The Role of MicroRNAs on Hepatic Growth and Senescence

MicroRNA 对肝脏生长和衰老的作用

• 批准号: RGPIN-2015-04090
• 负责人: Hardy, Daniel
• 金额: $ 1.75万
• 依托单位: University of Western Ontario
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2016
• 资助国家: 加拿大
• 起止时间: 2016-01-01 至 2017-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=612767
• 关键词: Role; MicroRNAs; Hepatic; Growth; Senescence

The relationship between accelerated postnatal catch-up growth and premature ageing is one of the important discoveries in biology. Recent studies by our laboratory and others has demonstrated that maternal protein restriction (MPR, 8% protein) during pregnancy in rats followed by rapid catch-up growth leads to premature hepatic senescence, glucose intolerance, and decreased longevity. In contrast, if there is no catch-up growth (due to maintenance of an 8% protein diet throughout life), longevity is not hindered. While we have previously demonstrated that posttranslational histone modifications may play a role in the long-term fetal programming of the liver, very little is known about the role of microRNAs (miRs) in governing hepatic function and senescence. Using Microarray analysis, we have recently identified that miR-193b, miR-29, and miR-140 are altered in the senescent livers of these MPR offspring with catch-up growth. Therefore, the overall goal of our research program is to understand the regulation and identity of miRNA targets in the liver which influence function, growth and senescence. Recently we demonstrated that (i) miR-29 expression is inversely related to insulin growth factor 1 (Igf-1) in these MPR offspring, (ii) these MPR offspring have augmented hepatic endoplasmic reticulum (ER) stress, and (iii) ER stress increases neuronal miR-29a in vivo. Therefore, our first objective is to directly assess the role of ER stress on hepatic miR-29a and other miRs in vitro using primary cultures of neonatal rat liver cells treated with and without activators of ER stress followed by measuring temporal changes in miR-29, Igf-1 expression and other miR-29 target genes. In addition, we would also inhibit miR-29 expression to observe if the silencing of Igf-1 could be prevented. Given Cyclin D1, an important component of the cell cycle, has been implicated in premature senescence and is inversely related to miR-193b expression in these MPR offspring, our second objective is to characterize if augmented Cyclin D1 is associated with impairment of other components the cell cycle. To directly implicate the role of miR-193b on Cyclin D1 and senescence in the liver, we will assess if activation of miR-193b alters Cyclin D1 expression, the cell cycle, and senescence in primary cultures of neonatal rat liver cells. Finally, given miR-140 targets HDAC-4 and SIRT1, both histone deacetylases, our third objective is to test if alterations in miR-140 in vitro influences total Histone H3 acetylation along with hepatic target genes known to be affected by histone acetylation and MPR. Collectively, these studies would further implicate miRs with impaired hepatic function, growth and aging. In addition, by using this MPR regime as a unique and highly relevant model of premature senescence, we can further elucidate how better management of low birth weight offspring can improve longevity in mammals.

出生后加速追赶生长与过早衰老之间的关系是生物学的重要发现之一。我们实验室和其他人最近的研究表明，大鼠怀孕期间母体蛋白质限制（MPR， 8%蛋白质），随后快速追赶生长导致肝脏过早衰老，葡萄糖耐受不良和寿命下降。相反，如果没有后起之长（由于终生保持8%的蛋白质饮食），寿命不会受到影响。虽然我们之前已经证明翻译后组蛋白修饰可能在肝脏的长期胎儿规划中发挥作用，但对于microRNAs （miRs）在控制肝功能和衰老中的作用知之甚少。通过微阵列分析，我们最近发现，在这些MPR后代的衰老肝脏中，miR-193b、miR-29和miR-140发生了改变。因此，我们研究计划的总体目标是了解影响肝脏功能、生长和衰老的miRNA靶点的调控和身份。最近，我们证明(i)在这些MPR后代中miR-29的表达与胰岛素生长因子1 （Igf-1）呈负相关，（ii）这些MPR后代增加了肝内质网（ER）应激，（iii） ER应激增加了体内神经元miR-29a。因此，我们的第一个目标是直接评估内质网应激对肝脏miR-29a和其他mir的作用，在体外使用经内质网应激激活剂和未经内质网应激激活剂处理的新生大鼠肝细胞进行原代培养，然后测量miR-29、Igf-1表达和其他miR-29靶基因的时间变化。此外，我们还将抑制miR-29的表达，观察是否可以阻止Igf-1的沉默。Cyclin D1是细胞周期的一个重要组成部分，与这些MPR后代的miR-193b表达呈负相关，因此我们的第二个目标是表征Cyclin D1增强是否与细胞周期其他组成部分的损伤有关。为了直接揭示miR-193b对Cyclin D1和肝脏衰老的作用，我们将评估miR-193b的激活是否会改变新生大鼠肝细胞原代培养中Cyclin D1的表达、细胞周期和衰老。最后，考虑到miR-140靶向HDAC-4和SIRT1这两种组蛋白去乙酰化酶，我们的第三个目标是测试miR-140的改变是否会影响体外组蛋白H3乙酰化总量以及已知受组蛋白乙酰化和MPR影响的肝脏靶基因。总的来说，这些研究将进一步表明miRs与肝功能受损、生长和衰老有关。此外，通过将这种MPR机制作为一种独特且高度相关的过早衰老模型，我们可以进一步阐明如何更好地管理低出生体重的后代可以提高哺乳动物的寿命。