Effect of age and dietary protein level on ovine nitrogen metabolism—I. Evidence of comparable metabolizable nitrogen availability

Seven 8-month old and seven 9-yr old ewes were utilized to study the effects of age and dietary protein level on nitrogen and organic matter digestibilities and urinary and plasma nitrogenous constituents. Animals were fed individual maintenance levels, based on metabolic body size (W^0.75), of a diet containing 10% crude protein in trial 1 and isocaloric amounts of a diet containing 20% crude protein in trial 2. No age-related differences occurred in either trial for apparent digestible nitrogen (ADN) or organic matter. Nitrogen retention (g/kg W^0.75/day) was 0.09 ± 0.02 and 0.10 ± 0.01 in trial 1 and 0.09 ± 0.03 and 0.14 ± 0.03 in trial 2 for young and old ewes, respectively. Total urinary N as a percentage of ADN did not differ by age in either trial, and the relative proportions of urinary urea, ammonia-N and creatinine-N were comparable. Plasma urea and ammonia nitrogen were also similar for the two age groups in both trials. Asparagine, alanine, valine, leucine and total branched chain amino acids were significantly higher while arginine was lower in the plasma of young ewes in trial 1. In trial 2, glutamine, citrulline and arginine were significantly lower in the plasma of young ewes. Concentrations of essential, nonessential, branched and total amino acids were negatively correlated with protein retention in trial 1, while no significant correlations were observed in trial 2. These data suggest that in ewes of different ages fed at maintenance, availability of metabolizable nitrogen is comparable as indicated by no significant differences observed in digestion, absorption or excretion of nitrogen-containing metabolites measured in these studies. Thus, the differences seen in various plasma parameters reflect differences in metabolic processes due to age.     

Effect of age and dietary protein level on ovine nitrogen metabolism—II. Incorporation of [14C]valine into plasma proteins

Uptake from plasma and incorporation into plasma proteins of a pulse-dose of [¹⁴C]-valine were studied in 8-month and 9-yr old ewes fed corn-soy diets containing 9.6 and 19.9% crude protein in trials 1 and 2 respectively. Diets were fed at maintenance levels to 7 ewes of each age in each trial. In trial 1, total body plasma pool radioactivity of whole and deproteinized plasma decreased 68.6 and 98.9% in young ewes and 67.6 and 98.9% in old ewes over a 12 h period. In trial 2, decreases in radioactivity of these same pools were 55.1 and 98.6% for young ewes and 58.8 and 98.9% for old ewes. Total plasma protein (TPP) and globulin (G) concentrations were higher in old animals in both trials while albumin (A) concentrations were comparable. In trial 1, changes in radioactivity of A and G pools from 2 to 12 h after dosing were 19.4% decrease and 41.3% increase for young ewes and 11.0 and 33.6% increase for old ewes. In trial 2, A radioactivity decreased 25.8% and G increased 40.1% for old ewes. Old ewes tended to have greater radioactivity than young ewes in teh G fraction in both trials. Old ewes consistently had a larger percent of TPP radioactivity in the G and a lower percent in the A fraction in trial 2. It was concluded that higher dietary protein intake resulted in increase incorporation or radioactivity into plasma proteins, and that animal age seemed to affect plasma protein concentrations and likely rate of incorporation of radioactivity into plasma proteins.     

Urinary metabolites characteristic of urea-cycle amino acid deficiency

Experiments with 45–75-g male rats gave conclusive evidence that the simultaneous absence from the diet of arginine, ornithine, or citrulline caused an immediate and persistent elevation of orotic and citric acids in the urine. The experiments also demonstrated that a deficiency of no other individual amino acid increased urinary citrate and orotate. Elevated urinary excretion of orotic and citric acid occurred independently of the form of nonessential nitrogen. Replacement of arginine isonitrogenously with ornithine or citrulline prevented the rise in urinary orotic acid, but had different effects on growth, urinary citrate, and urinary urea. These differences were probably due to differential uptake of arginine, ornithine, and citrulline by tissues. In the reported experiments employing L-amino acids as sources of dietary nitrogen, a deficiency of any amino acid indispensable for growth and nitrogen balance or a deficiency of arginine, ornithine, or citrulline retarded growth, increased urinary urea, and decreased urinary ammonia. It is concluded that the severe loss of orotic acid during urea-cycle amino acid deficiency arises from a decreased capacity of the urea cycle to detoxify ammonia, thereby causing increased shunting of intramitochondrial carbamyl phosphate into pyrimidine synthesis. The similarities in metabolism during arginine deficiency and ammonia intoxication are discussed. The evidence shows that urinary orotic acid may be a valuable measure of arginine nutrition in mammals.     

