Endocrine Abstracts (2011) 27 OC5.2

Investigating vitamin D status as a determinant of HbA1C% in type 1 diabetic paediatric population

Lucia Magee1, Zulf Mughal2, Sarah Ehtisham2, Judith Campbell2, Susan Ainsworth2, Marie Marshall2, Mark Bone2, Ian Doughty2 & Peter Clayton1

1University of Manchester, Manchester, UK; 2Royal Manchester Children’s Hospital, Manchester, UK.

Maintaining glycaemic control within recommended levels is crucial to minimise vascular complications associated with type 1 diabetes (T1D). Vitamin D is recognised as a vascular growth-factor. Detection of its receptors on pancreatic β-cells suggests it may have a role in glycaemic control. This study aimed to assess determinants of HbA1C including the potential influence of vitamin D status in a T1 diabetic paediatric population.

Methods: Patients attending clinic were recruited. Age, ethnicity, sex, height, weight, HbA1C, insulin dose and duration of diabetes were recorded at each visit from the time of diagnosis. 25(OH)D3 was measured at recruitment. To explore the potential relationship between HbA1C and 25(OH)D3, we analysed cross-correlation factor (CCF) between mean monthly HbA1C and median hours of daylight per month.

Results: Fifty-three patients (28 males) were recruited (mean age 12.5 years, range 3.7–19.3). Main determinants of HbA1C from time of diagnosis were age and basal-insulin dose u/kg per day (R2=0.108, P<0.001). 84% of patients were 25(OH)D3 deficient (14.9 ng/ml, range 7.7–26.6) at recruitment. All South-Asian children (n=11) were deficient. There was a significant negative relationship between HbA1C at recruitment and 25(OH)D3 in Caucasian children (P<0.01). Lowest monthly mean HbA1C was in August (8.58%) and highest in December (9.41%). At a time-lag of 0 the CCF was −0.527, indicating a strong inverse relationship. Moving the HbA1C data-series forward resulted in a positive CCF (+0.109) at a lead of 3 months.

Conclusion: 25(OH)D3 deficiency is prevalent amongst T1 diabetic children, particularly South-Asians. In Caucasian children higher HbA1C was significantly associated with lower 25(OH)D3. The cross-correlation data between HbA1C and hours of sunlight suggests a link between UVB radiation (hence 25(OH)D3) and control of T1D, with hours of sunlight impacting on HbA1C 3 months later. We suggest that measurement of vitamin D and treating deficiency should be part of regular monitoring in paediatric diabetic clinics.