Abstract
Background Diabetes is associated with endothelial dysfunction. However, there is little information on the relationship between hemoglobin A1c (HbA1c) level and endothelial function. This study evaluated the relationship between HbA1c level and flow-mediated vasodilation (FMD).Methods We measured FMD in 1215 patients with type 2 diabetes including 349 patients not taking antidiabetic drugs and 866 patients taking antidiabetic drugs. The patients were divided into four groups based on HbA1c levels: <48 mmol/mol, 48–52 mmol/mol, 53–63 mmol/mol, and ≥ 64 mmol/mol. (< 6.5%, 6.5–6.9%, 7.0-7.9%, ≥ 8.0%)Results An inverted U-shaped pattern of association between HbA1c level and FMD was observed at the peak of HbA1c of about 53 mmol/mol (7%). FMD was significantly smaller in the HbA1c < 48 mmol/mol (6.5%) group than in the HbA1c 48–52 mmol/mol (6.5–6.9%) group and HbA1c 53–63 mmol/mol (7.0-7.9%) group (p < 0.001 and p < 0.001), and FMD values were similar in the HbA1c < 48 mmol/mol (6.5%) group and HbA1c ≥ 64 mmol/mol (8.0%) group. There were no significant differences in nitroglycerine-induced vasodilation (NID) values among the four groups. After adjustments for confounding factors, FMD was significantly smaller in the HbA1c < 48 mmol/mol (6.5%) group than in the HbA1c 48–52 mmol/mol (6.5–6.9%) and HbA1c 53–63 mmol/mol (7.0-7.9%) group (p = 0.002 and p = 0.04). In patients not taking antidiabetic drugs, FMD was also significantly smaller in the HbA1c < 48 mmol/mol (6.5%) group than in the HbA1c 48–52 mmol/mol (6.5–6.9%) group and HbA1c 53–63 mmol/mol (7.0-7.9%) group (p < 0.001 and p = 0.02), and there were no significant differences in NID values among the four groups.Conclusions These findings suggest that a low HbA1c level of < 48 mmol/mol (6.5%) is associated with endothelial dysfunction. An HbA1c level of 48–52 mmol/mol (6.5–6.9%) may be appropriate for maintenance of endothelial function.
An Inconvenient Relationship of Hemoglobin A1c Level with Endothelial Function in Type 2 Diabetes
