Microcirculation in Aging Skeletal Muscle

描述（由申请人提供）：身体机能随着年龄的增长而下降，促进久坐不动的生活方式，增加肥胖、高血压和糖尿病的风险。骨骼肌维持活动的能力需要氧气输送和代谢物清除。我们推测，衰老通过对潜在的信号通路产生不利影响而损害了微循环向活跃的骨骼肌纤维供应血流的能力。我们已经开发了小鼠的臀大肌（运动所必需的髋伸肌）作为模型，以研究衰老如何影响小动脉网络中骨骼肌血流的控制。响应于收缩活动的血流量的快速增加通过输送氧气和清除代谢物来促进运动耐量，就像在运动期间和恢复期间维持充血一样。随着年龄的增长，小动脉扩张和灌注的时间进程和幅度严重减弱，但这些对肌肉功能的不良影响的机制尚不清楚。本研究的目的1是确定细胞间通讯如何受到衰老的影响。我们将选择性地阻断沿着小动脉内皮和平滑肌的信号传导，记录体内相应细胞的电活动，并通过免疫标记和实时PCR确定连接蛋白（间隙功能）的表达，以揭示这些机制。尽管平滑肌和内皮中的钾（K+）通道对于血管舒张是不可或缺的，但衰老对小动脉中的K+通道的影响尚不清楚。目的2是确定衰老如何影响K+通道的功能表达，这些通道使用膜片钳记录（和先前的技术）从新鲜分离的小动脉平滑肌和内皮细胞中控制血管舒张。交感神经活动（SNA）随着年龄的增长而增加，并且可以限制血液流向活跃的骨骼肌，特别是在男性中。目标3将确定衰老如何影响SNA和肌纤维收缩在控制小动脉直径方面的相互作用，并将根据性别差异进行研究。我们的长期目标是确定肌纤维收缩和小动脉扩张之间相互作用的关键信号通路如何受到衰老的影响。这些研究的结果将为制定改善肌肉血流量减少的策略提供新的机制见解，从而通过促进参与体力活动的能力和降低心血管风险来提高生活质量。

DESCRIPTION (provided by applicant): Physical performance declines with aging, promoting a sedentary lifestyle and increasing the risk of obesity, hypertension and diabetes. The capacity of skeletal muscle to sustain activity requires oxygen delivery and metabolite removal. We hypothesize that aging impairs the ability of the microcirculation to supply blood flow to active skeletal muscle fibers by adversely affecting underlying signaling pathways. We have developed the gluteus maximus muscle (a hip extensor essential to locomotion) of the mouse as a model to study how aging affects the control of skeletal muscle blood flow in arteriolar networks. A rapid increase in blood flow in response to contractile activity promotes exercise tolerance by delivering oxygen and removing metabolites, as does the maintenance of hyperemia during exercise and into recovery. With aging, the time course and magnitude of arteriolar dilation and perfusion are severely blunted however the mechanisms underlying these adverse effects on muscle function are unknown. Aim 1 of this research is to determine how cell-to-cell communication is affected by aging. We will selectively disrupt signaling along arteriolar endothelium and smooth muscle, record the electrical activity of respective cells in vivo, and determine connexin (gap unction) expression with immunolabeling and Real-Time PCR to reveal these mechanisms. Whereas potassium (K+) channels in both smooth muscle and endothelium are integral to vasodilation, the effect of aging on K+ channels in arterioles is unknown. Aim 2 is to determine how aging effects the functional expression of K+ channels that govern vasodilation using patch clamp recording (and preceding techniques) from freshly-dissociated arteriolar smooth muscle and endothelial cells. Sympathetic nerve activity (SNA) increases with aging and can restrict blood flow to active skeletal muscle, particularly in males. Aim 3 will determine how aging affects the interaction between SNA and muscle fiber contraction in controlling arteriolar diameter and will do so in light of gender differences. Our long term goal is to define how key signaling pathways that underlie the interaction between muscle fiber contraction and arteriolar dilation are affected by aging. Findings from these studies will provide new and mechanistic insight for developing strategies to ameliorate decrements in muscle blood flow and thereby enhance the quality of life through promoting the ability to engage in physical activity and reduce cardiovascular risks.