scholarly journals Effect of Amino Acid Infusion on Central Thermoregulatory Control in Humans

2004 ◽  
Vol 100 (3) ◽  
pp. 634-639 ◽  
Author(s):  
Yasufumi Nakajima ◽  
Akira Takamata ◽  
Takashi Matsukawa ◽  
Daniel I. Sessler ◽  
Yoshihiro Kitamura ◽  
...  
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Metabolic Rate ◽  
Core Temperature ◽  
Skin Surface ◽  
Saline Infusion ◽  
Acid Infusion ◽  
Set Point ◽  
Surface Warming ◽  
Amino Acid Infusion

Background Administration of protein or amino acids enhances thermogenesis, presumably by stimulating oxidative metabolism. However, hyperthermia results even when thermoregulatory responses are intact, suggesting that amino acids also alter central thermoregulatory control. Therefore, the authors tested the hypothesis that amino acid infusion increases the thermoregulatory set point. Methods Nine male volunteers each participated on 4 study days in randomized order: (1) intravenous amino acids infused at 4 kJ x kg(-1) x h(-1) for 2.5 h combined with skin-surface warming, (2) amino acid infusion combined with cutaneous cooling, (3) saline infusion combined with skin-surface warming, and (4) saline infusion combined with cutaneous cooling. Results Amino acid infusion increased resting core temperature by 0.3 +/- 0.1 degrees C (mean +/- SD) and oxygen consumption by 18 +/- 12%. Furthermore, amino acid infusion increased the calculated core temperature threshold (triggering core temperature at a designated mean skin temperature of 34 degrees C) for active cutaneous vasodilation by 0.3 +/- 0.3 degrees C, for sweating by 0.2 +/- 0.2 degrees C, for thermoregulatory vasoconstriction by 0.3 +/- 0.3 degrees C, and for thermogenesis by 0.4 +/- 0.5 degrees C. Amino acid infusion did not alter the incremental response intensity (i.e., gain) of thermoregulatory defenses. Conclusions Amino acid infusion increased the metabolic rate and the resting core temperature. However, amino acids also produced a synchronous increase in all major autonomic thermoregulatory defense thresholds; the increase in core temperature was identical to the set point increase, even in a cold environment with amble potential to dissipate heat. In subjects with intact thermoregulatory defenses, amino acid-induced hyperthermia seems to result from an increased set point rather than increased metabolic rate per se.

Removal of infused amino acids by splanchnic and leg tissues in humans

1986 ◽  
Vol 250 (4) ◽  
pp. E407-E413 ◽  
Author(s):  
R. A. Gelfand ◽  
M. G. Glickman ◽  
R. Jacob ◽  
R. S. Sherwin ◽  
R. A. DeFronzo
Keyword(s):  
Skeletal Muscle ◽  
Amino Acids ◽  
Amino Acid ◽  
Amino Acid Uptake ◽  
Branched Chain Amino Acids ◽  
Acid Uptake ◽  
Acid Infusion ◽  
Amino Acid Infusion ◽  
Significant Uptake ◽  
Branched Chain

To compare the contributions of splanchnic and skeletal muscle tissues to the disposal of intravenously administered amino acids, regional amino acid exchange was measured across the splanchnic bed and leg in 11 normal volunteers. Postabsorptively, net release of amino acids by leg (largely alanine and glutamine) was complemented by the net splanchnic uptake of amino acids. Amino acid infusion via peripheral vein (0.2 g X kg-1 X h-1) caused a doubling of plasma insulin and glucagon levels and a threefold rise in blood amino acid concentrations. Both splanchnic and leg tissues showed significant uptake of infused amino acids. Splanchnic tissues accounted for approximately 70% of the total body amino acid nitrogen disposal; splanchnic uptake was greatest for the glucogenic amino acids but also included significant quantities of branched-chain amino acids. In contrast, leg amino acid uptake was dominated by the branched-chain amino acids. Based on the measured leg balance, body skeletal muscle was estimated to remove approximately 25-30% of the total infused amino acid load and approximately 65-70% of the infused branched-chain amino acids. Amino acid infusion significantly stimulated both the leg efflux and the splanchnic uptake of glutamine (not contained in the infusate). We conclude that when amino acids are infused peripherally in normal humans, splanchnic viscera (liver and gut) are the major sites of amino acid disposal.

