Vitamin D status, enterovirus infection, and type 1 diabetes in Italian children/adolescents.

At the time of the clinical onset of type 1 diabetes (T1D), we investigated 82 pediatric cases in parallel with 117 non-diabetic controls matched by age, geographic area, and time of collection. The occurrence of an enteroviral infection was evaluated in peripheral blood using a sensitive method capable of detecting virtually all human enterovirus (EV) types. While non-diabetic controls were consistently EV-negative, 65% of T1D cases carried EVs in blood. The vitamin D status was assessed by measuring the concentration of 25-hydroxyvitamin D [25(OH)D] in serum. Levels of 25(OH)D were interpreted as deficiency (≤50 nmol/L), insufficiency (52.5-72.5 nmol/L), and sufficiency (75-250 nmol/L). In T1D cases, the median serum concentration of 25(OH)D was 54.4 ± 27.3 nmol/L vs 74.1 ± 28.5 nmol/L in controls (P = .0001). Diabetic children/adolescents showed deficient levels of vitamin D 25(OH)D (ie, 72.5 nmol/L) in 48.8% cases vs 17.9% in non-diabetic controls (P = .0001). Unexpectedly, the median vitamin D concentration was significantly reduced in virus-positive vs virus-negative diabetics (48.2 ± 22.5 vs 61.8 ± 31.2 nmol/L; P = .015), with deficient levels in 58.5% vs 31.0%, respectively. Thus, at the time of clinical onset, EV-positive cases had reduced vitamin D levels compared with EV-negative cases. This could indicate either that the virus-negative children/adolescents had been hit by a non-infectious T1D-triggering event, or that children/adolescents with proper levels of vitamin D had been able to rapidly clear the virus. Thus, it would be important to assess whether adequate vitamin D supplementation before or during the prediabetic phase of T1D may counteract the diabetogenic potential of infectious pathogens.