Publications by authors named "Corinne Pouyet"

18 Publications

  • Page 1 of 1

Anabolic Properties of Mixed Wheat-Legume Pasta Products in Old Rats: Impact on Whole-Body Protein Retention and Skeletal Muscle Protein Synthesis.

Nutrients 2020 May 29;12(6). Epub 2020 May 29.

UNH, Unité de Nutrition Humaine, CRNH, Université Clermont Auvergne, INRA, Auvergne, 63000 Clermont-Ferrand, France.

The mechanisms that are responsible for sarcopenia are numerous, but the altered muscle protein anabolic response to food intake that appears with advancing age plays an important role. Dietary protein quality needs to be optimized to counter this phenomenon. Blending different plant proteins is expected to compensate for the lower anabolic capacity of plant-based when compared to animal-based protein sources. The objective of this work was to evaluate the nutritional value of pasta products that were made from a mix of wheat semolina and faba bean, lentil, or split pea flour, and to assess their effect on protein metabolism as compared to dietary milk proteins in old rats. Forty-three old rats have consumed for six weeks isoproteic and isocaloric diets containing wheat pasta enriched with 62% to 79% legume protein (depending on the type) or milk proteins, i.e., casein or soluble milk proteins (SMP). The protein digestibility of casein and SMP was 5% to 14% higher than legume-enriched pasta. The net protein utilization and skeletal muscle protein synthesis rate were equivalent either in rats fed legume-enriched pasta diets or those fed casein diet, but lower than in rats fed SMP diet. After legume-enriched pasta intake, muscle mass, and protein accretion were in the same range as in the casein and SMP groups. Mixed wheat-legume pasta could be a nutritional strategy for enhancing the protein content and improving the protein quality, i.e., amino acid profile, of this staple food that is more adequate for maintaining muscle mass, especially for older individuals.
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http://dx.doi.org/10.3390/nu12061596DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7353003PMC
May 2020

Improving lipid mapping in Genome Scale Metabolic Networks using ontologies.

Metabolomics 2020 03 25;16(4):44. Epub 2020 Mar 25.

UMR1331, Toxalim (Research Centre in Food Toxicology), Université de Toulouse, INRAE, ENVT, INP-Purpan, UPS, 31300, Toulouse, France.

Introduction: To interpret metabolomic and lipidomic profiles, it is necessary to identify the metabolic reactions that connect the measured molecules. This can be achieved by putting them in the context of genome-scale metabolic network reconstructions. However, mapping experimentally measured molecules onto metabolic networks is challenging due to differences in identifiers and level of annotation between data and metabolic networks, especially for lipids.

Objectives: To help linking lipids from lipidomics datasets with lipids in metabolic networks, we developed a new matching method based on the ChEBI ontology. The implementation is freely available as a python library and in MetExplore webserver.

Methods: Our matching method is more flexible than an exact identifier-based correspondence since it allows establishing a link between molecules even if a different level of precision is provided in the dataset and in the metabolic network. For instance, it can associate a generic class of lipids present in the network with the molecular species detailed in the lipidomics dataset. This mapping is based on the computation of a distance between molecules in ChEBI ontology.

Results: We applied our method to a chemical library (968 lipids) and an experimental dataset (32 modulated lipids) and showed that using ontology-based mapping improves and facilitates the link with genome scale metabolic networks. Beyond network mapping, the results provide ways for improvements in terms of network curation and lipidomics data annotation.

Conclusion: This new method being generic, it can be applied to any metabolomics data and therefore improve our comprehension of metabolic modulations.
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http://dx.doi.org/10.1007/s11306-020-01663-5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7096385PMC
March 2020

Effect of high chronic intake of sucrose on liver metabolism in aging rats. Modulation by rutin and micronutrients.

J Physiol Biochem 2018 Nov 10;74(4):569-577. Epub 2018 Apr 10.

UNH, Unité de Nutrition Humaine, PFEM, MetaboHUB-Clermont, Université Clermont Auvergne, INRA, CRNH Auvergne, F-63000 Clermont-Ferrand, 63122, Theix, France.

