SMCT1介导短链脂肪酸跨瘤胃转运在奶牛SARA发生发展中的作用机制

亚急性瘤胃酸中毒（SARA）是集约化奶牛养殖场常见的群发性生产疾病。瘤胃内短链脂肪酸（SCFA）生成增多和/或吸收障碍引起的SCFA蓄积是SARA的病理学基础，但其吸收障碍的原因尚不清楚。基于申请者前期证实SARA奶牛瘤胃上皮介导SCFA转运的重要分子Na+偶联单羧酸转运蛋白1（SMCT1）低表达，且高浓度的SCFA抑制SMCT1表达，本项目提出SARA病牛瘤胃SCFA的蓄积可能使SMCT1介导的SCFA转运功能异常，进而导致SCFA吸收障碍的科学假设。拟通过高精粗比日粮诱导奶牛SARA模型（在体）、尤斯灌流室（组织）和原代瘤胃上皮细胞体外培养（细胞）三个方面，明确SMCT1介导的SCFA跨瘤胃转运机制，探究SCFA蓄积引起瘤胃内pH下降，乳酸、LPS和组胺增加对SMCT1介导的SCFA转运的影响，为揭示SMCT1介导的SCFA跨瘤胃转运机制在SARA发生发展中的作用提供理论依据。

Subacute rumen acidosis (SARA) is a common mass production disease in intensive dairy farms. Accumulation of short-chain fatty acids (SCFA) in the rumen due to increased production and/or malabsorption is the pathological basis of SARA, but the cause of SCFA malabsorption remains unclear. Based on the applicant's previous confirmation that, sodium-coupled monocarboxylate transporter 1 (SMCT1), an important molecule of rumen epithelium mediated SCFA transport, was low expressed in SARA cows, and the expression of SMCT1 was inhibited by high concentration of SCFA. This project proposes that SCFA accumulation in rumen of SARA cows may cause SMCT1-mediated SCFA transport function abnormal, thus leading to the malabsorption of SCFA. This project intends to corroborate SMCT1 role in rumen epithelial SCFA transportation through establishing a SARA cows model induced by high concentrate diet (in vivo), Ussing chamber (organizations) and the primary culture of rumen epithelial cells in vitro (cells), which could clarify the mechanism of SMCT1 mediated SCFA across rumen transportation. This project will also investigate the effects of SCFA accumulation on rumen pH reduction and increase of lactic acid, LPS and histamine on SMCT1-mediated SCFA transport, which could provide a theoretical basis for revealing the function of SMCT1-mediated SCFA transport across rumen in the development of SARA.