993-P: Cell-Free DNA Methylation as a Biomarker of Islet-Cell Death in Youth with Type 2 Diabetes

Type 2 diabetes (T2D) in youth is diagnosed after irreparable islet damage. Cell-free DNA methylation can be used as a marker of islet cell death after islet transplantation. We assessed the performance of cell-free (cf) DNA in the discrimination of T2D and as a circulating biomarker of islet cell death. Methods: We recruited 72 youth 10-20 years old through provider networks in Atlanta, Georgia. Participant groups were (a) new onset T2D (n=21, within 16 weeks of diagnosis) ; (b) healthy, normal weight (n=23, no family history of diabetes) ; and (c) High Risk (HR, n=31, BMI ≥ 95th %ile or acanthosis nigricans; with family history) . All participants had an oral glucose tolerance test. Based on genes uniquely unmethylated in islets, plasma was analyzed at 9 CpG sites across 3 genes (INS, GCK, IADD) using bisulfite conversion and next generation sequencing. T2D and HR were grouped and compared to Healthy by (a) linear regression of % methylation on group, and (b) area under the curve (AUC) ROC analysis, adjusted for age and BMI %ile. Results: Mean age was higher among healthy participants (17yr SD±3) vs. T2D+HR (14±2) . Age- & BMI %ile- adjusted methylation of INS GRCh38 CpG Chr11:2160843 was highest in T2D+HR (94.8%, 95%CI: 93.5, 96.1) and lowest in Healthy (90.0%, 95%CI: 87.7, 92.2) , p=0.0051. Secondly, at CpG Chr11:2160806, methylation was highest in T2D+HR (85.6%, 95%CI: 83.3, 87.8) vs. Healthy (83.1%, 95%CI: 79.1, 87.1) , p=0.0409. Cell-free INS methylation improved the AUC for T2D or severe prediabetes (i.e., combined impaired fasting glucose + impaired glucose tolerance, per ADA cutpoints) from 0.72 in models of age and BMI %ile to 0.81 in models also including cfINS methylation. Conclusions: Higher % methylated cfINS was found in T2D+HR youth, rather than hypothesized lower levels. It is possible that during T2D onset, non-islet apoptosis occurs in larger concentration than islet cell apoptosis. Methylated cfINS improved discrimination of T2D and severe prediabetes by nearly 10% beyond age and BMI.