High-sugar intake and senescence share common deleterious effects, in particular in liver, but combination of these two factors was little studied. Our aims were to examine the effect of a high-sucrose diet in liver of old rats and also the potential benefices of a polyphenol/micronutrient supplementation. Four groups of 22-month-old male rats fed during 5 months with a diet containing either 13 or 62% sucrose, supplemented or not with rutin, vitamin E, A, D, selenium, and zinc were compared. We measured liver macronutrient composition, glycation/oxidative stress, enzyme activities (lipogenesis, β-oxidation, fructokinase), gene expression (enzymes and transcription factors), in vivo protein synthesis rates and plasma parameters. Sucrose induced an increase in plasma and liver lipid content, and a stimulation of liver protein synthesis rates. Gene expression was little changed by sucrose, with lower levels for LXR-α and LXR-β. Polyphenol/micronutrient supplementation tended to limit liver triglyceride infiltration through variations in fatty acid synthase, acyl coA oxidase, and possibly ATP-citrate lyase activities. In conclusion, despite differences in enzymatic regulations, and blunted responses of gene expression, high-sucrose diet was still able to induce a marked increase in liver lipid content in old animals. However, it probably attenuated the positive impact of polyphenol/micronutrients.
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http://dx.doi.org/10.1007/s13105-018-0628-yDOI Listing
November 2018

Evaluation of oxidized phospholipids analysis by LC-MS/MS.

Anal Bioanal Chem 2018 Jan 28;410(2):633-647. Epub 2017 Nov 28.

Université Clermont Auvergne, INRA, UNH, Plateforme d'Exploration du Métabolisme, MetaboHUB Clermont, CRNH Auvergne, F-63000, Clermont-Ferrand, France.

Phospholipids (PLs) represent a class of metabolites of interest for evaluating the relationship between diet and the development of several metabolic diseases. Given that PLs are rich in unsaturated fatty acids, they can be oxidized. Because of their structure and reactivity, oxidized phospholipids (PLs-Ox) are increasingly recognized as markers of oxidative stress and of various diseases associated with inflammation. Therefore, there is a growing interest in studying PLs-Ox in lipidomics. Because of their limited commercial availability, very little information is currently available in databases to identify these molecules. The aim of this study is to acquire new knowledge about PLs-Ox in order to propose an analytical strategy for their analyses. For this purpose, a synthesis method of PLs-Ox, in auto-oxidation, has been developed and applied on phosphatidylcholine and phosphatidylethanolamine molecular species with various chain lengths, degree, and position of unsaturations. An analysis method based on mass (MS) and tandem mass spectrometry coupled to electrospray ionization was then developed and enabled the identification of a great diversity of long- and short-chain oxidation products. Formation kinetics of oxidation products was evaluated. Results showed that the formation of oxidized compounds was largely influenced by the degree of unsaturation on fatty acid chains. Oxidation time promotes the formation of some biologically important oxidation products. Coupling the MS method with liquid chromatography in flow injection analysis mode enabled the development of a full analytical strategy. Structural analysis of PLs-Ox allowed the enrichment of databases with important information to identify these molecules in biological matrices.
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http://dx.doi.org/10.1007/s00216-017-0764-1DOI Listing
January 2018

Supplementing Breakfast with a Vitamin D and Leucine-Enriched Whey Protein Medical Nutrition Drink Enhances Postprandial Muscle Protein Synthesis and Muscle Mass in Healthy Older Men.

J Nutr 2017 12 23;147(12):2262-2271. Epub 2017 Aug 23.

University of Clermont Auvergne, INRA, Human Nutrition Unit, Centre for Research in Human Nutrition Auvergne, Clermont-Ferrand, France;

