Relationship between serum 25-hydroxyvitamin D and inflammatory cytokines in Nigerian children with asthma

Background: Childhood asthma involves a network of mutually interacting inflammatory mediators and cytokines. The influence of serum vitamin D (an immunomodulatory agent) on these cytokines is poorly understood. This study sets out to determine the relationship between serum T-helper cells type 1 cytokines (Interleukins ILs-1 beta, 2, 6, 8 and 10), type 2 cytokines (ILs 3, 4,5,9,13), ILs-12, 17 and 25-hydroxyvitamin D (25-OHD) in Nigerian children with asthma. Methods: Children with physician-diagnosed asthma and non-asthmatics aged 2-15 years were consecutively recruited at a tertiary center in Nigeria. Serum 25-OHD and cytokines were assayed using chromatography method and association between these parameters determined. Results: A total of 180 children (90 for each group; mean age 7.5 +/- 3.9 years; M:F 1.9:1) were recruited. Fifty-six (76.7%) asthmatics had mild intermittent form and symptoms were sub-optimally controlled in 16 (21.9%). The mean (SD) serum Vitamin D was lower in children with asthma (38.8 +/- 17.0 ng/ml vs. 45.5 +/- 16.6 ng/ml vs. p = 0.023). Also more proportion of children with asthma had suboptimal serum vitamin D level (26.0% vs. 8.8%; p = 0.022). Deficient vitamin D state was associated with higher serum Th-1 and Th-2 cytokines compared to insufficient state, but the highest cytokine levels were observed in normal vitamin D state. There was significant positive correlation between serum vitamin D and Th-1 cytokines IL-2 and IL-8 as well as Th-2 cytokines (ILs-3, 4, 5 and 9), but negative correlation with IL-13 Conclusions: Serum Vitamin D and cytokines were lower in a sample of Nigerian children with asthma than controls. Vitamin D status was not related to asthma severity and control. Serum 25-OHD seems to have a non-linear relationship with Th-1 and Th-2 cytokines in Nigerian asthmatics.