University of Belgrade, Department of Physiology, Institute for Biological Research 'Sinisa Stankovic', Bulevar despota Stefana 142, 11060 Belgrade, Serbia.
J Exp Biol. 2013 Nov 15;216(Pt 22):4233-41. doi: 10.1242/jeb.089334. Epub 2013 Aug 15.
This study examined the molecular basis of energy-related regulatory mechanisms underlying metabolic recruitment of skeletal muscle during cold acclimation and possible involvement of the l-arginine/nitric oxide-producing pathway. Rats exposed to cold (4±1°C) for periods of 1, 3, 7, 12, 21 and 45 days were divided into three groups: untreated, l-arginine treated and N(ω)-nitro-l-arginine methyl ester (l-NAME) treated. Compared with controls (22±1°C), there was an initial increase in the protein level of 5'-AMP-activated protein kinase α (day 1), followed by an increase in peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α) and peroxisome proliferator-activated receptors (PPARs): PPARα and PPARγ from day 1 and PPARδ from day 7 of cold acclimation. Activation of the PGC-1α/PPAR transcription program was accompanied by increased protein expression of the key metabolic enzymes in β-oxidation, the tricarboxylic acid cycle and oxidative phosphorylation, with the exceptions in complex I (no changes) and ATP synthase (decreased at day 1). Cold did not affect hexokinase and GAPDH protein levels, but increased lactate dehydrogenase activity compared with controls (1-45 days). l-arginine sustained, accelerated and/or intensified cold-induced molecular remodeling throughout cold acclimation. l-NAME exerted phase-dependent effects: similar to l-arginine in early cold acclimation and opposite after prolonged cold exposure (from day 21). It seems that upregulation of the PGC-1α/PPAR transcription program early during cold acclimation triggers the molecular recruitment of skeletal muscle underlying the shift to more oxidative metabolism during prolonged cold acclimation. Our results suggest that nitric oxide has a role in maintaining the skeletal muscle oxidative phenotype in late cold acclimation but question its role early in cold acclimation.
本研究旨在探讨冷驯化过程中骨骼肌代谢募集的能量相关调节机制的分子基础，以及 l-精氨酸/一氧化氮产生途径的可能参与。将暴露于冷环境（4±1°C）1、3、7、12、21 和 45 天的大鼠分为三组：未处理组、l-精氨酸处理组和 N(ω)-硝基-l-精氨酸甲酯（l-NAME）处理组。与对照组（22±1°C）相比，冷驯化初期 5'-AMP 激活蛋白激酶α（第 1 天）的蛋白水平增加，随后过氧化物酶体增殖物激活受体-γ共激活因子-1α（PGC-1α）和过氧化物酶体增殖物激活受体（PPARs）增加：PPARα和 PPARγ从冷驯化第 1 天开始，PPARδ从第 7 天开始。PGC-1α/PPAR 转录程序的激活伴随着β-氧化、三羧酸循环和氧化磷酸化关键代谢酶的蛋白表达增加，除复合体 I（无变化）和 ATP 合酶（第 1 天减少）外。冷驯化不会影响己糖激酶和 GAPDH 蛋白水平，但与对照组相比，乳酸脱氢酶活性增加（1-45 天）。l-精氨酸维持、加速和/或强化了冷驯化过程中的冷诱导分子重塑。l-NAME 发挥了时相依赖性作用：在冷驯化早期与 l-精氨酸相似，在长时间冷暴露后则相反（从第 21 天开始）。似乎在冷驯化早期，PGC-1α/PPAR 转录程序的上调触发了骨骼肌的分子募集，导致在长时间冷驯化期间向更氧化代谢的转变。我们的结果表明，一氧化氮在晚期冷驯化中维持骨骼肌氧化表型方面发挥作用，但对冷驯化早期的作用提出质疑。
