RESUMEN
Goat milk is rich in various fatty acids that are beneficial to human health. Chromatin immunoprecipitation followed by sequencing (ChIP-seq) and RNA-seq analyses of goat mammary glands at different lactation stages revealed a novel lactation regulatory factor, Prospero homeobox 1 (PROX1). However, the mechanism whereby PROX1 regulates lipid metabolism in dairy goats remains unclear. We found that PROX1 exhibits the highest expression level during peak lactation period. PROX1 knockdown enhanced the expression of genes related to de novo fatty acid synthesis (e.g., SREBP1 and FASN) and triacylglycerol (TAG) synthesis (e.g., DGAT1 and GPAM) in goat mammary epithelial cells (GMECs). Consistently, intracellular TAG and lipid droplet contents were significantly increased in PROX1 knockdown cells and reduced in PROX1 overexpression cells, and we observed similar results in PROX1 knockout mice. Following PROX1 overexpression, RNA-seq showed a significant upregulation of peroxisome proliferator-activated receptor gamma coactivator-1 alpha (PPARGC1A) expression. Further, PPARGC1A knockdown attenuated the inhibitory effects of PROX1 on TAG contents and lipid-droplet formation in GMECs. Moreover, we found that PROX1 promoted PPARGC1A transcription via the PROX1 binding sites (PBSs) located in the PPARGC1A promoter. These results suggest a novel target for manipulating the goat milk-fat composition and improving the quality of goat milk.
Asunto(s)
Ácidos Grasos , Técnicas de Silenciamiento del Gen , Cabras , Proteínas de Homeodominio , Lactancia , Glándulas Mamarias Animales , Leche , Coactivador 1-alfa del Receptor Activado por Proliferadores de Peroxisomas gamma , Proteínas Supresoras de Tumor , Animales , Cabras/genética , Glándulas Mamarias Animales/metabolismo , Glándulas Mamarias Animales/citología , Leche/metabolismo , Ácidos Grasos/metabolismo , Ácidos Grasos/biosíntesis , Femenino , Coactivador 1-alfa del Receptor Activado por Proliferadores de Peroxisomas gamma/genética , Coactivador 1-alfa del Receptor Activado por Proliferadores de Peroxisomas gamma/metabolismo , Proteínas de Homeodominio/genética , Proteínas de Homeodominio/metabolismo , Lactancia/genética , Proteínas Supresoras de Tumor/genética , Proteínas Supresoras de Tumor/metabolismo , Ratones , Regulación de la Expresión Génica , Células Epiteliales/metabolismo , Regiones Promotoras Genéticas , Metabolismo de los Lípidos/genéticaRESUMEN
Goat milk is enriched in fatty acids which are beneficial to human health. Previous research has revealed that 98% of milk fat is composed of triglycerides. However, the mechanisms regulating milk fat composition remain unclear. Forkhead box protein O1 (FoxO1) is a crucial regulatory factor involved in lipid metabolism across various cell types. Chromatin immunoprecipitation sequencing (ChIP)-seq data) and RNA sequencing (RNA-seq) data revealed that have indicated a close association between FoxO1 was closely related to lipid metabolism during lactation in dairy goats. The objective of this study was to investigate the mechanisms by which FoxO1 regulates lipid metabolism in goat mammary epithelial cells (GMECs). FoxO1 knockdown significantly downregulated the expression of adipose triglyceride lipase (ATGL) and suppressed the activity of the ATGL promoter. Consistently, the number of lipid droplets decreased significantly in FoxO1-overexpressing cells and increased in ATGL-knockdown cells. To further verify the effect of FoxO1 on ATGL promoter activity, cells were transfected with four promoter fragments of different lengths. We found that the core region of the ATGL promoter was located between -882 bp and -524 bp, encompassing two FoxO1 binding sites (FKH1 and FKH2). Mutations in the FoxO1 binding sites significantly downregulated ATGL promoter activity in GMECs. Luciferase reporter assays demonstrated that FoxO1 overexpression markedly enhanced ATGL promoter activity. Furthermore, site-directed mutation confirmed that FKH1 and FKH2 sites were simultaneously mutated significantly attenuated the stimulatory effect of FoxO1 on ATGL promoter activities simultaneous mutation of FKH1 and FKH2 sites significantly attenuated the stimulatory effect of FoxO1 on ATGL promoter activity. ChIP assays showed that FoxO1 directly binds to the FKH2 element located in the ATGL promoter in vivo. Finally, immunofluorescence staining revealed that insulin promotes the translocation of FoxO1 from the nucleus to the cytoplasm, thereby attenuating the FoxO1-induced activation of the ATGL promoter. Collectively, these findings uncover a novel pathway where by FoxO1 may regulate lipid metabolism in GMECs specifically by modulating the transcriptional activity of ATGL.
Forkhead box protein O1(FoxO1) is a key cellular regulatory factor that was involved in lipid metabolism in several cell types. This study was performed to explore the regulatory mechanism of FoxO1 in adipose triglyceride lipase (ATGL) promoter-driven transcription during lactation in dairy goats. Chromatin immunoprecipitation (ChIP)-seq and RNA sequencing (RNA-seq) data revealed that FoxO1 was closely related to lipid metabolism and inflammation during lactation in dairy goats. FoxO1 overexpression significantly decreased cellular triglyceride (TAG) content lipid droplet accumulation in goat mammary epithelial cells (GMECs), while ATGL knockdown attenuated this effect of FoxO1. Furthermore, the relative content of free fatty acid (FFAs) was markedly increased in FoxO1-overexpressed cells. Additionally, site-directed mutation and ChIP assays confirmed that FoxO1 promotes ATGL transcription through FoxO1 binding sites (FKH) located in the ATGL promoter. Moreover, insulin attenuated the FoxO1-induced activation of the ATGL promoter. Our data reveal that FoxO1 regulates the activity of ATGL in GMECs by binding to FKH elements located in the ATGL promoter.
