title: A case-sibling assessment of the association between skin pigmentation and other vitamin D-related factors and type 1 diabetes mellitus.
abstract: Fair skin pigmentation has been associated with a higher risk of type 1 diabetes mellitus (T1DM). The aim is to compare children with T1DM directly to a sibling in relation to their skin pigmentation in sun-exposed and unexposed sites, past sun exposure and methylation of the VDR gene promoter. The sample consisted of children with T1DM attending a diabetes outpatient clinic and siblings (total n=42). Cutaneous melanin density was estimated using a spectrophotometer. Parental report on past sun exposure was obtained. DNA methylation analysis of the VDR gene promoter was conducted. Matched data analysis was performed comparing each case directly to their sibling. Cases were significantly more likely to have lighter skin pigmentation at the upper arm (AOR 0.69 [95% CI: 0.52, 0.90]; P=0.01). Low infant sun exposure was imprecisely associated with a two-fold increase in T1DM risk (AOR 2.43 [95% CI: 0.91, 6.51]; P=0.08 for under 1 h of winter sun exposure per leisure day). The VDR gene promoter was completely unmethylated in both cases and siblings. The previously demonstrated association between light skin pigmentation and T1DM risk was evident even in this comparison across sibling pairs. Further work on past UVR exposure and related factors such as skin pigmentation is required.
authors.affiliation: Murdoch Children's Research Institute, Royal Children's Hospital, Department of Paediatrics, University of Melbourne, Melbourne, Vic., Australia. anne-louise.ponsonby@mcri.edu.au
authors.forename: Anne-Louise
authors.initials: AL
authors.lastname: Ponsonby
authors.forename: Fergus
authors.initials: F
authors.lastname: Cameron
authors.forename: Richard
authors.initials: R
authors.lastname: Saffery
authors.forename: Angela
authors.initials: A
authors.lastname: Pezic
authors.forename: Nick
authors.initials: N
authors.lastname: Wong
authors.forename: Jeff
authors.initials: J
authors.lastname: Craig
authors.forename: Justine
authors.initials: J
authors.lastname: Ellis
authors.forename: Terence
authors.initials: T
authors.lastname: Dwyer
mesh_terms: D001483:Base Sequence; D016022:Case-Control Studies; D017931:DNA Primers; D003922:Diabetes Mellitus, Type 1 / Q000473:pathology*; D006801:Humans; D012880:Skin Pigmentation; D014807:Vitamin D / Q000235:genetics*
chemical_list: D017931:DNA Primers; D014807:Vitamin D