The prevalence of autoimmune diabetes was assessed in 113 indigenous and 1555 non-indigenous participants in the Fremantle Diabetes Study Phase II. Both type 1 diabetes (3.5% vs. 8.2%) and latent autoimmune diabetes of adults diagnosed based on glutamic acid decarboxylase antibody (GADA) positivity (1.0% vs. 5.7%) were lower in Aboriginal participants (P = 0.101 and 0.039 respectively). Six Aboriginals with GADA-negative type 2 diabetes were positive for tyrosine phosphatase-related islet antigen 2 antibodies but did not exhibit relative insulin deficiency.

Latent autoimmune diabetes in adults (LADA) or slowly progressive insulin-dependent diabetes mellitus (SPIDDM) is a form of autoimmune diabetes characterized by autoimmune destruction of pancreatic beta cells, leading to deficient insulin secretion. Here, we report a case of diabetes and obesity in a 56-year-old woman. She was diagnosed with severe obesity, impaired glucose tolerance (IGT), and a positive antiglutamic acid decarboxylase antibody (GADA) test result at the age of 39 years. She developed diabetes 7 years later, meeting the diagnostic criteria for SPIDDM (probable). Despite high GADA levels, her endogenous insulin secretion has been preserved for over a decade. GADA has been regarded as a marker of autoimmune destruction of pancreatic beta cells, and high levels of GADA are considered a risk factor for future insulin deficiency. However, the role of GADA in its pathogenesis remains unclear. GADA is not a specific indicator of autoimmune diabetes, as it is also positive for autoimmune diseases such as autoimmune thyroid diseases (AITDs) and stiff-person syndrome. Therefore, a positive GADA test alone is not sufficient to predict insulin deficiency in an individual case, even if the titer is high. In the early stages, autoimmune diabetes presents clinical features similar to those of type 2 diabetes, particularly obesity. Although insulin therapy is often started early in the treatment of autoimmune diabetes, as the consensus statement indicates, when endogenous insulin secretion is preserved and the risk of insulin deficiency is low, efforts should be made to prevent body weight gain and the development of cardiovascular diseases (CVD) by following treatment guidelines for type 2 diabetes, with the exception of the use of sulfonylurea agents.

Slowly progressive insulin-dependent (type 1) diabetes mellitus (SPIDDM) is a subtype of type 1 diabetes. Although SPIDDM is not rare among Japanese children, there are few reports on endogenous insulin secretory capacity and anti-pancreatic islet autoantibodies in pediatric SPIDDM. We followed the trends in endogenous insulin secretory capacity and anti-pancreatic islet autoantibody titers in two pediatric SPIDDM cases over several years. Case 1 developed insulin deficiency eight months after diabetes diagnosis; as her insulinoma-associated antibody test result was positive, insulin therapy was initiated. Fourteen months after the diagnosis, she tested positive for glutamic acid decarboxylase autoantibodies (GADA) and was diagnosed with SPIDDM. Case 2 was mildly positive for GADA at the onset of diabetes, but became a high titer during the course of the disease. Fourteen months after the diagnosis of diabetes, he became mildly insulin deficient, and insulin therapy was initiated. However, his insulin secretory capacity was preserved for 60 mo after the onset. SPIDDM is generally indistinguishable from type 2 diabetes at diagnosis; therefore, repeated evaluation of the insulin secretory capacity and anti-islet autoantibodies facilitates early diagnosis and appropriate treatment, especially in nonobese children with type 2 diabetes.

Intravenous immunoglobulins (IVIgs) contain various autoantibodies, including those against glutamic acid decarboxylase (GADAb), a valuable biomarker of type 1 diabetes mellitus. Passive transfer of GADAb from IVIgs to patients poses a risk of misdiagnosis, and information on the specific titres of GADAb and their impact on diagnostic accuracy remains limited. This study aimed to provide further insights into the origin of GADAb detected in patient serum following IVIg infusion.

GADAb titres in IVIg products from Japan and the United States were measured using enzyme-linked immunosorbent assay-based assays. For reliable quantification, GADAb titres in pooled plasma were quantified and compared with those in the IVIg products. The determined titres were used to estimate the likelihood of passively detecting acquired GADAb in individuals receiving IVIgs.

GADAbs were prevalent in IVIg products; however, the titres varied significantly among different lots and products. Importantly, IVIg-derived GADAb was estimated to remain detectable in patient serum for up to 100 days following a dosage of 2000 mg/kg.

