title: Alpha-ketoglutarate inhibits glutamine degradation and enhances protein synthesis in intestinal porcine epithelial cells.
abstract: α-Ketoglutarate (AKG) is a key intermediate in glutamine metabolism. Emerging evidence shows beneficial effects of AKG on clinical and experimental nutrition, particularly with respect to intestinal growth and integrity. However, the underlying mechanisms are unknown. Intestinal porcine epithelial cells (IPEC-1) were used to test the hypothesis that AKG inhibits glutamine degradation and enhances protein synthesis. IPEC-1 cells were cultured for 3 days in Dulbecco's modified Eagle's-F12 Ham medium (DMEM-F12) containing 0, 0.2, 0.5 or 2 mM of AKG. At the end of the 3-day culture, cells were used to determine L-[U-14C]glutamine utilization, protein concentration, protein synthesis, and the total and phosphorylated levels of the mammalian target of the rapamycin (mTOR), ribosomal protein S6 kinase-1 (S6K1) and eukaryotic initiation factor (eIF) 4E-binding protein-1 (4E-BP1). Compared with 0 mM of AKG (control), 0.2 and 0.5 mM of AKG dose-dependently reduced (P<0.05) glutamine degradation and the production of glutamate, alanine and aspartate in IPEC-1 cells. Addition of 0.5 and 2 mM of AKG to culture medium enhanced protein synthesis (P<0.05) by 78 and 101% without affecting protein degradation, compared to the control group. Rapamycin (50 nM; a potent inhibitor of mTOR) attenuated the stimulatory effect of AKG on protein synthesis. Consistent with these metabolic data, the addition of 0.5 or 2 mM of AKG to culture medium increased (P<0.05) the phosphorylated levels of mTOR, S6k1 and 4E-BP1 proteins. Collectively, these results indicate that AKG can spare glutamine and activate the mTOR signaling pathway to stimulate protein synthesis in intestinal epithelial cells.
authors.affiliation: Research Center for Healthy Breeding of Livestock and Poultry and Key Laboratory for Agro-ecological Processes in Subtropical Region, Institute of Subtropical Agriculture, The Chinese Academy of Sciences, Hunan, 410125, China. yaokang1981@gmail.com
authors.forename: Kang
authors.initials: K
authors.lastname: Yao
authors.forename: Yulong
authors.initials: Y
authors.lastname: Yin
authors.forename: Xilong
authors.initials: X
authors.lastname: Li
authors.forename: Pengbin
authors.initials: P
authors.lastname: Xi
authors.forename: Junjun
authors.initials: J
authors.lastname: Wang
authors.forename: Jian
authors.initials: J
authors.lastname: Lei
authors.forename: Yongqing
authors.initials: Y
authors.lastname: Hou
authors.forename: Guoyao
authors.initials: G
authors.lastname: Wu
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism; D000409:Alanine / Q000378:metabolism; D000818:Animals; D000831:Animals, Newborn; D001224:Aspartic Acid / Q000378:metabolism; D002250:Carbon Radioisotopes; D002478:Cells, Cultured; D003470:Culture Media; D004305:Dose-Response Relationship, Drug; D004847:Epithelial Cells / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D005973:Glutamine / Q000378:metabolism*; D007413:Intestinal Mucosa / Q000378:metabolism; D007422:Intestines / Q000166:cytology / Q000187:drug effects*; D007656:Ketoglutaric Acids / Q000378:metabolism / Q000494:pharmacology*; D010766:Phosphorylation / Q000187:drug effects; D014176:Protein Biosynthesis / Q000187:drug effects*; D038762:Ribosomal Protein S6 Kinases, 70-kDa / Q000378:metabolism; D020123:Sirolimus / Q000494:pharmacology; D013552:Swine; D058570:TOR Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D002250:Carbon Radioisotopes; D003470:Culture Media; D007656:Ketoglutaric Acids; D005973:Glutamine; D001224:Aspartic Acid; D038762:Ribosomal Protein S6 Kinases, 70-kDa; D058570:TOR Serine-Threonine Kinases; D000409:Alanine; D020123:Sirolimus