Objectives:

This study aims to investigate 25-hydroxyvitamin D (25(OH)D) levels in patients with glucose and glycated hemoglobin (HbA1c) defined prediabetes and type 2 diabetes mellitus (T₂DM).

Patients and methods:

Eighty-nine prediabetic patients (44 males, 45 females; mean age 48.9±6.1 years) with impaired fasting glisemia (IFG) with glucose levels between 100-125 mg/dL (5.55-6.98 mmol/L) and HbA1c levels lower than 6.4% (46 mmol/mol), and 78 type 2 diabetic patients (40 males, 38 females; mean age 50.1±6.9 years) with HbA1c levels higher than 6.5% (48 mmol/mol) and glucose levels higher than 126 mg/dL (6.99 mmol/L) were included in the study. All patients were kept under strict control and were allowed to use their oral antidiabetics. Serum levels of glucose, insulin, HbA1c and 25(OH)D were measured in all patients. Insulin resistance was calculated by homeostasis model assessment formula.

Results:

While high density lipoprotein cholesterol (p=0.0001), insulin (p=0.013), insulin resistance (p=0.014), and vitamin D levels (p=0.0001) of T₂DM patients were significantly lower compared to the IFG group, their HbA1c levels were higher (p=0.0001). There was a negative correlation between vitamin D and HbA1c (r=-0.327, p=0.006), but a positive correlation between vitamin D and insulin (r=0.215, p=0.006), and vitamin D and HOMA-IR (r=0.236, p=0.002). Glycated hemoglobin levels were significantly higher in the T₂DM group than in the IFG group (p=0.0001). In the T₂DM group, 25(OH)D levels were lower compared to the IFG group (p<0.0001). 25-hydroxy vitamin D levels were inversely associated with HbA1c levels in the T₂DM group (p=0.0001, r=0.215).

Conclusion:

Vitamin D levels were lower in T₂DM group than in IFG group. Our findings indicate that vitamin D supplementation to T₂DM patients may improve glycemic control.

Keywords: