Association of Autoimmune Thyroid Disease with Anti-GAD Antibody ELISA Test Positivity and Risk for Insulin Deficiency in Slowly Progressive Type 1 Diabetes

Study of an Ultrasensitive Label-Free Electrochemiluminescent Immunosensor Fabricated with a Composite Electrode for Detecting the Glutamate Decarboxylase Antibody

Antibody testing for the glutamic acid decarboxylase 65 antibody (GADA) is widely used as a golden standard for autoimmune diabetes diagnosis, while current methods for antibody testing are not sensitive enough for clinical usage. Here, a label-free electrochemiluminescent (ECL) immunosensor for detecting GADA in autoimmune diabetes is fabricated and investigated. In the designed immunosensor, a composite film including the multiwalled carbon nanotubes (MWCNTs), zinc oxide (ZnO), and Au nanoparticles (AuNPs) was prepared through nanofabrication processes to improve the performance of sensor. The MWCNTs, which can provide a larger specific surface area, ZnO as a good photocatalytic material, and AuNPs that can enhance the ECL signal of luminol and immobilize the GAD65 antigen were applied to prefunctionalize indium tin oxide (ITO) glass based on a nanofabrication process. The GADA concentration was detected using the ECL immunosensor after incubating with GAD65 antigen-coated prefunctionalized ITO glass. After a direct immunoreaction, it is found that the degree of decreased ECL intensity has a good linear regression toward the logarithm of the GADA concentration in the range of 0.01 to 50 ng mL^-1 with a detection limit down to 10 pg mL^-1. Human serum samples positive or negative for GADA all nicely fell in the expected area. The fabricated immunosensor with excellent sensitivity, specificity, and stability has potential capability for clinical usage in GADA detection.

Checking the Checkpoint Inhibitors: A Case of Autoimmune Diabetes After PD-1 Inhibition in a Patient with HIV

Immune checkpoint inhibitor-associated diabetes mellitus (ICI-DM) is a known immune-related adverse event (irAE) following treatment with programmed cell death protein 1 (PD-1), with a reported 0.9% incidence. We hereby present the first case, to our knowledge, of ICI-DM following ICI use in a human immunodeficiency virus (HIV) patient. In this case, a 48-year-old man with HIV stable on highly active antiretroviral therapy (HAART) was diagnosed with Hodgkin lymphoma and initiated treatment with the PD-1 inhibitor nivolumab. His lymphoma achieved complete response after 5 months. However, at month 8, he reported sudden polydipsia and polyuria. Labs revealed a glucose level of 764 mg/dL and glycated hemoglobin A1c (HbA1c) of 7.1%. Low C-peptide and elevated glutamic acid decarboxylase 65 (GAD65) antibody levels confirmed autoimmune DM, and he was started on insulin. Major histocompatibility complex class II genetic analysis revealed homozygous HLA DRB1*03-DQA1*0501-DQB1*02 (DR3-DQ2), which is a known primary driver of genetic susceptibility to type 1 DM. Autoimmune DM has been reported as an ICI-associated irAE. However, patients with immunocompromising conditions such as HIV are usually excluded from ICI trials. Therefore, little is known about such irAEs in this population. In this case, risk of ICI-DM as an irAE was likely increased by several factors including family history, a high-risk genetic profile, islet-related immunologic abnormalities, active lymphoma, and HIV infection with a possible immune reconstitution event. Clinicians should maintain a high index of suspicion for development of irAEs associated with ICI, particularly as use of these therapies broadens. Thorough investigation for presence of higher-risk features should be conducted and may warrant inclusion of pre-therapy genetic and/or autoantibody screening.

Characterization of patients with diabetes who were incidentally found to be glutamic acid decarboxylase autoantibody-positive by bridging-type enzyme-linked immunosorbent assay

This study aimed to characterize diabetic patients incidentally found to be positive for glutamic acid decarboxylase autoantibodies (GADA) in general practice. Using bridging‐type enzyme‐linked immunosorbent assay, we screened 1,040 patients with phenotypic type 2 diabetes for GADA, finding 25 (2.4%) to be positive. However, on retesting, with a median interval of 19 days, 44% of GADA‐positive patients turned negative (Disappearing Group). The mean age at diabetes onset was significantly higher (P < 0.05) and GADA titers at first determination were significantly lower (P < 0.001) in the Disappearing Group compared with the Persistent Positive Group. On initial screening, all patients in the Disappearing Group had GADA titers of <6.5 U/mL. The current study showed that a portion of phenotypic type 2 diabetic patients incidentally identified as GADA‐positive were falsely positive, and that to avoid the misclassification, remeasurement of GADA is essential in cases showing very low titers.

Exogenous Insulin Injection-Induced Stiff-Person Syndrome in a Patient With Latent Autoimmune Diabetes: A Case Report and Literature Review

