Effects of ACAT2 gene on milk fat synthesis in bovine mammary epithelial cells

Objective Acyl-CoA cholesterol acyltransferase 2 (ACAT2) is a key enzyme involved in cholesteryl ester synthesis. This study aimed to elucidate its regulatory mechanism in milk fat synthesis in bovine mammary epithelial cells (bMECs).

Method A lactation model of bMECs was established to characterize the temporal expression pattern of ACAT2. Subsequently, ACAT2 overexpression and interference experiments were performed in bMECs. The mRNA expression levels of genes related to milk fat synthesis, cell proliferation, and apoptosis were analyzed by qRT-PCR. In addition, cell proliferation rate, apoptosis rate, and intracellular concentrations of triacylglycerol (TAG) and cholesteryl esters (CE) were measured.

Result Overexpression of ACAT2 significantly upregulated the mRNA expression of key milk fat synthesis-related genes, including ACACA, FASN, SREBP1, and SCD1 (P < 0.05). Meanwhile, the expressions of the proliferation-related gene PCNA (P<0.01) and the anti-apoptotic gene BCL2 (P<0.05) were significantly increased (P < 0.01), whereas the expression of the apoptosis-related gene BAX was significantly decreased (P < 0.05). At the phenotypic level, ACAT2 overexpression resulted in a significant increase in intracellular TAG and CE concentration (P < 0.01), and an enhanced cell proliferation rate (P < 0.05). In contrast, interference with ACAT2 expression produced opposite effects.

Conclusion ACAT2 acts as a key gene promoting milk fat synthesis in bMECs. By promoting cell proliferation, suppressing apoptosis, and enhancing the apoptosis-related gene expression, ACAT2 facilitates intracellular lipid accumulation. These findings provide a basis for elucidating the molecular mechanisms underlying milk fat synthesis and for molecular breeding in dairy cattle.