 18 and 24 months were referred to as middle-aged and senescent rats, respectively, and were anesthetized and thoracotomized. We measured LV pressure and ascending aortic flow waves by using a high-fidelity pressure sensor and an electromagnetic flow probe, respectively. The elastance–resistance model was used to generate E_max and Q_max to describe the physical properties of the left ventricle; E_max is the maximal systolic elastance to represent the myocardial contractility; Q_max is the theoretical maximal flow to be inversely related to the LV internal resistance. Neither age nor diet affected basal heart rate, LV end-systolic pressure, or cardiac output. E_max normalized to LV weight (E_maxn) exhibited a decline from 941.9 ± 62.7 mmHg/ml-g to 690.2 ± 57.5 mmHg/ml-g with age in AL-fed rats but not FR rats. Q_max showed an increase with age from 36.55 ± 2.78 ml/s to 44.22 ± 2.62 ml/s in AL-fed rats or from 36.01 ± 2.09 ml/s to 43.52 ± 2.74 ml/s in FR rats. There was no effect of diet on Q_max. In conclusion, FR prevents or delays the reduction in myocardial contractility that occurred between 18 and 24 months of age in AL rats. However, FR does not affect the age-related changes in ventricular internal resistance.