Three-dimensional-arterial spin labeling perfusion correlation with diabetes-associated cognitive dysfunction and vascular endothelial growth factor in type 2 diabetes mellitus rat

Abstract

Background: Type 2 diabetes mellitus (T2DM) has been strongly associated with an increased risk of developing cognitive dysfunction and dementia. The mechanisms of diabetes-associated cognitive dysfunction (DACD) have not been fully elucidated to date. Some studies proved lower cerebral blood flow (CBF) in the hippocampus was associated with poor executive function and memory in T2DM. Increasing evidence showed that diabetes leads to abnormal vascular endothelial growth factor (VEGF) expression and CBF changes in humans and animal models. In this study, we hypothesized that DACD was correlated with CBF alteration as measured by three-dimensional (3D) arterial spin labeling (3D-ASL) and VEGF expression in the hippocampus.

Aim: To assess the correlation between CBF (measured by 3D-ASL and VEGF expression) and DACD in a rat model of T2DM.

Methods: Forty Sprague-Dawley male rats were divided into control and T2DM groups. The T2DM group was established by feeding rats a high-fat diet and glucose to induce impaired glucose tolerance and then injecting them with streptozotocin to induce T2DM. Cognitive function was assessed using the Morris water maze experiment. The CBF changes were measured by 3D-ASL magnetic resonance imaging. VEGF expression was determined using immunofluorescence.

Results: The escape latency time significantly reduced 15 wk after streptozotocin injection in the T2DM group. The total distance traveled was longer in the T2DM group; also, the platform was crossed fewer times. The percentage of distance in the target zone significantly decreased. CBF decreased in the bilateral hippocampus in the T2DM group. No difference was found between the right CBF value and the left CBF value in the T2DM group. The VEGF expression level in the hippocampus was lower in the T2DM group and correlated with the CBF value. The escape latency negatively correlated with the CBF value. The number of rats crossing the platform positively correlated with the CBF value.

Conclusion: Low CBF in the hippocampus and decreased VEGF expression might be crucial in DACD. CBF measured by 3D-ASL might serve as a noninvasive imaging biomarker for cognitive impairment associated with T2DM.

Keywords: Diabetes mellitus; Diabetes-associated cognitive dysfunction; Hippocampus; Perfusion imaging; Receptors; Three-dimensional pseudo-continuous arterial spin labeling; Type 2; Vascular endothelial growth factor.

Figure 1

Representative swimming trajectories of rats. A: Control group; B: Comparison with the control group, the swimming trajectory of the rats in the type 2 diabetes mellitus group was more chaotic.

Figure 2

Results of the Morris water maze test of each group. A: Latency time on the third, fourth, and fifth day (^aP < 0.05); B: The total distance reach the platform was recorded in the hidden platform tests on the fifth day (P < 0.01); C: Number of crossing times of the target platform within 2 min (P < 0.01); D: Effects of different groups on the distance in zone-platform (P < 0.05). T2DM: Type 2 diabetes mellitus.

Figure 3

Comparison of cerebral blood flow in hippocampal area between type 2 diabetes mellitus group and control group. A: Representative cerebral blood flow (CBF) images of the bilateral hippocampus area (orange arrow) in the control group; B: Representative CBF images of the bilateral hippocampus area (orange arrow) in type 2 diabetes mellitus (T2DM) group; C: Significantly different CBF values between the control and T2DM groups in the left hippocampus (P < 0.01); D: Significantly different CBF between the control and T2DM groups in the right hippocampus (P < 0.01).

Figure 4

Images of vascular endothelial growth factor immunofluorescence staining of the hippocampus in each group. A: Nucleus in the type 2 diabetes mellitus group (blue); B: Vascular endothelial growth factor levels in the type 2 diabetes mellitus group (green); C: Merged image for the type 2 diabetes mellitus group; D: Nucleus in the control group (blue); E: Vascular endothelial growth factor levels in the control group (green); F: Merged image for the control group. Scale bar, 100 µm.

Figure 5

Expression of vascular endothelial growth factor was lower in the type 2 diabetes mellitus group than in the control group (P < 0.05). T2DM: Type 2 diabetes mellitus; VEGF: Vascular endothelial growth factor.

Figure 6

Good relationship was found between cerebral blood flow value and vascular endothelial growth factor expression among the type 2 diabetes mellitus group. A: Positive correlation between left cerebral blood flow (CBF) and vascular endothelial growth factor (VEGF) (rho = 0.7762, P < 0.01); B: Positive correlation between right CBF and VEGF (rho = 0.7902, P < 0.01). Unit for CBF value is mL/min/100 g. T2DM: Type 2 diabetes mellitus.

Figure 7

Correlation between cerebral blood flow value and cognitive dysfunction. A: The escape latency negatively correlated with the cerebral blood flow (CBF) value (P < 0.01); B: The number of rats crossing the platform positively correlated with the CBF value (P < 0.05); C: A significant positive correlation was found between CBF and distance in the zone target (rho = 0.587, P < 0.05).