Plasma Essential Amino Acids Research Articles

Exercise in ZDF rats does not attenuate weight gain, but prevents hyperglycemia concurrent with modulation of amino acid metabolism and AKT/mTOR activation in skeletal muscle.

Protein metabolism is altered in obesity, accompanied by elevated plasma amino acids (AA). Previously, we showed that exercise delayed progression to type 2 diabetes in obese ZDF rats with maintenance of β cell function and reduction in hyperglucocorticoidemia. We hypothesized that exercise would correct the abnormalities we found in circulating AA and other indices of skeletal muscle protein metabolism. Male obese prediabetic ZDF rats (7-10/group) were exercised (swimming) 1 h/day, 5 days/week from ages 6-19 weeks, and compared with age-matched obese sedentary and lean ZDF rats. Food intake and weight gain were unaffected. Protein metabolism was altered in obese rats as evidenced by increased plasma concentrations of essential AA, and increased muscle phosphorylation (ph) of Akt(ser473) (187%), mTOR(ser2448) (140%), eIF4E-binding protein 1 (4E-BP1) (111%), and decreased formation of 4E-BP1*eIF4E complex (75%, 0.01 ≤ p ≤ 0.05 for all measures) in obese relative to lean rats. Exercise attenuated the increase in plasma essential AA concentrations and muscle Akt and mTOR phosphorylation. Exercise did not modify phosphorylation of S6K1, S6, and 4E-BP1, nor the formation of 4E-BP1*eIF4E complex, mRNA levels of ubiquitin or the ubiquitin ligase MAFbx. Positive correlations were observed between ph-Akt and fed circulating branched-chain AA (r = 0.56, p = 0.008), postprandial glucose (r = 0.42, p = 0.04) and glucose AUC during an IPGTT (r = 0.44, p = 0.03). Swimming exercise-induced attenuation of hyperglycemia in ZDF rats is independent of changes in body weight and could result in part from modulation of muscle AKT activation acting via alterations of systemic AA metabolism.

Effects of reduced dietary protein and supplemental rumen-protected essential amino acids on the nitrogen efficiency of dairy cows

When fed to meet the metabolizable protein requirements of the National Research Council, dairy cows consume an excess of N, resulting in approximately 75% of dietary N being lost to the environment as urine and feces. Reductions in environmental N release could be attained through an improvement in N efficiency. The objective of this study was to determine if the predicted reduction in milk yield associated with feeding a low-protein diet to lactating dairy cows could be avoided by dietary supplementation with 1 or more ruminally protected (RP) AA. Fourteen multiparous and 10 primiparous Holstein cows, and 24 multiparous Holstein × Jersey crossbred cows were used in a Youden square design consisting of 8 treatments and 3 periods. The 8 dietary treatments were (1) a standard diet containing 17% crude protein [CP; positive control (PC)], (2) a 15% CP diet [negative control (NC)], (3) NC plus RP Met (+M), (4) NC plus RP Lys (+K), (5) NC plus RP Leu (+L), (6) NC plus RP Met and Lys (+MK), (7) NC plus RP Met and Leu (+ML), and (8) NC plus RP Met, Lys, and Leu (+MKL). Dry matter intake was not affected by treatment. Crude protein intake was lower for NC and RP AA treatments compared with the PC treatment. No detrimental effect was detected of the low-CP diet alone or in combination with AA supplementation on milk and fat yield. However, milk protein yield decreased for NC and +MKL diets, and lactose yield decreased for the +MKL compared with the PC diet. Milk urea N concentrations were lower for all diets, suggesting that greater N efficiency was achieved by feeding the low-protein diet. Minimal effects of treatments on arterial plasma essential AA concentrations were detected, with only Ile and Val being significantly lower in the NC than in the PC diet. Phosphorylation ratios of signaling proteins known to regulate mRNA translation were not affected by treatments. This study highlights the limitations of requirement models aggregated at the protein level and the use of fixed postabsorptive efficiency to calculate milk protein requirements. Milk protein synthesis regulation by signaling pathways in vivo is still poorly understood.

PC.16 Hyperalimentation and plasma levels of conditionally essential amino acids in very preterm infants

BackgroundThe Standardised, Concentrated with Added Macronutrients Parenteral (SCAMP) nutrition regimen is a method of hyperalimentation for very preterm infants (VPI). Current neonatal parenteral nutrition (PN) amino acid (AA) formulations predate...

