Plasma amino acid and ammonia responses to altered dietary intakes prior to prolonged exercise in humans

1992 ◽  
Vol 70 (4) ◽  
pp. 420-427 ◽  
Author(s):  
D. A. MacLean ◽  
L. L. Spriet ◽  
T. E. Graham
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Prolonged Exercise ◽  
Plasma Concentrations ◽  
Latin Square ◽  
Branched Chain Amino Acids ◽  
Dietary Intakes ◽  
Rate Of Increase ◽  
Branched Chain ◽  
Exercise In Humans

This study examined the effects of altered dietary intakes on amino acid and ammonia (NH3) responses prior to and during prolonged exercise in humans. Six male recreational cyclists rode to exhaustion at 75% of [Formula: see text] following 3 days on a low carbohydrate (LC), mixed (M), or high carbohydrate (HC) diet in a latin square design. There were differences (p < 0.05) in exercise times among all treatments (58.8 ± 3.7, 112.1 ± 7.3, and 152.9 ± 10.3 min for the LC, M, and HC treatments, respectively). The rate of increase in plasma NH3 during exercise was greater (p < 0.05) during the LC trial. The LC trial was also characterized by higher (p < 0.05) resting plasma concentrations of branched chain amino acids (BCAA) and a greater decrease in these amino acids during exercise (p < 0.05), as compared with the other two treatments. Both plasma BCAA and NH3 were susceptible to dietary manipulations. These findings suggest that limited carbohydrate availability in association with increased BCAA availability results in enhanced BCAA metabolism during exercise. This is reflected in a greater rate of increase in plasma NH3 and is consistent with the hypothesis that a significant fraction of the NH3 released during a prolonged, submaximal exercise bout is from amino acid catabolism.Key words: AMP deaminase, branched chain amino acids, branched chain keto acid dehydrogenase, glycogen, purine nucleotide cycle.

Amino acid metabolism in the Zucker diabetic fatty rat: effects of insulin resistance and of type 2 diabetes

2004 ◽  
Vol 82 (7) ◽  
pp. 506-514 ◽  
Author(s):  
Enoka P Wijekoon ◽  
Craig Skinner ◽  
Margaret E Brosnan ◽  
John T Brosnan
Keyword(s):  
Insulin Resistance ◽  
Amino Acids ◽  
Amino Acid ◽  
Amino Acid Metabolism ◽  
Acid Metabolism ◽  
Plasma Concentrations ◽  
Branched Chain Amino Acids ◽  
Insulin Resistant ◽  
Branched Chain

We investigated amino acid metabolism in the Zucker diabetic fatty (ZDF Gmi fa/fa) rat during the prediabetic insulin-resistant stage and the frank type 2 diabetic stage. Amino acids were measured in plasma, liver, and skeletal muscle, and the ratios of plasma/liver and plasma/skeletal muscle were calculated. At the insulin-resistant stage, the plasma concentrations of the gluconeogenic amino acids aspartate, serine, glutamine, glycine, and histidine were decreased in the ZDF Gmi fa/fa rats, whereas taurine, α-aminoadipic acid, methionine, phenylalanine, tryptophan, and the 3 branched-chain amino acids were significantly increased. At the diabetic stage, a larger number of gluconeogenic amino acids had decreased plasma concentrations. The 3 branched-chain amino acids had elevated plasma concentrations. In the liver and the skeletal muscles, concentrations of many of the gluconeogenic amino acids were lower at both stages, whereas the levels of 1 or all of the branched-chain amino acids were elevated. These changes in amino acid concentrations are similar to changes seen in type 1 diabetes. It is evident that insulin resistance alone is capable of bringing about many of the changes in amino acid metabolism observed in type 2 diabetes.Key words: plasma amino acids, liver amino acids, muscle amino acids, gluconeogenesis.

scholarly journals Interactions among the branched-chain amino acids and their effects on methionine utilization in growing pigs: effects on plasma amino– and keto–acid concentrations and branched-chain keto-acid dehydrogenase activity

2000 ◽  
Vol 83 (1) ◽  
pp. 49-58 ◽  
Author(s):  
Stefan Langer ◽  
Peter W. D. Scislowski ◽  
David S. Brown ◽  
Peter Dewey ◽  
Malcolm F. Fuller
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Plasma Concentrations ◽  
Biceps Femoris ◽  
Branched Chain Amino Acids ◽  
Growing Pigs ◽  
Keto Acid ◽  
Blood Samples ◽  
Acid Dehydrogenase ◽  
Branched Chain

