Dietary intake of sulfur amino acids and risk of kwashiorkor malnutrition in eastern Democratic Republic of the Congo.

BACKGROUND: Kwashiorkor is an often-fatal type of severe acute malnutrition affecting hundreds of thousands of children annually, but whose etiology is still unknown. Evidence suggests inadequate sulfur amino acid (SAA) status may explain many signs of the condition but studies evaluating dietary protein intake in relation to the genesis of kwashiorkor have been conflicting. We know of no studies of kwashiorkor that have measured dietary SAAs. OBJECTIVES: We aimed to determine whether children in a population previously determined to have high prevalence of kwashiorkor [high-prevalence population (HPP)] have lower dietary intakes of SAAs than children in a low-prevalence population (LPP). METHODS: A cross-sectional census survey design of 358 children compared 2 previously identified adjacent populations of children 36-59 mo old in North Kivu Province of the Democratic Republic of the Congo. Data collected included urinary thiocyanate (SCN), cyanogens in cassava-based food products, recent history of illness, and a 24-h quantitative diet recall for the child. RESULTS: The HPP and LPP had kwashiorkor prevalence of 4.5% and 1.7%, respectively. A total of 170 children from 141 households in the LPP and 169 children from 138 households in the HPP completed the study. A higher proportion of HPP children had measurable urinary SCN (44.8% compared with 29.4%, P < 0.01). LPP children were less likely to have been ill recently (26.8% compared with 13.6%, P < 0.01). Median [IQR] intake of SAAs was 32.4 [22.9-49.3] mg/kg for the LPP and 29.6 [18.1-44.3] mg/kg for the HPP (P < 0.05). Methionine was the first limiting amino acid in both populations, with the highest risk of inadequate intake found among HPP children (35.1% compared with 23.6%, P < 0.05). CONCLUSIONS: Children in a population with a higher prevalence of kwashiorkor have lower dietary intake of SAAs than children in a population with a lower prevalence. Trial interventions to reduce incidence of kwashiorkor should consider increasing SAA intake, paying particular attention to methionine.

Protease em dietas com baixa proteína contendo farinha de Penas para codornas de corte / [Protease in low-protein diets for meat-type quails containing feather meal]

Objetivou-se avaliar a suplementação de protease em dietas com baixa proteína contendo farinha de penas (FP) sobre o desempenho e o rendimento de carcaça de codornas de corte. Foram utilizadas 240 codornas, machos, distribuídas em delineamento inteiramente ao acaso, em esquema fatorial 2x 3 (com e sem protease x 3 níveis de FP (0%, 5% e 10%)), totalizando seis tratamentos (dieta reduzida (DR) em 8% da exigência de proteína bruta e aminoácidos + 0% FP; DR + 5% FP; DR + 10% FP; DR + 0% FP + protease; DR + 5% FP + protease e DR + 10% FP + protease), quatro repetições de 10 codornas por parcela, nas fases de oito-21 dias e oito-35 dias de idade. Observou-se interação (P≤0,05) entre os níveis de FP e protease no ganho de peso de oito-21 dias. Os níveis de FP influenciaram (P≤0,05) o consumo de ração e o ganho de peso de oito-21 e oito-35 e a conversão alimentar de oito-21 dias. Verificou-se interação (P≤0,05) entre aprotease e a inclusão de FPpara o peso corporalaos 35 dias. Conclui-se que aFP pode ser utilizada em até 5% em dietas para codornas de corte semsuplementação comprotease.(AU)

The objective of this study was to evaluate protease supplementation in low-protein diets containing feather meal (FP) on the performance and carcass yield of meat-type quails. Twenty male quails were used in a completely randomized design, in a 2 x 3 factorial scheme (with and without protease x 3 FP levels (0, 5 and 10%)), totaling six treatments (Reduced diet (RD) in 8 % of the requirement of crude protein and amino acids + 0% FP; RD + 5% FP; RD + 10% FP; RD + 0% FP + protease; RD + 5% FP + protease and RD + 10% FP + protease), four replicates of 10 quails per plot, in the phases of 8-21 days and 8-35 days of age. Interaction (P≤0.05) was observed between FP and protease levels on weight gain over the period of 8-21 days. The levels of FP influenced (P≤0.05) the feed intake and the weight gain of 8-21 and 8-35 and the feed conversion ratio of 8-21 days. There was interaction (P≤0.05) between protease supplementation and FP inclusion for body weight at 35 days. It is concluded that FP can be used up to 5% in diets for meat-type quails without protease supplementation.(AU)

Influence of low-protein diet with different levels of amino acids on laying hen performance, quality and egg composition.

