[Effects of rare islet autoantibodies on islet function in patients with latent autoimmune diabetes in adults].

OBJECTIVE: To observe the changes of islet function in ZnT8A positive and IA-2A positive patients so as to provide rationales for early intervention of LADA patients.

METHODS: A total of 69 outpatients and inpatients with newly diagnosed LADA testing for GADA, IA-2A and ZnT8A by radioligand binding assay (RBA) were enrolled from 2005 to 2010, including 13 with double positive for GADA and ZnT8A (GADA+ZnT8A double positive group), 14 with double positive for GADA and IA-2A (GADA+IA-2A double positive group) and 42 with positive for GADA alone (GADA positive group), 40 type 2 diabetes mellitus (T2DM) patients negative for the above three autoantibodies were selected as control subjects (T2DM group). The baseline clinical data of all groups were compared and all patients were followed annually for 3 years. Fasting plasma glucose (FBG), HbA1c, fasting C-peptide (FCP), C-peptide 2 h after meal (2 h CP), triglyceride (TG), total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C) and low-density lipoprotein cholesterol (LDL-C) were detected and compared among the above groups during the follow-ups.

RESULTS: Compared to GADA positive group and T2DM group, the GADA+IA-2A double positive group had higher level of baseline FBG and HbA1c (10.5 ± 3.6) mmol/L and (9.3 ± 2.6) % vs (9.2 ± 2.0) mmol/L and (7.4 ± 2.0) %, P = 0.017, 0.011) and had lower level of baseline FCP (415 (68-934) vs 538 (224-1 146) and 643 (163-1 658) pmol/L, P = 0.015, 0.003). During the follow-ups, FCP decreased year-on-year in GADA+ZnT8A double positive, GADA+IA-2A double positive and GADA positive groups. The annual average rate of decrease in FCP was more rapid in GADA+ZnT8A double positive and GADA+IA-2A double positive groups than those in GADA positive alone and T2DM groups (all P < 0.01).

CONCLUSIONS: The islet functions of newly diagnosed LADA patients with GADA and IA-2A positive are much worse. And emergence of ZnT8A and IA-2A may accelerate the failure of islet function with diabetic progress in LADA patients.