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Unité de Nutrition et Métabolisme Protéique, INRA, Centre de Clermont-Ferrand/Theix, France and * Centre de Recherche Nestlé, Lausanne. Suisse.
2To whom correspondence should be addressed. E-mail: patureau{at}clermont.inra.fr.
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ABSTRACT |
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 TOP ABSTRACT INTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
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KEY WORDS: • chronic inflammation • protein metabolism • oxidative stress • free amino acids
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INTRODUCTION |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
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). In addition, chronic inflammation is more frequent in elderly people, and is believed to play a role in the age-related loss of muscle protein (2
).
Loss of muscle protein occurs also during severe infection and acute inflammation. Acute inflammation induced by injury alters amino acid and protein metabolism (3
). Whole-body protein catabolism is stimulated during sepsis (4
), trauma (5
), burn injury (6
,7
) or endotoxin administrations (8
). Animal experiments have shown that muscle protein catabolism is increased, whereas protein synthesis is decreased (7
,9
–11
). By contrast, protein synthesis is increased in liver (7
,9
–11
), intestines (11
, 12
), spleen and lungs (11
). Amino acids released from muscle protein catabolism provide substrate for the synthesis of acute-phase proteins and proteins of the immune system (13
). The activation of these pathways results in specific nutritional requirements (13
–16
).
By contrast, the consequences of chronic inflammation on protein metabolism are much less documented especially at the tissue level. Whole-body protein turnover is increased during chronic infection (17
) and in IBD (18
), but contradictory results have been reported in celiac disease (19
,20
). IBD induced a stimulation of protein synthesis in liver and colorectal mucosa (21
), and celiac disease had similar effects in duodenum (20
). The increase of intestinal and liver protein synthesis would not explain the increases of whole-body protein turnover in IBD (22
), suggesting that protein metabolism was altered in other organs. However, there is a lack of data concerning alterations of protein metabolism in similar inflammatory situations in nonsplanchnic organs, especially in skeletal muscle.
Therefore, the aim of this study was to obtain a better understanding of perturbations of protein turnover to better define the metabolic amino acid demands in chronic inflammation (23
). Administration of dextran sulfate sodium (DSS) to rats has been shown to induce clinical symptoms (diarrhea, bloody stools and weight loss) similar to those observed in patients with IBD (24
–27
). This model has been used previously in young rats, which were given DSS in their drinking water either for a short period of time (40–100 g/L for 5 to 8 d) or for a longer period (10 g/L for several months) for pharmacologic studies (28
). We adapted doses and duration of treatment to have a chronic inflammation (>25 d), in adult rats (9 mo old), with induction of muscle mass loss and minimal suffering.
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MATERIALS AND METHODS |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
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Male Sprague-Dawley rats aged 9 mo (n = 20), weighing 575 ± 20 g (Charles River, l’Arbresle, France) were housed in individual cages at controlled temperature (22°C) with a 12-h light:dark cycle (lights on at 2200 h). They were fed a dry purified diet consisting of the following (g/kg): carbohydrate 650, protein 150 (supplied by herring meal balanced to meet all amino acid requirements), lipids 80, crude fiber 30 and minerals plus vitamins sufficient to maintain adult rats. Food was given every day at 1000 h. All rats had free access to drinking water. After a 10-d acclimation period, rats were randomly distributed into two experimental groups (n = 10). One group was treated with dextran sulfate sodium (DSS, molecular weight 36–44 kDa, ICN Biomedicals, GmbH, Eschwege, Germany) dissolved in their drinking water. DSS concentration was 50 g/L for the first 9 d; it was then decreased to 20 g/L for the following 18 d. The other group, called the pair-fed control, had no DSS in its drinking water and was fed the mean amount of food consumed by the rats of the DSS group the day before.
During the treatment, body weight and food intake, as well as the presence of blood in the stools were assessed every day. Blood samples were taken from a tail vein in the postabsorptive state at d 0, 6, 15, 23 and 27 to measure plasma acute-phase protein levels, blood cell counts, and plasma oxidized protein levels. Plasma free amino acid levels were determined in aliquots of the blood samples taken on d 27, before feeding.
