Mitochondrial dysfunction: A major player in hepatic development, function, and senescence.

线粒体功能障碍：肝脏发育、功能和衰老的主要参与者。

• 批准号: RGPIN-2021-04164
• 负责人: Hardy, Daniel
• 金额: $ 2.04万
• 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: 2021
• 资助国家: 加拿大
• 起止时间: 2021-01-01 至 2022-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=742906
• 关键词: Mitochondrial; dysfunction; major; player; hepatic

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, dysmetabolism, 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. Recently we have demonstrated that these MPR offspring with catch-up growth exclusively exhibit higher hepatic p66Shc, a critical adapter protein involved in mitochondrial dysfunction, oxidative stress, and senescence. However, the underlying mechanisms remain elusive. We have also demonstrated that MPR offspring with catch-up growth exclusively exhibit changes in hepatic postranslational histone modifications and microRNAs (i.e. miR-140, miR-203-a-p, miR-193b) which can directly or indirectly influence p66Shc expression, mitochondrial function, and senescence. Therefore, the overall hypothesis is that postnatal catch-up growth in MPR offspring impairs hepatic development, function, and senescence via epigenetic mechanisms.  To address this, the first objective will employ chromatin immunoprecipitation (ChIP) to examine the posttranslational histone modifications in the proximal promoter of p66shc in MPR offspring with and without catch-up growth. We will also address if mimics or inhibitors of miR-140 influence the epigenetic regulation of hepatic p66Shc in vitro using cultured neonatal hepatocytes. For our second objective, using neonatal hepatocytes treated with mimics or inhibitors of miR-203a-p, we will address if alterations in miR-203a-p levels influences hepatic p66Shc expression and downstream mitochondrial function using the Seahorse XFe24 analyzer.  Finally, given Cyclin D1, an important component of the cell cycle, has been implicated in (i) premature senescence and (ii) is inversely related to miR-193b expression in these MPR offspring, our third objective is to directly implicate the role of miR-193b on mitochondrial function and senescence in the liver. To examine this relationship further, we will assess if mimics or inhibitors of miR-193b in vitro alters Cyclin D1 expression, mitochondrial function, and ultimately the cell cycle/senescence in neonatal rat liver cells. Collectively, these studies would further implicate how a poor in utero environment epigenetically impairs mitochondrial activity leading to altered hepatic development, function, and ageing. 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 which has major implications on the livestock industry (e.g. improved meat quality).

出生后追赶生长加速与早衰之间的关系是生物学的重要发现之一。我们实验室和其他实验室最近的研究表明，孕期限制母体蛋白质(MPR，8%蛋白质)后快速追赶生长会导致肝脏过早衰老、代谢障碍和寿命下降。相反，如果没有追赶增长(由于终生保持8%的蛋白质饮食)，长寿不会受到阻碍。最近，我们证明了这些追赶生长的MPR后代只表现出较高的肝脏p66Shc，这是一种参与线粒体功能障碍、氧化应激和衰老的关键适配蛋白。然而，潜在的机制仍然难以捉摸。我们还证明，追赶生长的MPR后代仅表现出肝脏翻译后组蛋白修饰和microRNAs(即miR-140、miR-203-a-p、miR-193B)的变化，这些变化可以直接或间接影响p66Shc的表达、线粒体功能和衰老。因此，总体假设是MPR后代出生后的追赶生长通过表观遗传机制损害肝脏的发育、功能和衰老。为了解决这个问题，第一个目标将使用染色质免疫沉淀(CHIP)来检测有追赶生长和没有追赶生长的MPR后代中p66shc近端启动子的翻译后组蛋白修饰。我们还将探讨miR-140的模拟物或抑制剂是否影响体外培养的新生肝细胞对肝脏p66Shc的表观遗传调节。对于我们的第二个目标，使用miR-203a-p的模拟物或抑制剂处理的新生肝细胞，我们将使用SeaHorse XFe24分析仪来研究miR-203a-p水平的变化是否影响肝脏p66Shc的表达和下游线粒体功能。最后，鉴于细胞周期的重要组成部分Cyclin D1在这些MPR后代中参与(I)过早衰老和(Ii)与miR-193B表达负相关，我们的第三个目标是直接揭示miR-193B在肝脏线粒体功能和衰老中的作用。为了进一步研究这种关系，我们将评估miR-193B的模拟物或抑制剂在体外是否会改变新生大鼠肝细胞的Cyclin D1表达、线粒体功能，并最终改变细胞周期/衰老。总而言之，这些研究将进一步暗示不良的宫内环境如何表观遗传地损害线粒体的活性，从而导致肝脏发育、功能和衰老的改变。此外，通过使用这种MPR机制作为一种独特且高度相关的早衰模型，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，这对畜牧业具有重大意义(例如，改善肉类质量)。