Clinicians should consider that IVIg preparations may contain GADAb, which can lead to false-positive results in serological assays. Careful interpretation of the assay results is key to the definitive diagnosis of type 1 diabetes mellitus.

Latent autoimmune diabetes in adults (LADA) is characterized by positive islet-associated autoantibodies including glutamic acid decarboxylase antibody (GADA), and gradual decline in insulin secretion, progressing to insulin dependency. This cross-sectional study aimed to determine whether GADA by enzyme-linked immunosorbent assay (GADA-ELISA) titer of ≥180 U/mL could be associated with decline in β-cell function in participants with LADA.

Sixty-three participants with LADA were recruited and an association between insulin secretion capacity and disease duration was investigated. Insulin peptide-specific inflammatory immunoreactivity was investigated to determine the disease's activity.

There was a significant inverse correlation between disease duration and C-peptide index in participants with GADA-ELISA titer of ≥180 U/mL (Spearman's r (rs) = -0.516, p < 0.01). The positivity rate of insulin peptide-specific inflammatory immunoreactivity was significantly higher in those with ≥180 U/mL than in those with <180 U/mL (p < 0.05). In participants with human leukocyte antigen (HLA)-DRB1*04:05, a significant inverse correlation was observed between disease duration and C-peptide index in those with ≥180 U/mL (rs = -0.751, p < 0.01).

GADA-ELISA titer of ≥180 U/mL, especially with HLA-DRB1*04:05, might reflect higher disease activity and may be associated with decline in β-cell function over time and future insulin dependency in LADA.

This study aimed to identify risk factors that contribute to the progression of slowly-progressive type 1 diabetes by evaluating the positive predictive value (PPV) of factors associated with the progression to an insulin-dependent state.

We selected 60 slowly-progressive type 1 diabetes patients who tested positive for glutamic acid decarboxylase autoantibodies (GADA) at diagnosis from the Japanese Type 1 Diabetes Database Study. GADA levels in these patients were concurrently measured using both radioimmunoassay (RIA) and enzyme-linked immunosorbent assay (ELISA) techniques.

Compared with the non-progressor group (fasting C-peptide [F-CPR] levels maintained ≥0.6 ng/mL), the progressor group showed a younger age at diagnosis, lower body mass index (BMI), lower F-CPR levels and a higher prevalence of insulinoma-associated antigen-2 autoantibodies (IA-2A). The PPV of RIA-GADA increased from 56.3 to 70.0% in the high titer group (≥10 U/mL), and further increased to 76.9, 84.2, 81.0 and 75.0% when combined with specific thresholds for age at diagnosis <47 years, BMI <22.6 kg/m2, F-CPR <1.41 ng/mL and IA-2A positivity, respectively. In contrast, the PPV of ELISA-GADA (71.8%) remained the same at 73.1% in the high titer group (≥180 U/mL), but increased to 81.8, 82.4 and 79.0% when evaluated in conjunction with age at diagnosis, BMI and F-CPR level, respectively.

Our findings show that, unlike RIA-GADA, ELISA-GADA shows no association between GADA titers and the risk of progression to an insulin-dependent state. The PPV improves when age at diagnosis, BMI and F-CPR levels are considered in combination.

In recent years, the emergence of multiplex technology that can simultaneously measure multiple anti-islet autoantibodies has become particularly valuable for the staging and early diagnosis of immune-mediated type 1 diabetes (T1D). While it has been established that 20%-30% of T1D patients suffer from autoimmune thyroid disease (AITD), there is limited available data regarding the presence of anti-islet autoantibodies in AITD patients. Among commercially available anti-islet autoantibodies, glutamic acid decarboxylase 65 autoantibodies (GADAs) are often the first marker measured in general clinical practice.

To investigate the frequency of anti-islet autoantibodies in AITD patients.

Our study involved four hundred ninety-five AITD patients, categorized into three distinct groups: AITD with T1D (n = 18), AITD with phenotypic type 2 diabetes (T2D) (n = 81), and AITD without diabetes (n = 396), and the enzyme-linked immunosorbent assay (ELISA) was employed to determine the frequencies of 3 Screen Islet Cell Autoantibody (3 Screen ICA), GADA, insulinoma-associated antigen-2 autoantibodies (IA-2As), and zinc transporter 8 autoantibodies (ZnT8As) within these groups.

