The broad objective of this program is to perform preclinical experimentation on rodent models of myocardial ischemia to test the effect of dietary manipulations prior to an ischemic event to increase the tolerance of the cardiac tissue to ischemic damage. I. Alternative Day Fasting (ADF), i.e., the feeding regimen when ad lib food is available only every other day, had been reported to increase the lifespan and to reduce the incidence of age-associated diseases, including cancer, diabetes and kidney disease. We had shown the cardioprotective effect of ADF in rats using the model of experimental myocardial infarction induced by a permanent coronary ligation. While tissue protective properties of ADF have been proven, the effects of chronic ADF on general cardiovascular fitness remained unknown. At 4-mo of age, male SD rats were started on ADF or continued on ad libitum diets. Heart morphometry and function was followed for 6 months with serial echocardiography. At the end of the observation period, rats were subjected to a comprehensive hemodynamic evaluation via pressure-volume loop analyses including a combined dobutamine - volume stress test, and hearts were harvested for histological assessment. The six-month long ADF resulted in a 9% reduction (p<0.01) of cardiomyocyte diameter and 3 fold increase in interstitial myocardial fibrosis. Left ventricular chamber size was not affected in ADF and ejection fraction was not reduced. Left atrial diameter increased 16% in ADF, while E/A ratio in Doppler-measured mitral flow was reduced. Pressure-volume loop analyses in ADF revealed a stiff heart during diastole, and histological analyses demonstrated a 3-fold increase of myocardial fibrosis vs control hearts. Combined dobutamine and volume loading showed a significant reduction in LV diastolic compliance and a lack of increase in systolic pump function in ADF, indicating a diminished cardiac reserve. Thus chronic ADF in rats results in development of diastolic dysfunction with diminished cardiac reserve. Therefore, ADF is a novel and unique experimental model of behaviorally induced diastolic heart failure. The deleterious effect of ADF in rats warrants additional studies of ADF effect on cardiovascular function in humans. On the other hand, contrary to ADF, calorie restriction (CR) was not cardioprotective in the same experimental model. However, 24-mo old rats maintained throughout their life on 30% caloric reduction showed a lower degree of age-related myocardial hypertrophy and higher systolic function than their ad libitum-fed age control animals. While ad libitum-fed 24-mo old rats could not respond to dobutamine challenge by the heart rate increase, the 24-mo old CR animals demonstrated the proper heart rate response typical of younger animals. Moreover, 24-mo old CR rats had less myocardial fibrosis and less age-related loss of density of cardiomyocytes than ad libitum-fed age-matched control. Additionally, the CR rats had lower pulse wave velocity measured in aorta than AL animals, indicating lower arterial stiffness. However, CR did not prevent the age-related loss of cardiomyocytes. Thus, contrary to ADF, CR promoted cardiac fitness and delayed age-related changes in the cardio-vascular structure and function. II. Antioxidant supplement. Reactive oxygen species (ROS) play a major role in ischemia-related myocardial injury. However, attempts to use synthetic antioxidants to block the detrimental effects of ROS have produced mixed or negative results, precipitating the interest in antioxidants found in natural products. We had shown that adding blueberries to the diet (BD) resulted in a 24% increase (p<0.001) of ROS indexed tMPT compared with control diet (CD). Twenty-four hrs after coronary ligation, resulting myocardial infarction (MI) in rats on BD was 24% less than in CD rats (p<0.05). Significantly fewer TUNEL(+) cardiomyocytes (2% vs 9%) and 40% fewer inflammation cells were observed in the myocardial area at risk of BD compared to CD rats (p<0.05). We concluded that a blueberry-enriched diet protected the myocardium from ischemic damage and demonstrated the potential to attenuate the development of post-MI chronic heart failure. To test the hypothesis that BD will attenuate the course of chronic heart failure (CHF), we introduced blueberry-enriched diet to rats 2 weeks after inducing MI by permanent ligation of a coronary artery. The outcome was a 1-year mortality and cardiac remodeling. Two weeks after coronary artery ligation, rats were divided into two groups of similar average MI size, measured by echocardiography, and then 12-mo dietary regimens were initiated as follows: ad libitum regular diet (control, CD, n = 27) and isocaloric food with 2% blueberry supplement (BD, n = 27) also available ad libitum. These dietary groups were compared to each other and to a sham group (SH). Mortality over the 12 mo was reduced by 22% in BD compared with CD (p<0.01). In the course of developing CHF, BD had no effect on the body weight, heart rate or blood pressure. Bi-monthly Echo revealed significant attenuation of the LV chamber remodeling, LV posterior wall thinning, and MI expansion in BD compared with CD. In fact, BD arrested the MI expansion. These results represent the first experimental evidence that a blueberry-enriched diet has positive effects on the course of CHF and thus warrants consideration for clinical evaluation. Multiple health benefits of resveratrol, a red wine extract, are well documented in pre-clinical animal studies. The recently reported property of resveratrol as SIRT1 activator made it an attractive target for the management of chronic heart failure (CHF). In this experiment we tested the effect of long-term resveratrol supplement to a diet on mortality and progression of cardiaovascular remodeling in the rat model of post-myocardial infarct (MI) CHF in rats. Resveratrol enriched (5mg/kg/day) or normal ad-libitum diets were initiated two weeks after induction of MI by ligation of the left descending coronary artery in male Wistar rats and continued for 10 months. 10-mo mortality was similar in untreated MI rats (C, 65%) and rats treated with resveratrol (R, 61%). 77% expansion of MI over 10 months observed in C via serial echocardiography (Echo) was also not affected by resveratrol supplement. Dilatation of LV chamber (86% for end-diastolic pressure, and 135% for end-systolic pressure) and decline of ejection fraction (63%) observed in C via serial echo were progressively attenuated over time in R group;however, differences between groups never reached statistical significance. Arterial blood pressure measured monthly revealed small, but statistically significant reduction of systolic and pulse pressure in R vs C. Marked decline of cardiac function associated with MI shown by invasive hemodynamic assessments at the end of the 10-mo experiment and cross-sectional in subgroups of animals throughout the experiment was mostly not affected by resveratrol supplement with the exception of preload recruitable stroke work (603 vs. 404 in C;p<0.05) and arterial-ventricular coupling (1.10.1 vs. 2.70.7 in C;p<0.05), both of which were similar to that in Sham. Pulse wave velocity, increased by 35% in C compared to Sham, normalized in R starting with 4 months of treatment (p<0.05). Results indicate that resveratrol supplement produces some beneficial effects in the rat model of post-MI CHF suggesting its utility as an adjunct treatment to existing therapeutic regimen.
|Wan, Ruiqian; Ahmet, Ismayil; Brown, Martin et al. (2010) Cardioprotective effect of intermittent fasting is associated with an elevation of adiponectin levels in rats. J Nutr Biochem 21:413-7|
|Ahmet, Ismayil; Spangler, Edward; Shukitt-Hale, Barbara et al. (2009) Blueberry-enriched diet protects rat heart from ischemic damage. PLoS One 4:e5954|