Abstract: AIM: To investigate the effects of serum 25-hydroxyvitamin D (25(OH)D) on the blood glucose and islet β-cells function in the elderly with type 2 diabetes (T2DM). METHODS: Fifty-eight elderly patients with type 2 diabetes were recruited from June 2019 to January 2020, and all the patients were divided into three groups according to levels of serum 25(OH)D. Age, body mass index (BMI) and the levels of fasting blood glucose (FBG), hemoglobin A1c (HbA1c) were analyzed. Steamed bread meal test was performed in all patients, and the levels of blood glucose and C-peptide were compared among the three groups at the time points of 0, 30, 60, 120 and 180 min to investigate the effect of serum 25(OH)D on the islet β-cells function．RESULTS: Compared with the elderly T2DM patients with sufficient 25(OH)D, the HbA1c increased significantly in the elderly T2DM patients with deficiency of 25(OH)D (P<0.05). The levels of blood glucose were increased at the time points of 120 min and 180 min, while the levels of C-peptide at the time point of 60 min and 120 min, C peptide index and AUCCP180 in elder T2DM patients decreased significantly (P<0.05). Pearson correlation analysis showed that serum was negatively correlated with HbA1c, and positively correlated with the C peptide and C peptide index and AUCCP180 (P<0.05). And stepwise multiple regression analysis indicated that C peptide was a factor influencing 25(OH)D levels. CONCLUSION: Elderly T2DM patients with deficiency of 25(OH)D are more likely to suffer with severe dysfunction of islet β-cells．

Key words: elderly patients, 25-hydroxyvitamin D, type 2 diabetes mellitus, β-cell