Are improvements in arterial stiffness associated with moderate physical activity and modulated by nitric oxide by-products in overweight adults?

Abstract

Arterial stiffness, measured via pulse wave velocity (PWV) has been shown to be a strong independent predictor of cardiovascular morbidity and all-cause mortality (1) . Healthy compliant brachial arteries normally have a PWV of 7-9 ms -1 , whereas stiffer arteries tend to be in the range of 12-15 ms -1(2,3) . It has been hypothesised that regular physical activity improves endothelial function due to vascular shear stress causing an increased production of the vasodilator nitric oxide (NO) (4) . We previously reported that six months of brisk walking was associated with a decrease in PWV (5) . Here we investigated whether the observed beneficial changes in PWV following regular brisk walking were associated with changes in serum nitrate and nitrite (NO x ) (a surrogate marker for the vasodilator NO) concentrations.77 overweight sedentary individuals (19 males, 58 females; mean age 45.6 (SD 6.55) years; BMI 29.18 (SD 4.27) kg/m 2 ) participated in a randomised control trial and were allocated to one of three groups: control group (n25), walking with monthly telephone contact group (n25) and walking with weekly telephone contact group (n27). The walking groups were asked to incorporate 3 · 10 minute bouts of brisk walking into their daily routine on 5days/week and were contacted over six months on to provide support. The control group were given light stretching exercises to carry-out on 5days/week and were contacted on a monthly basis to control for attention effects. Percentage body fat (Tanita scales), BMI (kg/m 2 ), and PWV were measured at baseline and repeated after six months with follow-up measurements taken four months later. PWV was measured using a sensor based device as described by McLaughlin et al. (2) . For the purposes of the present investigation, both walking groups were combined (n52) and telephone contact was included as a covariate. Time by group interactions were analysed using repeated measures two-way analysis of covariance (ANCOVA). Between subject differences were analysed using a one-way ANOVA with posteriori Tukey Honestly Significant Difference (HSD) test.There was a significant decrease in PWV (P < 0.001) coupled with significant increases in NO x (P < 0.001) over the 6 month intervention, in the walking group as compared to control, and these beneficial effects were sustained beyond the end of the intervention period (i.e. at 4 months follow-up) (Figure 1 and 2). Furthermore a strong negative correlation between PWV and NO x was also observed (r = -0.65, P < 0.001).The results demonstrate that the beneficial changes in PWV observed with regular brisk walking for 3 · 10 minutes per day may be explained by concurrent increases in nitric oxide by-products in these overweight individuals.