[Mechanism of electroacupuncture in protecting sciatic nerve of diabetic rats based on transcriptomics techniques]

To observe the protective effect of electroacupuncture(EA) on the structure and function of sciatic nerve in diabetic rats, so as to explore its mechanism in delaying diabetic peripheral neuropathy (DPN).

Thirty SPF-grade male Sprague-Dawley (SD) rats were randomly divided into normal group, model group, and EA group (n=10). Rats in the model group and EA group were intraperitoneally injected with streptozotocin (STZ, 60 mg/kg) to induce diabetes mellitus (DM) models. On the day after DM modeling, rats in the EA group received pre-intervention with EA (2 Hz, 10 min per session) at bilateral "Zusanli" (ST36), "Sanyinjiao" (SP6), "Pishu" (BL20), and "Shenshu" (BL23) acupoints. 3 times a week for 8 weeks. Rats in the normal group and model group only received fixation treatment. Before intervention, and at the 4 and 8 week after intervention, body weight, random blood glucose, thermal withdrawal latency (TWL), and mechanical withdrawal threshold (MWT) were measured. Following 8 weeks of intervention, the contents of total cholesterol (TC), triglycerides (TG), and non-esterified fatty acids (NEFA) in serum were determined using biochemical kits;the sensory nerve conduction velocity (SCV) and motor nerve conduction velocity (MCV) of the sciatic nerve were detected;the ultrastructural changes of the sciatic nerve were observed by transmission electron microscopy;transcriptome sequencing was used to screen differentially expressed genes (DEGs) for bioinformatics analysis;and qPCR was used to detect the mRNA expression levels of DEGs including adiponectin (Adipoq), aquaporin 7 (Aqp7), stearoyl-CoA desaturase 1 (Scd), and perilipin 4 (Plin4).

Compared with the normal group, the model group showed significantly decreased body weight, TWL, MWT, SCV, and MCV (P<0.01), significantly increased random blood glucose, serum TC, TG, and NEFA contents (P<0.01), and accompanied by sciatic nerve ultrastructural damage (axon dispersion, myelin sheath separation). After EA intervention, the above indicators and ultrastructural damage were significantly reversed (P<0.01). A total of 186 DEGs were screened. Gene Ontology (GO) analysis showed that these DEGs were mainly involved in biological processes such as glucocorticoid response and fatty acid beta-oxidation. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis and gene set enrichment analysis (GSEA) indicated that the DEGs were significantly enriched in the peroxisome proliferator-activated receptor (PPAR) signaling pathway, which changed from an inhibited state to an activated state after EA intervention. Through the identification of core pathway genes, the PPAR-γ pathway and its downstream target genes (Adipoq, Aqp7, Scd, Plin4) were finally identified as key regulatory targets. qPCR verification showed that compared with the normal group, the mRNA expressions of Adipoq, Aqp7, Scd, Plin4 in the model group were significantly down-regulated (P<0.01), while their expressions were significantly reversed after EA intervention (P<0.01), and this change trend was consistent with the results of transcriptome sequencing.

EA may activate the PPAR-γ signaling pathway, synergistically up-regulate the mRNA expressions of Adipoq, Aqp7, Scd, and Plin4, thereby remodeling the homeostasis of glucose and lipid metabolism, significantly improving the structure and function of the sciatic nerve, and delaying the progression of DM to DPN.