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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 = 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 15 N natural abundance method, the rates of macronutrient routing to dispensable AA using a 13 C natural abundance method, and the metabolic fluxes of protein synthesis (PS) and de novo lipogenesis using a 2 H 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 β-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., (Copyright © 2022 American Society for Nutrition. Published by Elsevier Inc. All rights reserved.)

Background: Plant-based substitutes are designed to have the same use as animal-based foods in the diet and could therefore assist the transition toward more plant-based diets. However, their nutritional impact has not been characterized., Objectives: We assessed and compared the effects of plant-based substitutes on the nutritional quality of the diet., Methods: We simulated separately the substitution of meat, milk, and dairy desserts with 96 plant-based substitutes in the diets of 2121 adults (18-79 y old) from the cross-sectional French Third Individual and National Study on Food Consumption Survey (INCA3; 2014-2015). The quality of initial individual diets and the 203,616 substituted diets was evaluated using the Probability of Adequate Nutrient Intake (PANDiet) scoring system, which assesses the probability of adequate (sufficient and not excessive) nutrient intake; also, nutrient security was evaluated using the SecDiet scoring system, which assesses the risk of overt deficiency., Results: Impacts on PANDiet depended on both the food substituted and the types of substitutes. Soy-based substitutes provided a slight improvement in diet quality (0.8% increase of the PANDiet score when substituting meat), whereas cereal-based substitutes resulted in a 1.1% decrease. Globally, substitutions led to better adequacies for fiber, linoleic acid, α-linolenic acid, vitamin E, folate, and SFAs, but lower adequacies regarding vitamin B-12 and riboflavin, as well as bioavailable zinc and iron when substituting meat, and calcium and iodine when substituting milk/dairy desserts. When they substituted dairy products, calcium-fortified substitutes allowed maintenance of calcium adequacy but there was a higher risk of iodine deficiency when substituting dairy, which may warrant iodine fortification. Substitutions modified the energy share of ultra-processed foods from 29% to 27%-40%, depending on the food substituted and the substitute used., Conclusions: Plant-based substitutes had a small effect on overall diet quality and heterogeneous impacts on nutrient adequacy and security. Plant-based substitutes that include legumes appear more nutritionally adequate to substitute animal products than do other substitutes., (© The Author(s) 2021. Published by Oxford University Press on behalf of the American Society for Nutrition.)

Background: There is a current trend in Western countries toward increasing the intake of plant protein. A higher plant-protein intake has been associated with nutritional and health benefits, but these may depend on the pattern of plant-protein sources., Objective: We hypothesized that the diversity of plant foods could be important to nutrient adequacy when increasing plant-protein intake in the diet., Methods: Using data on 1341 adults (aged 18-64 y) from a representative French national dietary survey conducted in 2014-2015 (the third Individual and National Study on Food Consumption Survey-INCA3), we studied the links between plant-protein intake, dietary diversity (using various dimensions), and nutrient adequacy [assessed using the PANDiet (Probability of Adequate Nutrient Intake) scoring system, comprising adequacy (AS) and moderation (MS) subscores]. We simulated substituting plant-protein foods for animal-protein foods using different models of plant-protein diversity., Results: We found that overall diet quality was weakly associated with total and protein diversity and more strongly with plant-protein diversity. Plant-protein intake was inversely associated with animal-protein intake, and positively with the PANDiet and MS, but not with the AS. Plant-protein intake displayed little diversity, mostly taking the form of grains (61% of plant-protein intake), and this diversity was even less marked under a higher plant-protein intake. Finally, modeled substitutions showed that reducing animal-protein intake increased the MS (by 32%) in a similar manner whichever plant protein was used for substitution, whereas it decreased the AS (by 20%) unless using a highly diversified plant-protein mix. These simulated improvements in overall adequacy included marked decreases in adequacy regarding certain nutrients that are typically of animal origin., Conclusions: We conclude that in French adults the current pattern of plant-protein intake is hindering the nutritional benefits of a transition toward more plant protein, indicating that the consumption of plant-protein-based foods other than refined grains should be encouraged., (Copyright © The Author(s) 2019.)

