Relationship between the prevalence of anti-glutamic acid decarboxylase autoantibodies and duration of type 1 diabetes mellitus in Brazilian patients

Persistence of islet autoantibodies after diagnosis in type 1 diabetes

The presence of islet autoantibodies remains a reliable biomarker to identify individuals at high risk of developing type 1 diabetes. As such, these autoantibodies play a pivotal role in understanding the prodrome of diabetes and selecting individuals for both prevention and intervention clinical trials. Over the last few decades, studies have sought to investigate autoantibody prevalence after diabetes onset to better understand ongoing islet autoimmunity; however, many findings are contradictory, and little is known about factors that may influence autoantibody persistence. Generally, glutamate decarboxylase autoantibodies (GADAs) are the most prevalent autoantibodies after diagnosis, particularly in adults, whilst zinc transporter 8 autoantibodies (ZnT8A) prevalence declines more rapidly. However, when studies with islet autoantibody data at diagnosis are considered, it becomes clear that overall islet antigen-2 autoantibodies (IA-2A) tend to persist for longer than GADA or ZnT8A. In this review, we assess the major studies that have contributed to our understanding of autoantibody persistence after diabetes onset and what factors affect this. Islet autoantibodies may provide biomarkers for long-term β-cell function and insights into how to prevent ongoing islet autoimmunity but larger studies collecting samples at and decades after diabetes onset are required to leverage the information they could provide.

Association of type 1 diabetes mellitus and autoimmune disorders in Brazilian children and adolescents

CONTEXT

Type 1 diabetes mellitus (T1DM) is caused by an immune-mediated destruction of pancreatic beta cells. Other autoimmune diseases can be observed in association with T1DM. The screening for celiac disease (CD) and Hashimoto's thyroiditis is necessary due to the increased prevalence of these pathologies in T1DM patients.

AIMS

This study aimed to investigate the prevalence of autoimmune markers for pancreatitis, thyroiditis, and CD in racially admixtured children and adolescents with T1DM.

SETTINGS AND DESIGN

Cross-sectional clinic-based study.

METHODS

Seventy-one patients with T1DM (average: 11.6 ± 5.1 years). In all patients, the following antibodies were surveyed: Anti-glutamic acid decarboxylase (anti-GAD), immunoglobulin A (IgA) anti-transglutaminase (anti-tTG), Antithyroglobulin (AAT), anti-thyroid peroxidase (anti-TPO), and IgA.

STATISTICAL ANALYSIS USED

The quantitative variables were expressed as a mean and standard deviation and the qualitative variables in contingency tables. Student's t-test and χ(2) tests were used to assess the differences between the groups. The level of significance was established as P < 0.05.

RESULTS

The prevalence of anti-GAD antibodies was 5.9%; anti-tTG IgA, 7.4%; anti-TPO, 11.8%; and AAT, 11.8%.

CONCLUSIONS

Children and adolescents with T1DM have increased the prevalence of antithyroid and CD-related antibodies. The positivity for anti-GAD and antithyroid antibodies was less frequent than in other studies. The prevalence of anti-tTG antibodies was similar to the literature.

Influence of age at diagnosis and duration of diabetes on the positivity of glutamic acid decarboxylase antibody in South-Brazilian type 1 diabetes mellitus

Aim

To evaluate the influence of age of onset and duration of diabetes on the positivity of glutamic acid decarboxylase antibody (GADA) in South-Brazilian type 1 diabetes mellitus (DM) patients.

Methods

GADA was evaluated in 92 patients with type 1 diabetes, in 147 gestational DM patients, and in 59 subjects with normal glucose tolerance.

Results

Type 1 patients with positive GADA ( N = 44, 48%) were older at the onset of diabetes (22 ± 9 versus 18 ± 10 y, P = 0.043) and had a shorter DM duration (12 ± 8 versus 19 ± 9 y, P < 0.001), as compared with negative GADA patients. A logistic regression with antibody positivity as the dependent variable and diabetes duration as the independent variable, showed that the shorter diabetes duration was related to the presence of the antibody with an odds ratio (OR) = 5.6; (CI 95% = 2.1–14.6); P < 0.001. Another model, with age at diagnosis as the independent variable, did not show any association with antibody positivity. However, analysing only men, a shorter DM duration (OR = 6.5; CI = 1.7–24.0; P = 0.006), and also a higher age at diagnosis (OR = 5.5; CI = 1.5–21.0; P = 0.01) were significantly related to the antibody positivity. The performance of GADA was similar in up to 15 y of duration of DM ( P = 0.78), but significantly diminished with higher duration ( P = 0.001).

Conclusion

GADA testing is a helpful tool in the diagnosis of type 1 DM starting in young adults and older individuals. Even though the positivity rate declines along the course of disease, it still provides useful information up to 15 y after the diabetes diagnosis.

Residual C-peptide in patients with Type 1 diabetes and multiethnic backgrounds

OBJECTIVE

To evaluate serum C-peptide in 88 patients from a multiethnic population with Type-1 diabetes and variable disease durations.

METHOD

Eighty-eight patients with a mean disease duration of 8.1 +7.6 years were included and underwent C-peptide measurement before and after glucagon stimulation. Chi-squared and Mann Whitney U-tests were used to compare the variables between groups (all two-tailed, α = 0.05). Spearmans correlation coefficient was used to test the association between the continuous variables. Logistic regression was used for the multivariate analysis. Twenty-eight (31.8%) individuals had significantly detectable C-peptide levels after stimuli, particularly those with a shorter disease duration (p<0.001).

