Revealing Leptin and Adiponectin Involvement in Endothelial Cell Response to Disturbed Flow
Authors: Anlar Gulsen , Kamareddine Layla , Zeidan Asad 
Published: May 2022

Background and Aims

Endothelial cells (ECs) line on the inner surface of the blood vessels and responsible from sensing and responding to mechanical forces of blood flow, to maintain vascular homeostasis. On the bifurcations and inner curves of arteria, ECs are exposed to multidirectional disturbed flow. Whereas, on the other parts of arteria, blood flow is unidirectional laminar flow. In response to disturbed flow, EC permeability, nitric oxide (NO) bioavailability, and tissue repair mechanisms are affected. As a result, increased inflammatory response occurs. Disturbed flow induced endothelial dysfunction and inflammation can cause atherosclerosis, which is a life threatening, chronic inflammatory disease of arteria characterized by disruption of blood flow via plaque formation. Discovering the molecules that mediate endothelial response leading to inflammatory diseases is important to develop early detection, prevention, and treatment methods. In the present study, two adipokines were investigated: A proinflammatory protein leptin that is related to cardiovascular (CV) risk factors and an anti‐inflammatory protein adiponectin (APN) that has cardioprotective functions. Considering their roles in CV diseases, the present study aimed to investigate whether leptin and APN are involved in EC response to proatherogenic disturbed flow.

Methods

Orbital shaker (Grant Instruments, UK) was used to generate laminar and disturbed flow conditions on cultured human endothelial cells (EA.hy926) by applying 10mm diameter circulatory flow with speed of 210rpm. ECs were exposed to fluid flow for different time points (6h, 15h, 24h, and 48h). Real time polymerase chain reaction (RT‐PCR) was performed to study gene expressions.

Results

Generation of laminar flow condition was confirmed via increased endothelial NO synthase (eNOS) by 1.964 ± 1.015 folds (n=8, p,0.05); disturbed condition via increased expression of inflammatory molecules, such as, e‐Selectin, by 2.075 ± 1.154 folds (n=8, p,0.05) and VCAM1 by 2.329 ± 1.540 folds (n=8, p,0.05). This study showed that mRNA expressions of intracellular leptin as well as APN increased by 3.559 ± 2.207 folds (n=8, p,0.05), and by 2.697 ± 1.713 folds (n=8, p<0.05) respectively, in response to disturbed flow, compared to static and laminar flow conditions. Further, APN receptor‐2 (APNR‐2) expression was downregulated by 0.5761 ± 0.2516 folds (n=8, p,0.05) in ECs following disturbed flow exposure, while leptin receptor expression alterations remained non‐significant.

Conclusion

The obtained results of this study indicate that disturbed flow upregulates leptin and APN expressions along with inflammatory molecules (VCAM1 and e‐Selectin). Knowing that leptin plays role in inflammation activation and CV disease development, confirming its relationship with EC inflammatory response to disturbed flow is logic. However, disturbed flow induced expression of cardioprotective, and anti‐inflammatory APN, is contradicting. On the other hand, APNR‐2 reduction shows reduced APN effect.