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Long-acting C-peptide fails to improve sural nerve conduction velocity in type 1 diabetes
In patients with type 1 diabetes, once-weekly subcutaneous injection of long-acting C-peptide for 52 weeks does not appear to improve sural nerve conduction velocity, other electrophysiologic variables or modified Toronto Clinical Neuropathy Score.
However, the injection did yield marked improvement in vibration perception response, according to the researchers.
John Wahren, MD, PhD, professor of clinical physiology at Karolinska Institutet in Stockholm, and colleagues evaluated 250 adults with type 1 diabetes and mild to moderate diabetic peripheral neuropathy enrolled from 32 clinical site in the United States, Canada and Sweden. Participants were randomly assigned to one of the following treatments: high-dose pegylated C-peptide (PEG-C-peptide; 2.4 mg; n = 73), low-dose PEG-C-peptide (0.8 mg; n = 71) or placebo (n = 106).
At baseline, 26 weeks and 52 weeks, sural nerve conduction velocity (SNCV) and vibration perception threshold (VPT) were measured.
Plasma levels of PEG-C-peptide varied in the low-dose group between 1.8 and 2.2 nmol/L and from 5.6 to 6.8 nmol/L in the high-dose group during the study.
In the low-dose group, there was an increase in SNCV after 52 weeks of 1.3 m/s (P < .005 within group) and an increase of 0.64 in the high-dose group (P < .025 within group). There was not a significant difference between these groups and placebo because of an unexpected improvement in SNCV in the placebo group (increase 1.19 m/s; P < .001 within group).
A gradual reduction in VPT was seen, suggesting improvement in participants receiving PEG-C-peptide. This decrease reached statistical significance compared with placebo after 52 weeks for both groups (low-dose, P < .003; high-dose, P < .02). After 52 weeks, participants in the low-dose group had decreased VPT by an average 31% compared with baseline, and the high-dose group had a reduction of 19%.
“The observed improvements in [initial] SNCV during the 12-month study period in subjects receiving PEG-C-peptide were significant within both treatment groups,” the researchers wrote. “However, a similar improvement was also observed in the placebo group. The differences in SNCV response for subjects treated with PEG-C-peptide or placebo were not statistically different, and the study thus failed to meet its primary endpoint.” – by Jennifer Byrne
Disclosure: Wahren reports having been an employee of Cebix Inc. at the time of the study. Please see the full study for a list of all other authors’ relevant financial disclosures.