The present experiment was designed to elucidate the mechanism of the methionine-sparing effect of excess branched-chain amino acids (BCAA) reported in the previous paper (Langer & Fuller, 2000). Twelve growing gilts (30–35 kg) were prepared with arterial catheters. After recovery, they received for 7 d a semipurified diet with a balanced amino acid pattern. On the 7th day blood samples were taken before (16 h postabsorptive) and after the morning meal (4 h postprandial). The animals were then divided into three groups and received for a further 7 d a methionine-limiting diet (80 % of requirement) (1) without any amino acid excess; (2) with excess leucine (50 % over requirement); or (3) with excesses of all three BCAA (leucine, isoleucine, valine, each 50 % over the requirement). On the 7th day blood samples were taken as in the first period, after which the animals were killed and liver and muscle samples taken. Plasma amino acid and branched-chain keto acid (BCKA) concentrations in the blood and branched-chain keto-acid dehydrogenase (BCKDH; EC 1.2.4.4) activity in liver and muscle homogenates were determined. Compared with those on the balanced diet, pigs fed on methionine-limiting diets had significantly lower (P < 0·05) plasma methionine concentrations in the postprandial but not in the postabsorptive state. There was no effect of either leucine or a mixture of all three BCAA fed in excess on plasma methionine concentrations. Excess dietary leucine reduced (P < 0·05) the plasma concentrations of isoleucine and valine in both the postprandial and postabsorptive states. Plasma concentrations of the BCKA reflected the changes in the corresponding amino acids. Basal BCKDH activity in the liver and total BCKDH activity in the biceps femoris muscle were significantly (P < 0·05) increased by excesses of leucine or all BCAA.

scholarly journals Amino acid catabolism by perfused rat hindquarter. The metabolic fates of valine

1986 ◽  
Vol 233 (3) ◽  
pp. 621-630 ◽  
Author(s):  
S H C Lee ◽  
E J Davis
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Degradation Products ◽  
Plasma Concentrations ◽  
Branched Chain Amino Acids ◽  
Total Amino Acid ◽  
Amino Acid Catabolism ◽  
Citrate Cycle ◽  
Important Intermediate ◽  
Branched Chain

Hindquarters from starved rats were perfused with plasma concentrations of amino acids, but without other added substrates. Release of amino acids was similar to that previously reported, but, if total amino acid changes were recorded, alanine and glutamine were not formed in excess of their occurrence in muscle proteins. In protein balance (excess insulin) there was no net formation of either alanine or glutamine, even though the branched-chain amino acids and methionine were consumed. If [U-14C]valine was present, radiolabelled 3-hydroxyisobutyrate and, to a lesser extent, 2-oxo-3-methylbutyrate accumulated and radiolabel was incorporated into citrate-cycle intermediates and metabolites closely associated with the citrate cycle (glutamine and glutamate, and, to a smaller extent, lactate and alanine). If a 2-chloro-4-methylvalerate was present to stimulate the branched-chain oxo acid dehydrogenase, flux through this step was accelerated, resulting in increased accumulation of 3-hydroxyisobutyrate, decreased accumulation of 2-oxo-3-methylbutyrate, and markedly increased incorporation of radiolabel (specific and total) into all measured metabolites formed after 3-hydroxyisobutyrate. It is concluded that: amino acid catabolism by skeletal muscle is confined to degradation of the branched-chain amino acids, methionine and those that are interconvertible with the citrate cycle; amino acid catabolism is relatively minor in supplying carbon for net synthesis of alanine and glutamine; and partial degradation products of the branched-chain amino acids are quantitatively significant substrates released from muscle for hepatic gluconeogenesis. For valine, 3-hydroxyisobutyrate appears to be quantitatively the most important intermediate released from muscle. A side path for inter-organ disposition of the branched-chain amino acids is proposed.

scholarly journals A Novel Dietary Intervention Reduces Circulatory Branched-Chain Amino Acids by 50%: A Pilot Study of Relevance for Obesity and Diabetes

