Protein Synthesis In Liver Research Articles

An Increase in Liver Polyamine Concentration Contributes to the Tryptophan-Induced Acute Stimulation of Rat Hepatic Protein Synthesis.

Tryptophan has a unique role as a nutritional signaling molecule that regulates protein synthesis in mouse and rat liver. However, the mechanism underlying the stimulating actions of tryptophan on hepatic protein synthesis remains unclear. Proteomic and metabolomic analyses were performed to identify candidate proteins and metabolites likely to play a role in the stimulation of protein synthesis by tryptophan. Overnight-fasted rats were orally administered L-tryptophan and then sacrificed 1 or 3 h after administration. Four differentially expressed protein spots were detected in rat liver at 3 h after tryptophan administration, of which one was identified as an ornithine aminotransferase (OAT) precursor. OAT is the main catabolic enzyme for ornithine, and its expression was significantly decreased by tryptophan administration. The concentration of ornithine was increased in the liver at 3 h after tryptophan administration. Ornithine is a precursor for polyamine biosynthesis. Significantly increased concentrations of polyamines were found in the liver at 3 h after administration of tryptophan. Additionally, enhanced hepatic protein synthesis was demonstrated by oral administration of putrescine. We speculate that the increase in ornithine level through suppression of OAT expression by tryptophan administration may lead to accelerated polyamine synthesis, thereby promoting protein synthesis in the liver.

Tissue-specific effect of colitis on protein synthesis in mice: impact of the dietary protein content

Inflammatory bowel diseases are associated with an increase in the whole-body protein turnover, thus possibly requiring an additional supply of dietary proteins. Our aim was to evaluate whether increasing dietary protein content could alleviate protein metabolism alterations in the injured splanchnic and peripheral tissues during colitis and spontaneous mucosal healing. Mice with acute chemically induced colitis received either a normal protein (P14, 14% as energy), a moderately (P30, 30%) and a very high-protein (P53, 55%) diets. At different times after the challenge, protein synthesis rate was determined in tissues using a flooding dose of 13C valine. Colon, liver and spleen protein synthesis rates were significantly increased after colitis induction, while being decreased in the caecum, kidneys and muscle. Contrastingly to the two other diets, P30 diet consumption allowed faster recovery of the animals, and this coincided with a rapid resaturation of the initial protein synthesis in the colon. In the other tissues studied, the high-protein diets show different effects depending on the dietary protein content consumed and on the examined tissues, with a general trend of P53 in lowering anabolism rates. This study highlights the severe impact of acute colonic inflammation on protein metabolism in different organs. In addition, dietary protein content modulated the recovery of the initial protein synthesis rate in the various tissues following colitis induction. P30 diet consumption notably showed a better ability to alleviate protein metabolism perturbations induced by colitis, that may explain its documented beneficial effect on colon mucosal healing.

Protein synthesizing function and the functional state of liver of rats for the continuous cadmium and lead load

The aim of the study was to investigate the effect of Cadmium and Lead on the protein synthesis and function of the rat liver. The experiments were conducted in male rats of the Wistar line, weighing 200–220 g, of which 4 groups of animals were formed: 1) a control group – injected drinking water through a metal probe in a volume equivalent to the volume of an aqueous solution of Cd2+ salts and Pb2+; 2) experimental group 1 – animals were administered a 0.029% aqueous solution of cadmium chloride at a dose of 4.0 mg/kg; 3) experimental group 2 – animals were administered 16.6% aqueous lead acetate solution at a dose of 200 mg/kg; 4) experimental group 3 – animals were administered 16.6% aqueous lead acetate solution at a dose of 100 mg/kg and 0.029% aqueous cadmium chloride solution at a dose of 2.0 mg/kg. Throughout the experiment, rats were kept in a balanced diet containing all the necessary components, and animals were given drinking water, without restriction, from 0.2 liter glass bowls. The functional state of the liver of rats under the conditions of use of salts of heavy metals was investigated by the activity of aminotransferases. In long-term lead-cadmium loading in rats of the experimental groups, the functional state of the liver is characterized, which is characterized by an increase in the permeability of biological membranes of the cell membranes, which causes hyperfermentemia in blood serum, in particular aminotransferase (AST, ALT). The high activity of ALT and AST in the serum of rats under the influence of Cadmium and Lead indicates the destructive processes in the liver that cause an increase in the output of aminotransaminases from cell organelles in the blood of experimental animals. Thus, the results obtained indicate an increase in the destructive processes in the body of rats under lead-cadmium loading. Important diagnostic value for intoxication of different etiology is the determination of protein synthesis of liver function. An important indicator of liver protein synthesis is the level of total protein and its fractions in the serum. This indicator reflects the changes that occur in the body in different pathological conditions. When loaded with heavy metals in the body of rats inhibits the protein synthesis function of the liver, which is manifested by a decrease in total blood protein and albumin levels.

