Reciprocal inhibition of in vitro substrate movement into avian skeletal muscle

Karen Sweazea, Eldon J. Braun

Research output: Contribution to journalArticlepeer-review

Abstract

Plasma glucose and ketone concentrations are much higher in birds than in humans and birds exhibit resistance to insulin-mediated glucose uptake into muscle. Therefore, birds may offer a model in which to examine the effects of high plasma glucose and free fatty acid (FFA) concentrations on substrate preference. The present study examined the uptake of radiolabeled oleic acid (OA; C18:1) and radiolabeled glucose by skeletal muscle isolated from the forewing of English sparrows (. Passer domesticus). In dose-response studies, unlabeled glucose and OA (20. mM each) inhibited the uptake of their respective radiolabeled counterparts. To examine the effects of glucose on OA uptake, muscles were incubated for 60. min in a buffer containing 20. mM glucose with the addition of radiolabeled OA. This level of glucose significantly decreased radiolabeled OA uptake by 36%. Using the same methodology, 20. mM OA significantly decreased radiolabeled glucose transport by 49%. Comparing control values for glucose (0.952. ±. 0.04. μM/mg muscle) and OA uptake (2.20. ±. 0.29. μM/mg muscle), it is evident that OA is preferentially taken up by avian skeletal muscle. As FFAs provide a greater amount of energy per mole (146 ATP/OA) than carbohydrates (36 ATP/glucose), storing and utilizing fats may be more energy-efficient for birds. As studies in mammals have shown that FFAs may impair glucose uptake pathways, it is suspected that high FFA uptake by avian skeletal muscle may induce their notably lower glucose transport.

Original languageEnglish (US)
Pages (from-to)85-89
Number of pages5
JournalZoology
Volume116
Issue number2
DOIs
StatePublished - Apr 1 2013

Keywords

  • Avian skeletal muscle
  • Fatty acid uptake
  • Glucose uptake
  • Insulin resistance
  • Muscle metabolism

ASJC Scopus subject areas

  • Animal Science and Zoology

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