Fasting and meal-stimulated serum C-peptide in long-standing type 1 diabetes mellitus

Charlotte E. Vollenbrock, Dick Mul, Pim Dekker, Erwin Birnie, Martine M.C. de Vries-Velraeds, Lianne Boesten, Joost Groen, Petronella H.L.M. Geelhoed-Duijvestijn, Henk Jan Aanstoot, Bruce H.R. Wolffenbuttel*

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

2 Citations (Scopus)
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Aims: This study aims to evaluate the stability of C-peptide over time and to compare fasting C-peptide and C-peptide response after mixed-meal tolerance test (MMTT) at T90 or T120 with C-peptide area under the curve (AUC) in long-standing type 1 diabetes. Methods: We included 607 type 1 diabetes individuals with diabetes duration >5 years. C-peptide concentrations (ultrasensitive assay) were collected in the fasting state, and in a subpopulation after MMTT (T0, just prior to, T30-T60-T90-T120, 30–120 min after ingestion of mixed-meal) (n = 168). Fasting C-peptide concentrations (in n = 535) at Year 0 and Year 1 were compared. The clinical determinants associated with residual C-peptide secretion and the correspondence of C-peptide at MMTT T90 / T120 and total AUC were assessed. Results: A total of 153 participants (25%) had detectable fasting serum C-peptide (i.e ≥ 3.8 pmol/L). Fasting C-peptide was significantly lower at Year 1 (p < 0.001, effect size = −0.16). Participants with higher fasting C-peptide had a higher age at diagnosis and shorter disease duration and were less frequently insulin pump users. Overall, 109 of 168 (65%) participants had both non-detectable fasting and post-meal serum C-peptide concentrations. The T90 and T120 C-peptide values at MMTT were concordant with total AUC. In 17 (10%) individuals, C-peptide was only detectable at MMTT and not in the fasting state. Conclusions: Stimulated C-peptide was detectable in an additional 10% of individuals compared with fasting in individuals with >5 years of diabetes duration. T90 and T120 MMTT measurements showed good concordance with the MMTT total AUC. Overall, there was a decrease of C-peptide at 1-year follow-up.

Original languageEnglish
Article numbere15012
Number of pages9
JournalDiabetic Medicine
Issue number2
Early online date18-Nov-2022
Publication statusPublished - Feb-2023


  • C-peptide
  • fasting
  • insulin-secreting cells
  • reproducibility of results
  • type 1 diabetes

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