Downregulation of T-Cell Transcription Factors in Adult Latent Autoimmune Diabetes with High-Titer Glutamic Acid Decaroxylase Antibody

Abstract

Introduction: Latent autoimmune diabetes in adults (LADA) shows a heterogeneous clinical profile that is dependent on the glutamic acid decaroxylase antibody (GADA) titer. We speculated that LADA patients with a high or low GADA titer may have distinct T-lymphocyte subset profiles and distinct expression patterns of transcription factors involved in T-cell immunomodulation. Methods: Patients with LADA (n = 40) and type 2 diabetes (T2DM; n = 14) were recruited to the study, and peripheral blood mononuclear cells were isolated. The proportions of T-lymphocyte subsets (Th1 [T helper type 1], Th2 [T helper type 2], Treg [regulatory T], and Th17 [T helper type 17] cells) were determined by flow cytometry. Real-time polymerase chain reaction (PCR) was performed to estimate mRNA expression levels of the T-cell subtype-enriched transcription factors T-bet (Th1), GATA3 (Th2), transcription factor forkhead box protein 3 (FOXP3) (Treg), and RORC (Th17). Results: The frequency of Th1 (as a percentage of total CD4+T cells) was greater in the LADA patients with high-titer GADA than in the LADA patients with low-titer GADA (11.06 ± 1.62 vs. 7.05 ± 0.86, P = 0.030). Compared to the T2DM group, in the low-titer GADA group the frequency of Th1 was significantly reduced (7.05 ± 0.86 vs. 16.75 ± 3.73, P = 0.017) and the frequency of Th17 frequency was signficantly increased (1.11 ± 0.09 vs. 0.74 ± 0.16, P = 0.017). Compared to T2DM patients, in the high-titer GADA group there was a significantly reduced expression of FOXP3 (0.35 ± 0.13 vs. 1.75 ± 0.54, P = 0.002), RORC (0.53 ± 0.19 vs. 2.00 ± 0.77, P = 0.046), and GATA3 (0.74 ± 0.17 vs. 2.31 ± 0.91, P = 0.046). Similarly, the hightiter GADA group expressed reduced levels of FOXP3 and RORC compared to the low-titer GADA group (0.35 ± 0.13 vs. 1.50 ± 0.41, P = 0.027; 0.53 ± 0.19 vs. 1.35 ± 0.21, P = 0.027, respectively). There was a negative correlation between FOXP3 expression level and GADA titer for the entire cohort (r =-0.0433, P = 0.015) and a stronger negative correlation in LADA patients (r =-0.606, P = 0.008). Conclusion: LADA patients with high-titer GADA express lower levels of T-cell transcription factors, including the Treg transcription factor FOXP3, which may contribute to differences in the clinical profile compared to LADA patients with low-titer GADA. Trial Registration: ClinicalTrials.gov identifier, NCT01159847.