Effect of Age and Fitness on Vascular Function and Oxidative Stress During Acute Inflammation

Acute inflammation increases cardiovascular event risk, especially with increasing age. The elevated risk in older adults may be linked to changes in vascular function caused by acute inflammation. Alternatively, high cardiorespiratory fitness with aging is cardio-protective both for risk and vascular function and may therefore be protective during acute inflammation. In young adults, oxidative stress has been linked to the reductions in vascular function during acute inflammation, however the effect of acute inflammation on vascular function with aging is inconclusive. Aging increases oxidative stress thus may explain the discrepant findings on vascular function in older adults during acute inflammation. The aims of this study were 1) to determine if fitness moderates the vascular response to acute inflammation with aging and 2) to determine if oral antioxidant administration eliminates vascular dysfunction during acute inflammation. Methods: Forty-five healthy adults (15 young, 15 older unfit, 15 older fit) completed vascular function assessments at baseline and 24h after the induction of acute inflammation with the typhoid vaccine. Microvascular reactivity and brachial flow-mediated dilation (FMD) were assessed via near-infrared spectroscopy and ultrasound, respectively, following a 5-min occlusion. A subset of individuals (9 young, 16 older adults) consumed 2g of Vitamin C during acute inflammation and had vascular function reassessed. Venous blood samples were taken to measure markers of inflammation and oxidative stress. Results: Inflammation was induced as both interleukin-6 and C-reactive protein were elevated from baseline at 24h (p<0.01). FMD was reduced in all groups during acute inflammation (p<0.01), however no changes were observed in microvascular reactivity (p>0.05). Vitamin C resurrected FMD back to baseline values in both younger and older adults during acute inflammation (p<0.01) but did not impact markers of oxidative stress (p>0.05). Conclusion: Our data suggest maintaining high cardiorespiratory fitness with aging does not alter the brachial endothelial response to acute inflammation. We further demonstrate that oral Vitamin C exerts beneficial effects and restores endothelial function during acute inflammation in older adults. The changes in endothelial function in both younger and older adults is likely related to antioxidant capacity and alterations in nitric oxide bioavailability.