Circulating angiogenic cells (CACs) are a diverse group that have been identified as predictors of cardiovascular health and are inversely proportional to cardiovascular disease (CVD) outcomes. Inactivity is a growing concern in industrialized nations and is an independent risk factor for CVD. There is limited evidence regarding the impact of reduced physical activity (rPA) on different CAC populations. The purpose of this study was to evaluate the effect of objectively monitored rPA with maintained energy balance on two CAC populations (CFU and CD34(+) cells), intracellular nitric oxide (NOi), and genes related to NO production in active, healthy men. Participants (age 25 ± 2.9 yr) refrained from structured physical activity for 10 days, which was reflected by a significant reduction in time in vigorous + very vigorous intensity activity (P = 0.03). Sedentary time tended to increase (P = 0.06) with rPA. CFU CACs have been characterized as mainly monocytic and lymphocytic cells. We found significant reductions in both the number of CFU CACs (-35.69%, P = 0.01) and CFU CAC NOi (-33.84%, P = 0.03). Neither NOi nor the number of CD34(+) cells, which are hematopoietic and endothelial progenitors, changed with rPA. We found no significant differences in NO-related gene expression or oxidative stress-related gene expression with rPA in either CAC type. Therefore, we conclude that although various CAC populations have been related to vascular health, regular physical activity is necessary to maintain CAC NOi and the vulnerability of CACs to short-term reductions in physical activity is population specific.

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Physical inactivity, a risk factor for cardiovascular disease, promotes changes in the endothelium that may be influenced by circulating angiogenic cells (CACs). CACs have the capacity to replace and repair damaged vascular endothelium. Intracellular nitric oxide (NOi) is essential for CAC migration, motility, and proliferation and is therefore a key determinant of CAC health. The objective was to determine whether CAC number and NOi levels changed in response to ten‐days of reduced physical activity (rPA). Lipid profile, weight, and blood pressure (BP) were quantified before and after rPA. rPA was confirmed with accelerometry and caloric intake was reduced to match the reduced energy expenditure during rPA. CACs (CFU‐Hill, CD34+) were isolated from PBMCs prior to and following rPA. CD34+ cells were isolated via magnetic separation and quantified with a hemocytometer. CFU‐Hill were cultured and quantified via colony‐forming assay. NOi was determined using DAF‐FM diacetate. There were no significant changes in lipid profile, weight, or BP with rPA. CFU‐Hill colonies decreased by 44.7% and CD34+ cells increased by 34.8% (p=0.095, p=0.45, respectively). CFU‐Hill NOi was significantly decreased by 52.7% (p=0.023) and CD34+ cells had reduced NOi by 24% (p=0.37). The effect of rPA on CAC NOi is specific to the CAC population.UMass, Amherst Faculty Research Grant and CHC Research Grant