Abstract：
Muscle and bone are cooperatively preserved in Daurian ground squirrels (Spermophilus dauricus) during hibernation. As such, we hypothesized that IGF-1 and myostatin may contribute to musculoskeletal maintenance during this period. Thus, we systematically assessed changes in the protein expression levels of IGF-1 and myostatin, as well as their corresponding downstream targets, in the vastus medialis (VM) muscle and femur in Daurian ground squirrels during different stages. Group differences were determined using one-way analysis of variance (ANOVA). Results indicated that the co-localization levels of IGF-1 and its receptor (IGF-1R) increased by 50% during the pre-hibernation period (PRE) and by 35% during re-entry into torpor (RET) compared to the summer active period (SA). The phosphorylation level of FOXO1 in the VM muscle increased by 50% in the torpor (TOR) group and by 82% in the inter-bout arousal (IBA) group compared to the PRE group. The phosphorylation level of SGK-1 increased by 54% in the IBA group and by 62% in the RET group compared to the SA group. In contrast, the protein expression of IGF-1 and phosphorylation levels of PI3K, Akt, mTOR, and GSK3β in the VM muscle showed no obvious differences among the different groups. β-catenin protein expression was up-regulated by 84% in the RET group compared to the SA group, while the content of IGF-1 protein, correlation coefficients of IGF-1 and IGF-1R, and phosphorylation levels of PI3K, Akt, and GSK3β in the femur showed no significant differences among groups. Regarding myostatin and its downstream targets, myostatin protein expression decreased by 70% in the RET group compared to the SA group, whereas ActRIIB protein expression and Smad2/3 phosphorylation in the VM muscle showed no obvious differences among groups. Furthermore, Smad2/3 phosphorylation decreased by 58% in the TOR group and 53% in the RET group compared to the SA group, whereas ActRIIB protein expression in the femur showed no obvious differences among groups. Overall, the observed changes in IGF-1 and myostatin expression and their downstream targets may be involved in musculoskeletal preservation during hibernation in Daurian ground squirrels.
摘要：
冬眠期间，肌肉和骨骼共同保存在Daurian地松鼠（Spermophilusdauricus）中。因此，我们假设IGF-1和肌肉生长抑制素在这一时期可能有助于肌肉骨骼的维持.因此，我们系统地评估了IGF-1和肌肉生长抑制素的蛋白质表达水平的变化，以及它们相应的下游目标，在不同阶段，Daurian地松鼠的股内侧（VM）肌肉和股骨中。使用单向方差分析(ANOVA)确定组差异。结果表明，与冬眠前（PRE）相比，IGF-1及其受体（IGF-1R）的共定位水平在冬眠前（PRE）期间增加了50％，在重新进入torpor（RET）期间增加了35％。夏季活跃期（SA）。与PRE组相比，托普（TOR）组的VM肌肉中FOXO1的磷酸化水平增加了50％，在发作间唤醒（IBA）组中增加了82％。与SA组相比,在IBA组中SGK-1的磷酸化水平增加了54%,在RET组中增加了62%。相比之下,IGF-1的蛋白表达和PI3K的磷酸化水平,Akt,mTOR,VM肌肉中的GSK3β在不同组之间无明显差异。与SA组相比，RET组β-catenin蛋白表达上调84%，而IGF-1蛋白的含量，IGF-1和IGF-1R的相关系数，和PI3K的磷酸化水平，Akt,股骨GSK3β在各组间无显著差异。关于肌肉生长抑制素及其下游靶标，与SA组相比，RET组肌肉生长抑制素蛋白表达下降了70%，而VM肌肉中ActRIIB蛋白表达和Smad2/3磷酸化在各组间无明显差异。此外，与SA组相比，TOR组Smad2/3磷酸化下降了58%，RET组下降了53%，股骨ActRIIB蛋白表达在各组间无明显差异。总的来说,观察到的IGF-1和肌肉生长抑制素表达及其下游靶标的变化可能与Daurian地松鼠冬眠期间的肌肉骨骼保存有关。