A promising strategy to help older adults preserve or build muscle mass is to optimize muscle anabolism through providing an adequate amount of high-quality protein at each meal. This "proof of principle" study investigated the acute effect of supplementing breakfast with a vitamin D and leucine-enriched whey protein medical nutrition drink on postprandial muscle protein synthesis and longer-term effect on muscle mass in healthy older adults. A randomized, placebo-controlled, double-blind study was conducted in 24 healthy older men [mean ± SD: age 71 ± 4 y; body mass index (in kg/m) 24.7 ± 2.8] between September 2012 and October 2013 at the Unit of Human Nutrition, University of Auvergne, Clermont-Ferrand, France. Participants received a medical nutrition drink [test group; 21 g leucine-enriched whey protein, 9 g carbohydrates, 3 g fat, 800 IU cholecalciferol (vitamin D), and 628 kJ] or a noncaloric placebo (control group) before breakfast for 6 wk. Mixed muscle protein fractional synthesis rate (FSR) was measured at week 0 in the basal and postprandial state, after study product intake with a standardized breakfast with the use of l-[H]-phenylalanine tracer methodology. The longer-term effect of the medical nutrition drink was evaluated by measurement of appendicular lean mass, representing skeletal muscle mass at weeks 0 and 6, by dual-energy X-ray absorptiometry. Postprandial FSR (0-240 min) was higher in the test group than in the control group [estimate of difference (ED): 0.022%/h; 95% CI: 0.010%/h, 0.035%/h; ANCOVA, = 0.001]. The test group gained more appendicular lean mass than the control group after 6 wk (ED: 0.37 kg; 95% CI: 0.03, 0.72 kg; ANCOVA, = 0.035), predominantly as leg lean mass (ED: 0.30 kg; 95% CI: 0.03, 0.57 kg; ANCOVA, = 0.034). Supplementing breakfast with a vitamin D and leucine-enriched whey protein medical nutrition drink stimulated postprandial muscle protein synthesis and increased muscle mass after 6 wk of intervention in healthy older adults and may therefore be a way to support muscle preservation in older people. This trial was registered at www.trialregister.nl as NTR3471.
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http://dx.doi.org/10.3945/jn.117.252510DOI Listing
December 2017

Fast digestive, leucine-rich, soluble milk proteins improve muscle protein anabolism, and mitochondrial function in undernourished old rats.

Mol Nutr Food Res 2017 11 12;61(11). Epub 2017 Sep 12.

Université Clermont Auvergne, INRA, UNH, Unité de Nutrition Humaine, Clermont-Ferrand, France.

Scope: One strategy to manage malnutrition in older patients is to increase protein and energy intake. Here, we evaluate the influence of protein quality during refeeding on improvement in muscle protein and energy metabolism.

Methods And Results: Twenty-month-old male rats (n = 40) were fed 50% of their spontaneous intake for 12 weeks to induce malnutrition, then refed ad libitum with a standard diet enriched with casein or soluble milk proteins (22%) for 4 weeks. A 13C-valine was infused to measure muscle protein synthesis and expression of MuRF1, and MAFbx was measured to evaluate muscle proteolysis. mTOR pathway activation and mitochondrial function were assessed in muscle. Malnutrition was associated with a decrease in body weight, fat mass, and lean mass, particularly muscle mass. Malnutrition decreased muscle mTOR pathway activation and protein FSR associated with increased MuRF1 mRNA levels, and decreased mitochondrial function. The refeeding period partially restored fat mass and lean mass. Unlike the casein diet, the soluble milk protein diet improved muscle protein metabolism and mitochondrial function in old malnourished rats.

Conclusions: These results suggest that providing better-quality proteins during refeeding may improve efficacy of renutrition in malnourished older patients.
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http://dx.doi.org/10.1002/mnfr.201700287DOI Listing
November 2017

Vitamin D supplementation restores the blunted muscle protein synthesis response in deficient old rats through an impact on ectopic fat deposition.

J Nutr Biochem 2017 08 8;46:30-38. Epub 2017 Apr 8.

Université Clermont Auvergne, INRA, UNH, CRNH Auvergne, F-63000 Clermont-Ferrand, France. Electronic address:

