目的:蛋白酶激活受体1(PAR1)已成为凝血和肥胖并发症(包括代谢功能障碍相关的脂肪变性肝病(MASLD))之间的重要联系。PAR1由各种细胞表达并被不同的蛋白酶切割以产生激活不同信号传导途径的独特的束缚激动剂。表达具有R41Q突变的PAR1的小鼠已经禁用了典型的凝血酶介导的信号传导,而R46Q小鼠表达对活化蛋白C(APC)的非规范信号传导具有抗性。
方法:全身和肝细胞选择性PAR1缺乏的小鼠,以及PAR1R41Q和R46Q小鼠饲喂高脂饮食以诱导MASLD。
结论:高脂肪饮食(HFD)喂养的R41Q小鼠表现出降低的肝脂肪变性和肝/体重比。相比之下,HFD喂养的R46Q小鼠显示增加的相对肝脏重量和肝脏脂肪变性以及增加的血清ALT活性。令人惊讶的是,尽管PAR1突变对脂肪变性有明显影响,肝细胞中PAR1的选择性缺失没有影响。为了评估可行的PAR1目标方法,用变构PAR1调节剂NRD-21治疗患有HFD诱导的肥胖的小鼠,其抑制典型的PAR1炎症信号但促进PAR1保护性,非规范的抗炎信号。NRD-21治疗降低血浆TNFα,血清ALT活性,肝脂肪变性,和胰岛素抵抗(HOMA-IR),但增加血浆活性GLP-1。结果表明,非肝细胞规范PAR1切割驱动肥胖小鼠的MASLD,并提供翻译概念证明,PAR1的选择性药理学调节在实验性肥胖中产生多种代谢益处。
BACKGROUND: Protease-activated
receptor-1 (PAR1) has emerged as an important link between coagulation and the complications of obesity including metabolic dysfunction-associated steatotic liver disease (MASLD). PAR1 is expressed by various cells and cleaved by different proteases to generate unique tethered agonists that activate distinct signaling pathways. Mice expressing PAR1 with an R41Q mutation have disabled canonical thrombin-mediated signaling, whereas R46Q mice express PAR1 resistant to noncanonical signaling by activated protein C.
METHODS: Mice with whole body and hepatocyte-selective PAR1 deficiency as well as PAR1 R41Q and R46Q mice were fed a high-fat diet (HFD) to induce MASLD.
RESULTS: HFD-fed R41Q mice displayed reduced hepatic steatosis and liver/body weight ratio. In contrast, HFD-fed R46Q mice displayed increased relative liver weight and hepatic steatosis alongside increased serum alanine aminotransferase activity. Surprisingly, despite the distinct impact of PAR1 mutations on steatosis, selective deletion of PAR1 in hepatocytes had no impact. To evaluate a viable PAR1-targeted approach, mice with HFD-induced obesity were treated with the allosteric PAR1 modulator NRD-21, which inhibits canonical PAR1 inflammatory signaling but promotes PAR1 protective, noncanonical anti-inflammatory signaling. NRD-21 treatment reduced plasma tumor necrosis factor-alpha, serum alanine aminotransferase activity, hepatic steatosis, and insulin resistance (Homeostatic Model Assessment for Insulin Resistance) but increased plasma active glucagon-like peptide-1.
CONCLUSIONS: The results suggest that nonhepatocellular canonical PAR1 cleavage drives MASLD in obese mice and provide translational proof-of-concept that selective pharmacologic modulation of PAR1 yields multiple metabolic benefits in experimental obesity.