Reducing meat consumption is encouraged to improve diet environmental sustainability. It results in reducing protein intake, and this can have consequences on eating behaviour. To better characterise these consequences, six-week-old male Wistar rats were divided into 5 groups receiving diets differing by their protein source and amount. Two groups received a casein (C) diet, containing 20% (C20) or 6% (C6) protein, a casein density known to induce a hyperphagic response in rats. Three groups received a dehydrated bovine protein (DBP) diet, containing 6% (B6), 10% (B10), or 20% (B20) protein. C20 and B20 rats had also free access to 40% protein pellets (casein for C20 and DBP for B20), but choose to maintain their protein intake close to 20%. C20 and B20 rats showed similar growth and food consumption throughout the 12-week experiment. B6 rats showed reduced growth (-26%) and lean body mass despite similar food consumption to B20. C6 and B10 rats increased their food intake (C6 by +20% relative to C20; B10 by +30% relative to B20) and showed similar growth to C20 and B20 rats. Comparison of amino acid intakes suggests that the amplitude of food overconsumption allowed C6 and B10 rats to achieve a threshold intake of specific essential amino acids. C6 and B10 rats had more visceral adiposity than C20 and B20 rats, but similar lean body mass. Our results characterize the hyperphagic response to moderate meat protein reduction, showing that it increases adiposity, then providing some insights into the obesogenic risk potentially associated with reduced meat consumption.

BACKGROUND & AIM:Dietary shifts replacing animal protein (AP) with plant protein (PP) sources have been associated with lowering cardiometabolic risk (CMR), but underlying mechanisms are poorly characterized. This nutritional intervention aims to characterize the metabolic changes induced by diets containing different proportions of AP and PP sources in males at CMR. DESIGN:This study is a 4-week, crossover, randomized, controlled-feeding trial in which 19 males with CMR followed two diets providing either 36 % for the control diet (CON-D) or 64 % for the flexitarian diet (FLEX-D) of total protein intake from PP sources. Plasma nontargeted metabolomes (LC-MS method) were measured in the fasted state and after a high-fat challenge meal at the end of each intervention arm. Lipogenesis and protein synthesis fluxes, flow-mediated dilatation (FMD) and gluco-lipidic responses were assessed after the challenge meal. Data were analyzed with mixed models, and univariate and multivariate models for metabolomics data. RESULTS:In both arms CMR improved with time, with decreased body weight (-0.9 %), insulin resistant (-34 %, HOMA-IR, Homeostatic Model Assessment for Insulin Resistance) and low-density lipoproteins (LDL)-cholesterol (-11 %). Diet had no effect on FMD or metabolic fluxes, but a trend (0.05 <p ≤ 0.1) was observed for a stronger decrease in HOMA-IR and lower postprandial glucose after FLEX-D vs CON-D. The abundance of 21 and 37 metabolites differed between diets at fasted and fed states, respectively, including food intake biomarkers of AP (methylhistidine, eicosapentaenoic acid, hydroxyprolines) and PP sources (trigonelline, N-acetyl-ornithine). In fasted or fed states, indole acrylic acid and indole propionic acid, both products of tryptophan catabolism, were higher after FLEX-D vs CON-D, while the indispensable amino acids-related metabolites alpha-aminoadipic acid, hydroxymethylbutyric acids and propionylcarnitine were lower. In the postprandial state only, the ω-oxidation products dodecanedioic, tetradecanedioic and hexadecanedioic acids were higher after FLEX-D vs CON-D. CONCLUSIONS:Despite little changes in risk factors after 4 wk, this study evidenced subtle metabolic adaptations in amino acids and lipid metabolism and gut microbiota activity occurring after higher PP source intake that may be beneficial to CMR. CLINICALTRIALS: GOV STUDY IDENTIFIER:NCT04236518. CLINICAL TRIAL REGISTRY:NCT04236518 on ClinicalTrials.gov.

