Department of Health and Human Physiology, University of Iowa, Iowa City, Iowa.
Abboud Cardiovascular Research Center, University of Iowa, Iowa City, Iowa.
Am J Physiol Heart Circ Physiol. 2019 Sep 1;317(3):H552-H560. doi: 10.1152/ajpheart.00275.2019. Epub 2019 Jul 5.
Aging is characterized by increased wall thickness of the central elastic arteries (i.e., aorta and carotid arteries), although the mechanisms involved are unclear. Evidence suggests that age-related increases in muscle sympathetic nerve activity (MSNA) may be a contributing factor. However, studies in humans have been lacking. Therefore, we tested the hypothesis that age-related increases in MSNA would be independently associated with carotid artery intima-media thickness (IMT) but not in young women given the reduced influence of MSNA on the vasculature in this group. In 93 young and middle-age/older (MA/O) adults (19-73 yr, 41 women), we performed assessments of MSNA (microneurography) and common carotid IMT and lumen diameter (ultrasonography). Multiple regression that included MSNA and other cardiovascular disease risk factors indicated that MSNA ( = 0.002) and 24-h systolic blood pressure (BP) ( = 0.024) were independent determinants of carotid IMT-to-lumen ratio (model R = 0.38, < 0.001). However, when examining only young women (<45 yr), no correlation was observed between MSNA and carotid IMT-to-lumen ratio ( = 0.01, = 0.963). MSNA was significantly correlated with IMT-to-lumen ratio while controlling for 24-h systolic BP among young men ( = 0.49, < 0.001) and MA/O women ( = 0.59, = 0.022). However, among MA/O men, controlling for 24-h systolic BP attenuated the association between MSNA and carotid IMT-to-lumen ratio ( = 0.50, = 0.115). Significant age differences in IMT-to-lumen ratio between young and MA/O men ( = 0.047) and young and MA/O women ( = 0.023) were removed when adjusting for MSNA (men: = 0.970; women: = 0.152). These findings demonstrate an association between higher sympathetic outflow and carotid artery wall thickness with a particular exception to young women. Increased wall thickness of the large elastic arteries serves as a graded marker for cardiovascular disease risk and progression of atherosclerosis. Findings from the present study establish an independent association between higher sympathetic outflow and carotid artery wall thickness in adults with an exception to young women and extend findings from animal models that demonstrate hypertrophy of vascular smooth muscle following chronic sympathetic-adrenergic stimulation.
衰老是中央弹性动脉（即主动脉和颈动脉）壁增厚的特征，尽管涉及的机制尚不清楚。有证据表明，与年龄相关的肌肉交感神经活动（MSNA）增加可能是一个促成因素。然而，人类的研究一直缺乏。因此，我们假设与年龄相关的 MSNA 增加将与颈动脉内膜中层厚度（IMT）独立相关，但在年轻女性中则不会，因为在该组中，MSNA 对血管的影响降低。在 93 名年轻和中老年（MA/O）成年人（19-73 岁，41 名女性）中，我们进行了 MSNA（微神经记录）和颈总动脉 IMT 和管腔直径（超声检查）的评估。包括 MSNA 和其他心血管疾病危险因素的多元回归表明，MSNA（ = 0.002）和 24 小时收缩压（BP）（ = 0.024）是颈动脉 IMT 与管腔比的独立决定因素（模型 R = 0.38，<0.001）。然而，当仅检查年轻女性（<45 岁）时，MSNA 与颈动脉 IMT 与管腔比之间没有相关性（ = 0.01， = 0.963）。在控制年轻男性（ = 0.49，<0.001）和 MA/O 女性（ = 0.59， = 0.022）中 24 小时收缩压后，MSNA 与 IMT 与管腔比显著相关。然而，在 MA/O 男性中，控制 24 小时收缩压会减弱 MSNA 与颈动脉 IMT 与管腔比之间的关联（ = 0.50， = 0.115）。当调整 MSNA 时，年轻男性和 MA/O 男性（ = 0.047）以及年轻女性和 MA/O 女性（ = 0.023）之间 IMT 与管腔比的年龄差异显著（男性： = 0.970；女性： = 0.152）。这些发现表明，较高的交感神经输出与颈动脉壁厚度之间存在关联，而年轻女性则是一个例外。大动脉弹性壁的增厚是心血管疾病风险和动脉粥样硬化进展的分级标志物。本研究的结果在年轻女性中建立了较高的交感神经输出与颈动脉壁厚度之间的独立关联，并扩展了动物模型的发现，即慢性交感神经-肾上腺素能刺激后血管平滑肌肥大。
