健康与遗传心理学研究室知识库

目的：创伤后应激障碍（Post Traumatic Stress Disorder, PTSD）是由异乎寻常的威胁性刺激或灾难导致延迟出现和长期持续的精神障碍。青少年经历创伤的风险远高于成人，早期创伤应激个体患上PTSD 的风险也更高。然而，青少年阶段神经行为的可塑性为PTSD提供了新的治疗思路，提示青少期可能是预防和治 疗PTSD的一个重要时间窗口。ω-3 多不饱和脂肪酸（Omega-3 polyunsaturated fatty acids, ω-3PUFAs）作为机体必不可少的大量营养素在一些神经系统疾病中发挥了保护作用，可能通过神经营养和抗炎等途径调节创伤相关的情绪障碍；故而，在青少期这一身心发育关键阶段补充ω-3PUFAs 可能为PTSD的预防和治疗 带来线索。目前，PTSD的生理机制尚不明确。PTSD 患者体内表现出异常的神经营养水平和过度的炎症反应，最新一些研究也发现了PTSD患者脂质代谢和肠道菌群异常。尽管并不清楚它们和PTSD相关细胞和分子机制之间的确切关系，鉴于目前治疗PTSD的药物疗效并不显著以及ω-3PUFAs在应激相关精神疾病中的改善作用，其仍然可为通过神经可塑性和免疫调节治疗PTSD带来启示。因此，本研究的目的是探究ω-3PUFAs对青少期PTSD样行为的改善作用及潜在的神经生理机制。

方法：本研究由五个子研究组成。研究一通过单次延长应激（single prolonged stress, SPS）这一经典PTSD模型对 Wistar 大鼠造模，通过条件性恐惧、糖水偏好、强迫游泳、旷场和高架十字迷宫实验检测造模之后大鼠的PTSD样行为，并借助质谱分析探讨创伤应激易感和韧性与ω-3PUFAs 的关系。研究二聚焦于青少期这一身心发育的关键时间窗，探究在青少期补充二十二碳六烯酸 （Docosahexaenoic acid, DHA）和二十碳五烯酸（Eicosapentaenoic acid, EPA）这 两种关键的ω-3PUFAs 对青少期创伤应激大鼠PTSD样行为的影响。研究三通过 脂质组学分析血清脂质的类型、分布和功能，探究青少期创伤应激大鼠PTSD样行为和血清脂质分子之间的关系。研究四利用 PCR 技术对16S rDNA基因序列进行测序，以获取摄入ω-3PUFAs 对青少期创伤应激大鼠肠道微生物的生态多样性信息，并对可能的作用机制进行功能预测。最后，基于研究三和研究四功能预测的结果，研究五检测ω-3PUFAs 对青少期创伤应激大鼠脑源性神经营养因子（brain-derived neurotrophic factor, BDNF）以及 PI3K/AKT 炎性信号通路的影响，探索ω-3PUFAs通过神经营养和神经免疫途径改善 SPS诱导的PTSD样症状的神经机制。

结果：（1）SPS可诱导成年大鼠产生PTSD样行为，主要表现为异常增强的恐惧记忆及一定程度的抑郁和焦虑样情绪，这种行为学上的改变伴随着外周血清中DHA的减少，创伤易感大鼠血清 DHA显著低于空白组和韧性组。（2）青少期大鼠在为期一天的急性SPS创伤应激后连续补充DHA和EPA 14天，其 PTSD 样行为得到显著改善。（3）青少期创伤应激大鼠血清中，包括甘油磷脂、鞘脂和甘油酯等在内的多个脂质成分浓度发生了异常变化；而补充 DHA和EPA均能有效降低异常增加的溶血磷脂酰丝氨酸（lysophosphatidylserine, LPS）这种 与神经炎症密切相关的脂质。（4）创伤应激诱导大鼠肠道 muri 菌、普雷沃氏-UCG-001 菌和拟杆菌相对丰度增多，毛螺旋菌、阿克曼菌和颤螺菌相对丰度减少；而补充 DHA 和 EPA 可以改善这些异常的菌群变化：补充DHA有效降低了异常升高的 muri 菌、普雷沃氏-UCG-001 菌和胃瘤球菌的相对丰度；补充EPA显著升高了异常降低的毛螺旋菌-UCG−005 和 NK4A136 菌的相对丰度。（5）补充 DHA 和 EPA能有效增加创伤应激诱导的前额叶内 BDNF 的异常减少，并显著 降低PI3K和AKT蛋白表达水平，促进神经营养水平恢复并改善过度的神经炎症。

结论：本研究发现在青少期补充两种关键的ω-3 多不饱和脂肪酸分子 DHA 和 EPA 可以通过调节脂质分子和肠道菌群，增加BDNF并调控 PI3K/AKT 炎性 信号通路，进而调节前额叶内的神经营养和神经炎症来改善 SPS 创伤应激模型 诱发的PTSD样症状。本研究为解释ω-3PUFAs 改善PTSD的神经生理机制提供了新的实验证据，并为预防和治疗早期创伤导致的青少年PTSD带来启示。

