PERIPHERAL MICROVASCULAR DISEASE IN DIABETES

In recent years a variety of techniques have been developed fbr studyi ng peripheral microvascular function in man, which have provided impor tant information regarding the functional breakdown of the microcircul ation in diabetes mellitus. In insulin dependent diabetes a sequence o f physiological changes have been described which support the so-calle d haemodynamic hypothesis: control-dependent increases in capillary pr essure result in microvascular sclerosis leading to limitation of hype raemia and loss of autoregulation. Furthermore, capillary pressure app ears to be especially raised in patients with incipient nephropathy wh o are at particular risk of microangiopathy. The limitation of maximum hyperaemia is duration related, may be observed in early childhood, a nd is correlated with the degree of basement membrane thickening. In c ontrast in normotensive non-insulin dependent patients a different arr ay of functional disturbances are described: Capillary pressure and ca pillary filtration coefficient are normal whereas maximum hyperaemia i s profoundly depressed even at diagnosis. This differential pattern of abnormalities arguably reflects the impact of a prediabetic insulin r esistant phase on the subsequent expression of microangiopathy. An und erstanding of the physiological breakdown of the microcirculation in d iabetes permits the generation of plausible candidate cellular and mol ecular mechanisms, knowledge of which will accelerate the development of protective therapy.