Background: Plant proteins (PPs) have been associated with better cardiovascular health than animal proteins (APs) in epidemiological studies. However, the underlying metabolic mechanisms remain mostly unknown.Objectives: Using a combination of cutting-edge isotopic methods, we aimed to better characterize the differences in protein and energy metabolisms induced by dietary protein sources (PP compared with AP) in a prudent or western dietary context. Methods: Male Wistar rats (n 1/4 44, 8 wk old) were fed for 4.5 mo with isoproteic diets differing in their protein isolate sources, either AP (100% milk) or PP (50%:50% pea: wheat) and being normal (NFS) or high (HFS) in sucrose (6% or 15% kcal) and saturated fat (7% or 20% kcal), respectively. We measured body weight and composition, hepatic enzyme activities and lipid content, and plasma metabolites. In the intestine, liver, adipose tissues, and skeletal muscles, we concomitantly assessed the extent of amino acid (AA) trafficking using a 15N natural abundance method, the rates of macronutrient routing to dispensable AA using a 13C natural abundance method, and the metabolic fluxes of protein synthesis (PS) and de novo lipogenesis using a 2H labeling method. Data were analyzed using ANOVA and Mixed models.Results: At the whole-body level, PP limited HFS-induced insulin resistance (-27% in HOMA-IR between HFS groups, P < 0.05). In the liver, PP induced lower lipid content (-17%, P < 0.01) and de novo lipogenesis (-24%, P < 0.05). In the different tissues studied, PP induced higher AA transamination accompanied by higher routings of dietary carbohydrates and lipids toward dispensable AA synthesis by glycolysis and beta-oxidation, resulting in similar tissue PS and protein mass.Conclusions: In growing rats, compared with AP, a balanced blend of PP similarly supports protein anabolism while better limiting whole -body and tissue metabolic dysregulations through mechanisms related to their less optimal AA profile for direct channeling to PS.

Background: Alternative, sustainable, and adequate sources of protein must be found to meet global demand. Objectives: Our aim was to assess the effect of a plant protein blend with a good balance of indispensable amino acids and high contents of leucine, arginine, and cysteine on the maintenance of muscle protein mass and function during aging in comparison to milk proteins and to determine if this effect varied according to the quality of the background diet. Methods: Old male Wistar rats (n 1/4 96, 18 mo old) were randomly allocated for 4 mo to 1 of 4 diets, differing according to protein source (milk or plant protein blend) and energy content (standard, 3.6 kcal/g, with starch, or high, 4.9 kcal/g, with saturated fat and sucrose). We measured: every 2 mo, body composition and plasma biochemistry; before and after 4 mo, muscle functionality; after 4 mo, in vivo muscle protein synthesis (flooding dose of L-[1 -13C]-valine) and muscle, liver, and heart weights. Two-factor ANOVA and repeated measures 2-fac-tor ANOVA were conducted. Results: There was no difference between protein type on the maintenance during aging of lean body mass, muscle mass, and muscle functionality. The high-energy diet significantly increased body fat (+47%) and heart weight (+8%) compared to the standard energy diet but had no effect on fasting plasma glucose and insulin. Muscle protein synthesis was significantly stimulated by feeding to the same extent in all groups (+13%). Conclusions: Since high-energy diets had little impact on insulin sensitivity and related metabolism, we could not test the hypothesis that in situations of higher insulin resistance, our plant protein blend may be better than milk protein. However, this rat study offers significant proof of concept from the nutritional standpoint that appropriately blended plant proteins can have high nutritional value even in demanding situations such as aging protein metabolism.