Background: Patterns of protein food intake are undergoing a transition in Western countries, but little is known about how dietary changes to protein intake affect nutrient adequacy of the diet., Objectives: Our objective was to identify simple modifications to protein food intake that can gradually increase overall nutrient adequacy., Methods: We identified patterns of dietary protein intake in 1678 adults from a representative French national dietary survey. For each individual, we identified the increase in portion size of 1 protein food paired with a decrease in the portion size of another protein food that would best increase nutrient adequacy (using PANDiet probabilistic scoring). Then, such an optimum simple dual change was iterated 20 times for each individual according to 2 scenarios, either by manipulating the intake of foods already consumed [scenario 1 (S1)] or by enabling the introduction of foods consumed by >10% of individuals with the same protein pattern [scenario 2 (S2)]., Results: The optimum stepwise changes to protein intake primarily consisted of reducing portions of deli meats (both scenarios), sandwiches, and cheese (S2), while increasing portions of fatty fish and lean poultry (both scenarios) and legumes (S2). However, these changes differed depending on the initial dietary protein pattern of the individual. For example, in S2, legume intake increased among "poultry" and "fish" eaters only and low-fat meat among "take-away eaters" and "milk drinkers" only. The improvements in overall nutrient adequacy were similar among the different initial dietary patterns, but this was the result of changes to the adequacy of different specific nutrients., Conclusion: Beyond generic changes to protein intake in the entire French adult population, the initial dietary protein pattern is key to identifying the food groups most likely to improve overall nutrient adequacy and the profile of nutrients whose adequacy can easily be increased., (© 2019 American Society for Nutrition.)

Background: A meal rich in saturated fatty acids induces a postprandial metabolic challenge. The type of dietary protein may modulate postprandial metabolism., Objective: We studied the effect of dietary protein type on postprandial changes in the metabolome after a high-fat meal., Methods: In a 3-period, crossover, postprandial study, 10 healthy overweight men with an elevated waist circumference (>94 cm) ingested high-fat meals made up of cream fat (70% of energy), sucrose (15% energy), and protein (15% energy) from either casein (CAS), whey protein (WHE), or α-lactalbumin-enriched whey protein (LAC). Urine collected immediately before and 2, 4, and 6 h after the meal was analyzed for metabolomics, a secondary outcome of the clinical study. We used mixed-effect models, partial least-square regression, and pathway enrichment analysis., Results: At 4 and 6 h after the meal, the postprandial metabolome was found to be fully discriminated according to protein type. We identified 17 metabolites that significantly explained the effect of protein type on postprandial metabolomic changes (protein-time interaction). Among this signature, acylcarnitines and other acylated metabolites related to fatty acid or amino acid oxidation were the main discriminant features. The difference in metabolic profiles was mainly explained by urinary acylcarnitines and some other acylated products (protein type, Ps < 0.0001), with a dramatically greater increase (100- to 1000-fold) after WHE, and to a lesser extent after LAC, as compared with CAS. Pathway enrichment analysis confirmed that the type of protein had modified fatty acid oxidation (P < 0.05)., Conclusion: Taken together, our results indicate that, in healthy overweight men, the type of protein in a high-fat meal interplays with fatty acid oxidation with a differential accumulation of incomplete oxidation products. A high-fat meal containing WHE, but not CAS, resulted in this outpacing of the tricarboxylic acid cycle. This study was registered at clinicaltrials.gov as NCT00931151.

Background: Limited evidence is available on the impact that unconditional cash transfer (UCT) programs can have on child nutrition, particularly in West Africa, where child undernutrition is still a public health challenge. Objective: This study examined the impact of a multiannual, seasonal UCT program to reduce the occurrence of wasting (weight-for-height, midupper arm circumference), stunting (height-for-age), and morbidity among children <36 mo old in Tapoa Province, in the eastern region of Burkina Faso. Methods: The study was designed as a 2-arm cluster-randomized controlled trial, with 32 villages randomly assigned to either the intervention or the control group. The study population comprised households that were classified as poor or very poor according to household economy approach criteria and that had ≥1 child <1 y of age at inclusion. The intervention consisted of seasonal UCTs, provided monthly from July to November, over 2 y (2013 and 2014). A monthly allowance of 10,000 West African Financial Community of Africa francs (∼US$17) was given by mobile phone to mothers in participating households. Anthropometric measurements and morbidity were recorded on a quarterly basis. Results: We found no evidence that multiannual, seasonal UCTs reduced the cumulative incidence of wasting in young children [incidence rate ratio: 0.92 (95% CI: 0.64, 1.32); P = 0.66]. We observed no significant difference ( P > 0.05) in children's anthropometric measurements and stunting between the 2 groups at the end point. However, children in the intervention group had a lower risk [21% (95% CI: 18.6%, 21.3%); P < 0.001] of self-reported respiratory tract infections than did children in the control group. Conclusions: We found that seasonal UCTs in the framework of safety nets did not result in a significant decrease in the incidence of acute malnutrition among children in Tapoa Province. Cash transfers combined with complementary interventions targeted to child nutrition and health should be investigated further. This trial was registered at clinicaltrials.gov as NCT01866124., Competing Interests: Author disclosures: J-FH, LH, and PK, no conflicts of interest. FH, AT-P, CA, and MA-A are employed by Action Against Hunger France, which implemented the MAM’Out study., (© 2017 American Society for Nutrition.)

