Older men display elevated levels of senescence-associated exercise-responsive CD28 angiogenic T cells compared with younger men.

Aging is associated with elevated cardiovascular disease risk. As a result of aging, endothelial dysfunction develops, partly due to a reduction in vascular regenerative ability. CD31 T cells (angiogenic T cells; T ) possess highly angiogenic capabilities; however, these cells are significantly reduced in older populations. In addition, older populations possess significantly higher senescent and highly differentiated T-cell levels in circulation, and these are reported to be highly exercise responsive. We investigated whether older adults display greater levels of circulating senescent (CD28 ) T cells and whether these cells were more exercise responsive than CD28 T cells. Young (18-25 years; n = 9) and older (60-75 years; n = 10) healthy men undertook a 30-min cycling bout at 70% V˙O peak, with circulating T cells (CD3 CD31 CD28 ; including CD4 and CD8 subsets) measured preexercise, postexercise, and 1 h post exercise by flow cytometry. Older adults displayed reduced basal levels of T cells (mean ± SEM: 410 ± 81 vs. 784 ± 118 cells·μL, P = 0.017), despite a greater proportion of these cells being CD28 (26.26 ± 5.08 vs. 13.36 ± 2.62%, P = 0.044). Exercise significantly increased the circulating number of T cells in both young and older men. However, in older men alone, exercise preferentially mobilized CD28 CD8 T cells compared with CD28 T cells (time × phenotype interaction: P = 0.022; Δ74 ± 29 vs. Δ27 ± 15 cells·μL, P = 0.059), with no such difference observed between these phenotypes in the young population. In conclusion, this is the first study to demonstrate that despite observing lower circulating numbers of T cells, older adults display greater levels of senescent T cells in comparison with younger individuals, and these cells are more exercise responsive than CD28 T cells. Lower number of circulating T and greater levels of senescent-associated CD28 T may contribute to greater CVD risk with advancing age.