At the end of treatment, 4 h after food distribution, in vivo protein synthesis rates were measured in tissues using the flooding dose method as described by Garlick et al. (29
). A flooding dose (150 µmol/100 g body, 99 atom % excess) of L-[1-13C]-valine (99 atom % excess, Eurisotop, group CEA, Saclay, France) was injected into a lateral tail vein. Tail vein blood (0.2 mL) was collected 3 min after the injection to take into account the decline of free valine enrichment during measurement. After 15 min, rats were anesthetized with sodium pentobarbital (6 mg/100 g body, Sanofi, Libourne, France). Rats were exsanguinated by sampling from abdominal aorta 20 min after valine injection; plasma was separated by centrifugation at 3000 x g at 10 min and 4°C and kept at -80°C until analysis. The following tissues were quickly removed, blotted dry, weighed, frozen in liquid nitrogen and stored at -80°C until analysis: spleen, thymus, and liver (organs involved in the inflammatory response), gastrocnemius and tibialis anterior muscles (30
), lung and kidney. The intestine was flushed with cold PBS, and the following sections were frozen in liquid nitrogen and stored at -80°C until analysis: duodenum (first 10 cm after stomach), jejunum (first two thirds of the following intestine), ileum (last one third of the small intestine), and colon (large intestine excluding cecum). Intestinal segments were sampled for histological evaluation. All procedures were performed according to current legislation on animal experimentation in France.
Analytical methods.
The presence of blood in the stools was assessed with hemoccult test (Smith Kline, Sunnyvale, CA). Blood cell counts (white and red cells, platelets and hematocrit) were determined with an automatic hematology counter (Minos, ABX, Montpellier, France) on fresh blood.
Four plasma acute-phase proteins were measured on d 0, 6, 15, 23 and 27 as follows: albumin, fibrinogen, 
1-acid glycoprotein (1-AGT) and 2-macroglobulin (2-MG). Their plasma levels were determined by single radial immunodiffusion (31
) using anti-rat fibrinogen and albumin antibodies (ICN, Cappel, Turnhout, Belgium) and anti-rat 2-MG and 1-AGT antibodies raised in rabbits in our laboratory, as already described (14
).
For the histological evaluation, the intestinal segments sampled were fixed in Bouin, dehydrated and embedded in paraffin. The slides were prepared from the paraffin blocks and stained with hematoxilin-eosin for the histological description.
Myeloperoxydase activity (MPO) has been widely accepted as a marker of the infiltration of neutrophils into tissues, and was shown to be correlated with white cell counts and associated with colon histological lesions in DSS-treated rats (28
). Hence, intestinal tissue was assayed for MPO activity as described by Krawisz et al. (32
).
The levels of plasma and gastrocnemius oxidized proteins were measured using the determination of carbonyl groups by reduction with tritiated sodium borohydride (33
). Gastrocnemius muscle was pulverized in liquid nitrogen and an aliquot (
200 mg) was homogenized in 3 mL of 4.5 mol/L NaCl, 50 mmol/L Tris, 1 mmol/L diethylenetriamine pentaacetic acid, 1 mmol/L dithiothreitol, 1 mmol/L benzamidine, pH 7.5, containing leupeptin (1 mg/L) and pepstatin (1 mg/L). After centrifugation, the supernatant was treated with streptomycin sulfate to remove nucleic acids. Protein oxidation level was given as radioactivity (dpm) per milligram protein in initial samples. Variation of the plasma level was expressed as a percentage compared with the basal value, observed on d 0 of the experiment.
Glutathione (reduced and oxidized) concentrations were assayed specifically by HPLC with fluorimetric detection of oxidized and reduced glutathione, according to Martin and White (34
). Briefly, liver and muscle samples ( 200 mg) were homogenized at 4°C in 5 mL of 0.5 mol/L perchloric acid (PCA), supplemented with 100 µL of 180 µmol/L deferoxamine, 180 µmol/L 
-phenanthroline, 50 mmol/L Hepes, pH 7.4 using a Polytron PT 3100 (16,000 rpm) for 30 s. The homogenate was then centrifuged (13,000 x g, 20 min, 4°C). To the supernatant (400 µL) was added 20 µL (10 nmol) 
-glutamyl-glutamine, used as internal standard. Samples were derivatized the same day with formation of the -carboxymethyl derivative of free thiols with iodoacetic acid followed by dansylation of free amino groups to allow fluorimetric detection. Samples are then injected onto a HPLC column (CC25014 Nucleosyl 120–7 NH2, Macherey-Nalgen, France) for analysis.