Background: Cash transfer programs have the potential to improve dietary intake by improving accessibility to food. However, quantitative data on the impact of cash transfer programs on children's energy and nutrient intakes are lacking. Objective: The aim of this study was to evaluate the effect of seasonal unconditional cash transfers on children's energy, micro- and macronutrient, and food group intakes during the lean season in Burkina Faso. Methods: Within the framework of the MAM'Out (Moderate Acute Malnutrition Out) cluster-randomized controlled trial, two 24-h dietary recall surveys were conducted in July and August 2014. Daily energy and macro- and micronutrient intakes, breastfeeding practices, and food group consumption were analyzed for 322 children aged 14-27 mo from an intervention group (benefiting from unconditional cash transfer during the lean season in 2013 and 2014) and a control group by using mixed linear, logistic, and Poisson regression models or a γ-generalized linear model with log-link. A dietary diversity score was calculated on the basis of 7 food groups. Results: Unconditional cash transfers during the lean season improved the diets of rural children through a higher consumption of eggs (11.3 ± 1.55 compared with 3.25 ± 0.79 g; P < 0.001), fat (20.6 ± 0.80 compared with 16.5 ± 0.89 g; P < 0.01), and vitamin B-12 (0.40 ± 0.02 compared with 0.34 ± 0.02 mg; P < 0.001) compared with controls and higher proportions of children consuming dairy products (OR: 4.14; 95% CI: 1.48, 11.6; P < 0.05), flesh foods (OR: 2.09; 95% CI: 1.18, 3.70; P < 0.05), and iron-rich or iron-fortified foods (OR: 2.23; 95% CI: 1.20, 4.13; P < 0.05). No difference was found in energy intake between the 2 groups. The minimum dietary diversity of two-thirds of the children who benefited from cash transfers was adequate compared with only one-third in the control group ( P < 0.001). Conclusions: Unconditional seasonal cash transfer increases intakes of high-nutritional-value foods in Burkinabe children aged 14-27 mo. As such, their use can be recommended in actions addressing children's dietary intake during the lean season. This trial was registered at clinicaltrials.gov as NCT01866124., Competing Interests: Author disclosures: LH, PK, and J-FH, no conflicts of interest. AT-P, FH, CA, and MA-A are currently employed by Action Contre la Faim, which implemented the MAM’Out study., (© 2017 American Society for Nutrition.)

Background: Plant protein intake, which is favorably associated with the intake of many nutrients, is a marker of a healthy diet. However, the higher nutrient adequacy of diets rich in plant protein may also originate from overarching factors associated with more healthful dietary behaviors, such as a greater dietary diversity., Objective: Our main objective was to determine whether the relation between plant protein intake and nutrient adequacy could be explained, at least in part, by an association with overall dietary diversity., Methods: We used data from 1330 adults participating in the French Nutrition and Health Survey [Etude Nationale Nutrition Santé (ENNS); 2006-2007]. With the use of global, integrative approaches, we assessed nutrient adequacy [by using the probabilistic PANDiet (Probability of Adequate Nutrient Intake) scoring system] and overall dietary diversity (by using a 100-point score that accounts for the relative number of subgroups consumed in 7 food groups). Linear multivariate modeling was used for the analysis., Results: We found a positive association between plant protein (but not total or animal protein) intake and dietary diversity (β = 0.08) and a strong positive association between dietary diversity and nutrient adequacy (β = 0.33). However, the association between plant protein intake and nutrient adequacy was not explained by dietary diversity (r = 0.38 and partial r = 0.36, P < 0.0001). In multivariate analysis, nutrient adequacy was positively associated with dietary diversity (β = 0.44) and plant (β = 0.37) and animal (β = 0.15) protein intakes. Associations persisted after adjustment for potential confounders (total energy, energy density, sex, body mass index, income, occupational status, educational level, region, season, and smoking status)., Conclusions: Overall dietary diversity is greater in French adults who consume more plant protein. Both plant protein intake and dietary diversity are associated with the nutrient adequacy of the diet. But the plant protein-nutrient adequacy association was not related to the relative overall diversity of the diet., (© 2016 American Society for Nutrition.)