We investigated the impact of vitamin D deficiency and repletion on muscle anabolism in old rats. Animals were fed a control (1 IU vitamin D/g, ctrl, n=20) or a vitamin D-depleted diet (VDD; 0 IU, n=30) for 6 months. A subset was thereafter sacrificed in the control (ctrl6) and depleted groups (VDD6). Remaining control animals were kept for 3 additional months on the same diet (ctrl9), while a part of VDD rats continued on a depleted diet (VDD9) and another part was supplemented with vitamin D (5 IU, VDS9). The ctr16 and VDD6 rats and the ctr19, VDD9 and VDS9 rats were 21 and 24 months old, respectively. Vitamin D status, body weight and composition, muscle strength, weight and lipid content were evaluated. Muscle protein synthesis rate (fractional synthesis rate; FSR) and the activation of controlling pathways were measured. VDD reduced plasma 25(OH)-vitamin D, reaching deficiency (<25 nM), while 25(OH)-vitamin D increased to 118 nM in the VDS group (P<.0001). VDD animals gained weight (P<.05) with no corresponding changes in lean mass or muscle strength. Weight gain was associated with an increase in fat mass (+63%, P<.05), intramyocellular lipids (+75%, P<.05) and a trend toward a decreased plantaris weight (-19%, P=.12). Muscle FSR decreased by 40% in the VDD group (P<.001), but was restored by vitamin D supplementation (+70%, P<.0001). Such changes were linked to an over-phosphorylation of eIF2α. In conclusion, vitamin D deficiency in old rats increases adiposity and leads to reduced muscle protein synthesis through activation of eIF2α. These disorders are restored by vitamin D supplementation.
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http://dx.doi.org/10.1016/j.jnutbio.2017.02.024DOI Listing
August 2017

N-3PUFA differentially modulate palmitate-induced lipotoxicity through alterations of its metabolism in C2C12 muscle cells.

Biochim Biophys Acta 2016 Jan 22;1861(1):12-20. Epub 2015 Oct 22.

Institut National de la Recherche Agronomique, UMR1019 Nutrition Humaine, Laboratoire de Nutrition Humaine, Université d'Auvergne, CRNH, 58 rue Montalembert BP321, 63009 Clermont Ferrand CEDEX 1, France. Electronic address:

Excessive energy intake leads to fat overload and the formation of lipotoxic compounds mainly derived from the saturated fatty acid palmitate (PAL), thus promoting insulin resistance (IR) in skeletal muscle. N-3 polyunsaturated fatty acids (n-3PUFA) may prevent lipotoxicity and IR. The purpose of this study was to examine the differential effects of n-3PUFA on fatty acid metabolism and insulin sensitivity in muscle cells. C2C12 myotubes were treated with 500 μM of PAL without or with 50 μM of alpha-linolenic acid (ALA), eicosapentaenoic acid (EPA) or docosahexaenoic acid (DHA) for 16 h. PAL decreased insulin-dependent AKT activation and glucose uptake and increased the synthesis of ceramides and diglycerides (DG) derivatives, leading to protein kinase Cθ activation. EPA and DHA, but not ALA, prevented PAL-decreased AKT activation but glucose uptake was restored to control values by all n-3PUFA vs. PAL. Total DG and ceramide contents were decreased by all n-3PUFA, but only EPA and DHA increased PAL β-oxidation, decreased PAL incorporation into DG and reduced protein kinase Cθ activation. EPA and DHA emerge as better candidates than ALA to improve fatty acid metabolism in skeletal muscle cells, notably via their ability to increase mitochondrial β-oxidation.
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http://dx.doi.org/10.1016/j.bbalip.2015.10.003DOI Listing
January 2016

DHA at nutritional doses restores insulin sensitivity in skeletal muscle by preventing lipotoxicity and inflammation.

J Nutr Biochem 2015 Sep 11;26(9):949-59. Epub 2015 May 11.

UMR 1019, Unité de Nutrition Humaine, INRA, Centre de Recherche en Nutrition Humaine (CRNH) Auvergne, Clermont Université, Université d'Auvergne, F-63000 Clermont-Ferrand, France.

Skeletal muscle plays a major role in the control of whole body glucose disposal in response to insulin stimulus. Excessive supply of fatty acids to this tissue triggers cellular and molecular disturbances leading to lipotoxicity, inflammation, mitochondrial dysfunctions, impaired insulin response and decreased glucose uptake. This study was conducted to analyze the preventive effect of docosahexaenoic acid (DHA), a long-chain polyunsaturated n-3 fatty acid, against insulin resistance, lipotoxicity and inflammation in skeletal muscle at doses compatible with nutritional supplementation. DHA (30 μM) prevented insulin resistance in C2C12 myotubes exposed to palmitate (500 μM) by decreasing protein kinase C (PKC)-θ activation and restoring cellular acylcarnitine profile, insulin-dependent AKT phosphorylation and glucose uptake. Furthermore, DHA protected C2C12 myotubes from palmitate- or lipopolysaccharide-induced increase in Ptgs2, interleukin 6 and tumor necrosis factor-α mRNA level, probably through the inhibition of p38 MAP kinase and c-Jun amino-terminal kinase. In LDLR -/- mice fed a high-cholesterol-high-sucrose diet, supplementation with DHA reaching up to 2% of daily energy intake enhanced the insulin-dependent AKT phosphorylation and reduced the PKC-θ activation in skeletal muscle. Therefore, DHA used at physiological doses participates in the regulation of muscle lipid and glucose metabolisms by preventing lipotoxicity and inflammation.
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http://dx.doi.org/10.1016/j.jnutbio.2015.04.003DOI Listing
September 2015

