Elevated muscle sympathetic nerve activity is independently associated with common carotid artery wall thickness in humans

Abstract

Aging is characterized by increased wall thickness and stiffening of the large elastic arteries (i.e., aorta and carotid arteries), although the mechanisms involved are incompletely understood. Studies in vitro demonstrate hypertrophy of vascular smooth muscle following chronic sympathetic‐adrenergic stimulation. In addition, higher measures of sympathetic nerve activity, which typically occur with advancing age, are associated with greater intima‐media thickness (IMT) of the large peripheral arteries such as the common femoral arteries. Therefore, we tested the hypothesis that the age‐related increase in large elastic artery (carotid) IMT would be independently associated with higher sympathetic nerve activity. In a cohort of 88 young and middle‐age/older adults (age: 19–73 yr, 52% men) with no history of cardiovascular disease, we performed assessments of muscle sympathetic nerve activity (MSNA, microneurography), common carotid IMT (ultrasonography), and ambulatory 24‐hr mean arterial pressure (MAP). As expected, advancing age was significantly correlated with higher MSNA burst frequency (R=0.54, P<0.001), carotid IMT (R=0.51, P<0.001), and ambulatory 24‐hr MAP (R=0.18, P=0.047). Results from multiple regression analysis that included MSNA burst frequency and traditional cardiovascular disease (CVD) risk factors that were also significantly correlated with carotid IMT (age, BMI, history of hypertension or borderline hypertension, family history of hypertension, and ambulatory 24‐hour MAP) showed that MSNA burst frequency (P=0.031), age (P=0.003), and ambulatory 24‐hour MAP (P=0.003) were independent determinants of carotid IMT (model R2=0.47, P<0.001). When expressing carotid IMT relative to lumen diameter (carotid IMT‐to‐lumen diameter ratio), multiple regression analysis showed that only MSNA burst frequency (P=0.02) was an independent determinant (model R2=0.36, P<0.001). These findings demonstrate an independent association between MSNA and carotid IMT and suggest that the age‐related increase in sympathetic‐adrenergic tone may contribute importantly to increased wall thickness of the large elastic arteries.Support or Funding InformationAHA (17POST33440101), T32 HL07121, NHLBI (P01HL014388), U54 TR001356 and AHA (13DG143400012).This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.