Background: Vascular endothelial dysfunction, the hallmark of early atherosclerosis, is induced transiently by a high-fat meal. High doses of free l-arginine supplements reduce fasting endothelial dysfunction., Objective: We sought to determine the effects of a low dose of a sustained-release (SR) l-arginine supplement on postprandial endothelial function in healthy overweight adults with cardiometabolic risk factors and to investigate whether this effect may vary by baseline arginine status., Methods: In a randomized, double-blind, 2-period crossover, placebo-controlled trial (4-wk treatment, 4-wk washout), we compared the effects of 1.5 g SR-l-arginine 3 times/d (4.5 g/d) with placebo in 33 healthy overweight adults [body mass index (BMI, in kg/m(2)): 25 to >30] with the hypertriglyceridemic waist (HTW) phenotype [plasma triglycerides > 150 mg/dL; waist circumference > 94 cm (men) or > 80 cm (women)]. The main outcome variable tested was postprandial endothelial function after a high-fat meal (900 kcal), as evaluated by use of flow-mediated dilation (FMD) and Framingham reactive hyperemia index (fRHI), after each treatment. By use of subgroup analysis, we determined whether the effect was related to the baseline plasma arginine concentration., Results: In the total population, the effects of SR-arginine supplementation on postprandial endothelial function were mixed and largely varied with baseline fasting arginine concentration (P-interaction < 0.05). In the lower half of the population (below the median of 78.2 μmol arginine/L plasma), but not the upper half, SR-arginine supplementation attenuated the postprandial decrease in both FMD (29% decrease with SR-arginine compared with 50% decrease with placebo) and fRHI (5% increase with SR-arginine compared with 49% decrease with placebo), resulting in significantly higher mean ± SEM values with SR-arginine (FMD: 4.0% ± 0.40%; fRHI: 0.41 ± 0.069) than placebo (FMD: 2.9% ± 0.31%; fRHI: 0.21 ± 0.060) at the end of the postprandial period (P < 0.05)., Conclusions: Supplementation with low-dose SR-arginine alleviates postprandial endothelial dysfunction in healthy HTW adults when the baseline plasma arginine concentration is relatively low. The benefits of arginine supplementation may be linked to a lower ability to mobilize endogenous arginine for nitric oxide synthesis during a postprandial challenge. This trial was registered at clinicaltrials.gov as NCT02354794., (© 2016 American Society for Nutrition.)

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., (© 2016 American Society for Nutrition.)

Background: Postprandial lipemia is a risk factor for cardiovascular disease. The potential impacts of the type/nature of dietary protein on postprandial lipemia and associated dysregulations have been insufficiently investigated., Objective: We investigated the postprandial effect of including in a high-fat meal some milk protein fractions that markedly differ in their physicochemical properties and composition [either casein (CAS), whey protein (WHE), or α-lactalbumin-enriched whey protein (LAC)]., Methods: The protein fractions were incorporated as 15% energy in a high-fat meal in a 3-period, crossover postprandial study of 10 healthy overweight men with an elevated waist circumference (>94 cm). We measured postprandial changes in plasma lipids, amino acids, glucose, and oxidative stress markers, vascular function (using pulse contour analysis), and low-grade inflammation (using plasma markers). We also characterized in vitro the meal structures, including the size of the fat globule, and possible changes during digestion., Results: The type of protein did not affect postprandial plasma glucose, amino acids, insulin, or nonesterified fatty acids, but, compared with WHE and LAC, which did not differ, CAS markedly reduced postprandial triglycerides (TGs), achieving a 22 ± 10% reduction in the 6-h area under the curve (P < 0.05). Similar trends were shown for plasma chylomicrons [apolipoprotein (apo)B-48; P < 0.05]. However, there were no significant differences between the meals regarding postprandial oxidative stress (plasma hydroperoxides and malondialdehyde), endothelial dysfunction (salbutamol-induced changes in pulse contour analysis), or low-grade inflammation. In vitro studies showed that when the pH of the meal decreased to stomach pH values, the reduction in the solubility of casein resulted in a phase separation between fat and protein, whereas the proteins in the other meals remained suspended with fat globules., Conclusion: In healthy overweight men, casein has specific physical interactions with fat that affect postprandial TGs, leading to the formation of fewer chylomicrons or an increase in chylomicron clearance. This trial was registered at clinicaltrials.gov as NCT00931151., (© 2015 American Society for Nutrition.)

