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International audience; Food matrix interactions with polyphenols can affect their bioavailability and as a consequence may modulate their biological effects. The aim of this study was to determine if the matrix and its processing would modulate the bioavailability and the postprandial nutrigenomic response to a dietary inflammatory stress of apple flavan-3-ol monomers. We carried out an acute randomized controlled study in minipigs challenged with a high fat meal (HFM) supplemented with raw fruit, puree, or apple phenolic extract with matched content of flavan-3-ol monomers. Fasting and postprandial blood samples were collected over 3 h to quantify flavan-3-ol monomers in sera by UPLC-Q-TOF/MS and to isolate peripheral blood mononuclear cells (PBMCs) for assessing the changes in the gene expression profile using a microarray analysis. When compared to the extract-supplemented meal, the peak of the total flavan-3-ol concentration was reduced by half with both raw apple and puree supplements. The apple matrices also affected the gene expression profile as revealed by the Principal Component Analysis of the microarray data from PBMCs which discriminated the supplementation of HFM with the polyphenol extract from those with raw apples or puree. A total of 309 genes were identified as differentially expressed by the apple-derived products compared to HFM, with 63% modulated only in the presence of the food matrix (apple and puree). The number of differentially modulated genes was higher with the puree (246) than with the unprocessed apple (182). Pathway enrichment analyses revealed that genes affected by the apple-derived products control inflammation and leukocyte transendothelial migration both involved in the onset of atherosclerotic processes. Overall, this study showed that the two apple matrices reduce the postprandial serum concentration of flavon-3-ols whereas they increase the nutrigenomic response of PBMCs. The biological processes identified as modulated by the apple products suggest an attenuation of the transient proinflammatory response induced by a HFM. The differences observed between the nutrigenomic responses support that the apple matrix and its processing affect the nutrigenomic response, probably by increasing the bioavailability of other apple phytochemicals. To conclude, this study raises awareness for considering the impact of the food matrix and its processing on the biological response of polyphenols in nutritional studies.

International audience; Purpose We examined the impact of matrix food structure on post-prandial folate bioavailability (and other macronutrients) in human volunteers using a randomized, controlled, crossover experimental design. Methods Twelve healthy male volunteers (22.6 ± 0.4 years old) were offered four food models (differing in matrix structure: Custard, Pudding, Sponge cake and Biscuit) to which 1 mg of folic acid was added, according to a randomized, controlled, crossover experimental design. Plasma folates, glucose, insulin, alpha amino nitrogen and triglycerides were measured over the post-prandial period (from T0 to T480 min). Results Food matrix structure was capable of altering folate plasma availability. The highest folate availability was observed for pudding and to a lesser extent Sponge cake whereas the lowest was for the two matrices presenting extreme rheological properties: Custard (liquid) (P < 0.05 total AUC) and to a lesser extent Biscuit (hard solid) (P < 0.05, AUC 180 min). The analysis of plasma kinetics of appearance of other nutrients/metabolites helps to understand/explain the lower bioavailability of folates in Custard and Biscuit. Conclusion A least overall efficient bio-accessibility of all macronutrients and folic acid is observed in the gut lumen for Biscuit (delayed/incomplete destructuration of biscuit along the digestive tract). On the contrary, the lower folic acid absorption observed with custard does not fit with the rapid plasma appearance of other nutrients and should require further investigation.

International audience; Scope: The specific effect of the food matrix structure on fat-soluble micronutrient bioavailability is only partly understood. Evaluating fat-soluble micronutrient bioavailability after consumption of foods displaying similar composition but different structure is aimed at. Methods and results: Twelve healthy subjects are enrolled in a randomized, open label, crossover postprandial trial. Four different model foods are tested: custard, pudding, sponge cake, and biscuit. Vitamin D 3 , lutein, and triglyceride chylomicron responses, evaluated as postprandial areas under the curve, are then assayed. Custard triglyceride response is higher than pudding and biscuit responses (up to +122.7%, p < 0.0001). Sponge cake vitamin D 3 response is higher than biscuit response (+26.6%, p = 0.047). No difference between the model foods are observed regarding lutein responses. Triglyceride responses peak at 3 h for all conditions, while vitamin D 3 and lutein peaks are delayed by 1 h with the biscuit matrix compared to other model foods. Conclusion: Food structure can significantly impact on triglyceride and vitamin D 3 bioavailability in terms of absorbed amounts and/or maximum absorption time. The data highlight positive correlations between triglyceride, vitamin D, and lutein nutrient responses. These results are of particular interest to develop functional foods for population subgroups such as the elderly.

