Aortic Stiffness is Negatively Associated with Microvascular Glycocalyx Thickness and Microvascular Perfusion among Older Adults: Role of Carotid Pressure Pulsatility

Abstract

Introduction The glycocalyx layer is essential to the maintenance of a healthy microvascular endothelium and diminishes with advancing age. Similarly, the aorta stiffens with aging and increases the risk of cardiovascular disease and target organ damage, possibly through pressure pulsatility‐associated microvascular damage. However, whether aortic stiffness and/or pressure pulsatility are associated with microvascular endothelial glycocalyx structure/function among older adults is unknown. Therefore, the objective of this analysis was to investigate the potential relation between aortic stiffness and pressure pulsatility with glycocalyx thickness and microvascular perfusion in older adults. We hypothesized that increased aortic stiffness and pressure pulsatility would be associated with less glycocalyx thickness and microvascular perfusion in older adults. Methods Sublingual microvessels were assessed using intravital microscopy in older adults (n=24; age 61 ± 6y, 46% women). Perfused boundary region (PBR) and red blood cell (RBC) filling %, indirect indices of glycocalyx thickness (larger PBR=smaller thickness) and microvascular perfusion respectively, were determined in vessels between 5‐25 µm RBC column width. Aortic stiffness was quantified by carotid‐femoral pulse wave velocity (cfPWV) and carotid pressure pulsatility as carotid pulse pressure (PP)/mean arterial pressure (MAP). Results Adjusting for age, sex and MAP, cfPWV was associated with larger PBR 5‐25 (β: 0.08; p=0.001) and lower RBC filling % (β: ‐0.02, p=0.002). Higher carotid pressure pulsatility was associated with lower RBC filling % (β: ‐0.12; p=0.03), but this relation was attenuated after adjusting for sex (p=0.11). Upon stratification by sex, higher carotid pressure pulsatility was associated with larger PBR 5‐25 (r=0.66, P=0.03) and lower RBC filling % (r=‐0.73, P=0.01) in women, but not men (P=0.94 and P=0.77 respectively). Conclusion Higher aortic stiffness was negatively associated with microvascular glycocalyx thickness and microvascular perfusion among older adults. Additionally, carotid pressure pulsatility was negatively associated with glycocalyx thickness and microvascular perfusion in women only. The mechanisms that contribute to sex differences in the relation between pressure pulsatility and glycocalyx structure/function in older adults require further study.