miR-34a Regulates Lipid Droplet Deposition in 3T3-L1 and C2C12 Cells by Targeting LEF1.

Intramuscular fat (IMF) content plays a key role in improving the flavor and palatability of pork. The IMF content varies between species, breeds, and individuals of the same breed. Hence, it is necessary to elucidate the mechanisms of IMF deposition to improve pork quality. Herein, the IMF content in the longissimus dorsi muscles of 29 Laiwu pigs was detected and divided into two groups, the H group (IMF > 12%) and the L group (IMF < 5%). RNA sequencing analysis showed 24 differentially expressed (DE) miRNA, and GO and KEGG analysis demonstrated that the DE miRNAs were significantly enriched in lipid metabolic process, lipid storage, Wnt, mTOR, and PPAR signaling pathways. miR-34a was found to be increased in the H group and 3T3-L1-derived adipocytes, while Lef1 was decreased. Luciferase reporter assays demonstrated that Lef1 was a potential target of miR-34a . Mechanism analysis revealed that miR-34a could increase lipid droplet deposition in 3T3-L1 and C2C12 cells by dampening the suppressive function of Lef1 on the transcription of adipogenic markers (i.e., Pparg , Cebpa , Fabp4, and Plin1 ). Moreover, overexpression of miR-34a could enhance the lipid deposition in the co-culture system of 3T3-L1 and C2C12 cells as well as in C2C12 cells cultured with conditioned medium from the progress of adipocyte differentiation. Taken together, our study indicated that miR-34a was an important positive modulator in the regulation of fatty metabolism and fat deposition by inhibiting the suppressive function of Lef1 . These results might provide insight for the exploration of potential strategies to promote intramuscular fat deposition in livestock.