Glutamine plays major roles in the inter-organ transport of nitrogen, carbon and energy within the body and is becoming recognized as an important regulatory molecule signaling changes in cell proliferation, gene expression, and protein metabolism. This has resulted in the increasing use of supplemental glutamine in both enteral and parenteral formulae. The research emphasis of this laboratory is the role and regulation of glutamine and glutamate metabolism, as they relate to gluconeogenesis and nitrogen excretion.

Specific Research Areas:

1. The Regulatory Role of Glutamine.
   1. We have established that 3T3L1 pre-adipocytes require glutamine, for growth, differentiation into adipocytes, and lipid storage. We are currently working to define exactly where glutamine is required and the mechanisms involved.
   2. The enzyme glutamine synthetase is rapidly degraded in C2C12 muscle cells cultured in the presence of glutamine and that this effect is not dependent on metabolism of the glutamine. Current work is focused on the mechanisms by which glutamine can signal the breakdown of a specific protein.
2. Engineering Glutamine and Glutamate Metabolism.
   In order to fully understand nitrogen homeostasis in health and disease we are working with Dr. Fatima Bosch (Autonomous University of Barcelona) to develop cell lines and mice with modified expression of key enzymes of glutamine and glutamate metabolism.
3. Comparative Aspects of Nitrogen Metabolism
   Working with Dr. Guoyao Wu ( Texas A & M University) we have established key tissue-specific differences in the glutamine metabolism of uricotelic species (birds and lizards) when compared to ureotelic species (mammals). We intend to continue such comparative studies which allow different approaches to key questions relating to nitrogen homeostasis.

Representative Publications

Huang, Y.F., Wang, Y. and Watford, M. (2007) Glutamine directly down-regulates the level of glutamine synthetase protein in C2C12 skeletal muscle cells. J. Nutr. in press

Manso-Filho, HC., Watford, M. and McKeever, K.H. (2007) Novel findings regarding Glut-4 expression in adipose tissue and muscle in horses. The Veterinary Journal in press

Wang, Y. and Watford, M. (2007) Glutamine, insulin and glucocorticoids regulate glutamine synthetase expression in C2C12 myotubes, HepG2 hepatoma cells and 3T3 L1 adipocytes.  Biochim. Biophys. Acta 1770: 594-600

Watford, M. (2007) Lowered concentrations of branched chain amino acids lead to impaired growth and neurological problems:  insights from a branched chain a-keto acid dehydrogenase complex kinase-deficient mouse model.  Nutr. Rev. 65, 167-172

Stipanuk, M.H. and Watford, M. (2006) Amino Acid Metabolism, in Biochemical, Physiological & Molecular Aspects of Human Nutrition (Stipanuk, M.H. ed 2nd edition) Saunders, Chapter 14, pp 360-418

Watford, M. (2006) Regulation of Fuel Utilization in Response to Food intake, in Biochemical, Physiological & Molecular Aspects of Human Nutrition (Stipanuk, M.H.ed, 2nd Edition) Saunders, Chapter 16, pp 541-565

Ribnicky, D.M, Poulev, A, Watford, M, Cefalu, W.T. and Raskin, I.  (2006) The effect of Tarralin, an extract of Artemisia dracunculus L., on blood glucose parameters in diabetic animal models.  Phytomedicine 13, 550-557

Watford, M. (2005) Is the small intestine a gluconeogenic organ?  Nutrition Reviews  63: 356-360

Watford, M. and Wu, G. (2005) Glutamine metabolism in uricotelic species: variation in skeletal muscle glutamine synthetase, glutaminase, glutamine content and rates of protein synthesis. Comp. Biochem. Physiol. 140B, 607-614

Brosnan, J.T. and Watford, M. (2004) Starvation: metabolic changes, Encyclopedia of Life Science (www.ELS.net), Nature Publishing Group,

Watford, M. (2004) The Ornithine Cycle, Encyclopedia of Biological Chemistry, Elsevier Science 172-177

Watford, M. (2003) The Urea Cycle: Teaching intermediary metabolism in a physiological setting. Biochem. Mole. Biol. Ed.31, 289-297

Watford, M., Chellaraj, V.C., Ismat, A., Brown, P. and Raman, P. (2002) Hepatic Glutamine Metabolism, Nutrition, 18:301-303

Watford, M. (2002) Net inter-organ transport of L-glutamate in the rat occurs via the plasma not via erythrocytes. J. Nutr. 132: 952-956

Patterson, B.W., Horowitz, J.F., Wu, G., Watford, M., Coppack, S.W. and Klein, S. (2002) Regional Muscle and Adipose Tissue Amino Acid Metabolism in Lean and Obese Humans. Am. J. Physiol. Endocrinol. Metab. 282: E931-E936

Watford, M. (2000) Glutamine and Glutamate Metabolism Across the Liver Sinusoid. J. Nutr. 130: 983S-985S

Watford, M., Darcy-Vrillon, B. and Duee, P.-H. (2000) Dietary Glutamine Suppresses the Appearance of Endogenous Glutamine in the Rat. Metabolism, 49: 141-145

Wu, G., Chung-Bok, M.-I., Vincent, N., Kowalski, T.J., Choi, Y-H. and Watford, M. (1998) Distribution of Phosphate Activated Glutaminase Isozymes in the Chicken: Absence from Liver but Presence of High Activity in Pectoralis Muscle. Comp. Biochem. Physiol. 120B, 285-290

Chung-Bok, M.I., Vincent, N., Jhala, U. and Watford, M. (1997) Rat Liver Glutaminase: Identification of the Full-Length Coding Sequence and Characterization of a Functional Promoter. Biochem. J. 324: 193-200

Kowalski, T.J., Wu, G. and Watford, M. (1997) Rat Adipose Tissue Amino Acid Metabolism In Vivo as Assessed by Microdialysis and Arterio-Venous Techniques. Am. J. Physiol. 273: E613-E622

Curthoys, N.P. and Watford, M. (1995) Regulation of Glutaminase Expression and Glutamine Metabolism. Ann. Rev. Nutr. 15: 133-159.