The present study aimed to investigate the consequences of dietary levels of crude protein (CP) and total sulfur amino acids (TSAA, Met+Cys) on productive performance, egg quality and egg components for Lohmann Brown laying hens through 18-34 weeks of age. A 2×3 factorial design experiment was conducted using two levels of CP (16 and 18 %) and three levels of Met+ Cys (0.67, 0.72 and 0.77 %). A total of 144 Lohmann Brown laying hens at 18 weeks of age were randomly divided into 6 treatment groups. The best values of final body weight and body weight change were recorded by the hens fed 18 % CP diet. Increasing dietary CP up to 18 % accompanied with the best (P> 0.01) feed conversion, egg weight and egg mass. The combination between low-CP diet (16 %) and 0.72 % Met+ Cys gave the best percentage of egg production. The majority of egg quality traits were not significantly altered by dietary treatments. The interaction between CP and Met+Cys levels had a statistical (P>0.01) impact on egg content of moisture and total solids only. It could be concluded that the best production criteria could be obtained by using 0.72% Met+Cys. Moreover, dietary level of 16 or 18 % CP with 0.72% Met+Cys is recommended for feeding Lohmann hens.

Supplementation of Sulfur-Containing Amino Acids or Essential Amino Acids Does Not Reverse the Hepatic Lipid-Lowering Effect of a Protein-Rich Insect Meal in Obese Zucker Rats.

The present study tested the hypothesis that the liver lipid-lowering effect of insect meal (IM) is caused by its low methionine concentration. A total of fifty, male obese Zucker rats were randomly assigned to five groups of 10 rats each (casein (C), IM, IM + Met, IM + Cys, and IM + EAA). While group C received a diet with casein, the IM-fed groups received a diet with IM as the protein source. In groups IM + Met, IM + Cys and IM + EAA, the diets were additionally supplemented with methionine, cysteine and essential amino acids (EAA), respectively. Hepatic concentrations of triacylglycerols and cholesterol, and hepatic mRNA levels and activities of lipogenic and cholesterogenic enzymes were markedly lower in the IM-fed groups than in group C (p < 0.05). All of these parameters either did not differ across the IM-fed groups or were only slightly higher in groups IM + Met, IM + Cys and IM+EAA than in the group IM. In conclusion, the results indicate that a difference in the amino acid composition between IM and casein, a low concentration of methionine in IM and a reduced cysteine synthesis secondary to a decreased methionine availability resulting from feeding IM are not causative for the lipid-lowering effect of IM.

Substitution of Dietary Sulfur Amino Acids by dl-2-Hydroxy-4-Methylthiobutyric Acid Reduces Fractional Glutathione Synthesis in Weaned Piglets.

BACKGROUND: Cys is limiting for reduced glutathione (GSH) synthesis and can be synthesized from Met. We hypothesized that the dietary Met hydroxyl analogue dl-2-hydroxy-4-methylthiobutyric acid (dl-HMTBA) affects Cys and GSH metabolism and oxidative stress defense differently than Met. OBJECTIVE: The objective was to elucidate whether dl-HMTBA supplementation of a Met-deficient diet affects Cys flux, GSH fractional synthetic rate (FSR), and the basal oxidative stress level relative to Met supplementation in pigs. METHODS: Twenty-nine male German Landrace piglets aged 28 d were allocated to 3 dietary groups: a basal diet limiting in Met (69% of Met plus Cys requirement) supplemented with either 0.15% l-Met (LMET; n = 9), 0.15% dl-Met (DLMET; n = 11), or 0.17% dl-HMTBA (DLHMTBA; n = 9) on an equimolar basis. At age 54 d the pigs received a continuous infusion of [1-13C]-Cys to calculate Cys flux and Cys oxidation. After 3 d, GSH FSR was determined by [2,2-2H2]-glycine infusion, and RBC GSH and oxidized GSH concentrations were measured. At age 62 d the animals were killed to determine hepatic mRNA abundances of enzymes involved in GSH metabolism, GSH concentrations, and plasma oxidative stress defense markers. RESULTS: The Cys oxidation was 21-39% and Cys flux 5-15% higher in the fed relative to the feed-deprived state (P < 0.001). On average, GSH FSR was 49% lower (P < 0.01), and RBC GSH and total GSH concentrations were 12% and 9% lower, respectively, in DLHMTBA and DLMET relative to LMET pigs (P < 0.05). In the feed-deprived state, Gly flux, the GSH:oxidized glutathione (GSSG) ratio, RBC GSSG concentrations, plasma oxidative stress markers, and the hepatic GSH content did not differ between groups. CONCLUSIONS: Although GSH FSR was higher in LMET compared with DLMET or DLHMTBA feed-deprived pigs, these differences were not reflected by lower oxidative stress markers and antioxidant defense enzymes in LMET pigs.

