Title: Adaptation to a long term (4 weeks) arginine- and precursor (glutamate, proline and aspartate)-free diet Authors
|Tharakan, John - MIT, CAMBRIDGE, MA|
|Yu, Yong - SHRINRS BURN HOSP, BOSTON|
|Zurakowski, David - CHILDRNS HOSP, BOSTON, MA|
|Roth, Rachel - CHILDRNS HOSP, BOSTON, MA|
|Young, Vernon - MIT, CAMBRIDGE, MA|
|Castillo, Leticia - BAYLOR COL MED|
Submitted to: Clinical Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 25, 2008
Publication Date: N/A
Interpretive Summary: Arginine is an important amino acid because it serves as a precursor for important compounds such as nitric oxide, a gaseous molecule that intervenes in multiple functions. Arginine is also the precursor of creatine, which intervenes in energy metabolism. It is important to know the effects of long-term (4 weeks) arginine and its precursors-free intake in healthy humans, to determine how arginine metabolism is regulated under these conditions. We found that under these conditions the rates of catabolism of arginine decrease, while arginine synthesis is maintained but not increased. These regulatory mechanisms are similar whether the dietary period devoid of arginine intake is short- (1 week) or long-term (4 weeks). These studies describe the regulatory mechanisms of arginine under a long-term arginine free intake and show that these mechanisms are not changed whether arginine is deprived for a short- or a long-term period. These data contribute to the understanding of the metabolic regulation of arginine.
Technical Abstract: It is not known whether arginine homeostasis is negatively affected by a "long-term" dietary restriction of arginine and its major precursors in healthy adults. To assess the effects of a 4-week arginine- and precursor-free dietary intake on the regulatory mechanisms of arginine homeostasis in healthy subjects, 10 healthy adults received a complete amino acid diet for 1 week (control diet). Following a break period, six subjects received a 4-week arginine, proline, glutamate, and aspartate-free diet (APF diet). The other four subjects continued for 4 weeks with the complete diet. On days 4 and 7 of the first week and days 25 and 28 of the 4-week period, the subjects received 24-h infusions of arginine, citrulline, leucine, and urea tracers. During the 4-week APF, plasma arginine fluxes for the fed state, were significantly reduced. There were no significant differences for citrulline, leucine, or urea fluxes. Arginine de novo synthesis was not affected by the APF intake. However, arginine oxidation was significantly decreased. In healthy adults, homeostasis of arginine under a long-term arginine- and precursor-free intake is achieved by decreasing catabolic rates, while de novo arginine synthesis is maintained.