Regulation of Extramuscular Fuel Sources During Exercise

Wasserman, David H.; Cherrington, Alan D.

doi:10.1002/cphy.cp120123

Cited by 26 publications

(33 citation statements)

References 318 publications

(482 reference statements)

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“…Epinephrine is known to in¯uence glucose _ R a . Generally, it is thought that increases in the circulating concentration of EPI contribute to the rise in glucose _ R a observed during exercise (Wasserman and Cherrington 1996); however, it appears that other glucoregulatory hormones and/or metabolic signals are also important in the control of glucose _ R a ). We did not make measurements of catecholamines and other glucoregulatory hormones, for others have consistently and repeatedly shown that various doses of caeine lead to increased concentrations of EPI, both at rest and during exercise, despite the varying types, intensities, and durations of exercise (Graham and Spriet 1991;Bangsbo et al 1992;Spriet et al 1992;Jackman et al 1996).…”

Section: Discussionmentioning

confidence: 97%

An acute oral dose of caffeine does not alter glucose kinetics during prolonged dynamic exercise in trained endurance athletes

Roy

Bosman

Tarnopolsky

2001

European Journal of Applied Physiology

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This study investigated the possible influence of oral caffeine administration on endogenous glucose production and energy substrate metabolism during prolonged endurance exercise. Twelve trained endurance athletes [seven male, five female; peak oxygen consumption (VO2peak) = 65.5 ml.kg-1.min-1] performed 60 min of cycle ergometry at 65% VO2peak twice, once after oral caffeine administration (6 mg.kg-1) (CAF) and once following consumption of a placebo (PLA). CAF and PLA were administered in a randomized double-blind manner 75 min prior to exercise. Plasma glucose kinetics were determined with a primed-continuous infusion of [6,6-2H]glucose. No differences in oxygen consumption (VO2), and carbon dioxide production (VCO2) were observed between CAF and PLA, at rest or during exercise. Blood glucose concentrations were similar between the two conditions at rest and also during exercise. Exercise did lead to an increase in serum free fatty acid (FFA) concentrations for both conditions; however, no differences were observed between CAF and PLA. Both the plasma glucose rate of appearance (Ra) and disappearance (Rd) increased at the onset of exercise (P < 0.05), but were not affected by CAF, as compared to PLA. CAF did lead to a higher plasma lactate concentration during exercise (P < 0.05). It was concluded that an acute oral dose of caffeine does not influence plasma glucose kinetics or energy substrate oxidation during prolonged exercise in trained endurance athletes. However, CAF did lead to elevated plasma lactate concentrations. The exact mechanism of the increase in plasma lactate concentrations remains to be determined.

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Section: Discussionmentioning

confidence: 97%

An acute oral dose of caffeine does not alter glucose kinetics during prolonged dynamic exercise in trained endurance athletes

Roy

Bosman

Tarnopolsky

2001

European Journal of Applied Physiology

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“…After hard physical exercise, lactate released into the blood from muscles can be converted to glucose in the liver (Coggan 1991;Wasserman and Cherrington 1996). The threshold level of this compound (determined as the level of lactate concentration at which the animal cannot continue exercise and falls down) varies in different mammalian species .…”

Section: Introductionmentioning

confidence: 99%

Relationship of hepatocyte ploidy levels with body size and growth rate in mammals

Vinogradov

Anatskaya²,

Kudryavtsev³

2001

Genome

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To elucidate possible causes of the elevation of genome number in somatic cells, hepatocyte ploidy levels were measured cytofluorimetrically and related to the organismal parameters (body size, postnatal growth rate, and postnatal development type) in 53 mammalian species. Metabolic scope (ratio of maximal metabolic rate to basal metabolic rate) was also included in 23 species. Body masses ranged 10(5) times, and growth rate more than 30 times. Postnatal growth rate was found to have the strongest effect on the hepatocyte ploidy. At a fixed body mass the growth rate closely correlates (partial correlation analysis) with the cell ploidy level (r = 0.85, P < 10(-6)), whereas at a fixed growth rate body mass correlates poorly with ploidy level (r = -0.38, P < 0.01). The mature young (precocial mammals) of the species have, on average, a higher cell ploidy level than the immature-born (altricial) animals. However, the relationship between precocity of young and cell ploidy levels disappears when the influences of growth rate and body mass are removed. Interspecies variability of the hepatocyte ploidy levels may be explained by different levels of competition between the processes of proliferation and differentiation in cells. In turn, the animal differences in the levels of this competition are due to differences in growth rate. A high negative correlation between the hepatocyte ploidy level and the metabolic scope indicates a low safety margin of organs with a high number of polyploid cells. This fact allows us to challenge a common opinion that increasing ploidy enhances the functional capability of cells or is necessary for cell differentiation. Somatic polyploidy can be considered a "cheap" solution of growth problems that appear when an organ is working at the limit of its capabilities.

