Human skeletal muscle nitrate and nitrite in individuals with peripheral arterial disease: effect of inorganic nitrate supplementation and exercise

Skeletal muscle may act as a reservoir for N-oxides following inorganic nitrate supplementation. This idea is most intriguing in individuals with peripheral artery disease (PAD) who are unable to endogenously upregulate nitric oxide. This study analyzed plasma and skeletal muscle nitrate and nitrite concentrations along with exercise performance, prior to and following 12-weeks of exercise training combined with oral inorganic nitrate supplementation (EX+BR) or placebo (EX+PL) in participants with PAD. Non-supplemented, at baseline, there were no differences in plasma and muscle nitrate. For nitrite, muscle concentration was higher than plasma (+0.10 nmol.g−1). After 12 -weeks, acute oral nitrate increased both plasma and muscle nitrate (455.04 and 121.14 nmol.g−1, p < 0.01), which were correlated (r = 0.63, p < 0.01), plasma nitrate increase was greater than in muscle (p < 0.01). Nitrite increased in the plasma (1.01 nmol.g−1, p < 0.05) but not in the muscle (0.22 nmol.g−1) (p < 0.05 between compartments). Peak walk time (PWT) increased in both groups (PL + 257.6 s;BR + 315.0 s). Six-minute walk (6 MW) distance increased only in the (EX+BR) group (BR + 75.4 m). We report no substantial gradient of nitrate (or nitrite) from skeletal muscle to plasma, suggesting a lack of reservoir-like function in participants with PAD. Oral nitrate supplementation produced increases in skeletal muscle nitrate, but not skeletal muscle nitrite. The related changes in nitrate concentration between plasma and muscle suggests a potential for inter-compartmental nitrate “communication”. Skeletal muscle did not appear to play a role in within compartment nitrate reduction. Muscle nitrate and nitrite concentrations did not appear to contribute to exercise performance in patients with PAD

A Comparison of Capillary, Venous, and Salivary Cortisol Sampling After Intense Exercise

Venipuncture is expensive, invasive, and impractical for many sport-science and clinical-based settings. Salivary free cortisol is often cited as a noninvasive practical alternative. However, when cortisol concentrations exceed the corticosteroid-binding globulin (CBG) point of 500 nmol/L, a lack of agreement between salivary and venous blood cortisol has been found. Alternatively, capillary blood may present a minimally invasive, cost-effective, and practical surrogate for determining cortisol concentration. PURPOSE: The aim of this study was to determine whether cortisol concentrations sampled from capillary blood and saliva accurately reflect those found in venous blood across a large range of concentrations after intense exercise. METHODS: Eleven healthy aerobically trained male subjects were recruited. Capillary, salivary, and venous blood samples were collected before and after (immediately and 5, 10, 15, and 20 min after) a treadmill VO(2) max test. RESULTS: Capillary and venous concentrations increased at a similar rate after exercise (Cohen d.14-.33), increasing up to 15 min postexercise before a decline was seen. Salivary cortisol values increased at a slower rate than venous and capillary cortisol but continued to increase 15 min postexercise (Cohen d .19-.47 and .09-.72, respectively). CONCLUSIONS: Capillary cortisol accurately reflects concentrations assayed from venous blood across a range of values below and above the CBG binding point. Capillary sampling provides a minimally invasive, cost-effective, practical surrogate for assessment of hypothalamic-pituitary-gland function