Vascular disease in the metabolic syndrome: do we need to target the microcirculation to treat large vessel disease?

The metabolic syndrome of vascular risk is threatening large numbers of ever-younger people. To date, the syndrome has been chiefly viewed as a potential risk marker that confers a heightened probability of developing type 2 diabetes and occlusive atherothrombotic disease of large- and medium-sized arteries. Accumulating evidence suggests that the components of the metabolic syndrome may also adversely affect the microvasculature through several inter-related mechanisms. These include the following observations: classic risk factors for macrovascular disease such as high blood pressure and dyslipidaemia also accelerate microvascular complications of diabetes, lesser disturbances of glucose metabolism (i.e. impaired glucose tolerance) may be associated with some forms of microvascular dysfunction, non-glucose intermediary metabolites may promote renovascular hypertension thereby damaging the microvasculature, and insulin resistance appears to be directly associated with microvascular dysfunction. In turn, microvascular complications such as nephropathy and autonomic neuropathy may promote the development and progression of atherosclerosis. We argue that the vascular implications of the metabolic syndrome should be broadened to include the microvasculature. The hypothesis that vascular events can be prevented, or at least deferred, through earlier therapeutic intervention in pre-diabetic subjects with glucose intolerance is amenable to testing in clinical trials.