Objectives: Post Traumatic Stress Disorder (PTSD) is a mental disorder with delayed onset and long-term persistence caused by unusually threatening stimuli or disasters. Adolescents are at much higher risk of experiencing trauma than adults, and individuals with early traumatic stress are at higher risk of developing PTSD. However, adolescence neurobehavioral plasticity in the treatment of PTSD provides a new train of thought, suggesting teenage period may be an important time window for the prevention and treatment of PTSD. As an essential macronutrient, ω-3 polyunsaturated fatty acids (ω-3PUFAs) play a protective role in some nervous system diseases, and may regulate trauma-related emotional disorders through neurotrophic and anti-inflammatory pathways. Therefore, supplementation of ω-3PUFAs in adolescence, a critical period for physical and mental development, may provide clues for the prevention and treatment of PTSD. Currently, the physiological mechanism of PTSD is still unclear. PTSD patients have shown abnormal nerve nutrient levels and excessive inflammatory response, the latest studies also found abnormal lipid metabolism and intestinal flora in them. Although the exact relationship between ω-3PUFAs and the cellular and molecular mechanisms involved in PTSD is not clear, given the limited efficacy of current drugs for PTSD and the ameliorating effect of ω-3PUFAs on stress-related psychiatric disorders, ω-3PUFAs may still have implications for the treatment of PTSD through neuroplasticity and immune modulation. Therefore, the aim of this study is to investigate the effects of ω-3PUFAs on PTSD-like behaviors in adolescents and the underlying neurophysiological mechanisms.

Methods: This study consisted of five sub-studies. In Study 1, the classic PTSD model, single prolonged stress (SPS), was established in Wistar rats. The PTSD-like behaviors of the rats were evaluated by conditioned fear, sucrose preference, forced swimming, open field and elevated plus maze tests. Mass spectrometry was used to explore the relationship between traumatic stress susceptibility or resilience and ω-3PUFAs. Study 2 focused on adolescence, the critical time window for physical and mental development, to investigate the effects of adolescent supplementation of two key ω-3PUFAs, Docosahexaenoic acid (DHA) and Eicosapentaenoic acid (EPA), on PTSD-like behaviors in adolescent rats with traumatic stress. In Study 3, lipidomics was used to analyze the types, distribution, and functions of serum lipids to explore the relationship between PTSD-like behaviors and serum lipid molecules. In Study 4, 16S rDNA gene sequence was sequenced by PCR technology to obtain information on the ecological diversity of gut microbiota in adolescent traumatic stress rats after ω-3PUFAs ingestion, and to predict the possible mechanism. Finally, based on the functional prediction results of Study 3 and 4, study 5 examined the effects of ω-3PUFAs on brain-derived neurotrophic factor (BDNF) and PI3K/AKT inflammatory signaling pathway in adolescent traumatic stress rats, exploring the neural mechanism of ω-3PUFAs in improving PTSD-like symptoms induced by SPS through neurotrophic and neuroimmune pathways.

Results: (1) SPS induced PTSD-like behaviors in adult rats, which were characterized by abnormally enhanced fear memory and a certain degree of depression and anxiety-like emotions. These behavioral changes were accompanied by decrease of the DHA in serum, which is significantly lower than that in the control and resilient groups. (2) adding DHA and EPA for 14 days continuously after one-day acute traumatic stress, PTSD-like behavior is improved significantly in adolescent rats. (3) Multiple concentration of lipid composition including glycerol phospholipid, sheath fat and glycerideanomaly changes have taken place in the serum of traumatic stress adolescent rats; While adding DHA and EPA can effectively reduce the abnormal increase of lysophosphatidylserine (LPS), which is closely related to neuroinflammation. (4) Traumatic stress increased the relative abundance of Muribaculaceae, Prevotellaceae-UCG-001, and Bacteroides, and decreased the relative abundance of Spirillum, Akkermansia, Lachnospiraceae-NK4A136 and Fluorespirillum in the gut of rats. DHA supplementation significantly reduced the abnormally elevated relative abundance of Muribaculaceae, Prevotellaceae-UCG-001, and Ruminococcus. EPA supplementation significantly elevated the abnormally reduced relative abundance of Lachnospiraceae-UCG-005, and -NK4A136. (5) Supplementation of DHA and EPA could effectively increase the traumatic stress-induced abnormal reduction of BDNF in the prefrontal lobe, and significantly reduce the relative protein expression levels of PI3K and AKT, and promote the recovery of neurotrophic level and excessive neuroinflammation.

Conclusion: This study found that supplementation of two key ω-3 PUFAs,that is, DHA and EPA during adolescence could improve PTSD-like symptoms induced by SPS traumatic stress model by regulating lipid molecules and gut microbiota, increasing BDNF and regulating PI3K/AKT inflammatory signaling pathway, thereby regulating neuronutrition and neuroinflammation in the prefrontal lobe. This study provides new experimental evidence to explain the neurophysiological mechanism of ω-3 PUFAs in improving PTSD, and has implications for the prevention and treatment of adolescent PTSD caused by early trauma.