Endothelial sensitivity to exercise-induced shear rate in older adults: effect of biological sex and acute folic acid consumption

Purpose: Aerobic exercise interventions improve peripheral endothelial function in healthy older males. This effect is inconsistently observed in healthy postmenopausal females, and possible mechanisms underlying this sex-related difference remain unknown. We tested the hypothesis that endothelial sensitivity to exercise-induced shear rate is reduced in healthy postmenopausal females and that it can be improved by acute folic acid consumption. Methods: Using a double-blind randomized crossover study design, 17 postmenopausal females (66 ± 8 years) and 14 males (66 ± 6 years) performed handgrip exercise at 20%, 40%, 60%, and 80% of maximal voluntary contraction after consuming a placebo or 5 mg of folic acid. Brachial artery diameter and blood velocity were measured continuously using high-resolution ultrasound and analyzed using edge-detection software. Endothelial sensitivity to shear rate was quantified as the slope of the linear regression between brachial artery dilation (% change from baseline) and shear rate. Results: During the placebo visit, endothelial sensitivity to exercise-induced shear rate did not differ between females (0.102 ± 0.055 %/s −1 ) and males (0.091 ± 0.061 %/s −1 , p=0.603). Acute folic acid consumption did not improve endothelial sensitivity to exercise-induced shear rate in females (placebo: 0.102 ± 0.055 %/s −1 , folic acid: 0.099 ± 0.062 %/s −1 , p=0.887) or males (placebo: 0.091 ± 0.061 %/s −1 , folic acid: 0.102 ± 0.083 %/s −1 , p=0.697). Conclusion: Endothelial sensitivity to exercise-induced shear rate does not differ between healthy postmenopausal females and age-matched males. Acute folic acid consumption does not improve endothelial sensitivity to exercise-induced shear rate in healthy older females or males.