Ageing is a major risk factor for cardiovascular disease and is thought to convey this risk in part by impairing endothelial function (Lakatta, 2002). The purpose of this study was to investigate the hypothesis that ageing alters resting endothelial behaviour and endothelial responses to acute exercise.
With institutional ethical approval, 14 young (mean ± S.E.M., 22 ± 1 yrs) and 13 aged (57 ± 3 yrs) healthy male non-smokers were recruited by local advertisement. Subjects attended the laboratory between 0900 hrs and 1300 hrs, having abstained from caffeine and intense exercise for 12 hours. Forearm reactive hyperaemia following a 3 min period of arterial occlusion was measured using venous occlusion plethysmography. Resting venous blood samples were taken for quantification of circulating endothelial cells (CEC) and for the analysis of plasma thrombomodulin (TM) and von Willebrand factor (vWF). Full blood cell counts were also carried out. Following a medical examination, subjects performed a bout of cycle exercise, in the form of an incremental fitness test to volitional exhaustion. A post-exercise blood sample was taken and blood cell counts were repeated. Inter-group results were compared using unpaired Student’s t tests and Mann-Whitney non-parametric tests. Intra-group comparisons were carried out using paired Student’s t tests and Wilcoxon non-parametric tests where appropriate. P < 0.05 was considered to be statistically significant.
Resting blood flow was not significantly different between the young and aged groups. Reactive hyperaemia however was significantly greater in young than in aged subjects (percentage increases 457.8 ± 69.9 cf. 177.1 ± 38.4% P < 0.01). Resting CEC numbers were similar between young and aged subjects (112.5 ± 52.0 cf. 100.5 ± 12.0 cells ml-1) and were not altered by acute exercise in either group (post-exercise 106.4 ± 34.2 cf. 107.4 ± 21.0 cells ml-1). Resting plasma vWF was significantly higher in aged than in young subjects (115.4 ± 9.1 cf. 194.8 ± 27.0 vWF units; P < 0.05) and rose significantly during exercise in the young group (115.4 ± 9.1 cf. 204.8 ± 26.7 vWF units; P < 0.01) but not in the aged group. Plasma TM was not significantly different between groups at rest and rose significantly during exercise in the young group (3.7 ± 0.5 cf. 4.1 ± 0.3 ng ml-1; P < 0.05) but not in the aged group. Exercise-induced leucocytosis was observed in the young (pre 6.4 ± 0.6 cf. post 9.8 ± 0.9 X 109.L-1; P < 0.01) but not in the aged subjects (pre 5.8 ± 0.4 cf. post 6.8 ± 0.5 X 109.L-1).
These results indicate that aging is associated with impaired reactive hyperaemia. This is accompanied by resting haemostatic changes and by a marked attenuation of several endothelium-derived responses to exercise.
This work was supported by Enterprise Ireland.