Citrulline protects human retinal pigment epithelium from hydrogen peroxide and iron/ascorbate induced damages.

Oxidative stress plays an important role in the ageing of the retina and in the pathogenesis of retinal diseases such as age-related macular degeneration (ARMD). Hydrogen peroxide is a reactive oxygen species generated by the photo-excited lipofuscin that accumulates during ageing in the retinal pigment epithelium (RPE), and the age-related accumulation of lipofuscin is associated with ARMD. Iron also accumulates with age in the RPE that may contribute to ARMD as an important source of oxidative stress. The aim of this work was to investigate the effects of L-Citrulline (CIT), a naturally occurring amino acid with known antioxidant properties, on oxidative stressed cultured RPE cells. Human RPE (ARPE-19) cells were exposed to hydrogen peroxide (H2 O2 ) or iron/ascorbate (I/A) for 4 h, either in the presence of CIT or after 24 h of pretreatment. Here, we show that supplementation with CIT protects ARPE-19 cells against H2 O2 and I/A. CIT improves cell metabolic activity, decreases ROS production, limits lipid peroxidation, reduces cell death and attenuates IL-8 secretion. Our study evidences that CIT is able to protect human RPE cells from oxidative damage and suggests potential protective effect for the treatment of retinal diseases associated with oxidative stress.

Dose-dependent beneficial effects of citrulline supplementation in short bowel syndrome in rats.

OBJECTIVES: Supplementing diet with citrulline has proved an efficient means of preserving nitrogen balance and improving nutritional status after massive intestinal resection. The aim of this study was to model the action of citrulline in gut-resected rats using a dose-ranging study focused on skeletal muscle nitrogen homeostasis. METHODS: Forty-six rats were randomly assigned to one of the following groups: citrulline 0.5 g·kg·d-1 (n = 9), citrulline 1 g·kg·d-1 (n = 7), citrulline 2.5 g·kg·d-1 (n = 8), citrulline 5 g·kg·d-1 (n = 8), control (n = 6), and sham (n = 8). The sham group underwent transection and the other groups underwent resection of 80% of the small intestine. All rats were then fed enteral nutrition (EN; all diets were isocaloric and isonitrogenous). After 10 d, the rats were sacrificed to measure and analyze animal weight; duodenum, jejunum, and ileum weight; and muscle trophicity. Protein fractional synthesis rate (FSR) and mammalian target of rapamycin complex (mTORC)1 activation were measured in the tibialis muscle. RESULTS: There was a significant dose-dependent association between rat weight and citrulline dose up to 2.5 g·kg·d-1 (P = 0.004). There was a significant improvement in tibialis weight correlated to plasma citrulline. Net protein FSR in the tibialis tended to be greater after resection and tended to return to baseline after citrulline supplementation. Citrulline supplementation significantly decreased the activated phosphorylated forms of S6 K1 (P = 0.003) and S6 RP (P = 0.003), with a significant positive association between myofibrillar FSR and activation of S6 K1 (r = 0.614; P = 0.02) and S6 RP (r = 0.601; P = 0.023). Jejunum weight was significantly positively correlated with plasma citrulline (r = 0.319; P = 0.0345). CONCLUSION: Citrulline promotes body weight gain, preserves muscle trophicity, and enhances intestinal adaptation in a dose-dependent manner in a model of resected rats.

L-Citrulline Supports Vascular and Muscular Benefits of Exercise Training in Older Adults.

Age-associated reduction in endothelial nitric oxide (NO) synthesis contributes to the development of cardiovascular diseases and sarcopenia. L-Citrulline is a precursor of NO with the ability to improve vascular function and muscle protein synthesis. We hypothesize that vascular and muscular benefits associated with oral L-citrulline supplementation might be augmented by concomitant supplementation with exercise training in older adults.

Amino acids and sport: a true love story?

