Department of Biochemistry, Ewha Womans University College of Medicine, Seoul, 07084, Republic of Korea.
Department of Biochemistry, Gachon University College of Medicine, Incheon, 21565, Republic of Korea.
BMC Pharmacol Toxicol. 2024 Oct 11;25(1):76. doi: 10.1186/s40360-024-00800-3.
The burden of nonalcoholic fatty liver disease is increasing, and limited therapeutic drugs are available for its treatment. Serotonin binds to approximately 14 serotonin receptors (HTR) and plays diverse roles in obesity and metabolic complications. In this study, we focused on the function of HTR4 on nonalcoholic fatty liver disease using GR113808, a selective HTR4 antagonist.
Male C57BL/6J mice were fed high-fat diet for 12 weeks with intraperitoneal GR113808 injection, and HTR expression, weight changes, glucose and lipid metabolism, hepatic fat accumulation, changes in adipose tissue, the changes in transcriptional factors of signaling pathways, and inflammations were assessed. Hep3B cells and 3T3-L1 cells were treated with siRNA targeting HTR4 to downregulate its expression and then cultured with palmitate to mimic a high-fat diet. The changes in transcriptional factors of signaling pathways, and inflammations were assessed in those cells.
After feeding a high-fat diet to male C57BL/6J mice, HTR4 expression in the liver and adipose tissues decreased. GR113808 suppressed body weight gain and improved glucose intolerance. Furthermore, GR113808 not only decreased fatty liver formation but also reduced adipose tissue size. Additionally, GR113808 reduced inflammatory cytokine serum levels and inflammasome complex formation in both tissues. Palmitate treatment in HTR4-downregulated Hep3B cells, also reduced peroxisome proliferator-activated receptor γ and sterol regulatory element-binding protein-1 pathway induction as well as inflammasome complex formation, thus decreasing inflammatory cytokine levels. HTR4 downregulation in 3T3-L1 cells also reduced palmitate-induced inflammasome complex formation and inflammatory cytokine production. Palmitate-induced insulin resistance in Hep3B cells, but not in 3T3-L1 cells, was improved by HTR4 downregulation.
In summary, GR113808 protected against fatty liver formation and improved inflammation in the liver and adipose tissue. Downregulation of HTR4 ameliorated insulin resistance in the liver. These results suggest that HTR4 could serve as a promising therapeutic target for metabolic diseases.
非酒精性脂肪性肝病的负担正在增加，而其治疗方法有限。血清素与大约 14 种血清素受体（HTR）结合，在肥胖和代谢并发症中发挥多种作用。在这项研究中，我们使用选择性 HTR4 拮抗剂 GR113808 关注 HTR4 在非酒精性脂肪性肝病中的功能。
雄性 C57BL/6J 小鼠用高脂肪饮食喂养 12 周，并进行腹腔内 GR113808 注射，评估 HTR 表达、体重变化、葡萄糖和脂质代谢、肝脂肪堆积、脂肪组织变化、信号通路转录因子变化和炎症。用靶向 HTR4 的 siRNA 处理 Hep3B 细胞和 3T3-L1 细胞以下调其表达，然后用棕榈酸培养以模拟高脂肪饮食。评估这些细胞中信号通路转录因子和炎症的变化。
在用高脂肪饮食喂养雄性 C57BL/6J 小鼠后，肝脏和脂肪组织中的 HTR4 表达降低。GR113808 抑制体重增加并改善葡萄糖不耐受。此外，GR113808 不仅减少了脂肪肝的形成，还减少了脂肪组织的大小。此外，GR113808 降低了两种组织中炎症细胞因子的血清水平和炎症小体复合物的形成。HTR4 下调的棕榈酸处理 Hep3B 细胞也降低了过氧化物酶体增殖物激活受体 γ 和固醇调节元件结合蛋白-1 途径的诱导以及炎症小体复合物的形成，从而降低了炎症细胞因子水平。3T3-L1 细胞中 HTR4 的下调也减少了棕榈酸诱导的炎症小体复合物形成和炎症细胞因子的产生。HTR4 下调改善了 Hep3B 细胞而非 3T3-L1 细胞中的棕榈酸诱导的胰岛素抵抗。
总之，GR113808 可防止肝形成脂肪并改善肝脏和脂肪组织的炎症。HTR4 下调改善了肝脏的胰岛素抵抗。这些结果表明 HTR4 可能是代谢性疾病的有前途的治疗靶点。
