AIMS: C-peptide secretion is currently the only available clinical biomarker to measure
residual beta-cell function in type 1 diabetes. However, the natural history of C-peptide
decline after diagnosis can vary considerably dependent upon several variables. We
investigated the shape of C-peptide decline over time from type 1 diabetes onset in
relation to age at diagnosis, HbA1c levels and insulin dose. MATERIALS AND METHODS:
We analysed data from 3,929 type 1 diabetes patients recruited from 7 European centres
representing all age groups at disease onset (childhood, adolescence, adulthood).
The influence of the age at onset on beta-cell function was investigated in a longitudinal
analysis at diagnosis and up to 5-years follow-up. RESULTS: Fasting C-peptide data
at diagnosis were available in 3,668 patients stratified according to age at diagnosis
in four groups (<5 yrs, n=344; >5 yrs< 10 yrs, n=668; >10 yrs<18yrs, n=991; >18 yrs,
n=1655). Fasting C-peptide levels were positively correlated with age (p<0.001); the
subsequent decline in fasting C-peptide over time was log-linear with a greater decline
rate in younger age groups (p<0.0001). CONCLUSIONS: This study reveals a positive
correlation between age at diagnosis of type 1 diabetes and fasting C-peptide with
a more rapid decline of beta-cell function in the very young patients. These data
can inform the design of clinical trials using C-peptide values as an end-point for
the effect of a given treatment.