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.

Effect of Amino Acid Infusion on Whole Body Leucine Kinetics and Metabolic Rate

1987 ◽  
Vol 72 (s16) ◽  
pp. 27P-28P ◽  
Author(s):  
P.J. Pacy ◽  
K.N. Cheng ◽  
J. Webster ◽  
G.C. Ford ◽  
D. Halliday ◽  
...  
Keyword(s):  
Amino Acid ◽  
Metabolic Rate ◽  
Whole Body ◽  
Acid Infusion ◽  
Amino Acid Infusion ◽  
Leucine Kinetics

Effect of Infused Branched-Chain Amino Acids on Muscle and Whole-Body Amino Acid Metabolism in Man

1990 ◽  
Vol 79 (5) ◽  
pp. 457-466 ◽  
Author(s):  
Rita J. Louard ◽  
Eugene J. Barrett ◽  
Robert A. Gelfand
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Muscle Protein ◽  
Muscle Protein Synthesis ◽  
Branched Chain Amino Acids ◽  
Whole Body ◽  
Acid Infusion ◽  
Amino Acid Infusion ◽  
Branched Chain Amino Acid ◽  
Branched Chain

1. Using the forearm balance method, together with systemic infusions of l-[ring-2,6-3H]phenylalanine and l-[1-14C]leucine, we examined the effects of infused branched-chain amino acids on whole-body and skeletal muscle amino acid kinetics in 10 postabsorptive normal subjects; 10 control subjects received only saline. 2. Infusion of branched-chain amino acids caused a four-fold rise in arterial branched-chain amino acid levels and a two-fold rise in branched-chain keto acids; significant declines were observed in circulating levels of most other amino acids, including phenylalanine, which fell by 34%. Plasma insulin levels were unchanged from basal levels (8 ± 1 μ-units/ml). 3. Whole-body phenylalanine flux, an index of proteolysis, was significantly suppressed by branched-chain amino acid infusion (P < 0.002), and forearm phenylalanine production was also inhibited (P < 0.03). With branched-chain amino acid infusion total leucine flux rose, with marked increments in both oxidative and non-oxidative leucine disposal (P < 0.001). Proteolysis, as measured by endogenous leucine production, showed a modest 12% decrease, although this was not significant when compared with saline controls. The net forearm balance of leucine and other branched-chain amino acids changed from a basal net output to a marked net uptake (P < 0.001) during branched-chain amino acid infusion, with significant stimulation of local leucine disposal. Despite the rise in whole-body non-oxidative leucine disposal, and in forearm leucine uptake and disposal, forearm phenylalanine disposal, an index of muscle protein synthesis, was not stimulated by infusion of branched-chain amino acids. 4. The results suggest that in normal man branched-chain amino acid infusion suppresses skeletal muscle proteolysis independently of any rise of plasma insulin. Muscle branched-chain amino acid uptake rose dramatically in the absence of any apparent increase in muscle protein synthesis, as measured by phenylalanine disposal, or in branched-chain keto acid release. Thus, an increase in muscle branched-chain amino acid concentrations and/ or local branched-chain amino acid oxidation must account for the increased disposal of branched-chain amino acids.

scholarly journals Insulin is required for amino acid stimulation of dual pathways for translational control in skeletal muscle in the late-gestation ovine fetus

2009 ◽  
Vol 296 (1) ◽  
pp. E56-E63 ◽  
Author(s):  
Laura D. Brown ◽  
Paul J. Rozance ◽  
James S. Barry ◽  
Jacob E. Friedman ◽  
William W. Hay
Keyword(s):  
Skeletal Muscle ◽  
Amino Acids ◽  
Amino Acid ◽  
Ribosomal Protein ◽  
Translation Initiation ◽  
Late Gestation ◽  
Acid Infusion ◽  
Amino Acid Infusion ◽  
Ribosomal Protein S6 ◽  
Ovine Fetus