Bee pollen improves muscle protein and energy metabolism in malnourished old rats through interfering with the Mtor signaling pathway and mitochondrial activity.

Nutrients 2014 Dec 1;6(12):5500-16. Epub 2014 Dec 1.

INRA, UMR1019, Unité de Nutrition Humaine, CRNH Auvergne, Clermont-Ferrand F-63000, France.

Although the management of malnutrition is a priority in older people, this population shows a resistance to refeeding. Fresh bee pollen contains nutritional substances of interest for malnourished people. The aim was to evaluate the effect of fresh bee pollen supplementation on refeeding efficiency in old malnourished rats. Male 22-month-old Wistar rats were undernourished by reducing food intake for 12 weeks. The animals were then renourished for three weeks with the same diet supplemented with 0%, 5% or 10% of fresh monofloral bee pollen. Due to changes in both lean mass and fat mass, body weight decreased during malnutrition and increased after refeeding with no between-group differences (p < 0.0001). Rats refed with the fresh bee pollen-enriched diets showed a significant increase in muscle mass compared to restricted rats (p < 0.05). The malnutrition period reduced the muscle protein synthesis rate and mTOR/p70S6kinase/4eBP1 activation, and only the 10%-pollen diet was able to restore these parameters. Mitochondrial activity was depressed with food restriction and was only improved by refeeding with the fresh bee pollen-containing diets. In conclusion, refeeding diets that contain fresh monofloral bee pollen improve muscle mass and metabolism in old, undernourished rats.
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http://dx.doi.org/10.3390/nu6125500DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4276980PMC
December 2014

Increased body fat mass and tissue lipotoxicity associated with ovariectomy or high-fat diet differentially affects bone and skeletal muscle metabolism in rats.

Eur J Nutr 2015 Oct 5;54(7):1139-49. Epub 2014 Nov 5.

INRA, UMR 1019, UNH, CRNH Auvergne, 63000, Clermont-Ferrand, France.

Purpose: The aim of this study was to evaluate and compare the musculoskeletal effects induced by ovariectomy-related fat mass deposition against the musculoskeletal effects caused by a high-fat diet.

Methods: A group of adult female rats was ovariectomized and fed a control diet. Two additional groups were sham-operated and fed a control or a high-fat diet for 19 weeks. Distal femur and serum bone parameters were measured to assess bone metabolism. Muscle protein metabolism, mitochondrial markers and triglyceride content were evaluated in tibialis anterior. Triglyceride content was evaluated in liver. Circulating inflammatory and metabolic markers were determined.

Results: The high-fat diet and ovariectomy led to similar increases in fat mass (+36.6-56.7%; p < 0.05) but had different impacts on bone and muscle tissues and inflammatory markers. Consumption of the high-fat diet led to decreased bone formation (-38.4%; p < 0.05), impaired muscle mitochondrial metabolism, muscle lipotoxicity and a 20.9% increase in tibialis anterior protein synthesis rate (p < 0.05). Ovariectomy was associated with higher bone turnover as bone formation increased +72.7% (p < 0.05) and bone resorption increased +76.4% (p < 0.05), leading to bone loss, a 17.9% decrease in muscle protein synthesis rate (p < 0.05) and liver lipotoxicity.

Conclusions: In female rats, high-fat diet and ovariectomy triggered similar gains in fat mass but had different impacts on bone and muscle metabolism. The ovariectomy-induced mechanisms affecting the musculoskeletal system are mainly caused by estrogen depletion, which surpasses the potential-independent effect of adiposity.
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http://dx.doi.org/10.1007/s00394-014-0790-0DOI Listing
October 2015

Spreading intake of a leucine-rich fast protein in energy-restricted overweight rats does not improve protein mass.

