Muscle performance depends on the supply of metabolic fuels and disposal of end-products. Using circulating metabolite concentrations to infer changes in fluxes is highly unreliable because the relationship between these parameters varies greatly with physiological state. Quantifying fuel kinetics directly is therefore crucial to the understanding of muscle metabolism. This review focuses on how @entity3363 , lipids and @entity3534 are provided to fish muscles during @entity519 and swimming. Both stresses force white muscle to produce @entity880 at higher rates than it can be processed by aerobic tissues. However, @entity880 accumulation is minimized because disposal is also strongly stimulated. Exogenous supply shows that trout have a much higher capacity to metabolize @entity880 than observed during @entity519 or intense swimming. The low density of @entity3338 transporters and their lack of upregulation with exercise explain the phenomenon of white muscle @entity880 retention. This tissue operates as a quasi-closed system, where glycogen stores act as an 'energy spring' that alternates between explosive power release during swimming and slow recoil from @entity880 in situ during recovery. To cope with exogenous @entity413 , trout can completely suppress hepatic production and boost @entity413 disposal. Without these responses, glycemia would increase four times faster and reach dangerous levels. The capacity of salmonids for glucoregulation is therefore much better than presently described in the literature. Instead of albumin-bound @entity1718 , fish use lipoproteins to shuttle energy from adipose tissue to working muscles during prolonged exercise. Proteins may play an important role in fueling muscle work in fish, but their exact contribution is yet to be established. The membrane pacemaker theory of metabolism accurately predicts general properties of muscle membranes such as unsaturation, but it does not explain allometric patterns of specific @entity1718 . Investigations of metabolic fuel kinetics carried out in fish to date have demonstrated that these ectotherms use several unique strategies to orchestrate energy supply to working muscles and to survive @entity519 .

Metabolic fuel kinetics in fish: swimming, XXXX and muscle membranes.

@entity3534 :: ('MESH:D000596', 'Chemical') :: ['amino acids'] @entity1718 :: ('MESH:D005227', 'Chemical') :: ['fatty acids'] @entity519 :: ('MESH:D000860', 'Disease') :: ['hypoxia'] @entity880 :: ('MESH:D019344', 'Chemical') :: ['lactate'] @entity413 :: ('MESH:D005947', 'Chemical') :: ['glucose'] @entity3338 :: ('CHEBI:35757', 'Chemical') :: ['monocarboxylate'] @entity3363 :: ('MESH:D002241', 'Chemical') :: ['carbohydrates']
@entity519 :: (MESH:D000860,Disease) :: ['hypoxia']
