Abstract
AIM: To investigate the formula of amino acid enriched BCAA on nutritional support in traumatic patients after operation.
METHODS: 40 adult patients after moderate or large abdominal operations were enrolled in a prospective, randomly and single-blind-controlled study, and received total parenteral nutrition (TPN) with either formula of amino acid (AA group, 20 cases) or formula of amino acid enriched BCAA (BCAA group, 20 cases). From the second day after operation, total parenteral nutrition was infused to the patients in both groups with equal calorie and equal nitrogen by central or peripheral vein during more than 12 hours per day for 6 days. Meanwhile, nitrogen balance was assayed by collecting 24 hours urine for 6 days. The markers of protein metabolism were investigated such as amino acid patterns, levels of total protein, albumin, prealbumin, transferrin and fibronectin in serum.
RESULTS: The positive nitrogen balance in BCAA group occurred two days earlier than that in AA group. The serum levels of total protein and albumin in BCAA group were increased more obviously than that in AA group. The concentration of valine was notably increased and the concentration of arginine was markedly decreased in BCAA group after the formula of amino acids enriched BCAA transfusion.
CONCLUSION: The formula of amino acid enriched BCAA may normalize the levels of serum amino acids, reduce the proteolysis, increase the synthesis of protein, improve the nutritional status of traumatic patients after operation.
INTRODUCTION
Hypermetabolism and increased catabolism can be observed in traumatic patients after operation, which may result in severe disturbance of sugar, lipid and protein metabolism[1-4], companied with the changes on the levels of amino acids in serum[5,6]. How to adjust the formula of amino acids to improve the metabolism is an interesting project. There has been no data about formula of amino acid which is fit for nutritional support of patients after trauma yet[7-11]. The purpose of our study was to investigate the effects of the formula of amino acids enriched BCAA on nutritional support in traumatic patients after operation.
MATERIALS AND METHODS
Subjects
40 adult patients after moderate or large abdominal operations who needed total parenteral nutrition (TPN) for more than 6 days were enrolled in a prospective, randomly and single-blind-controlled study from multiple centers during the period from March 2000 to November 2000. The patients (21 males and 19 females) weighed 45-71 kg and were 20-70 years old without metabolic diseases, malnutrition and dysfunction of liver and kidney. The change of weight in each patient was less than 10% of that before disease. The patients were divided into two groups in random order, the control group (AA group) supplemented with the formula of amino acid (BCAA 22.8%) and the study group (BCAA group) with the formula of amino acid enriched BCAA (BCAA 35.9%).
Experiment protocols
TPN was infused with equal nitrogen and calorie through peripheral or central vein during more than 12 hours per day for 6 days, and began on the 2nd day after operation. The formula included nitrogen (0.2 g·kg-1d-1), non-protein calorie (NPC, 25 kcal·kg-1d-1), the ratio of NPC to N (125/1), the ratio of lipid to sugar (1/1-3/2).
Collection of samples
Serum samples from all patients were collected on the day before operation and on the 7th day after operation. The amino acid pattern, total protein, albumin, prealbumin, transferring and fibronectin in serum were detected.
Urine samples: 24-hour urine samples (total volume of urine from 6 am on the first day to 6 am on the second day) of 40 patients were collected from the day before operation to the 7th day after operation to analyze nitrogen balance.
Assays of amino acids, proteins and nitrogen balance
The amino acid pattern in serum was analyzed by the system of high liquid phase amino acid analysis (BECKMAN, USA): 126AA, 166 monitor, 232 reactor, 507 autoloador, golden data station. The total protein (TP) and albumin in serum were respectively detected by the automatic biochemistry analyzer. The serum prealbumin, transferrin, fibronectin were monitored with anti-Pa, anti-Tf, anti-Fn immuno-diffusion board. (Yuhuan reagent Co.) The nitrogen balance was analyzed with the method of Kjeldah1 to get the data of nitrogen content in urine.
