Dual Endothelin-1 Receptor A/B Blockade Attenuates Adipose Tissue Inflammation in Mice Fed a High Fat Diet

Endothelin-1 (ET-1) is a potent vasoconstrictor and proinflammatory protein that is increased in adipose tissue of high fat diet (HFD) fed mice and contributes to cardiovascular and metabolic disease risk in obesity. Obesity causes adipose tissue hypoxia followed by infiltration of pro-inflammatory T cells and macrophages, adipocyte dysfunction (adipokine dysregulation and inability to store excess energy), and eventual peripheral insulin resistance. Our lab recently reported that adipocyte knockout of the ETB receptor (adETBKO) led to robust attenuation of adipose tissue inflammation, reduction in circulating adiponectin, and increased insulin sensitivity in mice fed HFD. Therefore, we hypothesized that treatment with macitentan, a dual ETA/ETB receptor antagonist, will reduce cardio-metabolic disease risk similar to what is observed in obese adETBKO mice. To test this hypothesis, C57BL/6J mice were fed either normal diet (NMD) or HFD for 8 weeks followed by 2 weeks of treatment with either vehicle or macitentan (30mg/kg/day) while diet was maintained. HFD mice had significantly higher fat mass than NMD mice, with no significant effect of treatment with macitentan. In addition, hypoxia inducible factor alpha ( Hif-1α ) mRNA, which increases as oxygen tension decreases, was elevated in visceral adipose of HFD fed mice compared to NMD (30963±3755 vs. 49771±5954 copies per 50 ng RNA; NMD vs. HFD; p<0.05 by two-way ANOVA). Macitentan reduced Hif-1α transcripts in NMD fed mice and attenuated the increase in HFD fed mice (25050±2982 vs. 32353±5061 copies per 50 ng RNA; NMD vs. HFD). Likewise, HFD fed mice had a significant increase in the proinflammatory cytokine tumor necrosis factor α mRNA (241±50.1 vs. 792.3±120.4 copies per 50 ng RNA; NMD vs. HFD; p<0.0001) in visceral adipose that was attenuated in mice treated with macitentan (209±29 vs. 431±44 copies per 50 ng RNA; NMD macitentan treated vs. HFD macitentan treated). Further, mRNA copies of the cytokines interleukin (IL) 10 and 12b were increased in visceral adipose of mice fed HFD compared to NMD (102±21 NMD vs. 283±58 HFD and 16±4 NMD vs 106±28 HFD copies per 50 ng RNA; IL10 and IL12b, respectively; both p<0.05 by two-way ANOVA), and this increase was attenuated by treatment with macitentan, (90±14 NMD vs. 170±37 HFD and 16±3 NMD vs. 55±14 HFD copies per 50 ng RNA; IL10 and IL12b, respectively). As expected, adiponectin mRNA was significantly reduced in HFD fed mice compared to NMD, however, there was no detectable difference in macitentan treated mice, suggesting that ETB receptor inhibition was not achieved at the adipocytes. Taken together, these data suggest that ET-1 receptor blockade with macitentan improves inflammation in visceral adipose tissue of obese mice. We predict that this is achieved in part by increasing oxygen delivery to the adipose tissue, but not through direct inhibition of ETB receptors on adipocytes. This work was funded by NIH grants R25 HL121042, P20 GM104357, R01 DK124327, and T32 HL105324. This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.