Amino Acids

, Volume 42, Issue 6, pp 2491–2500 | Cite as

Alpha-ketoglutarate inhibits glutamine degradation and enhances protein synthesis in intestinal porcine epithelial cells

Original Article

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.

Keywords

α-Ketoglutarate Intestinal cells mTOR signaling Protein synthesis 

Abbreviations

AKG

α-Ketoglutarate

BSA

Bovine serum albumin

DMEM-F12

Dulbecco’s modified Eagle’s F12 Ham medium

FBS

Fetal bovine serum

IPEC-1

Intestinal porcine epithelial cells-1

mTOR

Mammalian target of rapamycin

4E-BP1

4E-Binding protein-1

S6K1

70-kDa Ribosomal protein S6 kinase-1

Notes

Acknowledgments

This research was jointly supported by the National Natural Science Foundation of China (30901041, 30901040, 30928018, 30972156, 30871801, 30828024, 30828025, 30771558 and 30700581), National 863 Project (2008AA10Z316), National Basic Research Project (2009CB118800), the CAS/SAFEA International Partnership Program for Creative Research Teams, the Program for Innovative Research Groups of Hubei Provincial Natural Science Foundation (Grant No. 2007ABC009), Texas AgriLife Research, American Heart Association (10GRNT4480020) and the Thousand-People-Talent program at the China Agricultural University.

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Copyright information

© Springer-Verlag 2011

Authors and Affiliations

  1. 1.Research Center for Healthy Breeding of Livestock and Poultry and Key Laboratory for Agro-ecological Processes in Subtropical RegionInstitute of Subtropical Agriculture, The Chinese Academy of SciencesHunanChina
  2. 2.Department of Animal ScienceTexas A&M UniversityCollege StationUSA
  3. 3.Ministry of Agriculture Key Laboratory of Animal Nutrition and Feed Science (South China)Institute of Animal Science, Guangdong Academy of Agricultural SciencesGuangzhouPeople’s Republic of China
  4. 4.State Key Laboratory of Animal NutritionChina Agricultural UniversityBeijingChina
  5. 5.Hubei Key Laboratory of Animal Nutrition and Feed ScienceWuhan Polytechnic UniversityWuhanChina

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