FATP4 Switches Cellular Lipid Utilization via the PI3K-AKT Pathway in Goat Preadipocytes

The role of fatty acid transporter 4 (FATP4) in regulating lipid metabolism has been well studied. However, how it affects IMF deposition, especially in goats, remains poorly understood. Here, we cloned the whole coding sequence of the goat FATP4 gene and revealed its closest affinity to sheep by amino acid sequence blast analysis. In addition, we found that the FATP4 reached its highest expression level at day 6 of goat preadipocyte differentiation in vitro. Functionally, in cultured goat intramuscular preadipocytes, siRNA-induced FATP4 knockdown dramatically raised the mRNA expression of lipogenesis-related genes and encouraged lipid deposition. At the same time, FATP4 deficiency inhibited cell proliferation and significantly decreased apoptosis. Unexpectedly, although the overexpression of FATP4 promoted cell proliferation and suppressed apoptosis, it only slightly decreased cellular lipid deposition in goat intramuscular preadipocytes. For RNA-seq (performed on pooled cell samples with three technical replicates), a total of 467 differential genes (DEGs) were identified after silencing of FATP4 in goat preadipocytes, including 47 upregulated genes and 420 downregulated genes. These DEGs were mainly enriched in the signaling pathways of Focal adhesion, HIF-1, and PI3K-Akt by KEGG analysis. To validate these findings, knockdown of FATP4 increased the expression of phosphatidylinositol 3-kinase (PI3k) and vice versa. Convincingly, we rescued the phenotype observed in FATP4 knockout goat preadipocytes by blocking the PI3k-Akt signaling pathway with an AKT inhibitor (LY294002). In summary, in our in vitro model, FATP4 plays a crucial role in directing fatty acids toward cell proliferation (prioritized over cellular lipid deposition) via the PI3K-Akt signaling pathway in goat intramuscular preadipocytes. These findings provide preliminary mechanistic insights into the regulatory network of IMF formation at the cellular level, and offer theoretical clues for future research aimed at enhancing meat quality from the standpoint of IMF deposition.