Background and aims Aging is characterized, at the systemic level, by the development of low-grade inflammation, which has been identified as determining sarcopenia by blunting postprandial muscle anabolism. The causes of this “inflammageing” is still not clearly defined. An increased intestinal permeability, a microbiota dysbiosis and subsequent generation of intestinal then generalized inflammation have been hypothesized. The objective of this study was to test in vivo during aging if (1) a chronic low-grade intestinal inflammation can lead to anabolic resistance and muscle loss and (2) if a bacterial strain presenting anti-inflammatory properties could prevent these adverse effects. Methods Young adult (6 m) and elderly rats (18 m) received Dextran Sodium Sulfate (DSS) for 28 days to generate low-grade intestinal inflammation, and received (PB1 or PB2 groups) or not (DSS group) one of the two S. Thermophilus strains (5 × 10 9 CFU/day) previously shown to present an anti-inflammatory potential in vitro . They were compared to pair fed control (PF). Muscle and colon weights and protein synthesis (using 13 C Valine) were measured at slaughter. Muscle proteolysis, gut permeability and inflammatory markers were assessed only in old animals by RT-PCR or proteins quantifications (ELISA). Results In both adult and old rats, DSS reduced absolute protein synthesis (ASR) in gastrocnemius muscle [−12.4% (PB1) and −9.5% (PB2) vs. PF, P < 0.05] and increased ASR in colon (+86% and +30.5%, respectively vs. PF, P < 0.05). PB1 (CNRZ160 strain) but not PB2 resulted in a higher muscle ASR as compared to DSS in adults (+18%, P < 0.05), a trend also observed for PB1 in old animals (+12%, P = 0.10). This was associated with a blunted increase in colon ASR. In old rats, PB1 also significantly decreased expression of markers of autophagy and ubiquitin-proteasome pathways vs. DSS groups and improved gut permeability (assessed by Occludin, Zonula Occludens 1 and Claudin 1 expression, P < 0.05) and alleviated systemic inflammation (A2M: −48% vs. DSS, P < 0.05). Conclusion The loss of muscle anabolism associated with low-grade intestinal inflammation can be prevented by supplementation with anti-inflammatory CNRZ160 strain. We propose that the moderated gut inflammation by CNRZ160 may result in curtailed amino acids (AA) utilization by the gut, and subsequent restored AA systemic availability to support muscle protein accretion. Therefore, CNRZ160 could be considered as an efficient probiotic to modulate muscle mass loss and limit sarcopenia during aging.

Natural abundances of stable nitrogen and carbon isotopes (δ 15 N and δ 13 C) can vary with both dietary intake and metabolic (specifically catabolic) state. In low-income countries, weaning is a period of dietary transition from milk to plant-based foods and a high-risk period for malnutrition. We explored how diet and malnutrition impact hair δ 15 N and δ 13 C in young children by an observational, cross-sectional study in Cox’s Bazar District, Bangladesh [255 children, 6–59 months with 19.6% wasted (7.1% severely) and 36% stunted (9.8% severely)]. Hair δ 15 N and δ 13 C exhibited exponential decreases with age, with the loss of one trophic level (3.3‰ and 0.8‰, respectively) from 6 to 48 months, which we associate with the shift from exclusive breastfeeding to complete weaning. After adjustment for age and breastfeeding status, hair isotopic values were unaffected by wasting but lower in severe stunting (−0.45‰ to −0.6‰, P < 0.01). In this population of young children, whose isotopic values in hair primarily depended on age, we failed to observe any effect of wasting, likely due to opposite, compensating effects between dietary and metabolic changes involved. In contrast, we evidenced low δ 15 N and δ 13 C values in severely stunted children that likely indicate chronic exposure to diets low in animal products.

