2234-P: Metabolic and Immunological Characteristics of Presymptomatic First-Degree Relatives of Chinese Patients with Type 1 Diabetes

Introduction and Objective: Screening for islet autoantibodies (IAb) enables early identification of individuals at high risk of type 1 diabetes (T1D), yet data from China are scarce. This study aimed to investigate metabolic and immunological characteristics of first-degree relatives (FDRs) of T1D patients in China. Methods: From May 1st to Oct 19th, 2025, FDRs of T1D patients were recruited, whose demographic data and blood samples were collected. Clinical and metabolic parameters were compared between IAb-positive (IAb+) and IAb-negative (IAb−) individuals. Results: Of 157 FDRs (44.6% male; age: 10.6 7.8,18.7 years; 81.8% under 18 years), 11 (7.0%) IAb+ individuals were identified. Single IAb positivity was observed in 6.4% participants, including GADA (3.8%), IAA (2.5%), and IA-2A (1.3%). Only one 4-year-old child had two positive IAb (GADA and IAA). All IAb+ individuals were classified as stage 1 T1D without dysglycemia. Most affected FDRs were offspring or siblings (mothers: 72.8% of parents; elder sisters: 66.7% of siblings). Compared with IAb- individuals, IAb+ individuals had significantly lower fasting C-peptide levels (0.23 vs. 0.45 nmol/L; P=0.019), while other metabolic metrics were similar between groups (Table 1). Conclusion: The prevalence of IAb+ among FDRs in China was 7.0%. The affected individuals exhibited reduced fasting C-peptide levels, indicating early β-cell dysfunction despite preserved normoglycemia. Disclosure Y. Mo: None. J. Wu: None. Y. Zhou: None. Z. Lin: None. Y. Ni: None. Q. Lin: None. P. Ling: None. J. Yan: None. D. Yang: None. H. Deng: None. S. Luo: None. C. Wang: None. Funding Noncommunicable Chronic Diseases National Science and Technology Major Project (2023ZD0508204, 2023ZD0508203), Science and Technology Projects in Guangzhou (2023A04J1087), The Research Foundation of Medical Science and Technology of Guangdong Province (A2025154)