Total, free and protein-bound cysteine concentrations were measured according to Malloy et al. (35
) and Gaitonde et al. (36
). Plasma free amino acids concentrations were measured by ion-exchange chromatography, using an automated amino acid analyzer (Biotronic LC 3000, Roucaire, Vélizy, France, with BTC 2410 resin) (37
,38
).
Determination of in vivo protein synthesis rates by the flooding dose method requires measurement of 13C enrichment of free and protein-bound valine (29
). Frozen tissues were homogenized either directly in a Potter in 8 volumes of ice-cold 0.6 mol/L trichloroacetic acid, or after being finely pulverized in liquid nitrogen in a ball mill (Dangoumeau, Prolabo, Paris, France). The acid-soluble fraction containing free amino acid was separated from the protein precipitate by centrifugation (5000 x g, 15 min, 4°C). Supernatants containing free amino acids were desalted by cation-exchange chromatography (AG 50x8, 100–200 mesh, H+ form, Bio-Rad, Richmond, CA) in disposable minicolumns. Amino acids, eluted with 4 mol/L NH4OH were dried under vacuum and resuspended in 0.1 mol/L HCl for the determination of tissue free valine enrichment. This was performed by gas chromatography/mass spectrometry (GC-MS, Hewlett-Packard, Paris, France). Valine was measured as the tertiary butyl-dimethylsilyl derivative under electron impact ionization with selective ion-monitoring.
The tissue protein precipitates were washed four more times in 0.2 mol/L perchloric acid and finally incubated for 1 h at 37°C in 0.3 mol/L NaOH to solubilize proteins and to extract tissue RNA. Protein content was measured in weighed aliquots according to Smith et al. (39
) by the colorimetric reaction with bincinchoninic acid. Solubilized proteins were precipitated with 2 mol/L PCA and, after centrifugation (5000 x g, 15 min, 4°C), the supernatant RNA concentration was determined using the method described by Munro and Fleck (40
), or for muscle RNA by Manchester and Harris (41
). The protein precipitate was then used to measure incorporation of [13C]valine into tissue proteins, by GC-combustion-isotope ratio mass spectrometry (Isochrom Fisons Instruments, Manchester, UK) according to Yarasheski et al. (42
). Briefly, protein precipitate was hydrolyzed in 6 mol/L HCl for 48 h at 110°C, filtered, desalted and dried. N-Acetyl propyl derivatives of valine were separated from other amino acids and the valine derivative was directed through the furnace, where combustion in CO2 occurred.
The fractional synthesis rates in tissues (FSR, defined as the percentage of tissue protein synthesized each day, i.e., %/d) were then calculated from the following formula: FSR = 100 x (Eb - En)/(E'a x t), where t is the time interval between the end of the bolus injection and the killing of rats (incorporation period expressed in days); En is the natural enrichment of protein-bound valine, measured on additional rats; Eb is the enrichment of protein-bound valine at the end of the incorporation period; and E'a is the 13C enrichment of free valine calculated at a time half-way between injection and killing, to take into account the decline in Ea during measurement. In plasma, an initial Ea level was measured from a sample taken 3 min after injection. The change in plasma Ea was assumed to be linear over the experimental period and a mean plasma E'a was calculated. Tissue E'a was then calculated by subtracting the difference between final plasma and tissue enrichments from plasma E'a (14
). Absolute synthesis rates (ASR, mg/d or g/d) were calculated by multiplying FSR by total tissue protein content.
Data analysis.
Data are given as means ± SEM, n = 10 rats/group. Comparisons between treated and pair-fed control rats were performed by unpaired bilateral Student’s t test when variances were not different and otherwise by the nonparametric Mann-Whitney test. Comparisons of plasma parameters during DSS-treatment to initial values (Figs. 2
and 3)
were performed by paired bilateral Student’s t test. All analyses were performed using the SAS StatView package (StatView for windows version 5.0, SAS Institute Cary, NC). Significant differences were defined at P < 0.05.
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RESULTS |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
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Loose stools were observed within 3 d after the start of DSS treatment. Diarrhea with bloody stools was first seen for all of the treated rats on d 5 of treatment, i.e., during the first period when the higher dose of DSS was administered (50 g/L). During the second period of treatment (DSS, 20 g/L), diarrhea was still observed but stools were only sporadically bloody.