AbstractIn Western societies, unbalanced diets may lead to intestinal allostatic stress, with microbial dysbiosis and alteration of the gut barrier function. These local modifications may induce a low-grade inflammation via endotoxemic process, which contribute to systemic alterations clustering into the metabolic syndrome (MetS) and increasing the risk of cardiovascular diseases and type 2 diabetes. We investigated the sequence of events initiating the MetS in rats challenged with a diet that differed moderately from the dietary guidelines, regarding the proportions and nature of energy, carbohydrates, lipids and fibre.Male Wistar rats (265 g upon arrival) were with either a standard diet (Con, n = 10, 3730 kcalkg, 4.0% lipids, 6.3% sucrose, 58.0% starch, 5.0% fibre) or a westernized induction diet (Ind, n = 10, moderately enriched in energy (4120 kcal/kg), lipid (24.0%), and sugars (15%, half sucrose-half fructose), and low in starch (25.5%) and fibre (1.25%). An oral glucose tolerance test (OGTT) was performed after 3 weeks. Rats were euthanized after a further week for body composition and collection of caecum content and tissue samples. LPS-binding protein (LPS-BP) was assayed in plasma; ileum and colon samples were used for measurement of wall barrier function (using Ussing chambers) and microbial activity was assessed in caecum (enzymes and metabolites).Body weight did not differ between Con and Ind groups at any time, as well as the absolute masses and proportions of visceral adipose tissue and liver. Fasting triglyceride, glucose, insulin and LPS-BP concentrations, HOMA index and glucose AUC during the OGTT were similar in both groups. When compared to the Con group, Ind rats showed significantly higher risk markers, i.e.: (1) Insulin AUC (x2); (2) Hepatic triglyceride content (x2.8); (3) Wall permeability at both the para- and transcellular levels (x2.6 and 4.3, respectively) in the ileum (but not in the colon). In the caecum, H2S absolute and relative amounts were twice higher in the Ind group, in relation with 2–3-fold increases in specific and total activities of microbial cysteine desulfhydrase and proteases.Multiple dietary changes mimicking a moderately westernized diet induced an increased ileal permeability and changes in the caecal microbial activity, without evidence of endotoxemia. These perturbations were associated with detrimental rupture of homeostasis at both the splanchnic (hepatic steatosis) and systemic (insulin resistance) levels. In this realistic model, these alterations preceded the occurrence of clinical markers of the MetS (obesity and elevated plasma concentrations of glucose and triglyceride).

Introduction et but de l’etude : Dans le contexte de la transition nutritionnelle en cours vers davantage de proteines vegetales (PV) et moins de proteines animales (PA) pour des raisons de durabilite, les PV sont reputees de moindre qualite que les PA du fait de leurs moindres teneurs en acides amines indispensables. Ici, nous avons analyse comment la composition corporelle et le metabolisme proteique tissulaire varient selon la source proteique et les nutriments energetiques.Materiel et methodes : 44 rats Wistar mâles ont ete nourris avec 4 regimes iso-proteiques (15% de l’energie du regime, couvrant les besoins des rats en croissance) constitues de PA (lait) ou PV (50-50 ble-pois) avec des teneurs en lipides et sucres simples normales (N, 27% et 6% de l’energie du regime, respectivement) ou hautes (H, 55% et 20%, respectivement). Consommation alimentaire, poids et composition corporelle (IRM) ont ete suivis pendant 4 mois avant euthanasie et prelevement de tissus (intestin, foie, muscles tibialis anterior et gastrocnemius). Les masses des proteines tissulaires ont ete mesurees par analyse elementaire de leur contenu en N. Les flux de proteosyntheses tissulaires ont ete mesures par tracage isotopique au ²H (surchargei.p. initiale de ²H2O a 99,9% 2j avant l’euthanasie, puis ²H2O a 5% comme eau de boisson), et calcules a partir des enrichissements en ²H dans l’alanine libre et liee aux proteines tissulaires mesures en GC-MS. En outre, nous avons estime l’ampleur des remaniements metaboliques des acides amines dans les tissus par les ecarts d’abondance naturelle en 15N entre proteines alimentaires et tissulaires (Δ15N, ‰), mesures en EA-IRMS.Resultats et Analyse statistique : Les 4 regimes etaient associes a des consommations de proteines et d’energie totale similaires, mais avec de plus fortes consommations de lipides (x 2,2) et saccharose (x 2,6) pour les regimes H vs N. Cette consommation plus grasse et sucree (H vs N) induisait un poids corporel ~10% superieur du fait d’une masse grasse ~35% superieure, avec une masse maigre similaire et des masses et flux de syntheses proteiques similaires dans tous les tissus sauf le foie ou ils etaient ~20% superieurs. La source proteique (PV vs PA) n’affectait ni le poids, ni la masse maigre, ni les masses et flux de syntheses proteiquestissulaires. Mais par rapport aux PA, les PV induisaient une plus grande orientation des acides amines vers les processus isotopiquement discriminants de transaminations dans tous les tissus etudies (Δ15N superieurs de ~0,25 a 0,45 ‰).Conclusion : Un melange equilibre de proteines de cereales et legumineuses assure tout aussi bien que les proteines de lait la synthese et le renouvellement des proteines des differents tissus, grâce a l’activation de remaniements metaboliques permettant d’adapter le profil d’apport en acides amines a la demande metabolique tissulaire. Ces remaniements metaboliques ont vraisemblablement un cout et un impact sur le metabolisme energetique qu’il serait interessant d’explorer, notamment dans le contexte du risque cardiometabolique.