Effect of experimental fascioliasis on the protein synthesis function of cow liver

The purpose of the work was to explore the indicators of functional state and function of protein synthesis of the cow liver within experimental fasciolysis, sensitized to atypical mycobacteria. Ten cows of black-and-white breed were selected for the experiments. Two groups consisting of five animals each were formed. The control group cows were clinically healthy. The animals of the experimental group were contaminated with mycobacteriosis and fascicular invasion. In the course of research, the rules for performing zootechnical experiments on the selection and maintenance of animal-analogues in the group, harvesting technology, use and accounting of consumed feed were followed. Being impacted by fascicular invasion, the cattle sensitized with mycobacteria demonstrated the suppression of the liver protein synthesis function, which manifests itself as a decrease in total blood protein, a decrease in the level of albumins and an increase in the level of globulins. According to the clinical manifestation of fasciolosis in the cattle sensitized with atypical mycobacteria, disease pathogens have a toxic effect on hepatocytes causing an increase in the permeability of the biological membranes of the cell membranes. The indicated changes lead to an increase in the activity of blood serum enzymes, in particular, aminotransferases (AsAT and AlAT) and alkaline phosphatase. High activity of AlAT and AsAT in the blood serum of the cows under experimental fasciolysis sensitized by atypical mycobacteria, indicates destructive processes in the liver that cause release of aminotransaminases from cellular organelles in the blood of the cattle. Thus, the results obtained indicate an increase in destructive processes in the body of the cows under experimental fascioliasis sensitized with atypical mycobacteria.

Hepatic protein synthesis and morphological parameters in blood of rats under oxidative stress and action of feed additive Butaselmevit-plus

The intensive development of animal husbandry at the present stage requires new approaches to organizing the feeding of farm animals and the introduction of modern feed additives, which are not normally used purely as feed, but are deliberately added to feed or water to improve their quality, increase productivity and animal welfare. To prevent the development of oxidative stress in animals, we used the feed additive "Butaselmevit-plus", which in its composition contains the fruits of milk thistle, selenium, methionine and vitamins A, E and D3. The aim of the study was to investigate the effect of feed additive Butaselmevit-plus on blood morphological parameters and protein synthesis of rat liver under tetrachloromethane poisoning. For research, we used Wistar male rats, which were divided into three groups of 20 animals each. Control rats were intact. The first and second experimental group of rats were administered tetrachloromethane. Experimental intoxication in animals was performed by twice (after 48 h) intragastric administration of tetrachloromethane at a dose of 0.1 ml per 100 g of rat body weight in the form of a 50% oil solution. Experimental group R2 was fed a feed additive of Butaselmevit-plus for a dose of 0.1 g per 100 g of body weight together with the feed for experimental toxicosis for 30 days. On the basis of the conducted researches positive effect of feed additive "Butaselmevit-plus" on the organism of rats, which were intoxicated with tetrachloromethane, is shown, which is shown by normalization of hematological parameters and protein synthesis of liver function. Restoration of hematopoietic function of bone marrow of rats by intoxication with tetrachloromethane is due to the fact that the feed additive "Butaselmevit-plus" contains in its composition fruits thistle, which have a high level of vitamins A and K, and trace elements, namely: Ferum, Cuprum and Cobalt that are directly involved in hematopoiesis. When feeding Butaselmevit-plus as feed supplement, the number of red blood cells in the blood of the second experimental group of rats was higher than that of the first experimental group, but the control values reached only on the 30th day of the experiment. When using the feed additive Butaselmevit-plus in rats under conditions of oxidative stress development, the leukocyte count decreased to the optimum level.

