The Effect of Aerobic Exercise Versus Inactivity on Nitric Oxide Concentration and Synthesis in an Elderly Population

• Main Author: Burton, Samantha
• Format: Others
• Published: BYU ScholarsArchive 2015
• Subjects: microdialysis; skin vasomotor activity; cutaneous vascular conductance; Exercise Science
• Online Access: https://scholarsarchive.byu.edu/etd/6140; https://scholarsarchive.byu.edu/cgi/viewcontent.cgi?article=7140&context=etd

CONTEXT: Nitric Oxide (NO) is an endothelial-derived vasoactive molecule that causes an increase in blood flow and oxygen delivery to tissue. A reduction in NO bioavailability has been found to occur in adults over the age of 60 and can be reversed pharmacologically by improving NO synthase (NOS) activity. Reversing these age-related changes with alternative interventions, such as aerobic exercise, has shown some promising results. OBJECTIVE: To quantify blood NO-bioavailability (as measured by blood nitrite levels) in a population of aerobically trained elderly men and compare these data to a group of age-matched, inactive individuals. In addition, we measured the cutaneous vasodilator response to local skin heating as a bioassay for NO-mediated cutaneous dilation. SETTING: BYU Human Performance Research Center (HPRC). PARTICIPANTS: 16 healthy elderly men (age = 66 ± 7.07 years) were divided into two groups based on physical fitness levels and estimated VO2max in ml O2•kg-1•min-1 (Trained = 39.1 ± 1.21, Untrained = 29.0 ± 2.70). INTERVENTIONS: A blood sample was collected and analyzed for NO. A microdialysis study was performed and dialysate was collected at 32°C and at 42°C. During the heating process, skin blood flow (skin vasomotor activity) was monitored and reported as cutaneous vascular conductance (CVC). MAIN OUTCOME MEASURES: Whole blood nitrite concentrations, pre- and post-heat nitrite concentrations, and CVCmax were compared between trained and untrained groups. RESULTS: Whole blood nitrite concentration was similar in trained subjects and untrained subjects averaging 25.77 ± 6.75 and 21.43 ± 7.20 µM, respectively (F1,13 = 0.19; P = 0.6671]. Local skin heating had no impact on the concentration of nitrite in dialysate samples ([NOx]dialysate F1,26 = 0.01; P = 0.7567). In addition, the plateau in % CVCmax following 30 minutes of local heating was similar for trained and untrained subjects averaging 67.7 ± 5.8 and 68.0 ± 6.2 % CVCmax, respectively (F1,13 = 0.00; P = 0.9673). CONCLUSIONS: The results of this study indicate that age-mediated reductions in whole blood NO-bioavailability and decrements in NO-mediated cutaneous vasodilation during local heating were similar in aerobically fit and sedentary adults 60 years old or older. We conclude that a commitment to aerobic fitness was unable to overcome the age-related dysfunction of the NOS system.