Changes in cecum microbial community in response to total sulfur amino acid (TSAA: DL-methionine) in antibiotic-free and supplemented poultry birds.

The effect of essential total sulfur amino acids (TSAA) like methionine and cysteine on the cecal microbiome of broilers was investigated at 2 different time points (days 21 and 42) of broiler rearing. A total of 360-day-old Cobb male broiler chicks were randomly distributed to 6 dietary treatments in a 2 × 3 factorial arrangement, with 2 levels of antibiotic growth promoters (AGP: 0 and 0.05%) and 3 levels of TSAA (DL-methionine) either for starter (0.7, 0.8, and 0.9%) or finisher chicks (0.52, 0.62, and 0.72%), labeled as diets 1 to 6. Cecal digesta from each replicate (n = 10) were sampled on days 21 and 42. DNA was extracted for the amplification of the V4 region of bacterial 16S rRNA genes and subjected to Illumina sequencing. Bioinformatic analyses were performed using QIIME, Mothur, and ad hoc tools and functional profiles of the inferred metagenome were analyzed using PICRUST. Statistical difference was determined by 2-way ANOVA and PERMANOVA. Clustering of cecal communities using PCoA showed clear separation of microbial communities based on age (P < 0.05) of birds and between low and medium/ high levels of TSAA (DL-methionine). At day 21, bacterial richness and diversity were higher than at day 42 where Clostridium cluster XI and Lactobacillus were found most abundant. No variability in taxonomic richness at the genus level was observed with AGP and DL-methionine supplementation. Interbird variation for richness was greater at day 42 compared to day 21. The mean fold difference of richness was greater (1.5 mean fold) with diets 1 and 6, suggesting interactive effects of AGP and TSAA (DL-methionine) in the diet. KEGG function profiles calculated by PICRUST suggest that the cecal microbiome increased glycolysis and energy generation correlated with increased dietary TSAA (DL-methionine) supplementation levels during the late broiler growth period (day 42). This study increases our knowledge of microbial dynamics and functions that are relevant to host nutrition and performance that may help us tailoring alternative strategies for raising poultry birds under antibiotic-free conditions.

Estimation of the standardized ileal digestible lysine requirement and optimal sulphur amino acids to lysine ratio for 30-50 kg pigs.

Two experiments were conducted to determine the standardized ileal digestible (SID) lysine (Lys) requirement and the ideal SID sulphur amino acids (SAA) to Lys ratio for 30-50 kg crossbred pigs. In experiment 1, a total of 72 crossbred pigs with an average initial body weight (BW) of 28.9 kg were allotted to one of six dietary treatments in a randomized complete block design. Each diet was assigned to six pens containing two pigs each. Six diets were obtained by supplementing graded levels of L-Lysine∙HCl to create six dietary levels of SID Lys (0.70%, 0.80%, 0.90%, 1.00%, 1.10% and 1.20%). Responses of weight gain (ADG) and gain:feed (G:F) to increasing the SID Lys content of the diet fitted well with the curvilinear-plateau model; whereas, for plasma urea nitrogen (PUN) two-slope linear broken-line model was well fitted. The optimal SID Lys requirement for the pigs of this period was 1.10%. Experiment 2 was a dose-response study using SID Met+Cys to Lys ratios of 50%, 55%, 60%, 65%, 70% and 64%. A total of 72 crossbred pigs with initial BW of 32.9 kg were randomly allotted to receive one of the six diets. Diets 1-5 were formulated to contain 1.0% SID Lys to be second limiting in Lys and diet 6 contained 1.11% SID Lys to be adequate in Lys. The average optimal SID SAA:Lys ratio for maximal ADG and G:F and minimal PUN was 65.2% using curvilinear-plateau and linear broken-line models.

