C-peptide Persistence in People with Type 1 Diabetes: Predictors and Consequences

As immunoassays for C-peptide have become more sensitive it has become more apparent that many people with Type 1 diabetes have some degree of residual beta cell function. However the true extent of this across the full range of age of onset and duration of Type 1 diabetes is unclear. Neither is it clear how the genetic determinants of Type 1 diabetes or other clinical features of diabetes relate to this residual function. Whether residual beta cell function alters the clinical course of Type 1 diabetes and the incidence of acute or chronic complications is also unclear. The Scottish Diabetes Research Network Type 1 Bioresource (SDRNT1BIO) is a large (n=6127) collection of biosamples and retrospective and prospective data from a representative sample of people with Type 1 diabetes in Scotland. Participants had a clinical diagnosis of Type 1 diabetes with confirmation of insulin use within a year of onset but with no constraint on age at diagnosis. The cohort has been genotyped and random serum C-peptide (Roche ultrasensitive immunoassay) measured at recruitment. Overall 39% had detectable C-peptide (≥5 pmol/L) with prevalence being highest with older age of onset (p=6.9x10^-05) and shorter duration (p=1.8x10^-10). Heritability was 0.31 for age at onset and 0.26 for C-peptide adjusted for sex and age at onset. This presentation will summarise the distribution of C-peptide levels by age at onset and duration, will explore genetic associations with C-peptide levels and will summarise the relationship of C-peptide levels to complications in this cohort.