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International audience; Plant-based protein foods are increasingly common, but data on their nutritional protein quality are scarce. This study evaluated it for seitan (wheat-based food), tofu (soya-based food), soya milk, and a pea emulsion. The true ileal digestibility (TID) of their amino acids was determined in minipigs, to calculate the digestible indispensable amino acid score (DIAAS). The TID of the proteins was high and not significantly different between the foods tested: 97% for seitan, 95% for tofu, 92% for soya milk and 94% for pea emulsion. There were only minor differences in individual amino acid TIDs. DIAAS ranking was thus essentially driven by the amino acid composition of the food: soya-based food > pea emulsion > seitan. Nevertheless, the lower TID of sulphur-containing amino acids in tofu than in soya milk induced a significant decrease in DIAAS (from 117% to 97%), highlighting the importance of the matrix effect on nutritional protein quality.

Article; Proceedings Paper 6th International Conference on Food Digestion (INFOGEST) Location: Granada, SPAIN Date: APR 02-04, 2019; Intragastric pH greatly affects food disintegration and the release of nutrients in the gut. Here, the behaviour of two liquid meals (soymilk, pea emulsion) and two solid meals (tofu, seitan) was tested in miniature pigs fitted with gastric cannula. For 5 h, intragastric pH was recorded using one of three methods: ex vivo measurements of chyme samples, in situ measurements using pH catheters, or in situ measurements using wireless pH capsules, both inserted through a pig's cannula. The pH values obtained with the two in situ methods were highly correlated. The liquid and solid foods yielded distinct pH kinetics. For the solids, pH simply decreased exponentially. For the liquids, pH increased rapidly and then plateaued for 2 h before dropping Food macrostructure and, to a lesser extent, food buffering capacity clearly had an impact on intragastric pH. We modelled changes in intragastric pH over time with food-dependent nonlinear equations.

Food matrix is known to interact with some dietary constituents and microconstituents during digestion. These interactions may potentially affect the metabolism and bioavailability of some compounds, and as a consequence modulate their biological effects. In this context, the aim of this study was to determine the effect of apple food matrix on the bioavailability of flavan-3-ols and on the ability of these compounds to modulate the nutrigenomic response to a high fat challenge in minipigs.Adult male Yucatan minipigs (n = 5) were assigned to a random treatment sequence of high-fat meals non supplemented or supplemented with 250 g of raw apple, 250 g of apple puree or 1.4 g of apple polyphenols extract, with a 7-days washout period between each treatment. Each supplementation provided 155 mg flavan-3-ol monomers. At each treatment period, fasting- and 1h-, 2h-, 3h-postprandial blood samples were collected, and the concentration in flavan-3-ol monomers was measured on hydrolyzed serum, using UPLC-Q-TOF MS. The ability of apple-derived products to modulate the postprandial gene expression profile was assessed and compared in circulating PBMCs collected at 3 h after consumption of the four tested meals using a microarray analysis.Results show that the apple matrix did not affect the kinetic of the postprandial absorption of flavan-3-ol monomers. The total flavan-3-ols concentrations measured at peak were significantly higher in the extract (x1.75), suggesting an impact of the apple matrix on flavan-3-ols absorption. However, no significant difference in total flavanols was observed between raw apple and apple puree.Principal Component Analysis of the microarray data from PBMCs identified three distinct clusters of gene expression patterns: one corresponding to gene expression profiles after the high-fat meal, one for meal supplemented with raw apples or apple puree, and a third cluster for meal supplemented with polyphenol extract. A set of 309 genes was identified as differentially expressed by apple-derived products compared to high-fat meal alone, including 93 modulated with the three apple products. The variations in gene expression were similar for only 75% of the 93 genes, suggesting that the apple matrix affects the nutrigenomic response to flavan-3-ols. A bioinformatics analysis revealed that genes affected by apple-derived products are involved in inflammation and leukocyte transendothelial migration, suggesting a beneficial impact of apple-derived products.In conclusion, these results raise awareness for considering the impact of food matrix on the biological responsiveness of polyphenols in future nutritional studies.

