盐酸小檗碱促进棕色脂肪产热耗能机制与视黄酸通路的关联研究

Energy surplus is an important pathological mechanism of obesity and its related metabolic disorders. Recent studies have demonstrated that there is brown adipose tissue in human adults and it plays an important role in consuming energy to generate heat in humans, so the activation of human brown adipose tissue represents an opportunity to increase energy expenditure and weight loss alongside improved lipid and glucose homeostasis. However, no pharmacologic therapy has proved to be safe and effective for activation of brown adipose tissue. Our previous studies showed that berberine(BBR), a traditional Chinese herb, can decrease body weight and improve glucose and lipid metabolism. Further genome-wide microarray screening test showed that BBR treatment could induce the expression of UCP-1, which is confirmed by western blot in brown adipose tissue of SD rat. Therefore, BBR could promote the thermogenesis of brown adipose tissue, but the mechanism is still unclear. Since our genome-wide microarray screening results also showed that the retinoic acid pathway, a cellular signaling pathway related to UCP-1 expression regulation, is also activated after BBR treatment. we speculated that BBR activated the thermogenesis and energy expenditure of brown adipose tissue through the up-regulation of retinoic acid pathway.To verify this assumption, we plan to construct retinoic acid receptor (RAR/RXR) knock-down animal and celluar model, and detect the UCP1 expression and energy expenditure rate after BBR treatment, so that we can demonstrate the role and mechanisms of BBR in promoting thermogenesis and energy expenditure of the brown adipose tissue.

能量过剩是造成肥胖及其相关多种糖脂代谢疾病的重要根源。近年来，国外研究证实正常成年人体内存在棕色脂肪组织，其在机体耗能产热方面发挥重要作用，可能成为治疗肥胖及相关疾病的有效靶点。然而，真正安全有效的棕色脂肪激活剂仍未被发现。申请人课题组前期研究表明盐酸小檗碱（BBR）有减肥、降糖降脂和降低肝脏脂肪等多重代谢改善作用，且全基因组芯片筛查发现BBR可诱导肝脏组织表达解偶联蛋白(UCP1)。给大鼠BBR灌胃一周，发现BBR明显上调寒冷诱导的棕色脂肪UCP1表达，初步证实BBR具有促进棕色脂肪功能作用，提示其可激活棕色脂肪产热耗能，但具体机制尚不清楚。结合本课题组基因芯片结果示视黄酸通路与UCP1相关且在应用BBR后显著上调，我们推测BBR可能通过视黄酸通路促进棕色脂肪产热耗能。为证实这一推测，本项目拟构建视黄酸受体敲低动物和细胞模型，分别从整体代谢和分子水平阐明BBR促棕色脂肪产热作用和机制。

随着人类饮食结构和生活方式的改变，肥胖已成为影响人类健康的重要全球化健康问题。造成人体肥胖的重要根源是能量过剩。近年来，国外研究证实正常成人体内存在活性棕色脂肪组织，可发挥产热耗能活性，成为治疗肥胖及相关代谢疾病的重要靶点。本课题基于前期对小檗碱减肥、降糖降脂和降低肝脂肪含量的作用和机制探索，进一步研究小檗碱促进人体脂肪组织棕色化和产热耗能作用。研究发现：（1）小檗碱干预对临床合并非酒精性脂肪性肝病患者有显著的减肥、减轻肝脏脂肪沉积和改善胰岛素抵抗的作用。（2）从脂肪细胞、实验小鼠和人体三个层面，证明小檗碱可促进棕色脂肪组织分化，并动员其产热耗能活性。机制研究表明小檗碱可上调前棕色脂肪细胞的PRDM16表达，通过结合MED1形成复合体靶向调控脂肪棕色化相关基因，发挥促棕色化作用。通过PRDM16 ShRNA敲减棕色脂肪细胞的PRDM16表达，可抑制小檗碱诱导的棕色脂肪细胞分化以及棕色脂肪产热耗能活性。（3）通过基因芯片方法发现小檗碱干预引起棕色脂肪细胞多条信号通路的变化，包括小檗碱对于Hedgehog通路的抑制以及其对具有抑制前棕色脂肪分化作用的GATA2/3基因下调。本研究首次在人体上探索发现了小檗碱促进棕色脂肪活性的作用，为临床上干预治疗肥胖症及其相关糖脂代谢异常疾病提供了新的有效治疗手段。通过对小檗碱促进脂肪组织棕色化分子机制的探索，可以深化对棕色脂肪细胞生理功能和调控机制的认识，为临床设计靶向棕色脂肪细胞激活剂提供新的有效靶点。