Positive autoantibodies to ZnT8 indicate elevated risk for additional autoimmune conditions in patients with Addison's disease

SJ, Pittock SJ, Pittock ST. Clinical Utility and Outcome Prediction of Early ZnT8-IgG Testing and Titer in Type 1 Diabetes

OBJECTIVE

Type 1 diabetes autoantibodies are directed against multiple antigens including: glutamic acid decarboxylase, protein tyrosine phosphatase-like islet antigen 2 (IA2), insulin (IAA), and Zinc transporter 8 protein (ZnT8). The aim of our study was to determine if the presence or titer of ZnT8 antibodies (Ab) was predictive for clinical presentation at diagnosis or for the subsequent disease course.

METHODS

Between January, 2003 and May, 2019, 105 patients aged ≤21 years with a clinical diagnosis of type 1 diabetes mellitus had at least 1 autoantibody measured. A retrospective chart review was completed. At diagnosis, we evaluated the body mass index z-score, hemoglobin (HbA1c), and the presence of diabetic ketoacidosis (DKA). Complications analyzed post-diagnosis included episodes of DKA, the diagnosis of autoimmune disease, and the presence of vascular complications. We evaluated cumulative lifetime excess glucose as HbA1c area under the curve (AUC) >6%.

RESULTS

Seventy-one patients were ZnT8-Ab(+) (68%), with 19 having low titer ZnT8-Ab and 52 with high titer ZnT8-Ab. Follow-up ranged from 10 days to 15.7 years (median 2.08 years). There were no differences in the characteristics at disease onset or in the subsequent follow-up between those with and those without ZnT8-Ab or those with high or low titers of ZnT8 Ab, except for a small but statistically significant difference in cumulative excess glucose (HbA1c AUC >6%) between those with low and high titers (p=0.0095).

CONCLUSION

Our study adds to the limited literature on the effect of the presence and titer of ZnT8-Ab in pediatric diabetes. The small effect of ZnT8-Ab titer on glucose excess as measured by HbA1c AUC warrants further study.

Association between islet autoantibodies and the prevalence of autoimmune uveitis

AIM

To evaluate the predictive value of islet autoantibodies for the diagnosis of autoimmune uveitis (AU), as well as to characterize the association bet ween islet autoantibodies and AU.

METHODS

Totally 97 patients with AU and 100 healthy persons without any autoimmune diseases as the control group were recruited. Multiple serum islet autoantibodies were measured using commercial enzyme-linked immunosorbent assay kits (ELISA). A supplementary questionnaire was used to complement the subject's demographics and clinical features. The level of glucose concentrations and white blood cells were measured. Conditional logistic regression was performed to estimate odds ratios (ORs), and 95% confidence intervals (CIs) of AU according to islet autoantibodies and to evaluate the predictive value of islet autoantibodies for AU diagnosis. Autoantibodies subgroups and other variables were included into analysis.

RESULTS

In AU patients, the prevalence of detecting at least one of the autoantibodies was 31.9% (31/97). The most frequent autoantibody was ZnT8A (30.9%), followed by GADA (11.3%), IA-2A (4.1%), ICA (2.1%) and IAA (2.1%). Islet autoantibodies were found to be correlated positively with AU diagnosis [OR (95%CI): 13.86 (3.28, 58.50), P<0.001]. Moreover, Zn-T8A was remarkably correlated with AU diagnosis [OR (95%CI): 6.13 (1.96, 19.17), P<0.001], In contrast, neither GADA nor other islet antibodies (IA-2A, ICA and IAA) showed any association with AU risk under an additive model.

CONCLUSION

The prevalence of islet antibodies, especially ZnT8A, in patients with AU is higher. Islet antibodies as well as novel biomarkers should be included in routine evaluation at AU and is a valuable biological marker to classify newly-diagnosed uveitis.

Anti-ZnT8 autoantibodies: A new marker to be screened in patients with anti-adrenal antibodies

Patients with autoimmune Addison's disease (AAD) can develop other autoimmune diseases. They often display autoantibodies other than anti-adrenal cortex autoantibodies (ACA) which could be of interest in predicting the development of other diseases such as type 1 diabetes (T1D). Among the well-established autoantibodies associated with T1D, anti-ZnT8 autoantibodies (ZnT8A) could be found in absence of anti-GADA and anti-IA2A. Thus, the aim of our study was to evaluate the prevalence of ZnT8A in a cohort of AAD patients. The presence of ZnT8A was studied in 36 patients (19 children and 17 adults) displaying ACA. ZnT8A were detected in both children and adults with an overall prevalence of 19%. The results also indicated that ZnT8A were associated with coexisting T1D in more than 70% of this population regardless of age. Even if the titer of ZnT8A for the one third of patients without T1D was low, they have to be followed due to the potential risk of developing T1D. ZnT8A in those cases could also be a marker of autoimmunity associated to the adrenal gland destruction in AAD. As ZnT8A screening has been included in the diagnostic investigation of T1D, it should also be incorporated in the autoantibodies screening panel of the AAD population.

