title: Temperature- and exercise-induced gene expression and metabolic enzyme changes in skeletal muscle of adult zebrafish (Danio rerio).
abstract: Both exercise training and cold acclimatization induce muscle remodelling in vertebrates, producing a more aerobic phenotype. In ectothermic species exercise training and cold-acclimatization represent distinct stimuli. It is currently unclear if these stimuli act through a common mechanism or if different mechanisms lead to a common phenotype. The goal of this study was to survey responses that represent potential mechanisms responsible for contraction- and temperature-induced muscle remodelling, using an ectothermic vertebrate. Separate groups of adult zebrafish (Danio rerio) were either swim trained or cold acclimatized for 4 weeks. We found that the mitochondrial marker enzyme citrate synthase (CS) was increased by 1.5x in cold and by 1.3x with exercise (P<0.05). Cytochrome c oxidase (COx) was increased by 1.2x following exercise training (P<0.05) and 1.2x (P=0.07) with cold acclimatization. However, only cold acclimatization increased beta-hydroxyacyl-CoA dehydrogenase (HOAD) compared to exercise-trained (by 1.3x) and pyruvate kinase (PK) relative to control zebrafish. We assessed the whole-animal performance outcomes of these treatments. Maximum absolute sustained swimming speed (Ucrit) was increased in the exercise trained group but not in the cold acclimatized group. Real-time PCR analysis indicated that increases in CS are primarily transcriptionally regulated with exercise but not with cold treatments. Both treatments showed increases in nuclear respiratory factor (NRF)-1 mRNA which was increased by 2.3x in cold-acclimatized and 4x in exercise-trained zebrafish above controls. In contrast, peroxisome proliferator-activated receptor (PPAR)-alpha mRNA levels were decreased in both experimental groups while PPAR-beta1 declined in exercise training only. Moreover, PPAR-gamma coactivator (PGC)-1alpha mRNA was not changed by either treatment. In zebrafish, both temperature and exercise produce a more aerobic phenotype, but there are stimulus-dependent responses (i.e. HOAD and PK activities). While similar changes in NRF-1 mRNA suggest that common responses might underlie aerobic muscle remodelling there are distinct changes (i.e. CS and PPAR-beta1 mRNA) that contribute to specific temperature- and exercise-induced phenotypes.
authors.affiliation: Department of Biology, McMaster University, 1280 Main Street West, Hamilton, ON L8S 4K1, Canada. grantm@mcmaster.ca
authors.forename: Grant B
authors.initials: GB
authors.lastname: McClelland
authors.forename: Paul M
authors.initials: PM
authors.lastname: Craig
authors.forename: Kalindi
authors.initials: K
authors.lastname: Dhekney
authors.forename: Shawn
authors.initials: S
authors.lastname: Dipardo
mesh_terms: D015094:3-Hydroxyacyl CoA Dehydrogenases / Q000378:metabolism; D000064:Acclimatization / Q000502:physiology*; D000818:Animals; D002950:Citrate (si)-Synthase / Q000378:metabolism; D003080:Cold Temperature; D003576:Electron Transport Complex IV / Q000378:metabolism; D005136:Eye Proteins / Q000378:metabolism; D015971:Gene Expression Regulation, Enzymologic; D018763:Muscle Fatigue; D018482:Muscle, Skeletal / Q000201:enzymology* / Q000378:metabolism; D051266:Nuclear Respiratory Factor 1 / Q000378:metabolism; D047492:Peroxisome Proliferator-Activated Receptors / Q000378:metabolism; D010641:Phenotype; D010805:Physical Conditioning, Animal / Q000502:physiology*; D016133:Polymerase Chain Reaction; D011770:Pyruvate Kinase / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D013997:Time Factors; D015027:Zebrafish / Q000378:metabolism*; D029961:Zebrafish Proteins / Q000378:metabolism*
chemical_list: D005136:Eye Proteins; C116462:NRF1 protein, zebrafish; D051266:Nuclear Respiratory Factor 1; D047492:Peroxisome Proliferator-Activated Receptors; D012333:RNA, Messenger; D029961:Zebrafish Proteins; D015094:3-Hydroxyacyl CoA Dehydrogenases; D003576:Electron Transport Complex IV; D002950:Citrate (si)-Synthase; D011770:Pyruvate Kinase