Sphingolipids appear as a promising class of components susceptible to prevent the onset of the metabolic syndrome (MetS). Gut availability and effects of Camelina sativa sphingolipids were investigated in a mouse model of dietary-induced MetS. Seed meals from two Camelina sativa lines enriched, respectively, in C24- and C16-NH2- glycosyl-inositol-phosphoryl-ceramides (NH2GIPC) were used in hypercaloric diets. After 5 weeks on these two hypercaloric diets, two markers of the MetS were alleviated (adiposity and insulin resistance) as well as inflammation markers and colon barrier dysfunction. A more pronounced effect was observed with the C16-NH2GIPC-enriched HC diet, in particular for colon barrier function. Despite a lower digestibility, C16-NH2GIPC were more prevalent in the intestine wall. Sphingolipids provided as camelina meal can therefore counteract some deleterious effects of a hypercaloric diet in mice at the intestinal and systemic levels. Interestingly, these beneficial effects seem partly dependent on sphingolipid acyl chain length.

A growing body of evidence supports a role for tissue-to-diet 15N and 13C discrimination factors (Δ15N and Δ13C), as biomarkers of metabolic adaptations to nutritional stress, but the underlying mechanisms remain poorly understood. In obese rats fed ad libitum or subjected to gradual caloric restriction (CR), under a maintained protein intake, we measured Δ15N and Δ13C levels in tissue proteins and their constitutive amino acids (AA) and the expression of enzymes involved in the AA metabolism. CR was found to lower protein mass in the intestine, liver, heart and, to a lesser extent, some skeletal muscles. This was accompanied by Δ15N increases in urine and the protein of the liver and plasma, but Δ15N decreases in the proteins of the heart and the skeletal muscles, alongside Δ13C decreases in all tissue proteins. In Lys, Δ15N levels rose in the plasma, intestine, and some muscles, but fell in the heart, while in Ala, and to a lesser extent Glx and Asx, Δ13C levels fell in all these tissues. In the liver, CR was associated with an increase in the expression of genes involved in AA oxidation. During CR, the parallel rises of Δ15N in urine, liver, and plasma proteins reflected an increased AA catabolism occurring at the level of the liver metabolic branch point, while Δ15N decreases in cardiac and skeletal muscle proteins indicated increased protein and AA catabolism in these tissues. Thus, an increased protein and AA catabolism results in opposite Δ15N effects in splanchnic and muscular tissues. In addition, the Δ13C decrease in all tissue proteins, reflects a reduction in carbohydrate (CHO) oxidation and routing towards non-indispensable AA, to achieve fuel economy.

Toll-like receptor 4 (TLR4), an innate immune receptor, is suspected to play a key role in the postprandial inflammation that is induced by a high-fat meal rich in saturated fatty acids (SFA). Our objective was to test this hypothesis by using a specific competitive inhibitor of TLR4 (INH) vs vehicle (VEH) administered immediately before a high-SFA meal in rats.

Alterations in NO availability and signaling play a pivotal role at early stages of the metabolic syndrome (MetSynd). We hypothesized that dietary α-linolenic acid (ALA, 18:3 n-3) favors NO availability by modulating amino acid metabolism, with a specific impact on the arginine–NO pathway. Mice were fed a hyperlipidic diet (285 g lipid/kg, 51.1 % energy), rich in either saturated fatty acids (SFA, provided by palm oil, PALM group) or ALA (provided by linseed oil, LIN group). We measured whole-body NO synthesis and systemic arginine hydrolysis with a tracer-based method, plasma concentration of related metabolites, and hepatic mRNA level of related enzymes, and the study was completed by a transcriptomic analysis in the liver. As expected with this model, hyperlipidic diets resulted in increased adiposity and glycemia after 5 weeks. As compared to PALM mice, LIN mice had a higher plasma nitrite and nitrate concentration, a higher whole-body conversion of arginine into NO vs urea, and a similar plasma concentration of asymmetric dimethylarginine (ADMA), despite a higher expression of the liver dimethylargininase-1. In LIN mice, there was a higher expression of genes involved in PPARα signaling, but a little impact on gene expression related to amino acids and arginine metabolism. This effect cannot be directly ascribed to changes in arginase activity in the liver or ADMA metabolism, nor to direct regulation of the related target genes. In conclusion, dietary ALA favors NO synthesis, which could contribute to rescue NO availability when jeopardized by the nutritional conditions in relation with the initiation of the MetSynd.

