Electroacupuncture Promotes Skeletal Muscle Myogenic Differentiation and Protein Synthesis by Reducing Let-7c-5p Levels.

Objective: Acupuncture with low-frequency electrical stimulation (Acu-LFES) can attenuate muscle atrophy. Previous studies have found that Acu-LFES reduces the let-7 family in serum exosomes. This study explored the effects of let-7c-5p in chronic kidney disease (CKD) muscle atrophy. Methods: A total of 24 mice were randomly divided into control group, Acu-LFES group, CKD group, and CKD/Acu-LFES group (n = 6/group). The 5/6 nephrectomy was performed to establish the CKD model in mice. After 20 weeks, the Acu-LFES group and CKD/Acu-LFES group were treated with electroacupuncture at the "Zu San Li" and "Yang Ling Quan" bilaterally points for 15 minutes once. Surface sensing of translation (SUnSET), Reverse Transcription-quantitative PCR(RT-qPCR), immunofluorescence staining, and Western blot were performed to examine each group's state of protein production and myogenic differentiation. we knocked down or exogenously expressed let-7c-5p in C2C12 myoblast, RT-qPCR, and Western blot were performed to examine protein synthesis and myogenic differentiation. Results: The protein expressions of MyoD and Myogenin (MyoG) were decreased in the CKD group (P = .029 and P = .026) concomitant with a decrease in the muscle fiber cross-sectional area. Acu-LFES prevented muscle atrophy in CKD mice. The protein expressions of MyoD and MyoG were increased in the CKD/Acu-LFES group (P = .006 and P = .001). In muscle of CKD mice, IGF1, IGF1R, IRS1, phosphorylated mTOR and P70S6K proteins were decreased compared with control muscle (P = .001, P = .007, P < .001, P < .001 and P < .001), whereas atrogin-1/MAFbx and MuRF1 were dramatically increased (P < .001). Acu-LFES reversed these phenomena, indicating IGF1/mTOR signaling pathway was induced to promote muscle protein synthesis and myogenic differentiation. Meanwhile, Acu-LFES caused a decrease of let-7c-5p in skeletal muscle of CKD mice (P = .034). Inhibiting let-7c-5p promoted C2C12 myogenic differentiation (P = .002 and P = .001) and increased IGF1, IGF1R, IRS1 levels while upregulating mTOR and P70S6K phosphorylation (P < .001, P = .002, P = .009, P < .001 and P = .007). It is interesting to observe that the abundance of atrogin-1/MAFbx and MuRF-1 was unaffected by let-7c-5p (P > .05). Conclusions: Acu-LFES-reduced expression of let-7c-5p can ameliorate CKD-induced skeletal muscle atrophy by upregulating the IGF1/mTOR signaling pathway, which enhances skeletal muscle protein synthesis and myogenic differentiation. Let-7c-5p may be a potential regulator for the treatment of muscle atrophy.

CCN1 induces adipogenic differentiation of fibro/adipogenic progenitors in a chronic kidney disease model.

Previous studies have shown that sarcopenic obesity is highly prevalent in patients with chronic kidney disease (CKD). Here, the association between CKD and sarcopenic obesity were investigated. The 5/6 nephrectomy was performed to establish CKD in mice. Fluorescence-activated cell sorting (FACS), quantitative real-time PCR, ELISA kits assay, immunohistochemistry, and cell proliferation assay were carried out to investigate the condition of muscle loss and fatty infiltration were in CKD mice and the origin of adipocytes. Muscle atrophy occurred and adipogenic gene expression, Perilipin and FABP4 were markedly increased in the hind limb muscle of CKD mice. Results indicated that fibro/adipogenic progenitors (FAPs) are the precursor of adipocytes in the muscle of CKD mice. Meanwhile, the content of extracellular matrix protein CCN1 was notably increased in serum of CKD patients with sarcopenic obesity which was also found in muscle and serum of CKD mice. CCN1 induced the differentiation of FAPs into adipocytes. These results suggest that CKD mice are susceptible to sarcopenic obesity. CCN1 may be a novel activator of the differentiation of FAPs in CKD muscle.

Puerarin suppresses macrophage M1 polarization to alleviate renal inflammatory injury through antagonizing TLR4/MyD88-mediated NF-κB p65 and JNK/FoxO1 activation.

BACKGROUND: Acute kidney injury (AKI) is a clinically common and serious renal dysfunction, characterized by inflammation and damage to tubular epithelial cells. Puerarin, an isoflavone derivative isolated from Pueraria lobata, has been proven to possess exceptional effectiveness in reducing inflammation. However, the effects and underlying mechanisms of puerarin on AKI remain uncertain. PURPOSE: This study investigated the possible therapeutic effects of puerarin on AKI and explored its underlying mechanism. STUDY DESIGN AND METHODS: The effects of puerarin on AKI and macrophage polarization were investigated in lipopolysaccharide (LPS)-induced or unilateral ureteral obstruction (UUO)-induced mouse models in vivo and LPS-treated macrophages (Raw264.7) in vitro. Additionally, the effects of puerarin on inflammation-related signaling pathways were analyzed. RESULTS: Administration of puerarin effectively alleviated kidney dysfunction and reduced inflammatory response in LPS-induced and UUO-induced AKI. In vitro, puerarin treatment inhibited the polarization of M1 macrophages and the release of inflammatory factors in Raw264.7 cells stimulated by LPS. Mechanistically, puerarin downregulated the activities of NF-κB p65 and JNK/FoxO1 signaling pathways. The application of SRT1460 to activate FoxO1 or anisomycin to activate JNK eliminated puerarin-mediated inhibition of JNK/FoxO1 signaling, leading to suppression of macrophage M1 polarization and reduction of inflammatory factors. Further studies showed that puerarin bound to Toll/interleukin-1 receptor (TIR) domain of MyD88 protein, hindering its binding with TLR4, ultimately resulting in downstream NF-κB p65 and JNK/FoxO1 signaling inactivation. CONCLUSIONS: Puerarin antagonizes NF-κB p65 and JNK/FoxO1 activation via TLR4/MyD88 pathway, thereby suppressing macrophage polarization towards M1 phenotype and alleviating renal inflammatory damage.