title: Quantitation of glutamic acid decarboxylase autoantibody levels in prospectively evaluated relatives of patients with type I diabetes.
abstract: In this study, we demonstrate that levels of glutamic acid decarboxylase (GAD) autoantibodies (GAAs) by radioassay differ between relatives with GAD-absorbable and GAD-nonabsorbable islet cell antibodies (ICAs). Extremely high levels of GAAs are often found in relatives with GAD-absorbable ICAs (> 1,800 cpm, > 9 SD above normal control subjects; mean = 1,991 cpm), and lower levels (mean = 1,078 cpm) of GAAs were present in relatives with nonabsorbable ICAs (P < 10(-5). The serum levels of GAAs were remarkably constant for relatives of both groups over time. The levels of GAAs were found to be inversely related to both the levels of insulin autoantibodies and the rate of loss of intravenous glucose-stimulated insulin secretion (P < 10(-5) and P < 0.01, respectively). Relatives with low positive levels of GAAs had more rapid loss of insulin secretion and were at high risk to become diabetic (50% diabetic at 4 years) compared with relatives with higher levels (1,800 cpm) of GAAs (10% diabetic at 4 years; P < 0.05). These data suggest that high levels of GAAs are associated with a decreased risk of progression to type I diabetes and extend the hypothesis that distinct subsets of ICAs and GAAs with differing prognostic significance can be identified.
authors.affiliation: Barbara Davis Center for Childhood Diabetes, University of Colorado Health Sciences Center, Denver 80262.
authors.forename: L
authors.initials: L
authors.lastname: Yu
authors.forename: R
authors.initials: R
authors.lastname: Gianani
authors.forename: G S
authors.initials: GS
authors.lastname: Eisenbarth
mesh_terms: D000293:Adolescent; D000328:Adult; D001323:Autoantibodies / Q000097:blood*; D001786:Blood Glucose / Q000378:metabolism; D002648:Child; D002675:Child, Preschool; D003922:Diabetes Mellitus, Type 1 / Q000097:blood / Q000235:genetics* / Q000276:immunology*; D005951:Glucose Tolerance Test; D005968:Glutamate Decarboxylase / Q000276:immunology*; D006801:Humans; D007223:Infant; D007330:Insulin Antibodies / Q000097:blood; D007515:Islets of Langerhans / Q000276:immunology; D008875:Middle Aged; D009679:Nuclear Family; D012016:Reference Values
chemical_list: D001323:Autoantibodies; D001786:Blood Glucose; D007330:Insulin Antibodies; C024211:islet cell antibody; D005968:Glutamate Decarboxylase