![[Feedback]](/icons/banner/feedbackACT.gif){kind=icon}
![[For Subscribers]](/icons/banner/subscriberACT.gif){kind=icon}
![[Archive]](/icons/banner/archiveACT.gif){kind=icon}
![[Search]](/icons/banner/searchACT.gif){kind=icon}
![[Contents]](/icons/banner/tocACT.gif){kind=icon}
|
|
|
|
|
||
Department of Food Science and Human Nutrition, Iowa State University, Ames, IA 50011
3To whom correspondence should be addressed. E-mail: kschalin{at}iastate.edu.
Glycine N-methyltransferase (GNMT) regulates S-adenosylmethionine (SAM) levels and the ratio of SAM:S-adenosylhomocysteine (SAH). In liver, methionine availability, both from the diet and via the folate-dependent one-carbon pool, modulates GNMT activity to maintain an optimal SAM:SAH ratio. The regulation of GNMT activity is accomplished via posttranslational and allosteric mechanisms. We more closely examined GNMT regulation in various tissues as a function of excess dietary methyl groups. Sprague Dawley rats were fed either a control diet (10% casein plus 0.3% L-methionine) or the control diet supplemented with graded levels (0.5–2%) of L-methionine. Pair-fed control groups of rats were included due to the toxicity associated with high methionine consumption. As expected, the hepatic activity of GNMT was significantly elevated in a dose-dependent fashion after 10 d of feeding the diets containing excess methionine. Moreover, the abundance of hepatic GNMT protein was similarly increased. The kidney had a significant increase in GNMT as a function of dietary methionine, but to a much lesser extent than in the liver. For pancreatic tissue, neither the activity of GNMT nor the abundance of the protein was responsive to excess dietary methionine. These data suggest that additional mechanisms contribute to regulation of GNMT such that synthesis of the protein is greater than its degradation. In addition, methionine-induced regulation of GNMT is dose dependent and appears to be tissue specific, the latter suggesting that the role it plays in the kidney and pancreas may in part differ from its hepatic function.
KEY WORDS: • methionine • S-adenosylmethionine • tissue-specific • glycine N-methyltransferase • rats
This article has been cited by other articles:
|
|
 |
|
  K. M. Nieman, C. S. Hartz, S. S. Szegedi, T. A. Garrow, J. D. Sparks, and K. L. Schalinske Folate status modulates the induction of hepatic glycine N-methyltransferase and homocysteine metabolism in diabetic rats Am J Physiol Endocrinol Metab, December 1, 2006; 291(6): E1235 - E1242. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 R. A. Waterland Assessing the Effects of High Methionine Intake on DNA Methylation J. Nutr., June 1, 2006; 136(6): 1706S - 1710S. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
B. Beagle, T. L. Yang, J. Hung, E. A. Cogger, D. J. Moriarty, and M. A. Caudill The Glycine N-Methyltransferase (GNMT) 1289 C->T Variant Influences Plasma Total Homocysteine Concentrations in Young Women after Restricting Folate Intake J. Nutr., December 1, 2005; 135(12): 2780 - 2785. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 E. P. Wijekoon, B. Hall, S. Ratnam, M. E. Brosnan, S. H. Zeisel, and J. T. Brosnan Homocysteine Metabolism in ZDF (Type 2) Diabetic Rats Diabetes, November 1, 2005; 54(11): 3245 - 3251. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 C. L. Ulrey, L. Liu, L. G. Andrews, and T. O. Tollefsbol The impact of metabolism on DNA methylation Hum. Mol. Genet., April 15, 2005; 14(suppl_1): R139 - R147. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
R. Zhang, J. Ma, M. Xia, H. Zhu, and W. Ling Mild Hyperhomocysteinemia Induced by Feeding Rats Diets Rich in Methionine or Deficient in Folate Promotes Early Atherosclerotic Inflammatory Processes J. Nutr., April 1, 2004; 134(4): 825 - 830. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. J. Rowling and K. L. Schalinske Retinoic Acid and Glucocorticoid Treatment Induce Hepatic Glycine N-Methyltransferase and Lower Plasma Homocysteine Concentrations in Rats and Rat Hepatoma Cells J. Nutr., November 1, 2003; 133(11): 3392 - 3398. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
V. R. Young Introduction to the 2nd Amino Acid Assessment Workshop J. Nutr., June 1, 2003; 133(6): 2015S - 2020. [Abstract] [Full Text] [PDF]
|
|