Effect of different protein diets on the distribution of amino acids in plasma, liver and brain in the rat.

The distribution of amino acids between plasma, liver and brain was studied in adult male rats, fed a diet containing 8.7, 17 (control animals), 32 and 51% of protein during 15 days. The caloric intake was nearly equal in all groups. The highest food intake was observed in the animals on the low protein diet. Changes in plasma amino acids were variable. In contrast to the behavior of most amino acids in plasma, the branched chain amino acids were highest in the animals fed the 51% protein diet. Despite the low protein intake in the animals fed a 8.7% protein diet, the concentration of serine, glutamic acid, glutamine, glycine, alanine, methionine, isoleucine, leucine, phenylalanine and ornithine were significantly higher compared to control animals, whereas in those receiving a high protein diet, valine, leucine, tyrosine, tryptophan and histidine increased in relation to the increased protein and amino acid intake. The plasma amino acid patterns are not greatly influenced by the amino acid distribution in the food and the amount ingested. Alanine aminotransferase, aspartate aminotransferase, glutamate dehydrogenase and cholinesterase showed a two- to fivefold increased activity in the liver of animals consuming a high protein diet. In the brain, the concentration of valine, leucine, isoleucine, phenylalanine and tyrosine in animals receiving the low protein diet was higher than in controls and increased further with increasing protein content of the diet. Glutamine was increased in all dietary groups. The predicted influx of amino acids showed increasing influx rates in dependence of the plasma amino acid concentration. The entry of tyrosine and tryptophan and their brain concentration was inversely proportional to the protein content of the diet. In the present study which considers long-term adaptation to an increasing protein and amino acid intake in comparison to a balanced control protein diet, the levels of the indispensable amino acids were maintained within narrow limits in the brain and liver. The results indicate that inspite of a variable protein intake, the body tends to keep organ amino acids in relatively narrow limits favoring in this way amino acid homeostasis.     

Amino acid pattern in plasma before and after jejuno-ileal shunt operation for obesity.

The amino acid pattern in plasma was studied in a reference group (n=26) and in three groups of massive obese subjects (n=9, 8, and 9 respectively) before and at intervals after jejuno-ileostomy. The obese subjects had preoperatively an amino acid pattern significantly different from that in the reference group. The concentrations of lysine, tyrosine, 1/2 cystine, and glutamic acids were higher, and aspargin, glutamine, serine, and glycine were lower than in the reference group. During the post-operative period the amino acid pattern changed significantly; thus serine, glycine, and taurine increased and valine, lysine, leucine, tryptophan, thyrosine, 1/2 cystine, and citrulline decreased. The amino acid pattern in the obese group with the longest post-operative observation time and a stable body weight differed significantly from that in the reference group only with regard to a low valine concentration and high concentration of taurine and glutamatic acid.     

荷肝癌小鼠血浆和肿瘤组织游离氨基酸代谢变化及其与肿瘤体积相关性研究

目的探讨荷肝癌小鼠游离氨基酸代谢变化,为肝癌患者氨基酸失衡疗法提供理论依据。方法采用HITACHIL8800型氨基酸分析仪,检测10例荷肝癌小鼠血浆和肿瘤组织游离氨基酸,并以10例正常小鼠做为对照组,研究氨基酸代谢变化与肿瘤体积的关系。结果荷瘤组血浆游离精氨酸、缬氨酸、丝氨酸、谷氨酸明显降低;肿瘤组织游离蛋氨酸、精氨酸、缬氨酸、亮氨酸与对应血浆游离氨基酸呈负相关;肿瘤组织游离异亮氨酸、缬氨酸、蛋氨酸、酪氨酸、亮氨酸、谷氨酸、丝氨酸与肿瘤体积呈正相关。结论肝癌在其生长过程中与某些特定氨基酸关系密切,这将为针对肝癌的氨基酸失衡处理提供实验和理论依据。     

Amino Acid Concentrations in Plasma and Erythrocytes in Aregeneratory and Haemolytic Anaemias