International audience; We studied the kinetics of peptide release during the gastric digestion of meat proteins in vivo, in view to predicting the release of bioactive peptides further on in the digestive tract. Six mini pigs fitted with gastric cannulas received a meal with cooked beef as protein source. Digesta was collected at regular time intervals up to 5½ h. The peptides generated by the gastric digestion of meat were identified and quantified using label-free LC MS, thereafter subjected to in silico digestion mimicking the action of intestinal enzymes. Three clusters of proteins presenting similar evolutions according to their dynamic hydrolysis were obtained. This study clearly improves the in silico prediction of the intestinal release of bioactive peptides by mapping meat protein degradation in the stomach in an in vivo model. Knowledge of the conformation of the peptides released in the stomach further improves this prediction.

International audience; Fruit and vegetables (F&V) polyphenols have numerous positive health effects, ascribed either to their antioxidant activity within the gastrointestinal tract (GIT) or to bioactivity of their absorbed metabolites. The effect of the F&V matrix on the gastrointestinal bioaccessibility of polyphenols was investigated along with its possible interaction with protein digestion. Minipigs were fed a complete meal with either cubed F&V (apple, plum, artichoke) added, or the corresponding phenolic extract (PE). Gastric and ileal chymes were kinetically collected over the postprandial period. The overall polyphenol bioaccessibility in the stomach was found to be 1.5% and 3.1% after F&V and PE consumption, respectively. The lower release rate from artichoke than from apple showed evidence of a plant effect. Flavanol monomers and glucoside conjugates were not recovered in the ileum in agreement with their absorption in the upper GIT. Interestingly, PE, but not F&V, significantly decreased the speed and efficiency of dietary protein digestion.

This work was supported by an INRA Priority Action of the "Alimentation Humaine" department (2013-2015). Marielle Margier received a doctoral fellowship (2015-2018) from Region PACA in partnership with the Centre Technique de Conservation des Produits Alimentaires (CTCPA, Avignon); Scope: Food matrix is generally believed to alter carotenoid bioavailability, but its effect on xanthophylls is usually limited. This study thus aims to decipher the digestion-absorption process of lutein in the presence or not of a food matrix.Methods: Lutein transfer to gastric-like lipid droplets or artificial mixed micelles was assessed when lutein was added to test meals either as a pure molecule ((all-E)-lutein) or in canned spinach ((Z) + (all-E)-lutein). The obtained mixed micelles were delivered to Caco-2 cells to evaluate lutein uptake. Finally postprandial plasma lutein responses were compared in minipigs after the two test meals.Results: Lutein transfer to gastric-like lipid droplets and to mixed micelles was higher when lutein was added in spinach than when it was added as pure lutein (+614% and +147%, respectively, p < 0.05). Conversely, lutein uptake was less effective when micellar lutein was from a meal containing spinach than from a meal containing its pure form (-55%, p < 0.05). In minipigs, postprandial lutein response was delayed with spinach but not significantly different after the two test meals.Conclusion: Opposite effects at the micellarization and intestinal cell uptake steps explain the lack of effect of spinach matrix on lutein bioavailability.

Ageing impairs the muscle anabolic effect of food intake, which may explain muscle loss and an increased risk of sarcopenia. Ageing is also associated with low grade inflammation (LGI), which has been negatively correlated with muscle mass and strength. In rodents, the muscle anabolic resistance observed during ageing and sarcopenia has been ascribed to the development of the LGI. We aimed to investigate this relationship in humans. We studied protein metabolism and physical fitness in healthy elderly volunteers with slight chronic C-reactive protein. Two groups of healthy elderly volunteers were selected on the presence (or not) of a chronic, slight, elevation of CRP (Control: 2 mg l(-1) and

Lutein is a xanthophyll involved in the prevention of age-related macular degeneration. Its health effects obviously depend on its bioavailability, which can be modulated by the food matrix. Indeed, the matrix can either hold back its embedded micronutrients, or protect them from a possible degradation in the upper gastrointestinal tract. Thus, the purpose of this study was to determine the impact of the matrix of canned spinach on lutein bioavailability.In vitro digestions were first used to compare lutein bioaccessibility (percentage level of lutein released from the matrix to mixed micelles) when lutein was added to the test meal either as a pure molecule or in canned spinach. Then, mixed micelles isolated from these in vitro digestions were delivered to human intestinal Caco-2 TC7 cells to assess lutein uptake and efflux. To strengthen these results, an experiment was performed in piglets to verify in vivo the impact of the canned spinach matrix on lutein bioavailability, which was evaluated by comparison of the postprandial plasma lutein responses (0-12 h area under the curve of the plasma lutein concentrations) after test meals that contained either pure lutein or lutein in canned spinach.Our results showed that lutein bioaccessibility was significantly higher when lutein was digested in spinach as compared to in vitro digestion of the pure form (+35%, p

