Unveiling the Anti-Inflammatory Potential of Olive Leaf Phenolic Extracts in Diabetes-Related Endothelial Dysfunction

Ilaria Cappellacci^1,2Nadia Di Pietrantonio^1,2Davide Viola^1,2GLORIA FORMOSO^2,3Małgorzata Elżbieta Zujko⁴Beatriz Martín-García^5,6Ana Maria Gomez-Caravaca^5,6Vito Verardo⁷Assunta Pandolfi^1,2Caterina Pipino^1,2*

• ¹Department of Medical, Oral and Biotechnological Sciences, University of Studies G. d'Annunzio Chieti and Pescara, Chieti, Italy
• ²Center for Advanced Studies and Technology (CAST), University G. d’Annunzio Chieti-Pescara, Chieti, Italy
• ³Department of Medicine and Aging Sciences, University of Studies G. d'Annunzio Chieti and Pescara, Chieti, Italy
• ⁴Department of Food Biotechnology, Faculty of Health Science, Medical University of Białystok, Białystok, Poland
• ⁵Department of Analytical Chemistry, University of Granada, Granada, Spain
• ⁶Institute of Nutrition and Food Technology ‘José Mataix’, Biomedical Research Centre, University of Granada, Granada, Spain
• ⁷Department of Nutrition and Food Science, University of Granada, Granada, Spain

Diabetes mellitus is a severe metabolic disorder strongly linked to vascular complications driven by endothelial dysfunction, chronic inflammation, and oxidative stress. Novel strategies to mitigate endothelial activation are urgently needed. In this context, phenolic compounds derived from olive leaves, a byproduct of olive oil production, have shown promising potential in counteracting diabetes-associated endothelial inflammation. This study investigates the potential anti-inflammatory effect of polyphenol-rich extracts derived from two olive leaves Spanish monocultivars, Picual and Changlot Real, in human umbilical vein endothelial cells from healthy pregnancies (C-HUVEC) and gestational diabetes (GD-HUVEC), which serve as a relevant in vitro model of hyperglycemia-induced endothelial dysfunction. Olive leaf extracts were characterized by HPLC-ESI-TOF-MS. C-HUVEC and GD-HUVEC were treated with the extracts, and pro-inflammatory markers expression (NF-κB p65, MCP-1, and VCAM-1), NF-κB p65 phosphorylation, and monocyte adhesion were assessed under basal and TNFα-stimulated conditions using RT-PCR, flow cytometry, and adhesion assays. Both Picual and Changlot Real extracts showed no cytotoxicity at concentrations up to 50 μg/mL. Treatment with 10 μg/mL of both extracts significantly reduced NF-κB p65 and MCP-1 gene expression, as well as NF-κB p65 phosphorylation, particularly in GD-HUVEC. VCAM-1 protein expression and TNFα-induced monocyte adhesion were also significantly decreased following extract treatment. Notably, Changlot Real exhibited a broader anti-inflammatory effect across both cell types, while Picual exerted a more selective effect in GD-HUVEC. These findings support the anti-inflammatory activity of olive leaf polyphenols and highlight the potential of Changlot Real and Picual extracts in mitigating endothelial dysfunction associated with diabetes. By modulating the NF-κB–VCAM-1 axis, these compounds may attenuate endothelial activation, warranting further investigation into their possible role in the prevention or mitigation of diabetes-related vascular complications.