Combining Dietary Sulfur Amino Acid Restriction with Polyunsaturated Fatty Acid Intake in Humans: A Randomized Controlled Pilot Trial.

Dietary and plasma total cysteine (tCys) have been associated with adiposity, possibly through interaction with stearoyl⁻CoA desaturase (SCD), which is an enzyme that is involved in fatty acid and energy metabolism. We evaluated the effect of a dietary intervention with low cysteine and methionine and high polyunsaturated fatty acids (PUFAs) on plasma and urinary sulfur amino acids and SCD activity indices. Fourteen normal-weight healthy subjects were randomized to a seven-day diet low in cysteine and methionine and high in PUFAs (Cys/Metlow + PUFA), or high in saturated fatty acids (SFA), cysteine, and methionine (Cys/Methigh + SFA). Compared with the Cys/Methigh + SFA group, plasma methionine and cystathionine decreased (p-values < 0.05), whereas cystine tended to increase (p = 0.06) in the Cys/Metlow + PUFA group. Plasma total cysteine (tCys) was not significantly different between the groups. Urinary cysteine and taurine decreased in the Cys/Metlow + PUFA group compared with the Cys/Methigh + SFA group (p-values < 0.05). Plasma SCD-activity indices were not different between the groups, but the change in cystine correlated with the SCD-16 index in the Cys/Metlow + PUFA group. A diet low in methionine and cysteine decreased plasma methionine and urinary cysteine and taurine. Plasma tCys was unchanged, suggesting that compensatory mechanisms are activated during methionine and cysteine restriction to maintain plasma tCys.

Dietary sulfur amino acids affect jejunal cell proliferation and functions by affecting antioxidant capacity, Wnt/ß-catenin, and the mechanistic target of rapamycin signaling pathways in weaning piglets.

Intestinal epithelial cells undergo rapid renewal along the crypt-villus axis (CVA), which ensures intestinal functions. Weaning stress differentially effects intestinal epithelial cell metabolism and physiological states along the CVA. Sulfur amino acids (SAA) play a key role in intestinal epithelial cell functioning. This study evaluated the effects of SAA dietary supplementation on weaning pig jejunal epithelial cells along the CVA. Sixteen Duroc × Landrace × Yorkshire piglets (6.16 ± 0.22 kg BW) were weaned at 21 d of age and were blocked by BW and gender and the randomly assigned to 1 of 2 groups fed diets consisting of low (0.53%) or high (0.85%) levels of SAA for a 7-d period. All piglets were euthanized for tissue sampling on day 7 postweaning. Jejunal epithelial cells were isolated along the CVA to yield 3 "cell fractions" (upper villus, middle villus, and crypt cells). The number of proliferating cells per crypt of piglets fed the high SAA diet was lower (P < 0.05) than that for low SAA diet. High SAA diet piglets tended to have decreased (P = 0.059) sucrase activities compared low SAA diet piglets. A high SAA diet increased (P < 0.05) total antioxidant capacity, catalase, and superoxide dismutase activities compared with a low SAA diet. mRNA expression levels of claudin-1, Slc5a1, and Slc7a9 in high SAA diet piglets were lower (P < 0.05) than for low SAA diet piglets. There were no interactions between dietary SAA and cell sections along the CVA for enzyme activities and mRNA expression in any of the weaned piglets. Protein amounts and phosphorylation levels related to Wnt/ß-catenin and mechanistic targeting of rapamycin (mTOR) signaling pathways were affected by SAA in weaning piglets. These findings indicate that dietary SAA affects jejunal cell proliferation and functions in weaning piglets. There appears to be no interactions between dietary SAA and cell sections along the CVA. The effects of SAA may be partly through affecting antioxidant capacity, and Wnt/ß-catenin and mTOR signaling pathway.

Disease prevention and delayed aging by dietary sulfur amino acid restriction: translational implications.