International audience; Background: Meat cooking conditions in in vitro and in vivo models have been shown to influence the rate of protein digestion, which is known to affect postprandial protein metabolism in the elderly.Objective: The present study was conducted to demonstrate the effect of cooking conditions on meat protein assimilation in the elderly. We used a single-meal protocol to assess the meat protein absorption rate and estimate postprandial meat protein utilization in elderly subjects.Design: The study recruited 10 elderly volunteers aged 70–82 y. Each received, on 2 separate occasions, a test meal exclusively composed of intrinsically 15N-labeled bovine meat (30 g protein), cooked at 55°C for 5 min [rare meat (RM)] or at 90°C for 30 min [fully cooked meat (FCM)], and minced. Whole-body fluxes of leucine, before and after the meal, were determined with the use of a [1-13C]leucine intravenous infusion. Meat protein absorption was recorded with the use of 15N enrichment of amino acids.Results: Postprandial time course observations showed a lower concentration in the plasma of indispensable amino acids (P < 0.01), a lower entry rate of meat leucine in the plasma (P < 0.01), and a lower contribution of meat nitrogen to plasma amino acid nitrogen (P < 0.001), evidencing lower peripheral bioavailability of meat amino acids with RM than with FCM. This was associated with decreased postprandial whole-body protein synthesis with RM than with FCM (40% compared with 56% of leucine intake, respectively; P < 0.01).Conclusions: Whereas meat cooking conditions have little effect on postprandial protein utilization in young adults, the present work showed that the bioavailability and assimilation of meat amino acids in the elderly is lower when meat is poorly cooked. In view to preventing sarcopenia, elderly subjects should be advised to favor the consumption of well-cooked meat. This trial was registered at clinicaltrials.gov as NCT02157805.

The authors are very grateful to the physician and nurses of the Human Nutrition Research Centre of Auvergne and to Patrice Reiling for their technical assistance; International audience; Lycopene (LYC) bioavailability is relatively low and highly variable, because of the influence of several factors. Recent in vitro data have suggested that dietary Ca can impair LYC micellarisation, but there is no evidence whether this can lead to decreased LYC absorption efficiency in humans. Our objective was to assess whether a nutritional dose of Ca impairs dietary LYC bioavailability and to study the mechanism(s) involved. First, in a randomised, two-way cross-over study, ten healthy adults consumed either a test meal that provided 19-mg (all-E)-LYC from tomato paste or the same meal plus 500-mg calcium carbonate as a supplement. Plasma LYC concentration was measured at regular time intervals over 7 h postprandially. In a second approach, an in vitro digestion model was used to assess the effect of increasing Ca doses on LYC micellarisation and on the size and zeta potential of the mixed micelles produced during digestion of a complex food matrix. LYC bioavailability was diminished by 83 % following the addition of Ca in the test meal. In vitro, Ca affected neither LYC micellarisation nor mixed micelle size but it decreased the absolute value of their charge by 39 %. In conclusion, a nutritional dose of Ca can impair dietary LYC bioavailability in healthy humans. This inhibition could be due to the fact that Ca diminishes the electrical charge of micelles. These results call for a thorough assessment of the effects of Ca, or other divalent minerals, on the bioavailability of other carotenoids and lipophilic micronutrients.

The free radical theory of aging proposes that oxidative stress plays a key role in the aging process. By altering muscle protein degradation rates, it could accelerate the age-related loss of muscle proteins. Glutathione (GSH), one of the main body antioxidants, could prevent this phenomenon, but its concentration decreases during aging. Our aims were to have a better understanding of the mechanisms of the age-related decrease in glutathione availability and of the links with sarcopenia. Male Wistar rats aged 6, 9, 12, 15, 19, 22, 25 and 28 months (n = 6 per age) were used to measure plasma and skeletal muscle protein carbonyl content, plasma total and free cyst(e)ine content, liver and muscle glutathione content as well as liver GSSG reductase, GSH peroxidase, GSH transferase and gamma glutamyl cysteine synthetase (GCS) activities. Although tissue glutathione content decreased with age, the other markers of oxidative stress were little changed during aging. In particular, muscle protein carbonyl content was unchanged. Variations in glutathione availability were not explained by cyst(e)ine availability but depended on gamma GCS activity. The stability of skeletal muscle carbonyl content during aging suggests a very efficient degradation of oxidized proteins in muscle.

