Autoimmunological and metabolic markers of type 1 diabetes in first-degree relatives of patients with type 1 diabetes

Aim: The aim of the study was to assess the first phase of insulin secretion and C-peptide concentration in relation to the occurrence of antibodies (glutamic acid decarboxylase - GADA, insulin autoantibodies - IAA, and autoantibodies to tyrosine phosphatase - IA-2A) in a group of first-degree relatives of patients with type 1 diabetes. Material and methods: The study was performed in a group of 90 first-degree relatives, aged 16-65 years. The C-peptide concentration was determined by the ELISA method, insulin concentration by the EASIA method, and titres of GADA, IAA and IA-2A by the RIA method. Results: In 28 patients (31.11%), the presence of a positive titre of at least one of the antibodies was observed. The highest percentage was found for IAA (22.22%) and GADA (11.11%). We found a positive correlation between C-peptide and IAA (r = 0.282, p < 0.002). We observed a significantly higher insulin concentration at 0 min (p < 0.002) and significantly lower in the 1st min (p < 0.008) and 3rd min of the test (p < 0.005) in the study group as compared to the controls. Significantly higher fasting insulin concentrations were observed in the group with a positive IAA titre as compared to subjects without IAA (p < 0.04). Conclusions: The increase in fasting C-peptide and insulin concentrations, with reduced β cell function, may reflect a compensative increase in insulin secretion in the group of first-degree relatives and especially in the group with a positive titre of at least one of the antibodies seems to be a factor that can slow down the manifestation of clinical signs of the disease.