scholarly journals Effect of feed intake on amino acid transfers across the ovine hindquarters

2003 ◽  
Vol 89 (2) ◽  
pp. 167-179 ◽  
Author(s):  
S. O. Hoskin ◽  
I. C. Savary-Auzeloux ◽  
A. G. Calder ◽  
G. Zuur ◽  
G. E. Lobley
Keyword(s):  
Protein Synthesis ◽  
Amino Acid ◽  
Feed Intake ◽  
Vastus Lateralis ◽  
Vena Cava ◽  
Latin Square ◽  
Live Weight ◽  
Isoleucine Leucine ◽  
Peripheral Tissues ◽  
Branched Chain

Responses in variables of amino acid (AA) metabolism across peripheral tissues to feed intake were studied in six sheep (mean live weight 32 kg) prepared with arterio–venous catheters across the hindquarters. Four intakes (0·5, 1·0, 1·5 and 2·5 × maintenance energy) were offered over 2-week periods to each sheep in a Latin square design with two animals replicated. Animals were infused intravenously with a mixture of U-13C-labelled AA for 10 h and integrated blood samples withdrawn from the aorta and vena cava hourly between 5 and 9 h of infusion. Biopsy samples were also taken from skin andm. vastus lateralis. Data from both essential (histidine, isoleucine, leucine, lysine, phenylalanine, threonine) and nonessential (glycine, proline, serine, tyrosine) AA were modelled to give rates of inward and outward transport, protein synthesis and degradation, plus the fraction of total vascular inflow that exchanged with the hindquarter tissues. Rates of inward transport varied more than 10-fold between AA. For all essential AA (plus serine), inward transport increased with food intake (P<0·04). There were corresponding increases in AA efflux (P<0·05) from the tissues for threonine and the branched-chain AA. Protein synthesis rates estimated from the kinetics of these AA also increased with intake (P<0·02). Rates of inward transport greatly exceeded the amount of AA necessary to support protein retention, but were more similar to rates of protein synthesis. Nutritional or other strategies to enhance AA transport into peripheral tissues are unlikely to increase anabolic responses.

scholarly journals Effect of feed intake on ovine hindlimb protein metabolism based on thirteen amino acids and arterio–venous techniques

2001 ◽  
Vol 86 (5) ◽  
pp. 577-585 ◽  
Author(s):  
Simone O. Hoskin ◽  
Isabelle C. Savary ◽  
Grietje Zuur ◽  
Gerald E. Lobley
Keyword(s):  
Amino Acids ◽  
Protein Synthesis ◽  
Plasma Flow ◽  
Feed Intake ◽  
Vena Cava ◽  
Protein Breakdown ◽  
Peripheral Tissues ◽  
Linear Effect ◽  
Wide Range ◽  
Branched Chain

It has been suggested that protein synthesis in peripheral tissues: (1) responds in a curvilinear manner to increasing feed intake over a wide range of feeding levels; and (2) has a greater sensitivity to intake than protein breakdown. The aim of the present experiment was to test these hypotheses across the ovine hindlimb. Six growing sheep (6–8 months, 30–35 kg), with catheters in the aorta (two), posterior vena cava and jugular vein, received each of four intakes of dried grass pellets (0·5, 1·0, 1·5 and 2·5×maintenance energy; M) for a minimum of 7 d. A U-13C-labelled algal hydrolysate was infused intravenously for 10 h and from 3–9 hpara-aminohippuric acid was infused to measure plasma flow. Arterial and venous plasma were obtained over the last 4 h and the concentrations and enrichments of thirteen13C-labelled amino acids (AA) were determined by GC–MS. As intake increased, a positive linear response was found for plasma flow, arterial concentrations of the aromatic and branched-chain AA, total flow of all AA into the hindquarters and net mass balance across the hindquarters (except glycine and alanine). Based on two separate statistical analyses, the data for protein synthesis showed a significant linear effect with intake (except for phenylalanine, glycine and alanine). No significant curvilinear effect was found, which tends not to support hypothesis 1. Nonetheless, protein synthesis was not significantly different between 0·5, 1·0 and 1·5×M and thus the 2·5×M intake level was largely responsible for the linear relationship found. There was no significant response in protein breakdown to intake, which supports hypothesis 2.

scholarly journals Effects of intraruminal propionate supplementation on nitrogen utilisation by the portal-drained viscera, the liver and the hindlimb in lambs fed frozen rye grass

2003 ◽  
Vol 90 (5) ◽  
pp. 939-952 ◽  
Author(s):  
Isabelle C. Savary-Auzeloux ◽  
Linda Majdoub ◽  
Nathalie LeFloc'h ◽  
Isabelle Ortigues-Marty
Keyword(s):  
Protein Synthesis ◽  
Muscle Growth ◽  
Latin Square ◽  
Urea Synthesis ◽  
Peripheral Tissues ◽  
Rye Grass ◽  
Metabolisable Energy ◽  
Branched Chain ◽  
N Compounds

