Abstract

Introduction and Hypothesis: Restricted diets are effective interventions to enhance cardiovascular function and metabolic profile and are known to improve life spam. IF (Intemittent fasting) dietary regimen has a cardioprotective effect in a rat model of myocardial infarction (MI) when diet is started before MI induction. In heart failure (HF), upregulation of G protein-coupled receptor kinase 2 (GRK2) contributes to dysfunctional beta-adrenergic receptor (βAR) signaling and to decrease cardiac inotropic reserve. Moreover, it has been shown that caloric restriction has positive effects on the development of left ventricular hypertrophy and improves ischemic tolerance. Hence, we will test whether a long-term restricted diet, started late after MI, is beneficial in HF and how it could affect cardiac adrenergic signaling.

Methods: forty rats were randomly assigned to MI or sham operation. Four weeks later, a time point when post-ischemic HF was established, HF and sham rats were further randomized to a one year IF dietary restriction or ad libitum diet. Thus, our final animal population consisted in 4 groups: Sham normal diet, Sham IF diet, HF normal diet and HF IF diet.

Results: One year of IF diet induced a robust decrease in body weight. In HF groups, restricted diet resulted in improved cardiac systolic function and reduced left ventricle end diastolic diameter compared to HF rats fed with normal diet, as measured by echocardiography at the end of the study period. No differences in cardiac function and dimension were observed between sham groups treated with different diets. Consistently, invasive hemodynamic showed that both LV contractility and relaxation in response to βAR stimulation were significantly increased in IF HF rats compared to HF normal diet animals. IF diet resulted in improved cardiac βAR density and adenylyl cyclase activity in HF rats when compared to HF rats treated with standard diet. Restoration of βAR signaling was associated to a dramatic reduction in cardiac GRK2 protein levels.

Conclusions: We have demonstrated for the first time that IF, started when HF is already established, ameliorates cardiac function and inotropic reserve in an experimental model of HF. At the molecular level, IF diet significantly improves βAR signaling in HF.