The DPP-4 inhibitor linagliptin counteracts stroke in the normal and diabetic mouse brain: a comparison with glimepiride

Abstract

Type 2 diabetes is a strong risk factor for stroke. Linagliptin is a dipeptidyl peptidase-4 (DPP-4) inhibitor in clinical use against type 2 diabetes. The aim of this study was to determine the potential antistroke efficacy of linagliptin in type 2 diabetic mice. To understand whether efficacy was mediated by glycemia regulation, a comparison with the sulfonylurea glimepiride was done. To determine whether linagliptin-mediated efficacy was dependent on a diabetic background, experiments in nondiabetic mice were performed. Type 2 diabetes was induced by feeding the mice a high-fat diet for 32 weeks. Mice were treated with linagliptin/glimepiride for 7 weeks. Stroke was induced at 4 weeks into the treatment by transient middle cerebral artery occlusion. Blood DPP-4 activity, glucagon-like peptide-1 (GLP-1) levels, glucose, body weight, and food intake were assessed throughout the experiments. Ischemic brain damage was measured by determining stroke volume and by stereologic quantifications of surviving neurons in the striatum/cortex. We show pronounced antistroke efficacy of linagliptin in type 2 diabetic and normal mice, whereas glimepiride proved efficacious against stroke in normal mice only. These results indicate a linagliptin-mediated neuroprotection that is glucose-independent and likely involves GLP-1. The findings may provide an impetus for the development of DPP-4 inhibitors for the prevention and treatment of stroke in diabetic patients.

FIG. 1.

Experimental design and drug-treatment paradigm.

FIG. 2.

Metabolic phenotype of HFD feeding. A: Body weight gain after HFD treatment. B: IPGTT before and 12 weeks into the HFD. C: IPinsTT before and 12 weeks into the HFD. D: Fasted blood glucose levels before and 12 weeks into the HFD. Data are presented as means ± SEM. *P < 0.05, **P < 0.01, and ***P < 0.001 for a chance difference vs. controls using the Student unpaired t test.

FIG. 3.

Effects of linagliptin and glimepiride on DPP-4 activity, GLP-1 levels, and blood glucose in HFD-fed vs. normal mice. HFD-fed mice: DPP-4 activity (A), GLP-1 levels (B), fed glucose levels (C), and fasted blood glucose levels (5 h) at 1 h after drug administration (D). Normal mice: DPP-4 activity (E), GLP-1 levels (F), fed glucose levels (G), and fasted blood glucose levels (5 h) at 1 h after drug administration (H). Bars represent means ± SEM. One-way ANOVA, followed by Bonferroni post hoc tests was used. *P < 0.05, **P < 0.01, and ***P < 0.001.

FIG. 4.

Neuroprotective effects of linagliptin and glimepiride treatments. A: Ischemic volume (mm³) after 30 min of MCAO in HFD-fed mice. Number of surviving neurons in stroke-damaged striatum (B), cortex (C), and striatum and cortex combined (D) in HFD-fed mice. E: Ischemic volume (mm³) after 30 min of MCAO in nondiabetic mice. Number of surviving neurons in stroke-damaged striatum (F), cortex (G), and striatum and cortex combined (H) in nondiabetic mice. The dashed lines in B, C, F, G, represent the average number of neurons in the brain areas of naïve animals (no stroke) where the neuronal quantification was performed. Bars represent means ± SEM. One-way ANOVA, followed by Bonferoni post hoc tests, was used. *P < 0.05, **P < 0.01. K: An illustration of typical brain damage in our stroke model. I and J: Photomicrographs of the area of the cortex illustrated in L on the contralateral, nondamaged, side of the brain, show normal neuronal density. Photomicrographs of the area (L) of the stroke-damaged cortex in HFD (M–O) and normal diet (P–R) illustrating the changes in neuronal density in vehicle, linagliptin, and glimepiride-treated mice, respectively. All photomicrographs have been enhanced with high-contrast monochromatic adjustment for better visual representation on small images.

FIG. 5.

GLP-1R expression in the mouse cerebral cortex. A: Low magnification image of GLP-1R expression in cortex. B: High magnification image corresponding to the white borders square within panel A. Split channel images show immunoreactivity for NeuN (C), GLP-1R (D), and DAPI (E).