||We may now reflect on
what can influence vessel stiffness. Westerbacka and Yki-Jarvinen have argued that vessel
stiffness is one of the features of insulin resistance, with obese and other insulin
resistant subjects showing an increase in the reflected wave, seen as a larger
augmentation index in systole. They have also shown that this augmentation index in
healthy subjects is reduced within 30 minutes of the administration of insulin, while in
obese subjects, who have an increased augmentation index at baseline, the insulin
resistance is associated with a much slower and smaller decline of augmentation index.
They argue that the effect of insulin on large vessel stiffness is independent of its
vasodilatation effect because the time course of insulin-induced vasodilatation is much
slower than that of the fall in augmentation. It is proposed, then, that the relationship
between insulin resistance and macrovascular disease is that insulin resistant subjects
have stiffer blood vessels with an increased pulse pressure.