Asymptomatic hyperglycaemia and early atherosclerotic changes.

Ultrasonographic scanning of carotid arteries allows non-invasive detection of atherosclerotic changes. This technique has been used to investigate changes in the thickness of the intimal plus medial (IM) complex, in patients with type 2 diabetes, type 1 diabetes and those in the pre-diabetic state of impaired glucose tolerance (IGT). IM thickness (IMT) increases with age, but this process was found to be considerably accelerated in patients with type 2 diabetes. In addition, IMT was significantly greater in patients with cerebral lacunar infarctions, and in those with detectable coronary artery stenosis. A study in patients with type 1 diabetes found that IMT correlates with duration of diabetes as well as age. The correlation with duration of diabetes suggests that hyperglycaemia contributes to the progression of atherosclerosis. IMT was also found to be increased in individuals with hyperinsulinaemic IGT, compared with control individuals with normal glucose tolerance. These results suggest that even relatively small increases in postprandial blood glucose levels can lead to increases in IMT and, hence, increased risk of cardiovascular disease. Further analysis revealed a correlation between hyperinsulinaemia (i.e. insulin resistance) and increased IMT. These results provide a clear rationale for the therapeutic use of alpha-glucosidase inhibitors, such as acarbose, which attenuate postprandial hyperglycaemia-induced hyperinsulinaemia.