title: Vitamin D status and the predictors of circulating T helper 1-type immunoglobulin levels in Iranian subjects with type 1 diabetes and their siblings: a case-control study.
abstract: BACKGROUND
  Vitamin D status has been linked to both T helper (Th)1/Th2 balance and susceptibility to type 1 diabetes (T1D). The present study aimed to evaluate vitamin D status and its relation to Th1/Th2 balance in subjects with T1D, their siblings and unrelated healthy controls during autumn and winter 2008-2009.
  
  
  METHODS
  A case-control study was conducted on subjects with T1D (n(1) = 60) and two control groups comprising nondiabetic siblings (n(2) = 60) and unrelated healthy controls (n(3) = 60). Assessments of dietary intake, anthropometry, intact parathyroid hormone (iPTH) and 25(OH)D were performed. Serum levels of immunoglobulin (Ig)G(2) and IgE, as well as the IgG2/IgE ratio, were used to evaluate Th1/Th2 balance. Vitamin D status was defined based on circulating 25(OH)D as deficiency: <27.5 nm; insufficiency 27.5 ≤ 25(OH)D <50 nm; and sufficiency ≥50 nm.
  
  
  RESULTS
  Vitamin D status did not differ significantly among the groups. Similarly, no significant difference in 25(OH)D, iPTH, IgG(2), IgE and IgG(2)/IgE was found. In multiple regression analysis of pooled data, PTH and body mass index were the predictors of IgG(2)/IgE. In the diabetic group, both PTH and age and, in siblings, PTH only, were the predictors of IgG(2)/IgE ratio.
  
  
  CONCLUSIONS
  These data suggest PTH as the major predictor of immune deviance towards the Th1 response in both type 1 diabetic subjects and their siblings. Considering that the active form of vitamin D suppresses PTH production, it is hypothesised that vitamin D replenishment of just those who are genetically prone to the disease (i.e. siblings) may be regarded as a preventive measure against T1D.
authors.affiliation: Department of Nutrition and Biochemistry, Faculty of Public Health, Tehran University of Medical Sciences (TUMS), Tehran, Iran.
authors.forename: Z
authors.initials: Z
authors.lastname: Ghandchi
authors.forename: T R
authors.initials: TR
authors.lastname: Neyestani
authors.forename: A-A Saboor
authors.initials: AA
authors.lastname: Yaraghi
authors.forename: M-R
authors.initials: MR
authors.lastname: Eshraghian
authors.forename: A
authors.initials: A
authors.lastname: Gharavi
authors.forename: N
authors.initials: N
authors.lastname: Shariatzadeh
authors.forename: A
authors.initials: A
authors.lastname: Kalayi
authors.forename: A
authors.initials: A
authors.lastname: Houshiarrad
mesh_terms: D000293:Adolescent; D000328:Adult; D015992:Body Mass Index; D016022:Case-Control Studies; D002648:Child; D002675:Child, Preschool; D003922:Diabetes Mellitus, Type 1 / Q000097:blood / Q000276:immunology*; D002149:Energy Intake; D005260:Female; D006801:Humans; D007073:Immunoglobulin E / Q000097:blood; D007074:Immunoglobulin G / Q000097:blood; D007136:Immunoglobulins / Q000097:blood*; D007492:Iran; D008297:Male; D009752:Nutritional Status; D010281:Parathyroid Hormone / Q000097:blood; D006377:T-Lymphocytes, Helper-Inducer / Q000276:immunology*; D018417:Th1 Cells / Q000276:immunology; D018418:Th2 Cells / Q000276:immunology; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000097:blood; D014808:Vitamin D Deficiency / Q000097:blood / Q000175:diagnosis* / Q000276:immunology
chemical_list: D007074:Immunoglobulin G; D007136:Immunoglobulins; D010281:Parathyroid Hormone; D014807:Vitamin D; D007073:Immunoglobulin E; C104450:25-hydroxyvitamin D