Discussion on Therapeutic Effect of ALA on Diabetic Peripheral Neuropathy rats from mitochondrial transport

Abstract

Abstract Purpose To investigate the AMPK/CREB pathway–mediated effect of alpha-lipoic acid (ALA) on the sciatic nerve of rats with diabetic peripheral neuropathy (DPN) and to attempt to elucidate the underlying mechanism. Methods In vivo experiment, healthy male Sprague-Dawley (SD) rats were induced by high-carbohydrate/high-fat diet and intraperitoneal injection of streptozotocin (STZ) (30 mg·kg− 1) to induce diabetes. The diabetes SD rats were randomly divided into DPN group and alpha lipoic acid (ALA) group (n = 15). The other 15 SD rats were set as Control group. Then Control group and DPN group received the same amount of normal saline by intragastric administration, and ALA groups received ALA intervention every day for 12 weeks. Motor nerve conduction velocity (MNCV) and Paw Withdrawal Threshold (PWT) were detected. The morphological changes were observed by HE staining in sciatic nerves. Kinesin family member 5A (KIF5A), Dynein Cytoplasmic 1 Intermediate Chain 2 (DYNC1I2), phosphorylated Adenosine 5'-monophosphate (AMP) activated protein kinase (p-AMPK), Adenosine 5'-monophosphate (AMP) activated protein kinase (AMPK), phosphorylated cAMP responsive element binding protein(p-CREB) and cAMP responsive element binding protein(CREB)were observed by immunofluorescence assay and Western blot. In the vitro cell experiment, the NSC34 cells injury model was established by treating with 50 mmol·L− 1 of high glucose and 250 µmol·L− 1 of palmitic acid sodium. NSC34 cells were randomly divided into Control group, Model group and alpha lipoic acid intervention group (ALA group). ALA group was given corresponding ALA for 24 hours of intervention. The axon changes were observed by measured neuron axon length in NSC34 cells. KIF5A, DYNC1I2, p-AMPK,AMPK, p-CREB and CREB were observed by immunofluorescence assay and Western blot. Results ALA improved the MNCV and PTW of rats with DPN and reduced their mechanical pain threshold. AMPK was activated by ALA. p-CREB, KIF5A expression was upregulated, while DYNC1I2 expression was downregulated. ALA regulates mitochondrial transport in peripheral nerve. Conclusion ALA activates CREB and KIF5A through AMPK, regulates positive mitochondrial transport, protects axons, and attenuates DPN.