Study of plasma amino acid levels in children with autism: An Egyptian sample

BackgroundThe aetiology of autism is unclear and autistic symptoms had been attributed to an abnormal functional imbalance in neurotransmitter amines such as dopamine, noradrenaline and serotonin. ObjectiveTo study plasma essential and non-essential amino acid levels, protein electrophoresis, serum ammonia, and urea in autistic children in comparison with controls. MethodsTwenty autistic children were compared to twenty healthy age and sex matched normal children serving as control, where serum amino acids, urea, ammonia and protein electrophoresis were estimated. ResultsAs regards essential amino acid levels, autistic children had significant lower plasma levels of leucine, isoleucine, phenylalanine, methionine and cystine than controls (P<0.05),while there was no statistical difference in the level of tryptophan, valine, threonine, arginine, lysine and histidine (P>0.05). In non-essential amino acid levels, phosphoserine was significantly raised in autistic children than in controls (P<0.05). Autistic children had lower level of hydroxyproline, serine and tyrosine than controls (P<0.05). On the other hand there was no significant difference in levels of taurin, asparagine, alanine, citrulline, GABA, glycine, glutamic acid, and ornithine (P>0.05).There was no significant difference between cases and controls as regards the levels of urea, ammonia, total proteins, albumin and globulins (alpha 1, alpha 2, beta and gamma) (P>0.05). ConclusionsAutistic children had lower levels of some plasma amino acids except for glycine and glutamic acids and phosphoserine were increased with normal serum levels of urea, ammonia, total proteins, albumin and globulins (alpha 1, alpha 2, beta and gamma).

Pediatric reference intervals for plasma and urine essential amino acids in a Turkish population.

To establish age- and sex-specific reference intervals for essential amino acids in a healthy Turkish pediatric population. A total of 945 clinically healthy children (531 boys and 414 girls, ranging in age from birth to 14 years) were enrolled. Plasma and urine amino acids' concentrations were measured by high-performance liquid chromatography. Concentrations of essential amino acids in plasma were higher in girls than in boys in the age groups of 0-1 months and 7-14 years; however, there was no difference in the other age groups. Concentrations of essential amino acids in urine were higher in girls than in boys in the age group of 0-1 months; however, there was no difference in the other age groups. Our results demonstrated the sex-related differences in concentrations ofleucine, isoleucine, valine, phenylalanine, lysine, and histidine in plasma, which increased with age in boys but not in girls. The concentrations of leucine, tryptophan, methionine, and lysine in urine declined with age in girls but not in boys, which were sex-related differences, too. We defined essential amino acids' reference intervals in a Turkish pediatric population.

Plasma kinetic of ingested essential amino acids in healthy elderly people

The purpose of this study was to investigate whether the documented difficulties of physiological amounts of essential amino acids (EAAs) (7g) to induce protein synthesis could be reflected in a simple method adaptable to a clinical setting. Sixteen healthy individuals, nine elderly (75.3±3.5 years), and seven young (28±2.5 years) were enrolled in the study. Five minutes before EAA ingestion (baseline) and 20, 40, 60, 90, 120, 180min after EAA ingestion, venous blood samples were taken from the ante-cubital vein to determine the concentrations of EAAs (μmol/L). The results show that plasma EAA increases were significantly higher in old than in young persons at the considered time points (from p<0.004 to p<0.001) (unpaired Student t test). However, the velocity rate of the increasing was slower in old subjects than in young group. The study shows that EAAs ingestion by old subject is associated with reduced muscle EAA uptake.

Effects of dietary combination of corn and rice as whole crop silage and grain sources on carbohydrate digestion and nitrogen use in steers

Four Holstein steers were used to evaluate the combination effects of whole crop corn (Cs) or rice (Rs) silage with steam-flaked corn (Cg) or rice (Rg) grain (four dietary treatments) on ruminal carbohydrate digestion, duodenal nitrogen (N) flow and plasma essential amino acid (EAA) concentration. The ruminal digestibility of starch and nonfiber carbohydrate (NFC) for Rs and Rg diets compared with Cs and Cg diets was greater, but that of neutral detergent fiber (aNDFom) was less. Because the ruminal disappearance of NFC plus aNDFom was similar across four dietary treatments, microbial N flow was not affected by the diets. There was an interaction of methionine (Met) flow by silage and grain sources: greatest for CsRg and least for RsRg diet, and blood plasma concentration of Met after feeding was lower for Rg than Cg diets. Postprandial reduction degree of plasma EAA varied with the diets and individual EAA. The Cs diets compared with the Rs diets tended to be greater in N retention because of greater digestible organic matter (OM) intake. These results suggest that silage source combined with corn or rice grain affects N use in steers through the digestible OM intake, and the kinds of limiting AA may differ among the combination of silage and grain sources.

