Vol 8, No 5 (2007): Practical Diabetology
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Published online: 2007-05-24

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C-peptide reverses nociceptive neuropathy in type 1 diabetes

Hideki Kamiya, Weixian Zhang, Karin Ekberg, John Wahren, Anders A.F. Sima
Diabetologia Praktyczna 2007;8(5):178-187.

Abstract

We examined the therapeutic effects of C-peptide on established nociceptive neuropathy in type 1 diabetic BB/Worrats. Nociceptive nerve function, unmyelinated sural nerve fiber and dorsal root ganglion (DRG) cell morphometry, nociceptive peptide content, and the expression of neurotrophic factors and their receptors were investigated. C-peptide was administered either as a continuous subcutaneous replacement dose via osmopumps or a replacement dose given once daily by subcutaneous injection. Diabetic rats were treated from 4 to 7 months of diabetes and were compared with control and untreated diabetic rats of 4- and 7-month duration. Osmopump delivery but not subcutaneous injection improved hyperalgesia and restored the diabetesinduced reduction of unmyelinated fiber number (p < 0.01) and mean axonal size (p < 0.05) in the sural nerve. High-affinity nerve growth factor (NGF) receptor (NGFR-TrkA) expression in DRGs was significantly reduced at 4 months (p < 0.01). Insulin receptor and IGF-I receptor (IGF-IR) expressions in DRGs and NGF content in sciatic nerve were significantly decreased in 7-month diabetic rats (p < 0.01, 0.05, and 0.005, respectively). Osmopump delivery prevented the decline of NGFR-TrkA, insulin receptor (p < 0.05), and IGF-IR (p < 0.005) expressions in DRGs and improved NGF content (p < 0.05) in sciatic nerve. However, subcutaneous injection had only marginal effects on morphometric and molecular changes in diabetic rats. We conclude that C-peptide exerts beneficial therapeutic effects on diabetic nociceptive neuropathy and that optimal effects require maintenance of physiological C-peptide concentrations for a major proportion of the day.

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