Decline of popliteal artery flow-mediated dilation with aging and possible involvement of asymmetric dimethylarginine in healthy men

PURPOSE: We examined the influences of age and gender on flow-mediated endothelial function and the involvement of the competitive inhibition of L-arginine in endothelial function. METHODS: We measured brachial and popliteal flow-mediated vasodilation (FMD) responses, nitrate/nitrite (NOx) concentrations, and plasma levels of asymmetric dimethylarginine (ADMA) in four healthy, nonsmoking groups: young men (mean 26 ± 2 years, n = 17), middle-aged men (mean 50 ± 3 years, n = 19), young women (mean 27 ± 2 years, n = 16), and middle-aged women (mean 51 ± 2 years, n = 18). RESULTS: In young men, we found no significant differences between brachial and popliteal artery FMDs (10.6 ± 1.5 vs 8.7 ± 1.6%, p = 0.06). However, the popliteal artery FMD was significantly lower than the brachial artery FMD in middle-aged men (11.4 ± 1.5 vs 6.4 ± 1.0%, p < 0.001). In women, we found no significant differences between brachial and popliteal artery FMDs in young and middle-aged individuals (young, p = 0.17; middle-aged, p = 0.08). Popliteal artery FMD correlated with plasma NOx and ADMA levels as well as with the NOx/ADMA ratio in men but not in women (r = 0.485, - 0.544, and 0.672, respectively). CONCLUSION: We concluded that a decrease in flow-mediated endothelial function in arteries of the lower extremities was evident in healthy middle-aged men, but not in middle-aged women. The competitive inhibition of L-arginine may contribute to this decrease in men.