Increased consumption of salmon during pregnancy partly prevents the decline of some plasma essential amino acid concentrations in pregnant women

Oily fish is a good source of n-3 long-chain polyunsaturated fatty acids. Since these fatty acids may change efficiency of amino acid (AA) absorption, we determined whether increased salmon consumption influences plasma AA concentrations in pregnant women and their newborns. Pregnant women were randomly allocated to remain on their habitual diet (n = 61; control group) or to consume two 150 g farmed salmon portions per week from 20 weeks pregnancy until birth (n = 62; salmon group). Plasma AA concentrations were determined in women at w20, w34 and w38 of pregnancy and in umbilical cord at delivery. Concentrations of arginine, valine, leucine and lysine were affected by both time of pregnancy and salmon intake (p < 0.05), with a smaller gestation-associated decrease in the salmon group. Total essential AA concentrations were similar in both groups at w20, but at w38 were higher in salmon group (p < 0.05). Cord plasma AA concentrations, higher than in maternal plasma (p < 0.01), were similar in the two groups (p > 0.05). Two portions/wk of oily fish increased plasma essential AA concentrations during pregnancy and could contribute to a maternal health benefit. Two portions/wk of salmon did not affect plasma AA concentrations in the newborn. NCT00801502.

Rumen-protected lysine, methionine, and histidine increase milk protein yield in dairy cows fed a metabolizable protein-deficient diet

The objective of this experiment was to evaluate the effect of supplementing a metabolizable protein (MP)-deficient diet with rumen-protected (RP) Lys, Met, and specifically His on dairy cow performance. The experiment was conducted for 12wk with 48Holstein cows. Following a 2-wk covariate period, cows were blocked by DIM and milk yield and randomly assigned to 1 of 4 diets, based on corn silage and alfalfa haylage: control, MP-adequate diet (ADMP; MP balance: +9 g/d); MP-deficient diet (DMP; MP balance: −317g/d); DMP supplemented with RPLys (AminoShure-L, Balchem Corp., New Hampton, NY) and RPMet (Mepron; Evonik Industries AG, Hanau, Germany; DMPLM); and DMPLM supplemented with an experimental RPHis preparation (DMPLMH). The analyzed crude protein content of the ADMP and DMP diets was 15.7 and 13.5 to 13.6%, respectively. The apparent total-tract digestibility of all measured nutrients, plasma urea-N, and urinary N excretion were decreased by the DMP diets compared with ADMP. Milk N secretion as a proportion of N intake was greater for the DMP diets compared with ADMP. Compared with ADMP, dry matter intake (DMI) tended to be lower for DMP, but was similar for DMPLM and DMPLMH (24.5, 23.0, 23.7, and 24.3kg/d, respectively). Milk yield was decreased by DMP (35.2kg/d), but was similar to ADMP (38.8kg/d) for DMPLM and DMPLMH (36.9 and 38.5kg/d, respectively), paralleling the trend in DMI. The National Research Council 2001model underpredicted milk yield of the DMP cows by an average (±SE) of 10.3±0.75kg/d. Milk fat and true protein content did not differ among treatments, but milk protein yield was increased by DMPLM and DMPLMH compared with DMP and was not different from ADMP. Plasma essential amino acids (AA), Lys, and His were lower for DMP compared with ADMP. Supplementation of the DMP diets with RP AA increased plasma Lys, Met, and His. In conclusion, MP deficiency, approximately 15% below the National Research Council requirements from 2001, decreased DMI and milk yield in dairy cows. Supplementation of the MP-deficient diet with RPLys and RPMet diminished the difference in DMI and milk yield compared with ADMP and additional supplementation with RPHis eliminated it. As total-tract fiber digestibility was decreased with the DMP diets, but DMI tended to increase with RP AA supplementation, we propose that, similar to monogastric species, AA play a role in DMI regulation in dairy cows. Our data implicate His as a limiting AA in high-producing dairy cows fed corn silage- and alfalfa haylage-based diets, deficient in MP. The MP-deficient diets clearly increased milk N efficiency and decreased dramatically urinary N losses.

