Vermillion Katie L, Anderson Kyle J, Hampton Marshall, Andrews Matthew T
Department of Biology, University of Minnesota Duluth, Duluth, Minnesota; and.
Department of Mathematics and Statistics, University of Minnesota Duluth, Duluth, Minnesota.
Physiol Genomics. 2015 Mar;47(3):58-74. doi: 10.1152/physiolgenomics.00108.2014. Epub 2015 Jan 8.
Throughout the hibernation season, the thirteen-lined ground squirrel (Ictidomys tridecemlineatus) experiences extreme fluctuations in heart rate, metabolism, oxygen consumption, and body temperature, along with prolonged fasting and immobility. These conditions necessitate different functional requirements for the heart, which maintains contractile function throughout hibernation, and the skeletal muscle, which remains largely inactive. The adaptations used to maintain these contractile organs under such variable conditions serves as a natural model to study a variety of medically relevant conditions including heart failure and disuse atrophy. To better understand how two different muscle tissues maintain function throughout the extreme fluctuations of hibernation we performed Illumina HiSeq 2000 sequencing of cDNAs to compare the transcriptome of heart and skeletal muscle across the circannual cycle. This analysis resulted in the identification of 1,076 and 1,466 differentially expressed genes in heart and skeletal muscle, respectively. In both heart and skeletal muscle we identified a distinct cold-tolerant mechanism utilizing peroxisomal metabolism to make use of elevated levels of unsaturated depot fats. The skeletal muscle transcriptome also shows an early increase in oxidative capacity necessary for the altered fuel utilization and increased oxygen demand of shivering. Expression of the fetal gene expression profile is used to maintain cardiac tissue, either through increasing myocyte size or proliferation of resident cardiomyocytes, while skeletal muscle function and mass are protected through transcriptional regulation of pathways involved in protein turnover. This study provides insight into how two functionally distinct muscles maintain function under the extreme conditions of mammalian hibernation.
在整个冬眠季节,三线地松鼠(Ictidomys tridecemlineatus)的心率、新陈代谢、氧气消耗和体温会经历极端波动,同时伴有长时间禁食和不活动。这些情况对心脏和骨骼肌提出了不同的功能需求,心脏在整个冬眠期间维持收缩功能,而骨骼肌在很大程度上保持不活动状态。在如此多变的条件下用于维持这些收缩器官的适应性变化,可作为研究包括心力衰竭和废用性萎缩在内的多种医学相关病症的天然模型。为了更好地理解两种不同的肌肉组织在冬眠的极端波动过程中是如何维持功能的,我们对cDNA进行了Illumina HiSeq 2000测序,以比较心脏和骨骼肌在全年周期中的转录组。该分析分别在心脏和骨骼肌中鉴定出1076个和1466个差异表达基因。在心脏和骨骼肌中,我们都发现了一种独特的耐寒机制,该机制利用过氧化物酶体代谢来利用升高的不饱和储存脂肪水平。骨骼肌转录组还显示,颤抖时燃料利用改变和氧气需求增加所需的氧化能力早期增加。胎儿基因表达谱的表达用于维持心脏组织,要么通过增加心肌细胞大小,要么通过驻留心肌细胞的增殖,而骨骼肌功能和质量则通过参与蛋白质周转的途径的转录调控得到保护。这项研究深入了解了两种功能不同的肌肉在哺乳动物冬眠的极端条件下是如何维持功能的。