Objective Low vitamin D levels have been implicated in the development of and increased morbidity from asthma. The prevalence of asthma among urban African American (AA) youth is high. The goal of this study was to examine the prevalence of vitamin D insufficiency and deficiency among urban AA youth with asthma compared with non-asthmatic controls. Study Design A cross-sectional case-control study was conducted at an urban pediatric medical center. Total 25-hydroxyvitamin D insufficiency (< 30 ng/mL) and deficiency (< 20 ng/mL) were assessed in urban self-reported AA patients, aged 6 to 20 years, with (n = 92) and without (n = 21) physician-diagnosed asthma. Results Blood samples were available for 85 (92%) cases. After adjusting for age, gender, body mass index percentile, and season of sampling, the median vitamin D level of cases [18.5 (interquartile range (IQR): 11.3, 25.1)] was significantly lower than that of controls [40.4 (IQR: 34.6, 49.5), P = 0.002]. The prevalences of vitamin D insufficiency and deficiency were significantly greater among cases than controls [73/85 (86%) vs. 4/21 (19%), adjusted odds ratio (OR) = 41.7 (95% confidence interval (95%CI): 4.4 to 398.5) for insufficiency and 46/85 (54%) vs. 1/21 (5%), adjusted OR = 19.5 (95%CI: 1.4 to 272.0) for deficiency]. Conclusions A majority of this sample of urban AA youth with persistent asthma were vitamin D deficient and/or insufficient. Given the emerging associations between low vitamin D levels and asthma, strong consideration should be given to routine vitamin D testing in urban AA youth, particularly those with asthma. Clinical trials of vitamin D supplementation among urban AA youth with asthma are warranted.

Asthma is an inflammatory condition for which anti-inflammatory glucocorticoids are the standard of care. However, similar efficacy has not been shown for agents targeting inflammatory cells and pathways. This suggests a noninflammatory cell contributor (e.g., epithelium) to asthmatic inflammation. Herein, we sought to define the intrinsic and glucocorticoid-affected properties of asthmatic airway epithelium compared with normal epithelium. Human primary differentiated normal and asthmatic airway epithelia were cultured in glucocorticoid-free medium beginning at 248 hours. They were pulsed with dexamethasone (20 nM) or vehicle for 2 hours at 226, 22, 122, and 146 hours. Cultures were mechanically scrapewounded at 0 hours and exposed continuously to bromodeoxyuridine (BrdU). Cytokine secretions were analyzed using cytometric bead assays. Wound regeneration/mitosis was analyzed by microscopy and flow cytometry. Quiescent normal (n 5 3) and asthmatic (n 5 6) epithelia showed similar minimal inflammatory cytokine secretion and mitotic indices. After wounding, asthmatic epithelia secreted more basolateral TGF-b1, IL-10, IL-13, and IL-1b (P , 0.05) and regenerated less efficiently than normal epithelia (148 h wound area reduction 5 [mean 6 SEM] 50.2 6 7.5% versus 78.6 6 7.7%; P 5 0.02). Asthmatic epithelia showed 40% fewer BrdU 1 cells at 148 hours (0.32 6 0.05% versus 0.56 6 0.07% of total cells; P 5 0.03), and those cells were more dyssynchronously distributed along the cell cycle (52 6 10, 25 6 4, 23 6 7% for G1/G0, S, and G2/M, respectively) than normal epithelia (71 6 1, 12 6 2, and 17 6 2% for G1/G0, S, and G2/M, respectively). Dexamethasone pulses improved asthmatic epithelial inflammation and regeneration/mitosis. In summary, we show that inflammatory/fibrogenic cytokine secretions are correlated with dyssynchronous mitosis upon injury. Intermittent glucocorticoids simultaneously decreased epithelial cytokine secretions and resynchronized mitosis. These data, generated in an airway model lacking inflammatory cells, support the concept that epithelium contributes to asthmatic inflammation.

Introduction Low vitamin D levels have been associated with asthma severity in children. Young, urban African Americans (AA) have high rates of hypovitaminosis D and asthma. Our objective was to determine associations between variants in vitamin D metabolism genes and asthma characteristics in a pilot study of young urban AAs. Materials and Methods Two urban AA cohorts of subjects aged 6 to 20 years (139 subjects with asthma and 74 subjects without asthma) were genotyped for 12 single nucleotide polymorphisms (SNPs) in 3 vitamin D metabolism genes: VDR (vitamin D receptor), CYP24A1 (cytochrome P450 vitamin D 24-hydroxylase), and CYP2R1 (cytochrome P450 vitamin D 25-hydroxylase). In a case-control analysis, SNPs were studied for associations with an asthma diagnosis. Within the asthmatic cohort, SNPs were analyzed for associations with quantitative asthma characteristics. All analyses were adjusted for age, gender, and BMI percentile. Results Only the CYP2R1 SNP rs10766197 homozygous minor genotype was associated with asthma (P=0.044). CYP24A1 SNP rs2248137 was associated with lower vitamin D levels (P=0.006). Within the asthma cohort, multiple significant associations between SNPs and asthma characteristics were identified; VDR SNP rs2228570 was associated with the higher nighttime asthma morbidity scores (P=0.04), lower baseline spirometric measures (P<0.05), ≥1 positive aeroallergen skin test (P=0.003), and increased IgE levels (P<0.001). Discussion This pilot study demonstrates that variants in vitamin D metabolism genes are associated with quantitative asthma characteristics in young, urban AAs. The collection of these associations provides evidence for the need for a large population-based study of vitamin D relevant SNPs in this cohort.