Statistical analysis
All data were expressed as mean ± SD. Comparisons between two groups were performed using an unpaired Student’s t test. Differences were considered statistically significant when P < 0.05.
RESULTS
General clinical data
The age, sex, weight diagnosis and operation of patients were presented in Table 1, and showed the data comparable in both groups.
Table 1.
The comparability of patients’ age, sex and operation
| Group | Case | Age(y) | Sex(M/F) | Weigh before operation(kg) | Colectomy | Enterectomy | Miles | Rectal cancer anterior-rectal resection | Aborminal trauma | Digestive tract tumor resection |
| AA | 20 | 20-75 | 9/11 | 59.58 ± 12.28 | 9 | 4 | 2 | 1 | 1 | 3 |
| BCAA | 20 | 20-75 | 12/8 | 60.38 ± 9.83 | 7 | 5 | 0 | 2 | 5 | 1 |
Nitrogen balance
As shown in Figure 1, the negative nitrogen balance was observed from all patients in both groups after operation, which was significantly improved after TPN infusion. The positive nitrogen balance in study group occurred on the third day after operation, which was earlier two days than that in the control group. On the sixth day after operation, the nitrogen balance in the study group is obviously better than that in the control group (P < 0.05).
Figure 1.
Nitrogen balance after infusion in two groups. aP < 0.05 vs the control group.
Serum levels of prealbumin, fibronectin, and transferrin
The serum levels of prealbumin, fibronectin, and transferring have no significant difference beween two groups (Table 2).
Table 2.
The changes of prealbumin, fibronectin and transferrin in two groups
| Group | Case | Before transfusion -x ± s | After transfusion -x ± s | Difference -x ± s | P value | |
| Prealbumin (g/L) | I | 20 | 0.467 ± 0.294 | 0.449 ± 0.305 | -0.018 ± 0.091 | 0.305 |
| II | 20 | 0.296 ± 0.239 | 0.297 ± 0.250 | 0.001 ± 0.048 | ||
| Fibronectin (g/L) | I | 20 | 2.200 ± 0.752 | 2.112 ± 0.789 | -0.085 ± 0.344 | 0.128 |
| II | 20 | 2.201 ± 0.792 | 2.345 ± 1.052 | 0.144 ± 0.735 | ||
| Transferrin (g/L) | I | 20 | 0.316 ± 0.171 | 0.335 ± 0.179 | 0.019 ± 0.211 | 0.970 |
| II | 20 | 0.276 ± 0.107 | 0.296 ± 0.524 | 0.018 ± 0.116 |
I: AA group (the formula of amino acids); II: BCAA group (the formula of amino acids enriched BCAA).
Serum levels of albumin and total protein
There is significant difference before and after study in the serum levels of albumin and total protein of two groups. As shown in Figure 2, contrast to the study group, the serum levels of total protein and albumin decreased greatly in the control group after operation (P < 0.05).
Figure 2.
The changes of total protein and albumin after infusion in two groups. aP < 0.05 vs the control group.
The change in the pattern of serum amino acid
The concentration of valine was notably increased (P = 0.02642) and that of arginine was markedly decreased (P = 0.0412) in the study group after the formula of amino acids enriched BCAA infusion when compared with the control group. In the study group, the concentrations of valine, threonine, alanine, methionine, histidine, phenylalanine and BCAA are higher after infusion than those before transfusion (P < 0.05). In the control group, the concentrations of glycine, histine and phenylalanine are higher after infusion than those before infusion (P < 0.05). (Table 3).
Table 3.