Nutrition 2012 May 20;28(5):566-71. Epub 2011 Dec 20.

INRA, UMR 1019 Nutrition Humaine, Saint Genès Champanelle, France.

Objective: Energy restriction decreases fat mass and fat-free mass. Our aim was to prevent the latter using type and timing of protein nutrition as tools.

Methods: Young male Wistar rats were given a high-energy diet for 5 wk and then energy restricted and fed a high-protein diet containing caseins, milk-soluble proteins (MSP), or a casein-MSP mixture (n = 9 per group) as the only source of protein for 3 wk. Food intake was spread over 12 h, whereas in a previous experiment rats consumed their daily ration within 2 to 3 h. Weight and food intake were recorded. The body composition was measured by dual-energy x-ray absorptiometry before and after energy restriction. After 3 wk, the hind-limb muscles, the kidney, intestine, liver, and spleen weights, metabolic plasma parameters, and the liver and extensor digitorum longus muscle protein synthesis rates were measured in the postprandial state.

Results: The food intake was similar in all groups. Energy restriction induced a significant decrease in body weight and fat mass (P < 0.001) and stopped the slow growth of lean body mass, with no differences between groups. Among all tissues, a significant effect was detected only for the intestine (P = 0.0012), with a higher weight in the casein group. Postprandial liver and muscle protein synthesis rates were not different between groups.

Conclusion: When using a high-protein diet spread over 12 h, the nature of the protein intake has no influence on the sparing of lean body mass during energy restriction in young overweight rats.
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http://dx.doi.org/10.1016/j.nut.2011.08.020DOI Listing
May 2012

Increased availability of leucine with leucine-rich whey proteins improves postprandial muscle protein synthesis in aging rats.

Nutrition 2007 Apr 23;23(4):323-31. Epub 2007 Mar 23.

Unité de Nutrition Humaine, UMR 1019, Institut National de la Recherche Agronomique-Centre de Recherche en Nutrition Humaine d'Auvergne, Saint Genès Champanelle, France.

Objective: We previously found that aging was characterized by a decreased sensitivity of muscle protein synthesis to leucine and that a free leucine-supplemented diet corrected this defect in old rats and elderly humans. The present experiment was undertaken to evaluate the efficiency of selected leucine-rich proteins to stimulate postprandial muscle protein synthesis in old rats to optimize nutritional protein support in the elderly.

Methods: Sixty rats (22 mo old) received an experimental meal for the first hour of feeding and a standard diet for the rest of the day for 30 d. Experimental meals contained milk proteins that differed in leucine content: beta-lactoglobulin (14.5% leucine), Prolacta (13.4%), alpha-lactalbumin (10.9%), and casein (10%). As a control, a fifth group was added that received herring flour protein (7.3% leucine). Muscle protein synthesis was determined in vivo in the postprandial state at the end of the 30-d nutritional period using the flooding dose method (1-(13)C phenylalanine).

Results: Leucine intake and plasma leucine concentrations were significantly increased in rats fed meals containing the leucine-rich proteins (i.e., beta-lactoglobulin and Prolacta). As previously observed with free leucine-supplemented meals, postprandial muscle protein synthesis was significantly improved in rats fed the meals containing the leucine-rich proteins. Interestingly, the beneficial effect was maintained after the 30-d supplementation.

Conclusion: The results indicated that leucine-rich proteins were efficient in improving muscle protein synthesis in old rats. Thus, nutritional supplements containing such proteins may be efficient in preventing sarcopenia in the elderly and would represent a safe and optimized nutritional strategy. However, further experiments are necessary to determine the duration of such nutritional support to obtain a significant protein gain in muscle.
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http://dx.doi.org/10.1016/j.nut.2006.12.013DOI Listing
April 2007

Effect of an enteral diet supplemented with a specific blend of amino acid on plasma and muscle protein synthesis in ICU patients.

Clin Nutr 2007 Feb 25;26(1):30-40. Epub 2006 Sep 25.

RCO Département d'anesthésie-réanimation, CHU, 63000 Clermont-Ferrand, France.

Background & Aim: Polytrauma patients are characterized by a negative nitrogen balance and muscle wasting. Standard nutrition is relatively inefficient to improve muscle protein turnover. The aim of this study was to investigate the effect of enteral nutrition (EN) supplemented with specific amino acids on protein metabolism in polytrauma patients.

