BACKGROUND There is growing evidence that the gut microbiota may play an important role in neurodegenerative diseases such as Alzheimer's disease. However, how these commensals influence disease risk and progression still has to be deciphered. OBJECTIVE The objective of this review was to summarize current knowledge on the interplay between gut microbiota and retinoic acid. The latter one represents one of the important micronutrients, which have been correlated to Alzheimer's disease and are used in initial therapeutic intervention studies. METHODS A selective overview of the literature is given with the focus on the function of retinoic acid in the healthy and diseased brain, its metabolism in the gut, and the potential influence that the bioactive ligand may have on microbiota, gut physiology and, Alzheimer's disease. RESULTS Retinoic acid can influence neuronal functionality by means of plasticity but also by neurogenesis and modulating proteostasis. Impaired retinoid-signaling, therefore, might contribute to the development of diseases in the brain. Despite its rather direct impact, retinoic acid also influences other organ systems such as gut by regulating the residing immune cells but also factors such as permeability or commensal microbiota. These in turn can also interfere with retinoid-metabolism and via the gutbrain- axis furthermore with Alzheimer's disease pathology within the brain. CONCLUSION Potentially, it is yet too early to conclude from the few reports on changed microbiota in Alzheimer's disease to a dysfunctional role in retinoid-signaling. However, there are several routes how microbial commensals might affect and might be affected by vitamin A and its derivatives.

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维甲酸和阿尔茨海默氏病中的肠道菌群：背对背抗争？

背景技术越来越多的证据表明，肠道菌群可能在神经退行性疾病如阿尔茨海默氏病中起重要作用。但是，这些建议如何影响疾病的风险和进展仍然有待研究。目的本综述的目的是总结当前关于肠道菌群和维甲酸之间相互作用的知识。后者代表一种重要的微量营养素，已与阿尔茨海默氏病相关，并已用于初始治疗干预研究中。方法对文献进行选择性综述，重点是视黄酸在健康和患病大脑中的功能，其在肠道中的代谢以及生物活性配体可能对微生物群，肠道生理以及阿尔茨海默氏病的潜在影响。结果维甲酸可通过可塑性影响神经元功能，还可通过神经发生和调节蛋白稳态来影响神经元功能。因此，类维生素A信号传导受损可能会导致脑部疾病的发展。尽管视黄酸具有相当直接的影响，但它还可以通过调节驻留的免疫细胞来影响其他器官系统，例如肠道，还可以调节通透性或共生微生物群等因素。这些反过来又会干扰类视色素的代谢，并通过肠脑轴进一步干扰大脑内的阿尔茨海默氏病病理。结论潜在地，从关于阿尔茨海默氏病的微生物群改变到类视色素信号转导功能失调的少数报道的结论尚为时过早。然而，