Stiff-person syndrome (SPS) is highly associated with anti-glutamic acid decarboxylase (GAD) antibody. However, GAD antibodies alone appear to be insufficient to cause SPS, and they possibly are involved in only part of its pathophysiology. It is suspected that the symptoms of SPS get precipitated by external stimuli. Here, we briefly introduce the case of a patient with latent autoimmune diabetes who developed SPS through the action of subcutaneously injected insulin. A 43-year-old man was diagnosed with diabetes and initially well-controlled with oral hypoglycemic agents but progressed to requiring insulin within 1 year of diagnosis. Two months after the initiation of basal insulin therapy, he presented with abdominal stiffness and painful muscle spasms, involving the lower limbs, which resulted in walking difficulty, and thus, he refused insulin injections thereafter. He had been treated with oral anti-diabetic agents instead of insulin for 10 years until premixed insulin twice daily was started again due to poor diabetes control. Immediately after insulin injection, abdominal muscle rigidity and spasms were noted. When insulin was not administered, frequent episodes of diabetic ketoacidosis occurred. Serum GAD antibody test was positive and there was no positivity for islet antigen-2 antibody. A glucagon stimulation test demonstrated relative insulin deficiency, indicative of latent autoimmune diabetes in adults (LADA). Tolerable muscle rigidity was achieved when the dosage of basal insulin was split into two separate daily injections with lower amounts of units per injection. This case highlights a different form of autoimmune diabetes in SPS. To our knowledge, this is the first report of SPS described shortly after the initiation of insulin therapy that required basal insulin to achieve tolerable muscle symptoms and better glucose control, without the development of diabetic ketoacidosis.

Association of stiff-person syndrome with autoimmune endocrine diseases

BACKGROUND

Stiff-person syndrome (SPS) and its subtype, stiff limb syndrome (SLS), are rare neurological disorders characterized by progressive muscular rigidity and spasms. Glutamic acid decarboxylase (GAD) is the enzyme that catalyzes the production of γ-aminobutyric acid (GABA), a major inhibitory neurotransmitter of the central nervous system. SPS is an autoimmune disease triggered by anti-glutamic acid decarboxylase antibody (anti-GAD Ab). Clinically, anti-GAD Ab is associated with SPS, type 1 diabetes mellitus (T1DM), and other autoimmune diseases.

AIM

To investigate the link of autoimmune endocrine disorders with anti-GAD Ab in SPS subjects.

METHODS

This retrospective study was approved by the Institutional Review Board of Chang Gung Memorial Hospital, Taiwan. We collected the patients with SPS from January 2001 to June 2018. By reviewing 14 patients from medical records, we analyzed the clinical findings with coexisting autoimmune diseases, particularly diabetes mellitus and thyroid disease, which are associated with anti-GAD antibody titers or other immunological test results (anti-thyroid peroxidase and anti-nuclear antibodies). We also evaluated malignancies, major complications, and reported treatment to improve symptoms. Anti-GAD antibodies were measured using radioimmunoassay and enzyme-linked immunosorbent assay (ELISA). The cut-off values of these tests are < 1 U/mL and < 5 U/mL, respectively.

RESULTS

The median age of all patients was 39.3 (range, 28.0-54.0) years with a median follow-up period of 6.0 (2.7-13.3) years. Five (35.7%) patients were female; twelve (85.7%) were diagnosed with classic SPS and two (14.3%) with SLS. The median age of onset of symptoms was 35.0 (26.0-56.0) years with a median follow-up duration of 9.0 (2.1-14.9) years in the classic SPS group; the SLS group had a median age of onset of 46.7 years and a shorter follow-up duration of 4.3 years. Among nine classic SPS patients who underwent the anti-GAD Ab test, three were anti-GAD Ab seropositive and each of these three patients also had T1DM, latent autoimmune diabetes in adults, and autoimmune thyroid disease, respectively. In contrast, other rare autoimmune diseases co-existed in six anti-GAD Ab seronegative SPS patients. None of the SLS patients had additional autoimmune diseases.

CONCLUSION

While typical clinical symptoms are crucial for the diagnosis of SPS, the presence of anti-GAD autoantibody may consolidate the diagnosis and predict the association with other autoimmune diseases.

Circulating anti-glutamic acid decarboxylase-65 antibody titers are positively associated with the capacity of insulin secretion in acute-onset type 1 diabetes with short duration in a Japanese population

Aims/Introduction

To elucidate the relationship between titers of islet autoantibodies, the C‐X‐C motif chemokine 10 – a circulating chemokine that activates T‐helper 1 cells leading to β‐cell destruction – and β‐cell function in type 1 diabetes.

Materials and Methods

In total, 58 type 1 diabetes patients positive for glutamic decarboxylase‐65 autoantibodies (GADA)‐radioimmunoassay (mean age 54.1 years; 27 acute‐onset cases and 31 slowly progressive cases) were enrolled; serum C‐X‐C motif chemokine 10 (n = 50), zinc transporter 8 autoantibodies (n = 50) and GADA (n = 58) by an enzyme‐linked immunosorbent assay, and insulinoma‐associated antigen‐2 autoantibodies by radioimmunoassay (n = 50) were measured. The ratio of 100 × random C‐peptide (ng/mL)‐to‐plasma glucose levels (mg/dL; C‐peptide index [CPI]) was measured.

Results

The CPI significantly decreased in both groups with the progression of disease duration. GADA titers by radioimmunoassay and enzyme‐linked immunosorbent assay were strongly correlated with the CPI in acute‐onset type 1 diabetes patients with a shorter disease duration (≤10 years), but not in those with a longer duration or slowly progressive type 1 diabetes. Neither insulinoma‐associated antigen‐2 nor zinc transporter 8 autoantibodies titers were correlated with the CPI. Serum C‐X‐C motif chemokine 10 levels in both groups were significantly higher than in non‐diabetic controls, and persisted at high levels even in those with chronic duration.

Conclusions

Among islet autoantibodies, the intensity of the humoral immune response, as defined by GADA titers, reflected the degree of residual β‐cell function in acute‐onset type 1 diabetes patients with short duration. Prolonged disease activity might accelerate β‐cell impairment in both subtypes of type 1 diabetes.