Sulfur amino acids (SAAs) play numerous critical roles in metabolism and overall health maintenance. Preclinical studies have demonstrated that SAA-restricted diets have many beneficial effects, including extending life span and preventing the development of a variety of diseases. Dietary sulfur amino acid restriction (SAAR) is characterized by chronic restrictions of methionine and cysteine but not calories and is associated with reductions in body weight, adiposity and oxidative stress, and metabolic changes in adipose tissue and liver resulting in enhanced insulin sensitivity and energy expenditure. SAAR-induced changes in blood biomarkers include reductions in insulin, insulin-like growth factor-1, glucose, and leptin and increases in adiponectin and fibroblast growth factor 21. On the basis of these preclinical data, SAAR may also have similar benefits in humans. While little is known of the translational significance of SAAR, its potential feasibility in humans is supported by findings of its effectiveness in rodents, even when initiated in adult animals. To date, there have been no controlled feeding studies of SAAR in humans; however, there have been numerous relevant epidemiologic and disease-based clinical investigations reported. Here, we summarize observations from these clinical investigations to provide insight into the potential effectiveness of SAAR for humans.

Sulfur amino acid restriction-induced changes in redox-sensitive proteins are associated with slow protein synthesis rates.

The mechanisms underlying life span extension by sulfur amino acid restriction (SAAR) are unclear. Cysteine and methionine are essential for the biosynthesis of proteins and glutathione (GSH), a major redox buffer in the endoplasmic reticulum (ER). We hypothesized that SAAR alters protein synthesis by modulating the redox milieu. Male F344-rats were fed control (CD: 0.86% methionine without cysteine) and SAAR diets (0.17% methionine without cysteine) for 12 weeks. Growth rates, food intake, cysteine and GSH levels, proteins associated with redox status and translation, and fractional protein synthesis rates (FSRs) were determined in liver. Despite a 40% higher food intake, growth rates for SAAR rats were 27% of those fed CD. Hepatic free cysteine in SAAR rats was 55% compared with CD rats. SAAR altered tissue distribution of GSH, as hepatic and erythrocytic levels were 56% and 196% of those in CD rats. Lower GSH levels did not induce ER stress (i.e., unchanged expression of Xbp1s , Chop, and Grp78), but activated PERK and its substrates eIF2-α and NRF2. SAAR-induced changes in translation-initiation machinery (higher p-eIF2-α and 4E-BP1, and lower eIF4G-1) resulted in slower protein synthesis rates (53% of CD). Proteins involved in the antioxidant response (NRF2, KEAP1, GCLM, and NQO1) and protein folding (PDI and ERO1-α) were increased in SAAR. Lower FSR and efficient protein folding might be improving proteostasis in SAAR.

Lessons from animal nutritionists: dietary amino acid requirement studies and considerations for healthy aging studies.

Dietary restriction (DR) increases median life span and protects against age-related disease. Improved longevity can be achieved by restriction of dietary energy, protein, or amino acids (AAs), such as methionine (Met). Met requirements have been defined using methodologies that measure the dose response to Met when all other dietary variables are held constant and with outcomes focused on protein turnover. Here, we cover protein and sulfur AA requirements and discuss the terms "deficient," "optimal," and "excess" and how these need to be considered. We additionally discuss the effect of methyl-donating compounds on sulfur AA metabolism and outcomes. We will discuss how the mechanistic target of rapamycin complex 1 (mTORC1) signaling network regulates protein turnover, lipogenesis and cell growth, proliferation, differentiation, and metabolism in response to hormones, AAs, and cellular energy status. Inhibition of mTORC1 signaling with rapamycin or genetic mutation increases median life span in model organisms, and mTORC1 inhibition may be responsible for some of the life span-extending effects of DR. Finally, we discuss how the sulfur AAs may regulate aspects of reactive oxygen species (ROS) mitigation. Overall, we suggest that approaches evaluating AA intake need to consider whole-body protein synthesis and measures related to tissue-specific and whole-body metabolism that have been associated with longevity.

Total Sulfur Amino Acid Requirements Are Not Altered in Children with Chronic Renal Insufficiency, but Minimum Methionine Needs Are Increased.

