Free fatty acid and glucose metabolism during increased energy expenditure and after training

Paul, Prabir Kumar; Holmes, William L.

doi:10.1249/00005768-197500730-00015

Cited by 15 publications

(10 citation statements)

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“…Material balance studies have demonstrated that fat is the major substrate used during the migratory flights of birds (Berthold 1975). However, studies of mammalian exercise have implicated carbohydrate as the limiting fuel for endurance exercise, even when fatty acids are the major fuel (Bergstrom and Hultman 1967; Paul and Holmes 1975). This limitation exists because oxidation of carbohydrate increases proportionally to the increase in metabolic rate (Paul and Hohnes 1975) and body stores of carbohydrate and gluconeogenic capacities are lim-ited (see Newsholme and Start 1973).…”

Section: Discussionmentioning

confidence: 99%

Catabolic enzyme activities in relation to premigratory fattening and muscle hypertrophy in the gray catbird (Dumetella carolinensis)

Marsh

1981

J Comp Physiol B

101

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The flight muscles of the gray catbird (Dumetella carolinensis) were examined to determine if short term adjustments occur in the activity of key catabolic enzymes during preparation for long distance migration. The aerobic capacity of the pectoralis muscle as indicated by citrate synthase activity (CS) is among the highest reported for skeletal muscle (200 ~tmoles [rain. g fresh mass]-1 at 25 ~ The mass specific aerobic capacity as indicated by CS activity or cytochrome c concentration does not change during premigratory fattening (Fig. 2) or in relation to the muscle hypertrophy that occurs concomitantly. The maintenance of mass specific aerobic capacity indicates that the total aerobic capacity increases in proportion to the increase in muscle size. The augmented potential for total aerobic power output is considered an adaptation to meet the increased power requirements of flight due to the increased body mass. Additionally, the capacity to oxidize fatty acids, as indicated by fl-hydroxyacyl-CoA dehydrogenase activity, approximately doubles during premigratory fattening (from 35 to 70 gmoles [min.g fresh mass] 1 at 25 ~ Fig. 1 A). This adaptation should favor fatty acid oxidation, thereby sparing carbohydrate and prolonging endurance. The activity of phosphofructokinase, a key glycolytic enzyme, does not change before migration.

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Section: Discussionmentioning

confidence: 99%

Catabolic enzyme activities in relation to premigratory fattening and muscle hypertrophy in the gray catbird (Dumetella carolinensis)

Marsh

1981

J Comp Physiol B

101

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show abstract

“…Free fatty acids transported through the blood are thought to be a readily oxidizable fuel in skeletal muscle. Adipose tissue is metabolically very active and can, by the rapid release of free fatty acids, Downloaded by [University of Otago] at 08:48 26 December 2014 provide fuel for muscle contraction (92). Rates of FFA mobilization from adipose depots and the FFA uptake by muscles are higher during exercise than at rest at any equivalent FFA level (55, 91, 92).…”

Section: Oxidative Energy Sourcesmentioning

confidence: 99%

“…The contribution of intramuscular energy substrates is large at the beginning of exercise but decreases as the exercise is prolonged, with up to 80% of the substrate to support energy expenditure eventually supplied through the circulation (90,91,92). A great deal of research has investigated the role of blood glucose in energy metabolism (9, 14, 60, 119, 120).…”

Section: Oxidative Energy Sourcesmentioning

confidence: 99%

“…A great deal of research has investigated the role of blood glucose in energy metabolism (9, 14, 60, 119, 120). T h e importance of blood glucose during exercise has been demonstrated: the development of hypoglycemia can limit work endurance (92). While liver-derived glucose is not a major source of energy for prolonged exercise, it does maintain blood glucose levels necessary for central nervous system metabolism (105).…”

Section: Oxidative Energy Sourcesmentioning

confidence: 99%

“…At heavy work loads lasting only a few minutes, the contribution of adipose tissue to total energy expenditure is negligible (92). During intermittent weight lifting over a 60-min period, no changes in blood levels of triglycerides o r free fatty acids have been observed (62).…”

Section: Oxidative Energy Sourcesmentioning

confidence: 99%

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