Methods: In a double blind study, 12 polytrauma patients were randomized to receive EN supplemented with either a mixture of cysteine, threonine, serine and aspartate (AA patients) or alanine at isonitrogenous levels (Ala patients). An intravenous infusion of l-[1-(13)C]-leucine was performed in the fed state between day 9 and 12 post-injury (Df) in patients and in a group of healthy volunteers (n=8) (EN+Ala) to measure whole body leucine kinetics, plasma and muscle protein synthesis rates. Nitrogen balance, 3-methyl histidine excretion were measured from day 3 to Df.

Results: The contribution of total plasma proteins to whole body protein synthesis was greatly increased, from 11% in healthy volunteers to about 25% in polytrauma patients. AA supplementation had no effect on nitrogen balance, leucine kinetics or plasma protein synthesis in patients. In contrast, the urinary excretion of 3-methyl histidine tended to decrease along the study in the AA supplemented group compared to an increase in the Ala group. Muscle protein synthesis tended to be higher in the AA group than in the Ala group (46%, P=0.065).

Conclusion: During injury, an increased supply of cysteine, threonine, serine and aspartate could be able to better cover the specific amino requirements, thus resulting in improved muscle protein synthesis without impairment of acute phase protein synthesis.
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http://dx.doi.org/10.1016/j.clnu.2006.07.007DOI Listing
February 2007

Beneficial effect of amino acid supplementation, especially cysteine, on body nitrogen economy in septic rats.

Clin Nutr 2006 Aug 4;25(4):634-42. Epub 2006 Jan 4.

Centre de Recherches Nestlé, Vers chez-les-blanc, P.O. Box 44 CH1000, Lausanne 26, Switzerland.

Background And Aims: Muscle wasting and increased synthesis of proteins and compounds involved in host defense characterize severe injury. The aims of the studies reported were to determine which amino acids exhibited an increased tissue content linked to anabolic processes in infected rats by comparison with healthy pair-fed controls, and to explore whether diets supplemented with these amino acids attenuate the catabolic response to infection.

Methods: Total amino acid content of the liver and the rest of the body were measured in control well-fed rats, in infected rats and their pair-fed controls 2 days after infection. In the nutritional protocols, infected rats were fed with a diet supplemented with alanine (basal diet), or threonine, serine, aspartate, asparagine and arginine (AA) or AA+cysteine (complete diet).

Results: Infection significantly increased liver total amino acid content by 38% for most amino acids. In contrast, the percentage increase was cysteine 79.3, threonine 45.3, aspartate-asparagine 46.3 and serine 46.5. Whole body without liver content of most amino acids decreased after infection due to the catabolic response, while the content of cysteine increased by 6% (P<0.05) and those of threonine and arginine did not decrease. After infection, animals fed the complete diet lost less weight than animals fed the basal diet (P<0.05). Furthermore, AA plus cysteine supplementation reduced significantly urinary nitrogen excretion and muscle wasting.

Conclusions: The results provide evidence that diet supplementation with cysteine, threonine, serine, aspartate-asparagine and arginine supports the synthesis of vital proteins to spare body protein catabolism during infection.
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http://dx.doi.org/10.1016/j.clnu.2005.11.009DOI Listing
August 2006

Leucine-supplemented meal feeding for ten days beneficially affects postprandial muscle protein synthesis in old rats.

J Nutr 2003 Apr;133(4):1198-205

Human Nutrition Research Centre of Clermont-Ferrand, Unité de Nutrition et Métabolisme Protéique, 63122 Ceyrat, France.

