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

Abstract

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.

Residual β-cell function in Brazilian Type 1 diabetes after 3 years of diagnosis: prevalence and association with low presence of nephropathy

“…[ 11 ]. And a more recent study considered T1D individuals with diabetes duration with more than 5 years to evaluate C-peptide and complications [ 12 ] . Therefore, we selected participants with more than 3 years of diagnosis, but with an average diabetes duration time of 17 years, thus subject to the risk of complications.…”

Cohort profile: the ‘Biomarkers of heterogeneity in type 1 diabetes’ study—a national prospective cohort study of clinical and metabolic phenotyping of individuals with long-standing type 1 diabetes in the Netherlands

“…Third, the stability of residual C-peptide production over time was assessed. 49 About 25% of PWDs still showed some residual C-peptide production ( table 2 ). About 10% of participants who did not show fasting residual C-peptide production did still show meal-stimulated residual C-peptide production.…”

Cohort profile: the ‘Biomarkers of heterogeneity in type 1 diabetes’ study – a prospective cohort study of clinical and metabolic phenotyping of individuals with long-standing type 1 diabetes

“…2 Several studies on factors of heterogeneity in T1D stages 1-3 have been initiated. 16 While we have started to use data and samples from this Biomarker cohort, [19][20][21] the data and samples are available for additional projects and collaborative research. Requests for data and/or samples will be considered by a steering committee.…”

“…One of our analyses focussed on the stability of residual C-peptide production over time. 21 Because the MMTT procedure constitutes a burden to PWDs, an easier way to reliably assess residual C-peptide secretion is required, e.g. a simplified MMTT testing only 1 timepoint.…”