During late gestation, amino acids and insulin promote skeletal muscle protein synthesis. However, the independent effects of amino acids and insulin on the regulation of mRNA translation initiation in the fetus are relatively unknown. The purpose of this study was to determine whether acute amino acid infusion in the late-gestation ovine fetus, with and without a simultaneous increase in fetal insulin concentration, activates translation initiation pathway(s) in skeletal muscle. Fetuses received saline (C), mixed amino acid infusion plus somatostatin infusion to suppress amino acid-stimulated fetal insulin secretion (AA+S), mixed amino acid infusion with concomitant physiological increase in fetal insulin (AA), or high-dose insulin infusion with euglycemia and euaminoacidemia (HI). After a 2-h infusion period, fetal skeletal muscle was harvested under in vivo steady-state conditions and frozen for quantification of proteins both upstream and downstream of mammalian target of rapamycin (mTOR). In the AA group, we found a threefold increase in ribosomal protein S6 kinase (p70S6k) and Erk1/2 phosphorylation; however, blocking the physiological rise in insulin with somatostatin in the AA+S group prevented this increase. In the HI group, Akt, Erk1/2, p70S6k, and ribosomal protein S6 were highly phosphorylated and 4E-binding protein 1 (4E-BP1) associated with eukaryotic initiation factor (eIF)4E decreased by 30%. These data show that insulin is a significant regulator of intermediates involved in translation initiation in ovine fetal skeletal muscle. Furthermore, the effect of amino acids is dependent on a concomitant increase in fetal insulin concentrations, because amino acid infusion upregulates p70S6k and Erk only when amino acid-stimulated increase in insulin occurs.

Effects of i.v. amino acids on human splanchnic and whole body oxygen consumption, blood flow, and blood temperatures

1994 ◽  
Vol 266 (3) ◽  
pp. E396-E402 ◽  
Author(s):  
T. Brundin ◽  
J. Wahren
Keyword(s):  
Amino Acids ◽  
Blood Flow ◽  
Cardiac Output ◽  
Oxygen Consumption ◽  
Amino Acid ◽  
The Body ◽  
Whole Body ◽  
Acid Infusion ◽  
Amino Acid Infusion ◽  
Splanchnic Oxygen

The thermic effect of amino acid administration was examined in healthy subjects. Pulmonary and splanchnic oxygen uptake, cardiac output, splanchnic blood flow, and blood temperatures were measured in eight healthy men before and during 2.5 h of intravenous infusion of 600 kJ of a mixture of 19 amino acids. Indirect calorimetry and catheter techniques were used, including thermometry in arterial and a hepatic venous blood. During the infusion, pulmonary oxygen uptake rose progressively from a basal value of 269 +/- 6 to 321 +/- 8 ml/min after 2.5 h. The splanchnic oxygen consumption increased from a basal level of 64 +/- 4 to a peak value of 91 +/- 7 ml/min after 2 h of infusion. The 2.5 h average splanchnic proportion of the amino acid-induced whole body thermogenesis was 51 +/- 11%. Cardiac output increased from 6.2 +/- 0.3 in the basal state to 7.3 +/- 0.4 l/min, whereas the splanchnic blood flow remained unchanged during the infusion period. The arteriohepatic venous oxygen difference increased from 51 +/- 4 in the basal state to 65 +/- 5 ml/l after 2 h of amino acid infusion. The blood temperature rose by approximately 0.25 degrees C during the amino acid infusion, reflecting an increased heat accumulation in the body. It is concluded that the splanchnic tissues account for approximately one-half of the amino acid-induced whole body thermogenesis, that amino acid infusion augments blood flow in the extrasplanchnic but not in the splanchnic tissues, and stimulates the accumulation of heat in the body most likely via a resetting of the central thermosensors.

scholarly journals Effect of Preinduction Amino Acid Infusion on Body Core Temperature

1999 ◽  
Vol 36 (2) ◽  
pp. 197
Author(s):  
Kyu Taek Choi ◽  
Jong Hyun Lee ◽  
Eun Ju Lee ◽  
Dong Myung Lee
Keyword(s):  
Amino Acid ◽  
Core Temperature ◽  
Body Core Temperature ◽  
Acid Infusion ◽  
Amino Acid Infusion ◽  
Body Core

Glucocorticoids modulate amino acid-induced translation initiation in human skeletal muscle

2004 ◽  
Vol 287 (2) ◽  
pp. E275-E281 ◽  
Author(s):  
Zhenqi Liu ◽  
Guolian Li ◽  
Scot R. Kimball ◽  
Linda A. Jahn ◽  
Eugene J. Barrett
Keyword(s):  
Skeletal Muscle ◽  
Amino Acids ◽  
Amino Acid ◽  
Translation Initiation ◽  
Human Skeletal Muscle ◽  
Mrna Translation ◽  
Nucleotide Exchange ◽  
Acid Infusion ◽  
Amino Acid Infusion ◽  
Guanine Nucleotide Exchange