Dietary practices in glutaric aciduria type 1 over 16 years

In glutaric aciduria type 1 (GA1), dietary treatment with emergency management (EM) is essential to prevent encephalopathic crisis (EC). In the present study, dietary practices were examined in a single UK centre without access to newborn screening. Twenty GA1 patients (11 males, median age: 10.2 years, range 2.2-24.1 years) were evaluated. Nine presented without EC (median diagnosis age: 1.1 years, range 4 days to 8 years) and 11 with EC (median diagnosis age 10 months, range 6 months to 1.7 years). Dietary treatment, neurological outcome, anthropometry and biochemical/haematological markers were assessed. Diet treatment varied according to age of diagnosis and symptom severity. Four of six pre-encephalopathic children diagnosed before 2 years of age were treated with carnitine, protein restriction (medium l.2 g kg day(-1)) and lysine-free/low tryptophan protein substitute (PS) (medium dose: 1.6 g kg day(-1)). EM consisted of natural protein cessation and glucose polymer with PS delivered via an enteral feeding tube. Older children (>3 years) without EC were given carnitine and protein restriction, and seven of nine EC patients had PS via an enteral feeding tube. Clinical deterioration occurred in two patients without EC; one taking PS and protein restriction (with a second untreatable pathology) and one after protein restriction only. In patients presenting with EC, four died and one had some improvement in movement, with the rest remaining stable but with severe disability. Patients taking PS had better nutritional markers [serum vitamin B(12) (P < 0.001), albumin (P < 0.001), haemoglobin (P < 0.001) and essential plasma amino acids]. Early diagnosis of GA1 before EC is essential because PS and protein restriction with meticulous EM prevents EC. PS also improves nutritional status irrespective of clinical condition.

Muscle full effect after oral protein: time-dependent concordance and discordance between human muscle protein synthesis and mTORC1 signaling

We previously showed that human muscle protein synthesis (MPS) increased during infusion of amino acids (AAs) and peaked at ≈120 min before returning to baseline rates, despite elevated plasma AA concentrations. We tested whether a protein meal elicited a similar response and whether signaling responses that regulate messenger RNA translation matched MPS changes. Eight postabsorptive healthy men (≈21 y of age) were studied during 8.5 h of primed continuous infusion of [1,2-¹³C₂]leucine with intermittent quadriceps biopsies for determination of MPS and anabolic signaling. After 2.5 h, subjects consumed 48 g whey protein. At 45-90 min after oral protein bolus, mean (± SEM) myofibrillar protein synthesis increased from 0.03 ± 0.003% to 0.10 ± 0.01%/h; thereafter, myofibrillar protein synthesis returned to baseline rates even though plasma essential AA (EAA) concentrations remained elevated (+130% at 120 min, +80% at 180 min). The activity of protein kinase B (PKB) and phosphorylation of eukaryotic initiation factor 4G preceded the rise of MPS and increases in phosphorylation of ribosomal protein kinase S6 (S6K1), and 4E-binding protein 1 (4EBP1) was superimposable with MPS responses until 90 min. However, although MPS decreased thereafter, all signals, with the exception of PKB activity (which mirrored insulin responses), remained elevated, which echoed the slowly declining plasma EAA profile. The phosphorylation of eukaryotic initiation factor 2α increased only at 180 min. Thus, discordance existed between MPS and the mammalian target of rapamycin complex 1 (mTORC1) and signaling (ie, S6K1 and 4EBP1 phosphorylation). We confirm our previous findings that MPS responses to AAs are transient, even with oral protein bolus. However, changes in MPS only reflect elevated mTORC1 signaling during the upswing in MPS.