The changes of the amino acid pattern in serum after infusion
| Group | Case | Before infusion -x ± s | After infusion -x ± s | P value | Difference -x ± s | P value | |
| Asparagic acid(umol/L) | I | 20 | 0.0748 ± 0.0672 | 0.0942 ± 0.0789 | 0.2580 | 0.0194 ± 0.0638 | 0.8728 |
| II | 20 | 0.0633 ± 0.0413 | 0.0797 ± 0.0558 | 0.0999 | 0.0164 ± 0.0360 | ||
| Threonine (umol/L) | I | 20 | 0.1973 ± 0.1554 | 0.2829 ± 0.2147 | 0.0354 | 0.0856 ± 0.1424 | 0.2415 |
| II | 20 | 0.1549 ± 0.0863 | 0.3154 ± 0.2331 | 0.0065 | 0.1601 ± 0.1943 | ||
| Serine (umol/L) | I | 20 | 0.2320 ± 0.1455 | 0.2600 ± 0.1701 | 0.4696 | 0.0279 ± 0.1456 | 0.5872 |
| II | 20 | 0.1981 ± 0.1305 | 0.2518 ± 0.1576 | 0.0759 | 0.0537 ± 0.1086 | ||
| Glutacid (umol/L) | I | 20 | 0.2619 ± 0.2755 | 0.2829 ± 0.2146 | 0.8237 | 0.0209 ± 0.3574 | 0.3334 |
| II | 20 | 0.2718 ± 0.2409 | 0.4212 ± 0.3217 | 0.1275 | 0.1493 ± 0.3570 | ||
| Glycine (umol/L) | I | 20 | 0.3844 ± 0.2695 | 0.5402 ± 0.3608 | 0.0173 | 0.1558 ± 0.2237 | 0.9325 |
| II | 20 | 0.3722 ± 0.2207 | 0.5193 ± 0.3565 | 0.1028 | 0.1471 ± 0.3265 | ||
| Alanine (umol/L) | I | 20 | 0.5067 ± 0.3043 | 0.5737 ± 0.4167 | 0.5325 | 0.0669 ± 0.4053 | 0.1322 |
| II | 20 | 0.4382 ± 0.2862 | 0.7291 ± 0.5371 | 0.0111 | 0.2908 ± 0.3849 | ||
| Valine (umol/L) | I | 20 | 0.2959 ± 0.2188 | 0.2722 ± 0.2168 | 0.6596 | -0.0237 ± 0.2038 | 0.0264 |
| II | 20 | 0.2601 ± 0.1494 | 0.4599 ± 0.3765 | 0.0249 | 0.1999 ± 0.3082 | ||
| Cysteine (umol/L) | I | 20 | 0.0138 ± 0.0180 | 0.0209 ± 0.0182 | 0.1043 | 0.0057 ± 0.0127 | 0.9373 |
| II | 20 | 0.0300 ± 0.0202 | 0.0350 ± 0.0244 | 0.5238 | 0.0050 ± 0.0296 | ||
| Methionine (umol/L) | I | 20 | 0.0472 ± 0.0361 | 0.0590 ± 0.0498 | 0.3292 | 0.0118 ± 0.0452 | 0.4447 |
| II | 20 | 0.0282 ± 0.0222 | 0.0516 ± 0.0440 | 0.0253 | 0.0234 ± 0.0362 | ||
| Isoleucine (umol/L) | I | 20 | 0.1030 ± 0.0728 | 0.1298 ± 0.0874 | 0.1973 | 0.0268 ± 0.0766 | 0.7457 |
| II | 20 | 0.0825 ± 0.0586 | 0.1181 ± 0.0914 | 0.0730 | 0.0356 ± 0.0711 | ||
| Leucine (umol/L) | I | 20 | 0.2368 ± 0.1699 | 0.2496 ± 0.1694 | 0.7556 | 0.0128 ± 0.1557 | 0.3377 |
| II | 20 | 0.1770 ± 0.1113 | 0.2399 ± 0.1674 | 0.0698 | 0.0629 ± 0.1242 | ||
| Tyrosine (umol/L) | I | 20 | 0.0774 ± 0.0511 | 0.0787 ± 0.0631 | 0.9380 | 0.0014 ± 0.0659 | 0.7263 |
| II | 20 | 0.0584 ± 0.0378 | 0.0677 ± 0.0528 | 0.5343 | 0.0093 ± 0.0563 | ||
| Phenylalanine (umol/L) | I | 20 | 0.0897 ± 0.0960 | 0.1572 ± 0.1323 | 0.0289 | 0.0675 ± 0.1074 | 0.9835 |
| II | 20 | 0.0736 ± 0.0518 | 0.1418 ± 0.1277 | 0.0138 | 0.0683 ± 0.0939 | ||
| Lysine (umol/L) | I | 20 | 0.1888 ± 0.1780 | 0.2311 ± 0.1984 | 0.3706 | 0.0422 ± 0.1767 | 0.6928 |
| II | 20 | 0.1124 ± 0.1226 | 0.1836 ± 0.2403 | 0.2280 | 0.0712 ± 0.2187 | ||