Among a plethora of dietary supplements, amino acids are very popular with athletes for several reasons (e.g., to prevent nutritional deficiency, improve muscle function, and decrease muscle damages) whose purpose is to improve performance. However, it is difficult to get a clear idea of which amino acids have real ergogenic impact. Here, we review and analyze the clinical studies evaluating specific amino acids (glutamine, arginine, leucine, etc.) in athletes. Only english-language clinical studies evaluating a specific effect of one amino acid were considered. Despite promising results, many studies have methodological limits or specific flaws that do not allow definitive conclusions. To date, only chronic ß-alanine supplementation demonstrated an ergogenic effect in athletes. Much research is still needed to gain evidence-based data before any other specific amino acid can be recommended for use in athletes.

Synergistic effects of citrulline supplementation and exercise on performance in male rats: evidence for implication of protein and energy metabolisms.

Background: Exercise and citrulline (CIT) are both regulators of muscle protein metabolism. However, the combination of both has been under-studied yet may have synergistic effects on muscle metabolism and performance. Methods: Three-month-old healthy male rats were randomly assigned to be fed ad libitum for 4 weeks with either a citrulline-enriched diet (1 g·kg-1·day-1) (CIT) or an isonitrogenous standard diet (by addition of nonessential amino acid) (Ctrl) and trained (running on treadmill 5 days·week-1) (ex) or not. Maximal endurance activity and body composition were assessed, and muscle protein metabolism (protein synthesis, proteomic approach) and energy metabolism [energy expenditure, mitochondrial metabolism] were explored. Results: Body composition was affected by exercise but not by CIT supplementation. Endurance training was associated with a higher maximal endurance capacity than sedentary groups (P<0.001), and running time was 14% higher in the CITex group than the Ctrlex group (139±4 min versus 122±6 min, P<0.05). Both endurance training and CIT supplementation alone increased muscle protein synthesis (by +27% and +33%, respectively, versus Ctrl, P<0.05) with an additive effect (+48% versus Ctrl, P<0.05). Mitochondrial metabolism was modulated by exercise but not directly by CIT supplementation. However, the proteomic approach demonstrated that CIT supplementation was able to affect energy metabolism, probably due to activation of pathways generating acetyl-CoA. Conclusion: CIT supplementation and endurance training in healthy male rats modulates both muscle protein and energy metabolisms, with synergic effects on an array of parameters, including performance and protein synthesis.

Nitric oxide production by peritoneal macrophages from aged rats: A short term and direct modulation by citrulline.

Citrulline has anti-inflammatory properties and exerts beneficial effects on various impaired functions in aging. However, there are few data on citrulline action on immune function in aged populations. The objective of the study was to evaluate citrulline ability, after in vivo and in vitro administration, to modulate macrophage functions in aged rats and the possible pathways involved. Twenty-one-month-old Sprague-Dawley rats (n = 27) received a citrulline supplementation at 5 g/kg/d for 5 days, or an isonitrogenous diet, and peritoneal macrophages were cultured with or without LPS. In the in vitro study, macrophages from 22-month-old rats (n = 16) were cultured with or without LPS, citrulline and inhibitors of different inflammatory pathways (n = 8/conditions). Nitric oxide (NO) and tumor necrosis factor α (TNFα) production were measured in both in vivo and in vitro studies. Citrulline decreased NO production variability by peritoneal macrophages after in vivo administration (p = 0.0034) and downregulated NO production by 22% after in vitro administration (95% CI: [6%; 35%]; p = 0.0394), without any direct effect on TNFα production. None of the transductional pathways explored seem to be involved. Citrulline slightly modulates NO production in vivo and in vitro, suggesting a possible action through modulation of arginine metabolism in macrophages rather than a direct transductional effect. The pleiotropic effects of citrulline in aging could be due, at least in part, to the anti-inflammatory effect of citrulline.

Regulation of the proteome by amino acids.

Besides their main contribution as substrates for protein synthesis, amino acids as signaling molecules could exert some regulatory functions on protein synthesis and/or proteolysis that have been emphasized in a number of recent studies. Several publications have highlighted supplemental roles of those amino acids in protein metabolism as well as in immunity, heat shock response, or apoptosis processes. In this way, via their regulatory properties, selected amino acids (such as leucine, glutamine, arginine, citrulline, or methionine) directly influence the proteome. In this review, we are proposing an overview of the regulation of the proteome by amino acids in mammals.

