Objective. To explore the role of insulin-like growth factor 1 (IGF-1)gene expression abnormality in neurotrophic causes of diabetic peripheral neurophathy.Methods. Diabetes was induced in Sprague Dawley rats by alloxan. The parameters were measured as follows: IGF-1 mRNA by reverse transcriptase-polymerase chain reaction (RT-PCR); IGF-1 peptide by enzyme-linked immunosorbent assay (ELISA); electrophysiological parameters of nerves by evoked electromyogram; morphometric evaluation of sciatic nerves under light microscope and transmission electron microscope.Results. During early diabetic stage, IGF-1 mRNA [(0.430±0.031)vs. (0.370±0.016), P ＜0.01,(0.430 ± 0.031 ) vs. (0.280 ± 0.010) , P ＜0.001, respectively], IGF - 1 peptide contents [ (38.44 ± 3.60)ng/mgvs. (30.06±2.41) ng/mg, P ＜0.01, (38.44±3.6) ng/mgvs. (3.71 +2.70) ng/mg, P ＜0.001,respectively] in sciatic nerve tissue reduced in diabetic rats with hyperglycemia and varied with severity of diabetic state when compared with non-diabetic control rats, and further gradually down-regulated in the diabetic rats with duration of diabetes [IGF-1 mRNA (0. 320 ± 0. 021) ～ (0. 230 + 0. 060); IGF-1 peptide (28.80 ± 3.30) ～(19. 51 + 1.80)ng/mg]. Furthermore, they correlated with nerve functional (sensory nerve conduction velocity:r = 0. 741, P ＜0. 001; amplitude ofevokedpotential: r = 0. 716, P ＜0. 001, respectively)andstructuralabnormality (axonal areas r = 0. 81, P ＜ 0. 001 ) of sciatic nerve. No difference was found in the above parameters between diabetic rats with euglycemia and non-diabetic control group.Conclusion. IGF-1 gene expression in tissues was down-regulated from early diabetic stage, and varied with the severity and duration of diabetic state. The decrement in IGF-1 level might contribute to the initiation and development of diabetic neuropathy via autocrine or paracrine pathway.
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