Identifying the dietary changes with the greatest potential for improving diet quality is critical to designing efficient nutrition communication campaigns. Our objective was to simulate the effects of different types of dietary substitutions to improve diet quality at the individual level. Starting from the observed diets of 1330 adults participating in the national French Nutrition and Health Survey (Etude Nationale Nutrition Santé), we simulated the effects of 3 different types of food and beverage substitutions with graded implementation difficulty for the consumer in a stepwise dietary counseling model based on the improvement in the PANDiet index, which measures diet quality in terms of nutrient adequacy. In scenario 1, substitutions of a food or beverage for its "lighter" version resulted in a modest improvement in the PANDiet score (Δ = +3.3 ± 0.1) and a decrease in energy intake (Δ = -114 ± 2 kcal/d). In scenario 2, substitutions of a food or beverage within the same food subgroup resulted in a marked improvement in the PANDiet score (Δ = +26.4 ± 0.2) with no significant change in energy intake. In this second scenario, the improvement in nutrient adequacy was due to substitutions in many subgroups, with no single subgroup contributing >8% to the increase in the PANDiet score. In scenario 3, substitutions of a food or beverage within the same food group resulted in the greatest improvement in the PANDiet score (Δ = +31.8 ± 0.2) but with an increase in energy intake (Δ = +204 ± 9 kcal/d). In this third scenario, the improvement in nutrient adequacy was largely due to substitutions of fish for meat and processed meat (∼30% of the increase in the PANDiet score). This study shows that a strategy based on simple substitutions within food subgroups is effective in rapidly improving the nutritional adequacy of the diet of French adults and could be used in public health nutrition actions., (© 2014 American Society for Nutrition.)

The sustainability of dietary plant and animal protein consumption is an important issue, but few data are available to ascertain the health-related impact of animal and plant protein intake. The objective was to study the relationships between animal and plant protein intake and diet quality, as reflected by an integrated index of nutrient adequacy. Using data on 1912 adults from the French Individual and National Consumption Survey 2 (2006-2007), we assessed diet quality by using the PANDiet, a unique score combining 35 probabilities of having an adequate nutrient intake, and used multiple regression analysis to study the relationship with intakes of plant, animal, and related food source proteins. After adjustments for intakes of energy, alcohol, and protein from other sources and sociodemographic factors, plant protein intake was positively associated with the PANDiet, irrespective of sex (β = 0.50, P < 0.0001). By contrast, total and animal protein intakes were differently associated with the PANDiet according to sex, with a positive association in women (β = 0.07 and β = 0.08, respectively; P < 0.01) and an inverse association in men (β = -0.07 and β = -0.05, respectively; P < 0.01). The relationships between the PANDiet and intakes of protein from animal food sources varied: for instance, associations were inverse for red meat and poultry in men but not in women, whereas irrespective of sex, they were positive for fish, milk, and yogurt and inverse for processed meat, cheese, and eggs. These findings show that plant protein is a robust marker of a healthy diet, whereas total animal protein includes different subtypes of animal protein that largely vary in their relationship with diet quality. These data could help refine protein recommendations from a qualitative and dietary standpoint.

