Relationship of Vitamin D Levels with HbA1c and Fructosamine in Korean Type 2 Diabetic Patients

Abstract

Objectives Although previous studies reported an association of serum vitamin D with glycated hemoglobin (HbA1c) and fructosamine, the relationships remain unclear. Therefore, this study aims to identify the relationships of serum vitamin D with HbA1c and fructosamine independent of parathyroid hormone (PTH) in Korean type 2 diabetic patients. Methods Total 227 adults (male 112 and female 115) who treated for type 2 diabetes in a general hospital participated in this study. The serum vitamin D, HbA1c, fructosamine and fasting blood glucose (FBG) were measured in participants who met the detailed inclusion criteria. The level of serum vitamin D was defined as follows; deficient: <10.0 ng/mL, insufficient: 10.0-19.9 ng/mL, optimal: ≥20.0 ng/m. Results In the analysis of covariance, after adjusted for other covariates including PTH, the means (standard error, SE) values of HbA1c became lower with higher serum vitamin D level (deficiency: 7.8 [0.2]%, insufficient: 7.5 [0.1]%, optimal: 7.2 [0.1]%, p=0.015). Also, after adjusted for other covariates including PTH, the mean (SE) values of fructosamine became lower with higher serum vitamin D level (deficiency: 357.1 [13.1] μmol/L, insufficient: 344.5 [4.9] μmol/L, optimal: 313.3 [6.4] μmol/L, p=0.001). However, the mean values of FBG were not significantly associated with the serum vitamin D level. Conclusions There were significant associations of vitamin D with HbA1c and fructosamine independent of PTH, but there was no association of vitamin D with FBG in Korean type 2 diabetic patients. Key words: Diabetes mellitus, Vitamin D, Glycated hemoglobin A, Fructosamine, Parathyroid hormone