Inflammatory bowel diseases (IBDs) are associated with an increased whole-body protein turnover. In certain drug-induced experimental models of IBD, disturbances of protein synthesis in tissues have been reported recently, but it is unclear if similar disturbances occur in other chronic intestinal diseases. Therefore we investigated changes in protein synthesis in different tissues of HLA-B27 (human leucocyte antigen B27) transgenic rats that develop spontaneously chronic inflammation, with major involvement of the colon. Protein synthesis rate in HLA-B27 rats was shown to be higher in nine different tissues compared with control (Fisher 344) rats. The absolute rate of protein synthesis was highly stimulated at the main inflammatory site (+290% in the colon). However, liver, muscle and skin appeared to be major contributors to the increased protein synthesis observed at the whole-body level. Despite the increased protein synthesis, HLA-B27 rats presented a marked atrophy of muscles, which suggests an increased proteolysis. These results contrast with metabolic disturbances described in acute inflammation and colitis induced by drugs (i.e. dextran sodium sulphate). The present study suggests that the modifications of protein metabolism are strongly influenced by the type of the inflammatory diseases and thus by the underlying mechanisms, which result in different metabolic adaptations and specific nutritional requirements.

International audience; Previous studies indicate that the ingestion of oxidized vegetable oils leads to the incorporation of chemically reastive molecules issed from the decomposition of the initial lipid hydroperoxides into lipoproteins. The aim of the present study is to investigate the oxidation of dietary lipids in the gastric compartment and their inhibition by plant polyphenols provided either as fruit and vegetables (F&V) or an extract. Six minipigs received a standard Western diet containing primarily sunflower oil, ground beef meat, and starch. Polyphenols in different matrix forms were ingested either as cubed F&L or as the corresponding hydroacetonic extract. Sampling of the gastric digesta allowed the kinetic investigation of pH, heme and non-heme iron forms, total lipids, lipid-derived conjugated dienes (CD) and TBARS. F&V and the corresponding polyphenol extract delayed the gastric digestion process as shown for total lipid and heme iron contents. This study also demonstrated the occurence of in vivo oxidation of dietary lipids in the presence of meat iron. Interestingly, F&V played a protective role by totally inhibiting the accumulation of CD while largely decreasing the formation of TBARS. The polyphenol extract similarly slowed down the TBARS formation although it had no effect on the CD accumulation.

This study aimed at determining the kinetics of milk protein digestion and amino acid absorption after ingestion by six multi-canulated mini-pigs of two gelled dairy matrices having the same composition, similar rheological and structural properties, but differing by their mode of coagulation (acidification/renneting). Duodenal, mid-jejunal effluents and plasma samples were collected at different times during 7 h after meal ingestion. Ingestion of the acid gel induced a peak of caseins and β-lactoglobulin in duodenal effluents after 20 min of digestion and a peak of amino acids in the plasma after 60 min. The rennet gel induced lower levels of both proteins in the duodenum (with no defined peak) as well as much lower levels of amino acids in the plasma than the acid gel. Plasma ghrelin concentrations suggested a potentially more satiating effect of the rennet gel compared to the acid gel. This study clearly evidences that the gelation process can significantly impact on the nutritive value of dairy products.

This study aimed to determine the kinetics of milk protein digestion and amino acid absorption after ingestion of four dairy matrices by six minipigs: unheated or heated skim milk and corresponding rennet gels. Digestive contents and plasma samples were collected over a 7 h-period after meal ingestion. Gelation of milk slowed down the outflow of the meal from the stomach and the subsequent absorption of amino acids, and decreased their bioavailability in peripheral blood. The gelled rennet matrices also led to low levels of milk proteins at the duodenum. Caseins and b-lactoglobulin, respectively, were sensitive and resistant to hydrolysis in the stomach with the unheated matrices, but showed similar digestion with the heated matrices, with a heat-induced susceptibility to hydrolysis for b-lactoglobulin. These results suggest a significant influence of the meal microstructure (resulting from heat treatment) and macrostructure (resulting from gelation process) on the different steps of milk proteins digestion.

