In defense of microvascular constriction in diabetes.

In sharp contrast to vasodilatation, vasoconstriction is not subjected to great consideration in vascular physiological and pharmacological investigations in diabetes. However, vasoconstriction is a main regulatory process in smaller vessels, in particular in the small arterioles. Here it is linked to maintenance of local blood pressure and avoids capillary hyperperfusion/hypertension. This highlights the importance of constrictor processes in the microvascular bed as opposed to larger vessels. It is manifested by a series of phenomena such as precapillary vasomotion, venoarteriolar reflex and myogenic response. Animal and human studies indeed reported defects in small vessel constrictor reactivity in diabetes but also evidence for disturbances already present in nondiabetic, insulin resistant states. This abnormality is present whether humoral, neuronal or physical stimuli are used for test. This article overviews the adequate literature and discusses both vascular and metabolic implications induced by defective vasoconstriction.