title: The molecular basis of aerobic metabolic remodeling differs between oxidative muscle and liver of threespine sticklebacks in response to cold acclimation.
abstract: We sought to determine the molecular basis of elevations in aerobic metabolic capacity in the oxidative muscle and liver of Gasterosteus aculeatus in response to cold acclimation. Fishes were cold- or warm-acclimated for 9 wk and harvested on days 1, 2, and 3 and weeks 1, 4, and 9 of cold acclimation at 8 degrees C, and on day 1 and week 9 of warm acclimation at 20 degrees C. Mitochondrial volume density was quantified using transmission electron microscopy and stereological techniques in warm- and cold-acclimated fishes harvested after 9 wk at 20 or 8 degrees C. Changes in aerobic metabolic capacity were assessed by measuring the maximal activity of citrate synthase (CS) and cytochrome-c oxidase (COX) in fishes harvested throughout the acclimation period. Transcript levels of the aerobic metabolic genes CS, COXIII, and COXIV, and known regulators of mitochondrial biogenesis, including peroxisome proliferator-activated receptor-gamma coactivators-1alpha and -1beta (PGC-1alpha and PGC-1beta), nuclear respiratory factor-1 (NRF-1), and mitochondrial transcription factor-A were measured in fishes harvested throughout the acclimation period using quantitative real-time PCR. The maximal activities of CS and COX increased in response to cold acclimation in both tissues, but mitochondrial volume density only increased in oxidative muscle (P < 0.05). The time course for changes in aerobic metabolic capacity differed between liver and muscle. The expression of CS increased within 1 wk of cold acclimation in liver and was correlated with an increase in mRNA levels of NRF-1 and PGC-1beta. Transcript levels of aerobic metabolic genes increased later in oxidative muscle, between weeks 4 and 9 of cold acclimation and were correlated with an increase in mRNA levels of NRF-1 and PGC-1alpha. These results show that aerobic metabolic remodeling differs between liver and muscle in response to cold acclimation and may be triggered by different stimuli.
authors.affiliation: Institute of Arctic Biology and Department of Biology and Wildlife, University of Alaska Fairbanks, Fairbanks, Alaska 99775, USA.
authors.forename: J I
authors.initials: JI
authors.lastname: Orczewska
authors.forename: G
authors.initials: G
authors.lastname: Hartleben
authors.forename: K M
authors.initials: KM
authors.lastname: O'Brien
mesh_terms: D000064:Acclimatization / Q000502:physiology*; D000818:Animals; D002950:Citrate (si)-Synthase / Q000235:genetics / Q000378:metabolism; D003080:Cold Temperature; D004268:DNA-Binding Proteins; D003576:Electron Transport Complex IV / Q000235:genetics / Q000378:metabolism; D005399:Fishes / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D008099:Liver / Q000378:metabolism; D008928:Mitochondria / Q000235:genetics / Q000378:metabolism; D024101:Mitochondrial Proteins; D009132:Muscles / Q000378:metabolism; D051266:Nuclear Respiratory Factor 1 / Q000378:metabolism; D010084:Oxidation-Reduction; D012333:RNA, Messenger / Q000378:metabolism; D023701:Smegmamorpha / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors
chemical_list: D004268:DNA-Binding Proteins; D024101:Mitochondrial Proteins; D051266:Nuclear Respiratory Factor 1; D012333:RNA, Messenger; D014157:Transcription Factors; C422562:mitochondrial transcription factor A; D003576:Electron Transport Complex IV; D002950:Citrate (si)-Synthase