2型糖尿病大鼠模型,动物造模 z-bio 2021-05-14 683

　　Abstract: This is an exploratory study that uses a new imaging method, quantitative ultra-short echo time, contrast enhanced (QUTE-CE) magnetic resonance imaging to evaluate the permeability of the blood-brain barrier in a rat model of type 2 diabetes. Assume that small vessel disease is a contributing factor to diabetic neuropathy.

　　Method: The changes in the permeability of the blood-brain barrier in BBZDR/Wor rats (type 2 diabetes model) and age-matched control rats were studied. QUTE-CE is a quantitative vascular biomarker that generates more than 500,000 voxel angiography images, which are registered in the 3D MRI rat brain atlas, providing specific indicators of the permeability of the blood-brain barrier in 173 different brain regions location information.

　　Result: In this diabetes model, without the support of insulin treatment, more than 84% of the brain showed a significant increase in the permeability of the blood-brain barrier compared with the wild-type control group. The areas of the dopaminergic system in the cerebellum and midbrain were not significantly affected.

　　Conclusion: According to the assessment of the permeability of the blood-brain barrier, small vessel diseases in type 2 diabetes models are widespread, including most of the brain. The increased permeability of the blood-brain barrier may be a factor leading to diabetic encephalopathy and dementia.

　　Background: Vascular dementia is a serious consequence of diabetes. Long-term exposure to hyperglycemia (typically type 2 diabetes) can affect the structure, function, and permeability of the capillary endothelium. The destruction of the blood-brain barrier is the basis of cerebral small vascular disease and contributes to the onset of diabetic encephalopathy. Methods to quantify and locate the permeability changes of the blood-brain barrier in vivo are needed to understand and diagnose the early onset of type 2 diabetic vascular dementia. It is not possible to image subtle changes in blood-brain permeability using standard imaging protocols, but it can be assessed by dynamic contrast enhanced (DCE) MRI. However, dynamic enhanced MRI has some limitations. DCE-MRI has not been proven clinically useful. Due to the short acquisition time of the contrast agent and the strong dependence on microstructure characteristics (such as blood vessel size, curvature and direction), it is difficult to simulate the effect of the contrast agent on T2* and T1. In order to solve this problem, a new imaging method, quantitative ultra-short echo time, contrast-enhanced (QUTE-CE) MRI was used to study the blood of BBZDR/Wor rats (an inbred type 2 diabetes rat model). Changes in the brain barrier.

　　Animals: This study uses male Zucker diabetic rats (BBZDR/Wor rats) (n = 8) and age-matched non-diabetic BBDR littermates (n = 7). Obese male BBZDR/Wor rats spontaneously develop type 2 diabetes at about 10 weeks of age (~100%) after being fed standard rat diets. BBZDR/Wor diabetic rats showed all the clinical symptoms typically associated with type 2 diabetes, including dyslipidemia, hyperglycemia, insulin resistance and hypertension. The rats consumed food and water ad libitum, and were treated with intraperitoneal injection of saline when there were signs of weight loss.

　　Imaging: The study was done on a Bruker Biospec 7.0 T / 20 cm USR horizontal magnet and a 20-G / cm magnetic field gradient insert (ID = 12 cm) with a rise time of 120μs. Use the quadrature volume coil built into the rat restraint to send and receive radio frequency signals. All rats were imaged under 1-2% isoflurane while maintaining a respiratory rate of 40-50 breaths/min. The rats were imaged before and after intravenous injection of 6 mg/ml ferumoxytol. The injection volume is tailored for each rat (assuming blood accounts for 7% of body weight) to produce an initial blood concentration of 200μg/ml Fe (a clinical dose approved for humans). The QUTE-CE MRI image parameters of TE = 13µs, TR = 4 ms and flip angle = 20° utilize a high RF pulse bandwidth of 200 kHz. Therefore, compared with the approximate ferumoxytol concentration of T2 (3.58 mM is 4.58 ms, which is 200 µg/ml), the pulse duration is short (6.4 µs) to minimize signal blur and reduce the probability of the curved trajectory of the magnetization vector Mz. Using a 3×3×3cm3 field of view, the matrix grid size is 180×180×180 to produce an isotropic resolution of 167μm. Use the matlabspm12 toolbox developed by UCL to perform motion correction, spatial alignment and re-segmentation of the image. The UTE image before comparison is set as the baseline. For each rat in each imaging session, the voxel percentage change in signal intensity is calculated as (after con-baseline)/(blood intensity change)*100%, as described in our previous work, where the blood intensity change is The normalization factor calculated by subtracting the baseline blood signal intensity from the blood signal intensity after con. Taking into account the changes in brain size and location, the rat brain atlas of 173 regions was fitted to the T2-weighted RARE anatomical data set of each rat data set collected by each imaging.

　　Results: Table 1 shows all brain regions (147/173) with significantly different blood-brain barrier permeability between BBZDR/Wor rats and their littermate control group. Note: In all cases, BBZDR/Wor rats showed greater permeability. The location of these regions can be visualized in the surrounding 2D and 3D images generated by the rat MRI atlas shown in Figure 1. Compared with the control group, the permeability of the blood-brain barrier in all red areas in the 2D images of BBZDR/Wor rats was significantly increased. Table 2 shows all brain regions (26/173) where there is no significant difference in the permeability of the blood-brain barrier between the BBZDR/Wor rat and its littermate control group. These areas shown in white are located in the frontal lobe ctx, midbrain and cerebellum. These unaffected areas are shown in yellow in the brain.

　　Discussion: QUTE-CE MRI was developed as a quantitative vascular biomarker. The contrast agent is ferumoxytol, a superparamagnetic iron oxide nanoparticle coated with dextran. Because its size exceeds the critical value of glomerular filtration (~ 6nm), ferumoxytol will not be cleared by the kidneys, but is an excellent contrast agent with an intravascular half-life of  ~ 15h. A large number of clinical magnetic resonance imaging studies have been carried out on children and adults, and it has been proved that there are no major side effects. Therefore, QUTE-CE can be easily used for clinical research on the permeability of the blood-brain barrier. QUTE-CE MRI can identify high or low vascularization, small blood vessel density, blood-brain barrier permeability and vascular reserve, and the responsiveness of blood vessels to CO2 stimulation at the single voxel and regional level. This study took preclinical type 2 diabetes model BBZDR/Wor rats as the research object, and proved that the imaging technology can be used for clinical diagnosis and evaluation of blood-brain permeability and disease progression of diabetic encephalopathy.

　　Conclusion: Through the evaluation of the permeability of the blood-brain barrier, it is found that small vessel diseases in type 2 diabetes models are widespread, including most of the brain. The increased permeability of the blood-brain barrier may be a factor leading to diabetic encephalopathy and dementia.