Acute leucine supplementation of the diet has been shown to blunt defects in postprandial muscle protein metabolism in old rats. This study was undertaken to determine whether the effect of leucine persists in a 10-d experiment. For this purpose, adult (9 mo) and old (21 mo) rats were fed a semiliquid 18.2 g/100 g protein standard diet during the 8-h dark period for 1 mo. Then, each group was given either a leucine-supplemented meal or an alanine-supplemented meal (as the control meal) for 1 h and the standard diet the rest of the feeding period. On d 10, rats were fed either no food (postabsorptive group) or the supplemented meal for 1 h. Muscle protein synthesis was assessed in vivo 90-120 min after meal distribution using the flooding dose method (1-(13)C phenylalanine). Leucinemia was similar in rats of both ages in the postabsorptive state. Postprandial plasma leucine concentrations were one- to twofold greater after the leucine meal than after the control meal. In the postabsorptive state, leucine supplementation did not modify the muscle protein synthesis rate in old rats but enhanced it to the postprandial rate in adult rats. As expected, muscle protein synthesis was stimulated by the control meal in adult rats but not in old rats. The leucine meal restored this stimulation in old rats but did not further stimulate muscle protein synthesis in adult rats. In conclusion, the beneficial effect of leucine supplementation on postprandial muscle protein anabolism persists for at least 10 d. The long-term utilization of leucine-rich diets may therefore limit muscle protein wasting during aging.
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http://dx.doi.org/10.1093/jn/133.4.1198DOI Listing
April 2003

Acute phase protein levels and thymus, spleen and plasma protein synthesis rates differ in adult and old rats.

J Nutr 2003 Jan;133(1):215-9

Unité de Nutrition et Métabolisme Protéique, Institut National de la Recherche Agronomique, Theix, 63 122 Saint-Genès-Champanelle, France.

Aging induces a dysregulation of immune and inflammation functions that may affect protein synthesis rates in lymphoid tissue and plasma proteins. We quantified in vivo synthesis rates of thymus, spleen and plasma proteins, including albumin and acute phase proteins, in adult (8 mo old) and old (22 mo old) rats using the flooding dose method [L-(1-(13)C) phenylalanine]. Immunosenescence was reflected by thymus atrophy and spleen hypertrophy in old rats but not in adult rats. A low albumin plasma level associated with high concentrations of fibrinogen, alpha(2)-macroglobulin, alpha(1)-acid glycoprotein and proteins other than albumin revealed a low grade inflammation in old rats. Protein fractional synthesis rates (FSR) and protein synthesis efficiencies of thymus were 29 and 26% lower in old than in adult rats, respectively; these variables did not differ in spleen. Protein absolute synthesis rates (ASR) of the thymus and spleen were 76% lower and 67% greater in old than adult rats, respectively. The FSR and ASR of albumin and other plasma proteins were greater in old than in adult rats. Protein synthesis measurement is a valuable nonimmunological tool to assess, in vivo, immune and inflammatory variables. Alterations in secondary lymphoid organs and plasma protein synthesis may contribute to the significant repartitioning of amino acids in old compared with adult rats and may be involved in sarcopenia.
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http://dx.doi.org/10.1093/jn/133.1.215DOI Listing
January 2003

Postprandial stimulation of muscle protein synthesis in old rats can be restored by a leucine-supplemented meal.

J Nutr 2002 Jan;132(1):95-100

Human Nutrition Research Centre of Clermont-Ferrand and Institut National de la Recherche Agronomique, Unité de Nutrition et Métabolisme Protéique, 63122 Ceyrat, France.

Aging is characterized by a progressive loss of muscle mass. A decrease of muscle protein synthesis stimulation has been detected in the postprandial state and correlated to a decrease of muscle protein synthesis sensitivity to leucine in vitro. This study was undertaken to examine the effect of a leucine-supplemented meal on postprandial (PP) muscle protein synthesis during aging. Adult (8 mo old) and old (22 mo old) rats were fed a semiliquid 18.2% protein control diet for 1 mo. The day of the experiment, rats received no food (postabsorptive group) or either an alanine or leucine-supplemented meal for 1 h (postprandial groups: PP and PP + Leu groups, respectively). Muscle protein synthesis was assessed in vivo 90-120 min after the meal distribution using the flooding dose method (1-(13)C phenylalanine). Plasma leucine concentrations were significantly greater in the PP + Leu group compared with the PP group at both ages. Muscle protein synthesis was significantly greater in the adult PP group, whereas it was not stimulated in the old PP group. When supplemented with leucine, muscle protein synthesis in old rats was stimulated and similar to that observed in adults. We conclude that acute meal supplementation with leucine is sufficient to restore postprandial stimulation of muscle protein synthesis in old rats. Whether chronic leucine meal supplementation may limit muscle protein wasting during aging remains to be verified.
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http://dx.doi.org/10.1093/jn/132.1.95DOI Listing
January 2002
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