Nutrients ◽  
2020 ◽  
Vol 13 (1) ◽  
pp. 95
Author(s):  
Imran Ramzan ◽  
Moira Taylor ◽  
Beth Phillips ◽  
Daniel Wilkinson ◽  
Kenneth Smith ◽  
...  
Keyword(s):  
Amino Acids ◽  
Pilot Study ◽  
Dietary Intervention ◽  
Control Diet ◽  
Branched Chain Amino Acids ◽  
Model Assessment ◽  
Dietary Intakes ◽  
Restricted Diet ◽  
Obesity And Diabetes ◽  
Branched Chain

Elevated circulating branched-chain amino acids (BCAAs; isoleucine, leucine, and valine) are associated with obesity and type 2 diabetes (T2D). Reducing circulatory BCAAs by dietary restriction was suggested to mitigate these risks in rodent models, but this is a challenging paradigm to deliver in humans. We aimed to design and assess the feasibility of a diet aimed at reducing circulating BCAA concentrations in humans, while maintaining energy balance and overall energy/protein intake. Twelve healthy individuals were assigned to either a 7-day BCAA-restricted diet or a 7-day control diet. Diets were iso-nitrogenous and iso-caloric, with only BCAA levels differing between the two. The BCAA-restricted diet significantly reduced circulating BCAA concentrations by ~50% i.e., baseline 437 ± 60 to 217 ± 40 µmol/L (p < 0.005). Individually, both valine (245 ± 33 to 105 ± 23 µmol/L; p < 0.0001), and leucine (130 ± 20 to 75 ± 13 µmol/L; p < 0.05), decreased significantly in response to the BCAA-restricted diet. The BCAA-restricted diet marginally lowered Homeostatic Model Assessment of Insulin Resistance (HOMA-IR) levels: baseline 1.5 ± 0.2 to 1.0 ± 0.1; (p = 0.096). We successfully lowered circulating BCAAs by 50% while maintaining iso-nitrogenous, iso-caloric dietary intakes, and while meeting the recommended daily allowances (RDA) for protein requirements. The present pilot study represents a novel dietary means by which to reduce BCAA, and as such, provides a blueprint for a potential dietary therapeutic in obesity/diabetes.

scholarly journals Metabolic effects of low cortisol during exercise in humans

1998 ◽  
Vol 84 (3) ◽  
pp. 939-947 ◽  
Author(s):  
Pedro Del Corral ◽  
Edward T. Howley ◽  
Mike Hartsell ◽  
Muhammad Ashraf ◽  
Mary Sue Younger
Keyword(s):  
Amino Acids ◽  
Growth Hormone ◽  
Plasma Glucose ◽  
Respiratory Exchange Ratio ◽  
Branched Chain Amino Acids ◽  
Physiological Effect ◽  
Metabolic Effects ◽  
Whole Body ◽  
Branched Chain ◽  
Exercise In Humans

This study examined the physiological effect of reduced plasma cortisol (C) during prolonged exercise in humans. The effects of normal C (NC) were compared with metyrapone-induced low C (LC) on plasma substrate availability and the respiratory exchange ratio during 2 h of exercise at ∼60% peak O2 consumption in nine subjects. The C responses were compared with preexercise (Pre) levels and with a rest day (Con). At rest, C was attenuated by ∼70% for LC compared with NC. At rest, plasma glucose, lactate, glycerol, β-hydroxybutyrate, alanine, branched-chain amino acids, insulin, glucagon, growth hormone, epinephrine, and norepinephrine were similar under LC and NC ( P > 0.05). During exercise under NC, plasma C increased compared with Pre, whereas it remained unchanged during LC. During NC, plasma C was elevated at 90 min (compared with Con) and at 120 min (compared with Con and Pre). During exercise, plasma glucose decreased to the same extent and lactate was similar under both conditions, whereas plasma glycerol, β-hydroxybutyrate, alanine, and branched-chain amino acids were higher ( P < 0.01) under NC. Plasma insulin declined ( P = 0.01) to a greater extent under LC, whereas growth hormone, epinephrine, and norepinephrine tended to be higher (0.05 ≤ P ≤ 0.10). Plasma glucagon increased under both conditions ( P < 0.01). The respiratory exchange ratio did not differ between conditions. We conclude that, during exercise, 1) C accelerates lipolysis, ketogenesis, and proteolysis; 2) under LC, glucoregulatory hormone adjustments maintain glucose homeostasis; and 3) LC does not alter whole body substrate utilization or the ability to complete 2 h of moderate exercise.

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