High-saturated fat and high-sucrose meals induce vascular endothelial dysfunction, the early hallmark of atherogenesis. The impact of dietary protein on vascular homeostasis remains misunderstood. In this study, we investigated whether rapeseed protein, an emergent arginine- and cysteine-rich protein, can acutely modulate the onset of adverse effects induced by a high-saturated fat meal (HFM). In a series of crossover experiments, healthy rats received 3 HFM (saturated fat: 60%; sucrose: 20%; protein: 20% energy) with the protein source being either total milk protein (MP; control), rapeseed protein (RP), or MP supplemented with cysteine and arginine to the same level as in RP (MP+AA). Endothelium-related vascular reactivity, measured as an acetylcholine-induced transient decrease in blood pressure, and plasma triglycerides, hydroperoxides, cyclic GMP (cGMP), and free 3-nitrotyrosine were measured before and 2, 4, and 6 h after meals. Superoxide anion production, expressed as ethidine fluorescence, was measured in the aorta 6 h after meals. Whereas plasma triglycerides rose similarly in all meals, the decrease in vascular reactivity after MP was attenuated after MP+AA and entirely prevented after RP. The type of meal had no consistent effect on plasma cGMP and free 3-nitrotyrosine over the postprandial period. The postprandial increase in plasma hydroperoxides differed according to the meal, and concentrations were 43% lower 6 h after MP+AA and RP than after MP. Aortic superoxide anion production was 36% lower 6 h after RP than MP. These results show that substituting rapeseed protein for milk protein markedly reduces vascular and oxidative disturbances induced by an HFM and this may be mediated in part by cysteine and arginine.

Postprandial endothelial dysfunction is a key event mediating the effects of diet on early atherogenesis. The potential effects of protein intake have been overlooked in the past, although amino acids are precursors for homocysteine and nitric oxide (NO). Our objective was to study the effect of amino acids on postprandial vascular function, in relation to the utilization of meal arginine for NO production. In a crossover design, 9 men ingested 50 g of a complete amino acid mixture, trace-labeled with (13)C-glycine and (15)N(2)-arginine, without (meal A) or with (meal B) 3 g extra arginine. The postprandial utilization of meal arginine for NO production was determined from urinary (15)NO(3). We monitored endothelial function of the brachial artery, the stiffness of the common carotid artery, aortic pulse wave velocity and soluble markers related to endothelial function for 8 h. Meal A did not significantly increase plasma homocysteine and did not alter endothelial function markers. The amount of NO synthesized from meal arginine doubled after meal B (107.1 +/- 16.5% increase vs. meal A, P < 0.01) but was very low (271 +/- 84 ppm vs. 332 +/- 73 ppm, P < 0.05, respectively). After meal B, flow-mediated and nitroglycerine-induced dilation decreased but common carotid artery compliance, pulse wave velocity, plasma soluble intercellular adhesion molecule-1, and von Willebrand factor, and urinary cGMP did not differ when compared with meal A. Together, the data indicate that, in healthy men, meal amino acids do not adversely affect endothelial function, and meal arginine only slightly enters the NO pathway. Unexpectedly, arginine in physiological amounts may acutely lessen smooth muscle cell reactivity to a high dynamic NO release.

The metabolic effect of high-protein low-carbohydrate (HP) diets on body composition and glucose homeostasis remains incompletely understood. This study assesses the respective roles of the increased protein:carbohydrate ratio (P:C) and the resulting moderate decrease in energy intake in the metabolic effects of HP diets. Rats had free access to normal (NP; 14%) or high (HP; 53%) total milk protein isoenergetic diets, or were fed the NP diet but restricted to the energy intake of HP rats (NPr), which was 89.1 +/- 9.3% that of NP rats. After 8 wk, body weight was lower in HP and NPr rats than in NP rats. In HP rats, the lower body weight was associated with a lower adipose tissue mass and a reduced proportion of large adipocytes. HP rats also had an improved oral glucose tolerance and insulin sensitivity, as assessed by the homeostatic model assessment index, compared with NPr and NP rats, and these effects were related solely to the increased P:C. These data suggest that the reduced energy intake of rats fed a high-protein, low-carbohydrate diet explains the lower fat deposition but an increased P:C per se improves glucose homeostasis.

