Tang Bi formula alleviates diabetic sciatic neuropathy via AMPK/PGC-1α/MFN2 pathway activation

Diabetic peripheral neuropathy (DPN) is one of the most common chronic complications of diabetes mellitus, which affects various regions of the nervous system. Tang Bi formula (TBF) has been proven effective for DPN, while the underlying mechanism remains unclarified. This study aimed to clarifiy the neurprotective mechanism of TBF intervention in DPN through animal and cell models. UHPLC/QTOF-MS and network pharmacology analysis were utilized to identify the bioactive components and potential targets of TBF. DPN models were established in rats and Schwann cells to evaluate the therapeutic effects of TBF. In the DPN rats, body weight, fasting blood glucose, mechanical withdrawal threshold (MWT), paw withdrawal latency (PWL), sciatic motor nerve conduction velocity (MNCV), and sciatic nerve blood flow were measured. Pathological sections of the sciatic nerve (SN) were also examined. In vitro experiments, the Schwann cells (SCs) were cultured in a medium containing 30 mM glucose and treated with TBF for 48 h. Cell viability was assessed using the CCK-8 assay. The degree of apoptosis was evaluated by flow cytometry. The mitochondrial membrane potential was determined using JC-1 staining, and the generation of ROS was measured using DCFH-DA staining. Moreover, the expression levels of proteins related to the AMPK-PGC-1α-MFN2 pathway in the SN and SCs were detected. A total of 11 bioactive components of TBF were identified through UHPLC/QTOF-MS and network pharmacology analysis. In vivo experiments, MWT and PWL were decreased in DPN rats, which were restored after TBF administered daily for 12 weeks, TBF significantly attenuated thermal hyperalgesia and mechanical allodynia, and improved nerve conduction velocities. Further histopathological observations indicated that treatment with TBF promoted the regeneration of the myelin sheath of the SN, increased the density of intraepidermal nerve fibers, effectively improved distal microcirculation disorders, and alleviated demyelination and axonal degeneration. In vitro experiments were conducted to evaluate the protective effect of TBF on high-glucose-induced dysfunction of SCs. The data showed that treatment with TBF significantly inhibited the apoptosis of SCs. Meanwhile, TBF exhibited apparent antioxidant capacity, reducing the accumulation of intracellular ROS, and ameliorating mitochondrial dysfunction. Western blot analysis revealed that TBF activated the AMPK-PGC -1α-MFN2 pathway and upregulated the protein expressions of p-AMPK (Thr172), PGC-1α, and MFN2, suggesting that the neuroprotective effect of TBF was associated with the activation of this pathway. TBF ameliorated DPN by rectifying mitochondrial dynamic imbalance and modulating the activation of the AMPK-PGC-1α-MFN2 pathway. This, in turn, promoted neurogenesis and alleviated peripheral nerve lesions. Thus, this study demonstrated the therapeutic potential of TBF for DPN.