Free amino acid distribution in plasma and liver of juvenile cobia (Rachycentron canadum) fed increased levels of lizardfish silage

Juvenile cobia (Rachycentron canadum) (100 g) were fed four moist diets (447–476 g kg−1 dry wt) where 0, 130, 260 or 390 g kg−1 of concentrated lizardfish (Saurida undosquamis) silage replaced fresh lizardfish, respectively. Blood and livers were sampled at 0, 6, 12, 24 and 48 h postfeeding at the end of the 3-week experiment. At 6 h postfeeding in all groups, maximum concentrations of most plasma essential amino acids were observed, while significantly lower levels of most non-essential amino acid levels were recorded compared to the other sampled times. At 6 and 12 h after feeding, the concentration of most plasma free amino acid (FAA) increased with an increase in dietary fish silage levels. Most FAA in livers of all groups peaked at 12 and 24 h postfeeding. However, at 48 h postfeeding, concentrations of most plasma FAA were significantly higher in fish fed 0% silage-based diet than in fish fed the other diets (4999 versus 3390–4339 nmol AA mL−1 plasma). Growth rates and feed utilization were significantly lower in cobia fed 26% or 39% silage-based diets than in fish fed 0% or 13% silage-based diets. Different levels of silage protein thus seemed to have effects on growth and feed utilization efficiency of juvenile cobia. Results from this study support the premise that fish silage can be included until 130 g kg−1 in cobia diets.

Associations between amino acids and bone mineral density in men with idiopathic osteoporosis

Idiopathic osteoporosis in middle-aged men is characterized by low-level bone formation. Inhibited anabolism may be involved in the pathogenesis of the disease and amino acids may be of importance. In the present study fasting amino acid profiles in plasma and erythrocytes were determined in 22 male idiopathic osteoporosis (MIO) patients and in 20 age-matched healthy men and associated with bone mineral density, bone histomorphometry and hormones. The osteoporotic patients had normal plasma essential amino acids but increased non-essential amino acids ( p = 0.001), particularly glutamine and glycine. The ratio essential/non-essential amino acids, an index of protein nutritional status, was decreased in the MIO patients (0.59 (0.04) μmol/l, mean (SD)), compared to controls (0.66 (0.05), p = 0.001). In the MIO patients, the ratio essential/non-essential plasma amino acids ( r = 0.60, p = 0.003) was positively correlated with lumbar spine bone mineral density. The erythrocyte amino acids represent a large proportion of the free amino acids in blood. A novel finding was the lower levels of erythrocyte tryptophan in MIO (12 (2) μmol/l) compared to controls (16 (3), p = 0.001) and decreased erythrocyte/plasma ratio (0.28 (0.07) vs. 0.33, (0.06), p < 0.01), suggesting an altered amino acid transport of tryptophan between plasma and erythrocytes. In the combined group of MIO and control men ( n = 42), bone mineral density was positively correlated with erythrocyte tryptophan in both the lumbar spine ( r = 0.45, p = 0.003) and femoral neck ( r = 0.56, p < 0.001). The bone histomorphometric variables wall thickness, trabecular thickness and mineral apposition rate were all positively associated with erythrocyte tryptophan levels in the MIO patients. In the combined group of MIO and controls, a multiple regression analysis showed that erythrocyte tryptophan could explain 22% of the variation of lumbar spine and 30% of the variation in femoral neck bone mineral density. We conclude that men with idiopathic osteoporosis have changes in free amino acid profiles which indicate their altered utilization. The correlations between tryptophan and bone mineral density and bone histomorphometry suggest a link between tryptophan and osteoblast function which may be important for bone health.

Improved plasma amino acids pattern following 12 months of supplemented low-protein diet in peritoneal dialysis patients

Background: Decreased plasma essential amino acid (EAA) levels, increased nonessential amino acid (NEAA) levels, and low EAA to NEAA ratio (E/NEAA) are common in peritoneal dialysis (PD) patients and may impact uremic complications. In the present study, we investigate the impact of keto acids–supplemented low–protein (sLP) diet on plasma amino acids (AAs) patterns in stable PD patients. Methods: This is a supplemental analysis of a previously published prospective and randomized trial. Thirty-nine PD patients selected from the original population were divided to receive either low (LP: 0.6–0.8 g/kg ideal body weight [IBW]/d, n = 13), keto acids–supplemented low- (sLP: 0.6–0.8 g/kg IBW/d + 0.12 g/kg IBW/d of keto acids, n = 12), or high- (HP: 1.0–1.2 g/kg IBW/d, n = 14) protein diets and followed for 1 year. Plasma AA patterns were assessed at baseline and 12 months using high-performance liquid chromatography. Results: Whereas there were no significant differences between the three groups at baseline, following 12 months, the E/NEAA had increased significantly in group sLP (0.58 ± 0.16 to 0.83 ± 0.20, p < 0.05), but was not different in either LP (0.62 ± 0.20 to 0.72 ± 0.13, p = ns) or HP (0.66 ± 0.14 to 0.74 ± 0.12, p = ns) group. This change in E/NEAA in group sLP was due to a significant decrease in NEAA concomitantly with maintained EAA levels, whereas in the other two groups, neither EAA nor NEAA changed significantly. Conclusions: A low-protein diet supplemented with keto acids significantly improved the pattern of plasma AA in prevalent PD patients.

