Correlations of cholecalciferol-levels, daily insulin dose and clinical features in patients with Type 1 diabetes mellitus

Aims: Type 1 Diabetes mellitus(T1D) is caused by a complex process of altered humoral and cellular immunity, resulting in the destruction of insulin-producing cells. VD(25(OH)D3) insufficiency is implied as risk factor for T1D, whereas VD substitution in infantry is associated with a reduced risk of T1D. In T1D a daily insulin injection is required for a stable glucose homeostasis and insulin demand rises by a higher Body Mass Index(BMI). Today there are no studies investigating the relationship between endogenous VD production and insulin demand in T1D.

Patients and methods: Patients with T1D(n = 29) were examined for insulin demand (Carbohydrate Factor-IU/12 g carbohydrates(CF); basal insulin-IU/d), BMI(kg/m²) and VD(ng/ml). For our statistical studies we used the Mann-Whitney-U and Spearman's tests; p < 0.05 was significant.

Results: The median VD was 18.7, n = 16(55.17%) patients were VD insufficient(< 20) and n = 13(44.82%) sufficient(> 20). Interestingly, CF in the afternoon was significantly higher in the group with VD< 20 than in the group > 20(2 vs. 1.25;p = 0.03). CF in the morning and basal insulin exhibited a trend to be higher in the group with VD< 20 compared to the group with VD> 20 (2 vs. 1.3 and 18.1 vs. 17.65;p = 0.09 and p = 0.15 resp.). Furthermore the median BMI was 24.8, so we divided our patients in 2 groups (BMI< 24.8>resp.). The VD levels didn't differ between the groups (p = 0.96). A significant negative correlation between CF, basal insulin and VD levels was proven in the group with BMI> 24.8(p < 0.05, rho =-0.57 resp.) whereas in the group with BMI< 24.8 there were no significant results.

Conclusion: In our pilot study we proved that lower VD levels are associated with a higher insulin demand; by a BMI over the median range of 24.8, these parameters were significantly negatively correlated. Interesting would be to study whether higher VD levels through a VD treatment would decrease the insulin demand;this hypothesis we are investigating in our ongoing VD study.