Autoantibodies and HLA class II DR-DQ genotypes in Ugandan children and adolescents with type 1 diabetes mellitus

The phenotype of type 1 diabetes in sub-Saharan Africa

The phenotype of type 1 diabetes in Africa, especially sub-Saharan Africa, is poorly understood. Most previously conducted studies have suggested that type 1 diabetes may have a different phenotype from the classical form of the disease described in western literature. Making an accurate diagnosis of type 1 diabetes in Africa is challenging, given the predominance of atypical diabetes forms and limited resources. The peak age of onset of type 1 diabetes in sub-Saharan Africa seems to occur after 18-20 years. Multiple studies have reported lower rates of islet autoantibodies ranging from 20 to 60% amongst people with type 1 diabetes in African populations, lower than that reported in other populations. Some studies have reported much higher levels of retained endogenous insulin secretion than in type 1 diabetes elsewhere, with lower rates of type 1 diabetes genetic susceptibility and HLA haplotypes. The HLA DR3 appears to be the most predominant HLA haplotype amongst people with type 1 diabetes in sub-Saharan Africa than the HLA DR4 haplotype. Some type 1 diabetes studies in sub-Saharan Africa have been limited by small sample sizes and diverse methods employed. Robust studies close to diabetes onset are sparse. Large prospective studies with well-standardized methodologies in people at or close to diabetes diagnosis in different population groups will be paramount to provide further insight into the phenotype of type 1 diabetes in sub-Saharan Africa.

The Prevalence of Islet Autoantibodies in Children and Adolescents With Type 1 Diabetes Mellitus: A Global Scoping Review

Background and Purpose

Pancreatic islet autoantibodies (iAb) are the hallmark of autoimmunity in type 1 diabetes. A more comprehensive understanding of the global iAb prevalence could help reduce avertible morbidity and mortality among children and adolescents and contribute to the understanding in the observed differences in the incidence, prevalence and health outcomes of children and adolescents with type 1 diabetes across and within countries. We present the first scoping review that provides a global synthesis of the prevalence of iAb in children and adolescents with type 1 diabetes.

Research Design and Methods

We searched Ovid MEDLINE® with Daily Update, Embase (Elsevier, embase.com) and PubMed (National Library of Medicine -NCBI), for studies pertaining to prevalence in children and adolescents (0-19) with type 1 diabetes published between 1 Jan 1990 and 18 June 2021. Results were synthesized using Covidence systematic review software and meta-analysis was completed using R v3·6·1. Two reviewers independently screened abstracts with a third reviewer resolving conflicts (k= 0·92).

Results

The review revealed 125 studies from 48 different countries, with 92 from high-income countries. Globally, in new-onset type 1 diabetes, IA-2A was the most prevalent iAb 0·714 [95% CI (0·71, 0·72)], followed by ICA 0·681 [95% CI (0·67, 0·69)], ZnT8A was 0·654 [95% CI (0·64, 0·66)], GADA 0·636 [95% CI (0·63, 0·66)] and then IAA 0·424 [95% CI (0·42, 0·43)], with substantial variation across world regions. The weighted mean prevalence of IA-2A was more variable, highest in Europe at 0·749 [95% CI (0·74, 0·76)] followed by Northern America 0·662 [95% CI (0·64, 0·69)], Latin America and the Caribbean 0·632 [95% CI (0·54, 0·72)], Oceania 0·603 [95% CI (0·54, 0·67)], Asia 0·466 [95% CI (0·44, 0·50)] and Africa 0·311 [95% CI (0·23, 0·40)]. In established cases of type 1 diabetes, GADA was the most prevalent iAb 0·407 [95% CI (0·39, 0·42)] followed by ZnT8A 0·322 [95% CI (0·29, 0·36)], IA-2A 0·302 [95% CI (0·29, 0·32)], IAA 0·258 [95% CI (0·24, 0·26)] and ICA 0·145 [95% CI (0·13, 0·16)], again with substantial variation across world regions.

Conclusion

Understanding the global prevalence of iAb in children and adolescents with type 1 diabetes could help with earlier identification of those at-risk of developing type 1 diabetes and inform clinical practice, health policies, resource allocation, and targeted healthcare interventions to better screen, diagnose and manage children and adolescents with type 1 diabetes.

Zinc transporter 8 (ZnT8) autoantibody prevalence in black South African participants with type 1 diabetes

BACKGROUND

Autoantibodies to β-cell specific antigens are markers of type 1 diabetes. The most recently identified autoantibodies are targeted to the zinc transporter 8 (ZnT8) protein located in the membrane of β-cell insulin secretory granules. The prevalence of ZnT8 autoantibodies in newly diagnosed participants with type 1 diabetes has been found to range from 33 to 80 %. Due to the lack of data on the immunological aetiology of type 1 diabetes in African populations, this study aimed to determine the prevalence of ZnT8 autoantibodies in black South Africans with type 1 diabetes and whether ZnT8 autoantibody positivity was associated with age at diagnosis and disease duration.

METHODS

Participants with type 1 diabetes and controls were recruited from the greater Johannesburg area, South Africa. Positivity for ZnT8, GAD65 and IA2 autoantibodies was determined by ELISA.

RESULTS

Participants with type 1 diabetes (n = 183) and controls (n = 49) were matched for age (29.1 ± 9.53 vs. 27.3 ± 7.29, respectively; p = 0.248). The mean age at diagnosis for participants with type 1 diabetes was 20.8 ± 8.46 years. The prevalence of ZnT8 autoantibody positivity was 17.5 % (32 of 183) in participants with type 1 diabetes with a median disease duration of 7.00 [2.00; 11.0] years. ZnT8 autoantibody prevalence in newly diagnosed participants (< 1 year duration) was 27.3 % (6 of 22). Logistic regression analysis found an association between ZnT8 autoantibody positivity and shorter disease duration (OR: 0.9 (0.81-1.00); p = 0.042). In addition, ZnT8 autoantibody positivity was significantly associated with an increased chance of being GAD65 (OR: 3.37 (1.10-10.3)) and IA2 (OR: 8.63 (2.82-26.4)) autoantibody positive. Multiple regression analysis found no association between ZnT8 autoantibody positivity and age at diagnosis. However, the presence of ≥ 2 autoantibodies was associated with a younger age at diagnosis of type 1 diabetes when compared to participants with ≤ 1 autoantibody (B = -5.270; p = 0.002).

CONCLUSIONS

The presence of ZnT8 autoantibodies was not related to a younger age at diagnosis in black South African patients with type 1 diabetes. However, the greater the numbers of autoantibodies present in an individual the earlier the age at diagnosis. ZnT8 autoantibodies decline with disease duration in the black South African population.