锰抑制肉鸡腹脂沉积中关键酶LPL转录表达的分子机制

腹脂沉积过多严重制约着肉鸡生产效率，如何定向降低腹脂沉积是肉鸡生产中亟待解决的问题。我们前期研究发现，饲喂锰可有效降低肉鸡腹脂沉积，且与腹脂脂蛋白脂酶（LPL）mRNA表达下调密切相关，但其转录表达被抑制的分子机制尚不清楚。研究表明，锰可降低肉鸡腹脂KLF4 mRNA表达，而KLF4与LPL启动子区存在结合位点，且KLF4在脂肪沉积中起着重要作用。我们提出假说，即锰可能通过降低肉鸡腹脂KLF4的表达，进而减少KLF4与LPL启动子区的结合量，最终抑制LPL转录表达。因此，本项目拟采用ChIP-seq、过表达、siRNA、双荧光素酶报告基因联合点突变等技术，研究锰对肉鸡腹脂中以及正常和KLF4过表达/沉默的鸡前脂肪细胞中KLF4 mRNA和蛋白表达及其与LPL启动子区的结合量和LPL mRNA表达的影响，以揭示锰抑制肉鸡腹脂LPL转录表达的分子机制，为合理应用锰降低肉鸡腹脂沉积提供科学依据。

Excessive abdominal fat deposition seriously restricts the production efficiency of broiler chickens. How to reduce abdominal fat deposition is an urgent problem to be solved in the production of broiler chickens. Our previous studies have demonstrated that dietary supplemental manganese (Mn) could effectively reduce the abdominal fat deposition of broiler chickens, which is closely related to the down-regulation of the mRNA expression of the key enzyme lipoprotein lipase (LPL) involved in the abdominal fat deposition, but the underlying molecular mechanisms of the inhibited transcriptional expression are still unclear. It has been shown that Mn could reduce the mRNA expression of Kruppel-like transcriptional factor 4 (KLF4) in the abdominal fat of broiler chickens, and there are binding sites between the KLF4 and the LPL promoter region, and KLF4 plays an important role in fat deposition. We hypothesize that Mn may down-regulate the KLF4 expression, and then reduce the binding amount of the KLF4 to the LPL promoter region, and ultimately inhibit the transcriptional expression of the LPL in the abdominal fat of broiler chickens. Therefore, in the present project, the ChIP-seq, gene overexpression, siRNA, and dual-luciferase reporter gene-combined point mutation techniques will be used to study the effect of Mn on KLF4 mRNA and protein expressions and its binding amount with the LPL promoter region and LPL mRNA expression in the abdominal fat of broiler chickens and in normal or KLF4 gene overexpression/silencing chicken primary preadipocytes, in order to reveal the molecular mechanisms of Mn in inhibiting the transcriptional expression of the LPL in the abdominal fat of broiler chickens. The outcomes from the current study will provide scientific bases for the rational application of Mn to reduce the abdominal fat deposition of broiler chickens.