Citrulline Supplementation Induces Changes in Body Composition and Limits Age-Related Metabolic Changes in Healthy Male Rats.

BACKGROUND: Aging is associated with profound metabolic disturbances, and citrulline may be of use to limit them. OBJECTIVE: The aim of this work was to evaluate the long-term effect of citrulline supplementation on metabolism in healthy aged rats. METHODS: Twenty-month-old male rats were randomly assigned to be fed (ad libitum) for 12 wk with either a citrulline-enriched diet (1 g ⋅ kg(-1) ⋅ d(-1)) or a standard diet [rendered isonitrogenous by addition of nonessential amino acids (NEAAs)]. Motor activity and muscle strength were measured, body composition was assessed, and muscle metabolism (protein structure, mitochondrial exploration, and transductional factors) and lipid metabolism (lipoprotein composition and sensitivity to oxidative stress) were explored. RESULTS: Compared with the NEAA-treated group, citrulline supplementation was associated with lower mortality (0% vs. 20%; P = 0.05), 9% higher lean body mass (P < 0.05), and 13% lower fat mass (P < 0.05). Compared with the NEAA-treated group, citrulline-treated rats had greater muscle mass (+14-48% depending on type of muscle; P < 0.05 for tibialis, gastrocnemius, and plantaris). Susceptibility to oxidation of lipoproteins, as measured by the maximal concentration of 7-ketocholesterol after copper-induced VLDL and LDL oxidation, was lower in citrulline-treated rats than in NEAA-treated rats (187 ± 8 µmol/L vs. 243 ± 7 µmol/L; P = 0.0005). CONCLUSIONS: Citrulline treatment in male aged rats favorably modulates body composition and protects against lipid oxidation and, thus, emerges as an interesting candidate to help prevent the aging process.

Citrulline induces fatty acid release selectively in visceral adipose tissue from old rats.

SCOPE: During aging, increased visceral adipose tissue (AT) mass may result in impaired metabolic status. A citrulline (CIT)-supplemented diet reduces AT mass in old rats. We hypothesized that CIT could directly affect fatty acid (FA) metabolism in retroperitoneal AT. METHODS AND RESULTS: A 24-h exposure of AT explants from old (25 months) rats to 2.5 mM CIT induced a 50% rise in glycerol and FA release, which was not observed in explants from young (2 months) animals. The phosphorylated form of hormone-sensitive lipase, a key lipolytic enzyme, was 1.5-fold higher in CIT-treated explants from old and young rats, whereas glyceroneogenesis, that provides glycerol-3P requested for FA re-esterification, and its key enzyme phosphoenolpyruvate carboxykinase, were down-regulated 40-70%. Specifically in young rats, beta-oxidation capacity and gene expressions of carnitine palmitoyl transferase 1-b and very long chain acyl-CoA dehydrogenase were strongly up-regulated by CIT. In contrast, in old rats, while glyceroneogenesis was lower, beta-oxidation was not affected, enabling increased FA release. CONCLUSION: Hence, in visceral AT, CIT exerts a specific induction of the beta-oxidation capacity in young rats and a selective stimulation of FA release in old rats, therefore providing a direct mechanism of CIT action to reduce AT mass.

Citrulline diet supplementation improves specific age-related raft changes in wild-type rodent hippocampus.

