PLIN5 Promotes Lipid Reconstitution in Goat Intramuscular Fat via the PPARγ Signaling Pathway

Intramuscular fat (IMF) content is an important factor of goat meat quality, which is related to the proliferation and differentiation of intramuscular preadipocytes. Perilipin 5 (PLIN5) is a lipid droplet-associated protein; however, the specific function and underlying mechanism of PLIN5 in goat IMF deposition are still unclear. In this study, overexpression of PLIN5 significantly enhanced apoptosis and reduced the proliferation of preadipocytes and also promoted cellular lipid deposition via both the upregulation of the expression of peroxisome proliferator-activated receptor gamma (PPARγ) and a significant increase in the expression of lipogenesis-related genes. The inhibition of PLIN5 then confirmed these results. Untargeted lipidomics sequencing identified a total of 34 differentially expressed lipids after PLIN5 overexpression in goat preadipocytes and analysis by KEGG pathway enrichment, which are mainly involved in the PI3K-AKT signaling pathway. The lipid omics findings also show that ceramides and lysophosphatidylinositol were significantly upregulated, e.g., Cer (d35:1), Cer (d18:2/22:1), LPI (18:0), and LPI (16:0), after overexpression of the PLIN5 gene. Higher expression of LPI (16:0) or LPI (18:0) may regulate lipid droplet accumulation by activating PPARγ. Rescue experiments with the PI3K-AKT inhibitor (LY294002) and the PPARγ inhibitor (GW9662) showed that the PI3K-AKT signaling pathway is involved in the regulation of cell proliferation, and PPARγ is involved in the regulation of lipid deposition. In conclusion, our findings demonstrate that PLIN5 regulates lipid reconstitution in goat intramuscular fat via PPARγ and PI3K-AKT signaling pathways. This regulation delivered theoretical support for improving meat quality from the aspect of IMF deposition.