| Histidine (umol/L) | I | 20 | 0.2517 ± 0.1691 | 0.2885 ± 0.2054 | 0.2654 | 0.0368 ± 0.1227 | 0.2958 |
| II | 20 | 0.1907 ± 0.1041 | 0.2756 ± 0.1778 | 0.0196 | 0.0850 ± 0.1249 | ||
| Arginine (umol/L) | I | 20 | 0.1214 ± 0.2102 | 0.2534 ± 0.5048 | 0.1584 | 0.1320 ± 0.3433 | 0.0412 |
| II | 20 | 0.2038 ± 0.4115 | 0.0480 ± 0.0678 | 0.1459 | -0.1559 ± 0.3921 | ||
| BCAA (umol/L) | I | 20 | 0.6358 ± 0.4556 | 0.6516 ± 0.4014 | 0.8631 | 0.0158 ± 0.3494 | 0.0785 |
| II | 20 | 0.5196 ± 0.3128 | 0.8180 ± 0.6279 | 0.0325 | 0.2984 ± 0.4869 |
I: AA group (the formula of amino acids); II: BCAA group (the formula of amino acids enriched BCAA).
DISCUSSION
The trauma caused by moderate or large operation may result in disturbance of glucose, lipid and protein metabolism including hypermetabolism and increased catabolism, which may lead to acute protein malnutrition, decline of immunological function and dysfunction of multiple organs[12-16]. It was reported that the supplement of the special amino acids such as arginine, BCAA and glutamine would improve recovery of patients[17-24]. Our present study was to observe the effect of the formula of amino acids enriched BCAA on patients after trauma.
In this study, we began to supplement the application of the formula of amino acid enriched BCAA on day 2 after operation to correct patients’ hypermetabolism, to normalize the pattern of plasma amino acid concentrations and to improve recovery of patients. BCAA(valine, leucine, isoleucine) can be used as the substrate for energy and glyconeogenesis and as the muscle protein regulator. BCAA can increase the intake of energy by means of oxidization into energy in the tissues without aggran dizin g the burd en of the liver . As glyconeogenesis substrate, BCAA can also be oxidized in body and produce much energy by the mechanism of circulation between oxidation and alanine synthesis[25-28]. The valine, leucine and isoleucine per gram molecular can produce 42, 43 and 32 gram molecular ATP respectively, which can supply a lot of energy to the body. The character as the source of energy for these 3 amino acids is that their first carbon can be oxidized and produce phosphate of high energy without glutamic acid, which is helpful for the decline of mechanism of producing energy with glutamic acid during trauma and stress. Because BCAA is mainly metabolized in muscle, the application of the formula of amino acid enriched BCAA can decrease the decompose of visceral protein such as muscle and liver proteins, prevent the loss of amino acids from muscle, correct negative balance, improve protein synthesis and regulate serum amino acids. In addition our results demonstrated the effect was dependent on the dose of BCAA.