The aim of this work was to determine the effects in rats of ingesting 1 of 3 diets with normal or high protein concentrations and various carbohydrate:lipid ratios on weight gain, body composition, and the development and metabolism of white adipose tissue (WAT). For this purpose, male Wistar rats were fed for 20 or 42 d a high-carbohydrate, low-fat, normal-protein diet (76, 10, and 14% of energy as carbohydrate, lipid, and protein, respectively, carbohydrate:lipid ratio (C/L) = 7.6), a normal-carbohydrate, low-fat, high-protein diet (35, 10, and 55% of energy as carbohydrate, lipid, and protein respectively, C:L = 3.5), or a carbohydrate-free, high-fat, high-protein diet (45 and 55% of energy as fat and protein, respectively, C:L = 0). Growth, food intake, body composition, WAT cellularity, and several markers of lipogenesis including fatty acid synthase and lipoprotein lipase activities were measured in adipose tissue and liver. Lowering the C:L ratio reduced the development of WAT, weight gain, body fat mass, and adipocyte size, and in rats fed the carbohydrate-free diet (C:L = 0), the total number of adipocytes in subcutaneous WAT. These reductions in adipose tissue development with decreases in the C:L ratio of the diet seemed to be due primarily to reduced hepatic lipogenesis.

Dietary sulfur amino acids affect glutathione synthesis, but their acute effect under conditions of oxidative stress is unknown. We assessed the effect of the selective ingestion of alpha-lactalbumin, a cysteine-rich protein, on glutathione homeostasis before a single bout of exhaustive exercise. One hour before a 2-h run on a treadmill, untrained rats ingested a meal enriched with either milk protein (TMP), alpha-lactalbumin-enriched milk protein (alpha-LAC), glucose (GLUC) or milk protein plus 150 mg N-acetyl-L-cysteine, a pharmacologic cysteine donor (NAC). Glutathione status was monitored in the blood and measured postexercise in the liver and heart. A group of fed sedentary rats was used as a control (CON). Blood total glutathione levels declined over time in all test groups. Although postexercise heart glutathione did not differ among groups, postexercise liver glutathione was curvilinearly related to prior cysteine intake (R2=0.999, P<0.05). In alpha-LAC rats, liver glutathione was 60-80% higher than in GLUC or CON rats (P<0.05) and did not differ from that of NAC rats. Cysteine from dietary proteins exhibits a considerable, dose-dependent and acute stimulatory effect on liver glutathione during exercise but does not immediately benefit whole-body glutathione homeostasis, presumably because of an overlap between the postprandial and exercise-related states.

Omnivores show recognition of essential (indispensable) amino acid deficiency by changing their feeding behavior within 20 min, yet the cellular mechanisms of amino acid sensation in eukaryotes are poorly understood. The anterior piriform cortex (APC) of the brain in rats or its analog in birds likely houses the in vivo amino acid chemosensor. Because amino acid transporters adapt rapidly to essential amino acid deficiency in several cell models, we hypothesized that activation of electrogenic amino acid transport in APC neurons might contribute to the function of the amino acid sensor. We evaluated transport systems in primary cultures of neurons from the APC, hippocampus and cerebellum, or glia, incubated in complete or threonine-devoid (deficient) medium. After 10 min in deficient medium, uptake of threonine or a system A-selective substrate, methyl amino-isobutyric acid, was increased 60% in APC neurons only (P < 0.05). These results demonstrated upregulation of system A, an electrogenic amino acid-sodium symporter. This depletion-induced activation required sodium, intact intracellular trafficking, and phosphorylation of signal transduction-related kinases. Efflux studies showed that other transporter types were functional in the APC; they appeared to be altered dynamically in threonine-deficient cells in response to rapid increases in system A activity. The present data provided support for the chemical sensitivity of the APC and its role as the brain area housing the indispensable amino acid chemosensor. They also showed a region-specific, phosphorylation-dependent activation of the system A transporter in the brain in response to threonine deficiency.

The ontogenetic development of PepT1, NBAT and EAAC1 along the vertical and horizontal axes of the rat small intestine was evaluated using semiquantitative reverse transcriptase-polymerase chain reaction (RT-PCR) and immunohistochemistry. The proximodistal profiles of mRNA levels showed that PepT1 was evenly distributed, whereas NBAT had greater expression in the proximal part, and EAAC1 in the distal part. These regionalizations were the same from postnatal days 4 to 50. PepT1 and NBAT proteins were detected in the microvilli of enterocytes along the length of the villi. NBAT was also found in the cytoplasm. Surprisingly, EAAC1 was located exclusively in the microvilli of enterocytes in the crypt and the bases of the villi. These protein expression patterns were similar in all parts of the small intestine (proximal, median and distal), at all ages. We conclude that the expression of PepT1, NBAT or EAAC1 are differently regulated according to both the horizontal and vertical axes.