Glutathione Supplementation of Parenteral Nutrition Prevents Oxidative Stress and Sustains Protein Synthesis in Guinea Pig Model.

Peroxides contaminating parenteral nutrition (PN) limit the use of methionine as a precursor of cysteine. Thus, PN causes a cysteine deficiency, characterized by low levels of glutathione, the main molecule used in peroxide detoxification, and limited growth in individuals receiving long-term PN compared to the average population. We hypothesize that glutathione supplementation in PN can be used as a pro-cysteine that improves glutathione levels and protein synthesis and reduces oxidative stress caused by PN. One-month-old guinea pigs (7–8 per group) were used to compare glutathione-enriched to a non-enriched PN, animals on enteral nutrition were used as a reference. PN: Dextrose, amino acids (Primene), lipid emulsion (Intralipid), multivitamins, electrolytes; five-day infusion. Glutathione (GSH, GSSG, redox potential) and the incorporation of radioactive leucine into the protein fraction (protein synthesis index) were measured in the blood, lungs, liver, and gastrocnemius muscle. Data were analysed by ANOVA; p < 0.05 was considered significant. The addition of glutathione to PN prevented the PN-induced oxidative stress in the lungs and muscles and supported protein synthesis in liver and muscles. The results potentially support the recommendation to add glutathione to the PN and demonstrate that glutathione could act as a biologically available cysteine precursor.

P: 40 Potassium Deficiency Compromises Urea Synthesis and Markedly Increases Ammonia in Rats

BACKGROUND: Potassium deficiency decreases gene expression, synthesis of proteins, and growth in plants, bacteria, rodents and humans.1–4 The effect of hypokalemia on liver protein synthesis is scarcely described. Early studies have established an association between hypokalemia and development of hepatic encephalopathy in chronic liver disease.5,6 We investigated the effects of potassium deficiency on synthesis of liver proteins including urea cycle enzymes and the regulation of urea synthesis in rats. METHODS: Female Wistar rats were fed a K+-free diet for 13 days. Half of the rats were then repleted with K+ for one week following depletion. K+-depleted and -repleted rats were compared to free-fed and pair-fed controls. We examined the urea cycle enzyme mRNAs and proteins in liver tissue, the in vivo Capacity of Urea-Nitrogen Synthesis (CUNS) and plasma ammonia concentrations. Also, we measured hepatic albumin gene and protein expression, and potassium levels in plasma, liver, kidney and muscle tissues. RESULTS: The diet induced hypokalemia of 1.9 ± 0.4 mmol/L compared to pair-fed controls (3.6 ± 0.2 mmol/L). Muscle and kidney tissue potassium concentrations were decreased, but unchanged in liver tissue. Gene expression of albumin and two out of five urea cycle enzymes were moderately decreased, whereas protein expressions of albumin, the urea cycle enzymes, and glutamine synthetase were normal. However, CUNS was reduced by 33%. Plasma ammonia concentrations were eight-fold elevated to 235 (95% CI: 194–287) µmol/L compared to pair-fed controls 29 (95% CI: 26–32) µmol/L. Repletion of potassium normalized the changes. CONCLUSIONS: Hypokalemia markedly increased plasma ammonia concentrations. The capacity for urea synthesis was impaired, but only moderately so, and further studies are needed to fully explain the causes of hyperammonemia.

Redox balance and tissue development of juvenile Piaractus mesopotamicus subjected to high stocking density and fed dry diets containing nutraceutical food

Colostrum is a source of molecules with nutraceutical features that can attenuate the consequences of adverse conditions, such as densification. Thus, the redox balance and tissue development of juvenile Piaractus mesopotamicus subjected to high stocking density and fed diets containing lyophilized bovine colostrum (LBC) were evaluated. Juveniles were distributed into 16 cages making 50 kg fish m -3 and fed diets containing 0, 10, 20 and 30% inclusion of LBC (n = 4). After 30 days, enteric, hepatic, muscular, renal and branchial tissue were sampled for the determination of glutathione peroxidase (GPx), superoxide dismutase (SOD) and catalase activity, oxygen radical absorbance capacity (ORAC), lipid peroxidation and protein and nucleotides content. SOD activity and DNA content were higher in 20% LBC compared to the others in the enteric tissue ( P < 0.10). ORAC value in erythrocytes was higher in 30% LBC than 0 and 10% LBC ( P < 0.10). Juveniles fed 10% LBC showed higher lipid peroxidation in liver than 0 and 20% LBC ( P < 0.10) and those fed 20% LBC showed lower protein/RNA ratio compared to the others ( P < 0.10). Bovine colostrum determined a decrease in liver protein synthesis and increased in intestinal DNA content with an intake of 20% of this milk secretion. Additionally, LBC increased the protection of the enteric tissue of juveniles from superoxide radicals and blood antioxidant capacity. We conclude that bovine colostrum can be used as a nutraceutical food for fish, with positive effect in redox balance and tissue development in high concentrations of inclusion in the diet, 20 and 30%.

