Calorie restriction delays cardiac senescence and improves cardiac function in obese diabetic rats

The aims of this study were to investigate the impact of caloric restriction (CR) on cardiac senescence in an animal model of diabetes and examine the signal transduction mechanisms for changes in cell survival as well as cardiac function. Male 8-week-old Otsuka Long-Evans Tokushima fatty (OLETF) diabetic rats were divided into 2 groups: a group fed ad libitum (AL), and a group fed with CR (30% energy reduction). Long-Evans Tokushima Otsuka (LETO) non-diabetic rats were used as controls. LETO rats were divided into 3 groups: a high fat diet (HFD) group with a 22% increase in caloric intake, a CR group, and a group fed AL. At 40 weeks of age, the telomere length was significantly shorter in the heart tissue of HFD rats but was not altered by CR in experimental rats with or without CR, however, telomerase activity in both strains of CR rats was significantly elevated. Protein expression of IGF-1, Sirt 1 and phospho-FoxO1 was increased in both CR groups. Echocardiography showed that CR preserved LV diastolic function with a significantly shorter E-wave deceleration time and a greater E/A ratio compared with the AL groups. These findings suggest that CR protocol increased telomerase activity without changing of telomere length, enhanced autophagy and improved LV diastolic function in animal model of diabetes rats. It is finally suggested that those impacts may be important for the maintenance of normal cardiac function and for delayed cardiac aging.