Electrocardiograms of mice selectively bred for high levels of voluntary exercise: Effects of short-term exercise training and the mini-muscle phenotype
Electrocardiograms of mice selectively bred for high levels of voluntary exercise: Effects of short-term exercise training and the mini-muscle phenotype
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DOI：
10.1016/j.physbeh.2018.11.041
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发表时间：
2019-02-01
影响因子：
2.9
通讯作者：
Garland, Theodore, Jr.
中科院分区：
文献类型：
--
作者：
Kay, Jarren C.;Claghorn, Gerald C.;Garland, Theodore, Jr.
运动训练引起的心脏功能变化已经被详细研究过，但对那些伴随着体力活动持续时间或强度的逐渐增加而来的变化却知之甚少。为了解决这一差距，我们研究了来自人工选择实验的小鼠的心电图(ECG)，在该实验中，四个重复系被培育用于高自愿车轮跑(HR)，而四个未被选择的系作为对照(C)。使用ECGenie(Mouse Speciics，Inc.)记录ECG。在六天轮子进入之前和之后(如标准协议中用于选择繁殖者)。我们假设，HR小鼠将在心电图特征上显示出先天的差异，并且HR小鼠相对于C小鼠对训练的反应将更大，因为前者跑得更多。在轮子接触后，在控制体重变化的统计分析中，所有小鼠的心率都较低，而HR系小鼠的PR间期比C系小鼠长。同样在轮子接触后，雄性小鼠的心率变异性增加，而雌性小鼠的心率变异性降低。以身体质量为协变量，6天的车轮接触显著增加了FIR和C男性的脑室质量。在HR系中，被称为迷你肌肉个体的一组小鼠的后肢肌肉质量和通常更大的内部器官(包括心脏和脑室)减少了50%。与肌肉正常的个体相比，肌肉发达的个体在接触车轮之前和之后都有更长的QRS波。对其他种类哺乳动物的一些研究表明，运动成绩和QRS持续时间之间存在相关性。在HR选择实验的8个单独品系或从文献中获得的17个近交系小鼠之间，车轮运行与心率或QRS持续时间(车轮运行前)之间的相关性没有统计学意义。而雄株系的总转数和平均速度与PR持续时间呈负相关，17个雌性自交系的奔跑持续时间与PR持续时间呈负相关。我们的结论是，与C小鼠相比，HR小鼠增强了心脏功能的可训练性(如轮子接触后它们较长的PR持续时间所表明的)，并且迷你肌肉表型引起的心脏变化与先前对哺乳动物的研究中提高的运动能力有关。
Changes in cardiac function that occur with exercise training have been studied in detail, but those accompanying evolved increases in the duration or intensity of physical activity are poorly understood. To address this gap, we studied electrocardiograms (ECGs) of mice from an artificial selection experiment in which four replicate lines are bred for high voluntary wheel running (HR) while four non-selected lines are maintained as controls (C). ECGs were recorded using an ECGenie (Mouse Specifics, Inc.) both before and after six days of wheel access (as used in the standard protocol to select breeders). We hypothesized that HR mice would show innate differences in ECG characteristics and that the response to training would be greater in HR mice relative to C mice because the former run more. After wheel access, in statistical analyses controlling for variation in body mass, all mice had lower heart rates, and mice from HR lines had longer PR intervals than C lines. Also after wheel access, male mice had increased heart rate variability, whereas females had decreased heart rate variability. With body mass as a covariate, six days of wheel access significantly increased ventricle mass in both FIR and C males. Within the HR lines, a subset of mice known as mini-muscle individuals have a 50% reduction in hindlimb muscle mass and generally larger internal organs, including the heart ventricles. As compared with normal-muscled individuals, mini-muscle individuals had a longer QRS complex, both before and after wheel access. Some studies in other species of mammals have shown correlations between athletic performance and QRS duration. Correlations between wheel running and either heart rate or QRS duration (before wheel running) among the eight individual lines of the HR selection experiment or among 17 inbred mouse strains taken from the literature were not statistically significant. However, total revolutions and average speed were negatively correlated with PR duration among lines of the HR selection experiment for males, and duration of running was negatively correlated with PR duration among 17 inbred strains for females. We conclude that HR mice have enhanced trainability of cardiac function as compared with C mice (as indicated by their longer PR duration after wheel access), and that the mini-muscle phenotype causes cardiac changes that have been associated with increased athletic performance in previous studies of mammals.