International audience; The speed of protein digestion impacts on postprandial protein anabolism. After exercise or in the elderly, fast proteins stimulate protein synthesis more efficiently than slow proteins. It has been shown that meat might be a source of fast proteins. However, cooking temperature, acting on the macrostructure and microstructure of the meat could affect both the speed, and efficiency, of protein digestion. This study aims to evaluate, in vivo, the effect of meat cooking on digestion parameters, in the context of a complete meal. Six minipigs fitted with an ileal cannula and an arterial catheter were used. In order to measure the true ileal digestibility, tested meat was obtained from a calf, the muscle proteins of which were intrinsically labelled with 15 N-amino acids. Three cooking temperatures (60, 75 and 95uC; core temperature for 30 min), and three levels of intake (1, 1.45, and 1.90 g protein/kg body weight) were tested. Following meat ingestion, ileal digesta and arterial blood were collected over a 9-h period. The speed of digestion, evaluated from the kinetics of amino acid appearance in blood within the first 3 h, was greater for the cooking temperature of 75uC, than for 60 or 95uC. The true ileal digestibility, which averaged 95%, was not affected by cooking temperature or by the level of meat intake. The amino acid composition of the digesta flowing at the ileum was not affected by cooking temperature. These results show that cooking temperature can modulate the speed of meat protein digestion, without affecting the efficiency of the small intestinal digestion, and consequently the entry of meat protein residues into the colon.

The high requirement of the gut for threonine has often been ascribed to the synthesis of mucins, secreted threonine-rich glycoproteins protecting the intestinal epithelium from injury. This requirement could be even greater during intestinal inflammation, when mucin synthesis is enhanced. In this study, we used an animal model to investigate the effects of an acute ileitis on threonine splanchnic fluxes. Eight adult multi-catheterized minipigs were fed with an enteral solution. Four of them were subjected to experimental ileitis involving direct administration of trinitrobenzene sulfonic acid (TNBS) into the ileum (TNBS-treated group) and the other 4 were not treated (control group). Threonine fluxes across the portal-drained viscera (PDV) were quantified with the use of simultaneous i.g. L-[(15)N]threonine and i.v. L-[U-(13)C]threonine infusions. Ileal mucosa was sampled for mucin fractional synthesis rate measurement, which was greater in the TNBS-treated group (114 +/- 15%/d) than in the control group (61 +/- 8%/d) (P = 0.021). The first-pass extraction of dietary threonine by the PDV and liver did not differ between groups and accounted for approximately 27 and 10% of the intragastric delivery, respectively. PDV uptake of arterial threonine increased from 25 +/- 14 micromol x kg(-1) x h(-1) in the control group to 171 +/- 35 micromol x kg(-1) x h(-1) in the TNBS-treated group (P < 0.001). In conclusion, ileitis increased intestinal mucin synthesis and PDV utilization of threonine from arterial but not luminal supply. This leads to the mobilization of endogenous proteins to meet the increased threonine demand associated with acute intestinal inflammation.

Publication Inra prise en compte dans l'analyse bibliométrique des publications scientifiques mondiales sur les Fruits, les Légumes et la Pomme de terre. Période 2000-2012. http://prodinra.inra.fr/record/256699; International audience; The aim of the present study was to determine whether the addition of soluble fibre in the diet affected protein metabolism in the intestinal tissues, some visceral organs and in skeletal muscle. A diet supplemented with pectin (80 g/kg) was fed to young growing rats and the effect on organ mass and protein metabolism in liver, spleen, small and large intestines and gastrocnemius muscle was monitored and compared with the control group. Protein synthesis rates were determined by measuring [13C]valine incorporation in tissue protein. In the pectin-fed rats compared with the controls, DM intake and body weight gain were reduced (9 and 20 %, respectively) as well as gastrocnemius muscle, liver and spleen weights (6, 14 and 11 %, respectively), but the intestinal tissues were increased (64 %). In the intestinal tissues all protein metabolism parameters (protein and RNA content, protein synthesis rate and translational efficiency) were increased in the pectin group. In liver the translational efficiency was also increased, whereas its protein and RNA contents were reduced in the pectin group. In gastrocnemius muscle, protein content, fractional and absolute protein synthesis rates and translational efficiency were lower in the pectin group. The stimulation of protein turnover in intestines and liver by soluble fibre such as pectins could be one of the factors that explain the decrease in muscle turnover and whole-body growth rate.