Tumour-specific and organ-specific protein synthesis rates in patients with pancreatic cancer.

BackgroundLiving tissues maintain a fine balance between protein synthesis and protein breakdown rates. Animal studies indicate that protein synthesis rates are higher in organs when compared with skeletal muscle tissue. As such, organ and tumour protein synthesis could have major effects on whole‐body protein metabolism in wasting disorders such as cancer cachexia. We aimed to assess protein synthesis rates in pancreatic tumour tissue and healthy pancreas, liver, and skeletal muscle tissue in vivo in humans.MethodsIn eight patients with pancreatic cancer undergoing pancreaticoduodenectomy, primed continuous infusions with L‐[ring‐13C6]phenylalanine and L‐[3,5‐2H2]tyrosine were started prior to surgery and continued throughout the surgical procedures. During surgery, plasma samples and biopsies from the pancreas, pancreatic tumour, liver, and vastus lateralis muscle were taken. Post‐absorptive fractional protein synthesis rates were determined by measuring incorporation of labelled L‐[ring‐13C6]phenylalanine in tissue protein using the weighed plasma L‐[ring‐13C6]phenylalanine enrichments as the precursor pool.ResultsFive male patients and three female patients with a mean age of 67 ± 2 years were included into this study. Plasma L‐[ring‐13C6]phenylalanine enrichments (6–9 mole per cent excess) did not change during surgery (P = 0.60). Pancreatic tumour protein synthesis rates were 2.6‐fold lower than surrounding pancreatic tissue protein synthesis rates (0.268 ± 0.053 vs. 0.694 ± 0.228%/h, respectively; P = 0.028) and 1.7‐fold lower than liver protein synthesis rates (0.268 ± 0.053 vs. 0.448 ± 0.043%/h, respectively; P = 0.046). Among healthy organ samples, protein synthesis rates were 20‐fold and 13‐fold higher in pancreas and liver, respectively, compared with skeletal muscle tissue (0.694 ± 0.228 and 0.448 ± 0.043 vs. 0.035 ± 0.005%/h, respectively; P < 0.05).ConclusionsLiver and pancreas tissue protein synthesis rates are higher when compared with pancreatic tumour and skeletal muscle tissue protein synthesis rates and can, therefore, strongly impact whole‐body protein metabolism in vivo in humans.

Effect of tannins and cellulase on growth performance, nutrients digestibility, blood profiles, intestinal morphology and carcass characteristics in Hu sheep.

ObjectiveThis study was conducted to evaluate the effects of tannins and cellulase on growth performance, nutrient digestibility, blood profiles, intestinal morphology, and carcass characteristics in Hu sheep.MethodsA total of 48 three-month-old meat Hu sheep (25.05±0.9 kg) were blocked based on body weight, and randomly allotted to 4 treatments with 3 replicates of 4 sheep each. The experiment lasted for 80 d, and dietary treatments were as follows: i) CON, control diet; ii) TAN, CON+0.1% tannins; iii) CEL, CON+0.1% cellulase; iv) TAN+CEL, CON+0.1% tannins and 0.1% cellulase.ResultsCompared with CON, CEL, and TAN+CEL had greater (p<0.05) final body weight (FBW) and average daily gain but lower (p<0.05) feed conversion ratio, while FBW of TAN+ CEL was lower (p<0.05) than that of CEL. The apparent total tract digestibility (ATTD) of dry matter in TAN, CEL, and TAN+CEL groups were higher (p<0.05) than that in CON. CEL and TAN+CEL groups had greater (p<0.05) ATTD of crude fiber compared with TAN and CON, while TAN group had lower (p<0.05) ATTD of crude protein than other treatments. TAN, CEL, and TAN+CEL groups increased (p<0.05) serum globulin and alkaline phosphatase but decreased (p<0.05) albumin/globulin. Serum total protein was greatest for TAN+CEL, intermediate for TAN and CEL and least for CON (p<0.05). TAN+CEL group increased (p<0.05) dressing percentage compared with CON, while the backfat thickness of CEL was lower (p<0.05) than that of CON. The villus height of jejunum and ileum in CEL and TAN+CEL groups were greater (p<0.05) than that in CON, and the crypt depth and villus height: crypt depth of jejunum were increased (p<0.05) in TAN, CEL, and TAN+CEL groups.ConclusionThe addition of tannins and cellulase together promoted nutrient digestion, liver protein synthesis and intestinal development and thus improved growth performance and carcass characteristics.