RESULTS

Patients with detectable C-peptide levels required lower insulin doses (p<0.009) and had similar HbA1C results (p = 0.182) and fewer chronic complications (p = 0.029).

CONCLUSION

C-peptide detection was common in Type-1 diabetics, particularly shortly after being diagnosed. This result may have clinical implications.

Macroscopic placental changes associated with fetal and maternal events in diabetes mellitus

OBJECTIVES

The current study sought to identify macroscopic placental changes associated with clinical conditions in women with or without diabetes and their newborns.

METHODS

The study population consisted of 62 pregnant women clinically diagnosed with diabetes and 62 healthy women (control group).

RESULTS

Among the subjects with diabetes, 43 women (69.3%) were diagnosed with gestational diabetes mellitus, 15 had diabetes mellitus I (24.2%), and four had diabetes mellitus II (6.5%). The mean age of the women studied was 28.5 ± 5.71 years, and the mean gestational age of the diabetic women was 38.51 weeks. Of the 62 placentas from diabetic pregnancies, 49 (79%) maternal surfaces and 59 (95.2%) fetal surfaces showed abnormalities, including calcium and fibrin deposits, placental infarction, hematoma, and fibrosis. A statistical association was found between newborn gender and fetal and maternal placental changes (p = 0.002). The mean weight of the newborns studied was 3,287 ± 563 g for women with diabetes mellitus, 3,205 ± 544 g for those with gestational diabetes mellitus, 3,563 ± 696 g for those with diabetes mellitus II, and 3,095 ± 451 g for those with diabetes mellitus I.

CONCLUSIONS

Infarction, hematoma, calcification, and fibrin were found on the maternal and fetal placental surfaces in women with diabetes. Women with gestational diabetes and post-term infants had more calcium deposits on the maternal placental surface as compared to those with type I and type II diabetes.

Frequency of the anti-glutamic acid decarboxylase immunological marker in patients with diabetes duration longer than three years in southern Brazil

CONTEXT AND OBJECTIVE

The anti-GAD (glutamic acid decarboxylase) antibody is considered to be an important marker for type 1 diabetes mellitus (DM1), with frequency that varies depending on the population studied and the duration of the disease. Therefore, the aim of this study was to determine the frequency of this autoantibody in a group of patients in southern Brazil with DM1 that had been diagnosed more than three years previously.

DESIGN AND SETTING

Analytical cross-sectional study with a control group conducted at the Biomedicine Laboratory of Universidade Feevale.

METHODS

This study was conducted between June 2007 and December 2008, and 109 individuals were enrolled during this period. Fifty-eight were DM1 patients and 51 were individuals free from DM1 and without any history of diabetes, who constituted the control group.

RESULTS

In the DM1 group, the mean age was 27 ± 1.7 years and 50% were men. The mean fasting blood glucose in the DM1 group was 208 ± 15 mg/dl and mean HbA1c (glycosylated hemoglobin) was 8.7 ± 0.25%. In the control group, the mean fasting blood glucose and HbA1c were 82 mg/dl and 5.0% respectively. Thirty-seven individuals with DM1 (63.8%) were positive for anti-GAD, and this proportion was significantly larger than in the control group.

CONCLUSIONS

These results show the high prevalence of anti-GAD in the population of diabetic patients in southern Brazil, thus indicating that the antibody was still present a long time after the disease had been diagnosed.

Avaliação da função pancreática em pacientes com diabetes melito tipo 1 de acordo com a duração da doença

Os pacientes com diabetes melito tipo 1 (DM1) podem apresentar secreção residual de insulina por longos períodos, o que tem sido associado a prognóstico mais favorável. OBJETIVO: Avaliar a secreção de insulina por meio da dosagem de peptídeo C (PC) em pacientes com DM1 de curta (<5 anos; grupo 1) e longa (> 5 anos; grupo 2) duração da doença. PACIENTES E MÉTODOS: Voluntários com DM1 coletaram sangue em jejum e 6 minutos após a infusão de glucagon para dosagem de PC, HbA1c e anti-GAD. RESULTADOS: Foram avaliados 43 pacientes, 22 no grupo 1 e 21 no grupo 2. Secreção de insulina preservada (PC > 1,5 ng/mL) foi identificada em seis (13,9%) e oito (18,6%) casos nas coletas basal (PC1) e após estímulo (PC2), sem diferença entre os grupos (p = 0,18 e 0,24). PC1 foi detectável (> 0,5 ng/mL) em 13 (30,2%) e PC2 em 18 (41,9%) casos, mais frequentes no grupo 1 do que no 2 (p = 0,045 para PC1/p = 0,001 para PC2). Os títulos de PC1 (1,4 ±0,8 versus 1,2 ±1,0; p = 0,69) ou PC2 (1,8 ±1,5 versus 1,7 ±0,8; p = 0,91) não diferiram entre os grupos. No grupo 1 houve correlação inversa entre tempo de doença e PC2 (R = -0,58; p = 0,025). CONCLUSÃO: Uma proporção significativa dos pacientes com DM1 apresenta secreção residual de insulina, especialmente nos primeiros cinco anos da doença. Tais indivíduos representam a população ideal para estudos visando à prevenção secundária da doença.