This study was designed to assess the effects of long-term adaptation to a high protein diet on energy intake, body weight gain, body composition and splanchnic metabolic indicators in rats. For this purpose, adult male Wistar rats were fed either a 50 g/100 g dry matter (DM) protein diet (P50 group) or a 14 g/100 g DM protein diet (P14 group) for 21 d. These two groups were compared with a P14 pair-fed (P14-pf) group that consumed the same daily energy as the P50 group. The energy intake of the P50 group was 16 +/- 1% less than that of the P14 group (P < 0.05), and the P50 group had significantly lower body weight. The P50 group had significantly less adipose tissue compared with both P14 and P14-pf rats. The activities of the brush border membrane enzymes, neutral aminopeptidase and gamma-glutamyl transferase, were significantly higher in the P50 group than in the P14 rats. Similarly, the activities of alanine aminotransferase, arginase and serine dehydratase were significantly higher in the liver of P50 rats compared with P14 rats. Both amino acid transporter system A and X(A,G-) activities, measured in freshly isolated hepatocytes, were significantly higher in the P50 group (8- and 1.5-fold, P < 0.05, respectively) compared with the P14 group. The 1.5-fold increase in the steady-state activity of X(A,G-) was accompanied by a doubling of EAAT2 mRNA, involved in the system X(A,G-). This study provides confirmation that specific biochemical and molecular adaptive processes of the splanchnic area are involved in the response to variations in the protein content of the diet.

The postprandial fixation of dietary nitrogen in splanchnic and peripheral tissues as well as its dynamic transfer to the nitrogen pools of the body were quantified in rats subjected to an acute augmentation of dietary protein. For this purpose, we traced the dietary protein and studied the immediate fate of exogenous nitrogen in many tissues and biological fluids. Rats were adapted to a diet providing an adequate protein level (14 g/100 g), and then fed a meal containing either 0.42 g (Group A) or 1.50 g (Group H) of [(15)N]-labeled milk protein. The amounts of exogenous nitrogen transferred to urea (0.32 +/- 0.04 vs. 2.46 +/- 0.25 mmol, respectively), incorporated in splanchnic (0.41 +/- 0.02 vs. 0.87 +/- 0.10 mmol) and peripheral (1.65 +/- 0.84 vs. 2.36 +/- 0.49 mmol) tissue protein were higher in group H than in group A. Individual plasma amino acids (AA) [(15)N]-enrichments showed that AA respond differentially to an acute augmentation of dietary intake. This work provides new descriptive and quantitative information on the metabolic fate of dietary nitrogen in the postprandial state. It highlights the higher integration of a surplus of dietary nitrogen in the tissues even if it is rapidly limited by saturation of the protein synthesis capacities. The main metabolic response remains the stimulation of AA degradation, leading to a large rise in urea production. However, both anabolic and catabolic systems are exceeded, resulting in an elevation of peripheral AA and negative feedback on the gastric emptying rate.

The purpose of this work was to determine exogenous and endogenous contributions to the overall nitrogen flux in the upper jejunum in humans. After the ingestion of water or 8 g of [15N]casein, the behavior of gastro-jejunal nitrogen and electrolyte (Na+, K+, Cl-) movements were studied in seven volunteers using the "slow marker" perfusion technique. The jejunal flow-rate of the chyme peaked during 0-20 min and 20-40 min periods following water and casein ingestion, respectively. Osmolarity, Cl- and Na+ concentrations decreased significantly (P < 0.05) during the first 20 min following meal ingestion and returned to the basal levels in the 20-60 min period. The gastric half-emptying times (min) of the liquid phase differed significantly (P < 0.05) for water (7.9 +/- 0.4) and casein (21.4 +/- 9.1). The basal flow rate of endogenous nitrogen was 9 +/- 3.3 mmol/h in the jejunum. After casein ingestion, the total nitrogen content reached maximum values in the 20-40 min period and then progressively returned to the initial level. The gastro-jejunal casein absorption was 58% and the remaining amount of casein in the jejunum was degraded more than 80% to alcohol-soluble compounds. After the ingestion of a low amount of casein no significant increase in the endogenous nitrogen fraction was observed. The 15N-dilution technique is an appropriate method in humans for the direct measurement of endogenous and exogenous contributions to the intestinal nitrogen fraction.