English

One of the attributes of amino acid lysine is to manufacture muscle protein, as it is a physiologically essential amino acid for immunity, development and production in birds. This study evaluates the influence of several levels of the essential amino acid lysine for chicks, with age of about 504 hours, maintained at a temperature of approximately 29 degrees Celsius. The basal diet contained 21.0% crude protein and 3,000 kcal of energy of biological transformations/kg. This formula was supplemented with levorotatory-lysine acid monohydrochloride, resulting in diets with 1.040 to 1.280% of total lysine for five experimental treatments. The treatments were found to have a mathematical expression squared influence on animals’ weight gain, conversion of diet, total liver mass and protein synthesis index. The effect of the five experimental treatments was not observed in diet consumption, fat synthesis index, absolute weights of intestines and heart, and percentage of liver mass. It was concluded that the total lysine requirements for chicks aged up to 504 h were 1.240%. Key words: Thermal environment, dietary lysine, growth performance, rearing setting.

Effects of mustard oil cake on liver proteins of Channa punctatus (Bloch).

Mustard oil cake is a biofertilizer widely used in agriculture and fish cultivation almost in all South East Asian Countries including India. The study was carried out to observe the effects of this biofertilizer on the liver proteins of Channa punctatus. At sublethal concentration (0.42 g/L ), fishes were exposed for a prolonged period of 35 days and amount of total liver protein (TLP) was measured. The investigation showed a low rate of liver protein synthesis in treated fish after 4 days of exposure. An increase in the amount of protein was observed between the 7th and 35th day. But such increment was below the amount of TLP of control fish, indicating physiological stress in the treated fish.

A moderately high level of dietary lipid inhibited the protein secretion function of liver in juvenile tiger puffer Takifugu rubripes

Tiger puffer have a unique lipid storage pattern. They store lipid predominantly in liver. To investigate the hepatic physiology of tiger puffer in response to a moderately high level of dietary lipid, a 74-day feeding trial was conducted, followed by a hepatic transcriptome assay. Two experimental diets which had an optimal (10.44%, Control) or moderately higher (14.64%, high-lipid diet, HL) dietary lipid level was formulated. Each diet was fed to triplicate tanks. No significant difference was observed in growth and feed efficiency between the two groups, but the survival was significantly lower in group HL. The HL diet also resulted in significantly higher lipid accumulation in liver, which was reflected in the hepatic histology. The biochemical parameters in serum confirmed the existence of stress in liver caused by high lipid intake. A total of 63 differentially expressed genes between groups were observed in the hepatic transcriptome assay, which were primarily enriched in Gene Ontology (GO) terms such as Endopeptidase activity, Secretion, and Organic acid transport, as well as in Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways such as Protein processing in endoplasmic reticulum and DNA replication. The HL diet tended to inhibit the protein synthesis and secretion in liver, and this was evidenced by activities/concentrations of selected proteins secreted into intestine. Genes related to liver protection and repair were transcriptionally stimulated by diet HL. In conclusion, compared to the optimal lipid requirement, a moderately higher lipid level in the diet for tiger puffer did not compromise the growth performance, but tended to inhibit the protein secretion function of liver and stimulate the processes related to liver protection and repair. The present results will be beneficial to both feed management in tiger puffer farming and elucidation of lipid metabolism characteristics in fish which store lipid in liver.

Effects of feed intake restriction during late pregnancy on the function, anti-oxidation capability and acute phase protein synthesis of ovine liver.

