Introduction: Glucagon-like peptide-1 (GLP-1) based therapy is a novel treatment for type 2 Diabetes. GLP-1 receptor agonists and inhibitors of dipeptidyl peptidase IV improve glycemic control. GLP-1 exerts multiple effects including modulation of a-cell proliferation, apoptosis and exogenesis. Inhibition of gastric emptying and food Intake with stimulation of glucose uptake by adipocytes has also Been reported.
Beneficial effects of GLP-1 on myocardial and endothelial functions. However, the mechanisms underlying these various effects are not fully understood. Therefore, we examined whether the GLP-1 analog liraglutide protects human umbilical vein endothelial cells (HUVECs) from the injurious effects of the proinflammatory cytokine tumor necrosis factor-alpha (TNF-a).
Materials and Method: Cell culture and other materials were obtained. An analysis of reactive oxidative stress (ROS) generation was carried out and the expression of mRNA for the subunits of NADPH oxidase and ptx3 was determined by doing a RT-PCR analysis. NF -kB activation was studied and a western blot analysis was done to determine if the NF -kB activation had taken place. Subcelelular fractionation was carried out to obtain individual samples of each cellular element. An immunoflorescent microscopy of the cells was done and apoptotic cells were detected using the Inage J software. A statistical analysis of the expressed data was done.
Results: TNF-a-induced oxidative stress was attenuated by Liraglutide in a dose-dependent manner. There was also significant reduction in the expression of gp91phox and p22phox, which are essential components of NADPH oxidase. There was also significant up-regulation of mRNA and protein levels of SOD-2 by Ligratulide.
Ligratulide inhibited the translocation of PKC-a into the cell membrane. There was also an inhibition of TNF-a induced NF-kB activation in the cells. There was also an inhibition of THF-a induced apoptosis and PTX3 expression in the cells by Liraglutide. This was shown by a significant reduction in the percentage of apoptotic cells noticed which was in a dose-dependent manner. Also following treatment with Liraglutide, there was a down regulation of PTX2 expression, which suggests that liraglutide has both anti-oxidative and anti-inflammatory effects on the cells.
Discussion
Reactive Oxygen Species lead to development of Diabetic vascular complications. Liraglutide pretreatment for 30 minutes could inhibit Reactive Oxygen Species generation in the cells exposed to TNF-a. PKC is important in several signaling pathways. It acts upstream of NADPH and ROS production in endothelial cells. Liraglutide inhibits NF-kB which mediates inflammation when activated by TNF-a.
Conclusion:
The research suggests that liraglutide has significant anti oxidant and anti-inflammatory effects on endothelial cells in biologically active concentrations. Liraglutide may be important in cardiovascular protection as well as regulating glycemic control.
