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

加速的产后追赶性生长和过早衰老之间的关系是生物学上的重要发现之一。我们实验室和其他人最近的研究表明，大鼠妊娠期间母体蛋白质限制（MPR，8%蛋白质），然后快速追赶生长，导致肝脏过早衰老，代谢障碍和寿命缩短。相反，如果没有追赶性生长（由于一生中维持8%的蛋白质饮食），长寿不会受到阻碍。最近，我们已经证明，这些MPR的后代与追赶增长专门表现出较高的肝脏p66 Shc，一个关键的衔接蛋白参与线粒体功能障碍，氧化应激和衰老。然而，根本的机制仍然难以捉摸。我们还证明，具有追赶生长的MPR后代仅表现出肝脏翻译后组蛋白修饰和microRNA（即miR-140，miR-203-a-p，miR-193 b）的变化，这些变化可以直接或间接影响p66 Shc表达，线粒体功能和衰老。因此，总体假设是MPR后代的出生后追赶性生长通过表观遗传机制损害肝脏发育、功能和衰老。 为了解决这一问题，第一个目标将采用染色质免疫沉淀（ChIP）检查的近端启动子的p66 shc在MPR后代和不追赶生长的翻译后组蛋白修饰。我们还将使用培养的新生肝细胞在体外研究miR-140的模拟物或抑制剂是否影响肝脏p66 Shc的表观遗传调控。对于我们的第二个目标，使用miR-203 a-p模拟物或抑制剂处理的新生肝细胞，我们将使用Seahorse XFe 24分析仪研究miR-203 a-p水平的改变是否影响肝脏p66 Shc表达和下游线粒体功能。 最后，考虑到细胞周期的重要组成部分Cyclin D1与（i）早衰和（ii）这些MPR后代中的miR-193 b表达呈负相关，我们的第三个目标是直接暗示miR-193 b对肝脏线粒体功能和衰老的作用。为了进一步研究这种关系，我们将评估体外miR-193 b的模拟物或抑制剂是否会改变新生大鼠肝细胞中细胞周期蛋白D1的表达、线粒体功能以及最终的细胞周期/衰老。总的来说，这些研究将进一步揭示子宫内环境不良如何表观遗传地损害线粒体活性，导致肝脏发育、功能和衰老改变。此外，通过使用这种MPR制度作为一个独特的和高度相关的模型过早衰老，我们可以进一步阐明如何更好地管理低出生体重后代可以提高哺乳动物的寿命，这对畜牧业有重大影响（如改善肉质）。

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).