ABSTRACT
Antibodies directed against the enzyme glutamic acid decarboxylase [GAD] are believed to be the main cause of destruction of pancreatic islet cells in type I [insulin dependent] diabetes mellitus. The enzyme was found both in the brain and pancreatic beta cells. Although similarities in identity of GAD in human and rat brain have been demonstrated, little is known about the interaction between the enzyme and antiserum in type 1 diabetic patients. In the present study GAD was partially purified from rat brain homogenate. The four-step procedure involves, sequentially, an ultracentrifugation, DEAE-cellulose, hydroxyapatite resin, and Sephadex G-200 gel filtration chromatography. The enzyme activity was assayed either manometrically or fluorimetrically. The results showed a positive correlation between the rates of CO[2] production with the changes of fluorescence intensities of the enzyme after addition of glutamate. The collected fraction from the gel filtration chromatography showed approximately 140-fold purification of the enzyme with a 15% yield. The specific activity of the enzyme of brain supernatant and the partially purified enzyme collected from every chromatographic step was measured upon addition of the serum samples from type I diabetes [n= 11]. A marked decrease in the rate of CO[2] production or the change of fluorescence intensities of the enzyme was observed, indicating an interaction between the enzyme and the patients' sera. However, serum samples from healthy control individuals had little effect on the enzyme activity of the partially purified GAD. The results suggested that rat brain GAD might be used as an in vitro reagent for screening of type I diabetes, using an enzyme inhibition assay
Subject(s)
Humans , Glutamic Acid/immunology , Antibodies , Diabetes Mellitus, Type 1/etiologyABSTRACT
Background: Islet cell-specific autoantibodies such as islet cell antibody (ICA), antiinsulin (IAA), anti-glutamic acid decarboxylase (GAD) and anti-tyrosine phosphatase (IA2) can be present in patients with type I diabetes. Breast feeding duration and the early exposure to milk substitutes are environmental factors associated to etiology of type 1 diabetes. Aim To study the frequency of the anti-GAD, anti-IA-2 e ICA antibodies in Chilean type 1 diabetic patients and determine the possible modulator effect of the breast feeding. Patients and methods: One hundred thirty four type I diabetic patients, aged one to 15 years old, were studied at the moment of their diagnosis. Patients were classified according to the duration of exclusive breast feeding. IA-2 and GAD were determined by radio immuno assay and ICA by means of indirect immunofluorescence. Results: Subjects with three months or less and those with more than three months of breast feeding were positive for ICA in 78.8 and 90.6 per cent of cases respectively, for GAD in 75 and 54.6 per cent of cases respectively (p=0.024) and for IA-2 in 73 and 43.8 per cent of cases respectively (p=0.001). All three antibodies were positive in 53.9 and 21.8 per cent of children with less or more than three months of breast feeding (p=0.001). Conclusion: Both IA-2 and GAD antibodies are less frequently positive in type 1 diabetic patients who have been breast fed for more than three months. These findings suggest a possible attenuating role of exclusive breast feeding on pancreatic aggression events in patients with type 1 diabetes
Subject(s)
Humans , Child, Preschool , Infant , Child , Male , Female , Autoantibodies/immunology , Breast Feeding , Diabetes Mellitus, Type 1/immunology , Autoimmunity/immunology , Islets of Langerhans/immunology , Glutamic Acid/immunology , Insulin Antibodies/immunology , Protein Tyrosine Phosphatases/immunologyABSTRACT
Objetivo. Conocer la frecuencia de autoanticuerpos a la descarboxilasa del ácido glutámico (GAD) en niños mexicanos con diabetes mellitus tipo 1 (DM 1) por un método de radioligando (RBA). Material y métodos. Se determinaron anticuerpos a GAD en 140 niños mestizos con DM 1, 66 niñas (47.14 por ciento) y 74 niños (52.8 por ciento), con promedio de 11.7 ñ 3.55 años, entre 1.10 a 18.5 años de edad. Todos estaban en tratamiento con insulina de acción intermedia y algunos de ellos con combinación de insulina de acción rápida. El promedio de la evolución del padecimiento fue de 3.11 ñ 2.94 años, entre un mes a 14.5 años. Previo consentimiento informado se tomó la muestra de 5.0 mL de sangre, que se centrifugó de inmediato y el suero se conservó congelado a -20º C hasta su procesamiento por un equipo comercial de RBA. Resultados. Los anticuerpos a GAD resultaron positivos en 76 pacientes con DM 1 (54.28 por ciento) con valores entre 1.11 a 156.73 U/mL y negativos en 64 (45.71 por ciento). En 19 pacientes con anticuerpos a GAD positivos, se repitió la misma determinación y los valores se encontraron entre 1.38 a 156.62 U/mL. En un grupo control inicial de 25 voluntarios no relacionados, igualados en edad y sexo, la determinación de los anticuerpos fue negativa en todos ellos. Conclusiones. La frecuencia de anticuerpos a GAD en estos pacientes fue inferior a la informada en pacientes europeos con DM 1, pero semejante a la de asiáticos. Estos resultados apoyan la heterogeneidad de la etiopatogenia de la DM 1 en diferentes grupos étnicos.
Subject(s)
Humans , Male , Female , Infant , Child, Preschool , Adolescent , Glutamic Acid/immunology , Antibodies/analysis , Child , Diabetes Mellitus, Type 1/immunology , Mexico/epidemiology , Diabetes Mellitus/physiopathology , Glutamate Decarboxylase/immunologyABSTRACT
Insulin dependent diabetes mellitus [IDDM] is an autoimmune disease, the factors that induce the selective destruction of the insulin producing islet cells of the pancreas are unknown. Although autoreactive T-cells rather than autoantibodies are responsible for the destruction of beta-cells, the identification and chararcterization of the autoantibody-autoantigen system in IDOM are of crucial and fundamental importance in prediction and potential immunotherapy of the disease. Currently, Cytoplasmic Islets Cell Antibodies [ICAs Insulin Autoantibodies [IAA], Glutamic Acid Decarboxylase Antibodies [Anti-GADs] and 37-k antigen antibodies are potentially useful hurnoral markers for such prediction. The attempt to identify the earliest events in the autoimmune process suggest that Anti-GAD could be the first and most important autoantigen