The frequency of 3 Screen ICA in AITD patients with T1D, T2D, and those without diabetes were 88.9%, 6.2%, and 5.1%, respectively, with no significant difference seen between the latter two groups. Notably, the frequency of 3 Screen ICA was 11.1% higher in AITD patients with T1D, 1.3% higher in AITD patients with T2D, and 1.1% higher in AITD patients without diabetes compared to GADA, respectively. Furthermore, 12.5%, 20.0%, and 20.0% of the 3 Screen ICA-positive patients were negative for GADA. Additionally, 1.3% of the AITD patients who tested negative for 3 Screen ICA in both the AITD with T2D and non-diabetic AITD groups were found to be positive for individual autoantibodies. Among the 3 Screen ICA-positive patients, there was a significantly higher proportion of individuals with multiple autoantibodies in AITD patients with T1D compared to those without diabetes (37.5% vs 5.0%, P < 0.05). However, this proportion was similar to that in AITD patients with T2D (20.0%). Nevertheless, there was no significant difference in 3 Screen ICA titers between AITD patients with T1D and those without diabetes (436.8 ± 66.4 vs 308.1 ± 66.4 index). Additionally, no significant difference in 3 Screen ICA titers was observed between Graves' disease and Hashimoto's thyroiditis in any of the groups.

Our findings reveal that some AITD patients without diabetes exhibit 3 Screen ICA titers comparable to those in AITD patients with T1D. Thus, 3 Screen ICA outperforms GADA in identifying latent anti-islet autoantibody-positive individuals among AITD patients.

Recent studies have shown that the quality of life (QOL) of people living with type 1 diabetes (T1D) is poor and must be improved. However, the living situation and QOL of adults living with T1D in Japan have not been fully clarified. This study will examine their lifestyle, QOL, and clinical situation, as well as the relationships between them.

This is a prospective, 5-year follow-up observational study. Between December 2019 and September 2021, we enrolled adults in Japan who were living with T1D and receiving insulin therapy, and are acquiring longitudinal clinical data and the responses to seven questionnaires regarding lifestyle and QOL. The primary study outcomes are (1) the relationship between Problem Areas in Diabetes (PAID) scores and various factors including demographic data, clinical characteristics, medical history, lifestyle habits, treatment history, biochemical data, and the scores of questionnaires; and (2) the relationship between Beck Depression Inventory (BDI)-II scores and various factors aforementioned. The secondary outcomes are the relationships between various factors aforementioned and each of the following: (1) blood glucose control, (2) blood lipid control, (3) dietary patterns, (4) fear of hypoglycemia, (5) sleep patterns, and (6) physical activity.

We registered 352 participants. The median age was 49 (41-63) years, and the median duration of T1D was 13 (8-20) years. All the results will be available in 2026. We expect to clarify the factors associated with decreased QOL, and that this knowledge will contribute to improving QOL in adults in Japan who are living with T1D and receiving insulin therapy.

Clinical Trials.gov identifier, UMIN000044088.

Autoantibodies directed against the 65-kilodalton isoform of glutamic acid decarboxylase (GAD65Abs) are markers of autoimmune type 1 diabetes (T1D) but are also present in patients with Latent Autoimmune Diabetes of Adults and autoimmune neuromuscular diseases, and also in healthy individuals. Phenotypic differences between these conditions are reflected in epitope-specific GAD65Abs and anti-idiotypic antibodies (anti-Id) against GAD65Abs. We previously reported that 7.8% of T2D patients in the GRADE study have GAD65Abs but found that GAD65Ab positivity was not correlated with beta-cell function, glycated hemoglobin (HbA1c), or fasting glucose levels.

In this study, we aimed to better characterize islet autoantibodies in this T2D cohort. This is an ancillary study to NCT01794143.

We stringently defined GAD65Ab positivity with a competition assay, analyzed GAD65Ab-specific epitopes, and measured GAD65Ab-specific anti-Id in serum.

Competition assays confirmed that 5.9% of the patients were GAD65Ab positive, but beta-cell function was not associated with GAD65Ab positivity, GAD65Ab epitope specificity or GAD65Ab-specific anti-Id. GAD65-related autoantibody responses in GRADE T2D patients resemble profiles in healthy individuals (low GAD65Ab titers, presence of a single autoantibody, lack of a distinct epitope pattern, and presence of anti-Id to diabetes-associated GAD65Ab). In this T2D cohort, GAD65Ab positivity is likely unrelated to the pathogenesis of beta-cell dysfunction.

Evidence for islet autoimmunity in the pathophysiology of T2D beta-cell dysfunction is growing, but T1D-associated autoantibodies may not accurately reflect the nature of their autoimmune process.