ObjectiveAn experiment was conducted to investigate the effects of feed intake restriction during late pregnancy on the function, anti-oxidation capability and acute phase protein synthesis of ovine liver.MethodsEighteen time-mated ewes with singleton fetuses were allocated to three groups: restricted group 1 (RG1, 0.18 MJ ME/kg W0.75 d, n = 6), restricted group 2 (RG2, 0.33 MJ ME/kg W0.75 d), n = 6) and a control group (CG, ad libitum, 0.67 MJ ME/kg W0.75 d, n = 6). The feed restriction period was from 90 days to 140 days of pregnancy.ResultsThe ewe’s body weight, liver weights, water, and protein content of liver in the restricted groups were reduced compared with the CG group (p<0.05), but the liver fat contents in the RG1 group were higher than those of the CG group (p<0.05). The increased hepatic collagen fibers and reticular fibers were observed in the restricted groups with the reduction of energy intake. The concentrations of nonesterified free fatty acids in the RG1 and RG2 groups were higher than those of the CG group with the reduction of energy intake (p<0.05), but there were decreased concentrations of lipoprotein lipase and hepatic lipase in both restricted groups compared with the CG group (p<0.05). In addition, the increased concentrations of β-hydroxybutyric acid, triglycerides, malondialdehyde, total antioxidant capacity and activities of superoxide dismutase activity and catalase were found in the RG1 group, and the concentrations of cholinesterase in the RG1 group were reduced compared with the CG group (p<0.05). For the concentrations of acute phase proteins, the C-reactive protein (CRP) in the RG1 group were reduced compared with the CG group, but there were no differences in haptoglobin relative to the controls (p>0.05).ConclusionThe fat accumulation, increased hepatic fibrosis, antioxidant imbalance and modified synthesis of acute phase proteins were induced in ewe’s liver by maternal malnutrition during late pregnancy, which were detrimental for liver function to accommodate pregnancy.

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

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

Impact of 3-week citrulline supplementation on postprandial protein metabolism in malnourished older patients: The Ciproage randomized controlled trial

Citrulline (CIT), is not extracted by the splanchnic area, can stimulate muscle protein synthesis and could potentially find clinical applications in conditions involving low amino acid (AA) intake, such as in malnourished older subjects. Our purpose was to research the effects of CIT supplementation on protein metabolism in particular on non-oxidative leucine disposal (NOLD, primary endpoint), and splanchnic extraction of amino acids in malnourished older patients. This prospective randomized multicenter study determined whole-body and liver protein synthesis, splanchnic protein metabolism and appendicular skeletal muscle mass (ASMM) in 24 malnourished older patients [80-92 years; 18 women and 6 men] in inpatient rehabilitation units. All received an oral dose of 10g of CIT or an equimolar mixture of six non-essential amino acids (NEAAs), as isonitrogenous placebo, for 3 weeks. NOLD and albumin fractional synthesis rates were not different between the NEAA and CIT groups. Splanchnic extraction of dietary amino acid tended to decrease (p=0.09) in the CIT group (45.2%) compared with the NEAA group (60.3%). Total differences in AA and NEAA area under the curves between fed-state and postabsorptive-state were significantly higher in the CIT than in the NEAA group. There were no significant differences for body mass index, fat mass (FM), lean mass (LM) or ASMM in the whole population except for a tendential decrease in FM for the citrulline group (p=0.089). Compared with Day 1, lean mass and ASMM significantly increased (respectively p=0.016 and p=0.018) at Day 20 in CIT-treated women (mean respective increase of 1.7kg and 1.1kg), and fat mass significantly decreased (p=0.001) at Day 20 in CIT-group women (mean decrease of 1.3kg). Our results demonstrate that CIT supplementation has no effect on whole-body protein synthesis or liver protein synthesis in malnourished older subjects. However, CIT supplementation was associated with a higher systemic AA availability. In the subgroup of women, CIT supplementation increased LM and ASMM, and decreased FM.

Creatine supplementation to total parenteral nutrition improves creatine status and supports greater liver and kidney protein synthesis in neonatal piglets.

