Neuroprotective effect of diosgenin in a mouse model of diabetic peripheral neuropathy involves the Nrf2/HO-1 pathway

Diabetic peripheral neuropathy (DPN) is one of the most common chronic complications of diabetes. Diosgenin is a natural steroidal saponin with a variety of beneficial effects, including antidiabetic effects, and is a raw material for the synthesis of carrier hormones. In our study, we aimed to assess the antioxidant effects of diosgenin in diabetic mice.

Male C57 mice were fed a high-fat diet for 8 weeks and intraperitoneally injected with streptozotocin (STZ) at a dose of 100 mg/kg for 2 consecutive days. Eligible mice were divided into the normal control group (CON), diabetic group (DM), low-dose diosgenin (50 mg/kg) group (DIO50) and high-dose diosgenin (100 mg/kg) group (DIO100). Treatment was started 6 weeks after the induction of diabetes by STZ and continued for 8 weeks. Blood sugar and body weight were monitored dynamically. The behavioural effects of diosgenin were detected by a hot tail immersion test and paw tactile responses. HE staining was used to evaluate edema and degeneration of the sciatic nerve. The levels of SOD, MDA and GPx were tested according to the instructions of the respective kits. The levels of Nrf2, HO-1 and NQO1 were detected by immunofluorescence and Western blotting. Statistical analysis was performed using SPSS, and P < 0.05 was considered statistically significant.

Diosgenin decreased the blood glucose levels and increased the body weight of diabetic mice. There was a significant increase in the tail withdrawal latency of diabetic animals, and mechanical hyperalgesia was significantly alleviated after diosgenin treatment. Histopathological micrographs of HE-stained sciatic nerves showed improvement after diosgenin treatment. Diosgenin attenuated the level of MDA but increased the activities of SOD and GPx. Diosgenin increased the expression of Nrf2, HO-1 and NQO1.

Our results demonstrate that diosgenin can ameliorate behavioural and morphological changes in DPN by reducing oxidative stress. The Nrf2/HO-1 signalling pathway was involved in its neuroprotective effects.