Neuroprotective effects of liraglutide for stroke model of rats

Abstract

The number of diabetes mellitus (DM) patients is increasing, and stroke is deeply associated with DM. Recently, neuroprotective effects of glucagon-like peptide-1 (GLP-1) are reported. In this study, we explored whether liraglutide, a GLP-1 analogue exerts therapeutic effects on a rat stroke model. Wistar rats received occlusion of the middle cerebral artery for 90 min. At one hour after reperfusion, liraglutide or saline was administered intraperitoneally. Modified Bederson's test was performed at 1 and 24 h and, subsequently, rats were euthanized for histological investigation. Peripheral blood was obtained for measurement of blood glucose level and evaluation of oxidative stress. Brain tissues were collected to evaluate the level of vascular endothelial growth factor (VEGF). The behavioral scores of liraglutide-treated rats were significantly better than those of control rats. Infarct volumes of liraglutide-treated rats at were reduced, compared with those of control rats. The level of derivatives of reactive oxygen metabolite was lower in liraglutide-treated rats. VEGF level of liraglutide-treated rats in the cortex, but not in the striatum significantly increased, compared to that of control rats. In conclusion, this is the first study to demonstrate neuroprotective effects of liraglutide on cerebral ischemia through anti-oxidative effects and VEGF upregulation.

Figure 1

Amelioration in behavioral scores. Post-stroke administration of liraglutide reduced modified Bederson’s score at 24 h after reperfusion, although the scores of both groups did not differ at one hour after reperfusion just before administration of liraglutide or saline. * p < 0.05 vs. control group.

Figure 2

Reduced and partially recovered cortical blood flow at MCAO and reperfusion. Cortical blood flow was reduced to almost half at MCAO and recovered to 70%–80% at reperfusion. There was no difference between both groups. * p < 0.05 vs. CBF before suture insertion.

Figure 3

Reduced infarct volumes in rats receiving liraglutide. Representative images of TTC staining of rats in control (A) and liraglutide-treated groups (B) demonstrate remarkable reduction of infarct volumes in liraglutide-treated rats. The graph shows the significant differences in infarct volumes (C). * p < 0.05 vs. control group.

Figure 4

Reduced oxidative stress in liraglutide-treated rats. The graph shows significant reduction in level of d-ROMs in liraglutide-treated rats. * p < 0.05 vs. control group.

Figure 5

VEGF upregulation in the cortex of rats receiving liraglutide. Upper graph: The graph demonstrates significant increase of VEGF level in the cortex of liraglutide-treated rats; Lower graph: The level of VEGF in the striatum was not increased by administration of liraglutide. Infarct/Intact means tissues in the infarct/intact side, respectively. * p < 0.05 vs. control group.

Figure 6

Experimental design. Rats in control and liraglutide-treated groups underwent MCAO surgery with subsequent reperfusion at 90 min after the occlusion. Behavioral test was performed at 1 and 24 h after reperfusion. Blood was sampled from caudal vein to evaluate oxidative stress and blood glucose level. Then rats were euthanized for histological evaluation and protein assay at 24 h.