Under the stress of trauma, the decompose of muscle protein seriously increases and produces a lot of free amino acids[29-33], and hyperphenylalaninaemia appears. The ratio of phenylalanine to tyrosine (phe/tyr) rises and the ratio of BCAA to aromatic amino acid (AAA) descents after trauma because of the dysfunction of liver[34,35]. The low dose of phenylalanine and the high dose of BCAA in the formula of amino acid enriched BCAA can also improve the pattern of serum amino acids after trauma.
In summary, the nitrogen balance, the synthesis of acute phase proteins and visceral proteins and the pattern of serum amino acid concentrations were measured and compared with two groups after six days of TPN after trauma. Our results demonstrated that the formula of amino acid enriched BCAA could normalize of serum amino acid levels, reduce proteolysis, increase protein synthesis and improve nitrogen balance.
Footnotes
Supported by the Natural Science Foundation of Jiangsu Province, China (No. BQ 2000014), and the Tenth Five-year Medicine Research Foundation in the CPLA (No. 01Z011)
Edited by Zhou YP
References
- 1.Liang LJ, Yin XY, Luo SM, Zheng JF, Lu MD, Huang JF. A study of the ameliorating effects of carnitine on hepatic steatosis induced by total parenteral nutrition in rats. World J Gastroenterol. 1999;5:312–315. doi: 10.3748/wjg.v5.i4.312. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 2.Wu YA, Lu B, Liu J, Li J, Chen JR, Hu SX. Consequence alimentary reconstruction in nutritional status after total gastrectomy for gastric cancer. World J Gastroenterol. 1999;5:34–37. doi: 10.3748/wjg.v5.i1.34. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 3.Cui XL, Iwasa M, Iwasa Y, Ogoshi S. Arginine-supplemented diet decreases expression of inflammatory cytokines and improves survival in burned rats. JPEN J Parenter Enteral Nutr. 2000;24:89–96. doi: 10.1177/014860710002400289. [DOI] [PubMed] [Google Scholar]
- 4.Mansoor O, Cayol M, Gachon P, Boirie Y, Schoeffler P, Obled C, Beaufrère B. Albumin and fibrinogen syntheses increase while muscle protein synthesis decreases in head-injured patients. Am J Physiol. 1997;273:E898–E902. doi: 10.1152/ajpendo.1997.273.5.E898. [DOI] [PubMed] [Google Scholar]
- 5.Vente JP, von Meyenfeldt MF, van Eijk HM, van Berlo CL, Gouma DJ, van der Linden CJ, Soeters PB. Plasma-amino acid profiles in sepsis and stress. Ann Surg. 1989;209:57–62. doi: 10.1097/00000658-198901000-00009. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 6.Wu Y, Chai J, Li J, Diao L. [The change in plasma concentration of free amino acids during early postburn stage in severely scalded rats] Zhonghua Shaoshang Zazhi. 2001;17:215–218. [PubMed] [Google Scholar]
- 7.Klein S, Kinney J, Jeejeebhoy K, Alpers D, Hellerstein M, Murray M, Twomey P. Nutrition support in clinical practice: review of published data and recommendations for future research directions. Clin Nutr. 1997;16:193–218. doi: 10.1016/s0261-5614(97)80006-4. [DOI] [PubMed] [Google Scholar]
