Relationship between hemoglobin A1c level and flow-mediated vasodilation in patients with type 2 diabetes mellitus receiving antidiabetic drugs

Aims/Introduction Diabetes mellitus is associated with endothelial dysfunction. However, it is still controversial as to whether antidiabetic drug treatment affects endothelial function. The purpose of this study was to evaluate the relationships of the hemoglobin A1c (HbA1c) level with flow-mediated vasodilation (FMD) and nitroglycerine-induced vasodilation (NID) in patients with type 2 diabetes mellitus who are receiving antidiabetic drugs. Materials and Methods The FMD was measured in 866 patients with type 2 diabetes mellitus who were receiving antidiabetic drugs (625 men and 241 women; mean age: 62 +/- 10 years). The patients were divided into four groups according to HbA1c levels: <6.5, 6.5-6.9, 7.0-7.9, and >= 8.0%. Results There was an inverted U-shaped pattern of association of the HbA1c level with the FMD at an HbA1c level of about 7% of the peak of FMD in patients with type 2 diabetes mellitus who were receiving antidiabetic drugs. The FMD was significantly smaller in the HbA1c <6.5% group than in the HbA1c 6.5-6.9% group and the HbA1c 7.0-7.9% group (P < 0.001 and P < 0.001, respectively). The FMD values were similar in the HbA1c <6.5% group and HbA1c >= 8.0% group (P = 0.10). There were no significant differences in NID among the four groups (P = 0.98). Conclusions These findings suggest that a low HbA1c <6.5% as well as a high HbA1c >= 8.0% is associated with endothelial dysfunction in patients with type 2 diabetes mellitus who are receiving antidiabetic drugs and that vascular smooth muscle function is similar in such patients regardless of the HbA1c level.

Automated summary

This study investigated the relationship between HbA1c levels and vascular function in patients with type 2 diabetes mellitus receiving antidiabetic drug treatment. Results showed an inverted U-shaped association between HbA1c levels and FMD, with both low (<6.5%) and high (>= 8.0%) HbA1c levels associated with endothelial dysfunction, while vascular smooth muscle function was similar regardless of HbA1c levels.