肝脏雌激素受体在营养调控母猪泌乳与发情转换中的作用与机制

Nutrition deficit caused delayed return to estrus cyclicity and even reproductive failure in postweaning sows as a consequence of inadequate secretion of metabolic hormone Leptin and IGFI to induce sufficient central kisspeptin expression, a protein required for normal pulsatile GnRH release, however, the mechanism responsible for the nutritional regulation of metabolic hormones secretion remains unclear. Researh in mice revealed that liver estrogen receptor alpha (ERα) played a critical role in directing nutrition-dependent secretions of metabolic hormones and integrating metabolic and reproductive functions, yet the phsiological role of hepatic ERα remained uncertain in sows. In present study, the signal pathway by which the amino acid-dependent activation of ERα responsible for IGFI secretion, if any, will be revealed using in vitro primary hepatic cell culture from lactating sows or ERα transfected hepatic cells. Using postweaning sows with severe body reserve mobilization, exogenous chronic amino acids were intravenously infused to confirm the IGFI secretion by amino acid-dependent activation of ERα, and further test whether this increased the central secretion of of kisspeptin to facilitate estrus cyclicity, and further confirms the developmental synchronization of reproductive tissue, e.g. uterus and ovaries. Based on the in vitro and in vivo tests, weaned sows with severe body reserve mobilization would be returing to estrus cyclicity advancely with optimized amino acid forticated diets. The results of the present study would shed light on the mechanisms integreting nutritional regimen and reproductive functions, and will also provide practical nutritional strategies to improve the percentage of estrus gilts and reproductive performance of postweaning sows.

营养不足引起泌乳母猪断奶后发情推迟或失败，原因在于体内代谢激素Leptin和IGFI分泌减少，导致情期启动关键蛋白Kisspeptin表达量降低，不能激活GnRH神经元，从而抑制情期启动，但营养调控代谢激素合成与分泌的机制仍不清楚。鼠上研究发现，肝脏雌激素受体（ERα）在介导营养调控代谢激素合成和繁殖功能转换中发挥重要作用，然而，在猪上未见报道。本项目采用母猪肝细胞培养和转染ERα细胞模型，研究氨基酸对肝脏ERα的激活和IGFI的合成效应及其作用信号通路；进一步选用高失重断奶母猪，采用恒流灌注氨基酸，证实补充氨基酸可通过肝脏ERα活性介导IGFI合成，并促进Kisspeptin分泌，启动发情，同时验证繁殖组织发育的同步性；采用动物试验筛选高失重母猪由断奶向发情快速转换的氨基酸日粮。本研究对揭示营养与繁殖功能转换的分子机理具有重大理论意义，并对提高断奶母猪的发情率和繁殖成绩具有重大实践意义

项目背景：营养不足引起泌乳母猪断奶后发情推迟或失败，直接导致母猪繁殖障碍而被淘汰，其原因在于体内代谢激素胰岛素样生长因子（IGF1）和成纤维细胞生长因子（FGF21）等分泌紊乱，导致促性腺激素分泌不足，从而抑制情期启动及卵泡发育，但营养调控代谢激素合成与分泌及其与繁殖激素之间的互作效应尚不清楚。. 研究内容：构建泌乳母猪高、低失重模型，通过代谢组学分析母猪血液氨基酸代谢及激素分泌的差异；通过体外培养肝原代细胞模型，证实雌激素受体α在氨基酸对代谢激素分泌中的作用；通过动物试验，解析不同发情周期的雌激素信号与机体能量的互作机制；通过中试及大规模母猪饲养试验，证实氨基酸组合对高失重泌乳母猪断奶与发情转换、卵泡发育及繁殖力的调控效应。. 重要结果：基于泌乳期高、低失重模型，发现高失重母猪断奶后情期启动显著推迟，屠宰母猪发现卵泡发育受阻，结合代谢组学分析，揭示高失重母猪29种与氨基酸合成、分解、蛋白质降解相关通路存在显著差异，鉴定出血液FGF21浓度与母猪断奶-发情转换密切相关；氨基酸水平与种类显著影响肝原代细胞FGF21表达与分泌，结合体内与体外试验证实雌二醇可通过肝脏雌激素受体信号调控FGF21表达及机体能量代谢；设计高、低氨基酸水平饲喂高失重泌乳母猪，高氨基酸水平显著改善高失重母猪的情期启动及卵泡发育。. 关键数据：泌乳期母猪体重损失达到33kg时，体蛋白损失3.93kg（占比9.44%），母猪断奶后情期启动受到显著影响；在高失重泌乳母猪日粮中额外补充氨基酸，卵巢重量由13.21g增加至18.35g，大卵泡数量由3.35个提高至7.93个。大群试验发现，高失重母猪饲粮添加特定组合的氨基酸将母猪的受胎率由85.3%提高至93.5%。. 科学意义：泌乳母猪体重损失过大引起繁殖障碍是规模化猪场母猪饲养难题。根据本研究的结果，对高失重泌乳母猪额外补充特定的氨基酸组合可显著提高母猪的繁殖力，对于改善生猪养殖效益、降低母猪淘汰率具有重要的生产价值。