Background: The total sulfur amino acid (TSAA) and minimum Met requirements have been previously determined in healthy children. TSAA metabolism is altered in kidney disease. Whether TSAA requirements are altered in children with chronic renal insufficiency (CRI) is unknown.Objective: We sought to determine the TSAA (Met in the absence of Cys) requirements and minimum Met (in the presence of excess Cys) requirements in children with CRI.Methods: Five children (4 boys, 1 girl) aged 10 ± 2.6 y with CRI were randomly assigned to receive graded intakes of Met (0, 5, 10, 15, 25, and 35 mg · kg-1 · d-1) with no Cys in the diet. Four of the children (3 boys, 1 girl) were then randomly assigned to receive graded dietary intakes of Met (0, 2.5, 5, 7.5, 10, and 15 mg · kg-1 · d-1) with 21 mg · kg-1 · d-1 Cys. The mean TSAA and minimum Met requirements were determined by measuring the oxidation of l-[1-13C]Phe to 13CO2 (F13CO2). A 2-phase linear-regression crossover analysis of the F13CO2 data identified a breakpoint at minimal F13CO2 Urine samples collected from all study days and from previous studies of healthy children were measured for sulfur metabolites.Results: The mean and population-safe (upper 95% CI) intakes of TSAA and minimum Met in children with CRI were determined to be 12.6 and 15.9 mg · kg-1 · d-1 and 7.3 and 10.9 mg · kg-1 · d-1, respectively. In healthy school-aged children the mean and upper 95% CI intakes of TSAA and minimum Met were determined to be 12.9 and 17.2 mg · kg-1 · d-1 and 5.8 and 7.3 mg · kg-1 · d-1, respectively. A comparison of the minimum Met requirements between healthy children and children with CRI indicated significant (P < 0.05) differences.Conclusion: These results suggest that children with CRI have a similar mean and population-safe TSAA to that of healthy children, suggesting adequate Cys synthesis via transsulfuration, but higher minimum Met requirement, suggesting reduced remethylation rates.

Autophagy Modulation by Lanthionine Ketimine Ethyl Ester Improves Long-Term Outcome after Central Fluid Percussion Injury in the Mouse.

Diffuse axonal injury is recognized as a progressive and long-term consequence of traumatic brain injury. Axonal injury can have sustained negative consequences on neuronal functions such as anterograde and retrograde transport and cellular processes such as autophagy that depend on cytoarchitecture and axon integrity. These changes can lead to somatic atrophy and an inability to repair and promote plasticity. Obstruction of the autophagic process has been noted after brain injury, and rapamycin, a drug used to stimulate autophagy, has demonstrated positive effects in brain injury models. The optimization of drugs to promote beneficial autophagy without negative side effects could be used to attenuate traumatic brain injury and promote improved outcome. Lanthionine ketimine ethyl ester, a bioavailable derivative of a natural sulfur amino acid metabolite, has demonstrated effects on autophagy both in vitro and in vivo. Thirty minutes after a moderate central fluid percussion injury and throughout the survival period, lanthionine ketimine ethyl ester was administered, and mice were subsequently evaluated for learning and memory impairments and biochemical and histological changes over a 5-week period. Lanthionine ketimine ethyl ester, which we have shown previously to modulate autophagy markers and alleviate pathology and slow cognitive decline in the 3 × TgAD mouse model, spared cognition and pathology after central fluid percussion injury through a mechanism involving autophagy modulation.

Splanchnic tissues respond differently when piglets are offered a diet 30 % deficient in total sulfur amino acid for 10 days.

PURPOSE: A deficient total sulfur amino acid (TSAA) supply has been reported to differently affect the amino acid composition of tissues, but limited information is available about its effects on the morphology and metabolic properties of splanchnic tissues. METHODS: The amino acid composition, protein metabolism, glutathione concentration of the liver, proximal and distal jejunum, ileum and kidneys, and intestinal architecture were compared in 42-day-old piglets pair-fed either a diet deficient (TSAA-; 28 % deficiency) or sufficient (TSAA+) in TSAA for 10 days. RESULTS: The supply of TSAA had no effect on tissue weights, but influenced the amino acid composition in a tissue-dependent manner. Compared with animals receiving diet TSAA+, the concentrations of Met and Ser were higher in liver protein of TSAA- animals while the Cys concentration in protein was lower in the liver but higher in the distal jejunum. The TSAA supply had no effect on protein synthesis and proteolytic activities of tissues. Villus width and surface, and crypt surface were lower in the proximal jejunum of TSAA- versus TSAA+ pigs. Crypt surface in the ileum of TSAA- pigs was higher. Pigs receiving diet TSAA- had lower GSH and GSSG concentrations in the liver and proximal jejunum, but the GSH/GSSG ratio was decreased only in the liver. CONCLUSIONS: A greater nutritional priority appears to be given to splanchnic tissues so that its growth and protein metabolism can be maintained when the TSAA supply is limiting. The amino acid composition, glutathione status, and intestinal mucosa architecture are affected in a tissue-dependent manner.