Introduction et but de l’etude : Il existe une forte variabilite interindividuelle de reponse a une alimentation trop grasse et sucree : chez les individus les moins aptes a gerer cet exces chronique d'energie, elle favorise le developpement d'une obesite (O) parfois associee a un syndrome metabolique (SM), avec des alterations du metabolisme energetique mais aussi probablement du metabolisme proteique qui sont encore mal connues. Cette etude visait a mieux identifier la variabilite de reponse a un regime gras et sucre ainsi que les differences metaboliques entre individus sensibles et resistants a l'O et au SM, en utilisant des biomarqueurs isotopiques des orientations preferentielles du metabolisme proteique, les abondances naturelles en 15N (δ15N) des tissus. Materiel et methodes : 36 rats Wistar mâles, de poids initialement similaires, ont ete nourris avec un regime riche en lipides et sucres, suivis pour leurs consommation et gain de poids pendant 4 mois puis euthanasies pour mesurer parametres biochimiques, composition corporelle et δ15N des proteines tissulaires par spectrometrie de masse a ratio isotopique. Nous avons discrimine les rats selon leur sensibilite a l'O et au SM par une classification non supervisee (proc cluster sous SAS), sur la base de 2 indicateurs d'O (poids et adiposite viscerale) et de 2 indicateurs de SM (HOMAIR et triglycerides hepatiques). Nous avons calcule le Zscore global d'O et de SM (ZOSM) comme la moyenne des Zscores de ces 4 indicateurs, puis analyse les correlations entre ZOSM, efficacites proteiques tissulaires (proteines tissulaires / proteines ingerees) et δ15N tissulaires. Resultats et Analyse statistique : La classification a distingue 3 groupes de rats : resistants a l'O et au SM (R, n=12), sensibles a l'O mais resistants au SM (O, n=12), ou sensibles a l'O et au SM (OSM, n=12). Les rats R, O et SM avaient les caracteristiques suivantes (moyennes ± ecart-types, significativement differentes si elles portent des lettres differentes) : poids de 542 ± 42a, 620 ± 44b et 670 ± 33c g ; adiposite viscerale de 6,9 ± 0,5a, 8,3 ± 0,3b et 8,6 ± 0,7b % ; HOMA-IR de 7,1 ± 3,4a, 10,0 ± 5,7a et 21,7 ± 7,3b μg·mmol·L-2 ; triglycerides hepatiques de 57 ± 14a, 62 ± 20a et 101 ± 13 b μmol·g-1 ; efficacites proteiques de 2,37 ± 0,20a, 2,41 ± 0,31ab et 2,62 ± 0,18b % dans le foie, 0,53 ± 0,08a, 0,49 ± 0,04a et 0,43 ± 0,04b % dans le muscle gastrocnemien, et 0,19 ± 0,02a, 0,17 ± 0,02ab et 0,16 ± 0,02b % dans le muscle tibialis. Le ZOSM etait correle (P<0,01) positivement a l'efficacite proteique du foie (R=0,54) et negativement a celles des muscles gastrocnemien (R=-0,48) et tibialis (R=-0,45), et negativement au δ15N des proteines du foie (R=-0,47), erythrocytes (R=- 0,43) et poils (R=-0,49). Conclusion : Dans ce modele, la sensibilite a l'O et au SM concerne 2/3 de la population, avec 1/3 en O saine et 1/3 en O avec SM. Chez les individus sensibles, l'efficacite d'utilisation anabolique des proteines alimentaires est plus grande dans le foie mais plus faible dans certains muscles, et la plus grande efficacite anabolique hepatique est liee a une moindre orientation catabolique des acides amines dont attestent les plus faibles δ15N du foie et d'autres pools plus accessibles (erythrocytes, poils). Conflits d’interets: Aucun conflit a declarer