The concentrations of unbound amino acids in erythrocytes and in plasma from 7 normal individuals, 11 patients with various types of aregeneratory anaemia, and 4 patients with hereditary haemolytic anaemias were determined on a Technicon Amino Acid Analyzer (Perry et al 1970). Most amino acids were normally found in higher concentrations in plasma than intracellularly. Cystine, methionine and tryptophan were almost exclusively present in plasma. Aspartic acid, however, was mainly found in erythrocytes, and glutathione only in erythrocytes. Glutamic acid and ornithine were more concentrated in the cells, while glycine and asparagine showed approximately the same concentrations in erythrocytes as in plasma. In the patients, plasma amino acids showed little deviations from normal, but in the erythrocytes there were striking changes. Erythrocyte glutamic acid concentrations were moderately to markedly elevated in all patients studied, and glycine concentrations in 13 out of 15 patients. In addition, the following amino acids were increased intracellularly in more than one patient: glutamine (8 patients), serine (7), asparagine (5), threonine (4), taurine (3), alanine (2), valine (2), ornithine (2), lysine (2), citrulline (2). Aspartic acid was decreased in erythrocytes from 4 patients with aregeneratory and 1 with haemolytic anaemia.     

Amino acid concentrations in plasma and erythrocytes in aregeneratory and haemolytic anaemias.

The concentrations of unbound amino acids in erythrocytes and in plasma from 7 normal individuals, 11 patients with various types of aregeneratory anaemia, and 4 patients with hereditary haemolytic anaemias were determined on a Technicon Amino Acid Analyzer (Perry et al 1970). Most amino acids were normally found in higher concentrations in plasma than intracellularly. Cystine, methionine and trypotophan were almost exclusively present in plasma. Aspartic acid, however, was mainly found in erythrocytes, and glutathione only in erythrocytes. Glutamic acid and ornithine were more concentrated in the cells, while glycine and asparagine showed approximately the same concentrations in erythrocytes as in plasma. In the patients, plasma amino acids showed little deviations from normal, but in the erythrocytes there were striking changes. Erythrocyte glutamic acid concentrations were moderately to markedly elevated in all patients studied, and glycine concentrations in 13 out of 15 patients. In addition, the following amino acids were increased intracellularly in more than one patient: glutamine (8 patients), serine (7), asparagine (5), threonine (4), taurine (3), alanine (2), valine (2), ornithine (2), lysine (2), citrulline (2). Aspartic acid was decreased in erythrocytes from 4 patients with aregeneratory and 1 with haemolytic anaemia.     

维持性血液透析患者血浆游离氨基酸检测的临床意义

目的　对维持血液透析患者的血浆游离氨基酸进行测定和分析。方法　用氨基酸自动分析仪测定 15例血透患者在一次透析前后的血浆氨基酸谱。结果　血透患者在透析前的必需氨基酸除苯丙氨酸外均较正常对照组降低 ,其中以缬氨酸、亮氨酸和组氨酸下降为显著 ;非必需氨基酸中精氨酸、甘氨酸和鸟氨酸明显升高 ;酪氨酸/苯丙氨酸和丝氨酸 /甘氨酸的比值较对照组明显降低。患者在一次透析后的必需和非必需氨基酸均低于透析前水平。结论　血透患者氨基酸异常的原因可能与蛋白质摄入不足、尿毒症毒性物质和酸中毒等有关     

Delayed plasma clearance of phenylalanine and tyrosine in elderly men

The plasma levels of 17 amino acids were measured in three groups of men: healthy young men, healthy elderly men, and demented tube-fed elderly men living in a nursing home, prior to, and again 2, 4, and 6 hours after the consumption of a standard protein-containing meal. The standard meal provided per kilogram of body weight 8.3 calories, 0.33 grams of protein, 0.90 grams of carbohydrate, and 0.37 grams of fat. The concentrations of all amino acids, except tryptophan, rose significantly at 2 hours and returned to baseline by 6 hours. Plasma phenylalanine and tyrosine were significantly (P less than 0.05) higher at 2 hours in the two groups of elderly men than in the young healthy men. In other respects the pre- and post-prandial amino acid profiles were not influenced by age. The ratio, tyrosine/other large neutral amino acids (tyr/LNAA), was significantly higher in both elderly groups than in the young men at nearly all time points before and after the test meal. It was generally higher in the demented older men than in the healthy older men. The data demonstrated a delayed plasma clearance of phenylalanine and tyrosine in old age. The elevated plasma tyr/LNAA ratio in the elderly men may have tended to augment an entry of tyrosine, the precursor of norepinephrine and dopamine, into their brains.     

