title: Glutamic acid decarboxylase and ICA512/IA-2 autoantibodies as disease markers and relationship to residual beta-cell function and glycemic control in young type 1 diabetic patients.
abstract: Circulating autoantibodies (Ab) to islet autoantigens, glutamic acid decarboxylase (GAD(65)), and tyrosine phosphatase ICA512/IA-2 have been proposed as predictive markers of type 1 diabetes mellitus. To ascertain residual beta-cell function and the clinical relevance for monitoring autoimmunity after clinical manifestation of disease, we studied 63 children at diagnosis of type 1 diabetes (mean SD age 7.5 +/- 4 years) and 91 adolescent patients with type 1 diabetes (age 14.7 +/- 1.6 years) with a mean duration of disease of 7 +/- 3.5) years. Forty-two normal adolescent subjects (age 14.6 +/- 1.8 years) without a family history of diabetes were the control group. Anti-GAD(65) and ICA512/IA-2 Ab were assessed by a quantitative radioimmunoprecipitation assay. The relationship between humoral autoimmunity and clinical parameters was explored. GAD(65) and ICA512/IA-2 Ab were detected in 56% and 63% of newly diagnosed children and the prevalence was not different in relationship to clinical characteristics. Levels of GAD(65) Ab positively correlated with diagnosis age (P <.05). Both Ab were associated with islet cell antibodies (ICA) (P <.05), but one fifth of patients had at least 1 of the 2 Ab and absent ICA. At onset, only age showed a significant relationship to residual C-peptide secretion. Among the cohort of patients with diabetes of short-mid duration, GAD(65) and ICA512/IA-2 Ab were present in 44% and 45% of cases (P >.05 and P <.05 v newly diagnosed children, respectively) and more patients were identified by these Ab (68%) than by ICA alone (34%) (P <.05). In this cohort, levels of ICA512/IA-2 Ab negatively correlated with levels of glycosylated hemoglobin (HbA(1c)) (P <.005) and with daily insulin requirement (P <.05). Moreover, the presence of some residual C-peptide secretion was significantly associated with the presence of ICA512/IA-2 Ab (P <.05). Our findings confirm that positivity for either GAD(65) or ICA512/IA-2 Ab is a highly sensitive marker of type 1 diabetes in the pediatric age group, identifying a group of patients with absent ICA immunofluorescence. The persistence of Ab to islet tyrosine phosphatase possibly represents a marker of better glycemic control and less insulin requirement, indicating residual beta-cell function, thus conferring clinical and prognostic relevance to these Ab, as well as potential usefulness in intervention strategies.
authors.affiliation: Division of Internal Medicine, University of Torino, Torino, Italy.
authors.forename: M M
authors.initials: MM
authors.lastname: Zanone
authors.forename: E
authors.initials: E
authors.lastname: Catalfamo
authors.forename: S L
authors.initials: SL
authors.lastname: Pietropaolo
authors.forename: I
authors.initials: I
authors.lastname: Rabbone
authors.forename: C
authors.initials: C
authors.lastname: Sacchetti
authors.forename: F
authors.initials: F
authors.lastname: Cerutti
authors.forename: M
authors.initials: M
authors.lastname: Trucco
authors.forename: P
authors.initials: P
authors.lastname: Cavallo-Perin
mesh_terms: D000293:Adolescent; D001323:Autoantibodies / Q000032:analysis*; D001324:Autoantigens; D015415:Biomarkers / Q000032:analysis*; D001786:Blood Glucose / Q000378:metabolism*; D002096:C-Peptide / Q000378:metabolism; D002648:Child; D015331:Cohort Studies; D003922:Diabetes Mellitus, Type 1 / Q000188:drug therapy / Q000276:immunology* / Q000378:metabolism*; D005260:Female; D005968:Glutamate Decarboxylase / Q000276:immunology*; D006442:Glycated Hemoglobin / Q000378:metabolism; D006801:Humans; D007515:Islets of Langerhans / Q000502:physiology*; D007527:Isoenzymes / Q000276:immunology*; D008297:Male; D008565:Membrane Proteins / Q000276:immunology*; D054562:Protein Tyrosine Phosphatase, Non-Receptor Type 1; D017027:Protein Tyrosine Phosphatases / Q000276:immunology*; D011863:Radioimmunoassay; D054635:Receptor-Like Protein Tyrosine Phosphatases, Class 8
chemical_list: D001323:Autoantibodies; D001324:Autoantigens; D015415:Biomarkers; D001786:Blood Glucose; D002096:C-Peptide; D005968:Glutamate Decarboxylase; D006442:Glycated Hemoglobin; D007527:Isoenzymes; D008565:Membrane Proteins; D054562:Protein Tyrosine Phosphatase, Non-Receptor Type 1; D017027:Protein Tyrosine Phosphatases; D054635:Receptor-Like Protein Tyrosine Phosphatases, Class 8; C516862:PTPRN protein, human; C401141:glutamate decarboxylase 2