Abstract Background Obesity is a global pandemic associated with increased cardiovascular risk and mortality. Changes in whole-body metabolism, vascular health and the immune system induce a pro-inflammatory environment and disrupt intercellular crosstalk. Targeting incretin signalling pathways, including glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP), has recently emerged as an effective weight-lowering strategy with pleiotropic metabolic and cardiovascular benefits. However, the underlying mechanisms remain elusive, specifically the direct effects of incretins on endothelial cells (EC) and adipocytes. Purpose We hypothesize that GLP-1, GIP and the dual receptor agonist tirzepatide (TZP) directly modulate metabolism and function of both EC and adipocytes, thereby exerting positive vasoprotective effects beyond weight loss. This project aims to elucidate those effects in healthy condition as well as in an obesity-associated meta-inflammatory environment. Methods Human umbilical vein endothelial cells (HUVEC) were treated with 100 nM GIP, GLP-1 or TZP with or without a pro-inflammatory cytokine mix (1.25 ng/mL TNFα, 2.5 ng/mL IL6, 0.25 ng/mL IL1β and 1.25 ng/mL IFNy) for 24 hours to mimic obesity induced chronic low-grade inflammation. In parallel, 3T3-L1 pre-adipocytes were exposed to the same mix of pro-inflammatory cytokines at different stages of differentiation (at days -3, 0, 3 and 6 from the start of differentiation). Cellular function and metabolic responses were assessed using Western Blot analysis, qPCR and Seahorse extracellular flux analysis. Results The cytokine mix activated endothelial inflammatory markers VCAM and ICAM at RNA and protein levels in HUVEC. In contrast, incretin treatments alone do not alter these adhesion molecules. Seahorse extracellular flux analysis revealed that GLP-1 and TZP enhanced mitochondrial activity under basal condition, by increasing basal respiration and proton leak, while GIP had no effect. Under inflammatory condition, proton leak was significantly increased in cells with and without incretin treatment. Notably, this effect was reduced in TZP-treated cells compared to cells without incretin exposure. Preliminary data from 3T3-L1 pre-adipocytes revealed time-dependent effects of exposure to the cytokine mix during differentiation. Exposure prior to differentiation enhanced adipogenic marker gene expression (Adip), whereas exposure from day 3 onwards induced the strongest induction of inflammatory markers (Il6, Tnfa, Ccl2). Late exposure resulted in lower inflammatory induction while maintaining elevated Glp1 gene expression. Conclusion Our preliminary findings demonstrate that TZP counteracts cytokine-induced proton leak in HUVEC, while the same cytokine mix exerts time-dependent effects on 3T3-L1 pre-adipocyte differentiation and inflammatory activation. Further investigation will better characterize the effect of incretins on both endothelial cells and adipocytes.
Krajic et al. (Fri,) studied this question.