Preventive Effects of the Chinese Herbal Medicine Prescription Tangkuei Decoction for Frigid Extremities on Sciatic Neuropathy in Streptozotocin-Induced Diabetic Rats

Ischemia and hypoxia are important physiological changes in diabetic peripheral neuropathy (DPN). Chinese herbal medicine prescription Tangkuei Decoction for Frigid Extremities (TDFE) is useful for increasing blood flow. To help determine whether TDFE could protect the peripheral nerves of diabetic patients from the degeneration caused by high blood glucose, TDFE was administered to streptozotocin-induced diabetic rats for 6 or 12 weeks. Plantar thermal stimulation reaction time thresholds, sciatic nerve conduction velocities, and the levels of HIF-1α mRNA, HIF-1α protein, VEGF protein, and the endothelial marker vWF in sciatic nerves were measured at the end of the sixth and twelfth weeks. The thermal thresholds and sciatic nerve conduction velocities of the rats differed after 12 weeks, and the sciatic nerves of the diabetic rats that were given TDFE displayed higher levels of HIF-1α protein, VEGF protein, and HIF-1α mRNA than those of the diabetic model rats. The results at 6 weeks differed from those at 12 weeks. These results suggest that the early preventive application of TDFE effectively delayed the development of DPN and that TDFE increased HIF-1α mRNA levels in the sciatic nerves of diabetic rats through 12 weeks of treatment.