Altered plasma free amino acid levels in obese traumatized man

Obesity is a major nutritional disorder that produces many abnormal metabolic responses. The effect of injury-induced stresses acting synergistically with the state of excessive body fat is not well known. Plasma levels of circulating free amino acids reflect the net status of protein breakdown and utilization. Hypoaminoacidemia is a common finding in severe injury and its significance in obese subjects was investigated. We measured in 10 obese (body mass index [BMI] greater than 30) and 10 non-obese (BMI less than 30) traumatized (Injury Severity Score [ISS] 17 to 50) patients, the plasma levels of free amino acids in the early "flow" phase of injury when subjects were receiving maintenance fluids without calories or nitrogen. Postabsorptive control samples were obtained from 10 obese and 10 non-obese volunteers. Obese controls showed an increase in valine, leucine, isoleucine, and glutamic acid levels, and a decrease in glycine, tryptophan, threonine, histidine, taurine, citrulline, and cystine levels compared with lean controls. Hypoaminoacidemia was equally seen in traumatized obese and non-obese patients, and it was mainly due to a 24% decrease in nonessential amino acids. Remarkably, essential amino acid levels were the same in all groups. Arginine and ornithine levels were significantly different in traumatized obese compared with non-obese patients. The hypoglycinemia seen in non-obese trauma patients was absent in obese patients. The changes in levels of sulphur-containing amino acids also suggest that monitoring of these levels should be included in the nutritional management of obese trauma patients.     

Amino acid profiles of young adults differ by sex,body mass index and insulin resistance

Background and aims

An increase in plasma branched-chain amino acids is associated with a higher risk of developing type 2 diabetes and cardiovascular diseases. However, little is known about the basal plasma amino acid concentrations in young adults. Our aim was to determine the plasma amino acid profiles of young adults and to evaluate how these profiles were modified by sex, body mass index (BMI) and insulin resistance (IR).

Plasma tryptophan and total neutral amino acid levels in men: influence of hyperinsulinemia and age

Because of the well-recognized age-related changes in peripheral tissue sensitivity to insulin and the demonstrated impact of insulin on blood amino acid profiles in young individuals, we evaluated the influence of insulin level and age on the concentrations of tryptophan and its ratio to the sum of the large neutral amino acids (LNAA). The ratio of the plasma concentrations of tryptophan and the LNAA (leucine, isoleucine, valine, tyrosine, and phenylalanine), may be an important determinant of the rate at which tissues synthesize neurotransmitters, such as catecholamines and serotonin. Each of five healthy young (21 to 34 yr) and five healthy old subjects (67 to 85 yr) received, on separate occasions, euglycemic insulin infusions at rates of 6, 10, 30, and 400 mU X m-2 X min-1. Basal plasma tryptophan concentrations and LNAA levels were similar in young and old. Both tryptophan and LNAA levels decreased in an insulin dose-dependent manner (P less than .02). The dose-response effect of insulin on tryptophan levels in the elderly was less than in the young (P less than .03), while the response of the LNAA was similar in both age groups. The ratio of tryptophan to LNAA was less in the old when compared to the young (P less than .03) but increased in the two age groups in an insulin-dose-dependent fashion (P less than .02). Maximal plasma tryptophan decrements were 39% and 32%, and maximal LNAA declines were 58% and 61% in young and old, respectively, during the 400 mU X m-2 X min-1 studies.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of essential and nonessential amino acids on gastric emptying in the dog.

