Behavioral, dietary and pharmacological modalities of cardioprotection

心脏保护的行为、饮食和药理学方式

• 批准号: 8148333
• 负责人: Mark Talan
• 金额: $ 18.5万
• 依托单位: NATIONAL INSTITUTE ON AGING
• 依托单位国家: 美国
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/8148333
• 关键词: Anti-inflammatory; Apoptotic; Behavioral; Caliber; Caloric Restriction; Cardiac; Control Animal; Coronary; Development; Diabetes Mellitus; Diastole; Diastolic heart failure; Diet; Disease; Dobutamine; Echocardiography; Experimental Designs; Harvest; Inflammatory Response; Modality; Myocardial; Myocardial Ischemia; Rodent Model; Subgroup; Ventricular; fitness; follow-up; prevent

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 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. Neuroprotective effects of ADF against ischemic injury of the brain have also been reported. We investigated the cardioprotective effect of ADF in rats using the model of experimental myocardial infarction induced by a permanent coronary ligation. After three months of ADF or regular, daily, feeding ad libitum (AL), 5-mo old rats were subjected to coronary ligation or sham operation. A subset of rats was sacrificed 24 hours later to measure the size of myocardial infarction (MI) and the extent of apoptosis. The remainder of the animals were continued for 10 weeks on the same food regimen, during which time the progression of left ventricular (LV) remodeling was assessed by serial echocardiography. After ten weeks LV function was measured by pressure-volume loops analyses, and hearts were evaluated histologically. We showed that 24 hrs following coronary ligation the ischemic area of myocardium, i.e., the area at risk (AAR), was similar in both groups, but in ADF rats MI size, expressed as a percent of AAR, was more than 2-fold smaller, apoptosis in the AAR was reduced by more than 4-fold, and the inflammatory response was significantly reduced. At 10 wks, late LV remodeling and MI expansion occurred in AL rats but not in ADF rats, and LV pump function and arterio-ventricular coupling were superior in ADF vs AL rats. The myocyte hypertrophy in areas remote from the MI was also absent in ADF rats. The results indicate that Intermittent Food Deprivation protects the heart from ischemic injury in part, at least, via an enhanced anti-apoptotic mechanism. In another experiment, we demonstrated that ADF improves glycemic control and results in the increase of the levels of circulating adiponectin. Because recent studies have shown that adiponectin can protect the heart against ischemic injury, adiponectin may mediate, at least in part, the cardioprotective effect of ADF. 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. Contradiction of results of ADF experiments (ADF is cardioprotective but results in reduction of diastolic compliance and cardiac reserve) prompted the initiation of similar studies with direct reduction of caloric intake (CR). Similar to the experimental design described above, rats were maintained either on regular ad libitum diet, or on the diet consisting of 30% calorie reduction. After 3 mos of respective diet the MI was induced by a permanent ligation of the left descending coronary artery. MI measured histologically 24 hrs following intervention did not reveal any significant differences in MI size or apaptosis/inflammation in the area at risk. Follow-up serial echocardiographic assessment in a subgroup of rats did not reveal any differences between groups with respect to LV remodeling, function or MI expansion. Thus, contrary to ADF, CR is not cardioprotective. On the other hand, 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 for 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. Blueberry supplement. Reactive oxygen species (ROS) play a major role in ischemia-related myocardial injury. However, the 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. Blueberries have the highest antioxidant capacity among fruits and vegetables, and had been shown to reduce neurological deficits observed in aged animal models. The objective of this study was to assess the cardioprotective properties of a blueberry enriched diet (BD). Following 3-mo exposure to BD or a regular control diet (CD), the threshold for mitochondrial permeability transition (tMPT) was measured in isolated cardiomyocytes obtained from young male Fischer-344 rats. Compared to CD, BD resulted in a 24% increase (p<0.001) of ROS indexed tMPT. The remaining animals were subjected to a permanent ligation of descending coronary artery. Twenty-four hrs later, 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). In other groups of rats immediately after coronary ligation, the original diet was either continued or switched to the opposite one, and their cardiac remodeling and MI expansion were followed by serial echocardiography for 10 weeks. Results of echo measurements indicated that rates of post MI cardiac remodeling and MI expansion were proportional to original myocardial damage governed by the previous diet. However, BD or its withdrawal after MI induction attenuated or accelerated this effect. We concluded that blueberry-enriched diet protected the myocardium from ischemic damage and demonstrated the potential to attenuate the development of post MI chronic heart failure.

