中介素依赖CRLR/RAMP途径改善肥胖小鼠脂肪组织慢性炎症的机制研究

The chronic inflammation in white adipose tissue plays a crucial role in obesity-associated metabolic disorders. Intermedin is a newly discovered cardiovascular protective peptide, and its receptor is the calcitonin receptor like receptor (CRLR). Our previous studies showed that the expression of intermedin and three types of receptor activity-modifying protein (RAMP) were significantly decreased in adipocytes of high-fat diet-induced obese mice. Intermedin treatment promotes adipose tissue browning through the up-regulation of uncoupling protein-1 (UCP-1) expression. However, the effect of intermedin on the chronic inflammation in white adipose tissue remains unclear. Based on the findings, we hypothesize that intermedin inhibits the expression of monocyte chemotactic protein-1 (MCP-1) in adipocytes and reduces the chronic inflammation of white adipose tissue in high-fat diet-induced obese mice in a CRLR/RAMP- dependent pathway. This study firstly used the high-fat diet-induced obese mice and aP2/AM2 transgenic (aAM2-tg) mice to confirm the effect of intermedin on the expression of MCP-1 and the chronic inflammation in white adipose tissue by histology and molecular biology technology; secondly, by using intermedin peptide or gene manipulation, we explored whether intermedin inhibits the expression of MCP-1 in adipocytes and reduces the chronic inflammation of white adipose tissue in high-fat diet-induced obese mice in a CRLR/RAMP- dependent pathway. The study findings will provide new ideas for the treatment of obesity-associated metabolic disorders.

脂肪组织慢性炎症是肥胖相关代谢异常的机制之一。我们前期发现，肥胖小鼠脂肪细胞中介素及受体活性调节蛋白（RAMP）表达降低，中介素上调脂肪细胞解偶联蛋白-1（UCP-1）表达、促进白色脂肪棕色化。预实验显示，中介素降低肥胖小鼠脂肪组织巨噬细胞浸润，抑制TNF-α诱导的脂肪细胞NF-κB活性并降低单核细胞趋化蛋白-1（MCP-1）表达。据此我们假设：中介素依赖受体（CRLR）及RAMP途径，抑制脂肪细胞MCP-1表达，减少脂肪组织巨噬细胞浸润，改善脂肪组织慢性炎症。本课题首先应用高脂诱导肥胖小鼠及脂肪组织特异性中介素高表达转基因小鼠模型通过组织学、分子生物学手段明确中介素对脂肪组织慢性炎症的影响；其次在原代脂肪细胞、分化的3T3-L1脂肪细胞，应用中介素受体拮抗剂、慢病毒敲低或过表达CRLR及RAMP等技术，初步阐明中介素抑制脂肪组织慢性炎症的具体机制。本研究为改善肥胖相关代谢异常提供新的思路

肥胖是2型糖尿病的重要危险因素，而肥胖相关的脂肪组织慢性炎症在其中发挥重要作用。课题组前期研究显示，在饮食诱导的肥胖小鼠及db/db小鼠，脂肪细胞的中介素及RAMP的三个亚型的表达均明显降低，提示脂肪组织中介素及其RAMP的表达下降可能参与肥胖相关的脂肪组织功能改变。本研究首先在整体人群水平探讨了2型糖尿病/糖耐量异常患者胰岛素抵抗及慢性炎症状态的相关影响因素，阐明糖耐量异常患者和2型糖尿病患者的血清VEGF水平升高，且与HOMA-IR水平呈明显正相关。而TPOAb水平是甲功正常的自身免疫性甲状腺炎患者HOMA-IR和hsCRP水平的独立影响因素。其次，本研究评估药物治疗对于胰岛素抵抗及β细胞功能改善程度的影响因素，明确较低基线HDL-C和较高HbA1c和SBP水平的新诊断2型糖尿病患者，经过阿卡波糖治疗更有可能实现β细胞功能的改善，而较高的基线空腹血糖和腰围是胰岛素抵抗改善的重要标志。并在体外培养的脂肪细胞、高脂喂养制成的肥胖小鼠模型等，阐明中介素依赖其受体CRLR，在受体活性调节蛋白RAMP参与下，抑制脂肪细胞MCP-1表达，减少脂肪组织巨噬细胞浸润，改善肥胖小鼠脂肪组织慢性炎症。本研究对于阐明肥胖相关胰岛素抵抗及慢性炎症的机制，做出积极有益的探索，具有较好的科学意义和应用价值。