Detection of β cell death in diabetes using differentially methylated circulating DNA

In diabetes mellitus, beta cell destruction is largely silent and can be detected only after significant loss of insulin secretion capacity. We have developed a method for detecting beta cell death in vivo by amplifying and measuring the proportion of insulin 1 DNA from beta cells in the serum. By using primers that are specific for DNAmethylation patterns in beta cells, we have detected circulating copies of beta cell-derived demethylated DNA in serum of mice by quantitative PCR. Accordingly, we have identified a relative increase of beta cell-derived DNA after induction of diabetes with streptozotocin and during development of diabetes in nonobese diabetic mice. We have extended the use of this assay to measure beta cell-derived insulin DNA in human tissues and serum. We found increased levels of demethylated insulin DNA in subjects with new-onset type 1 diabetes compared with age-matched control subjects. Our method provides a noninvasive approach for detecting beta cell death in vivo that may be used to track the progression of diabetes and guide its treatment.