Circulating unmethylated insulin DNA as a biomarker of human beta cell death: a multi-laboratory assay comparison.

CONTEXT: There is an unmet need for biomarkers of pancreatic beta-cell death, to improve early diagnosis of type 1 diabetes, enroll subjects into clinical trials, and assess treatment response. To address this need, several groups developed assays measuring insulin DNA with unmethylated CpG sites in cell-free DNA. Unmethylated insulin DNA should be derived predominantly from beta-cells, and indicate ongoing beta-cell death.

OBJECTIVE: To assess the performance of three unmethylated insulin DNA assays.

DESIGN AND PARTICIPANTS: Plasma or serum samples from 13 subjects undergoing total pancreatectomy and islet autotransplantation were coded and provided to investigators to measure unmethylated insulin DNA. Samples included a negative control taken post-pancreatectomy but pre-transplant, and a positive control taken immediately following islet infusion. We assessed technical reproducibility, linearity, and persistence of detection of unmethylated insulin DNA for each assay.

RESULTS: All assays discriminated between the negative sample and samples taken directly from the islet transplant bag; two of three discriminated negative samples from those taken immediately after islet infusion. When high levels of unmethylated insulin DNA were present, technical reproducibility was generally good for all assays.

CONCLUSIONS: The measurement of beta cell cell-free DNA, including insulin, is a promising approach, warranting further testing and development in those with or at-risk for type 1 diabetes, as well as in other settings where understanding the frequency or kinetics of beta cell death could be useful.