Tril基因对小鼠糖代谢的影响及主要的代谢机制

Obesity is a major health issue, linked to insulin resistance and elevated risk of type 2 diabetes. However, it is uncertain to what extent disrupted glucose homeostasis and other features of poor metabolic health in individuals with obesity are a consequence of elevated adiposity alone, or whether dietary macronutrient composition is an additional or sole factor of importance. Glucose tolerance is a function of glucose stimulated insulin secretion, liver glucose output and tissue insulin sensitivity. Previously, we demonstrated that only dietary fat regulates energy intake and causes adiposity in mice. We then found that body fat impacted both fasting blood glucose and glucose tolerance mainly through insulin and leptin. More importantly, we identified the novel Tril gene, which also impact glucose tolerance. TLR4 has been directly implicated in the link between diet-induced-obesity and insulin resistance in mice, and was increased in type 2 diabetic patients. As a novel modulator of TLR4, the relationship between Tril gene and glucose homeostasis is unknown. Single cell RNAseq illustrated the expression of Tril in both BAT and sWAT. High fat diet challenge altered the expression of Tril in different adipose tissues of mice. Therefore, the objectives of this study are to explore the impact of Tril on the phenotype and glucose homeostasis in mice, by overexpress or knockdown Tril gene, and to investigate the underlying pathways by which Tril influence glucose metabolism in mice.

肥胖是全世界面临的严峻的健康问题，是很多慢性疾病的致病因素，尤其是糖尿病。但是肥胖如何影响糖代谢，是通过体脂或饮食影响，还是二者共同影响糖代谢仍不明确。申请人前期研究表明，饮食中只有脂肪调节能量摄入并导致肥胖，但与糖耐受力无关。首次揭示只有体脂与空腹血糖和糖耐受力相关，且除胰岛素和瘦素外，还可通过Tril基因对其调节，且证实Tril基因在脂肪组织中的表达以及对高脂摄食的敏感性。Tril基因作为一种新的TLR4信号介质，与糖代谢之间的关系尚不明确。本研究的目标是，解析小鼠体内Tril基因改变后，小鼠表型变化情况，明确Tril基因对表型的影响；分析Tril基因表达发生变化后小鼠各组织转录组的变化情况，解析Tril基因是否参与下丘脑饥饿通路、白色脂肪棕色化通路、葡萄糖摄取通路以及糖代谢调控通路等主要代谢通路，最终确证Tril基因对小鼠表型的影响及影响糖代谢的主要机制。

肥胖不仅本身是一种慢性疾病，又是糖尿病很多等慢性疾病的致病因素。但是，肥胖究竟通过怎样的机制导致糖尿病，饮食因素还是高体脂，目前仍不清楚。前期研究发现，饮食碳水化合物和蛋白质与空腹血糖水平和血糖耐受力均无关，只有脂肪含量与空腹血糖水平显著相关，但血糖耐受力无关。体脂不仅与空腹血糖水平，也与血糖耐受曲线下面积相关。饮食脂肪与体脂显著相关，而体脂对糖耐受力的影响除通过胰岛素和瘦素外，还与Tril等基因所参与的通路发挥作用。Tril基因不仅与体脂显著相关，还与糖耐受力显著正相关。Tril是一种TLR4（toll样受体）信号介质，而TLR4参与高脂饮食中脂肪细胞的炎症反应，TLR4配体在2型糖尿病患者中的表达也有所增加。然而，目前仍没有Tril对糖稳态影响的报道。因此，本研究解析高脂饮食下Tril对小鼠体脂及其糖稳态的影响。本研究以C57BL/6N小鼠为研究对象，解析不同组织中Tril基因的表达情况。另外，采用腺相关病毒的方法，通过尾静脉注射，对Tril基因分别进行敲降和过表达，并对小鼠的体重、摄食和糖耐受力等指标进行测定，探索Tril基因表达量的变化对小鼠糖耐受情况的影响。本项目采用qPCR方法进行对病毒侵染后小鼠的基因表达情况进行验证，并进一步确认AAV基因表达的变化对小鼠糖耐受力的影响。通过采用腺相关病毒的方法对Tril基因进行敲降或过表达处理，结果表明Tril基因表达量的降低或增加对小鼠体重和摄食的影响不大，小鼠的脑、肝脏、胰腺以及消化道（包括小肠、盲肠和大肠）的重量没有显著差异。不同处理小鼠体重与糖耐受力显著正相关，但是Tril表达水平与血糖曲线下面积不相关。