Skeletal muscles respond differently when piglets are offered a diet 30% deficient in total sulfur amino acid for 10 days.

PURPOSE: Although amino acids (AA) are required for growth, little is known about the effect of a deficient AA supply on the composition and the contractile and metabolic properties of skeletal muscles. METHODS: Protein metabolism, oxidative catabolism, glutathione system, and fiber-type composition of the longissimus (LM), rhomboideus (RM), and semitendinous (SM) muscles were compared between 42-day-old piglets pair-fed for 10 days either with a diet with a 28% deficient supply of total sulfur AA (TSAA-) or with a diet with a sufficient supply of total sulfur AA (TSAA+). RESULTS: The relative weight, protein mass, and protein synthesis of LM were 10-32% lower in TSAA- pigs compared with TSAA+ pigs, while RM and SM were not affected by the TSAA supply. The TSAA supply affected the AA composition of muscles. Concentrations of Met and branched-chain AA were, respectively, 7 and 3% lower in TSAA- pigs compared with TSAA+ pigs. The His concentration was 30% higher in LM and SM in TSAA- pigs compared with TSAA+ pigs and unaffected in RM. The activity of citrate synthase was 14% higher in all three muscles of TSAA- pigs. In these pigs, the ß-hydroxy-acyl-CoA dehydrogenase activity was 20% higher in RM compared with TSAA+ pigs while that of lactate dehydrogenase was 21% lower in LM. Total and reduced glutathione concentrations were more than 70% greater in RM than in LM or SM, and these concentrations were approximately 10% lower in TSAA- pigs than in TSAA+ pigs. CONCLUSIONS: Results of this study indicate that a TSAA deficiency affects muscle properties in a muscle-dependent manner increasing the oxidative capacity of RM and reducing growth and glycolytic metabolism of LM.

Macroporous chitosan hydrogels: Effects of sulfur on the loading and release behaviour of amino acid-based compounds.

Chitosan is a biodegradable, biocompatible polymer of natural origin widely applied to the preparation of functional hydrogels suitable for controlled release of drugs, peptides and proteins. Non-covalent interactions, expecially ionic interactions, are the main driver of the loading and release behaviour of amino acids or peptides from chitosan hydrogels. With the aim to improve the understanding of the mechanisms governing the behaviour of chitosan hydrogels on peptide uptake and delivery, in this paper the attention was focused on the role played by sulfur on the interactions of chitosan hydrogels with sulfur-containing amino acids (AA) and peptides. Hence, loading and release experiments on cysteine, cystine and glutathione (SH containing amino acid, dipeptide and tripeptide, respectively) as well as on glycine and valine as apolar amino acids were carried out. For these puroses, chitosan hydrogels were prepared in an easy and reproducible manner by a freeze-gelation process on a poly-L-lysine coated support. The hydrogel surface pore size, uniformity and distribution were tested. Optimal results (D50 = 26 ± 4 µm) were obtained by using the poly-L-lysine positively-charged surface. The loading results gathered evidenced that the sulfur-containing molecules presented an increased absorption both in terms of rate and extent by chitosan hydrogels with respect to nonpolar amino acids, mainly due to ionic and hydrogen bond interactions. ATR-FTIR analysis carried out on chitosan hydrogels, with and without the AA related compounds to study putative interactions, supported these apparent sulfur-dependent results. Finally, chitosan hydrogels displayed excellent retention capabilities (AA release <5%) for all AA, strongly supporting the use of chitosan hydrogels as matrix for controlled drug release.

The role of the renal ammonia transporter Rhcg in metabolic responses to dietary protein.

