[Overexpression of CGRP improves peripheral neuropathy in diabetic mice]

Objective To observe the effect of calcitonin gene-related peptide (CGRP) on peripheral neuropathy in diabetic mice, and to explore whether overexpressed CGRP improves peripheral neuropathy in diabetic mice. Methods Diabetic mouse model was induced by intraperitoneal injection of streptozotocin (STZ). The mice were randomly divided into 4 groups according to their body mass and blood glucose: normal control group, model group, Ad-CGRP group and Ad negative control group. The mice in the Ad-CGRP group and the Ad-negative control group were intramuscularly injected with adenovirus in the muscles of left hind limb. The mice in the normal group and the model group were injected with equal volume of normal saline. After 4 weeks of administration, the expression of CGRP mRNA was detected by real-time quantitative PCR. The expression of CGRP protein was detected by Western blot analysis. The latency of pain was measured by hot plate test. The motor nerve conduction velocity (MNCV) was measured by physiological signal acquiring system. The nerve blood flow was monitored with Laser Doppler Flowmetry (LDF). Results Compared with the normal group, the mRNA and protein levels of CGRP in the model group were reduced, the level of glucose was significantly raised, the latency of pain was extended, the MNCV and the nerve blood flow were decreased. Compared with the model group, the mRNA and protein levels of CGRP in the Ad-CGRP group were significantly increased, the latency of pain was shortened, the MNCV and the nerve blood flow was increased. There was no significant change in the Ad-negative control group. Conclusion Overexpression of CGRP may ameliorate diabetic peripheral neuropathy by expanding blood vessel and increasing blood flow.