Objective: Previous studies have indicated that the latent autoimmune diabetes in adults (LADA) phenotype is heterogeneous and that LADA patients share features of type 1 and type 2 diabetes in various proportions. We tested for association of known type 1 and type 2 diabetes susceptibility genes in LADA subjects and analyzed relationships to a marker of autoimmune activity (titers of anti-GAD) and a phenotypic risk factor of type 2 diabetes (BMI).
Research design and methods: Data were assembled from the Nord-Trøndelag Health Study (HUNT) study, which comprises the adult population of an entire county in Norway. We genotyped 60 single nucleotide polymorphisms (SNPs) known to be associated with type 1 or type 2 diabetes, including 14 tag SNPs used for HLA haplotyping in 120 type 1 diabetic, 126 LADA, and 1,090 type 2 diabetic patients and 1,503 age- and sex-matched nondiabetic subjects.
Results: The majority of the strongly associated HLA haplotypes for type 1 diabetes were significantly associated with LADA in general, but mainly with high anti-GAD LADA patients. Two distinct HLA haplotypes were associated only with LADA and mainly in low anti-GAD LADA patients. There were no associations of non-HLA type 1 diabetes loci with LADA. Of type 2 diabetes-associated genes, the CC/CT genotypes of rs7961581 (TSPAN8) and the obesity-linked AA/AC genotypes of rs8050136 (FTO) were associated with LADA in general, but mainly in low anti-GAD LADA patients (P = 0.004 and P = 0.004, respectively).
Conclusions: Genetic heterogeneity in LADA is linked to various degrees of autoimmune activity and may be partly distinct from both type 1 and type 2 diabetes.