Amino acids are unique anabolic agents in that they nutritively signal to mRNA translation initiation and serve as substrates for protein synthesis in skeletal muscle. Glucocorticoid excess antagonizes the anabolic action of amino acids on protein synthesis in laboratory animals. To examine whether excessive glucocorticoids modulate mixed amino acid-signaled translation initiation in human skeletal muscle, we infused an amino acid mixture (10% Travasol) systemically to 16 young healthy male volunteers for 6 h in the absence ( n = 8) or presence ( n = 8) of glucocorticoid excess (dexamethasone 2 mg orally every 6 h for 3 days). Vastus lateralis muscles were biopsied before and after amino acid infusion, and the phosphorylation of eukaryotic initiation factor (eIF) 4E-binding protein 1 (4E-BP1), ribosomal protein S6 kinase (p70S6K), and eIF2α and the guanine nucleotide exchange activity of eIF2B were measured. Systemic infusion of mixed amino acids significantly stimulated the phosphorylation of 4E-BP1 ( P < 0.04) and p70S6K ( P < 0.001) and the dephosphorylation of eIF2α ( P < 0.003) in the control group. Dexamethasone treatment did not alter the basal phosphorylation state of 4E-BP1, p70S6K, or eIF2α; however, it abrogated the stimulatory effect of amino acid infusion on the phosphorylation of 4E-BP1 ( P = 0.31) without affecting amino acid-induced phosphorylation of p70S6K ( P = 0.002) or dephosphorylation of eIF2α ( P = 0.003). Neither amino acid nor dexamethasone treatment altered the guanine nucleotide exchange activity of eIF2B. We conclude that changes of amino acid concentrations within the physiological range stimulate mRNA translation by enhancing the binding of mRNA to the 43S preinitiation complex, and the activity of p70S6K and glucocorticoid excess blocks the former action in vivo in human skeletal muscle.

Response of rat heart and skeletal muscle protein in vivo to insulin and amino acid infusion

1993 ◽  
Vol 264 (6) ◽  
pp. E958-E965 ◽  
Author(s):  
P. H. McNulty ◽  
L. H. Young ◽  
E. J. Barrett
Keyword(s):  
Skeletal Muscle ◽  
Amino Acids ◽  
Protein Synthesis ◽  
Amino Acid ◽  
Muscle Protein ◽  
Muscle Protein Synthesis ◽  
Skeletal Muscle Protein ◽  
Acid Infusion ◽  
Amino Acid Infusion

Whether insulin, at physiological concentrations, stimulates net muscle protein synthesis in vivo remains unresolved. To examine this, we infused either saline, insulin (2.8 mU.kg-1.min-1, euglycemic clamp), an amino acid solution, or insulin plus amino acids for 4 h into awake overnight-fasted rats. Heart and skeletal muscle protein synthesis was measured by either a continuous tracer infusion method, using L-[1-14C]leucine, L-[2,5-3H]leucine, or L-[ring-2,6-3H]phenylalanine or by injection of L-[ring-2,6-3H]phenylalanine with a pool-flooding bolus of unlabeled phenylalanine. In heart, synthesis rates obtained using the arterial plasma specific activity of [3H]phenylalanine administered as either a tracer infusion or flooding bolus were comparable in saline-treated rats (range 10.9 +/- 1.2 to 12.2 +/- 0.9%/day) and were not affected by infusion of insulin or amino acids. Estimates using continuous infusion of L-[1-14C]leucine were significantly lower (P < 0.001), except when unlabeled amino acids were given also. In skeletal muscle, rates estimated using the flooding bolus (6.7 +/- 0.8%/day) were also not affected by insulin or amino acids. Estimates using continuous infusion of [3H]leucine (2.6 +/- 0.3%/day) or [3H]phenylalanine (2.8 +/- 1.0%/day) were lower and were still lower using [14C]leucine (1.6 +/- 0.6%/day), but increased toward those estimated with the flooding bolus during amino acid infusion. We conclude that, in heart muscle of the mature rat in vivo, neither insulin nor amino acids affect protein synthesis.(ABSTRACT TRUNCATED AT 250 WORDS)

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