title: The regulation of glucose on milk fat synthesis is mediated by the ubiquitin-proteasome system in bovine mammary epithelial cells.
abstract: Glucose as one of the nutrition factors plays a vital role in the regulation of milk fat synthesis. Ubiquitin-proteasome system (UPS) is a vital proteolytic pathway in all eukaryotic cells through timely marking, recognizing and degrading the poly-ubiquitinated protein substrates. Previous studies indicated that UPS plays a considerable role in controlling the triglyceride (TG) synthesis. Therefore, the aim of this study is to confirm the link between high-glucose and UPS and its regulation mechanism on milk fat synthesis in BMEC (bovine mammary epithelial cells). We incubated BMEC with normal (17.5 mm/L) and high-glucose (25 mm/L) with and without proteasome inhibitor epoxomicin and found that, compared with the control (normal glucose and without proteasome inhibitor), both high-glucose concentration and proteasome inhibitor epoxomicin could increase the accumulation of TG and poly-ubiquitinated proteins, and reduce significantly three proteasome activities (chymotrypsin-like, caspase-like, and trypsin-like). In addition, high-glucose concentration combined with proteasome inhibitor further enhanced the increase of the poly-ubiquitinated protein level and the decrease of proteasome activities. Our results suggest that the regulation of high-glucose on milk fat synthesis is mediated by UPS in BMEC, and high-glucose exposure could lead to a hypersensitization of BMEC to UPS inhibition which in turn results in increased milk fat synthesis.
authors.affiliation: Key Laboratory of Animal Genetics and Breeding of Ministry of Agriculture, National Engineering Laboratory of Animal Breeding, College of Animal Science and Technology, China Agricultural University, Beijing 100193, China.
authors.forename: Lily
authors.initials: L
authors.lastname: Liu
authors.affiliation: Key Laboratory of Animal Genetics and Breeding of Ministry of Agriculture, National Engineering Laboratory of Animal Breeding, College of Animal Science and Technology, China Agricultural University, Beijing 100193, China.
authors.forename: Li
authors.initials: L
authors.lastname: Jiang
authors.affiliation: Key Laboratory of Animal Genetics and Breeding of Ministry of Agriculture, National Engineering Laboratory of Animal Breeding, College of Animal Science and Technology, China Agricultural University, Beijing 100193, China.
authors.forename: Xiang-dong
authors.initials: XD
authors.lastname: Ding
authors.affiliation: Key Laboratory of Animal Genetics and Breeding of Ministry of Agriculture, National Engineering Laboratory of Animal Breeding, College of Animal Science and Technology, China Agricultural University, Beijing 100193, China.
authors.forename: Jian-feng
authors.initials: JF
authors.lastname: Liu
authors.affiliation: Key Laboratory of Animal Genetics and Breeding of Ministry of Agriculture, National Engineering Laboratory of Animal Breeding, College of Animal Science and Technology, China Agricultural University, Beijing 100193, China. Electronic address: qzhang@cau.edu.cn.
authors.forename: Qin
authors.initials: Q
authors.lastname: Zhang
mesh_terms: D000818:Animals; D002417:Cattle; D004847:Epithelial Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D005260:Female; D005947:Glucose / Q000378:metabolism / Q000494:pharmacology*; D007774:Lactation / Q000502:physiology; D008321:Mammary Glands, Animal / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D009842:Oligopeptides / Q000494:pharmacology; D061251:Primary Cell Culture; D046988:Proteasome Endopeptidase Complex / Q000187:drug effects / Q000378:metabolism*; D061988:Proteasome Inhibitors / Q000494:pharmacology; D014280:Triglycerides / Q000096:biosynthesis*; D025801:Ubiquitin / Q000378:metabolism*
chemical_list: D009842:Oligopeptides; D061988:Proteasome Inhibitors; D014280:Triglycerides; D025801:Ubiquitin; D046988:Proteasome Endopeptidase Complex; D005947:Glucose; C078846:epoxomicin
keywords: BMEC; High-glucose; Milk fat synthesis; Poly-ubiquitinated proteins; Proteasome activity; UPS