Food intake did not differ between the two groups during treatment. A decrease in food intake was observed progressively from d 1 to 8, with a minimum intake that reached 50% of the initial intake on d 5 and 6. Then it increased and reached initial values at d 20. Immediately after the beginning of DSS treatment, rats started to loose weight, and did so until d 15 of the treatment (Fig. 1
). Body weight loss was greater in the treated rats compared with their pair-fed controls. At the end of the experiment, body weight loss of DSS-treated rats represented 17% of their initial body weight. Of this loss, 7% could be explained by food intake reduction (pair-fed controls). The remaining 10% corresponded to a specific body weight loss induced by DSS treatment (Fig. 1)
. This loss did not involve liver, lung and kidney (no fresh weight changes), nor spleen and intestine (fresh weights increased by 20–50% in treated rats compared with their pair-fed control rats) (Table 1
). By contrast, gastrocnemius and tibialis anterior weights were significantly lower in the treated rats (11 and 10%, respectively).
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On d 15, a significant increase was observed in the number of leukocytes (+108% compared with d 0) and in the number of blood platelets (+62% compared with d0) as well as a slight decrease of hematocrit (-17%). There was no further change thereafter (Fig. 2A
). For the treated rats, the acute-phase protein response was at a maximum between d 15 (1-AGT) and d 21 (2-MG). Elevated levels persisted until the end of the experiment, with partial normalization on d 27 (Fig. 2
B). On the contrary, the effect of treatment on fibrinogen and albumin plasma levels was minor. The fibrinogen level was significantly increased on d 6 and the albumin level decreased on d 15, but on other days, levels did not differ from initial levels (data not shown). Colon MPO activity was significantly higher in DSS rats than in pair-fed control rats (143.0 U/g protein vs. 1.4). On the contrary, in the other intestinal sections (duodenum, jejunum and ileum), MPO activity was undetectable in all groups (data not shown).
Oxidative status in plasma, liver, and muscle.
Oxidatively modified plasma proteins were increased in treated rats from d 5, compared with d 0 (considered as basal values) until the end of the treatment. The greatest increase (14.5%) was observed on d 21. A trend for normalization was observed during the last week of treatment (Fig. 3
). At the end of treatment, there was no significant difference in the carbonyl content of gastrocnemius muscle proteins in treated rats compared with the pair-fed controls (224,713 ± 19,680 dpm/mg for the treated rats; 252,109 ± 18,810 dpm/mg for the pair-fed control rats).
Treatment increased total and reduced liver glutathione (23.7% compared with their pair-fed controls), but decreased total and reduced muscle glutathione (17.3%), without any effect on the oxidized form of glutathione in either tissue. Glutathione concentrations in ileum did not differ between groups (Table 2
).
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Plasma free leucine, methionine, phenylalanine, valine and glutamine levels were lower in treated rats than in pair-fed controls. By contrast, treated rats had higher plasma levels of free alanine, citrulline, glutamate, glycine, proline, serine, taurine, lysine and threonine than pair-fed controls (Table 3
).
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Tissue protein metabolism.
Intestinal tissues (Table 4
).
The effect of DSS treatment on fresh weight, protein mass and RNA content was generally similar in the different parts of the intestines, i.e., they were increased or maintained despite a decrease in whole-body weight. However, the effects on protein synthesis were different depending on the intestinal section, and were greatest in the colon. The colon fresh weight was significantly higher (26%) in the treated rats than in pair-fed controls (Table 1)
. This difference was not related to protein contents because they did not differ between the groups, and yet protein ASR was significantly higher (63%) in the treated rats than in pair-fed controls. This could be explained by the higher RNA pool size (77%) despite a lower ribosomal efficiency (kRNA) in treated rats than in pair-fed controls. In ileum, DSS treatment also had marked effects. Fresh tissue weights were higher (21%) in the treated rats than in pair-fed controls. This could result from the difference between protein contents (28%). But the differences between protein ASR in treated rats and in pair-fed controls (40%) were even greater than the difference in protein contents. As observed in colon, the higher ASR of the treated rats appeared to be a consequence of the larger RNA pool size because kRNA did not differ between groups. DSS treatment had no effect in jejunum, except on ribosomal capacity and kRNA. Duodenum fresh weight was higher (28%) in treated rats than in pair-fed controls. This was in relation with the difference between protein contents (19%). This difference could not result from differences in protein synthesis activities; like in jejunum, ASR did not differ between groups despite a lower kRNA in treated rats because they had a larger RNA pool.
