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Higher C-peptide levels may identify lower risk for hypoglycemia events in type 1 diabetes
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A C-peptide level of more than 20 pmol/L may indicate a lower risk for hypoglycemia among adults with type 1 diabetes, suggesting that these individuals may safely pursue tighter glycemic targets, according to findings published in Diabetic Medicine.
“Findings from [the Diabetes Control and Complications Trial] highlight that the benefit of persistent C-peptide may arise from allowing tighter glucose control with intensive treatment through protection from hypoglycemia,” Richard Oram, PhD, BMBCh, MRCP, a senior clinical instructor at the Institute of Biomedical and Clinical Science at the University of Exeter Medical School in the U.K., and colleagues wrote. “Although [the Diabetes Control and Complications Trial] provides clear evidence of benefit from preserved endogenous insulin secretion in an intensively treated trial setting, and studies of islet cell transplants show the clear benefit of restoring relatively large amounts of endogenous insulin secretion, the impact of preserved endogenous insulin in people with long-standing diabetes receiving usual clinical care is unclear.”
A standard mixed-meal tolerance test to assess C-peptide levels was undertaken by 221 adults who were diagnosed with type 1 diabetes before age 30 years. Oram and colleagues measured C-peptide from samples collected every half-hour for 2 hours after the test and identified 70 participants with C-peptide levels of more than 20 pmol/L, or “preserved” measures (mean age, 30.9 years; 59% women; mean age at diagnosis, 15.1 years), and 151 participants with C-peptide levels of less than 10 pmol/L, or “low” measures (mean age, 19.9 years; 43% women; mean age at diagnosis, 6.1 years). Participants also completed a questionnaire to establish how often they experienced hypoglycemia.
An average of 7.5 symptomatic hypoglycemic events per month was reported in the low C-peptide group compared with 5.9 events per month among the preserved C-peptide group (P < .001). Additionally, participants with low C-peptide levels experienced an average of 2.9 asymptomatic hypoglycemic events per month compared with an average of one event per month for those with preserved C-peptide levels. According to the researchers, based on incidence rate ratios (IRRs), symptomatic episodes and asymptomatic episodes were lower by 21% (OR = 0.79; 95% CI, 0.68-0.91) and 65% (OR = 0.35; 95% CI, 0.25-0.48), respectively, for those with preserved C-peptide levels vs. those with lower measures. These reductions in symptomatic events (IRR = 0.8; 95% CI, 0.68-0.84) and asymptomatic events (IRR = 0.39; 95% CI, 0.28-0.55) remained largely the same when excluding participants with more than 200 pmol/L C-peptide.
In addition to its effects on hypoglycemia, higher C-peptide levels appeared to be linked to smaller insulin requirements, as more daily insulin was needed by those with low C-peptide levels (0.81 U/kg) compared with those with preserved C-peptide levels (0.68 U/kg; P = .01).
“Our study suggests it may be possible to intensify treatment in adults with persistent C-peptide,” the researchers wrote. “Our study highlights the association of persistent high C-peptide with reduced hypoglycemia in adults. Additionally, it demonstrates that higher C-peptide does not always robustly associate with improved glycemic control and reduced complications rates.” – by Phil Neuffer
Disclosures: The authors report no relevant financial disclosures.
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