No abstract

Background/Aims: Skeletal muscle atrophy is an important health issue and can impose tremendous economic burdens on healthcare systems. Glucocorticoids (GCs) are well-known factors that result in muscle atrophy observed in numerous pathological conditions. Therefore, the development of effective and safe therapeutic strategies for GC-induced muscle atrophy has significant clinical implications. Some natural compounds have been shown to effectively prevent muscle atrophy under several wasting conditions. Dihydromyricetin (DM), the most abundant flavonoid in Ampelopsis grossedentata, has a broad range of health benefits, but its effects on muscle atrophy are unclear. The purpose of this study was to evaluate the effects and underlying mechanisms of DM on muscle atrophy induced by the synthetic GC dexamethasone (Dex). Methods: The effects of DM on Dex-induced muscle atrophy were assessed in Sprague-Dawley rats and L6 myotubes. Muscle mass and myofiber cross-sectional areas were analyzed in gastrocnemius muscles. Muscle function was evaluated by a grip strength test. Myosin heavy chain (MHC) content and myotube diameter were measured in myotubes. Mitochondrial morphology was observed by transmission electron microscopy and confocal laser scanning microscopy. Mitochondrial DNA (mtDNA) was quantified by real-time PCR. Mitochondrial respiratory chain complex activities were examined using the MitoProfile Rapid Microplate Assay Kit, and mitochondrial membrane potential was assessed by JC-1 staining. Protein levels of mitochondrial biogenesis and dynamics markers were detected by western blotting. Myotubes were transfected with siRNAs targeting peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α), mitochondrial transcription factor A (TFAM) and mitofusin-2 (mfn2) to determine the underlying mechanisms. Results: In vivo, DM preserved muscles from weight and average fiber cross-sectional area losses and improved grip strength. In vitro, DM prevented the decrease in MHC content and myotube diameter. Moreover, DM stimulated mitochondrial biogenesis and promoted mitochondrial fusion, rescued the reduced mtDNA content, improved mitochondrial morphology, prevented the collapse in mitochondrial membrane potential and enhanced mitochondrial respiratory chain complex activities; these changes restored mitochondrial function and improved protein metabolism, contributing to the prevention of Dex-induced muscle atrophy. Furthermore, the protective effects of DM on mitochondrial function and muscle atrophy were alleviated by PGC-1α siRNA, TFAM siRNA and mfn2 siRNA transfection in vitro. Conclusion: DM attenuated Dex-induced muscle atrophy by reversing mitochondrial dysfunction, which was partially mediated by the PGC-1α/TFAM and PGC-1α/mfn2 signaling pathways. Our findings may open new avenues for identifying natural compounds that improve mitochondrial function as promising candidates for the management of muscle atrophy.

Gliomas are the most common and aggressive brain tumors, and a poor prognosis is correlated with its World Health Organization (WHO) grade. MicroRNAs (miRNAs) may serve as diagnostic and prognostic biomarkers in gliomas. In the present study, we collected plasma samples from patients with gliomas to evaluate the expression of miR-122 and analyzed the role of miR-122 in the diagnosis and prognosis of gliomas. We found that the expression of miR-122 in the plasma of patients with gliomas was significantly down-regulated compared to that in healthy individuals. In addition, the expression of miR-122, which was significantly correlated with WHO grade, decreased along with the development of gliomas. A receiver operating characteristic curve analysis showed high sensitivity and specificity of miR-122 for diagnosing gliomas (sensitivity 91.9%; specificity 81.1%; area under the curve 0.939). Finally, we found that lower expression of miR-122 was correlated with poor prognosis, and miR-122 was an independent prognostic parameter indicating poor prognosis for gliomas. In conclusion, our results showed that plasma miR-122 expression might act as a diagnostic and prognostic biomarker for gliomas.

MicroRNAs (miRs) participate in the development of several cancers. miR-361-5p suppresses the proliferation of hepatocellular carcinoma (HCC) cells. However, its function and potential underlying mechanism of action in the chemoresistance of HCC remains unknown. Therefore, cisplatin (DDP)-resistant HCC cells were used to study the role and potential mechanism of action of miR-361-5p in HCC resistance to chemotherapy. TargetScan software and dual-luciferase reporter assays were used to determine whether MAPK kinase kinase 9 (MAP3K9) is a target gene of miR-361-5p. Subsequently, reverse transcription-quantitative PCR and western blot analyses demonstrated that miR-361-5p mimic decreased MAP3K9 expression levels in Huh7 cells and this change was reversed by transfection with the MAP3K9-plasmid. In addition, compared with THLE-2 cells, miR-361-5p was downregulated, while MAP3K9 was upregulated in Huh7 cells. MAP3K9 also reversed the miR-361-5p-induced HCC cell apoptosis. A DDP-resistant cell line, Huh7/DDP, was established and MTT analysis revealed that the IC 50 value of DDP treatment in Huh7/DDP cells was higher compared with that in Huh7 cells. miR-361-5p expression was lower in Huh7/DDP cells compared with that in Huh7 cells. Similarly, miR-361-5p downregulated the expression levels of MAP3K9 in Huh7/DDP cells. Furthermore, MAP3K9 reversed miR-361-5p-induced sensitivity of Huh7/DDP cells to DDP and miR-361-5p induced Huh7/DDP cell apoptosis. Therefore, the findings of the present study demonstrated that the miR-361-5p/MAP3K9 axis may serve as a new potential biomarker and therapeutic target for DDP-resistant HCC.