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).
Spleen was dramatically affected by DSS treatment, and all variables measured were higher in the treated rats than in their pair-fed controls. Treatment increased organ weight (Table 1)
and protein and RNA contents (50, 46 and 163% respectively). RNA efficiency was also higher (23%) and this resulted in a very marked increase of ASR (227%). Liver fresh weights (Table 1)
and protein contents did not differ between the groups. Protein ASR was also unaffected by treatment, but FSR was significantly higher (30%). This could result from a higher RNA content (39%), whereas kRNA was unaffected. In lung, most of treatment effects on protein metabolism were similar to those in liver but they were less marked and were significant only for the RNA-related variables. In kidney, treatment had only minor effects on organ weights (Table 1)
and protein contents. Protein ASR did not differ between the groups. This was consistent with the fact that the lower ribosomal efficiency in treated rats was compensated for by a larger RNA pool size, as in most splanchnic organs.
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A significant atrophy of gastrocnemius muscle (-11%) (Table 1)
and a tendency for a lower protein content (-8%, P = 0.14) were observed in DSS-treated rats. This corresponded in part to the effect of treatment observed on protein ASR. It was significantly lower (-23%) in the treated rats than in pair-fed controls on account of lower ribosomal efficiency (-20%). |
DISCUSSION |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
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To study the disturbances of protein metabolism in chronic inflammatory diseases, we developed a model of DSS-induced colitis in adult rats. The DSS treatment was adjusted for adult rats by combining first a period of injury induction (50 g/L DSS for 9 d), and second a maintenance period of the injury, which resulted in a chronic inflammation (20 g/L DSS for 3 wk). DSS is widely used to induce a rapid and acute form of colitis in rats, mice or hamsters, that shows similarities with IBD in humans. The mechanisms by which DSS induces colitis are still unknown, and several hypotheses have been detailed in the literature (28
,43
–45
). We adapted the DSS-induced colitis model currently described to obtain a more chronic inflammatory state in adult rats. The pattern of clinical symptoms observed in this study (i.e., wasting, histological lesions, intestinal MPO activity, diarrhea and bloody stools) were in agreement with the previous studies using this model in growing rats (46
, 47
). All positive markers of inflammation (leukocytes, platelets, 1-AGT and 2-MG) were greatly increased during the induction phase, and a persistent inflammatory state was maintained throughout the chronic period of treatment. The histological analysis (data not shown) of the different portions of the gastrointestinal tract showed inflammatory alterations localized in the colon mucosa alone. The latter exhibited a hypertrophy of muscular mucosa and sometimes ulcers. The lesions consisted of an atrophy of crypts and their replacement by inflammatory tissue with fibrosis and prominent vessel neoformation.
The increase in plasma oxidized proteins in DSS-treated rats indicated that the treatment induced oxidative stress at the systemic level. It was initiated during the period with the highest dose of DSS and persisted until the end of the treatment. Similar results have been reported in patients with celiac disease (48
). The oxidative stress is linked with the stimulation of the immune system (45
). Rebamipide, a drug that inhibits the production of free radicals, was shown to act as a direct anti-inflammatory agent in chronic DSS-induced colitis (28
). The control of oxidative stress implies multiple antioxidant mechanisms. Glutathione is one of the most important antioxidant and reducing agents of the body (49
). In IBD, studies in humans have shown contradictory results concerning GSH levels in the target site of the diseases (50
–52
). In rats with chronic inflammation induced by DSS, ileum GSH was unaffected and liver GSH was higher in the treated group than in controls. This increased liver GSH may be due to a higher synthesis rate as seen in many diseases (49
) and could induce lower plasma cysteine and methionine levels. Plasma levels of taurine, a cysteine metabolite with antioxidant properties, were higher in the treated rats, also suggesting an increased utilization of cysteine. Therefore, sulfur amino acids could be limiting, as has been described in acute infection (53
) and in chronic HIV infection (37
,54
). As a consequence, they would not be available for maintaining the muscle glutathione level, which was decreased in DSS rats, as during the final period of acute inflammation (49
). A similar situation was described in young pigs during acute inflammation induced by turpentine injection, i.e., a low protein diet did not maintain reduced glutathione erythrocyte levels (55
). Taken together, these results indicate that the splanchnic organs have priority over muscle for nutrient utilization during chronic inflammation.