Five dogs with gastric fistulas were studied to assess the effect on gastric emptying of two potent cholecystokinin (CCK) releasers (tryptophan and phenylalanine) and six other essential amino acids; the nonessential amino acids alanine, beta-alanine, arginine, asparagine, aspartic acid, citrulline, cysteine, cystine, glutamic acid, glutamine, D-glutamine, histidine, hydroxyproline, ornithine, proline, serine, tyrosine, and D-tryptophan; four peptide and amino acid preparations; and solutions of glucose, glycine, and mannitol. Of the essential amino acids, only tryptophan significantly slowed emptying and it was above 4 mM that there was a difference between control and test meal. The delay in response to tryptophan was dose-related and approached maximum at 40 mM; D-tryptophan had no effect at these concentrations. In concentrations up to 80 mM, none of the nonessential amino acids slowed emptying significantly. The four peptide and amino acid preparations in concentrations ranging from 80 to 700 milliosmoles had dose responses identical to those of D-glucose, glycine, and mannitol at similar osmolalities. It is concluded that L-tryptophan is a uniquely potent delayer of gastric emptying in the dog which is dose-dependent and stereospecific. Phenylalanine, a potent CCK releaser, did not slow emptying, which suggests that CCK release may not be the only mechanism by which tryptophan acts. The peptide and amino acid preparations (casein hydrolysate, Bacto-peptone, Amigen, FreAmine) seem to delay emptying by stimulation of osmoreceptors which is distinct from the mechanism of action of tryptophan.     

The effect of glucagon on free plasma amino acids in cirrhotics and healthy controls

The effect on free plasma amino acids before and after infusion of 1 mg glucagon was studied at rest after an overnight fast in seven patients with compensated liver cirrhosis and in seven healthy controls. Total aminoacidaemia in cirrhotic patients is significantly higher than in controls. Elevated basal levels in cirrhotics are found particularly in tyrosine, citrulline, tryptophane, threonine, phenylalanine, and methionine whereas ornithine and serine levels are decreased. Save for the redox couple cystine-cysteine which increases, glucagon elicits an decrease in most amino acids that is proportionate to their initial level. Total aminoacidaemia decreases in controls and cirrhotics by 14.6 and 9.1 per cent respectively. Serum ammonia level rises significantly in both groups, urea increases only in controls, uricaemia remains virtually unchanged.     

Ileal losses of nitrogen and amino acids in humans and their importance to the assessment of amino acid requirements

BACKGROUND & AIMS: Irreversible amino acid losses at the human ileum are not taken into account when tracer-derived amino acid requirements are calculated because the data available are scarce. We have investigated amino acid losses at the ileal level in humans after ingestion of a protein meal. METHODS: Thirteen volunteers ingested a single meal of 15N milk or soy proteins. The appearance of 15N and 15N amino acids in the ileal effluents collected using an ileal tube was monitored for 8 hours. RESULTS: In the soy group, higher losses of endogenous nitrogen, especially originating from amino acids, were observed, as well as a higher flow rate of dietary non-amino acid nitrogen. With soy protein, the digestibilities of valine, threonine, histidine, tyrosine, alanine, and proline were significantly lower than with milk. Ileal losses of leucine, valine, and isoleucine amounted to 12, 10, and 7 mg x kg(-1) x day(-1), respectively. Threonine ileal loss (9-12 mg x kg(-1) x day(-1)) was particularly high compared with the current amino acid requirement. CONCLUSIONS: Amino acid losses at the human terminal ileum are substantial and depend on the type of dietary protein ingested. Although it remains unclear whether intact amino acids are absorbed in the colon, we suggest that ileal losses should be considered an important component of amino acid requirements.     

Twenty-four-hour variations in rat blood and brain levels of the aromatic and branched-chain amino acids: chronic effects of dietary protein content

Groups of young adult, male rats were given free access for 12 weeks to a single diet containing either 12%, 24%, or 40% protein (dry weight). At the end of this time, six rats from each diet group were killed every four hours throughout a single 24-hour period, and blood samples and brains were obtained for quantitation of several of the large neutral amino acids (LNAAs). The blood level of each LNAA varied significantly as a function of time of day (tending to be lower during the day than at night) and as a function of dietary protein content (typically rising as protein intake increased). Except for tyrosine and valine, the serum concentration ratio of each LNAA to the sum of the other LNAA (previously reported to be a good predictor of the competitive uptake of each LNAA into brain) and the brain level of each LNAA showed unremarkable variations with time of day and dietary protein content. In contrast, the serum ratios and brain levels of tyrosine and valine did show notable variations at night as a function of dietary protein intake. Together, the results show that within a chronic physiologic range of protein intakes, the serum ratios and brain levels of several large neutral amino acids, particularly tryptophan, bear no relationship to dietary protein level. Though good correlations between these parameters and protein intake were obtained for valine and tyrosine, their physiologic/metabolic significance, if any, is unknown. In general, the data do not support the broad, unvalidated use of serum LNAA ratios in chronic settings as predictors of brain LNAA levels.     

