Mechanism of Action
Receptor Signaling
C-peptide binds to a distinct GPCR on cell surfaces that has not been fully characterized, activating pertussis toxin-sensitive Gi signaling. Downstream activation includes MAPK/ERK, PI3K/Akt, and eNOS pathways. eNOS activation in endothelial cells produces NO, explaining the vasodilatory effects. Akt activation promotes cell survival and anti-apoptotic gene expression.
Microvascular and Neuroprotective Effects
In diabetic models, C-peptide increases capillary blood flow, reduces endothelial cell apoptosis, and suppresses NF-kB-mediated inflammatory gene expression in the microvasculature. In neurons, C-peptide activates Na+/K+-ATPase and promotes neurotrophic signaling, improving nerve conduction velocity in peripheral neuropathy models. These effects are dependent on insulin acting in concert, C-peptide does not work effectively in hyperglycemia without concurrent insulin action.
Research Summary
Peripheral Neuropathy in T1D
HumanMultiple randomized trials in type 1 diabetes patients showed C-peptide replacement for 3-6 months significantly improved nerve conduction velocity, vibration perception threshold, and symptoms of peripheral neuropathy compared to placebo. These are the most robust human efficacy data for C-peptide and have driven clinical development.
Renal and Microvascular Protection
HumanC-peptide infusion in T1D patients improved renal blood flow and glomerular filtration rate. Urinary albumin excretion (a microvascular injury marker) decreased with C-peptide treatment in some trials. These renal effects suggest C-peptide opposes diabetic nephropathy progression.
Non-Diabetic Applications
AnimalBeyond diabetes, C-peptide shows cytoprotective effects in ischemia-reperfusion models, reduces atherosclerotic plaque formation in animal studies, and demonstrates neuroprotective activity in spinal cord injury models. These findings suggest potential applications extending beyond type 1 diabetes.
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Research Protocols
| Goal | Dose | Frequency | Route |
|---|---|---|---|
| Neuropathy research | 600 pmol/kg/h | Continuous SC infusion for weeks | Subcutaneous pump |
| Acute vascular studies | 600 pmol/kg/h | Short IV infusion | Intravenous |
C-peptide research primarily targets type 1 diabetes patients lacking endogenous C-peptide. Effects in non-deficient individuals are less established.
Interactions
Safety Profile
C-peptide has been well tolerated in all Phase II trials with no dose-limiting toxicity identified. No significant hypoglycemic risk exists as C-peptide is not insulin. Immunogenicity has not been an issue in trials using native human sequence. The primary limitation is the need for continuous subcutaneous delivery due to the 30-35 minute half-life.
References
- [1]Wahren J, et al. C-peptide and the pathophysiology of microvascular complications of type 1 diabetes. Exp Diabetes Res. 2012.
- [2]Ekberg K, et al. C-peptide replacement therapy and sensory nerve function in T1DM neuropathy. Diabetes Care. 2003;26(11):2943-2948.
- [3]Hills CE, Brunskill NJ. Intracellular signalling by C-peptide. Exp Diabetes Res. 2008.