Effects of rumen-protected tryptophan on growth performance, fibre characteristics, nutrient utilization and plasma essential amino acids in Cashmere goats during the cashmere slow growth period

Tryptophan (Trp) is a limiting amino acid in growing ruminants and supplementation of Trp in a rumen-protected form may have positive effects on performance in ruminants. Trp may affect cashmere fibre growth by regulating plasma melatonin secretion. From December to February, identified as the cashmere slow growth period, cashmere growth rate slows down and plasma melatonin secretion declines. Thus, Trp supplementation may affect cashmere fibre growth positively during this period. This study was conducted to investigate the effects of rumen-protected tryptophan (RPT) on Cashmere goats during the cashmere slow growth period. Optimal RPT supplementation level was determined. The Thirty-six Liaoning Cashmere goat wethers (41.63 ± 0.37 kg) aged 1.5-year-old were stratified by weight and randomly assigned to the following treatments: without RPT (control), low RPT (LRPT), medium RPT (MRPT) and high RPT (HRPT) at RPT levels of 0, 2.0, 4.0 and 6.0 g per goat per day, respectively. LRPT and MRPT supplementation increased average daily gain ( P < 0.05) and N retention ( P < 0.05).The length and growth rate of cashmere fibre increased both linearly ( P < 0.05) and quadratically ( P < 0.05) with increasing RPT supplementation. Plasma Trp concentration increased linearly ( P < 0.05) with increasing RPT supplementation. Conversely, RPT supplementation decreased plasma isoleucine, valine and total essential amino acid concentrations ( P < 0.05). In conclusion, RPT supplementation potentially enhanced growth performance, cashmere fibre growth and N utilization in Liaoning Cashmere goat wethers. In experimental conditions of the current trial, the optimum RPT supplementation level was 2.0 g per goat per day during the cashmere slow growth period.

A specific protein-enriched enteral formula decreases cortisolemia and improves plasma albumin and amino acid concentrations in elderly patients

BackgroundOld age is associated with an involuntary and progressive but physiological loss of muscle mass. The aim of this study was to evaluate the effects of exclusive consumption for 6 months of a protein-enriched enteral diet with a relatively high content of branched-chain amino acids on albuminemia, cortisolemia, plasma amino acids, insulin resistance, and inflammation biomarkers in elderly patients.MethodsThirty-two patients from the Clinical Nutrition Outpatient Unit at our hospital exclusively consumed a protein-enriched enteral diet for 6 months. Data were collected at baseline and at 3 and 6 months on anthropometric and biochemical parameters and on plasma concentrations of amino acids, cortisol, adrenocorticotropic hormone, urea, creatinine, insulin resistance, and inflammation biomarkers.ResultsThe percentage of patients with albumin concentration below normal cut-off values decreased from 18% to 0% by the end of the study. At 6 months, concentrations of total plasma (p = 0.008) and essential amino acids (p = 0.011), especially branched-chain amino acids (p = 0.031), were higher versus baseline values, whereas 3-methylhistidine (p = 0.001), cortisol (p = 0.001) and adrenocorticotropic hormone (p = 0.004) levels were lower.ConclusionsRegular intake of specific protein-enriched enteral formula increases plasma essential amino acids, especially branched-chain amino acids, and decreases cortisol and 3-methylhistidine, while plasma urea and creatinine remain unchanged.

