Long-term calorie restriction (CR) alters cardiac mechanics and energetics

CR decreases cardiac V1 and increases the Vs isoform, suggesting that diet may also alter cardiac mechanics and energetics. We examined) the effects of 8 months of CR or ad libitum feeding (AL) on the pressure-volume relationship and energetics of isolated perfused hearts from Fisher 344 rats. Isoproterenol (Iso) and changes in external calcium ion (Ca) were used to alter contractility. With low Ca, CR hearts developed significantly greater maximum pressures (65 ±3 mm Hg) than AL hearts (33 ±7 mm Hg); at higher Ca, the difference disappeared. Similarly, when Iso was used to increase contractility, the difference also disappeared. The oxygen consumption/tension developed and the O₂ cost of E-C coupling were unaffected by CR when Ca was altered. With Iso, hearts from CR rats exhibited a lower oxygen consumption/tension, but a higher cost for E-C coupling than observed in AL rats. Diet did not affect the basal oxygen consumption. Thus, CR produces adaptations in both cardiac mechanics and energetics. (Supported by grants AG01188, AG00469 and T32-AG-00205 from the NIH and the VA Research Service).