雄性小鼠慢性高脂饮食对子代行为的影响及遗传机制

The rate of overweight or obesity in adolescence is increasing gradually in our country in last twenty years. Obesity has persistent implication on parents and their children. It is reported that maternal high-fat diet during the perinatal period has an enduring impact on numerous aspects of offspring physiology and behavior, including a higher likelihood of developing mental health disorders, impairments in social behaviors, decreased cognitive abilities, enhanced response to stress, and altered reward-based behaviors. Until now the majority of examples of transgenerational environmental effects described have been maternal effects. However, maternal effects are difficult to separate from direct effects of in utero environmental exposure on offspring. It is therefore of great interest to determine what environmental conditions have transgenerational effects in mammals, and to characterize the mechanisms that mediate these effects. Our preliminary data show that the offspring of high-fat diet fathers are more anxious compared with offspring of control diet fathers, with the change of monoamine oxidase A (MAOA) in brain. Moreover, the neuronal specific PPARgamma knockout mice are more anxious compared with wild type mice. Based on our preliminary data, we are going to study the transgenerational effects of paternal high-fat diet on behavior and gene expression in offspring in mice. We will examine anxiety, depression and memory in the fathers with high fat diet and their offspring. Then we will screen genes in offspring mice that responded to paternal diet. Cytosine methylation will also be examined in fathers' sperm and offspring brain to determine the mechanisms that mediate these effects.

我国城镇肥胖人群呈逐渐上升趋势，母亲在围产期的肥胖影响子女的焦虑、抑郁等行为，母亲在围产期的生活环境对后代的影响，不能排除子宫内环境的直接影响；而父亲的营养状况对子女行为的影响目前尚无报道。最近发现，父亲的代谢状况可以影响子代的代谢，这种影响可能是通过表观遗传实现的。父亲的高脂饮食和肥胖是否影响子代的行为，机制是什么？我们在预实验中发现，高脂饮食雄性小鼠的后代表现出一定的焦虑样行为，脑内单胺氧化酶的量发生改变，神经元特异性PPARgamma敲除小鼠也表现出一定的焦虑样行为。本课题研究：高脂饮食和肥胖在雄性小鼠中对子代焦虑、抑郁、记忆等行为的影响及遗传机制。我们应用DNA甲基化芯片，结合染色质免疫沉淀、PCR等方法，检测与脂肪代谢相关的PPARgamma、神经递质代谢的MAOA等基因的DNA甲基化改变，应用相应的抑制剂、基因敲除和过表达等方法，阐明父亲代谢水平的变化对子代行为影响的机制。

我国肥胖人口呈逐渐上升趋势，代谢性疾病的发病年龄逐渐降低。最近研究发现，父亲的代谢状况可以影响子代的代谢：雄性高脂饮食小鼠，其子代雌性小鼠出现糖耐量异常，这种影响是通过表观遗传实现的。父亲的高脂饮食对其自身的焦虑、抑郁行为有何影响？对子代的行为有何影响？通过何种机制遗传给子代？在本课题中，我们选用8-10周雄性C57/BL 小鼠，给予高脂饮食4周或12周，或对照饲料。高脂饮食4周或12周，小鼠体重均增加明显，血糖升高。高脂4周小鼠表现出抗焦虑样行为，而高脂12周小鼠未表现出抗焦虑样行为。Western blot 检测不同脑区SIRT1的量，发现4周高脂小鼠mPFC区SIRT1显著下降，连续两周给予SIRT1激动剂可以取消高脂诱导的抗焦虑作用；12周高脂小鼠mPFC区和杏仁核SIRT1变化不显著，连续两周给予SIRT1抑制剂，无抗焦虑作用。我们的结果提示短期高脂饮食可以抗焦虑，而长期高脂饮食无抗焦虑作用。给予小鼠16周高脂饮食，小鼠表现出抑郁样行为。检测发现mPFC区PPARg下降明显，局部脑区给予PPARg激动剂或过表达PPARg可以取消高脂饮食导致的抑郁样行为。神经元特异性敲除PPARg小鼠表现出抑郁样行为，mPFC区过表达PPARg可以取消抑郁样行为。在慢性社交挫败模型中，敏感组小鼠mPFC区PPARg下降，给予PPARg激动剂或丙咪嗪可以取消抑郁样行为。我们的结果提示mPFC区PPARg降低，可能是高脂饮食诱导的抑郁样行为的机制；在伴有肥胖的抑郁病人中，可能可以用PPARg激动剂治疗抑郁。给予4周的雄性小鼠高脂饮食，8周后检测，发现小鼠出现抗焦虑。Western blot检测发现杏仁核MAOA减少。以上小鼠与雌性小鼠交配，产生子一代。子一代小鼠给予对照饲料，8-10周时检测，发现子代小鼠表现出抗焦虑。亲代小鼠精子MAOA组蛋白甲基化升高，子代小鼠海马区MAOA升高，杏仁核MAOA降低。小鼠腹腔注射MAOA抑制剂或者杏仁核注射MAOA shRNA，均产生抗焦虑作用。我们的结果提示青少年时期高脂饮食有抗焦虑作用，并且可以遗传给子代，这种遗传可能是通过MAOA组蛋白甲基化升高实现的。综上所述，我们的研究提示短期高脂饮食有抗焦虑作用，而长期高脂饮食没有抗焦虑作用，而表现出抑郁样行为。抑郁样行为与脑内PPARg降低有关，PPARg激动剂可能可以用于肥胖抑郁病人的治疗。