RESUMO
BACKGROUND: Mitochondrial dysregulation in skeletal myocytes is considered a major factor in aged sarcopenia. In this study, we aimed to study the effects of peroxisome proliferator-activated receptor gamma coactivator-1 alpha (PGC-1α) on Sestrin2-mediated mechanistic target of rapamycin complex 1 (mTORC1) in aged skeletal muscles. METHODS: C2C12 myoblasts were stimulated by 50 µM 7ß-hydroxycholesterol (7ß-OHC) to observe the changes of DNA damage, mitochondrial membrane potential (Δψm), mitochondrial ROS and PGC-1α protein. The PGC-1α silence in the C2C12 cells was established by siRNA transfection. The levels of DNA damage, Δψm, mitochondrial ROS, Sestrin2 and p-S6K1/S6K1 proteins were observed after the PGC-1α silence in the C2C12 cells. Recombinant Sestrin2 treatment was used to observe the changes of DNA damage, Δψm, mitochondrial ROS and p-S6K1/S6K1 protein in the 7ß-OHC-treated or PGC-1α siRNA-transfected C2C12 cells. Wild-type (WT) mice and muscle-specific PGC-1α conditional knockout (MKO) mice, including young and old, were used to analyse the effects of PGC-1α on muscle function and the levels of Sestrin2 and p-S6K1 in the white gastrocnemius muscles. Recombinant Sestrin2 was administrated to analyse its effects on muscle function in the old WT mice and old MKO mice. RESULTS: 7ß-OHC treatment induced DNA damage, mitochondrial dysfunction and decrease of PGC-1α protein in the C2C12 cells. PGC-1α silence also induced DNA damage and mitochondrial dysfunction in the C2C12 cells. Additionally, PGC-1α silence or 7ß-OHC treatment decreased the levels of Sestrin2 and p-S6K1/S6K1 protein in the C2C12 cells. Recombinant Sestrin2 treatment significantly improved the DNA damage and mitochondrial dysfunction in the 7ß-OHC-treated or PGC-1α siRNA-transfected C2C12 cells. At the same age, muscle-specific PGC-1α deficiency aggravated aged sarcopenia and decreased the levels of Sestrin2 and p-S6K1 in the white gastrocnemius muscles when compared to the WT mice. Recombinant Sestrin2 treatment improved muscle function and increased p-S6K1 levels in the old two genotypes. CONCLUSION: This research demonstrates that PGC-1α participates in regulating mitochondrial function in aged sarcopenia through effects on the Sestrin2-mediated mTORC1 pathway.
RESUMO
Polyploidy occurs naturally in fish; however, the appearance of these species is an occasional and gradual process, which makes it difficult to trace the changes in phenotypes, genotypes, and regulation of gene expression. The allotetraploid hybrids (4nAT) of red crucian carp (RCC; â) × common carp (CC; â) generated from interspecies crossing are a good model to investigate the initial changes after allopolyploidization. In the present study, we focused on the changes in the active sites of the testicular transcriptome of the allotetraploid by localization of RNA Pol II CTD YSPTSPS (phospho S5) using immunofluorescence and RNA-seq data via bioinformatic analysis. The results showed that there was no significant difference in signal counts of the RNA Pol II CTD (S5) between the different types of fish at the same stages, including RCC, CC, 2nF1, and 4nAT, which means that the number of transcriptionally active sites on germ cell chromosomes was not affected by the increase in chromosome number. Similarly, RNA-seq analysis indicated that in the levels of chromosomes and 10-kb regions in the genome, there were no significant changes in the highly active sites in RCC, 2nF1, and 4nAT. These findings suggest that at the beginning of tetraploid origin, the active transcriptome site of 4nAT in the testis was conserved in the regions of the genome compared to that in RCC and 2nF1. In conclusion, 4nAT shared a similar gene expression model in the regions of the genome with RCC and 2nF1 with significantly different expression levels.
