Effect Of Neurotrophic Factors On Diabetic Neuropathy In Rats: An Experimental Study

ObjectiveTo further study the effect of nerve growth factor ( NGF) and vascular endo-thelial growth factor ( VEGF) (two neurotrophic factors) on diabetic neuropathy.MethodsStreptozotocin - induced diabetic rats ( SD rats) were treated with NGF (800u. kg-1, d-1) after diabetic model formation. The morphology of sciatic nerve was investigated by toluidine blue stain and electron microscope. The enzyme cytochemical reaction and the enzyme activity ( Average gray value) of AChE in motor end-plates and SDH in muscle fibers were used to investigate in tibial anterior muscles of rats. Electron microscope was used to observe the change of motor neuron of anterior horn in spinal cord of diabetic rats. Western blot and histochemistry methods were used to detect the expression (IOD Integrated optical density) of VEGF in sciatic nerves of diabetic rats.ResultThe pathologic change of sciatic nerve was found by electron microscope in two - week diabetic rat. Myelin size and axon size in sciatic nerve increased after 3 and 6 months treated with NGF comparing with diabetic group untreated with NGF. Mylin size of NGF group, diabetic group in 3 months were 47.48 ± 11.84μm2 and 44.86 ± 12. 28μm2 (p<0.05) respectively. Mylin size of NGF group, diabetic group in 6 months were 57. 76 ± 10. 33μm2 and 46. 34 ±11. 57μm2(p <0. 05 ) respectively. Axon size of NGF group, diabetic group in 3 months were 22. 86 ±9. 59μm2 and 19. 86 ±7. 78μm2(p <0. 05) respectively;Axon size of NGF group, diabetic group in 6 months were 23.90 ± 7.and 20. 29 ± 6. 67μm2 (p < 0. 05 ) respectively. NGF treatment after 6 monthsdecreased demyelinating neuropathy in sciatic nerve.The area of skeletal muscle fiber and the SDH activity in diabetic group ( the red fiber 1665. 34 ± 127. 19μm2; the intermidiate fiber 2068. 89 ± 245. 52μm2 ;the white fiber 2428.73 ±489.47μm2; the SDH activity in the red fiber 83. 46 ± 23. 60 ) decreased significandy compared with that in the control group ( the red fiber 2977. 33 ± 736. 37μm2; the intermidiate fiber 3831. 95 ± 1171. 93μm2; the white fiber 5459. 24 ± 1049.28μm2; the SDH activity in the red fiber 33.40 ± 17. 93 ) ( p < 0. 01) respectively. The area of skeletal muscle fiber and SDH activity of the red fiber in NGF group ( the red fiber 1604. 67 ± 192. 14μm2;the intermidiate fiber 2208. 27 ±489. 31μm2; the white fiber 2345. 78 ±587.45μm2) decreased compared with control group (p <0. 01) , the red fiber SDH activity in NGF group (57. 44 ±28. 29) increased significantiy compared with that of diabetic group( p < 0. 05 ). The area of motor end - plates and AChE activity in diabetic group (the motor end -plates in the red fiber 389. 18 ±194. 73μm2 and 127. 69 ± 3. 82; the motor end - plates in the white fiber 449.10 ± 189. 04μm2 and 127.40 ±6.9) decreased significandy compared with that in control group (the motor end - plates in the red fiber 721. 14 ± 13. 97μm2 and 97. 30 ±8. 59; the motor end - plates in the white fiber 1964. 09 ± 219.23μm2 and 104.75 ± 3. 23) (p <0. 01) , the AChE activity in NGF group (the motor end - plates in the red fiber 109.14 ± 10.29; the motor end - plates in the white fiber 117. 82 ±11.12) increased significandy compared with that in diabetic group. The difference between the area of motor end - plates in diabetic group and NGF group had no significance. Motor neuron of anterior horn in spinal cord in NGF group had recovery changes compared with that of diabetic group.The expression of VEGF in diabetic sciatic nerves in 2-week-group (60621.15 ± 15776. 24) increased compared with control group (15585. 37 ± 4257.25) and NGF group(8734.90 ±4873.33 ) (p < 0.01). The expression of VEGF in 6-month-group diabetic rats (19398. 97 ± 4176. 67 ) also decreasedcompared with 2-week-group diabetic rats and 6-month NGF group (34526.68 +1811.20) and control group (57797.11+6837.98) (p <0.01). The difference between the expression of VEGF in 2-week NGF group and control group had no sig...