First-emerging islet autoantibody and glucose metabolism: search for type 1 diabetes subtypes

Abstract

Objective Subtypes in type 1 diabetes pathogenesis have been implicated based on the first-appearing autoantibody (primary autoantibody). We set out to describe the glucose metabolism in preclinical diabetes in relation to the primary autoantibody in children with HLA-conferred disease susceptibility. Design and methods Dysglycemic markers are defined as a 10% increase in HbA1c in a 3–12 months interval or HbA1c ≥5.9% (41 mmol/mol) in two consecutive samples, impaired fasting glucose or impaired glucose tolerance, or a random plasma glucose value ≥7.8 mmol/L. A primary autoantibody could be detected in 295 children who later developed at least 1 additional biochemical autoantibody. These children were divided into three groups: insulin autoantibody (IAA) multiple (n  = 143), GAD antibody (GADA) multiple (n  = 126) and islet antigen 2 antibody (IA-2A) multiple (n  = 26). Another 229 children seroconverted to positivity only for a single biochemical autoantibody and were grouped as IAA only (n  = 87), GADA only (n  = 114) and IA-2A only (n  = 28). Results No consistent differences were observed in selected autoantibody groups during the preclinical period. At diagnosis, children with IAA only showed the highest HbA1c (P < 0.001 between groups) and the highest random plasma glucose (P = 0.005 between groups). Children with IA-2A only progressed to type 1 diabetes as frequently as those with IA-2A multiple (46% vs 54%, P = 0.297) whereas those with IAA only or GADA only progressed less often than children with IAA multiple or GADA multiple (22% vs 62% (P < 0.001) and 7% vs 43% (P < 0.001)), respectively. Conclusions The phenotype of preclinical diabetes defined by the primary autoantibody is not associated with any discernible differences in glucose metabolism before the clinical disease manifestation.