Protein Restriction after Weaning Modifies the Calcium Kinetics and Induces Cardiomyocyte Contractile Dysfunction in Rats

Abstract

Protein restriction (PR) is associated with cardiovascular diseases. The purpose of this study was to investigate the effects on single ventricular cardiomyocyte contractile function of a short-term PR after weaning. Male Fischer rats that were 28 days old were randomly divided into a control group (CG, n = 16) and a protein-restricted group (PRG, n = 16). After weaning, CG and PRG animals received isocaloric diets containing 15 and 6% protein, respectively, for 35 days. Biometric parameters were then measured, and the hearts were removed for the analysis of contractile function and calcium transient in isolated cardiomyocytes of the left ventricule (LV), and the quantification of calcium and collagen fibers in LV myocardium. PRG animals had lower body weight (BW) and LV weight (LVW), an increased LVW to BW ratio and a higher proportion of collagen fibers than CG animals. PRG animals exhibited reduced tissue levels of calcium, reduced the length, width and volume of cardiomyocytes and their sarcomere length compared to CG animals. Cardiomyocytes from PRG animals had a lower amplitude of shortening, a slower time to the peak of shortening and a longer time to half-relaxation than those from the CG. Cardiomyocytes from PRG animals also presented a lower peak of calcium transient and a longer calcium transient decay time than CG animals. Taken together, the results indicate that short-term PR after weaning induces a marked structural remodeling of the myocardium parenchyma and stroma that coexists with contractile dysfunctions in single LV cardiomyocytes of rats, which is probably associated with pathological changes of the intracellular calcium kinetics, rather than inadequate available amounts of this mineral in cardiac tissue.

Changes in cardiovascular responses to chemoreflex activation of rats recovered from protein restriction are not related to AT1 receptors

“…; Penitente et al . ). Another important finding here is that recovery did not fully revert resting tachycardia, suggesting that abnormalities in chronotropic control are more profound and may not be reinstated to normal.…”

“…; Penitente et al . ). Data in the literature have also shown that increased sympathetic drive to the cardiovascular system can be associated with both an increase in the action of the renin–angiotensin system on peripheral mechanisms controlling circulation and changes in central pathways controlling the autonomic system.…”

Basal and �-Adrenergic Cardiomyocytes Contractility Dysfunction Induced by Dietary Protein Restriction is Associated with Downregulation of SERCA2a Expression and Disturbance of Endoplasmic Reticulum Ca2+Regulation in Rats

“…Several hypotheses have been suggested to explain the hemodynamic changes associated with malnutrition. Considering the model investigated, appears to be more relevant the hypothesis of reduced amino acids bioavailability, which is associated to structural abnormalities of the parenchyma and stroma in different organs of the cardiovascular system, especially the heart [2,9]. Furthermore, a lower efficiency in the synthesis of peptide regulatory molecules such as neurotransmitters, growth factors and intracellular signaling molecules can also directly associated with reduced amino acids levels [6].…”

“…The left ventricles (LV) were dissected and weighed separately [9]. The relative heart and LV weight was calculated by dividing the heart mass and LV mass by the tibia length (TL).…”

“…In this study, the initial evidences indicate that contractile insufficiency was probably associated with pathological changes of the intracellular calcium kinetics, rather than inadequate available amounts of this mineral in cardiac tissue [9]. …”