McClelland Grant B, Craig Paul M, Dhekney Kalindi, Dipardo Shawn
Department of Biology, McMaster University, 1280 Main Street West, Hamilton, ON L8S 4K1, Canada.
J Physiol. 2006 Dec 1;577(Pt 2):739-51. doi: 10.1113/jphysiol.2006.119032. Epub 2006 Sep 21.
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.
运动训练和冷适应都会在脊椎动物中引发肌肉重塑，产生更具有氧代谢能力的表型。在变温动物中，运动训练和冷适应代表着不同的刺激因素。目前尚不清楚这些刺激是通过共同机制起作用，还是不同机制导致相同的表型。本研究的目的是利用一种变温脊椎动物，探究可能导致收缩和温度诱导的肌肉重塑的潜在机制。将成年斑马鱼（Danio rerio）分成不同组，分别进行为期4周的游泳训练或冷适应处理。我们发现，线粒体标记酶柠檬酸合酶（CS）在冷适应组中增加了1.5倍，在运动训练组中增加了1.3倍（P<0.05）。细胞色素c氧化酶（COx）在运动训练后增加了1.2倍（P<0.05），在冷适应后增加了1.2倍（P=0.07）。然而，与运动训练组相比，只有冷适应增加了β-羟酰基辅酶A脱氢酶（HOAD），与对照斑马鱼相比，冷适应还增加了丙酮酸激酶（PK）。我们评估了这些处理对动物整体性能的影响。运动训练组的最大绝对持续游泳速度（Ucrit）增加了，但冷适应组没有增加。实时PCR分析表明，运动训练主要通过转录调控增加CS，但冷处理则不然。两种处理都使核呼吸因子（NRF）-1 mRNA增加，冷适应组比对照组增加了2.3倍，运动训练组比对照组增加了4倍。相比之下，两个实验组的过氧化物酶体增殖物激活受体（PPAR）-α mRNA水平均下降，而PPAR-β1仅在运动训练组中下降。此外，两种处理均未改变PPAR-γ共激活因子（PGC）-1α mRNA水平。在斑马鱼中，温度和运动都会产生更具有氧代谢能力的表型，但存在刺激依赖性反应（即HOAD和PK活性）。虽然NRF-1 mRNA的类似变化表明，共同反应可能是有氧肌肉重塑的基础，但也存在导致特定温度和运动诱导表型的不同变化（即CS和PPAR-β1 mRNA）。
