Plasma nitrate/nitrite levels are unchanged after long-term aerobic exercise training in older adults

Abstract

Reduced nitric oxide (NO) production and bioactivity is a major contributor to endothelial dysfunction. Animal data suggests that improvements in endothelial function in response to aerobic exercise training may depend on the duration of the training program. However, no studies have examined changes in NO (as assessed by the major NO metabolites, nitrate and nitrite, NOx) after long-term training in humans. In addition, aging may impair the ability of the vasculature to increase NO with exercise. Thus, we determined whether 24 weeks of aerobic exercise training increases plasma NOx levels in sedentary older adults. We also examined changes in forearm blood flow (FBF) at rest and during reactive hyperemia as a measure of vasomotor function. Plasma NOx levels were measured in 82 men and women using a modified Griess assay. FBF was assessed in a subset of individuals (n=15) using venous occlusion plethysmography. After 24 weeks of exercise training, there were significant improvements in maximum oxygen consumption, HDL cholesterol, triglycerides, and body fat. Changes in plasma NOx levels ranged from −14.83 to +16.69 μmol/L; however, the mean change overall was not significant (−0.33±6.30 μmol/L, p=0.64). Changes in plasma NOx levels were not associated with age, gender, race, HDL cholesterol, triglycerides, body weight, body fat, or maximal oxygen consumption. There were also no significant changes in basal FBF, peak FBF, hyperemic response, total hyperemic flow, or minimum forearm vascular resistance with exercise training. In conclusion, improvements in plasma NOx levels and FBF are not evident after long-term training in older adults.

l-Arginine supplementation improves antioxidant defenses through l-arginine/nitric oxide pathways in exercised rats

“…It has been long recognized that supplementation of L-Arg, the endogenous physiological precursor of NO, improves endothelial vasodilator function of coronary and peripheral arteries (23). More recently, L-Arg supplementation was also shown to reduce moderate-intensity exercise-induced oxidative stress and enhance high-intensity exercise tolerance (1,5). In this study, we investigated whether L-Arg supplementation attenuates endurance training and an exhaustive exercise-induced oxidative stress using rat models.…”

Nitro-Oxidative Stress Biomarkers in Active and Inactive Men

“…However, the responses to longer-term training ( ≥ 16 wk) seem to be more variable. In a group of older men and women, 24 wk of exercise training did not improve plasma NOx levels [ 1 ] . Given the extremely long duration of training in the present study, the lack of association between activity level and plasma NOx levels may be less surprising.…”

“…However, our plasma NOx measurement is an assessment of NO bioavailability as opposed to a measurement of endothelial function. Although reduced NO bioavailability is one mechanism thought to cause endothelial dysfunction [ 1 ] , impairments in endothelial function can occur without decreases in NOx levels. For example, an earlier study found that atherosclerotic rabbits had higher plasma NO levels, as determined by quantifying nitrosyl compounds in blood, but impaired endothelium-dependent vasodilation, compared to control rabbits [ 25 ] .…”

Ageing, exercise and cardiovascular health: good and bad news

“…The good news is that these changes are not observed in lifelong physically active men. However, 24 weeks of aerobic training, increasing by 15%, failed to significantly increase venous NO metabolites and forearm flow mediated vasodilatation in older men and women (Brinkley et al 2009). Despite leg training, in the study of Brinkley et al (2009), forearm flow mediated vasodilatation should have been improved (Green et al 2004).…”

“…However, 24 weeks of aerobic training, increasing by 15%, failed to significantly increase venous NO metabolites and forearm flow mediated vasodilatation in older men and women (Brinkley et al 2009). Despite leg training, in the study of Brinkley et al (2009), forearm flow mediated vasodilatation should have been improved (Green et al 2004). In fact, Hambrecht et al (1998) found increased acetylcholine‐induced blood flow in the femoral artery after 24 weeks of aerobic training in chronic heart failure patients (mean age = 56 years).…”