Long-acting C-peptide and neuropathy in type 1 diabetes: A 12-month clinical trial

OBJECTIVE Lack of C-peptide in type 1 diabetesmay be an important contributing factor in the development of microvascular complications. Replacement of native C-peptide has been shown to exert a beneficial influence on peripheral nerve function in type 1 diabetes. The aim of this study was to evaluate the efficacy and safety of a long-acting C-peptide in subjects with type 1 diabetes and mild to moderate peripheral neuropathy. RESEARCH DESIGN AND METHODS A total of 250 patients with type 1 diabetes and peripheral neuropathy received long-acting (pegylated) C-peptide in weekly dosages of 0.8 mg (n = 71) or 2.4 mg (n = 73) or placebo (n = 106) for 52 weeks. Bilateral sural nerve conduction velocity (SNCV) and vibration perception threshold (VPT) on the great toe were measured on two occasions at baseline, at 26 weeks, and at 52 weeks. Themodified Toronto Clinical Neuropathy Score (mTCNS) was used to grade the peripheral neuropathy. RESULTS Plasma C-peptide rose during the study to 1.8-2.2 nmol/L (low dose) and to 5.6- 6.8 nmol/L (high dose). After 52 weeks, SNCV had increased by 1.0 ± 0.24 m/s (P < 0.001 within group) in patients receiving C-peptide (combined groups), but the corresponding value for the placebo group was 1.2 ± 0.29 m/s. Compared with basal, VPT had improved by 25% after 52 weeks of C-peptide therapy (δ for combined C-peptide groups: 24.5 ± 1.0 mm, placebo group: 20.1 ± 0.9 mm; P < 0.001). mTCNS was unchanged during the study. CONCLUSIONS Once-weekly subcutaneous administration of long-acting C-peptide for 52 weeks did not improve SNCV, other electrophysiological variables, or mTCNS but resulted in marked improvement of VPT compared with placebo.