Data_Sheet_1_Obese mice induced by high-fat diet have differential expression of circular RNAs involved in endoplasmic reticulum stress and neuronal synaptic plasticity of hippocampus leading to obesity-associated cognitive impairment.docx

Obesity induced by a high-fat diet (HFD) is an important cause of impaired memory and cognitive function, but the underlying mechanisms are not clear. In the present study, we analyzed the levels of circRNAs in the hippocampus of C57BL/6J mice and evaluated the memory and cognition ability of C57BL/6J mice with HFD using Morris water maze and Y-maze approaches to explore the potential mechanisms linking circRNAs in obesity-associated cognitive impairment. Learning performance showed that HFD-induced obesity mice have impaired memory and cognition. The Arraystar analysis of the hippocampus displayed that HFD-induced obesity leads to the differential expression of circRNAs (DE-circRNAs) in mice. In total, 46 circular RNAs with elevated expression and 10 with decreased expression were identified. Among them, mmu_circRNA_004797 was identified to be significantly downregulated and the expression of mmu_circRNA_21040 was significantly upregulated in the HFD-fed mice, compared with control mice by PCR test. Bioinformatics analysis also showed that the upregulated circRNAs were related to the neuronal function and behavior, and material transport process, while downregulated circRNAs participated in the process of cell response to external stimuli, such as cellular response to nutrient levels. Furthermore, the KEGG pathway analysis showed that the upregulated circRNAs are mainly involved in Axon guidance, calcium signaling pathway, and ErbB signaling pathway. Only a single significant pathway, that is, “protein processing in endoplasmic reticulum”, was observed in the downregulated circRNAs. Finally, we examined the deficits of hippocampal synaptic plasticity and detected the expression of ER stress-related protein. The results showed that ER stress was activated in the hippocampus, and hippocampal synaptic plasticity deficits were displayed. Our results demonstrated that circRNAs were most likely implicated in the predisposition to obesity-associated cognitive impairment.

高脂饮食（high-fat diet, HFD）诱导的肥胖是引发记忆与认知功能受损的重要诱因，但其潜在分子机制尚未阐明。本研究中，我们对C57BL/6J小鼠海马组织中的环状RNA（circRNAs）表达水平进行了分析，并通过莫里斯水迷宫（Morris water maze）与Y型迷宫（Y-maze）实验评估了高脂饮食喂养的C57BL/6J小鼠的记忆与认知能力，以探索环状RNA与肥胖相关认知损伤之间的潜在关联机制。行为学实验结果显示，高脂饮食诱导的肥胖小鼠存在记忆与认知功能受损。Arraystar分析显示，高脂饮食诱导的肥胖会导致小鼠海马组织内差异表达环状RNA（differentially expressed circRNAs, DE-circRNAs）的产生。本研究共鉴定得到46个表达上调的环状RNA以及10个表达下调的环状RNA。经聚合酶链式反应（Polymerase Chain Reaction, PCR）检测发现，与对照组小鼠相比，高脂饮食喂养小鼠体内mmu_circRNA_004797显著下调，而mmu_circRNA_21040的表达则显著上调。生物信息学分析结果显示，表达上调的环状RNA主要参与神经元功能与行为、物质转运过程；而表达下调的环状RNA则参与细胞对外界刺激的响应过程，例如细胞对营养水平的应答反应。此外，京都基因与基因组百科全书（Kyoto Encyclopedia of Genes and Genomes, KEGG）通路分析显示，表达上调的环状RNA主要富集于轴突导向、钙信号通路以及ErbB信号通路；而表达下调的环状RNA仅富集到一条显著通路，即内质网内蛋白质加工通路。最后，我们检测了海马突触可塑性的损伤情况，并对内质网应激（endoplasmic reticulum, ER）相关蛋白的表达水平进行了测定。结果显示，小鼠海马组织中内质网应激被激活，同时出现海马突触可塑性损伤。本研究结果表明，环状RNA极有可能参与了肥胖相关认知损伤的发生发展过程。