title: Adipocyte differentiation-related protein promotes lipid accumulation in goat mammary epithelial cells.
abstract: Milk fat originates from the secretion of cytosolic lipid droplets (CLD) synthesized within mammary epithelial cells. Adipocyte differentiation-related protein (ADRP; gene symbol PLIN2) is a CLD-binding protein that is crucial for synthesis of mature CLD. Our hypothesis was that ADRP regulates CLD production and metabolism in goat mammary epithelial cells (GMEC) and thus plays a role in determining milk fat content. To understand the role of ADRP in ruminant milk fat metabolism, ADRP (PLIN2) was overexpressed or knocked down in GMEC using an adenovirus system. Immunocytochemical staining revealed that ADRP localized to the surface of CLD. Supplementation with oleic acid (OA) enhanced its colocalization with CLD surface and enhanced lipid accumulation. Overexpression of ADRP increased lipid accumulation and the concentration of triacylglycerol in GMEC. In contrast, morphological examination revealed that knockdown of ADRP decreased lipid accumulation even when OA was supplemented. This response was confirmed by the reduction in mass of cellular TG when ADRP was knocked down. The fact that knockdown of ADRP did not completely eliminate lipid accumulation at a morphological level in GMEC without OA suggests that some other compensatory factors may also aid in the process of CLD formation. The ADRP reversed the decrease of CLD accumulation induced by adipose triglyceride lipase. This is highly suggestive of ADRP promoting triacylglycerol stability within CLD by preventing access to adipose triglyceride lipase. Collectively, these data provide direct in vitro evidence that ADRP plays a key role in CLD formation and stability in GMEC.
authors: Shaanxi Key Laboratory of Molecular Biology for Agriculture, College of Animal Science and Technology, Northwest A&F University, Yangling, Shaanxi, P.R. China 712100; College of Life Science, Zhejiang Sci-Tech University, Hangzhou, Zhejiang, P. R. China 310018.
authors: H B
authors: HB
authors: Shi
authors: Shaanxi Key Laboratory of Molecular Biology for Agriculture, College of Animal Science and Technology, Northwest A&F University, Yangling, Shaanxi, P.R. China 712100.
authors: K
authors: K
authors: Yu
authors: Shaanxi Key Laboratory of Molecular Biology for Agriculture, College of Animal Science and Technology, Northwest A&F University, Yangling, Shaanxi, P.R. China 712100. Electronic address: luojun@nwsuaf.edu.cn.
authors: J
authors: J
authors: Luo
authors: Shaanxi Key Laboratory of Molecular Biology for Agriculture, College of Animal Science and Technology, Northwest A&F University, Yangling, Shaanxi, P.R. China 712100.
authors: J
authors: J
authors: Li
authors: Shaanxi Key Laboratory of Molecular Biology for Agriculture, College of Animal Science and Technology, Northwest A&F University, Yangling, Shaanxi, P.R. China 712100.
authors: H B
authors: HB
authors: Tian
authors: Shaanxi Key Laboratory of Molecular Biology for Agriculture, College of Animal Science and Technology, Northwest A&F University, Yangling, Shaanxi, P.R. China 712100.
authors: J J
authors: JJ
authors: Zhu
authors: Shaanxi Key Laboratory of Molecular Biology for Agriculture, College of Animal Science and Technology, Northwest A&F University, Yangling, Shaanxi, P.R. China 712100.
authors: Y T
authors: YT
authors: Sun
authors: Shaanxi Key Laboratory of Molecular Biology for Agriculture, College of Animal Science and Technology, Northwest A&F University, Yangling, Shaanxi, P.R. China 712100.
authors: D W
authors: DW
authors: Yao
authors: Shaanxi Key Laboratory of Molecular Biology for Agriculture, College of Animal Science and Technology, Northwest A&F University, Yangling, Shaanxi, P.R. China 712100.
authors: H F
authors: HF
authors: Xu
authors: Shaanxi Key Laboratory of Molecular Biology for Agriculture, College of Animal Science and Technology, Northwest A&F University, Yangling, Shaanxi, P.R. China 712100.
authors: H P
authors: HP
authors: Shi
authors: Mammalian NutriPhysioGenomics, Department of Animal Sciences and Division of Nutritional Sciences, University of Illinois, Urbana 61801. Electronic address: jloor@illinois.edu.
authors: J J
authors: JJ
authors: Loor
mesh_terms: D000818:Animals; D002352:Carrier Proteins; D003001:Cloning, Molecular; D004847:Epithelial Cells / Q000378:metabolism*; D005260:Female; D015870:Gene Expression; D055785:Gene Knockdown Techniques / Q000662:veterinary; D006041:Goats / Q000378:metabolism*; D050356:Lipid Metabolism / Q000502:physiology*; D008321:Mammary Glands, Animal / Q000166:cytology*; D008565:Membrane Proteins / Q000235:genetics / Q000502:physiology*; D008892:Milk / Q000737:chemistry; D019301:Oleic Acid / Q000008:administration & dosage; D000070780:Perilipin-2; D014162:Transfection / Q000662:veterinary; D014280:Triglycerides / Q000032:analysis / Q000378:metabolism
chemical_list: D002352:Carrier Proteins; D008565:Membrane Proteins; D000070780:Perilipin-2; D014280:Triglycerides; D019301:Oleic Acid
keywords: hydrolysis; lipid droplet; milk fat; triacylglycerol