<i>TCF7L2</i> Genetic Variants Contribute to Phenotypic Heterogeneity of Type 1 Diabetes.

Abstract

The phenotypic diversity of type 1 diabetes suggests heterogeneous etiopathogenesis. We investigated the relationship of type 2 diabetes-associated transcription factor 7 like 2 (<i>TCF7L2</i>) single nucleotide polymorphisms (SNPs) with immunologic and metabolic characteristics at type 1 diabetes diagnosis. We studied TrialNet participants with newly diagnosed autoimmune type 1 diabetes with available <i>TCF7L2</i> rs4506565 and rs7901695 SNP data (<i>n</i> = 810; median age 13.6 years; range 3.3-58.6). We modeled the influence of carrying a <i>TCF7L2</i> variant (i.e., having 1 or 2 minor alleles) on the number of islet autoantibodies and oral glucose tolerance test (OGTT)-stimulated C-peptide and glucose measures at diabetes diagnosis. All analyses were adjusted for known confounders. The rs4506565 variant was a significant independent factor of expressing a single autoantibody, instead of multiple autoantibodies, at diagnosis (odds ratio [OR] 1.66 [95% CI 1.07, 2.57], <i>P</i> = 0.024). Interaction analysis demonstrated that this association was only significant in participants ≥12 years old (<i>n</i> = 504; OR 2.12 [1.29, 3.47], <i>P</i> = 0.003) but not younger ones (<i>n</i> = 306, <i>P</i> = 0.73). The rs4506565 variant was independently associated with higher C-peptide area under the curve (AUC) (<i>P</i> = 0.008) and lower mean glucose AUC (<i>P</i> = 0.0127). The results were similar for the rs7901695 SNP. In this cohort of individuals with new-onset type 1 diabetes, type 2 diabetes-linked <i>TCF7L2</i> variants were associated with single autoantibody (among those ≥12 years old), higher C-peptide AUC, and lower glucose AUC levels during an OGTT. Thus, carriers of the <i>TCF7L2</i> variant had a milder immunologic and metabolic phenotype at type 1 diabetes diagnosis, which could be partly driven by type 2 diabetes-like pathogenic mechanisms.