title: Effects of slow-release urea and rumen-protected methionine and histidine on mammalian target of rapamycin (mTOR) signaling and ubiquitin proteasome-related gene expression in skeletal muscle of dairy cows.
abstract: The mammalian target of rapamycin (mTOR) is a major regulator of protein synthesis, whereas the ubiquitin-proteasome system (UPS) is regarded as the main proteolytic pathway in skeletal muscle. The objective of the current study was to investigate the effects of slow-release urea and rumen-protected (RP) Met and His supplementation of a metabolizable protein (MP)-deficient diet on the abundance of key components of the mTOR pathway and of the UPS in skeletal muscle of dairy cows. Sixty Holstein cows were blocked based on days in milk and milk yield and were randomly assigned within block to 1 of 5 diets in a 10-wk experiment (including the first 2 wk as covariate period) as follows: (1) MP-adequate diet (AMP; 107% of MP requirements, based on the National Research Council requirements); (2) MP-deficient diet (DMP; 95% of MP requirements); (3) DMP supplemented with slow-release urea (DMPU); (4) DMPU supplemented with RPMet (DMPUM); and (5) DMPUM supplemented with RPHis (DMPUMH). Muscle biopsies were collected from longissimus dorsi during the last week of the experiment. The mRNA abundance of key mTOR signaling genes was not affected by the treatments. The phosphorylated (P)-mTOR protein was or tended to be greater for DMP compared with DMPU and AMP, respectively. The P-mTOR protein in DMPUMH was decreased when compared against DMPUM. The P-ribosomal protein S6 tended to be increased by DMPUM compared with DMPU. The abundance of total-S6 was or tended to be greater for DMP compared with AMP and DMPU, respectively. The mRNA abundance of ubiquitin activating and conjugating enzymes was not affected by the treatments, whereas that of muscle ring-finger protein 1 (MuRF-1) was greater in DMP than DMPU. The increased abundance of mTOR-associated signaling proteins and MuRF-1 mRNA abundance indicates a higher rate of protein turnover in muscle of DMP-fed cows. The reduced abundance of P-mTOR by supplementation of RPHis may suggest that His is likely partitioned to the mammary gland in favor of milk protein synthesis rather than to the skeletal muscle in dairy cows fed MP-deficient diets.
authors.affiliation: Institute of Animal Science, Physiology and Hygiene Unit, University of Bonn, 53115 Bonn, Germany; Department of Clinical Science, Faculty of Veterinary Medicine, University of Tabriz, 516616471 Tabriz, Iran. Electronic address: hsadri@uni-bonn.de.
authors.forename: H
authors.initials: H
authors.lastname: Sadri
authors.affiliation: Department of Animal Science, The Pennsylvania State University, University Park 16802.
authors.forename: F
authors.initials: F
authors.lastname: Giallongo
authors.affiliation: Department of Animal Science, The Pennsylvania State University, University Park 16802.
authors.forename: A N
authors.initials: AN
authors.lastname: Hristov
authors.affiliation: Animal Resource Program, The Pennsylvania State University, University Park 16802.
authors.forename: J
authors.initials: J
authors.lastname: Werner
authors.affiliation: Department of Cellular and Molecular Physiology, Penn State College of Medicine, Hershey, PA 17033.
authors.forename: C H
authors.initials: CH
authors.lastname: Lang
authors.affiliation: Evonik Nutrition & Care GmbH, Rodenbacher Chaussee 4, 63457 Hanau, Germany.
authors.forename: C
authors.initials: C
authors.lastname: Parys
authors.affiliation: Evonik Nutrition & Care GmbH, Rodenbacher Chaussee 4, 63457 Hanau, Germany.
authors.forename: B
authors.initials: B
authors.lastname: Saremi
authors.affiliation: Institute of Animal Science, Physiology and Hygiene Unit, University of Bonn, 53115 Bonn, Germany.
authors.forename: H
authors.initials: H
authors.lastname: Sauerwein
mesh_terms: D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D002417:Cattle; D004032:Diet / Q000662:veterinary; D004044:Dietary Proteins / Q000378:metabolism; D005260:Female; D005786:Gene Expression Regulation; D006639:Histidine / Q000494:pharmacology; D007774:Lactation; D008715:Methionine / Q000378:metabolism*; D008892:Milk / Q000378:metabolism; D018482:Muscle, Skeletal / Q000378:metabolism; D046988:Proteasome Endopeptidase Complex; D012417:Rumen / Q000378:metabolism*; D020123:Sirolimus / Q000378:metabolism*; D025801:Ubiquitin; D014508:Urea / Q000378:metabolism
chemical_list: D004044:Dietary Proteins; D025801:Ubiquitin; D006639:Histidine; D014508:Urea; D008715:Methionine; D046988:Proteasome Endopeptidase Complex; D020123:Sirolimus
keywords: dairy cow; mammalian target of rapamycin; muscle; rumen-protected amino acid; ubiquitin-proteasome system