Article Text
Abstract
Objective The aim of this study was to determine the relationship of haemoglobin A1c (HbA1c) level with flow-mediated vasodilation (FMD) and nitroglycerine-induced vasodilation (NID) in patients with type 2 diabetes.
Design Cross-sectional study.
Setting 22 university hospitals and affiliated clinics in Japan.
Participants 1215 patients with type 2 diabetes including 349 patients not taking antidiabetic drugs.
Measures We evaluated FMD and HbA1c level. All patients were divided into four groups based on HbA1c level: <6.5%, 6.5%–6.9%, 7.0%–7.9% and ≥8.0%.
Results An inverted U-shaped pattern of association between HbA1c level and FMD was observed at the peak of HbA1c of about 7%. FMD was significantly smaller in the HbA1c <6.5% group than in the HbA1c 6.5%–6.9% group and HbA1c 7.0%–7.9% group (p<0.001 and p<0.001), and FMD values were similar in the HbA1c <6.5% group and HbA1c ≥8.0% group. There were no significant differences in NID values among the four groups. After adjustments for confounding factors, FMD was significantly smaller in the HbA1c <6.5% group than in the HbA1c 6.5%–6.9% and HbA1c 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 <6.5% group than in the HbA1c 6.5%–6.9% group and HbA1c 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 there is an inverted U-shaped pattern of association between FMD and HbA1c and that a low HbA1c level of <6.5% is associated with endothelial dysfunction.
Trial registration number UMIN000012950, UMIN000012951, UMIN000012952 and UMIN000003409.
- cardiology
- diabetes & endocrinology
- general diabetes
Data availability statement
Data are available upon reasonable request. There is no additional information.
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Data availability statement
Data are available upon reasonable request. There is no additional information.
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Footnotes
Contributors TY and YHi: drafting the article and conception of the study. TH, YHas, YT, MK, YHan, TM, SK, HH, CG, AN and FMY: acquiring subjects and/or data. EH, KC and YK: revising the article critically for important intellectual content. YHi is the guarantor of this work and as such had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of data analysis.
Funding Funding was received from Grant-in-Aid for Scientific Research from the Ministry of Education, Science and Culture of Japan (18590815 and 21590898 to YHi) and Grant-in-Aid of Japanese Arteriosclerosis Prevention Fund (to YHi).
Competing interests None declared.
Provenance and peer review Not commissioned; externally peer reviewed.
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