SIRT5 Regulates Lipid Deposition in Goat Preadipocytes via PI3K-Akt and MAPK Signaling Pathways

Silent Information Regulator 5 (<i>SIRT5</i>) has been established as a crucial regulator of cellular alanylation modification. Furthermore, accumulating evidence suggests that <i>SIRT5</i> plays a significant regulatory role in key metabolic pathways, including glycolysis, the tricarboxylic acid (TCA) cycle, and fatty acid oxidation, all of which are closely associated with cellular lipid metabolism. Despite these advancements, the specific role of <i>SIRT5</i> in regulating intramuscular fat (IMF) deposition in goats, as well as the underlying molecular mechanisms, remains largely unexplored. In this study, we cloned the complete coding sequence of the goat <i>SIRT5</i> gene and, through amino acid sequence alignment, demonstrated its closest phylogenetic relationship with sheep. Additionally, we characterized the higher expression of <i>SIRT5</i> during the differentiation of goat intramuscular precursor adipocytes. The silencing of <i>SIRT5</i> by siRNA-mediated knockdown significantly upregulated the expression of lipogenesis-related genes and enhanced lipid deposition in goat intramuscular preadipocytes. Concurrently, <i>SIRT5</i> deficiency led to the inhibition of cell proliferation and a marked reduction in apoptosis. Interestingly, although overexpression of <i>SIRT5</i> promoted cell proliferation, it did not significantly alter lipid deposition in goat intramuscular precursor adipocytes. RNA sequencing (RNA-seq) analysis identified a total of 106 differentially expressed genes (DEGs) following <i>SIRT5</i> silencing in goat preadipocytes, predominantly involved in the Focal adhesion, HIF-1, PI3K-Akt, and MAPK signaling pathways by KEGG pathway enrichment analysis. Notably, we successfully reversed the phenotypic effects observed in <i>SIRT5</i> knockdown goat precursor adipocytes by inhibiting the PI3K-Akt and MAPK signaling pathways using the AKT inhibitor LY294002 and the p38 MAPK pathway inhibitor PD169316, respectively. In conclusion, our findings demonstrated that <i>SIRT5</i> may modulate intramuscular fat deposition in goats through PI3k-Akt and MAPK signaling pathways. These results expand the gene regulatory network associated with IMF formation and provide a theoretical foundation for improving meat quality by targeting IMF deposition.