Activation of Liver X Receptor (LXR) Enhances De Novo Fatty Acid Synthesis in Bovine Mammary Epithelial Cells

Liver X receptor (LXR) is a nuclear receptor and a known regulator of lipid synthesis in rodents; however, the role of LXR in the regulation of fatty acid synthesis in bovine mammary epithelial cells has not yet been defined. The objective of the study was to evaluate the effect of LXR activation on the de novo synthesis of fatty acids in bovine mammary epithelial cells (BME-UV). Bovine mammary epithelial cells were treated with T0901317 (T09), an LXR agonist. Treatment of BME-UV with T09 increased the transcription of ATP-binding cassette transporter-G1, an LXR target gene, without modifying LXRα mRNA abundance. Acute and chronic treatment of BME-UV with T09 dramatically increased de novo fatty acid synthesis. Activation of LXR resulted in the upregulation of transcription, translation, and proteolytic cleavage of sterol regulatory element-binding protein-1 (SREBP1), a lipogenic transcription factor expressed in the bovine mammary gland. Additionally, the mRNA abundance of fatty acid synthase, an LXR and SREBP1 target gene, increased in response to LXR activation. Our data indicate that SREBP1 is regulated by LXR activation in BME-UV. Controlling LXR activation may prove useful in regulating milk fat production in lactating dairy cows.