The levels of molecules crucial for signal transduction processing change in the brain with aging. Lipid rafts are membrane microdomains involved in cell signaling. We describe here substantial biophysical and biochemical changes occurring within the rafts in hippocampus neurons from aging wild-type rats and mice. Using continuous sucrose density gradients, we observed light-, medium-, and heavy raft subpopulations in young adult rodent hippocampus neurons containing very low levels of amyloid precursor protein (APP) and almost no caveolin-1 (CAV-1). By contrast, old rodents had a homogeneous age-specific high-density caveolar raft subpopulation containing significantly more cholesterol (CHOL), CAV-1, and APP. C99-APP-Cter fragment detection demonstrates that the first step of amyloidogenic APP processing takes place in this caveolar structure during physiological aging of the rat brain. In this age-specific caveolar raft subpopulation, levels of the C99-APP-Cter fragment are exponentially correlated with those of APP, suggesting that high APP concentrations may be associated with a risk of large increases in beta-amyloid peptide levels. Citrulline (an intermediate amino acid of the urea cycle) supplementation in the diet of aged rats for 3 months reduced these age-related hippocampus raft changes, resulting in raft patterns tightly close to those in young animals: CHOL, CAV-1, and APP concentrations were significantly lower and the C99-APP-Cter fragment was less abundant in the heavy raft subpopulation than in controls. Thus, we report substantial changes in raft structures during the aging of rodent hippocampus and describe new and promising areas of investigation concerning the possible protective effect of citrulline on brain function during aging.

Decreased glutamate, glutamine and citrulline concentrations in plasma and muscle in endotoxemia cannot be reversed by glutamate or glutamine supplementation: a primary intestinal defect?

Endotoxemia affects intestinal physiology. A decrease of circulating citrulline concentration is considered as a reflection of the intestinal function. Citrulline can be produced in enterocytes notably from glutamate and glutamine. The aim of this work was to determine if glutamate, glutamine and citrulline concentrations in blood, intestine and muscle are decreased by endotoxemia, and if supplementation with glutamate or glutamine can restore normal concentrations. We induced endotoxemia in rats by an intraperitoneal injection of 0.3 mg kg(-1) lipopolysaccharide (LPS). This led to a rapid anorexia, negative nitrogen balance and a transient increase of the circulating level of IL-6 and TNF-α. When compared with the values measured in pair fed (PF) animals, almost all circulating amino acids (AA) including citrulline decreased, suggesting a decrease of intestinal function. However, at D2 after LPS injection, most circulating AA concentrations were closed to the values recorded in the PF group. At that time, among AA, only glutamate, glutamine and citrulline were decreased in gastrocnemius muscle without change in intestinal mucosa. A supplementation with 4% monosodium glutamate (MSG) or an isomolar amount of glutamine failed to restore glutamate, glutamine and citrulline concentrations in plasma and muscle. However, MSG supplementation led to an accumulation of glutamate in the intestinal mucosa. In conclusion, endotoxemia rapidly but transiently decreased the circulating concentrations of almost all AA and more durably of glutamate, glutamine and citrulline in muscle. Supplementation with glutamate or glutamine failed to restore glutamate, glutamine and citrulline concentrations in plasma and muscles. The implication of a loss of the intestinal capacity for AA absorption and/or metabolism in endotoxemia (as judged from decreased citrulline plasma concentration) for explaining such results are discussed.

Leucine and citrulline modulate muscle function in malnourished aged rats.

Protein energy malnutrition in the elderly causes preferential loss of muscle mass which is associated with poor functional states. Leucine and citrulline are able to stimulate muscle protein synthesis in aged rats but no study has been undertaken to evaluate their effect on muscle function. Sprague-Dawley male rats aged 23 months were used in the experiment. Part of them were subjected to a dietary restriction for 12 weeks and then assigned to four groups: a group was euthanized (restricted group), and the others were refed for 1 week with either a leucine-, a citrulline-supplemented diet, or a standard diet. The other rats were fed ad libitum. Muscle mass and motor activity significantly increased during the refeeding with either leucine or citrulline (respectively, +51 and +37% for muscle mass, P < 0.05). The improvement of muscle mass and of motor activity induced by leucine and citrulline was highly associated with that of maximal tetanic isometric force (r = 0.769, P < 0.0001; r = 0.389, P < 0.05, respectively) but only leucine improved maximal tetanic isometric force (+101%, P < 0.05). In conclusion, this is the first study to demonstrate the ability of two amino acids (leucine and citrulline) to modulate muscle function.

TPL-2-mediated activation of MAPK downstream of TLR4 signaling is coupled to arginine availability.

