Vascular responsiveness in type 2 diabetes mellitus (T2DM)

Diabetic retinopathy is used for staging of progression of micro and macro-vascular complications of patients with DM. Our hypothesis was that diabetic patients at different stages of retinopathy would have different vascular responsiveness that will be used as a surrogate marker of macro-vascular disease for risk assessment of cardiovascular complications.

A prospective study enrolled 96 patients. Twenty-three healthy volunteers (44 ± 11 years), 25 diabetic patients without retinopathy (63 ± 11 years), 25 patients with non-proliferative retinopathy [NPDR] (62 ± 9 years) and 23 patients with proliferative diabetic retinopathy [PDR] (59 ± 10 years). All patients underwent an ophthalmologic examination to diagnose retinopathy staging, and vascular responsiveness evaluation that included endothelial function evaluation (using the brachial artery method to measure flow mediated diameter change (FMD%)) and measuring the ankle-brachial blood pressure ratio, a measure of arterial stiffness.

Endothelial function was severely impaired in all diabetic patients. Patients with PDR had an FMD% of -3.1 ± 6.6%, patients with NPDR had -3.3 ± 9.2%, patients without retinopathy -1.9 ± 7.4% (P = NS between all groups of patients). Healthy controls had an FMD% of 16.5 ± 7.5% with a significant difference (P < 0.001) compared with each group of patients. No difference in FMD% was observed among patients (P = 0.93 between PDR and NPDR groups, P = 0.54 between NPDR and no retinopathy groups and P = 0.71 between patients without retinopathy and those with PDR).The ankle brachial (ABI) ratio was 1.03 ± 0.28 in the PDR group, 1.14 ± 0.24 in the NPDR group and 0.97 ± 0.18 in the no-retinopathy group. Healthy volunteers had an ABI of 1.07 ± 0.18. No difference was observed between ABI of PDR and NPDR patients (P = 0.17) and between patients without retinopathy and PDR patients (P = 0.91). However, a significant difference was observed between the NPDR and no-retinopathy groups (P = 0.008). No significant difference was found between ABI ratios when compared with the control group (P = 0.62 for PDR, P = 0.26 for NPDR and P = 0.07 for the no-retinopathy group). No difference was observed in age and BMI among all groups of patients (P = NS for all). Patients were older (P < 0.001) and had a higher BMI (P < 0.001). Interestingly there was no difference in height among groups of patients, but controls were significantly taller compared with each group of patients (P < 0.02).

All patients with T2DM had severe endothelial dysfunction with no difference among the different retinopathy groups. In our patients, all patients had a normal arterial stiffness but patients without retinopathy who had the highest arterial stiffness. We could not distinguish vascular traits that would define diabetic patients at the highest risk to develop cardiovascular complications.