The loss of insulin-producing (beta) cells is central to the development of Type 1 diabetes (T1D). Beta-cell death occurs months to years prior to clinical T1D. Currently, we lack tools to quantitate beta-cell loss prior to T1D onset.
Circulating microRNAs (miRs) and cell-free (cf)DNA are increasingly recognised as biomarkers of disease progression, including T1D. We have optimised protocols to quantitate circulating miRs (ultra-high throughput qPCR1) and cell-free insulin DNA using methylation-specific plasmids on digital droplet PCR (ddPCR). Our initial islet miR-profiling studies (NGS/qPCR validation) identified 50 miRs with potential to predict T1D progression. We hypothesise that these miRs and insulin cfDNA correlate with beta-cell death and diabetes progression.
This cross-sectional study used plasma from a cohort of 180 T1D individuals (average T1D duration of 20±13yrs), including 58 with microvascular diabetes complications (T1DCx+), and 138 age and gender‑matched controls. C-peptide was measured using ultra-sensitive ELISA. Data were analysed using t-test, ANOVA or Spearman correlation as appropriate.
Several (10-14%) miRs were dysregulated in circulation of T1D individuals versus controls (with or without Cx and/or detectable c-peptide). Eight (16%) miRs positively correlated (P<0.05) with C-peptide levels in T1D (no correlation in controls). Two (4%) miRs inversely correlated (P<0.05) with T1D onset. Nine (18%) miRs inversely correlated (P<0.05) with T1D duration. Nine (18%) miRs had significantly lower abundance in subjects with T1D duration >20yrs compared to ≤20yrs. Table 1 summarises the major miRNA findings. I will also present our current analyses on the potential application of insulin cfDNA in predicting diabetes progression.
Our studies highlight the potential of circulating miRs and cfDNA in quantifying beta-cell mortality. We show that as beta-cells are lost in established diabetes (reduction in C-peptide) there is a reduction of released miRs. These miRNAs and insulin cfDNA are robust molecular markers of beta-cell death in Type 1 diabetes.