Three-phasic pattern of C-peptide decline in type 1 diabetes patients with partial remission

To explore the different patterns of C-peptide decline in patients with and without partial remission of newly diagnosed type 1 diabetes (T1D).

A total of 298 patients with new-onset T1D were followed up regularly at 3 months' interval to investigate the loss of C-peptide. Partial remission was determined by postprandial C-peptide ≥300 pmol/L or insulin dose-adjusted A1c ≤ 9 in the absence of C-peptide. Beta-cell function was defined as preserved, residual or failed by postprandial C-peptide of ≥200 pmol/L, 50-200 pmol/L or ≤50 pmol/L, respectively.

Altogether, 199 out of 298 patients (125 adults) had partial remission. The pattern of C-peptide change in patients with partial remission was three-phasic, demonstrating an upward trend followed by a downward trend of fast first and then slow, while the pattern in patients without partial remission was biphasic, showing an initial fast fall and a subsequent slower decrease. The patterns remained consistent when patients were stratified by the age of onset. At 3 years, there were 71% of the patients with partial remission still had preserved or residual beta-cell function, while 89% of the patients who had no partial remission developed beta-cell function failure. In patients whose partial remission ended, the average C-peptide was still higher than duration-matched patients without partial remission.

Patients with partial remission of T1D have a distinct three-phasic pattern of C-peptide decline, other than the widely recognized biphasic pattern. The effect of partial remission still exist​s after remission ends.