Behavioral, dietary and pharmacological modalities of cardioprotection

该计划的主要目标是在心肌缺血的啮齿动物模型上进行临床前实验，以测试在缺血事件发生前饮食操作的效果，以增加心脏组织对缺血损伤的耐受性。 一、间歇性禁食(IF)，即每隔一天才能获得即兴食物的进食方法，据报告可延长寿命并减少与年龄有关的疾病的发病率，包括癌症、糖尿病和肾脏疾病。IF对脑缺血损伤的神经保护作用也有报道。采用冠状动脉结扎致大鼠实验性心肌梗死模型，观察IF对大鼠心肌的保护作用。5个月龄大鼠自由喂养(AF)3个月后，行冠状动脉结扎或假手术。24小时后处死一部分大鼠，测量心肌梗死(MI)面积和细胞凋亡程度。其余的动物在相同的饮食方案下持续10周，在此期间，通过系列超声心动图评估左心室(LV)重构的进展。10周后，通过压力-容量环分析测定左心功能，并对心脏进行组织学评价。我们发现，冠脉结扎后24小时，两组大鼠心肌缺血面积，即危险面积(AAR)相似，但IF组大鼠心肌梗死面积(占AAR的百分比)缩小2倍以上，AAR中的细胞凋亡减少4倍以上，炎症反应显著减轻。在10周时，房颤大鼠出现晚期左室重构和心肌梗死扩大，而IF大鼠则无此现象，且IF大鼠的室泵功能和室室偶联作用优于房颤大鼠。IF大鼠心肌梗死远端心肌细胞肥大也不明显。结果表明，间歇性食物剥夺至少在一定程度上通过增强抗细胞凋亡机制来保护心脏免受缺血损伤。在最后的实验中，我们证明了IF改善了血糖控制，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损伤，脂联素可能至少部分地介导了IF的心脏保护作用。 二、蓝莓补充剂。活性氧自由基(ROS)在缺血性心肌损伤中起重要作用。然而，试图使用合成抗氧化剂来阻断ROS的有害影响，已经产生了混合或负面的结果，促使人们对天然产品中发现的抗氧化剂感兴趣。蓝莓在水果和蔬菜中具有最高的抗氧化能力，并已被证明可以减少在老年动物模型中观察到的神经缺陷。本研究的目的是评估蓝莓强化饮食(BD)的心脏保护特性。在BD或正常对照饲料(CD)暴露3个月后，测定青年雄性Fischer-344大鼠分离的心肌细胞线粒体通透性转换(TMPT)阈值。与CD相比，BD导致ROS指数的TMPT增加了24%(p&lt；0.001)。其余的动物接受冠状动脉降支的永久性结扎。24小时后，BD大鼠的心肌梗死(MI)比CD大鼠减少24%(p&lt；0.05)。与CD大鼠相比，患BD的心肌区TUNEL(+)心肌细胞明显减少(2%比9%)，炎症细胞减少40%(p&lt；0.05)。其他组大鼠在冠脉结扎后立即继续或改用原来的饮食，并对其心脏重构和心肌梗死扩大进行连续10周的超声心动图观察。超声心动图测量结果显示，心肌梗死后心脏重构和心肌梗死扩张率与既往饮食所导致的原始心肌损害成正比。然而，BD或MI诱导后停药可减弱或加速这一效应。我们的结论是，富含蓝莓的饮食可以保护心肌免受缺血损伤，并显示出减缓心肌梗死后慢性心力衰竭发展的潜力。

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. Intermittent Fasting (IF), i.e., the feeding regimen when ad lib food is available only every other day, had been reported to increase the life span and to reduces the incidence of age-associated diseases including cancer, diabetes and kidney disease. Neuroprotective effects of IF against ischemic injury of the brain have also been reported. We investigated the cardioprotective effect of IF in rats using the model of experimental myocardial infarction induced by a permanent coronary ligation. After three months of IF or regular, daily, feeding ad libitum (AF), 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 IF 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 AF rats but not in IF rats, and LV pump function and arterio-ventricular coupling were superior in IF vs AF rats. The myocyte hypertrophy in areas remote from the MI was also absent in IF 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 the last experiments we demonstrated that IF 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 IF. 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. 24 hrs later resulting myocardial infarction (MI) in rats on BD was 24% less than in CD rats (p<0.05). Significantly less TUNEL(+) cardiomyocytes (2% vs 9%) and 40% less 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.