Effects of carbohydrate feedings on plasma free tryptophan and branched-chain amino acids during prolonged cycling

Davis, John M.; Bailey, Stephen P.; Woods, Jeffrey A.; Galiano, Floyd; Hamilton, Marc T.; Bartoli, W. P.

doi:10.1007/bf00602357

Cited by 168 publications

(134 citation statements)

References 30 publications

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“…It has been reported that leptin production is not changed by short-term exercise (12,30). We can suggest that our observation in this study is similar, because no changes in leptin were seen during shortterm exercise.…”

Section: Discussionsupporting

confidence: 85%

“…The brain may detect changes in the normal levels of the constituents of the blood, such as the concentration ratio of tryptophan to branched-chain amino acids (4,6,7,11,12,(26)(27)(28)(29), which can then act as a specific signal to increase the organism's sensitivity to fatigue. However, little is known about the counteractive effects of the central nervous system (CNS) on peripheral energy metabolism.…”

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confidence: 99%

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Intracranial administration of transforming growth factor-β3 increases fat oxidation in rats

Yamazaki

Arai

Matsumura

et al. 2002

American Journal of Physiology-Endocrinology and Metabolism

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Yamazaki, Hanae, Masanao Arai, Shigenobu Matsumura, Kazuo Inoue, and Tohru Fushiki. Intracranial administration of transforming growth factor-␤3 increases fat oxidation in rats. Am J Physiol Endocrinol Metab 283: E536-E544, 2002. First published May 28, 2002 10.1152/ ajpendo.00094.2001.-The effects of intracranial transforming growth factor (TGF)-␤3 on spontaneous motor activity and energy metabolism were examined in rats. After injection of TGF-␤3 into the cisterna magna of the rat, spontaneous motor activity decreased significantly for 1 h. The intracranial injection of TGF-␤3 produced an immediate decrease in respiratory exchange ratio (RER). No significant changes were observed in energy expenditure. TGF-␤3 induced a significant increase in total fat oxidation and a decrease in total carbohydrate oxidation. Furthermore, the serum substrates associated with fat metabolism were significantly altered in rats injected with TGF-␤3. Both lipoprotein lipase activity in skeletal muscle and the concentration of serum ketone bodies increased, suggesting that the increase in fat oxidation caused by TGF-␤3 may have occurred in the liver and muscle. Intracranial injection of TGF-␤3 appeared to evoke a switch in the energy substrates accessed in energy expenditure. These results suggest that the release of TGF-␤3 in the brain by exercise is a signal for regulating energy consumption. spontaneous motor activity; respiratory exchange ratio; energy metabolism WE HAVE PREVIOUSLY REPORTED that intracranial administration of cerebrospinal fluid (CSF) from exerciseexhausted rats produced a decrease in spontaneous motor activity, whereas CSF from sedentary rats had no such effect (19).

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Section: Discussionsupporting

confidence: 85%

mentioning

confidence: 99%

Intracranial administration of transforming growth factor-β3 increases fat oxidation in rats

Yamazaki

Arai

Matsumura

et al. 2002

American Journal of Physiology-Endocrinology and Metabolism

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“…Central fatigue is aggravated by hyperthermia (47,48), but the neurobiological mechanism(s) underlying this type of fatigue is unknown. Special attention has been given to the synthesis and metabolism of serotonin (5-hydroxytryptamine), because of its role in arousal, sleepiness, and mood (5,13,15,42,51). Cerebral serotonin kinetics cannot be assessed directly in humans, because its passage across the blood-brain barrier is limited (27).…”

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confidence: 99%

Neurohumoral responses during prolonged exercise in humans

Nybo¹,

Nielsen²,

Blomstrand³

et al. 2003

Journal of Applied Physiology

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.-This study examined neurohumoral alterations during prolonged exercise with and without hyperthermia. The cerebral oxygen-to-carbohydrate uptake ratio (O 2/CHO ϭ arteriovenous oxygen difference divided by arteriovenous glucose difference plus one-half lactate), the cerebral balances of dopamine, and the metabolic precursor of serotonin, tryptophan, were evaluated in eight endurance-trained subjects during exercise randomized to be with or without hyperthermia. The core temperature stabilized at 37.9 Ϯ 0.1°C (mean Ϯ SE) in the control trial, whereas it increased to 39.7 Ϯ 0.2°C in the hyperthermic trial, with a concomitant increase in perceived exertion (P Ͻ 0.05). At rest, the brain had a small release of tryptophan (arteriovenous difference of Ϫ1.2 Ϯ 0.3 mol/l), whereas a net balance was obtained during the two exercise trials. Both the arterial and jugular venous dopamine levels became elevated during the hyperthermic trial, but the net release from the brain was unchanged. During exercise, the O2/CHO was similar across trials, but, during recovery from the hyperthermic trial, the ratio decreased to 3.8 Ϯ 0.3 (P Ͻ 0.05), whereas it returned to the baseline level of ϳ6 within 5 min after the control trial. The lowering of O2/CHO was established by an increased arteriovenous glucose difference (1.1 Ϯ 0.1 mmol/l during recovery from hyperthermia vs. 0.7 Ϯ 0.1 mmol/l in control; P Ͻ 0.05). The present findings indicate that the brain has an increased need for carbohydrates during recovery from strenuous exercise, whereas enhanced perception of effort as observed during exercise with hyperthermia was not related to alterations in the cerebral balances of dopamine or tryptophan.brain; dopamine; hyperthermia; tryptophan ALTHOUGH FATIGUE MAY RELATE to both peripheral (muscular) and central factors (4, 31, 52), attention has primarily been on the association to muscular factors. Hypotheses have connected central fatigue with alterations in the cerebral level of different neurotransmitters, but the cerebral balances of these neurotransmitters, their precursors, or metabolites have actually never been determined during prolonged exercise in humans. Central fatigue is aggravated by hyperthermia (47, 48), but the neurobiological mechanism(s) underlying this type of fatigue is unknown. Special attention has been given to the synthesis and metabolism of serotonin (5-hydroxytryptamine), because of its role in arousal, sleepiness, and mood (5, 13, 15, 42, 51). Cerebral serotonin kinetics cannot be assessed directly in humans, because its passage across the blood-brain barrier is limited (27). However, determination of the cerebral uptake of tryptophan (TRP), the precursor for the synthesis of serotonin, may provide an indication of changes in the serotonin level within the brain, because transport of TRP into the brain is the ratelimiting step in the synthesis of serotonin (5, 20). Some support for the involvement of serotonin in fatigue is obtained from studies that have attempted to alter the cerebral serotonin level by me...

