Inconvenient relationship of haemoglobin A1c level with endothelial function in type 2 diabetes in a cross-sectional
Takayuki Yamaji1, Takahiro Harada1, Yu Hashimoto1
1Department of Cardiovascular Medicine, Hiroshima University Faculty of Medicine Graduate School of Biomedical and Health Sciences, Hiroshima, Japan.
BMJ Open
|June 10, 2021
Summary
This study reveals an inverted U-shaped relationship between hemoglobin A1c (HbA1c) levels and flow-mediated dilation (FMD) in type 2 diabetes patients. Critically, low HbA1c levels (<6.5%) are linked to endothelial dysfunction.
Area of Science:
- Endocrinology
- Cardiovascular Medicine
- Diabetes Research
Background:
- Endothelial dysfunction is a key factor in the progression of cardiovascular complications in type 2 diabetes.
- Hemoglobin A1c (HbA1c) is a standard measure of long-term glycemic control.
- The relationship between HbA1c levels and endothelial function, particularly at lower ranges, requires further elucidation.
Purpose of the Study:
- To investigate the association between hemoglobin A1c (HbA1c) levels and endothelial function, specifically flow-mediated vasodilation (FMD) and nitroglycerine-induced vasodilation (NID).
- To determine if varying levels of glycemic control, including lower HbA1c ranges, impact vascular function in patients with type 2 diabetes.
Main Methods:
- A cross-sectional study involving 1215 patients with type 2 diabetes across 22 university hospitals in Japan.
- Patients were categorized into four groups based on HbA1c levels: <6.5%, 6.5%-6.9%, 7.0%-7.9%, and ≥8.0%.
- Flow-mediated vasodilation (FMD) and nitroglycerine-induced vasodilation (NID) were assessed, along with HbA1c levels.
Main Results:
- An inverted U-shaped association was observed between HbA1c levels and FMD, peaking around 7% HbA1c.
- FMD was significantly lower in patients with HbA1c <6.5% compared to those with HbA1c 6.5%-6.9% and 7.0%-7.9% (p<0.001 for both).
- No significant differences in NID were found across the HbA1c groups, suggesting a specific impact on endothelium-dependent vasodilation.
Conclusions:
- The study indicates an inverted U-shaped relationship between FMD and HbA1c levels in type 2 diabetes.
- A low HbA1c level (<6.5%) is associated with endothelial dysfunction, highlighting potential risks of overly aggressive glycemic control on vascular health.
- These findings underscore the importance of optimizing, rather than solely minimizing, glycemic control for cardiovascular health in diabetes management.
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