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Insulin production may persist decades after onset of type 1 diabetes
Wang L. Diabetes Care. 2012;35:465-470.
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Decades after the onset of type 1 diabetes, C-peptide production persists and beta-cell functioning appears to be preserved in some patients years after apparent loss of pancreatic function, according to data collected using an ultrasensitive assay. Results are published in the March issue of Diabetes Care.
The ultrasensitive assay found that 10% of patients with type 1 diabetes duration of 3 to 4 decades still produced C-peptide.
Serum C-peptide levels and beta-cell function were measured in 182 patients with type 1 diabetes using ultrasensitive assay. Compared with standard assays, the ultrasensitive assay is 22 times more sensitive, with a lower detection limit of 1.5 pmol/L.
Regression analysis was used to determine the relationship between C-peptide production and disease duration, age at onset, sex and autoantibody titers.
Four additional patients were serially studied for up to 20 weeks to analyze C-peptide levels and functioning, according to the researchers.
Among these patients, samples demonstrating hyperglycemia (n=12) were associated with higher C-peptide levels vs. those showing normoglycemia (n=50). Similar findings were reported in the larger sample of 182 patients, according to the researchers.
Three patients who were serially followed up to 20 weeks had three different C-peptide ranges (extremely low, low and moderate) that demonstrated a linear relationship between glycemic levels and C-peptide. According to the researchers, this suggests that beta cells remain functional, even in those patients with low C-peptide output.
In the larger sample, 10% of patients had C-peptide 31 to 40 years after disease onset; percentages were higher at shorter duration, according to the assay. Residual beta-cell function was indicated by levels as low as 2.8 pmol/L that responded to hyperglycemia with increased C-peptide production.
According to other analyses, beta cells were capable of functioning, even if C-peptide production was formerly undetectable. In addition, disease duration (beta cells=–2.721; P=.005) and zinc transporter 8 autoantibody levels (beta cells=0.127; P=.015) were significantly associated with C-peptide production.
“Although some studies have shown that adult-onset diabetes confers a more benign course, subjects in this study with onset at >40 years of age showed a more rapid loss of C-peptide levels despite relative short disease duration,” the researchers wrote.
Based on their findings, the researchers said patients with low C-peptide levels or advanced disease should not be excluded from clinical trials or viewed as having complete islet cell destruction.
Disclosure: The researchers report no relevant financial disclosures.
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