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“…Because carbohydrate ingestion has also been shown to reduce the availability of free tryptophan and to improve endurance for prolonged exercise (18), we also determined whether combined tyrosine and carbohydrate supplementation has a greater beneficial effect on endurance than either one alone.…”

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confidence: 99%

Effects of l-tyrosine and carbohydrate ingestion on endurance exercise performance

Chinevere

Sawyer

Creer

et al. 2002

Journal of Applied Physiology

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To test the effects of tyrosine ingestion with or without carbohydrate supplementation on endurance performance, nine competitive cyclists cycled at 70% peak oxygen uptake for 90 min under four different feeding conditions followed immediately by a time trial. At 30-min intervals, beginning 60 min before exercise, each subject consumed either 5 ml/kg body wt of water sweetened with aspartame [placebo (Pla)], polydextrose (70 g/l) (CHO), L-tyrosine (25 mg/kg body wt) (Tyr), or polydextrose (70 g/l) and L-tyrosine (25 mg/kg body wt) (CHOϩTyr). The experimental trials were given in random order and were carried out by using a counterbalanced double-blind design. No differences were found between treatments for oxygen uptake, heart rate, or rating of perceived exertion at any time during the 90-min ride. Plasma tyrosine rose significantly from 60 min before exercise to test termination (TT) in Tyr (means Ϯ SE) (480 Ϯ 26 mol) and CHOϩTyr (463 Ϯ 34 mol) and was significantly higher in these groups from 30 min before exercise to TT vs. CHO (90 Ϯ 3 mol) and Pla (111 Ϯ 7 mol) (P Ͻ 0.05). Plasma free tryptophan was higher after 90 min of exercise, 15 min into the endurance time trial, and at TT in Tyr (10.1 Ϯ 0.9, 10.4 Ϯ 0.8, and 12.0 Ϯ 0.9 mol, respectively) and Pla (9.7 Ϯ 0.5, 10.0 Ϯ 0.3, and 11.7 Ϯ 0.5 mol, respectively) vs. CHO (7.8 Ϯ 0.5, 8.6 Ϯ 0.5, and 9.3 Ϯ 0.6 mol, respectively) and CHOϩTyr (7.8 Ϯ 0.5, 8.5 Ϯ 0.5, 9.4 Ϯ 0.5 mol, respectively) (P Ͻ 0.05). The plasma tyrosine-to-free tryptophan ratio was significantly higher in Tyr and CHOϩTyr vs. CHO and Pla from 30 min before exercise to TT (P Ͻ 0.05). CHO (27.1 Ϯ 0.9 min) and CHOϩTyr (26.1 Ϯ 1.1 min) treatments resulted in a reduced time to complete the endurance time trial compared with Pla (34.4 Ϯ 2.9 min) and Tyr (32.6 Ϯ 3.0 min) (P Ͻ 0.05). These findings demonstrate that tyrosine ingestion did not enhance performance during a cycling time trial after 90 min of steady-state exercise. central fatigue; cycling; perceived exertion RECENTLY, IT HAS BEEN HYPOTHESIZED that, during prolonged exercise, an increased concentration of brain serotonin may be an important factor in the onset of central nervous system fatigue (2-4, 8, 10, 27) and a high serotonin-to-dopamine ratio results in fatigue (17). Brain serotonin synthesis depends on the availability of free tryptophan, its amino acid precursor, and the activity of the rate-limiting enzyme, tryptophan hydroxylase (7, 10). Similarly, tyrosine is the amino acid precursor to dopamine (32). These amino acid precursors compete for transport across the bloodbrain barrier via the same carrier mechanism (17).We speculated that, if tyrosine were elevated in the blood by ingestion during exercise and competed for transport across the blood brain barrier with tryptophan, increased uptake of tyrosine and a decreased uptake of tryptophan could result in a lower brain serotonin/dopamine ratio and improved endurance.Limited research has been done on the effects of tyrosine ingestion on exercise endurance. Struder et al. (30) rep...

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Effects of carbohydrate feedings on plasma free tryptophan and branched-chain amino acids during prolonged cycling

Cited by 168 publications

References 30 publications

Intracranial administration of transforming growth factor-β3 increases fat oxidation in rats

Intracranial administration of transforming growth factor-β3 increases fat oxidation in rats

Neurohumoral responses during prolonged exercise in humans

Effects of l-tyrosine and carbohydrate ingestion on endurance exercise performance

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