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“…delivery during exercise by activating liver glucose production with decreased insulin, increased glucagon, and catecholamines, as well as enhanced availability of gluconeogenic precursors, glutamine, and alanine (1,30,36).…”

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confidence: 99%

Carbohydrate metabolism during prolonged exercise and recovery: interactions between pyruvate dehydrogenase, fatty acids, and amino acids

Mourtzakis¹,

Saltin²,

Graham³

et al. 2006

Journal of Applied Physiology

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Mourtzakis, Marina, Bengt Saltin, Terry Graham, and Henriette Pilegaard. Carbohydrate metabolism during prolonged exercise and recovery: interactions between pyruvate dehydrogenase, fatty acids, and amino acids. J Appl Physiol 100: 1822-1830, 2006. First published January 19, 2006 doi:10.1152/japplphysiol.00571.2005.-During prolonged exercise, carbohydrate oxidation may result from decreased pyruvate production and increased fatty acid supply and ultimately lead to reduced pyruvate dehydrogenase (PDH) activity. Pyruvate also interacts with the amino acids alanine, glutamine, and glutamate, whereby the decline in pyruvate production could affect tricarboxycylic acid cycle flux as well as gluconeogenesis. To enhance our understanding of these interactions, we studied the time course of changes in substrate utilization in six men who cycled at 44 Ϯ 1% peak oxygen consumption (mean Ϯ SE) until exhaustion (exhaustion at 3 h 23 min Ϯ 11 min). Femoral arterial and venous blood, blood flow measurements, and muscle samples were obtained hourly during exercise and recovery (3 h). Carbohydrate oxidation peaked at 30 min of exercise and subsequently decreased for the remainder of the exercise bout (P Ͻ 0.05). PDH activity peaked at 2 h of exercise, whereas pyruvate production peaked at 1 h of exercise and was reduced (ϳ30%) thereafter, suggesting that pyruvate availability primarily accounted for reduced carbohydrate oxidation. Increased free fatty acid uptake (P Ͻ 0.05) was also associated with decreasing PDH activity (P Ͻ 0.05) and increased PDH kinase 4 mRNA (P Ͻ 0.05) during exercise and recovery. At 1 h of exercise, pyruvate production was greatest and was closely linked to glutamate, which was the predominant amino acid taken up during exercise and recovery. Alanine and glutamine were also associated with pyruvate metabolism, and they comprised ϳ68% of total amino-acid release during exercise and recovery. Thus reduced pyruvate production was primarily associated with reduced carbohydrate oxidation, whereas the greatest production of pyruvate was related to glutamate, glutamine, and alanine metabolism in early exercise. alanine; pyruvate dehydrogenase kinase 4 mMRNA; carbohydrate oxidation; nitrogen balance THE REGULATION OF CARBOHYDRATE provision during prolonged exercise and recovery is a profound challenge for the human body. Muscle carbohydrate metabolism does not happen in isolation but requires integration across tissues as well as regulation with the other major substrates, such as fats and amino acids. Because carbohydrate stores are limited in the body (i.e., muscle, liver), the highly coordinated integration of liver, adipose tissue, pancreas, and muscle metabolism is important for constant energy provision during prolonged exercise (1, 30, 34 -36) and in reestablishing homeostasis during recovery (2). Arterial glucose delivery is one key element in energy provision, and the body attempts to maintain glucose delivery during exercise by activating liver glucose production with decreased insulin, increased gl...

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Regulation of Extramuscular Fuel Sources During Exercise

Abstract: The sections in this article are: Fuel Requirements of the Working Muscle Effect of Exercise Duration Effect of Exercise Intensity Exercise Responses of Hormones and Nerves Involved in Acute Metabolic Regulation Insulin Response Glucagon Response Catecholamine Responses … Show more

Cited by 26 publications

References 318 publications

An acute oral dose of caffeine does not alter glucose kinetics during prolonged dynamic exercise in trained endurance athletes

An acute oral dose of caffeine does not alter glucose kinetics during prolonged dynamic exercise in trained endurance athletes

Relationship of hepatocyte ploidy levels with body size and growth rate in mammals

Carbohydrate metabolism during prolonged exercise and recovery: interactions between pyruvate dehydrogenase, fatty acids, and amino acids

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