Cardiovascular risk factors in Type 2 diabetes: the role of hyperglycaemia

Macrovascular complications are the most important causes of morbidity, mortality and disability in people with Type 2 diabetes mellitus. Although other known risk factors for macrovascular disease (e.g, dyslipidaemia, hypertension, obesity) often co-exist, diabetes itself is an important risk factor for accelerated development of atherosclerosis. Hyperglycaemia, hyperinsulinaemia and insulin resistance may each play a major role in the onset and development of atherosclerotic disease, which causes arterial wall dysfunction, haematological disturbances and lipid abnormalities through two mechanisms: oxidative stress and nonenzymatic glycation. Hyperglycaemia induces damage to the endothelium through activation of mitogen-activated protein kinase, protein kinase C and transcription factor nuclear factor (NF)-kappa B and through increased levels of pro-adhesion proteins such as intracellular adhesion molecule (ICAM)-1. The arterial wall tone is shifted towards vasoconstriction by hyperglycaemia, which is also associated with vascular smooth muscle cell proliferation and increased intimal wall thickness. Alteration of the coagulation system towards thrombophilia is observed in Type 2 diabetes and a series of lipid abnormalities that facilitate the development of atherosclerosis is evident. In Type 2 diabetes, undiagnosed disease and unrecognized postprandial hyperglycaemia are becoming the most relevant issues in reducing the risk of vascular complications and cardiovascular mortality; improved glycaemic control may reduce the incidence of macrovascular complications.