- 8.Cao WX, Cheng QM, Fei XF, Li SF, Yin HR, Lin YZ. A study of preoperative methionine-depleting parenteral nutrition plus chemotherapy in gastric cancer patients. World J Gastroenterol. 2000;6:255–258. doi: 10.3748/wjg.v6.i2.255. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 9.Chen QP. Enteral nutrition and acute pancreatitis. World J Gastroenterol. 2001;7:185–192. doi: 10.3748/wjg.v7.i2.185. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 10.Pei WF, Xu GS, Sun Y, Zhu SL, Zhang DQ. Protective effect of electroacupuncture and moxibustion on gastric mucosal damage and its relation with nitric oxide in rats. World J Gastroenterol. 2000;6:424–427. doi: 10.3748/wjg.v6.i3.424. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 11.Boctor DL, Pillo-Blocka F, Mccrindle BW. Nutrition after cardiac surgery for infants with congenital heart disease. Nutritim Clini-cal Praetice. 1999;14:111–115. [Google Scholar]
- 12.Antonio J, Sanders MS, Ehler LA, Uelmen J, Raether JB, Stout JR. Effects of exercise training and amino-acid supplementation on body composition and physical performance in untrained women. Nutrition. 2000;16:1043–1046. doi: 10.1016/s0899-9007(00)00434-2. [DOI] [PubMed] [Google Scholar]
- 13.Wang SJ, Wen DG, Zhang J, Man X, Liu H. Intensify standardized therapy for esophageal and stomach cancer in tumor hospitals. World J Gastroenterol. 2001;7:80–82. doi: 10.3748/wjg.v7.i1.80. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 14.Dionigi P, Alessiani M, Ferrazi A. Irreversible intestinal failure, nutrition support, and small bowel transplantation. Nutrition. 2001;17:747–750. doi: 10.1016/s0899-9007(01)00630-x. [DOI] [PubMed] [Google Scholar]
- 15.Zhou HP, Wang X, Zhang NZ. Early apoptosis in intestinal and diffuse gastric carcinomas. World J Gastroenterol. 2000;6:898–901. doi: 10.3748/wjg.v6.i6.898. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 16.Zhou ZW, Wan DS, Chen G, Chen YB, Pan ZZ. Primary malignant tumor of the small intestine. World J Gastroenterol. 1999;5:273–276. doi: 10.3748/wjg.v5.i3.273. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 17.Freund HR, Hanani M. The metabolic role of branched-chain amino acids. Nutrition. 2002;18:287–288. doi: 10.1016/s0899-9007(01)00740-7. [DOI] [PubMed] [Google Scholar]
- 18.García-de-Lorenzo A, Ortíz-Leyba C, Planas M, Montejo JC, Núñez R, Ordóñez FJ, Aragón C, Jiménez FJ. Parenteral administration of different amounts of branch-chain amino acids in septic patients: clinical and metabolic aspects. Crit Care Med. 1997;25:418–424. doi: 10.1097/00003246-199703000-00008. [DOI] [PubMed] [Google Scholar]
- 19.James JH. Branched chain amino acids in heptatic encephalopathy. Am J Surg. 2002;183:424–429. doi: 10.1016/s0002-9610(02)00808-5. [DOI] [PubMed] [Google Scholar]
- 20.Bassit RA, Sawada LA, Bacurau RF, Navarro F, Martins E, Santos RV, Caperuto EC, Rogeri P, Costa Rosa LF. Branched-chain amino acid supplementation and the immune response of long-distance athletes. Nutrition. 2002;18:376–379. doi: 10.1016/s0899-9007(02)00753-0. [DOI] [PubMed] [Google Scholar]
- 21.Bruins MJ, Soeters PB, Lamers WH, Deutz NE. L-arginine supplementation in pigs decreases liver protein turnover and increases hindquarter protein turnover both during and after endotoxemia. Am J Clin Nutr. 2002;75:1031–1044. doi: 10.1093/ajcn/75.6.1031. [DOI] [PubMed] [Google Scholar]
- 22.Yin L, Li JS, Guo AQ, Liu FK, Liu FN. The prospective study of metabolic support with individual amino acids after trauma. Chinese J Surg. 1992;30:659–662. [Google Scholar]
