Furthermore, comparability of groups within a cross-sectional aging study requires control of multiple vascular risk factors, that depend on aging and the aging-immanent metabolic syndrome and may generally affect structural or functional endpoints of clinical vascular studies, such as capillarisation, arterial stiffness or endothelial function in in response to arterial-occlusion, insulin or exercise stimuli [25, 28, 35, 37, 39, 41, 42, 48, 53]. This evidence concerns the gene INS and metabolic syndrome.