Characterization of residual β cell function in long-standing type 1 diabetes
Some patients with long-standing type 1 diabetes (T1D) maintain detectable levels of C-peptide. The quantitative and qualitative aspects of insulin secretion in these subjects has not been assessed, but may shed light on the basis for maintained β cell function. Our objective was to characterize insulin secretion in subjects with varying duration of T1D.
Data from mixed meal tolerance tests (MMTT) were collected in this cross-sectional study. We screened 58 subjects with T1D <1 year and 34 subjects with T1D >2 years, twenty of whom had previously participated in trials of anti-CD3 monoclonal antibody. Data from 38 historical non-diabetic controls was utilized. Insulin secretory rates were calculated from C-peptide levels from MMTTs. Patterns and rates of insulin secretion (ISR) were characterized along with relationships between ISR and clinical parameters.
Detectable C-peptide was present in 68% of subjects with T1D duration >2 years. ISR was negatively correlated with HgbA1c and insulin use. A decline in total insulin secretion was seen with increasing disease duration (p < 0.0001). More subjects with long duration of T1D had a delayed time to peak secretion compared to those with new onset T1D or non-diabetics. Insulin and glucagon secretory responses appeared unrelated.
Meal stimulated insulin secretory responses are seen in those with long standing T1D and detectable C-peptide. Delayed insulin secretory responses are more common in individuals with longer disease duration. Residual insulin secretory responses are associated with improved clinical parameters. This article is protected by copyright. All rights reserved.
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