Elevated Muscle Sympathetic Nerve Activity Contributes to Central Artery Stiffness in Young and Middle-Age/Older Adults

Abstract

Muscle sympathetic neural activity (MSNA) influences the mechanical properties (i.e., vascular smooth muscle tone and stiffness) of peripheral arteries, but it remains controversial whether MSNA contributes to stiffness of central arteries such as the aorta and carotids. We examined whether elevated MSNA (age-related) would be independently associated with greater stiffness of central [carotid-femoral pulse wave velocity (PWV)] and peripheral (carotid-brachial PWV) arteries, in addition to lower carotid compliance coefficient (CC), in healthy men and women (n=88, age:19-73 years, 52%men). Also, we examined whether acute elevations in MSNA without increases in mean arterial pressure (MAP) using graded levels of lower body negative pressure (LBNP) would augment central and peripheral artery stiffness in young (YG, n=15, 60%men) and middle-age/older adults (MA/O, n=14, 43%men). Resting MSNA burst frequency (bursts·min −1 ) was significantly correlated with carotid-femoral PWV (R=0.44, P<0.001), carotid-brachial PWV (R=0.32, P=0.003), and carotid CC (R=0.28, P=0.01) after controlling for sex, MAP, heart rate, and waist-to-hip ratio (central obesity), but these correlations were abolished after further controlling for age (all P>0.05). In YG and MA/O adults, MSNA was elevated during LBNP (P<0.001) and produced significant increases in carotid-femoral PWV (YG:Δ+1.3±0.3 vs. MA/O:Δ+1.0±0.3 m·s −1 , P=0.53) and carotid-brachial PWV (YG: Δ+0.7±0.3 vs. MA/O: Δ+0.7±0.5 m·s −1 , P=0.92), whereas carotid CC during LBNP was significantly reduced in YG but not MA/O (YG:Δ-0.04 ±0.01 vs. MA/O:Δ0.001±0.008 mm 2 ·mmHg −1 , P<0.01). Collectively, these data demonstrate the influence of MSNA on central artery stiffness and its potential contribution to age-related increases in stiffness of both peripheral and central arteries. Our findings demonstrate the influence of MSNA on central artery stiffness and its potential contribution to age-related increases in stiffness of both peripheral and central arteries.