To explore the function of PPARγ in the goat mammary gland, we cloned the whole cDNA of the PPARγ gene. Homology alignments revealed that the goat PPARγ gene is conserved among goat, bovine, mouse, and human. Luciferase assays revealed that rosiglitazone enhanced the activity of the PPARγ response element (PPRE) in goat mammary epithelial cells (GMECs). After rosiglitazone (ROSI) treatment of GMECs, there was a significant (P < 0.05) increase in the expression of genes related to triacylglycerol synthesis and secretion: LPL, FASN, ACACA, PLIN3, FABP3, PLIN2, PNPLA2, NR1H3, SREBF1, and SCD. The decreases in expression observed after knockdown of PPARγ relative to the control group (Ad-NC) averaged 65%, 52%, 67%, 55%, 65%, 58%, 85%, 43%, 50%, and 24% for SCD, DGAT1, AGPAT6, SREBF1, ACACA, FASN, FABP3, SCAP, ATGL, and PLIN3, respectively. These results provide direct evidence that PPARγ plays a crucial role in regulating the triacylglycerol synthesis and secretion in goat mammary cells and underscore the functional importance of PPARγ in mammary gland tissue during lactation.

In rodents, peroxisome proliferator-activated receptor-γ (PPARG) plays a crucial role in fatty acid (FA) metabolism through regulation of gene expression, including stearoyl-coenzyme A desaturase (SCD), which is the rate-limiting enzyme for the biosynthesis of monounsaturated FA. However, whether or how PPARG regulates the activity of mammary SCD in ruminants is unknown. This study explored the potential role of PPARG isoforms in regulating SCD mRNA expression in lactating goat mammary epithelial cells (GMEC). Using quantitative real-time PCR, we observed a positive correlation between PPARG and SCD expression in the goat mammary gland at peak lactation. Overexpression of both PPARG1 and PPARG2 in GMEC increased markedly the expression of SCD, the concentration of 16:1 and 18:1, and the desaturation indices of 16:1 and 18:1. The PPARG ligand rosiglitazone further increased SCD expression and desaturation indices in GMEC, overexpressing PPARG1 and PPARG2. Incubation with rosiglitazone alone increased the expression of SCD, but did not alter the concentration of 16- to 18-carbon FA or their desaturation indices. The results provide evidence that PPARG regulates the expression and activity of SCD in GMEC. As such, PPARG may contribute to regulation of SCD and monounsaturated FA synthesis during lactation.

No abstract

Dairy goats serve as an important source of milk and also fulfill agricultural and economic roles in developing countries. Understanding the genetic background of goat mammary gland is important for research on the regulatory mechanisms controlling tissue function and the synthesis of milk components. We collected tissue at four different stages of goat mammary gland development and generated approximately 25 GB of data from Illumina de novo RNA sequencing. The combined reads were assembled into 51,361 unigenes, and approximately 60.07 % of the unigenes had homology to other proteins in the NCBI non-redundant protein database (NR). Functional classification through eukaryotic Ortholog Groups of Protein (KOG), gene ontology (GO), and Kyoto Encyclopedia of Genes and Genomes (KEGG) revealed that the unigenes from goat mammary glands are involved in a wide range of biological processes and metabolic pathways, including lipid metabolism and lactose metabolism. The results of qPCR revealed that genes encoding FABP3, FASN, SCD, PLIN2, whey proteins (LALBA and BLG), and caseins (CSN1S1, CSN1S2, CSN2 and CSN3) at 100 and 310 days postpartum increased significantly compared with the non-lactating period. In addition to their role in lipid and protein synthesis, the higher expression at 310 days postpartum could contribute to mammary cell turnover during pregnancy. In conclusion, this is the first study to characterize the complete transcriptome of goat mammary glands and constitutes a comprehensive genomic resource available for further studies of ruminant lactation.

No abstract