Every Fifth Individual With Type 1 Diabetes Suffers From an Additional Autoimmune Disease: A Finnish Nationwide Study

OBJECTIVE

The aim of this study was to quantify the excess risk of autoimmune hypothyroidism and hyperthyroidism, Addison disease, celiac disease, and atrophic gastritis in adults with type 1 diabetes (T1D) compared with nondiabetic individuals in Finland.

RESEARCH DESIGN AND METHODS

The study included 4,758 individuals with T1D from the Finnish Diabetic Nephropathy (FinnDiane) Study and 12,710 nondiabetic control individuals. The autoimmune diseases (ADs) were identified by linking the data with the Finnish nationwide health registries from 1970 to 2015.

RESULTS

The median age of the FinnDiane individuals at the end of follow-up in 2015 was 51.4 (interquartile range 42.6-60.1) years, and the median duration of diabetes was 35.5 (26.5-44.0) years. Of individuals with T1D, 22.8% had at least one additional AD, which included 31.6% of women and 14.9% of men. The odds ratios for hypothyroidism, hyperthyroidism, celiac disease, Addison disease, and atrophic gastritis were 3.43 (95% CI 3.09-3.81), 2.98 (2.27-3.90), 4.64 (3.71-5.81), 24.13 (5.60-104.03), and 5.08 (3.15-8.18), respectively, in the individuals with T1D compared with the control individuals. The corresponding ORs for women compared with men were 2.96 (2.53-3.47), 2.83 (1.87-4.28), 1.52 (1.15-2.02), 2.22 (0.83-5.91), and 1.36 (0.77-2.39), respectively, in individuals with T1D. Late onset of T1D and aging increased the risk of hypothyroidism, whereas young age at onset of T1D increased the risk of celiac disease.

CONCLUSIONS

This is one of the largest studies quantifying the risk of coexisting AD in adult individuals with T1D in the country with the highest incidence of T1D in the world. The results highlight the importance of continuous screening for other ADs in individuals with T1D.

Autoantibodies against ZnT8 are rare in Central-European LADA patients and absent in MODY patients, including those positive for other autoantibodies

BACKGROUND

Testing for autoantibodies against the zinc transporter ZnT8 (ZnTA) is becoming routine in pediatric diabetes. However, available data are inconclusive when focusing on adult-onset diabetes, including autoimmune diabetes, which does not require insulin at diagnosis (LADA).

BASIC PROCEDURES

We examined the ZnTA prevalence and titers and matched them with the clinical phenotype and PTPN22 genotypes of Czech LADA patients who were positive for GADA and/or IA2A and had a fasting C-peptide level >200 pmol/L at diagnosis as well as HNF4A-, GCK- or HNF1A-MODY patients and healthy controls.

MAIN FINDINGS

Most LADA patients were negative for ZnTA, and the sensitivity of the assay was only 18-20% for patients with LADA-like progression to insulinotherapy compared to healthy controls. In LADA patients, there was no association between the ZnTA and PTPN22 risk genotypes. LADA patients positive for ZnTA had a lower BMI than those positive for other autoantibodies alone. Importantly, MODY patients were completely negative for ZnTA, and the levels of ZnTA in MODY patients were similar to those in healthy controls.

CONCLUSIONS

ZnTA quantification did not improve LADA diagnosis. However, positivity for ZnTA can be used as a negative MODY pre-diagnostic criterion even in the region of Central and East Europe, where other islet cell autoantibodies are common in MODY patients.

Zinc transporter 8 autoantibodies (ZnT8-ab) are associated with higher prevalence of multiple diabetes-related autoantibodies in adults with type 1 diabetes

AIM

The study aimed to assess the prevalence of zinc transporter 8 autoantibodies (ZnT8-ab), other diabetes-related autoantibodies and clinical manifestation of type 1 diabetes in adults, depending on age of the onset of disease.

METHODS

119 patients with type 1 diabetes, 66 at age <35 years (T1DM < 35) and 53 T1DM at age ≥35 years (T1DM ≥ 35). We assessed clinical features, GAD-ab, IA2-ab, ICA, ZnT8-ab and thyroid peroxidase antibodies (ATPO).

RESULTS

In T1DM < 35 lower initial serum C-peptide concentration was observed and diabetes ketoacidosis (DKA) was more common. ATPO positivity was more prevalent in T1DM ≥ 35 (35.8 vs 21.2%, p = 0.04). The prevalence of GAD-ab, IA2-ab and ZnT8-ab was similar in both groups, the titres of IA2-ab and ICA were higher in T1DM < 35 but titre of ZnT8-ab was higher in T1DM ≥ 35. The majority of T1DM < 35 patients were positive for three autoantibodies (40.9%), while T1DM ≥ 35 subjects most often presented with only one (30.2%) antibody, most commonly GAD-ab (81.2%). 45% T1DM < 35 and 34% T1DM ≥ 35 subjects were positive for ZnT8-ab. ZnT8-ab positive patients had higher titre and more frequent occurrence of multiple diabetes-related autoantibodies than ZnT8-ab negative patients.

CONCLUSIONS

Adults with T1DM < 35 and T1DM ≥ 35 differ in the severity of autoimmune response at diagnosis. ZnT8-ab positivity is related to higher titre and more frequent occurrence of multiple diabetes-related autoantibodies.