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

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.

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

Clinical Science ◽

10.1042/cs0790457 ◽

1990 ◽

Vol 79 (5) ◽

pp. 457-466 ◽

Cited By ~ 105

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.

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Measurement of L-[1-14C]Leucine Kinetics in Splanchnic and Leg Tissues In Humans: Effect of Amino Acid Infusion

Diabetes ◽

10.2337/diab.37.10.1365 ◽

1988 ◽

Vol 37 (10) ◽

pp. 1365-1372 ◽

Cited By ~ 32

Author(s):

R. A. Gelfand ◽

M. G. Glickman ◽

P. Castellino ◽

R. J. Louard ◽

R. A. DeFronzo

Keyword(s):

Amino Acid ◽

Acid Infusion ◽

Amino Acid Infusion ◽

Leucine Kinetics

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Changes in whole body and tissue oxygen consumption during recovery from hypothermia: effect of amino acid infusion

Clinical Nutrition ◽

10.1016/0261-5614(90)90230-p ◽

1990 ◽

Vol 9 ◽

pp. 28-29

Author(s):

K. Hersio ◽

J. Takala ◽

A. Kari ◽

H Huttunen

Keyword(s):

Oxygen Consumption ◽

Amino Acid ◽

Whole Body ◽

Tissue Oxygen ◽

Acid Infusion ◽

Amino Acid Infusion ◽

Tissue Oxygen Consumption

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

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.1994.266.3.e396 ◽

1994 ◽

Vol 266 (3) ◽

pp. E396-E402 ◽

Cited By ~ 7

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.

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Increase in anterior tibialis muscle protein synthesis in healthy man during mixed amino acid infusion: studies of incorporation of [1−13C]leucine

Clinical Science ◽

10.1042/cs0760447 ◽

1989 ◽

Vol 76 (4) ◽

pp. 447-454 ◽

Cited By ~ 158

Author(s):

W. M. Bennet ◽

A. A. Connacher ◽

C. M. Scrimgeour ◽

K. Smith ◽

M. J. Rennie

Keyword(s):

Protein Synthesis ◽

Amino Acid ◽

Muscle Protein ◽

Muscle Protein Synthesis ◽

Whole Body ◽

Body Protein ◽

Anterior Tibial Muscle ◽

Acid Infusion ◽

Amino Acid Infusion ◽

Anterior Tibial

1. Anterior tibial muscle protein synthesis in seven healthy postabsorptive men was determined from increases in muscle protein bound leucine enrichment during a primed continuous infusion of l-[1−13C]leucine. Biopsies were taken 30 min after the beginning of leucine infusion (when plasma 13C enrichment was steady), 240 min later during continued fasting and again after 240 min of infusion of a mixed amino acid solution which increased plasma total amino acid concentrations by 37%. The mean enrichment of 13C in plasma α-ketoisocaproate was used as an index of the enrichment of the precursor pool for leucine metabolism. 2. Anterior tibial muscle mixed protein synthetic rate during fasting was 0.055 (sd 0.008) %/h and this increased by an average of 35% during infusion of mixed amino acid to 0.074 (sd 0.021) %/h (P < 0.05). 3. Whole-body protein breakdown (expressed as the rate of endogenous leucine appearance in plasma) was 121 (sd 8) μmol h−1 kg−1 during fasting and decreased (P < 0.01) by an average of 12% during amino acid infusion. Leucine oxidation was 18 (sd 3) μmol h−1 kg−1 during fasting and increased (P < 0.001) by 89% during amino acid infusion. Whole-body protein synthesis (non-oxidative leucine disappearance) was 104 (sd 6) μmol h−1 kg−1 during fasting and rose by 13% (P < 0.001) during mixed amino acid infusion. 4. 13C enrichment of muscle free leucine was only 61 (sd 19) % of that in plasma α-ketoisocaproate and this increased to 74 (sd 16) % (P < 0.02) during mixed amino acid infusion. 5. The results suggest that increased availability of amino acids reverses whole-body protein balance from negative to positive and a major component of this is the increase in muscle protein synthesis.

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Abomasal amino acid infusion in postpartum dairy cows: Effect on whole-body, splanchnic, and mammary glucose metabolism

Journal of Dairy Science ◽

10.3168/jds.2014-9013 ◽

2015 ◽

Vol 98 (11) ◽

pp. 7962-7974 ◽

Cited By ~ 7

Author(s):

C. Galindo ◽

M. Larsen ◽

D.R. Ouellet ◽

G. Maxin ◽

D. Pellerin ◽

...

Keyword(s):

Amino Acid ◽

Glucose Metabolism ◽

Dairy Cows ◽

Whole Body ◽

Acid Infusion ◽

Amino Acid Infusion

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Effect of intravenous amino acids on glutamine and protein kinetics in low-birth-weight preterm infants during the immediate neonatal period

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.00274.2005 ◽

2006 ◽

Vol 290 (4) ◽

pp. E622-E630 ◽

Cited By ~ 33

Author(s):

Mark M. Kadrofske ◽

Prabhu S. Parimi ◽

Lourdes L. Gruca ◽

Satish C. Kalhan

Keyword(s):

Amino Acids ◽

Amino Acid ◽

De Novo ◽

Whole Body ◽

Preterm Neonates ◽

De Novo Synthesis ◽

Acid Infusion ◽

Amino Acid Infusion ◽

Amino Acid Load ◽

Acid Load

Glutamine may be a conditionally essential amino acid in low-birth-weight (LBW) preterm neonates. Exogenously administered amino acids, by providing anaplerotic carbon into the tricarboxylic acid cycle, could result in greater cataplerotic efflux and glutamine de novo synthesis. The effect of dose and duration of amino acid infusion on glutamine and nitrogen (N) kinetics was examined in LBW infants in the period immediately after birth. Preterm neonates (<32 weeks gestation, birth weights 809–1,755 g) were randomized to initially receive either 480 or 960 μmol·kg−1·h−1 of an intravenous amino acid solution for 19–24 hours, followed by a higher or lower amino acid load for either 5 h or 24 h. Glutamine de novo synthesis, leucine N, phenylalanine, and urea kinetics were determined using stable isotopic tracers. An increase in amino acid infusion from 480 to 960 μmol·kg−1·h−1 for 5 h resulted in decreased glutamine de novo synthesis in every neonate (384.4 ± 38.0 to 368.9 ± 38.2 μmol·kg−1·h−1, P < 0.01) and a lower whole body rate of proteolysis ( P < 0.001) and urea synthesis ( P < 0.001). However, when the increased amino acid infusion was extended for 24 h, glutamine de novo synthesis increased (369.7 ± 92.6 to 483.4 ± 97.5 μmol·kg−1·h−1, P < 0.001), whole body rate of proteolysis did not change, and urea production increased. Decreasing the amino acid load resulted in a decrease in glutamine rate of appearance (Ra) and leucine N Ra, but had no effect on phenylalanine Ra. Acutely stressed LBW infants responded to an increase in amino acid load by transiently suppressing whole body rate of glutamine synthesis, proteolysis, and oxidation of protein. The mechanisms of this transient effect on whole body protein/nitrogen metabolism remain unknown.

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