Abstract
Objective
Sepsis causes severe hypotension, accompanied by high mortality in the setting of septic shock. LEADER, SUSTAIN-6 and other clinical trials revealed cardioprotective and anti-inflammatory properties of GLP-1 analogs like Liraglutide (Lira). We already demonstrated improved survival by amelioration of disseminated intravasal coagulation (DIC) in lipopolysaccharide (LPS)-induced endotoxemia by inhibition of the GLP-1 degrading enzyme dipeptidylpeptidase-4 (DPP-4). With the present study we aim to investigate the mechanism of protective effects of the GLP-1 analog Lira and the DPP4 inhibitor Linagliptin (Lina) in the clinically relevant sepsis model cecal ligation and puncture (CLP).
Methods
C57/BL6j and endothelial cell-specific GLP-1 receptor knockout mice (Cdh5crexGLP-1rfl/flmice) were used and sepsis was induced by cecal ligation and puncture (CLP). DPP4 inhibitor (Lina, 5mg/kg/d; 3 days) and GLP-1 analog (Lira, 200μg/kg/d; 3 days) were applied subcutaneously. Aortic vascular function was tested by isometric tension recording. Aorta and heart tissue was used for Western blotting, dot blot and qRT-PCR. Endogenous GLP-1 (7–36 and 9–36) and insulin was determined by ELISA. Blood samples were collected for examination of cell count, oxidative stress and glucose levels.
Results
Body temperature was increased by CLP and normalized by Lina and Lira. Sham- and Lira- but not Lina-treated septic mice showed low blood glucose levels compared to healthy controls. Acetylcholine-induced (endothelium-dependent) vascular relaxation in aorta was impaired by CLP. This was accompanied by vascular inflammation and elevation of IL-6, iNOS, ICAM-1, and TNF-alpha mRNA levels in aortic tissue. Vascular, cardiac and whole blood oxidative stress were increased by CLP. Furthermore, we detected higher levels of IL-6, 3-nitrotyrosine (3-NT) and 4-hydroxynonenal (4-NHE) in plasma of CLP animals. Lina and Lira reduced oxidative stress and vascular inflammation, which was accompanied by improved endothelial function. In addition, CLP treatment in endothelial specific knockout mice of the GLP-1r strongly induced mortality compared to WT mice, with the effect being strongest in the Lira-treated group.
Conclusion
The present study demonstrates that Lina (DPP4 inhibitor) and the GLP-1 analog Lira ameliorate sepsis-induced endothelial dysfunction by reduction of vascular inflammation and oxidative stress. Clinical trials like LEADER and SUSTAIN-6 proved that GLP-1 analogs like Lira have cardioprotective effects in T2DM patients. The present study, performed in a clinically relevant model of polymicrobial sepsis, reveals that the known cardioprotective effects of GLP-1 might be translated to other diseases which affect the cardiovascular system like sepsis, underlining the potent anti-inflammatory effects of GLP-1 analogs.
