Long-term hyperglycaemia impairs vascular smooth muscle cell function in women with type 1 diabetes mellitus

Observations of increased stiffness in the elastic aorta in women with diabetes, but not men, emphasise the need for further analysis regarding early abnormalities in arterial wall properties of women with type 1 diabetes mellitus (DM). Ultrasound was used to study the wall properties of the distal brachial artery (BA) in 37 type 1 diabetic women (aged 22-45 years) without evident complications and in 53 controls (C). Blood samples were drawn for later analysis. Flow-mediated dilatation (FMD) was slightly lower in DM than C, 8.1+/-4.3% vs. 10.3+/-4.9% (p<0.05), and nitrate-mediated dilatation (NMD) was markedly lower, 21.7+/-6.6% vs. 31.4+/-5.7% (p<0.001). Lumen diameter, intima-media thickness and distensibility were similar in DM and C. Insulin-like growth factor (IGF-1) was lower in DM than C, 231+/-65 vs. 349+/-68 ng/ml (p<0.001). Glycosylated haemoglobin (HbA1C) and matrix metalloproteinase (MMP-9) were independent predictors of the reduced NMD in the DM. Brachial artery responsiveness to an exogenous donor of nitric oxide (NO) was markedly reduced in type 1 diabetic women despite only limited reduction in endothelium-dependent dilatation. The negative association between NMD and HbA1C suggests that long-term hyperglycaemia impairs vascular smooth muscle cell function in DM.