Abstract: Objective   To explore whether type 2 diabetes mellitue (DM) aggravates the spatial learning and memory impairment in rats with chronic cerebral hypoperfusion (CCH) and the possible mechanism. Methods  Twenty-four Sprague-Dawley (SD) rats were randomly divided into 4 groups: control group (normal diet + sham); DM group [high-fat diet + streptozocin (STZ) injection]; CCH group [normal diet + two vessel occlussion (2-VO)] and DM + CCH group (high-fat diet + STZ injection + 2-VO). All rats were submitted to behavioral testing for spatial learning and memory in Morris water maze test, and immunofluorescence staining to detect hippocampal β-site amyloid precursor protein cleaving enzyme 1 (BACE-1) positive cells. The relative expressions of BACE-1 in hippocampus were detected with Western blotting. Results  Morris water maze test showed escape latency of DM + CCH group was significantly longer than control group on 2nd-5th days [(54.60 ± 3.75) s vs (25.99 ± 4.10) s, P = 0.000; (45.39 ± 2.78) s vs (27.50 ± 4.39) s, P = 0.003; (39.71 ± 3.47) s vs (20.34 ± 3.69) s, P = 0.001; (41.43 ± 4.48) s vs (11.35 ± 3.95) s, P = 0.000]. The percentage of target quadrant time in DM + CCH group on the 6th day was significantly reduced compared with the control group [(22.38 ± 3.41)% vs (43.69 ± 3.22)%, P = 0.000]. Compared with control group, BACE-1 positive cells significantly increased in the hippocampus of DM + CCH group, and the relative expression of BACE-1 increased statistically (0.23 ± 0.04 vs 0.06 ± 0.02, P = 0.005). Conclusions  Type 2 diabetes mellitus exacerbates spatial learning and memory impairment of rats with chronic cerebral hypoperfusion, which may be related to the abnormal expression of BACE-1 in the hippocampus of rats.

Key words: Diabetes mellitus, type 2, Cognition disorders, Hippocampus, Amyloid precursor protein secretases, Fluoroimmunoassay, Immunoblotting, Disease models, animal

摘要： 目的  探讨2 型糖尿病（DM）加重慢性脑低灌注（CCH）大鼠空间学习记忆能力损害及其可能机制。方法 成年雄性Sprague-Dawley 大鼠经高脂饮食饲养4 周后予小剂量链脲佐菌素腹腔注射制备2型糖尿病模型、双侧颈总动脉永久性结扎制备慢性脑低灌注模型。采用Morris水迷宫实验测试大鼠空间学习记忆能力，免疫荧光染色和Western blotting 法检测海马淀粉样前体蛋白β位点剪切酶-1（BACE-1）阳性神经元数目及其相对表达量。结果 与对照组相比，DM + CCH 组大 Morris水迷宫实验第2 ~ 5 天逃避潜伏期延长［（54.60 ± 3.75）s vs（25.99 ± 4.10）s，P = 0.000；（45.39 ± 2.78）s vs（27.50 ±4.39）s，P = 0.003；（39.71 ± 3.47）s vs（20.34 ± 3.69）s，P = 0.001；（41.43 ± 4.48）s vs（11.35 ± 3.95）s，P =0.000］，第6 天目标象限游泳时间百分比降低［（22.38 ± 3.41）% vs（43.69 ± 3.22）%，P = 0.000］；海马BACE-1阳性神经元数目增加、相对表达量显著升高（0.23 ± 0.04 vs 0.06 ± 0.02，P = 0.005）。结论 2型糖尿病伴慢性脑低灌注可以加重大鼠空间学习记忆能力障碍，其机制可能与海马神经元BACE-1表达水平升高有关。

关键词: 糖尿病, 2 型, 认知障碍, 海马, 淀粉样前体蛋白分泌酶类, 荧光免疫测定, 免疫印迹法, 疾病模型, 动物