Preserved Endothelium-independent Function With Aging: Evidence From The Peripheral And Cerebral Vasculature

Abstract

There is growing evidence that vascular endothelial dysfunction is not only antecedent to cardiovascular disease, but also cognitive dysfunction and Alzheimer’s disease. Vascular smooth muscle cells (VSMCs) translate the endothelial-derived signal to vasodilate into action. PURPOSE: However, in the peripheral, and especially the cerebral, vasculature, the impact of aging on the functional capacity of VSMCs, and any functional link between these vascular beds, is not well understood. METHODS: Therefore, endothelium-independent dilation, elicited by sublingual nitroglycerin (NTG, 2 tabs, 0.4 mg Nitrostat each), compared to sham-delivery (control), was assessed using Doppler ultrasound in both the popliteal and middle cerebral (MCA) arteries of 12 young (22 ± 4 yrs, 6 male/6 female) and 11 old (67 ± 3 yrs, 6 male/5 female) healthy adults. RESULTS: In the popliteal artery, when compared to control (∆ young: 0.00 ± 0.03 mm, ∆ old: 0.02 ± 0.05 mm), NTG resulted in significant increases in vessel diameter (∆ young: 0.32 ± 0.13 mm, ∆ old: 0.37 ± 0.13 mm) with no differences between age or sex. Similarly, in the MCA, when compared to control (∆ young: 0.07 ± 0.11 mm, ∆ old: 0.02 ± 0.20 mm), NTG resulted in significant increases in vessel diameter (∆ young: 1.01 ± 0.30 mm, ∆ old: 1.00 ± 0.38 mm) with no differences between age or sex. Interestingly, there was no evidence of a relationship between the peripheral and cerebral vascular responses to NTG in terms of either age, sex, or all subjects as a whole. CONCLUSION: Thus, the known age-related vascular dysfunction, in the peripheral and cerebral circulations, does not appear to be the consequence of dysfunctional VSMCs, and there is no evidence of a link between VSMC function in these two vascular beds.