Endothelial function was assessed with flow-mediated dilation of the brachial artery , aerobic capacity by peak oxygen uptake ( VO ( 2peak ) ) , arterial stiffness by carotid-femoral pulse wave velocity , numbers of EPCs and OPCs by flow cytometry , circulatory angiogenic cell function by an in vitro migratory assay , and quality of life by the Kidney Disease Quality of Life-Short Form questionnaire .