Possibility of energy restriction as a means of preventing sudden death among the elder

在各种哺乳动物中，没有营养不良的能量限制（ER）可以延缓衰老过程并延长寿命。我们研究了ER对使用秋田饮食的C57 B1/6雄性小鼠心脏的形态和生理特性的影响。我们使用包括588个基因的cDNA阵列膜分析了ER（200 kJ/周）或对照（400 kJ/周）B6 11月龄雄性小鼠心脏mRNA的表达。雌激素受体增加的mRNA为胎儿肌球蛋白碱性轻链基因和热休克基因转录因子1（HSF 1）。电镜观察发现ER心肌内脂滴很少，而对照组心肌内脂滴较多。与对照组相比，ER小鼠的心脏没有肥大。对老年小鼠的体温和心电图进行动态长期记录，发现ER小鼠的心率变化先于体温变化，体温降低时心率急剧下降至原来的1/5。当体温上下变化时，ER小鼠未出现室性早搏等危险性心律失常。这些结果表明ER小鼠心脏对低温有良好的适应性。结果表明，ER心脏在改变体温方面具有重要作用，ER可能改变心脏的结构和功能特性，使其适应更宽的体温和能量利用范围。这也表明ER可能作为预防老年人致命性心律失常和猝死的一种手段。

Energy restriction (ER) without malnutrition has been known to retard aging processes and extend the life span in various species of mammals. We investigated the effects of ER on morphological and physiological properties of the heart of C57B1/6 male mice using AKITA diet. We analyzed the expression of heart mRNA from ER (200 kJ/week) or control (400 kJ/week) B6 11-month-old male mice using cDNA array membranes including 588 genes. mRNAs increased by ER were fetal myosin alkali light chain genes and transcriptional factor 1 for heat shock gene (HSF1). Electron microscopy revealed that ER cardiac muscle had very few lipid droplets, which were often found in control one. Heart of ER mice was not hypertrophic compared to control. Ambulatory long-term recording of body temperature and electrocardiogram of aged mice revealed that the heart rate of ER mice changed before body temperature did, and the rate was dramatically decreased to one fifth when body temperature was decreased. When body temperature changed up and down dangerous arrhythmia, such as ventricular premature beat, was not found in ER mice. These findings mean that the heart of ER mice has good adaptation to hypothermia. Moreover, it is suggested that the ER heart has an important role in changing body temperature.In conclusion, ER may alter structure and functional properties of the heart and make it adaptable to wide range of body temperature and energy availability. This also suggests possibility of ER as a means of preventing lethal arrhythmia, and also sudden deaths, among the elder.