BackgroundCreatine is not included in commercial pediatric parenteral products; the entire creatine requirement must be met by de novo synthesis from arginine during parenteral nutrition (PN). Poor arginine status is common during PN in neonates, which may compromise creatine accretion. We hypothesized that creatine supplementation will improve creatine status and spare arginine in PN-fed piglets.MethodsPiglets (3-5-day (d) old) were provided PN with or without creatine for 14 d. Tissue concentrations of creatine metabolites and activities of creatine-synthesizing enzymes, as well as tissue protein synthesis rates and liver lipid parameters, were measured.ResultsCreatine provision lowered kidney and pancreas L-arginine:glycine amidinotransferase (AGAT, EC number 2.1.4.1) activities and plasma guanidinoacetic acid (GAA) concentration, suggesting the downregulation of de novo creatine synthesis. Creatine increased plasma creatine concentrations to sow-fed reference levels and increased the creatine concentrations in most tissues, but not in the brain. PN creatine resulted in greater protein synthesis in the liver and the kidney, but not in the pancreas, skeletal muscle, or gut. Creatine supplementation also reduced liver cholesterol concentrations, but not triglyceride or total fat.ConclusionThe addition of creatine to PN may optimize the accretion of creatine and reduce the metabolic burden of creatine synthesis in rapidly growing neonates.

Short-term changes in diet composition do not affect in vivo hepatic protein synthesis in rats.

Protein synthesis is critical to protein homeostasis (proteostasis), and modifications in protein synthesis influence lifespan and the development of comorbidities associated with obesity. In the present study, we examined the acute response of liver protein synthesis to either high-fat or high-sucrose diets in order to elucidate nutrient-mediated regulation of hepatic protein synthesis in the absence of body fat accumulation. Total and endoplasmic reticulum-associated protein syntheses were assessed by use of the stable isotope, deuterium oxide (2H2O), in rats provided a control diet or diets enriched in polyunsaturated fat, saturated fat, or sucrose for 2, 4, or 7 days. The three experimental diets increased hepatic triglycerides 46-91% on day 7 and fasting insulin levels 83-117% on day 7, but did not result in differences in body weight when compared with control ( n = 6/diet/time). The fraction of newly synthesized proteins in total liver lysates and microsomes was not significantly different among dietary groups ( n = 3/diet/time). To determine whether the experimental diets provoked a transcriptional response to enhance the capacity for protein synthesis, we also measured a panel of genes linked to amino acid transport, synthesis, and processing. There were no significant differences in any of the genes measured among groups. Therefore, dietary treatments that have been linked to impaired proteostasis and that promote hepatic steatosis and insulin resistance, did not result in significant changes in total or ER-associated protein synthesis in the liver over a 7-day period.

Dietary Methionine Restriction Regulates Liver Protein Synthesis and Gene Expression Independently of Eukaryotic Initiation Factor 2 Phosphorylation in Mice

Background: The phosphorylation of eukaryotic initiation factor 2 (p-eIF2) during dietary amino acid insufficiency reduces protein synthesis and alters gene expression via the integrated stress response (ISR).Objective: We explored whether a Met-restricted (MR) diet activates the ISR to reduce body fat and regulate protein balance.Methods: Male and female mice aged 3-6 mo with either whole-body deletion of general control nonderepressible 2 (Gcn2) or liver-specific deletion of protein kinase R-like endoplasmic reticulum kinase (Perk) alongside wild-type or floxed control mice were fed an obesogenic diet sufficient in Met (0.86%) or an MR (0.12% Met) diet for ≤5 wk. Ala enrichment with deuterium was measured to calculate protein synthesis rates. The guanine nucleotide exchange factor activity of eIF2B was measured alongside p-eIF2 and hepatic mRNA expression levels at 2 d and 5 wk. Metabolic phenotyping was conducted at 4 wk, and body composition was measured throughout. Results were evaluated with the use of ANOVA (P < 0.05).Results: Feeding an MR diet for 2 d did not increase hepatic p-eIF2 or reduce eIF2B activity in wild-type or Gcn2-/- mice, yet many genes transcriptionally regulated by the ISR were altered in both strains in the same direction and amplitude. Feeding an MR diet for 5 wk increased p-eIF2 and reduced eIF2B activity in wild-type but not Gcn2-/- mice, yet ISR-regulated genes altered in both strains similarly. Furthermore, the MR diet reduced mixed and cytosolic but not mitochondrial protein synthesis in both the liver and skeletal muscle regardless of Gcn2 status. Despite the similarities between strains, the MR diet did not increase energy expenditure or reduce body fat in Gcn2-/- mice. Finally, feeding the MR diet to mice with Perk deleted in the liver increased hepatic p-eIF2 and altered body composition similar to floxed controls.Conclusions: Hepatic activation of the ISR resulting from an MR diet does not require p-eIF2. Gcn2 status influences body fat loss but not protein balance when Met is restricted.