该计划的主要目标是对心肌缺血的啮齿动物模型进行临床前实验，以测试缺血事件前饮食控制的效果，以提高心脏组织对缺血损伤的耐受性。 I. 替代日禁食（ADF），即每隔一天才提供随意食物的喂养方案，据报道可以延长寿命并减少与年龄相关的疾病，包括癌症、糖尿病和肾病的发病率。 ADF 对大脑缺血性损伤的神经保护作用也有报道。我们使用永久冠状动脉结扎诱导的实验性心肌梗塞模型研究了 ADF 对大鼠的心脏保护作用。经过三个月的 ADF 或定期、每日、随意喂养 (AL) 后，对 5 个月大的大鼠进行冠状动脉结扎或假手术。 24小时后处死一部分大鼠以测量心肌梗塞（MI）的大小和细胞凋亡的程度。其余动物继续采用相同的饮食方案 10 周，在此期间通过连续超声心动图评估左心室 (LV) 重塑的进展。十周后，通过压力-容积环分析测量左心室功能，并对心脏进行组织学评估。我们发现，冠状动脉结扎后 24 小时，两组心肌缺血面积（即危险区域 (AAR)）相似，但在 ADF 大鼠中，MI 大小（以 AAR 的百分比表示）缩小了 2 倍多，AAR 中的细胞凋亡减少了 4 倍多，炎症反应也显着减轻。第 10 周时，AL 大鼠发生晚期左室重塑和 MI 扩张，而 ADF 大鼠则没有，且 ADF 大鼠的左室泵功能和动心室耦合优于 AL 大鼠。 ADF 大鼠中远离 MI 的区域也不存在肌细胞肥大。结果表明，间歇性食物剥夺至少部分通过增强的抗凋亡机制保护心脏免受缺血性损伤。在另一项实验中，我们证明 ADF 可以改善血糖控制并导致循环脂联素水平增加。 由于最近的研究表明脂联素可以保护心脏免受缺血性损伤，因此脂联素可能至少部分介导 ADF 的心脏保护作用。 虽然 ADF 的组织保护特性已得到证实，但慢性 ADF 对一般心血管健康的影响仍然未知。 4 个月大时，雄性 SD 大鼠开始服用 ADF 或继续随意饮食。 通过连续超声心动图对心脏形态测量和功能进行为期 6 个月的随访。观察期结束时，通过压力-容量环分析（包括联合多巴酚丁胺-容量压力测试）对大鼠进行全面的血流动力学评估，并收获心脏进行组织学评估。为期六个月的 ADF 导致心肌细胞直径减少 9% (p<0.01)，间质性心肌纤维化增加 3 倍。 ADF 中左心室大小未受影响，射血分数未降低。 ADF 中的左心房直径增加了 16%，而多普勒测量的二尖瓣血流中的 E/A 比值降低了。 ADF 中的压力-容量环分析显示舒张期心脏僵硬，组织学分析表明心肌纤维化与对照心脏相比增加了 3 倍。联合多巴酚丁胺和容量负荷显示 ADF 中左心室舒张顺应性显着降低，而收缩泵功能没有增加，表明心脏储备减少。因此，大鼠的慢性 ADF 会导致舒张功能障碍的发生，并导致心脏储备减少。 因此，ADF是一种新颖且独特的行为诱发舒张性心力衰竭的实验模型。 ADF 对大鼠的有害作用需要进一步研究 ADF 对人类心血管功能的影响。 ADF 实验结果的矛盾（ADF 具有心脏保护作用，但会导致舒张期顺应性和心脏储备减少），促使开展直接减少热量摄入 (CR) 的类似研究。与上述实验设计类似，大鼠维持常规随意饮食或减少30%热量的饮食。分别饮食 3 个月后，通过永久结扎左冠状动脉降支诱发 MI。干预后 24 小时对 MI 进行组织学测量，未发现 MI 大小或危险区域的细胞凋亡/炎症有任何显着差异。对一组大鼠进行的后续连续超声心动图评估并未显示各组之间在左心室重塑、功能或心肌梗死扩张方面存在任何差异。因此，与 ADF 相反，CR 不具有心脏保护作用。 另一方面，与随意喂养的年龄对照动物相比，24个月大的大鼠一生中保持30%热量减少，与年龄相关的心肌肥大程度较低，收缩功能较高。虽然随意喂养的 24 个月大的大鼠无法通过心率增加来应对多巴酚丁胺攻击，但 24 个月大的 CR 动物表现出年轻动物典型的适当心率反应。此外，与随意喂养的年龄匹配的对照组相比，24个月大的CR大鼠的心肌纤维化和与年龄相关的心肌细胞密度损失较少。此外，与 AL 动物相比，CR 大鼠的主动脉脉搏波速度较低，表明动脉僵硬度较低。然而，CR 并不能阻止与年龄相关的心肌细胞损失。因此，与 ADF 相反，CR 可以促进心脏健康并延缓与年龄相关的心血管结构和功能的变化。 二.蓝莓补充剂。 活性氧（ROS）在缺血相关的心肌损伤中发挥着重要作用。然而，使用合成抗氧化剂来阻止 ROS 有害影响的尝试却产生了好坏参半或负面的结果，这引发了人们对天然产物中抗氧化剂的兴趣。蓝莓在水果和蔬菜中具有最高的抗氧化能力，并且已被证明可以减少老年动物模型中观察到的神经缺陷。本研究的目的是评估富含蓝莓的饮食 (BD) 的心脏保护特性。在接触 BD 或常规对照饮食 (CD) 3 个月后，测量从年轻雄性 Fischer-344 大鼠获得的分离心肌细胞的线粒体通透性转变 (tMPT) 阈值。与 CD 相比，BD 导致 ROS 指数 tMPT 增加 24% (p<0.001)。其余动物接受冠状动脉降支的永久结扎。 24 小时后，BD 组大鼠的心肌梗塞 (MI) 比 CD 组大鼠减少 24% (p<0.05)。与 CD 大鼠相比，在 BD 风险心肌区域中观察到 TUNEL(+) 心肌细胞显着减少（2% vs 9%），炎症细胞减少 40%（p<0.05）。在冠状动脉结扎后立即进行的其他组大鼠中，继续原来的饮食或改为相反的饮食，并通过连续超声心动图跟踪它们的心脏重塑和心肌梗死扩张10周。回波测量结果表明，MI 后心脏重塑和 MI 扩张的速率与先前饮食控制的原始心肌损伤成正比。然而，BD 或 MI 诱导后的戒断减弱或加速了这种效应。我们得出的结论是，富含蓝莓的饮食可以保护心肌免受缺血性损伤，并证明有可能减轻心肌梗死后慢性心力衰竭的发展。