Characterisation and identification of peptides (800 to 5000 Da) generated by intestinal digestion of fish or meat were performed using MS analyses (matrix-assisted laser desorption ionisation time of flight and nano-liquid chromatography electrospray-ionisation ion trap MS/MS). Four pigs fitted with cannulas at the duodenum and jejunum received a meal exclusively made of cookedPectoralis profundusbeef meat or cooked trout fillets. A protein-free meal, made of free amino acids, starch and fat, was used to identify peptides of endogenous origin. Peptides reproducibly detected in digesta (i.e. from at least three pigs) were evidenced predominantly in the first 3 h after the meal. In the duodenum, most of the fish- and meat-derived peptides were characteristic of a peptic digestion. In the jejunum, the majority of peptides appeared to result from digestion by chymotrypsin and trypsin. Despite slight differences in gastric emptying kinetics and overall peptide production, possibly in relation to food structure and texture, six and four similar peptides were released after ingestion of fish or meat in the duodenum and jejunum. A total of twenty-six different peptides were identified in digesta. All were fragments of major structural (actin, myosin) or sarcoplasmic (creatine kinase, glyceraldehyde-3-phosphate dehydrogenase and myoglobin) muscle proteins. Peptides were short (

International audience; BACKGROUND: The rate of protein digestion affects protein utilization in elderly subjects. Although meat is a widely consumed protein source, little is known of its digestion rate and how it can be affected by the chewing capacity of elderly subjects. OBJECTIVES: We used a [1-(13)C]leucine balance with a single-meal protocol to assess the absorption rate of meat protein and to estimate the utilization of meat protein in elderly subjects with different chewing efficiency. DESIGN: Twenty elderly volunteers aged 60-75 y were involved in the study. Ten of them had healthy natural dentition, and the other 10 were edentulous and wore complete dentures. Whole-body fluxes of leucine, before and after the meal (120 g beef meat), were measured with the use of a [1-(13)C]leucine intravenous infusion. RESULTS: A rapid increase in plasma aminoacidemia and plasma leucine entry rate was observed after meat intake in dentate subjects. In complete denture wearers the increase in leucine entry rate was delayed (P

International audience; BACKGROUND: Inflammation is known to affect sulfur amino acid metabolism. Aging is associated with an increased prevalence of inflammatory conditions, but the metabolism of methionine has been poorly explored in the elderly. OBJECTIVES: The aims of this study were to compare methionine kinetics between elderly and young subjects and to explore the effect of aging on the response to a mild inflammatory challenge induced by a vaccination. DESIGN: Seven elderly volunteers aged 66-76 y and 8 young volunteers aged 22-26 y were studied before and 2 d after a vaccination (diphtheria, tetanus, poliomyelitis, and typhoid vaccines). Methionine kinetics were measured by using an infusion of L-[1-13C, methyl-2H3]methionine in the postabsorptive and fed states. RESULTS: Before vaccination, the contribution of homocysteine remethylation to methionine-methyl flux (Qm) and the ratio of remethylation to homocysteine transsulfuration were significantly lower in the elderly subjects than in the young subjects (P < 0.05). In contrast, the contribution of transsulfuration to methionine transmethylation was higher in the elderly (P < 0.05). Vaccination significantly increased the ratio of transsulfuration to transmethylation and decreased the ratio of remethylation to Qm (P < 0.05). CONCLUSIONS: The preferential methionine metabolism toward cysteine synthesis observed after vaccination suggests an increased requirement of sulfur amino acids even in mild inflammatory situations. The main finding of this study is a higher proportion of methionine entering the transsulfuration pathway in elderly subjects before vaccination. This finding suggests an increased cysteine demand during aging.

Article original; International audience; 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

Mitochondrial free radical (ROS) production could be involved in sarcopenia. Our aim was to measure this production in various muscles during aging. Male Wistar rats aged 4.5 and 24 months were used. H(2)O(2) release and protein carbonyls were evaluated in isolated mitochondria from an oxidative (soleus) and a glycolytic (tibialis anterior) muscle. Total and Mn-superoxide dismutase (SOD), catalase, glutathione peroxidase (GPX) and glutathione reductase (GR) activities were measured in tibialis anterior. In soleus, glutamate/malate supported mitochondrial H(2)O(2) release was lower than in tibialis anterior in young rats, but increased significantly with age. In tibialis anterior, glutamate/malate or succinate supported H(2)O(2) release was unchanged with age. ROS generators were complexes I and III. Mitochondrial carbonyl content remained stable during aging in both muscles but tended to be higher in tibialis anterior than in soleus. Tibialis anterior total SOD (+17%), catalase (+84%), and GPX (-17%) activities varied significantly with age but Mn-SOD was unchanged, suggesting an increase in cytosolic ROS production. In conclusion, the higher life-long H(2)O(2) release observed in tibialis anterior is consistent with the known sensitivity of glycolytic muscles to sarcopenia. The fact that the rate of H(2)O(2) release increases with age in soleus seems to have little impact.