Short-Term Administration of a Combination of Recombinant Growth Hormone and Insulin-Like Growth Factor-I Induces Anabolism in Maintenance Hemodialysis

Resistance to GH and IGF-I is a significant complication of severe chronic kidney disease, which contributes to muscle wasting. Pharmacological doses of recombinant human (rh) GH or rhIGF-I have been proposed to treat this catabolic condition. This study was undertaken to examine the potential additive anabolic effects of rhGH + rhIGF-I compared with rhIGF-I. We studied eight well-nourished hemodialysis patients in a random crossover design and compared the metabolic effects of a 3-d administration of moderate dose of rhIGF-I (40 microg/kg per 12h) with an association of rhIGF-I + rhGH (50 microg/kg/d). Leucine kinetics, plasma amino acids (AAs), serum insulin, and IGF binding proteins (IGFBP)-1 and -3 were measured. The net protein balance was not affected by rhIGF-I alone, whereas serum insulin and IGFBP-3 decreased (P < 0.05) and IGFBP-1 increased (P < 0.01). With the combination rhGH + rhIGF-I, an increase of IGFBP-3 (P < 0.01) and insulin (P < 0.01) as well as a decrease of IGFBP-1 (P < 0.01) occurred. Plasma essential AAs (P = 0.01) as well as the essential to nonessential AA ratio (P < 0.001) decreased. Whole-body protein net balance increased significantly (P < 0.05) with a 22% decrease in leucine oxidation and a 15% increase in nonoxidative leucine disposal. In dialysis patients, rhIGF-I administration at a moderate dose has no protein metabolic effect, but the association with a moderate dose of rhGH is followed by a significant anabolic response.

INDIVIDUAL essential amino acids in plasma and urine of surgical patients.

INDIVIDUAL essential amino acids in plasma and urine of surgical patients.

Long-term feeding effects of dietary protein levels on egg production, immunocompetence and plasma amino acids of laying hens in subtropical condition

The objective of this study was to determine the effect of protein levels on production performance, immune response, liver triglyceride and plasma amino acids profile of laying hens during 21-48 weeks of age. Two groups of commercial hens (Babcock B-308) were fed with diets with different crude protein levels (14% and 18% CP). The high protein diet (18% CP) significantly increased production performance, essential amino acid intake, spleen weight (% of body weight), ND-titre (haemagglutination-inhibition test), serum albumin (g/dl), serum alpha-globulin and plasma essential amino acids (except histidine) and decreased liver triglyceride (mg/g liver) in relation to the low protein diet (14% CP). In long-term effect, therefore, this study suggested that adequate dietary condition of amino acids, particularly methionine and branch-chain amino acids is necessary for sustaining normal immunocompetence and achieving maximum production performance.

Lactation Performance of Mid-Lactation Dairy Cows Fed Ruminally Degradable Protein at Concentrations Lower Than National Research Council Recommendations

The aim of this study was to test whether feeding of diets containing lower proportions of ruminally degradable protein (RDP) but with a constant proportion of ruminally undegradable protein (RUP) alters feed intake, milk production and yield, and the apparent efficiency of N utilization by mid-lactation dairy cows. During the covariate period (d 1 to 28), 40 mid-lactation cows (36 Holstein and 4 Jersey × Holstein cross-breds) were fed a common diet formulated to contain 11.3% of diet dry matter (DM) as RDP. During the treatment period (d 29 to 47), cows were randomly assigned to 1 of 4 diets formulated to contain 11.3, 10.1, 8.8, or 7.6% RDP, whereas ruminally undegradable protein remained constant at 7.1% of DM. All diets contained 47.5% forage and 52.5% concentrate on a DM basis. Dry matter intake was significantly reduced for the 7.6% RDP diet. The lowest RDP content was associated with a trend for reduced milk yield. Dietary RDP had no effect on body weight or milk fat, protein, and lactose contents. Milk protein yield was not affected by RDP level; however, milk fat yield decreased linearly as dietary RDP was reduced. Concentrations of plasma essential amino acids were unaffected, whereas milk urea-N concentrations decreased linearly as dietary RDP content was reduced. The apparent efficiency of N utilization for milk N production increased from 27.7% on the 11.3% RDP diet to 38.6% on the 7.6% RDP diet. The dietary RDP requirement of cows in this study was apparently met between 15.9 and 14.7% dietary crude protein. Milk production was not significantly affected by the 8.8% RDP (15.9% crude protein) diet even though the NRC (2001) model predicted that RDP supply was 87% of that required, suggesting the current NRC recommendations for RDP may be overestimated for mid-lactation dairy cows in this study.