The innate immune response is influenced by the nutrient status of the host. Mitogen-activated protein kinases (MAPKs), such as extracellular signal-regulated kinase 1 (ERK1) and ERK2, are activated after the stimulation of macrophages with bacterial lipopolysaccharide (LPS) and are necessary for the optimal production of proinflammatory cytokines such as tumor necrosis factor-alpha (TNF-alpha). We uncovered a role for the extracellular nutrient arginine in the activation of ERK1/2 in LPS-stimulated macrophages. Arginine facilitated the activation of MAPKs by preventing the dephosphorylation and inactivation of the MAPK kinase kinase tumor-promoting locus 2 (TPL-2). Starvation of mice decreased the concentration of arginine in the plasma and impaired the activation of ERK1/2 by LPS. Supplementation of starved mice with arginine promoted the subsequent activation of ERK1/2 and the production of TNF-alpha in response to LPS. Thus, arginine is critical for two aspects of the innate immune response in macrophages: It is the precursor used in the generation of the antimicrobial mediator nitric oxide, and it facilitates MAPK activation and consequently cytokine production.

The 2009 ESPEN Sir David Cuthbertson. Citrulline: a new major signaling molecule or just another player in the pharmaconutrition game?

Citrulline (CIT) is synthesized from arginine (ARG) and glutamine in enterocytes and metabolized by the kidneys into arginine, which is available for peripheral tissues. Thus CIT, rather than ARG, could be a limiting amino acid (AA) in situations of intestinal failure. This was verified in a rat model of short bowel syndrome. The effects of CIT were further tested in renutrition of malnourished rats and in healthy volunteers fed a hypoproteic diet. CIT supplementation improved protein synthesis (PS) and ARG availability more than ARG itself, which is explained by the fact that CIT, unlike ARG, is very efficiently transported into enterocytes and escapes hepatic uptake. Action of CIT on PS is mediated through the mTOR pathway. A key issue is why CIT should stimulate PS. CIT could be a counterpart of leucine, with leucine stimulating PS in the postprandial state, while CIT acts when protein intake is low or nil to maintain PS at a minimal level compatible with life. CIT could also be a safe way to deliver ARG to endothelial and immune cells, and can certainly prevent excessive uncontrolled nitric oxide production.

Interactions between ω3 polyunsaturated fatty acids and arginine on nutritional and immunological aspects in severe inflammation.

BACKGROUND & AIMS: Immune-enhancing diets (IEDs) contain a mixture of nutrients claimed to have immunological properties. Therefore, it seemed relevant to determine the effect of each of their components. The aim of this study was to examine the role of arginine (Arg) and ω3 polyunsaturated fatty acids (ω3 PUFAs) in the effect of an IED (Crucial(®)) in a validated rat model of inflammation induced by turpentine (TI). METHODS: Forty-two rats were randomized into five groups: AL (ad libitum), TI-EN (TI+standard enteral nutrition (EN): Sondalis(®)HP), TI-EN-Arg (TI+standard EN+Arg in equimolar concentration to Arg in the IED), TI-M-IED (TI+modified IED containing the same ω6/ω3 ratio as in standard EN) and TI-IED (TI+Crucial(®)). Blood was sampled to determine CD25 receptor density on lymphocytes. TNF-α, IL-6 and NO (production and expression) were evaluated on isolated macrophages. Mesenteric lymph nodes, spleen and liver were cultured for analysis of enterobacterial translocation and dissemination. RESULTS: CD25 density was decreased after TI and was corrected in the TI-EN-Arg, TI-M-IED and TI-IED groups (p<0.05). TI induced an alteration of macrophage mRNA expression of IL-6, TNF-α and iNOS, corrected in the TI-EN-Arg and TI-M-IED groups (p<0.05), but not by the IED. Enterobacterial translocation was observed in all treated groups, nevertheless the amount tended (p=0.054) to be lower in the TI-EN-Arg group. CONCLUSIONS: Arg and ω3 PUFAs make a major contribution to IED effects, but our study shows interaction between them on macrophage reactivity. This indicates that the individual properties of each pharmaconutrient are not additive in IEDs.

