Oak S, Gaur LK, Radtke J, Patel R, Iyer D, Ram N, Gaba R, Balasubramanyam A, Hampe CS. Masked and overt autoantibodies specific to the DPD epitope of 65-kDa glutamate decarboxylase (GAD65-DPD) are associated with preserved β-cell functional reserve in ketosis-prone diabetes.
J Clin Endocrinol Metab 2014;
99:E1040-4. [PMID:
24601691 PMCID:
PMC4037721 DOI:
10.1210/jc.2013-4189]
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Abstract
CONTEXT
Ketosis-prone diabetes (KPD), defined by presentation with diabetic ketoacidosis (DKA), comprises 4 subgroups based on the presence or absence of islet cell autoantibodies (A(-) or A(+)) and β-cell functional reserve (β(-) or β(+)). Among A(+) KPD, autoantibody epitope reactivity to 65-kDa glutamate decarboxylase (GAD65), defined by monoclonal GAD65Ab(DPD), was associated with greater β-cell functional reserve. In a majority of healthy individuals, GAD65Ab are present in the sera but are masked by anti-idiotypic antibodies; in contrast, overtly GAD65Ab-positive patients with autoimmune type 1 diabetes patients lack these anti-idiotypic antibodies.
OBJECTIVE
Our objective was to determine the presence of masked and overt GAD65Ab(DPD) in relation to β-cell function and genetic risk factors in KPD patients.
DESIGN
We investigated the associations of masked and overt GAD65Ab(DPD) with β-cell functional reserve, and their relationship with human leukocyte antigen (HLA) class II haplotypes linked to autoimmune diabetes susceptibility or resistance, in a large KPD cohort.
PATIENTS
Adult KPD patients (n = 384) were followed longitudinally in a research clinic.
MAIN OUTCOME MEASURES
β-Cell function, autoantibody status, GAD65Ab epitopes, and HLA class II haplotypes were evaluated.
RESULTS
Overall, KPD patients with β-cell functional reserve (β(+) subgroups) showed significantly higher frequency of masked GAD65Ab(DPD) than patients without β-cell functional reserve (β(-) subgroups): 112 of 144 (79%) compared with 59 of 100 (59%), respectively (P = .002). Masked or overt GAD65Ab(DPD) were also more frequent among autoantibody-positive patients with preserved β-cell functional reserve (A(+)β(+) KPD) than those lacking β-cell function (A(+)β(-) KPD): 77% compared with 55% (P = .01). The susceptibility HLA haplotypes DQA1*0301/DQB1*0302 and DQA1*0301/DQB1*0201 were associated with absence of overt or masked GAD65Ab(DPD) (odds Ratios 2.3 and 2.2, respectively).
CONCLUSIONS
Masked GAD65Ab(DPD) are strongly associated with preserved β-cell functional reserve among patients with KPD. Absence of GAD65Ab(DPD) reactivity is associated with 2 HLA class II susceptibility haplotypes for autoimmune type 1 diabetes.
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