Levels of circulating insulin cell-free DNA in women with polycystic ovary syndrome - a longitudinal cohort study

BackgroundWomen with Polycystic Ovary Syndrome (PCOS) present a heterogeneous reproductive and metabolic profile with an increased lifetime risk of Type 2 Diabetes (T2D). Early biomarkers of these metabolic disturbances in PCOS women have not been identified. The abundance of circulating insulin gene promotor cell-free DNA (INS cfDNA) was shown to be valuable as a predictive biomarker of -cell death in individuals with Type 1 diabetes (T1D) as well as with gestational diabetes. Since -cell death is common to the development of T1D as well as in T2D, we aimed to investigate if insulin-coding DNA is more abundant in circulation of PCOS women (vs Controls) and if their levels change after 6yr. follow-up as a potential measure to predict future T2D.MethodsA cohort of 40 women diagnosed with PCOS according to Rotterdam 2003 criteria and eight healthy controls were examined at baseline and 6years follow-up. Clinical measurements for evaluation of glucose homeostasis as well as blood/serum samples were obtained at each visit. Methylated and unmethylated INS cfDNA were quantified using droplet digital PCR. Differences between groups were assessed using Kruskall-Wallis test and Wilcoxon Signed rank test.ResultsAt baseline, there was no detectable difference in copy number (copies/L) of methylated (p=0.74) or unmethylated INS cfDNA (p=0.34) between PCOS and Control groups. At follow up, neither methylated (p=0.50) nor unmethylated INScfDNA levels (p=0.48) differed significantly between these groups. Likewise, when pooling the groups, there was no difference between baseline and follow up, in terms of copies of methylated or unmethylated INS cfDNA (p=0.38 and p=0.52, respectively). There were no significant correlations between counts of unmethylated or methylated cfDNA and the clinical measurements of -cell function and pre-diabetes.ConclusionThe circulating level of unmethylated and methylated INScfDNA is similar between PCOS and Controls and cannot be used to predict islet -cell loss and progression to Type 2 diabetes in a 6-year follow-up.Trial registrationThe Danish Data Protection Agency (REG-31-2016. Approval: 01-12-2015) and by the Danish Scientific Ethical committee of Region Zealand (Journal no. SJ-525. Approval: 13-06-2016), Clinicaltrials.gov, (NCT03142633, registered 1. March, 2017, Retrospectively registered).