As expected, DSS treatment severely affected colon protein metabolism. There was an increase in protein turnover likely involving both protein synthesis and protein losses because tissue protein masses were not modified despite a large increase in protein synthesis, as already described in other chronic intestinal diseases (20
,21
). Those losses could be the consequence of local injury, cell losses, increased protein secretion and degradation. A similar protein synthesis stimulation was detected in ileum. In contrast, protein synthesis was unaffected in jejunum and duodenum. In any case, assuming that cecum protein synthesis changes were similar to those in colon, the amount of daily synthesized protein in the whole intestine was increased by 10%. Such an increase is less than that described during acute inflammation induced by turpentine (10
) or by sepsis (11
,12
). Alterations in protein synthesis in other organs were observed after DSS-induced inflammation, as already observed in both acute (56
) or more chronic diseases (21
). The response of spleen to DSS treatment was characterized by a sharp increase in protein synthesis rate (+330%), but in this case was lower than in acute inflammation states such as sepsis (11
). This increase in protein synthesis rate was much greater than the increase in spleen protein content (+45%), indicating that spleen protein loss (proteolysis, exportation via erythrocytes) was also considerable during chronic inflammation. By contrast, the effect of chronic inflammation on protein metabolism in liver and lungs was much less marked than in acute inflammation. This is consistent with variations of the acute-phase protein levels that were much lower than in acute injury (11
,14
).
In the gastrocnemius muscle, DSS treatment decreased protein ASR as has been described in acute inflammation (7
,14
). Because the decrease in muscle protein content (-7%) was less than the decrease in protein synthesis (-23%), we assume that protein degradation was reduced simultaneously. In fact, most muscle protein losses occurred during the first days of the treatment, corresponding to the acute phase of injury. Indeed, muscle weights measured at d 14 in an additional experiment (data not shown) were similar to those observed at the end of the present experiment. This indicates an inhibition of muscle protein degradation between d 14 and 27 similar to the inhibition of protein synthesis observed at the end of the chronic period. The low muscle protein turnover could limit muscle protein loss during the chronic period, but also prevent recovery of the losses that occurred during the acute phase. Therefore, by contrast with acute inflammation (14
), after 4 wk of DSS treatment, muscle protein cannot be considered to be a source of amino acids for splanchnic organs (spleen, liver and intestines). Rather, the lower muscle protein turnover could be a consequence of lower amino acid availability at the peripheral level illustrated by the free plasma levels of methionine, valine, leucine and phenylalanine, which were significantly lower in treated rats than in pair-fed controls. This decreased availability of peripheral amino acids could be a consequence of the stimulation of protein synthesis that occurs at the splanchnic level. This relative deficiency in several indispensable amino acids during this chronic phase suggests that there are specific amino acid requirements.
In conclusion, this experiment demonstrates that the chronic inflammation induced by DSS in adult rats is associated with substantial perturbations in protein metabolism. Two periods can be distinguished. During the induction period, phenomena are likely to be similar to those described during the acute phase of sepsis. During the chronic period that follows, protein synthesis remains increased in several splanchnic organs (spleen and intestines) and oxidative protein alterations such as during acute inflammation persist, but to a lesser extent. In contrast, muscle protein turnover is reduced. This indicates a muscle protein sparing mechanism, probably in response to lower amino acid availability at the peripheral level. Therefore, amino acid requirements would be increased during chronic inflammation. Further studies are required to explore the beneficial effect of dietary supplementation on muscle recovery.
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ACKNOWLEDGMENTS |
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FOOTNOTES |
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3 Abbreviations used: 1-AGT, 1-acid glycoprotein; 2-MG, 2-macroglobulin; ASR, absolute synthesis rate; DSS, dextran sulfate sodium; FSR, fractional synthesis rate; GC, gas chromatography; IBD, inflammatory bowel disease; kRNA, ribosomal efficiency; MPO, myeloperoxydase activity; PCA, perchloric acid.
Manuscript received 26 November 2001. Initial review completed 22 January 2002. Revision accepted 11 March 2002.
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LITERATURE CITED |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
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