Number of autoantibodies and HLA genotype, more than high titers of glutamic acid decarboxylase autoantibodies, predict insulin dependence in latent autoimmune diabetes of adults.
OBJECTIVE
In latent autoimmune diabetes of adults (LADA), the progression into insulin-dependent diabetes is usually faster than in type 2 diabetes (T2D) but the factors influencing this progression are not completely known. In this study, we searched for sensitive markers associated with early development of insulin dependence.


METHODS
The screening of 5568 T2D patients for glutamic acid decarboxylase autoantibodies (GAD65Ab) identified 276 LADA patients (M=131; F=145) and in 251 of them, tyrosine phosphatase-2 (IA-2Ab) and thyroperoxidase autoantibodies (TPOAbs), some clinical features and genotype variation of the main type 1 diabetes (T1D) disease susceptibility loci (HLA-DRB1 and HLA-DQB1) were analyzed.


RESULTS
Four years after the diagnosis of diabetes, high GAD65Ab titer was not significantly associated with faster progression toward insulin deficiency (P=0.104). Patients with GAD65Ab and TPOAb or IA-2Ab or triple positivity for both islet and TPOAbs (GAD65Ab/IA-2Ab/TPOAb) showed a significantly faster disease progression (P=0.002). Among 104 TPOAb-positive LADA patients, 10 received replacement therapy (l-thyroxine), 43 showed high TSH levels (62.7% developed insulin dependence), and 3 had hyperthyroidism treated with methimazole. Multivariate analysis revealed a significant effect on disease progression only for TPOAb (P=0.022), female gender (P=0.036), low body mass index (BMI; P=0.001), and T1D high/intermediate risk HLA-DRB1/DQB1 genotypes grouped (P=0.020).


CONCLUSIONS
High GAD65Ab titers per se are not a major risk factor for disease progression in LADA, while the number of positive autoantibodies and HLA DRB1-DQB1 genotypes at high risk for T1D are significant predictors. Moreover, clinical characteristics such as low BMI and female gender are more likely to identify patients who will require insulin therapy within 4 years of diagnosis.
Maioli
M
M
Department of Internal Medicine, University of Sassari, Sassari, Italy. marimaio@uniss.it
Pes
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Delitala
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Puddu
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Falorni
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Tolu
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Lampis
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Orrù
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Secchi
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Cicalò
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Floris
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Madau
G F
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Pilosu
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Whalen
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Cucca
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D000328:Adult; D000368:Aged; D001323:Autoantibodies / Q000276:immunology*; D003922:Diabetes Mellitus, Type 1 / Q000188:drug therapy / Q000235:genetics* / Q000276:immunology*; D005260:Female; D020022:Genetic Predisposition to Disease / Q000235:genetics; D005838:Genotype; D005968:Glutamate Decarboxylase / Q000276:immunology*; D006683:HLA-DQ Antigens / Q000235:genetics; D059848:HLA-DQ alpha-Chains; D059866:HLA-DQ beta-Chains; D006684:HLA-DR Antigens / Q000235:genetics; D059811:HLA-DRB1 Chains; D000949:Histocompatibility Antigens Class II / Q000235:genetics*; D006801:Humans; D007328:Insulin / Q000627:therapeutic use*; D053208:Kaplan-Meier Estimate; D008297:Male; D008875:Middle Aged
D001323:Autoantibodies; D006683:HLA-DQ Antigens; D059848:HLA-DQ alpha-Chains; D059866:HLA-DQ beta-Chains; C069050:HLA-DQA1 antigen; C069051:HLA-DQB1 antigen; D006684:HLA-DR Antigens; D059811:HLA-DRB1 Chains; D000949:Histocompatibility Antigens Class II; D007328:Insulin; D005968:Glutamate Decarboxylase