Knockdown of LXRα Inhibits Goat Intramuscular Preadipocyte Differentiation

Goat intramuscular fat (IMF) content is mainly determined by the processes of intramuscular preadipocytes adipogenic differentiation and mature adipocyte lipid accumulation. However, the underlying regulators of these biological processes remain largely unknown. Here, we report that the expression of Liver X receptor alpha (LXR) reaches a peak at early stage and then gradually decreases during goat intramuscular adipogenesis. Knockdown of LXR mediated by two independent siRNAs significantly inhibits intramuscular adipocytes lipid accumulation and upregulates preadipocytes marker- preadipocyte factor 1 (pref1) expression. Consistently, siRNA treatments robustly decrease mRNA level of adipogenic related genes, including CCAAT enhancer binding protein alpha (Cebp), Peroxisome proliferator activated receptor gamma (Pparg), Sterol regulatory element binding protein isoform 1c (Srebp1c), Fatty acids binding protein (aP2) and Lipoprotein lipase (Lpl). Next, adenovirus overexpression of LXR does not affect intramuscular adipocytes adipogenesis manifested by Oil Red O signal measurement and adipogenic specific genes detection. Mechanically, we found that both CCAAT enhancer binding protein beta (Cebp) and Kruppel like factor 8 (Klf8) are potential targets of LXR, indicated by having putative binding sites of LXR at the promoter of these genes and similar expression pattern during adipogenesis comparing to LXR. Importantly, mRNA levels of Cebp and Klf8 are downregulated significantly in goat LXR knockdown intramuscular adipocyte. These results demonstrate that loss function of LXR inhibits intramuscular adipogenesis possibly through down-regulation of Cebp and Klf8. Our research will provide new insights into mechanical regulation of goat IMF deposition.