Chronic treatment with D-chiro-inositol prevents autonomic and somatic neuropathy in STZ-induced diabetic mice

Methods: Streptozotocin-induced (STZ) diabetic mice were treated by oral gavage for 60 days with DCI (20 mg/kg/12 h) or saline (NaCl 0.9%; 0.1 ml/10 g/12 h; Diab) and compared with euglycaemic groups treated with saline (0.1 ml/10 g/12 h; Eugly). We compared the response of the isolated sciatic nerve, corpora cavernosa or vas deferens to electrical stimulation. Results: The electrically evoked compound action potential of the sciatic nerve was greatly blunted by diabetes. The peak-to-peak amplitude (PPA) was decreased from 3.24 +/- 0.7 to 0.9 +/- 0.2 mV (p < 0.05), the conduction velocity (CV) of the first component was reduced from 46.78 +/- 4.5 to 26.69 +/- 3.8 ms (p < 0.05) and chronaxy was increased from 60.43 +/- 1.9 to 69.67 +/- 1.4 ms (p < 0.05). These parameters were improved in nerves from DCI-treated mice (p < 0.05). PPA in the DCI group was 5.79 +/- 0.8 mV (vs. 0.9 +/- 0.2 mV-Diab; p < 0.05) and CV was 45.91 +/- 3.6 ms (vs. 26.69 +/- 3.8 ms-Diab; p < 0.05). Maximal relaxation of the corpus cavernosum evoked by electrical stimulation (2-64 Hz) in the Diab group was 36.4 +/- 3.8% compared to 65.4 +/- 2.8% in Eugly and 59.3 +/- 5.5% in the DCI group (p < 0.05). Maximal contraction obtained in the vas deferens was 38.0 +/- 9.2% in Eugly and 11.5 +/- 2.6% in Diab (decrease of 69.7%; p < 0.05), compared to 25.2 +/- 2.3% in the DCI group (p < 0.05 vs. diabetic). Electron microscopy of the sciatic nerves showed prevention of neuronal damage. Conclusions: DCI has a neuroprotective action in both autonomic and somatic nerves in STZ-induced DN.