Lessons from an estivating frog: sparing muscle protein despite starvation and disuse

Hudson, N. J., Lehnert, S. A., Ingham, A. B., Symonds, B., Franklin, C. E. and Harper, G. S. (2006) Lessons from an estivating frog: sparing muscle protein despite starvation and disuse. American Journal of Physiology-regulatory Integrative And Comparative Physiology, 290 3: R836-R843. doi:10.1152/ajpregu.00380.2005


Author Hudson, N. J.
Lehnert, S. A.
Ingham, A. B.
Symonds, B.
Franklin, C. E.
Harper, G. S.
Title Lessons from an estivating frog: sparing muscle protein despite starvation and disuse
Journal name American Journal of Physiology-regulatory Integrative And Comparative Physiology   Check publisher's open access policy
ISSN 0363-6119
Publication date 2006-01-01
Year available 2006
Sub-type Article (original research)
DOI 10.1152/ajpregu.00380.2005
Open Access Status Not yet assessed
Volume 290
Issue 3
Start page R836
End page R843
Total pages 8
Place of publication Bethesda
Publisher American Physiological Society
Language eng
Subject C1
Abstract Long (6- to 9-mo) bouts of estivation in green-striped burrowing frogs lead to 28% atrophy of cruralis oxidative fibers (P < 0.05) and some impairment of in vitro gastrocnemius endurance (P < 0.05) but no significant deficit in maximal twitch force production. These data suggest the preferential atrophy of oxidative fibers at a rate slower than, but comparable to, laboratory disuse models. We tested the hypothesis that the frog limits atrophy by modulating oxidative stress. We assayed various proteins at the transcript level and verified these results for antioxidant enzymes at the biochemical level. Transcript data for NADH ubiquinone oxidoreductase subunit 1 (71% downregulated, P < 0.05) and ATP synthase (67% downregulated, P < 0.05) are consistent with mitochondrial quiescence and reduced oxidant production. Meanwhile, uncoupling protein type 2 transcription (P < 0.31), which is thought to reduce mitochondrial leakage of reactive oxygen species, was maintained. Total antioxidant defense of water-soluble (22.3 +/- 1.7 and 23.8 +/- 1.5 mu M/mu g total protein in control and estivator, respectively, P = 0.53) and membrane-bound proteins (31.5 +/- 1.9 and 42.1 +/- 7.3 mu M/mu g total protein in control and estivator, respectively, P = 0.18) was maintained, equivalent to a bolstering of defense relative to oxygen insult. This probably decelerates muscle atrophy by preventing accumulation of oxidative damage in static protein reserves. Transcripts of the mitochondrially encoded antioxidant superoxide dismutase type 2 ( 67% downregulated, P < 0.05) paralleled mitochondrial activity, whereas nuclear-encoded catalase and glutathione peroxidase were maintained at control values (P = 0.42 and P = 0.231), suggesting a dissonance between mitochondrial and nuclear antioxidant expression. Pyruvate dehydrogenase kinase 4 transcription was fourfold lower in estivators (P = 0.11), implying that, in contrast to mammalian hibernators, this enzyme does not drive the combustion of lipids that helps spare hypometabolic muscle.
Keyword Disuse Atrophy
Antioxidant
Mitochondria
Gene Expression
Physiology
Hibernating Ground-squirrels
Skeletal-muscle
Oxidative Stress
Mammalian Hibernation
Cyclorana-alboguttata
Burrowing Frog
Immobilization
Gene
Expression
Periods
Q-Index Code C1
Institutional Status UQ

 
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Created: Wed, 15 Aug 2007, 18:53:35 EST