The influence of propionate supplementation on the splanchnic metabolism of amino acids (AA) and other N compounds (urea-N and NH3-N) and the supply of AA and NH3-N to the hindlimb was investigated in growing lambs. Six rumen-cannulated and multicatheterised lambs (32·2kg) were fed frozen rye grass at 690kJ metabolisable energy intake/d per kg average metabolic body weight. They were infused intraruminally with a salt solution (control) or with propionate solutions at 0·23mol/l (P1) or 0·41mol/l (P2) infused at a maximal rate of 1·68 (sd 0·057) ml/min according to a repeated Latin square design. The propionate infusion did not increase the net portal appearance of total AA (TAA)-N but increased that of some branched-chain AA (valine and to a lesser extent isoleucine). Simultaneously, the propionate treatment (especially P2) induced an increased TAA utilisation by the liver. This was due mainly to an increased (+79%;P<0·07) utilisation of the essential AA and particularly the branched-chain AA. A stimulation of protein synthesis in the liver is hypothesised since (1) propionate stimulated insulin secretion and (2) utilisation of non-essential AA were less influenced by the propionate treatment in the liver (except for alanine), suggesting that the AA utilised by the liver were directed towards protein synthesis rather than towards oxidation or urea synthesis. At the splanchnic level, the propionate treatment did not have any effect on the TAA, non-essential AA and essential AA, except for a net splanchnic release that was decreased for leucine (P<0·02) and methionine (P<0·01) and increased for threonine (P<0·05). The propionate treatment did not have any effect on the hindlimb uptake of AA (essential and non-essential). As a consequence, even though the propionate treatment induced some major alterations in the splanchnic metabolism of AA, there were no changes in the net AA balance in the hindlimb (and hence probably on muscle growth). The role of the splanchnic tissues in the regulation of the AA supply to the peripheral tissues (such as muscle) therefore appears to be prominent in the regulation of muscle growth. Whether the peripheral tissues regulate their own supply by interacting with the splanchnic tissues (and especially the liver) or the liver is the only regulator of the AA supply to the muscle remains in doubt.

scholarly journals Impaired branched chain amino acid metabolism alters feeding behavior and increases orexigenic neuropeptide expression in the hypothalamus

2011 ◽  
Vol 212 (1) ◽  
pp. 85-94 ◽  
Author(s):  
Megan N Purpera ◽  
Li Shen ◽  
Marzieh Taghavi ◽  
Heike Münzberg ◽  
Roy J Martin ◽  
...  
Keyword(s):  
Amino Acid ◽  
Food Intake ◽  
Feeding Behavior ◽  
Control Diet ◽  
Peripheral Tissues ◽  
Protein Status ◽  
Branched Chain Amino Acid ◽  
Branched Chain ◽  
Branched Chain Aminotransferase ◽  
Deficient Mice

Elevation of dietary or brain leucine appears to suppress food intake via a mechanism involving mechanistic target of rapamycin, AMPK, and/or branched chain amino acid (BCAA) metabolism. Mice bearing a deletion of mitochondrial branched chain aminotransferase (BCATm), which is expressed in peripheral tissues (muscle) and brain glia, exhibit marked increases in circulating BCAAs. Here, we test whether this increase alters feeding behavior and brain neuropeptide expression. Circulating and brain levels of BCAAs were increased two- to four-fold in BCATm-deficient mice (KO). KO mice weighed less than controls (25.9 vs 20.4 g,P<0.01), but absolute food intake was relatively unchanged. In contrast to wild-type mice, KO mice preferred a low-BCAA diet to a control diet (P<0.05) but exhibited no change in preference for low- vs high-protein (HP) diets. KO mice also exhibited low leptin levels and increased hypothalamicNpyandAgrpmRNA. Normalization of circulating leptin levels had no effect on either food preference or the increasedNpyandAgrpmRNA expression. If BCAAs act as signals of protein status, one would expect reduced food intake, avoidance of dietary protein, and reduction in neuropeptide expression in BCATm-KO mice. Instead, these mice exhibit an increased expression of orexigenic neuropeptides and an avoidance of BCAAs but not HP. These data thus suggest that either BCAAs do not act as physiological signals of protein status or the loss of BCAA metabolism within brain glia impairs the detection of protein balance.