Dietary Leucine Supplementation Alters Muscle and Liver Protein Synthesis during Immune System Stimulation in Pigs

IntroductionImmune system stimulation (ISS) adversely affects protein and amino acid (AA) metabolism, leading to a decrease in skeletal muscle protein synthesis and increases in muscle protein degradation and visceral protein synthesis. While such short‐term changes in protein metabolism are beneficial for supporting an immune response, prolonged alterations are undesirable as it negatively affects whole‐body protein deposition (PD) and body weight gain. Among essential AA, Leu has a regulatory role in protein turnover in skeletal muscle and other tissues through its effect on the mechanistic target of rapamycin complex 1 signalling pathway. However, ISS may produce a short‐term resistance to Leu in skeletal muscle that impairs the anabolic effects of this AA.ObjectiveThe objective of this study was to evaluate the effects of ISS and dietary Leu supplementation on plasma AA and urea concentrations, and protein synthesis of various tissues during ISS.MethodsYorkshire pigs (initial body weight [BW] = 10.6 ± 1.1 kg) were surgically fitted with indwelling jugular vein catheters and assigned to one of three diets: 1. CON, 1.36% standardized ileal digestible (SID) Leu; 2. LEU‐M, 2.04% SID Leu; and 3. LEU‐H, 2.72% SID Leu. Immune system stimulation was induced in all LEU‐M and LEU‐H pigs and half of CON pigs with lipopolysaccharide (ISS+; n = 7, 8, and 7 for CON, LEU‐M, and LEU‐H, respectively); the remaining CON pigs were administered saline (ISS‐; n = 6). During ISS, feed allowance of ISS− and ISS+ pigs was equivalent. Blood was collected every 12 h at 0, 12, 24, and 36‐h after ISS was induced for determining plasma AA and urea concentrations. At 36 h, FSR of liver, plasma, gastrocnemius, and longissimus dorsi (LD) proteins were determined with a flooding dose of L‐[ring‐2H5]‐Phe.ResultsWhole‐body PD was decreased in ISS+ pigs (P &lt; 0.01). Plasma AA and urea concentrations in ISS− pigs were constant over time, whereas they were increased in ISS+ pigs 12 h after ISS despite similar AA intake between ISS− and ISS+ pigs (P &lt; 0.05). Plasma AA and urea concentrations at 36 h were similar between ISS− and ISS+ pigs except Phe (P = 0.053) and Thr (P = 0.054), which tended to decrease in ISS− pigs, and Gln (P = 0.072), which tended to increase in ISS+ pigs. Although dietary Leu supplementation increased plasma Leu concentration prior to ISS (Linear; P &lt; 0.01), there was no linear effect at 36 h in ISS+ pigs. Dietary Leu supplementation decreased plasma Gln, Ile, and Val and urea concentrations at 36 h in ISS+ pigs (Linear; P &lt; 0.05). Liver protein FSR was increased in ISS+ pigs (P &lt; 0.05), whereas plasma and skeletal muscle protein FSR was not affected by ISS. Dietary Leu supplementation tended to decrease liver protein FSR (Linear; P = 0.052) and increase gastrocnemius protein FSR (Linear; P = 0.085) in ISS+ pigs, but there was no linear effect on LD protein FSR.ConclusionsIn this study, ISS resulted in acute increases in plasma AA and urea concentrations that reflect changes in tissue AA and protein metabolism. Skeletal muscle anabolic resistance to Leu was likely transient since protein synthesis rates were not reduced in gastrocnemius and LD muscles after ISS. However, the reduction in liver protein synthesis and increase in gastrocnemius protein synthesis in response to dietary Leu supplementation may facilitate AA partitioning for muscle PD during ISS.Support or Funding InformationNSERC 400994, OMAFRA 030087