Objectives: To investigate the effects of environmental enrichment on cognitive behavior and the expression of adenosine triphosphate binding cassette transporter A7 (ABCA7) in hippocampus of the adolescent mice with high fat diet.
Methods: A total of healthy 3-week-old male C57BL/6J mice were randomly divided into 3 groups: a control (Con) group, a high fat diet (HFD) group, and a high fat diet+environmental enrichment (HFD+EE) group, with 10 mice in each group. The Con group was given normal diet. The HFD group was given high fat diet. The HFD+EE group was given high fat diet; at the same time, they treated by environmental enrichment. After 10 weeks, open field test was used to detect activity. Novel object recognition test and Y maze test were used to detect cognitive behavior. After the test, the brain was collected and used to detect the protein expression of ABCA7 in the hippocampus by immunohistochemistry and Western blotting. And quantitative RT-PCR (RT-qPCR) was used to detect the ABCA7 mRNA expression level in the hippocampus.
Results: There was no significant difference in the total movement distance in the mice among the 3 groups (P>0.05). In the novel object recognition test, the discrimination index of the HFD group was much lower than that of the Con group, and the difference was significant (P<0.01). The discrimination index of the HFD+EE group was higher than that of the HFD group, and the difference was significant (P<0.01). In the Y maze test, there was no significant difference in the percentage of time spent on the new arm among the mice in the 3 groups (P=0.1279). The percentage of entries in new arm in the HFD group was much lower than that in the Con group, and the difference was significant (P<0.01). The percentage of the entries in new arm in the HFD+EE group was significantly higher than that in the HFD group (P<0.05). The results of immunohistochemistry showed that ABCA7 was positively expressed in the cytoplasm of hippocampal neurons in the mice from these 3 groups, and the expression of ABCA7 in the hippocampus of the HFD group was lower than that of the Con group (CA1: P<0.01, CA3: P=0.06), while the expression of ABCA7 in hippocampus of HFD+EE group was higher than that of HFD group (CA1: P=0.23, CA3: P<0.05). Western blotting results showed that compared with the Con group, the protein level of ABCA7 in the hippocampus of the HFD group was significantly reduced (P<0.05), while compared with the Con group, the protein level of ABCA7 in the hippocampus of the HFD+EE group showed an upward trend (P=0.06). The results of RT-qPCR showed that the mRNA level of ABCA7 in the hippocampus of HFD group was significantly lower than that of the Con group (P<0.01), while the mRNA level of ABCA7 in the hippocampus of HFD+EE group was significantly higher than that of the HFD group (P<0.01).
Conclusions: High fat diet in adolescent can impair cognitive function with a decrease in the expression of ABCA7 in hippocampus, which can be ameliorate by environmental enrichment.
目的: 探究丰富环境对青春期高脂饮食小鼠认知行为和海马三磷酸腺苷结合盒转运子A7(adenosine triphosphate binding cassette transporter A7，ABCA7)表达的影响。方法: 健康SPF级3周龄C57BL/6J雄性小鼠30只，随机分为对照(Con)组、高脂饮食(HFD)组和高脂+丰富环境(HFD+EE)组，每组10只。Con组给予普通饲料，HFD组给予高脂饲料，HFD+EE组给予高脂饲料和丰富环境处理。10周后采用旷场实验检测小鼠活动度，新旧物体识别和Y迷宫检测小鼠认知行为。采用免疫组织化学法和蛋白质印迹法检测小鼠海马组织中ABCA7的蛋白质表达水平，采用定量RT-PCR(quantitative RT-PCR，RT-qPCR)检测小鼠海马组织中ABCA7的mRNA表达水平。结果: 3组小鼠总运动距离差异无统计学意义(P>0.05)。在新旧物体识别实验中，HFD组的辨别指数低于Con组，差异有统计学意义 (P<0.01)，HFD+EE组的辨别指数高于HFD组，差异有统计学意义(P<0.01)。在Y迷宫实验中，3组小鼠在Y迷宫中新异臂停留时间百分比差异无统计学意义(P=0.1279)。HFD组进出新异臂的次数百分比远低于Con组，差异具有统计学意义(P<0.01）。HFD+EE组小鼠进出新异臂的次数百分比较HFD组明显增加(P<0.05)。免疫组织化学结果显示：3组小鼠海马神经细胞胞质中可见ABCA7阳性表达，且HFD组海马组织中ABCA7的表达低于Con组(CA1：P<0.01，CA3：P=0.06)，而HFD+EE组海马组织中ABCA7的表达高于HFD组(CA1：P=0.23，CA3：P<0.05)。蛋白质印迹法结果显示：与Con组相比，HFD组小鼠海马组织中ABCA7蛋白质水平明显降低(P<0.05)，而HFD+EE组小鼠海马组织中ABCA7蛋白质水平与HFD组相比有升高趋势(P=0.06)。HFD组小鼠海马中ABCA7 mRNA水平与Con组相比明显降低(P<0.01)，而HFD+EE组小鼠海马中ABCA7 mRNA水平与HFD组相比明显升高，差异有统计学意义(P<0.01)。结论: 青春期高脂饮食能引起小鼠认知功能受损以及海马ABCA7表达下调，而丰富环境干预对这些具有改善作用。.
Keywords: adenosine triphosphate binding cassette transporter A7; adolescence; cognitive behavior; environmental enrichment; high fat diet.