The mechanisms leading to hypoalbuminemia in sepsis were explored by measuring plasma volume, albumin distribution, plasma albumin transcapillary escape rate (TER), and efflux (TER × albumin intravascular pool). These parameters were quantified in infected rats, injected intravenously with live Escherichia coli, and pair-fed and well-fed rats using an injection of35S-albumin and measuring plasma and whole body albumin concentrations. Animals were studied on days 1, 6, and 10 after infection. In pair-fed rats, neither albumin distribution nor exchange rate between the intra- and extravascular compartments was modified. The increase of plasma volume after infection partly explained hypoalbuminemia. Infection resulted in a reduction of the total albumin pool of the body all along the experimental period, indicating a net loss of the protein. Albumin TER (%/day) was significantly increased 1 and 6 days after infection, but the absolute efflux was increased only on day 1. Normal values were observed on day 10. Therefore, an accelerated plasma efflux contributes to hypoalbuminemia only during the early period of sepsis. During this phase, the protein was retained in the extravascular space where it was probably catabolized. Later on, other factors are probably involved.

International audience; 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.

Methionine transsulfuration in plasma and liver, and plasma methionine and cysteine kinetics were investigated in vivo during the acute phase of sepsis in rats. Rats were infected with an intravenous injection of live Escherichia coli, and control pair-fed rats were injected with saline. Two days after injection, the rats were infused for 6 h with [35S]methionine and [15N]cysteine. Transsulfuration was measured from the transfer rate of 35S from methionine to cysteine. Liver cystathionase activity was also measured. Infection significantly increased ( P < 0.05) the contribution of transsulfuration to cysteine flux in both plasma and liver (by 80%) and the contribution of transsulfuration to plasma methionine flux (by 133%). Transsulfuration measured in plasma was significantly ( P < 0.05) higher in infected rats than in pair-fed rats (0.68 and 0.25 μmol · h−1 · 100 g−1, respectively). However, liver cystathionase specific activity was decreased by 17% by infection ( P < 0.05). Infection increased methionine flux (16%, P < 0.05) less than cysteine flux (38%, P < 0.05). Therefore, the plasma cysteine flux was higher than that predicted from estimates of protein turnover based on methionine data, probably because of enhanced glutathione turnover. Taken together, these results suggest an increased cysteine requirement in infection.

We investigated the ability of pentoxifylline (PTX) to modulate protein synthesis and degradation in the presence and absence of insulin during incubation of epitrochlearis muscle, 2 or 6 days after injection of Escherichia coli. On days 2 and 6 after infection, protein synthesis was inhibited by 25%, whereas proteolysis was enhanced by 75%. Insulin (2 nM) in vitro stimulated protein synthesis in muscles from infected rats to the same extent as in controls. The ability of insulin to limit protein degradation was severely blunted 48 h after infection. On day 6 after infection, insulin inhibited proteolysis to a greater extent than on day 2. PTX suppressed the increase in plasma concentrations of tumor necrosis factor more than 600-fold after injection of bacteria, and partially prevented the inhibition of protein synthesis and stimulation of protein degradation during sepsis. Moreover, PTX administration maintained the responsiveness of protein degradation to insulin during sepsis. Thus cytokines may influence skeletal muscle protein metabolism during sepsis, both indirectly through inhibition of the effects of insulin on proteolysis, and directly on the protein synthesis and degradation machinery.

Skeletal muscle catabolism is a characteristic metabolic response to sepsis. We investigated the ability of physiological insulin (2 nM) or insulin-like growth factor I (IGF-I, 10 nM) concentrations to modify protein metabolism during incubation of epitrochlearis 2, 6, or 15 days after injection of live Escherichia coli. On days 2 and 6 postinfection, skeletal muscle exhibited an exacerbated negative protein balance resulting from both an inhibition in protein synthesis (25%) and an enhanced proteolysis (90%) compared with controls. By day 15 postinfection, protein balance in infected rats was significantly improved compared with either day 2 or 6. At this time, protein synthesis was augmented and protein degradation was decreased in infected rats relative to day 6. Insulin or IGF-I stimulated protein synthesis in muscles from septic and control rats in vitro to the same extent at each time point examined. The ability of insulin or IGF-I to limit protein degradation was severely blunted 48 h after infection. On day 6 postinfection, the effect of insulin or IGF-I to inhibit proteolysis was more pronounced than on day 2. Incubation with IGF-I limited proteolysis to a greater extent than insulin on both days in infected but not control rats. By day 15, insulin diminished proteolysis to the same extent as in controls. The results suggest that injection of bacteria causes fundamental derangements in protein metabolism that persist for days after infection.