- 23.Apovian CM. Nutritional assessment in the elderly: facing up to the challenges of developing new tools for clinical assessment. Nutrition. 2001;17:62–63. doi: 10.1016/s0899-9007(00)00479-2. [DOI] [PubMed] [Google Scholar]
- 24.Harper AE, Yoshimura NN. Protein quality, amino acid balance, utilization, and evaluation of diets containing amino acids as therapeutic agents. Nutrition. 1993;9:460–469. [PubMed] [Google Scholar]
- 25.Holecek M. Relation between glutamine, branched-chain amino acids, and protein metabolism. Nutrition. 2002;18:130–133. doi: 10.1016/s0899-9007(01)00767-5. [DOI] [PubMed] [Google Scholar]
- 26.Kouznetsova L, Bijlsma PB, van Leeuwen PA, Groot JA, Houdijk AP. Glutamine reduces phorbol-12,13-dibutyrate-induced macromolecular hyperpermeability in HT-29Cl.19A intestinal cells. JPEN J Parenter Enteral Nutr. 1999;23:136–139. doi: 10.1177/0148607199023003136. [DOI] [PubMed] [Google Scholar]
- 27.Khan J, Iiboshi Y, Cui L, Wasa M, Sando K, Takagi Y, Okada A. Alanyl-glutamine-supplemented parenteral nutrition increases luminal mucus gel and decreases permeability in the rat small intestine. JPEN J Parenter Enteral Nutr. 1999;23:24–31. doi: 10.1177/014860719902300124. [DOI] [PubMed] [Google Scholar]
- 28.Kudsk KA, Wu Y, Fukatsu K, Zarzaur BL, Johnson CD, Wang R, Hanna MK. Glutamine-enriched total parenteral nutrition maintains intestinal interleukin-4 and mucosal immunoglobulin A levels. JPEN J Parenter Enteral Nutr. 2000;24:270–274; discussion 270-274;. doi: 10.1177/0148607100024005270. [DOI] [PubMed] [Google Scholar]
- 29.Bush JA, Wu G, Suryawan A, Nguyen HV, Davis TA. Somatotropin-induced amino acid conservation in pigs involves differential regulation of liver and gut urea cycle enzyme activity. J Nutr. 2002;132:59–67. doi: 10.1093/jn/132.1.59. [DOI] [PubMed] [Google Scholar]
- 30.Meadows GG, Zhang H, Ge X. Specific amino acid deficiency alters the expression of genes in human melanoma and other tumor cell lines. J Nutr. 2001;131:3047S–3050S. doi: 10.1093/jn/131.11.3047S. [DOI] [PubMed] [Google Scholar]
- 31.Ratheiser KM, Pesola GR, Campbell RG, Matthews DE. Epinephrine transiently increases amino acid disappearance to lower amino acid levels in humans. JPEN J Parenter Enteral Nutr. 1999;23:279–287. doi: 10.1177/0148607199023005279. [DOI] [PubMed] [Google Scholar]
- 32.Baggott JE. Metabolism of methionine derived from deuterated serine infused in a human. Am J Clin Nutr. 2001;74:701–703. doi: 10.1093/ajcn/74.5.701. [DOI] [PubMed] [Google Scholar]
- 33.Klassen P, Fürst P, Schulz C, Mazariegos M, Solomons NW. Plasma free amino acid concentrations in healthy Guatemalan adults and in patients with classic dengue. Am J Clin Nutr. 2001;73:647–652. doi: 10.1093/ajcn/73.3.647. [DOI] [PubMed] [Google Scholar]
- 34.Roberts SA, Thorpe JM, Ball RO, Pencharz PB. Tyrosine requirement of healthy men receiving a fixed phenylalanine intake determined by using indicator amino acid oxidation. Am J Clin Nutr. 2001;73:276–282. doi: 10.1093/ajcn/73.2.276. [DOI] [PubMed] [Google Scholar]
- 35.de Jonge WJ, Marescau B, D'Hooge R, De Deyn PP, Hallemeesch MM, Deutz NE, Ruijter JM, Lamers WH. Overexpression of arginase alters circulating and tissue amino acids and guanidino compounds and affects neuromotor behavior in mice. J Nutr. 2001;131:2732–2740. doi: 10.1093/jn/131.10.2732. [DOI] [PubMed] [Google Scholar]