High dietary protein imposes a metabolic acid load requiring excretion and buffering by the kidney. Impaired acid excretion in CKD, with potential metabolic acidosis, may contribute to the progression of CKD. Here, we investigated the renal adaptive response of acid excretory pathways in mice to high-protein diets containing normal or low amounts of acid-producing sulfur amino acids (SAA) and examined how this adaption requires the RhCG ammonia transporter. Diets rich in SAA stimulated expression of enzymes and transporters involved in mediating NH4 (+) reabsorption in the thick ascending limb of the loop of Henle. The SAA-rich diet increased diuresis paralleled by downregulation of aquaporin-2 (AQP2) water channels. The absence of Rhcg transiently reduced NH4 (+) excretion, stimulated the ammoniagenic pathway more strongly, and further enhanced diuresis by exacerbating the downregulation of the Na(+)/K(+)/2Cl(-) cotransporter (NKCC2) and AQP2, with less phosphorylation of AQP2 at serine 256. The high protein acid load affected bone turnover, as indicated by higher Ca(2+) and deoxypyridinoline excretion, phenomena exaggerated in the absence of Rhcg. In animals receiving a high-protein diet with low SAA content, the kidney excreted alkaline urine, with low levels of NH4 (+) and no change in bone metabolism. Thus, the acid load associated with high-protein diets causes a concerted response of various nephron segments to excrete acid, mostly in the form of NH4 (+), that requires Rhcg. Furthermore, bone metabolism is altered by a high-protein acidogenic diet, presumably to buffer the acid load.

Sulfur amino acid-free diet results in increased glutamate in human midbrain: a pilot magnetic resonance spectroscopic study.

OBJECTIVE: This pilot study was designed to determine if metabolic effects in different brain regions (left and right parietal lobes, midbrain) caused by 3 d of food consumption without methionine or cysteine could be detected by proton magnetic resonance spectroscopy. METHODS: Healthy individuals 18 to 36 y old (n = 8) were studied by magnetic resonance spectroscopy after receiving a diet with adequate sulfur amino acids (SAAs) or with zero SAA for 3 d. Pulse sequences were used to selectively measure glutathione (GSH), and linear combination modeling of spectra was used to measure other high-abundance brain metabolites and expressed relative to creatine (Cr). RESULTS: Although dietary SAAs are required to maintain GSH, the 3-d SAA insufficiency resulted in no significant change in GSH/Cr in the three brain regions. Principal component analysis of 16 metabolites measured by linear combination modeling showed that the metabolic pattern in the midbrain, but not in the parietal lobes, was distinguished according to the dietary SAAs. Multivariate statistical analysis showed that the major discriminating factors were signals of glutamate/Cr, (glutamate + glutamine)/Cr, and myoinositol/Cr. Correlation analyses between midbrain metabolites and GSH-related metabolites in plasma showed that midbrain glutamate/Cr had an inverse correlation with plasma cystine. CONCLUSION: The data show that magnetic resonance spectroscopy is a non-invasive tool suitable for nutritional assessment and suggest that nutritional imbalance caused by 3 d of SAA-free food more selectively affects the midbrain than the parietal lobes.

A sulfur amino acid-free meal increases plasma lipids in humans.

The content of sulfur amino acid (SAA) in a meal affects postprandial plasma cysteine concentrations and the redox potential of cysteine/cystine. Because such changes can affect enzyme, transporter, and receptor activities, meal content of SAA could have unrecognized effects on metabolism during the postprandial period. This pilot study used proton NMR ((1)H-NMR) spectroscopy of human plasma to test the hypothesis that dietary SAA content changes macronutrient metabolism. Healthy participants (18-36 y, 5 males and 3 females) were equilibrated for 3 d to adequate SAA, fed chemically defined meals without SAA for 5 d (depletion), and then fed isoenergetic, isonitrogenous meals containing 56 mg·kg(-1)·d(-1) SAA for 4.5 d (repletion). On the first and last day of consuming the chemically defined meals, a morning meal containing 60% of the daily food intake was given and plasma samples were collected over an 8-h postprandial time course for characterization of metabolic changes by (1)H-NMR spectroscopy. SAA-free food increased peak intensity in the plasma (1)H-NMR spectra in the postprandial period. Orthogonal signal correction/partial least squares-discriminant analysis showed changes in signals associated with lipids, some amino acids, and lactate, with notable increases in plasma lipid signals (TG, unsaturated lipid, cholesterol). Conventional lipid analyses confirmed higher plasma TG and showed an increase in plasma concentration of the lipoprotein lipase inhibitor, apoC-III. The results show that plasma (1)H-NMR spectra can provide useful macronutrient profiling following a meal challenge protocol and that a single meal with imbalanced SAA content alters postprandial lipid metabolism.