Citrulline blood levels as indicators of residual intestinal absorption in patients with short bowel syndrome

Plasma citrulline is known to be a marker of absorptive enterocyte mass in humans. We evaluated whether citrulline and other blood amino acids are indicators of residual small intestinal length and therefore potential predictors of dependence on parenteral nutrition in the long term. We studied 25 patients with short bowel syndrome (SBS) after at least 18 months since last digestive circuit modification; 24 of them were again evaluated 1 year later. Ten patients were weaned off parenteral nutrition and 15 were dependent on parenteral nutrition. Fifty-four healthy volunteers (28 women and 26 men) served as controls. Amino acid levels were determined on serum with high-performance liquid chromatography (HPLC) as well as on blood and serum with tandem mass spectrometry analysis. Five amino acids (citrulline, leucine, isoleucine, valine and tyrosine) were significantly lower in all SBS patients than in controls, whereas glutamine, measured only by HPLC, was significantly higher. Nevertheless, only serum citrulline measured with HPLC was significantly related to small bowel length. We conclude that HPLC remains the reference methodology to evaluate blood or serum amino acid levels in adult population with SBS.     

Gastrectomized patients are in a state of chronic protein malnutrition analyses of 23 amino acids

BACKGROUND/AIMS: Malnutrition is one of the major postoperative complications of radical subtotal or total gastrectomy for gastric cancer. This study was conducted to clarify the nutritional consequences of radical gastrectomy with respect to protein metabolism. METHODOLOGY: To evaluate the nutritional status and the abnormalities in protein metabolism in such cases, serum concentrations of 23 amino acids were measured by high performance liquid chromatography in 40 patients who had undergone either subtotal (n = 20) or total (n = 20) gastrectomy more than 6 months prior to this analysis. RESULTS: Serum concentrations of total amino acids and nonessential amino acids were the same between gastrectomized patients and healthy controls (n = 50). However, concentrations of essential amino acids, essential amino acid/nonessential amino acid and branched-chain amino acid/total amino acid ratios were significantly lower in patient groups than in normal controls. Each essential amino acid was decreased and concentrations of glutamate and citrulline were increased in both patient groups compared with controls. The major differences between patients with subtotal and total gastrectomies included an increased ornithine and a decreased arginine concentration in patients with subtotal gastrectomy. CONCLUSIONS: These changes suggest that malabsorption of protein from the intestinal tract causes persistent proteolysis in the skeletal muscle for long periods of time after surgery in these patients and that changes in ornithine and citrulline levels may reflect more severe alterations in those with total gastrectomy.     

Protein tolerance to standard and high protein meals in patients with liver cirrhosis

AIM To investigate the plasma amino acid response and tolerance to normal or high protein meals in patients with cirrhosis.METHODS The plasma amino acid response to a 20 g mixed protein meal was compared in 8 biopsy-proven compensated cirrhotic patients and 6 healthy subjects.In addition the response to a high protein meal(1 g/kg body weight) was studied in 6 decompensated biopsy-proven cirrhotics in order to evaluate their protein tolerance and the likelihood of developing hepatic encephalopathy(HE) following a porto-caval shunt procedure.To test for covert HE,the "number connection test"(NCT) was done on all patients,and an electroencephalogram was recorded in patients considered to be at Child-Pugh C stage.RESULTS The changes in plasma amino acids after a 20 g protein meal were similar in healthy subjects and in cirrhotics except for a significantly greater increase(P 0.05) in isoleucine,leucine and tyrosine concentrations in the cirrhotics.The baseline branched chain amino acids/aromatic amino acids(BCAA/AAA) ratio was higher in the healthy persons and remained stable-but it decreased significantly after the meal in the cirrhotic group.After the high protein meal there was a marked increase in the levels of most amino acids,but only small changes occurred in the levels of taurine,citrulline,cysteine andhistidine.The BCAA/AAA ratio was significantly higher 180 and 240 min after the meal.Slightly elevated basal plasma ammonia levels showed no particular pattern.Overt HE was not observed in any patients.CONCLUSION Patients with stable liver disease tolerate natural mixed meals with a standard protein content.The response to a high protein meal in decompensated cirrhotics suggests accumulation of some amino acids but it did not precipitate HE.These results support current nutritional guidelines that recommend a protein intake of 1.2-1.5 g/kg body weight/day for patients with cirrhosis.