title: Decreased serum vitamin D levels in children with asthma are associated with increased corticosteroid use.
abstract: BACKGROUND
  There is little knowledge about clinical variables associated with vitamin D (VitD) insufficiency in asthmatic children.
  
  
  OBJECTIVE
  We sought to investigate disease variables associated with VitD insufficiency in patients with childhood asthma and interaction of VitD with corticosteroid-mediated anti-inflammatory responses.
  
  
  METHODS
  We analyzed 25-hydroxyvitamin D serum levels in 100 asthmatic children to investigate relationships between 25-hydroxyvitamin D levels and patients' characteristics. We determined VitD's effects on dexamethasone (DEX) induction of mitogen-activated protein kinase phosphatase 1 and IL-10 in PBMCs.
  
  
  RESULTS
  The median 25-hydroxyvitamin D serum level was 31 ng/mL. Forty-seven percent of subjects had VitD levels in the insufficient range (<30 ng/mL), whereas 17% were VitD deficient (<20 ng/mL). Log(10) IgE (P = .01, rho = -0.25) and the number of positive aeroallergen skin prick test responses (P = .02, rho = -0.23) showed a significant inverse correlation with VitD levels, whereas FEV(1) percent predicted (P = .004, rho = 0.34) and FEV(1)/forced vital capacity ratio (P = .01, rho = 0.30) showed a significant positive correlation with VitD levels. The use of inhaled steroids (P = .0475), use of oral steroids (P = .02), and total steroid dose (P = .001) all showed significant inverse correlations with VitD levels. The amount of mitogen-activated protein kinase phosphatase 1 and IL10 mRNA induced by VitD plus DEX was significantly greater than that induced by DEX alone (P < .01). In an experimental model of steroid resistance in which DEX alone did not inhibit T-cell proliferation, addition of VitD to DEX resulted in significant dose-dependent suppression of cell proliferation.
  
  
  CONCLUSIONS
  Corticosteroid use and worsening airflow limitation are associated with lower VitD serum levels in asthmatic patients. VitD enhances glucocorticoid action in PBMCs from asthmatic patients and enhances the immunosuppressive function of DEX in vitro.
authors.affiliation: Division of Allergy and Immunology, Department of Pediatrics, National Jewish Health, Denver, CO 80206, USA.
authors.forename: Daniel A
authors.initials: DA
authors.lastname: Searing
authors.forename: Yong
authors.initials: Y
authors.lastname: Zhang
authors.forename: James R
authors.initials: JR
authors.lastname: Murphy
authors.forename: Pia J
authors.initials: PJ
authors.lastname: Hauk
authors.forename: Elena
authors.initials: E
authors.lastname: Goleva
authors.forename: Donald Y M
authors.initials: DY
authors.lastname: Leung
mesh_terms: D001249:Asthma / Q000188:drug therapy*; D002648:Child; D002675:Child, Preschool; D003907:Dexamethasone / Q000494:pharmacology / Q000627:therapeutic use*; D054638:Dual Specificity Phosphatase 1 / Q000378:metabolism; D005260:Female; D005938:Glucocorticoids / Q000494:pharmacology / Q000627:therapeutic use*; D006801:Humans; D016753:Interleukin-10 / Q000378:metabolism; D008213:Lymphocyte Activation; D008297:Male; D016133:Polymerase Chain Reaction; D013601:T-Lymphocytes / Q000276:immunology / Q000378:metabolism; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000097:blood; D014808:Vitamin D Deficiency / Q000209:etiology*
chemical_list: D005938:Glucocorticoids; D016753:Interleukin-10; D014807:Vitamin D; D003907:Dexamethasone; C104450:25-hydroxyvitamin D; D054638:Dual Specificity Phosphatase 1
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