慢性不可预知温和刺激小鼠内侧前额叶的能量代谢障碍及功能磁共振成像

Energy metabolism disorder and functional magnetic resonance imaging of the medial prefrontal cortex in mice with chronic unpredictable mild stress

目的研究慢性不可预知温和刺激(CUMS)小鼠活体状态下内侧前额叶灰质体积和自发活动的变化,及其与mTORC1能量信号通路的关联及机制。方法4周龄健康C57Bl/6小鼠随机分为正常对照组(n=16,未予处理)和抑郁模型组(n=16,CUMS方法造模8周)。旷场实验、强迫游泳实验、悬尾实验、糖水摄取实验检测小鼠抑郁倾向,利用结构功能磁共振探究小鼠脑灰质体积和低频振幅的改变。而后,将抑郁模型组的CUMS小鼠随机分成CUMS治疗组(n=8,氯胺酮活化mTORC1通路)和CUMS对照组(n=8,生理盐水)。取小鼠内侧前额叶组织,蛋白免疫印迹法检测并比较正常对照组、CUMS治疗组及CUMS对照组3组小鼠mTORC1相关蛋白的磷酸化水平,ELISA法检测ATP和NADP+/NADPH为代表的3组小鼠组织能量代谢情况。结果经过CUMS后小鼠出现明显抑郁行为倾向,CUMS小鼠的糖水偏爱百分比下降(P<0.05)、糖和水的总摄取量减低(P<0.01),旷场实验总运动距离(P<0.05)及中央区域运动距离(P<0.01)缩短,在悬尾实验和强迫游泳实验中CUMS小鼠不动时间增加(P>0.05),但不具有统计学意义。磁共振检测发现CUMS小鼠内侧前额叶灰质体积增大,mALFF显著增高(P<0.01,Alphasim矫正);mTORC1相关蛋白的磷酸化水平减低,ATP和NADP+/NADPH降低(P<0.05),经过氯胺酮治疗,mTORC1相关蛋白的磷酸化水平升高,ATP显著升高(P<0.05)。结论CUMS小鼠内侧前额叶存在更高的自发活动以及更低的产能效率,这种自发活动与产能效率的不匹配提示内侧前额叶存在mTORC1磷酸化减低相关的能量代谢方面的障碍,且此障碍可以通过氯胺酮活化mTORC1通路得到缓解。

Objective To analyze spontaneous activities and energy metabolism in the medial prefrontal cortex(mPFC)of mice with chronic unpredictable mild stress(CUMS)and explore the correlation of these changes with the mTORC1 signaling pathway.Methods Normal C57Bl/6 mice were randomly divided into control group(n=16)and depression model group(n=16),and the mice in the latter group were subjected to 8 weeks of modeling with CUMS.Behavioral tests including open field test,sucrose consumption test,tail suspension test and forced swimming test were performed,and the changes in prefrontal gray matter volume and the amplitude of low frequency fluctuation(ALFF)in the mice were detected with functional magnetic resonance imaging.The CUMS mice were then randomized into two groups for treatment with ketamine(n=8)or saline(n=8).The mPFC tissues of the mice were collected for detecting the phosphorylation levels of mTORC1-related proteins with Western blotting and ATP level and NADP+/NADPH ratio with ELISA in the 3 groups.Results Compared with the control mice,CUMS mice exhibited a distinct depressive phenotype with significantly decreased sucrose preference(P<0.05)and shortened total distances(P<0.01)and central exercise distances(P<0.05)in the open field test without obvious changes of immobile time in tail suspension test and forced swimming test(P>0.05).Prefrontal gray matter volume and mALFF increased(P<0.01),and the phosphorylation level of mTORC1-related proteins,ATP level and NADP+/NADPH ratio all decreased significantly(P<0.05)in CUMS mice.After ketamine treatment,the phosphorylation level of mTORC1-related proteins and ATP level increased significantly in CUMS mice(P<0.05),but the increase of NADP+/NADPH ratio was not statistically significant.Conclusion The mPFC of CUMS mice shows increased spontaneous activities but lowered productivity efficiency,indicating the presence of energy metabolism disorder in the mPFC,which is related with reduced mTORC1 phosphorylation and can be alleviated by activating the mTORC1 pathway with ketamine.