Branched chain amino acid enriched elemental diets support hepatic protein synthesis in injured rats

1985 ◽  
Vol 5 (7) ◽  
pp. 737-748 ◽  
Author(s):  
Javier Sobrado ◽  
James J. Pomposelli ◽  
Kazuma Yamazaki ◽  
Alberto Maiz ◽  
Lyle L. Moldawer ◽  
...  
Keyword(s):  
Protein Synthesis ◽  
Amino Acid ◽  
Branched Chain Amino Acid ◽  
Elemental Diets ◽  
Branched Chain ◽  
Hepatic Protein Synthesis

Branched chain amino acid regulation of the ILV2 locus in Saccharomyces cerevisiae

Genome ◽  
1990 ◽  
Vol 33 (4) ◽  
pp. 596-603 ◽  
Author(s):  
Wei Xiao ◽  
Gerald H. Rank
Keyword(s):  
Amino Acid ◽  
Acetolactate Synthase ◽  
Multiple Control ◽  
Isoleucine Leucine ◽  
Acid Sensitivity ◽  
Cis Acting ◽  
General Amino Acid Control ◽  
Branched Chain Amino Acid ◽  
Branched Chain ◽  
Unusual Phenotype

Mutant regulatory loci of the branched pathway for the biosynthesis of isoleucine–valine and leucine were identified with the unusual phenotype of an amino acid dependent auxotrophy. Two mutant loci, bcs1 and bcs2, conferred branched chain amino acid sensitivity and showed independent segregation. Linkage studies defined bcs1 as a cis-acting regulatory site of ILV2 (SMR1). ILV2 upstream deletion analyses and high-copy transformation of the positive regulatory locus LEU3 ruled out the possibility of LEU3 protein binding palindromes mediating the branched chain amino acid dependent auxotrophy. In the presence of leucine and valine, the general amino acid control system (GCN4) was epistatic to bcs1 and bcs2, and under nonstarvation conditions GCN4 strains showed an increased acetolactate synthase activity over gcn4 strains. Thus in addition to general regulation of ILV2, GCN4 functions in basal level expression when the locus is subject to specific repression by pathway end product.Key words: yeast, isoleucine, leucine, valine pathway, amino acid sensitivity, gene regulation, multiple control.

scholarly journals Amino acid infusion increases the sensitivity of muscle protein synthesis in vivo to insulin. Effect of branched-chain amino acids

1988 ◽  
Vol 254 (2) ◽  
pp. 579-584 ◽  
Author(s):  
P J Garlick ◽  
I Grant
Keyword(s):  
Amino Acids ◽  
Protein Synthesis ◽  
Amino Acid ◽  
Muscle Protein ◽  
Muscle Protein Synthesis ◽  
Branched Chain Amino Acids ◽  
Acid Infusion ◽  
Amino Acid Infusion ◽  
Branched Chain

Rates of muscle protein synthesis were measured in vivo in tissues of post-absorptive young rats that were given intravenous infusions of various combinations of insulin and amino acids. In the absence of amino acid infusion, there was a steady rise in muscle protein synthesis with plasma insulin concentration up to 158 mu units/ml, but when a complete amino acids mixtures was included maximal rates were obtained at 20 mu units/ml. The effect of the complete mixture could be reproduced by a mixture of essential amino acids or of branched-chain amino acids, but not by a non-essential mixture, alanine, methionine or glutamine. It is concluded that amino acids, particularly the branched-chain ones, increase the sensitivity of muscle protein synthesis to insulin.

Amino acid requirements of growing pigs 5. The interaction between isoleucine and leucine

1984 ◽  
Vol 38 (2) ◽  
pp. 257-261 ◽  
Author(s):  
S. J. Taylor ◽  
D. J. A. Cole ◽  
D. Lewis
Keyword(s):  
Amino Acid ◽  
Conversion Efficiency ◽  
Live Weight ◽  
Basal Diet ◽  
Growing Pigs ◽  
Carcass Quality ◽  
Food Conversion ◽  
Isoleucine Leucine ◽  
Plasma Urea ◽  
Food Conversion Efficiency

ABSTRACTThirty-two female growing pigs (25 to 55 kg live weight) were subjected to four dietary treatments combining two levels of isoleucine and two levels of leucine to investigate the effects of leucine supply on the requirement for isoleucine.Results for daily live-weight gain, food conversion efficiency and carcass quality judged by ham dissection indicated that 3·8 g isoleucine per kg diet was marginally adequate for the growing pig in diets containing 13·4 g leucine per kg. An interaction between dietary leucine and isoleucine was demonstrated. Increasing the dietary leucine concentration to 20·4 g/kg clearly resulted in a deficiency of isoleucine in the basal diet, as daily gain, food conversion efficiency and carcass quality were significantly improved by increasing the isoleucine concentration from 3·8 g to 4·5 g/kg diet. Dietary leucine concentration did not influence performance at the higher level of isoleucine supply. Changes in plasma urea and amino acid concentrations confirmed the findings from the growth experiment of the interaction between isoleucine, leucine and valine.

