Blood Vessel Health: The Influence of Ageing and Aerobic Fitness

Abstract

Optimal blood vessel function requires a balance between sympathetic neural vasoconstrictor activity (SNA) and endothelial-derived vasodilatory nitric oxide (NO) bioavailability. Ageing is associated with elevated resting SNA and reduced NO production. Aerobically-trained older adults (OT) have higher SNA compared with their untrained age-matched peers (OU). An explanation for higher SNA is unclear but may serve to ‘buffer’ a corresponding increase in NO production. PURPOSE. To test the hypothesis that OT will: 1) have higher resting SNA than aerobic fitness-matched young adults (YA) and OU, 2) have similar endothelial-mediated NO production to YA, but greater than OU, and 3) observe a positive relationship between resting SNA and popliteal artery (PA) flow-mediated dilation (FMD). METHODS. Resting common fibular nerve muscle SNA (MSNA, microneurography) and PA endothelial-dependent FMD were determined in 8 YA (23±2yrs, VO2peak 49.2±9.4mLO2/kg/min), 8 OU (63±6yrs, VO2peak 28.1±5.2mLO2/kg/min), and 8 OT (65±3years, VO2peak 49.4±3.2mL O2/kg/min). RESULTS. MSNA was higher in OT than YA (71±20 vs. 29±19 bursts/100heartbeats; p=0.006) but not OU (43±32 bursts/100heartbeats; p=0.1). FMD was higher in both YA and OT (9.5±1.5% and 12.1±2.4%, respectively) than OU (6.7±1.1%, all, p<0.02). In OT, the correlation between MSNA and FMD was significant (r=0.89, p=0.003). CONCLUSIONS. This study marks the first attempt to concurrently measure MSNA and FMD in older adults. Our data suggests that exaggerated resting MSNA levels in OT adults may be a compensatory mechanism to ‘buffer’ a corresponding increase in NO production to maintain vascular tone and arterial pressure.