Thyroid hormone responsive protein spot 14 enhances lipogenesis in bovine mammary epithelial cells.

Thyroid hormone responsive spot 14 (THRSP, Spot14, S14) is a nuclear protein that regulates milk fat synthesis. To investigate the role of THRSP in lipogenesis in the dairy cow mammary gland, first, we examined the association between milk fat concentration and THRSP expression in the mammary gland. We found that the dairy cow mammary glands that produced milk with high fat had high THRSP mRNA and protein levels. Additionally, the study described the consequences of overexpression or depletion of THRSP on lipogenesis in cultured bovine mammary epithelial cells (BMECs). We found that BMECs with overexpressed THRSP increased triacylglycerol levels and enhanced the expression of FAS, PPARγ, and SREBP1, compared with the control BMECs. Depletion of THRSP produced the opposite effects. Overall, increased mammary expression of THRSP can be a marker of high fat. In addition, our results provide evidence that THRSP may regulate expression of PPARγ and SREBP1 and can regulate milk fat synthesis by directly affecting the activity of some classical lipogenic enzymes.