Leucine and insulin activate p70 S6 kinase through different pathways in human skeletal muscle

2001 ◽  
Vol 281 (3) ◽  
pp. E466-E471 ◽  
Author(s):  
Jeffrey S. Greiwe ◽  
Guim Kwon ◽  
Michael L. McDaniel ◽  
Clay F. Semenkovich
Keyword(s):  
Skeletal Muscle ◽  
Amino Acids ◽  
Protein Synthesis ◽  
Human Skeletal Muscle ◽  
Vastus Lateralis ◽  
S6 Kinase ◽  
Signaling Mechanism ◽  
Insulin Resistant ◽  
Branched Chain ◽  
Plasma Leucine

Amino acids and insulin have anabolic effects in skeletal muscle, but the mechanisms are poorly understood. To test the hypothesis that leucine and insulin stimulate translation initiation in human skeletal muscle by phosphorylating 70-kDa ribosomal protein S6 kinase (p70S6k), we infused healthy adults with leucine alone ( n = 6), insulin alone ( n= 6), or both leucine and insulin ( n = 6) for 2 h. p70S6k and protein kinase B (PKB) serine473phosphorylation were measured in vastus lateralis muscles. Plasma leucine increased from ∼116 to 343 μmol/l during the leucine-alone and leucine + insulin infusions. Plasma insulin increased to ∼400 pmol/l during the insulin-alone and leucine + insulin infusions and was unchanged during the leucine-alone infusion. Phosphorylation of p70S6k increased 4-fold in response to leucine alone, 8-fold in response to insulin alone, and 18-fold after the leucine + insulin infusion. Insulin-alone and leucine + insulin infusions increased PKB phosphorylation, but leucine alone had no effect. These results show that physiological concentrations of leucine and insulin activate a key mediator of protein synthesis in human skeletal muscle. They suggest that leucine stimulates protein synthesis through a nutrient signaling mechanism independent of insulin, raising the possibility that administration of branched-chain amino acids may improve protein synthesis in insulin-resistant states.

scholarly journals Nutritional and endocrinological manipulation of lean deposition in forage-fed steers

1991 ◽  
Vol 66 (2) ◽  
pp. 171-185 ◽  
Author(s):  
J. M. Dawson ◽  
P. J. Buttery ◽  
M. J. Lammiman ◽  
J. B. Soar ◽  
C. P. Essex ◽  
...  
Keyword(s):  
Protein Synthesis ◽  
Protein Degradation ◽  
Lipid Composition ◽  
Muscle Protein ◽  
Muscle Protein Synthesis ◽  
Vastus Lateralis ◽  
Live Weight ◽  
Dry Matter Content ◽  
Semitendinosus Muscle ◽  
Intramuscular Lipid

The effect of supplementing grass silage with fishmeal on growth, muscle composition and the rate of muscle protein synthesis was investigated in young Friesian steers with and without oestradiol implants. The effect of the β-adrenergic agonist cimaterol was simultaneously investigated in animals fed on silage alone. Treatments lasted for 9 or 10 weeks. Fishmeal supplementation significantly increased animal growth rates (P < 0.001) and the weights of three dissected muscles (P < 0.001) compared with the silage-fed controls. These effects were further enhanced in animals also implanted with oestradiol. Muscle weights expressed as a proportion of body-weight were increased by fishmeal, suggesting that protein deposition had been enhanced. No further increase in the proportional muscle weights was obtained with oestradiol. Muscle dry matter content tended to be increased in both implanted and non-implanted animals receiving fishmeal compared with controls, but the proportions of protein, fat and ash were relatively constant. The intramuscular lipid composition was slightly altered by fishmeal. Muscle protein fractional synthetic rates (FSR), measured by continuous infusion of [3H]tyrosine, were increased by fishmeal in all three muscles of both implanted and non-implanted animals. There were no differences, however, due to oestradiol, over non-implanted fishmeal animals. This suggests that oestradiol may increase muscle accretion by reducing protein degradation rate. Cimaterol significantly increased longissimus dorsi (P < 0.05) and vastus lateralis (P < 0.01) muscle weights but had no effect on semitendinosus muscle weight or live-weight gain. The proportion of protein was increased (P <0.001) and the fat content reduced (P < 0.05) in all three muscles but intramuscular lipid composition was not markedly affected. Whilst methylhistidine: creatinine excretion was reduced by cimaterol, FSR were increased in the I. dorsi and v. lateralis muscles suggesting β-agonists have effects on both protein synthesis and protein degradation.

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