Free and biousability vitamin D levels in TYPE 1 diabetes mellitus patients

ABSTRACT Aim: Type-1 Diabetes Mellitus (Type-1 DM) is one of the most common chronic diseases in children. While trying to elucidate its etiopathogenesis, researchers found that children with Type1-DM had lower levels of total 25-hydroxyvitamin D [25(OH)D]) and they had vitamin D receptor in their pancreatic beta cells. The studies examining the relationship between vitamin D levels and diabetes report contradicting results. Recent research have revealed that the use of free 25 (OH) D fraction and bioavailable 25(OH)D levels instead of serum total 25(OH)D levels could prove better results to show the actual serum 25(OH)D levels. In this study, we aimed to examine the bioavailable 25(OH)D and calculated free 25(OH)D fractions in pediatric patients with Type-1 DM, as well as any possible roles of these fractions in the etiopathogenesis of Type-1 DM. Methods: The study included 47 patients recently diagnosed with Type-1 DM (21 females and 26 males; mean age: 9.70 ± 4.26 years) and 61 healthy controls (26 females and 35 males; mean age: 9.13 ± 4.43). Total serum 25(OH)D levels, vitamin D binding globulin (DBP) and albumin levels were measured in all participants. Free fraction of 25(OH)D and bioavailable 25(OH)D levels were calculated by affinity constant of 25(OH)D for DBP and albumin. Results: The mean total 25(OH)D levels in Type-1 DM patients were significantly lower than that of the control group (17.36 ± 5.91 ng/ml and 22.02 ± 7.38 ng/ml, p=0.0006). The calculated free 25(OH)D levels were 47.36 ± 35.14 pmol/L in the patient group and 65.6 ± 35.55 pmol/L in the control group (p<0.01). Bioavailable 25(OH)D levels were 18.01 ± 13.38 nmol/L in patients and 26.97 ± 14.01 nmol/L in the control group (p=0.0011). Conclusion: Based on the results of our study, we suggest that the total calculated free and bioavailable 25(OH)D levels in patients with Type1 DM are significantly lower, and despite the decrease in all the fractions of vitamin D, bioavailable 25(OH)D levels could be used as a better indicator for vitamin D deficiency, and low levels may be playing a role in the etiopathogenesis of Type-1 DM. Key words: Type 1 diabetes mellitus, bioavailable vitamin D, calculated free vitamin D, vitamin D deficiency.