title: Expression of beta-cell autoimmunity does not differ between potential dizygotic twins and siblings of patients with type 1 diabetes.
abstract: Twin studies help to elucidate the contribution of genes and environment to type 1 diabetes (T1DM). The Diabetes Prevention Trial-1 (DPT-1) tested for anti-islet autoantibodies: 34,765 non-diabetic non-twin siblings of patients with T1DM, and 896 non-diabetic potential twins of patients with T1DM. Zygosity (being monozygotic [MZ] or dizygotic [DZ]) was unknown except for 357 non-diabetic subjects with opposite gender to their diabetic twin, who must be DZ. Expression of cytoplasmic islet cell (ICA), GAD65, ICA512 and insulin autoantibodies in 357 different-sex (DZ) potential non-diabetic twins of T1DM patients was, respectively, 4.5%, 4.7%, 3.0% and 2.4%, which was lower than in 539 same-sex potential non-diabetic twins (including MZ and DZ) of T1DM patients for ICA (7.8%, p < 0.05), GAD65 (13.4%, p < 0.0001) and ICA512 (6.5%, p < 0.03). In contrast, expression of ICA, GAD65, ICA512 and insulin autoantibodies was not significantly different in different-sex (DZ) potential twins versus all siblings (respectively, 4.2%, 4.8%, 2.2%, 2.5%), different-sex siblings (3.9%, 4.9%, 2.2%, 2.5%) or same-sex siblings (4.4%, 4.7%, 2.2%, 2.5%) of T1DM patients. In conclusion, anti-islet autoimmunity is not increased in non-diabetic DZ twins of T1DM patients compared to non-diabetic siblings of T1DM patients, suggesting that the greater environmental sharing by twins does not increase risk of anti-islet autoimmunity.
authors.affiliation: Barbara Davis Center for Childhood Diabetes, University of Colorado Health Sciences Center, 4200 East Ninth Avenue B-140, Denver, CO 80262, USA.
authors.forename: Maria J
authors.initials: MJ
authors.lastname: Redondo
authors.forename: Pamela R
authors.initials: PR
authors.lastname: Fain
authors.forename: Jeffrey P
authors.initials: JP
authors.lastname: Krischer
authors.forename: Liping
authors.initials: L
authors.lastname: Yu
authors.forename: David
authors.initials: D
authors.lastname: Cuthbertson
authors.forename: William E
authors.initials: WE
authors.lastname: Winter
authors.forename: George S
authors.initials: GS
authors.lastname: Eisenbarth
mesh_terms: D015551:Autoimmunity / Q000276:immunology*; D003922:Diabetes Mellitus, Type 1 / Q000276:immunology* / Q000473:pathology; D005260:Female; D006801:Humans; D007515:Islets of Langerhans / Q000276:immunology* / Q000473:pathology; D008297:Male; D010375:Pedigree; D035781:Siblings; D014429:Twins, Dizygotic / Q000276:immunology*