In obese subjects, the loss of fat mass during energy restriction is often accompanied by a loss of muscle mass. The hypothesis that n-3 PUFA, which modulate protein homoeostasis via effects on insulin sensitivity, could contribute to maintain muscle mass during energy restriction was tested in rats fed a high-fat diet (4 weeks) rich in 18 : 1 n-9 (oleic acid, OLE-R), 18 : 3 n-3 (α-linolenic acid, ALA-R) or n-3 long-chain (LC-R) fatty acid and then energy restricted (8 weeks). A control group (OLE-ad libitum (AL)) was maintained with AL diet throughout the study. Rats were killed 10 min after an i.v. insulin injection. All energy-restricted rats lost weight and fat mass, but only the OLE-R group showed a significant muscle loss. The Gastrocnemius muscle was enriched with ALA in the ALA-R group and with LC-PUFA in the ALA-R and LC-R groups. The proteolytic ubiquitin-proteasome system was differentially affected by energy restriction, with MAFbx and muscle ring finger-1 mRNA levels being decreased in the LC-R group (-30 and -20 %, respectively). RAC-α serine/threonine-protein kinase and insulin receptor substrate 1 phosphorylation levels increased in the LC-R group (+70 %), together with insulin receptor mRNA (+50 %). The ALA-R group showed the same overall activation pattern as the LC-R group, although to a lesser extent. In conclusion, dietary n-3 PUFA prevent the loss of muscle mass associated with energy restriction, probably by an improvement in the insulin-signalling pathway activation, in relation to enrichment of plasma membranes in n-3 LC-PUFA.

BACKGROUND:Oral l-arginine supplements can have a beneficial effect on nitric oxide (NO)-related functions when subjects have cardiovascular disease risk factors.OBJECTIVE:The study was designed to determine the utilization for NO synthesis of oral l-arginine as a function of the cardiometabolic risk and the speed of absorption by comparing immediate-release arginine (IR-Arg), as in supplements, and sustained-release arginine (SR-Arg), which mimics the slow release of dietary arginine.METHODS:In a randomized, single-blind, 2-period crossover, controlled trial (1 wk of treatment, >2 wk of washout), using [(15)N-(15)N-(guanidino)]-arginine for the first morning dose, we compared the bioavailability (secondary outcome) and utilization for NO synthesis (primary outcome) of 1.5 g IR- and SR-Arg 3 times/d in 12 healthy overweight [body mass index (BMI; in kg/m(2)): 25-30] adults with the hypertriglyceridemic waist phenotype [HTW; plasma triglycerides (TGs): >150 mg/dL; waist circumference: >94 cm (men) or >80 cm (women)] and 15 healthy control adults (CON; BMI: 18.5-25; no elevated TGs and waist circumference).RESULTS:Plasma oral arginine areas under the curve were lower after supplementation with SR-Arg than with IR-Arg (112 ± 52.3 and 142 ± 50.8 μmol ⋅ h/L; P < 0.01). The utilization of oral arginine for NO synthesis was 58% higher in HTW subjects than in CON subjects and higher with SR-Arg than with IR-Arg (P < 0.05 both), particularly in HTW subjects (group-by-treatment interaction, P < 0.05). In HTW subjects administered the SR form, utilization for NO synthesis was 32% higher than with the IR form and 87% higher than in CON subjects who were administered the SR form.CONCLUSION:In overweight adults with the HTW phenotype, a slow- compared with a fast-release form of oral arginine markedly favors the utilization of arginine for NO synthesis. The utilization of low-dose, slow-release arginine for NO synthesis is higher in overweight adults with the HTW phenotype than in healthy controls, suggesting that the sensitivity of NO synthesis to the dietary arginine supply increases with cardiometabolic risk. The trial was registered at clinicaltrials.gov as NCT02352740.