Impairment of arginine metabolism in rats after massive intestinal resection: effect of parenteral nutrition supplemented with citrulline compared with arginine.

Arginine homoeostasis is impaired in short bowel syndrome, but its supplementation in short bowel syndrome patients remains controversial. Recently, we demonstrated the benefits of citrulline supplementation by the enteral route in resected rats. Since the first step in managing short bowel syndrome is to initiate total parenteral nutrition, we hypothesized that parenteral citrulline supplementation would be more appropriate in this situation than arginine supplementation. In the present study, 24 rats were assigned to four groups. The sham group underwent transection whereas the three other groups underwent resection (R) of 80% of the small intestine. All rats were then fed exclusively by total parenteral nutrition as follows: supplementation with citrulline (R+CIT), with arginine (R+ARG) or no supplementation (R). All of the rats received isocaloric and isonitrogenous nutrition for 4 days. Nitrogen balance was measured daily. Rats were then killed and the blood was collected and the intestinal mucosa and extensor digitorum longus muscle were removed for amino acid and protein analysis. Citrulline and arginine increased mucosal protein content in the ileum (compared with sham and R, P<0.05). However, only citrulline prevented extensor digitorum longus atrophy (R+CIT, 130+/-3 mg compared with R, 100+/-6 mg and R+ARG, 110+/-2 mg, P<0.05). In addition, arginine worsened nitrogen balance (R+ARG, 104+/-46 mg/72 h compared with R, 249+/-69 mg/72 h, P<0.05). Only citrulline was able to prevent muscle atrophy and it was achieved independently from any noticeable effect on the gut in particular because citrulline and arginine share the same effect on mucosal ileal protein content. These results suggest that citrulline should be considered as a potential supplement for total parenteral nutrition of short bowel syndrome patients.

Effect of an immune-enhancing diet on lymphocyte in head-injured rats: what is the role of arginine?

OBJECTIVE: The benefit of immune-enhancing diets (IEDs) in the intensive care unit remains controversial. Considering their complexity, the role of each component, in particular arginine (Arg), in their properties is largely unknown. The aim of this study was to determine the role of arginine in the immunomodulatory effects of an IED (Crucial) in head-injured rats. DESIGN: Thirty-four rats were randomized into five groups: AL (ad libitum), HI (head-injured), HI-STD (HI + standard enteral nutrition, EN), HI-STD-Arg (HI + standard EN + Arg in equimolar concentration to Arg in IED), and HI-IED (HI + IED). These isocaloric and isonitrogenous diets were administered over 4 days. After death, the thymus was removed and weighed. The density of CD25, CD4 and CD8 on lymphocytes from blood and from Peyer patches was evaluated. Mesenteric lymph nodes, liver and spleen were cultured for analysis of enterobacterial translocation and dissemination. MEASUREMENTS AND RESULTS: HI induced an atrophy of the thymus which was not corrected by the standard diet (HI 0.27 +/- 0.03, HI-STD 0.35 +/- 0.03 vs. AL 0.49 +/- 0.02 g; p < 0.05). However, the standard diet supplemented with arginine limited the thymic atrophy and the IED restored thymus weight. CD25 density and interleukin-2 production were increased only in the HI-STD-Arg and HI-IED groups (p < 0.05). Head injury induced enterobacterial translocation and dissemination which were blunted only in the HI-STD-Arg group (p < 0.05). CONCLUSIONS: In this rat HI model, arginine appears to be safe, contributes to a large extent to the immunomodulatory effects of the IED, and seems to limit enterobacterial translocation and dissemination more efficiently alone than in an IED.

L-arginine plus atorvastatin for prevention of atheroma formation in genetically hypercholesterolaemic rabbits.

We investigated the combined effect of dietary supplementation with L-arginine, which is the precursor of NO, and pharmacological treatment with atorvastatin, which is a 3-hydroxy-3-methylglutaryl (HMG)-CoA reductase inhibitor, on the development of atherosclerosis in homozygous Watanabe heritable hyperlipidaemic rabbits. Rabbits were fed either standard rabbit chow (group C; n 9) as control, a 1.5 % L-arginine diet (group A; n 9), standard rabbit chow plus atorvastatin (2.5 mg/kg per d) in drinking water (group S; n 8), or standard rabbit chow plus a 1.5 % L-arginine diet with atorvastatin (group SA; n 8). Blood was sampled at 2-week intervals. After 8 weeks (T8), the aorta was harvested for topographic and histological analysis. Only the SA group showed decreases in total area of lesions (21 %) and the area of abdominal lesions (44 %) compared with the control group (P = 0.019). Furthermore, plaques in the SA group were smaller and less thick than those observed in the S group. Unexpectedly, plasma nitrite + nitrate levels were not modified under either the L-arginine diet alone or under L-arginine plus atorvastatin. The present study is the first to demonstrate that diet supplementation with L-arginine associated with a statin (atorvastatin) is more efficient in reducing lesion size than treatment with L-arginine or a statin alone. This is a relatively novel therapeutic approach associating a macronutrient and a drug.

Impairment of lymphocyte function in head-injured rats: effects of standard and immune-enhancing diets for enteral nutrition.

BACKGROUND: The metabolic response to head injury (HI) is characterized by a dysimmunity which may be a risk factor of a septic state. The use of immune enhancing diets (IEDs) could be a promising approach to improve immune functions. The aim of the study was to investigate the consequences of HI on lymphocyte function and to determine the effects of an enteral IED comparatively to a standard enteral nutrition. METHOD: A rat model of HI by fluid percussion was used. Twenty-five male Sprague-Dawley rats were randomized into 4 groups: rats receiving standard chow diet ad libitum (AL), rats sustaining HI and receiving standard chow diet and enteral saline (HI), rats receiving the enteral standard diet Sondalis HP (HIS), and rats receiving the IED Crucial (HIC). The two enteral diets were infused continuously during 4 days after the HI and were isocaloric, isonitrogenous and isovolumic. RESULTS: HI induced a thymus atrophy (HI vs. AL, P<0.05), and an impairment in lymphocyte CD25 receptor density responsiveness to stimulation. The IED blunted thymus atrophy and allowed to preserve the stimulation of blood and Peyer patches lymphocytes (HIC: Stimulated vs. Basal, P<0.05). CONCLUSION: IED seems more adapted for preserving lymphocyte function than standard diet in HI patients.

Pretreatment of starved rats with ornithine alpha-ketoglutarate: effects on hepatic mRNA levels and plasma concentrations of three liver-secreted proteins.

OBJECTIVE: Ornithine alpha-ketoglutarate (OKG) displays anabolic properties at the hepatic level, but the mechanisms involved remain unclear. This study investigated in vivo the ability of OKG to modulate hepatic gene expression of three liver-secreted proteins: albumin, transthyretin, and retinol binding protein. METHODS: One hundred eighty rats were fed for 5 d with a balanced regimen enriched with OKG (5 g.kg(-1).d(-1)) or an isonitrogenous mixture (alanine, glycine, and serine). Hepatic mRNA levels and plasma concentrations of the three proteins studied were determined at the end of the nutrition period and after 1, 2, and 3 d of food deprivation. Results were compared by analysis of variance and Bonferroni-Dunn tests. RESULTS: At the end of the nutrition period, hepatic mRNA levels and plasma concentrations of the three proteins were not modified by OKG supplementation. However, OKG largely increased mRNA levels of albumin, transthyretin, and retinol binding protein on the first day of starvation compared with control animals (+68%, +64% and +51%, respectively; P < 0.01 versus control). OKG precociously increased albuminemia (on day 2) but had no effect on plasma concentrations of transthyretin and retinol binding protein. Neither regulation of polyamine hepatic concentration nor alteration in hepatic amino acid content seemed to be implicated in these actions. CONCLUSION: This study is the first to demonstrate that OKG regulates in vivo liver gene expression during acute malnutrition by modulating hepatic mRNA levels.