Department of Biomedical Sciences and Engineering, National Central University, Taoyuan, Taiwan.
Taiwan International Graduate Program in Interdisciplinary Neuroscience, National Central University and Academia Sinica, Taipei, Taiwan.
Sci Rep. 2024 Apr 2;14(1):7774. doi: 10.1038/s41598-024-57649-z.
Human microbiota mainly resides on the skin and in the gut. Human gut microbiota can produce a variety of short chain fatty acids (SCFAs) that affect many physiological functions and most importantly modulate brain functions through the bidirectional gut-brain axis. Similarly, skin microorganisms also have identical metabolites of SCFAs reported to be involved in maintaining skin homeostasis. However, it remains unclear whether these SCFAs produced by skin bacteria can affect brain cognitive functions. In this study, we hypothesize that the brain's functional activities are associated with the skin bacterial population and examine the influence of local skin-bacterial growth on event-related potentials (ERPs) during an oddball task using EEG. Additionally, five machine learning (ML) methods were employed to discern the relationship between skin microbiota and cognitive functions. Twenty healthy subjects underwent three rounds of tests under different conditions-alcohol, glycerol, and water. Statistical tests confirmed a significant increase in bacterial population under water and glycerol conditions when compared to the alcohol condition. The metabolites of bacteria can turn phenol red from red-orange to yellow, confirming an increase in acidity. P3 amplitudes were significantly enhanced in response to only oddball stimulus at four channels (Fz, FCz, and Cz) and were observed after the removal of bacteria when compared with that under the water and glycerol manipulations. By using machine learning methods, we demonstrated that EEG features could be separated with a good accuracy (> 88%) after experimental manipulations. Our results suggest a relationship between skin microbiota and brain functions. We hope our findings motivate further study into the underlying mechanism. Ultimately, an understanding of the relationship between skin microbiota and brain functions can contribute to the treatment and intervention of diseases that link with this pathway.
人体微生物主要存在于皮肤和肠道中。人体肠道微生物可以产生多种短链脂肪酸（SCFAs），这些酸通过双向的肠脑轴影响许多生理功能，最重要的是调节大脑功能。同样，皮肤微生物也有相同的 SCFA 代谢物，据报道这些代谢物参与维持皮肤内稳态。然而，目前尚不清楚皮肤细菌产生的这些 SCFAs 是否会影响大脑认知功能。在这项研究中，我们假设大脑的功能活动与皮肤细菌种群有关，并使用 EEG 检查局部皮肤细菌生长对Oddball 任务中事件相关电位（ERP）的影响。此外，还采用了五种机器学习（ML）方法来辨别皮肤微生物群和认知功能之间的关系。二十名健康受试者在不同条件（酒精、甘油和水）下进行了三轮测试。统计检验证实，与酒精条件相比，水和甘油条件下细菌种群显著增加。细菌代谢物可使苯酚红从红橙色变为黄色，证实酸度增加。与水和甘油处理相比，只有在四个通道（Fz、FCz 和 Cz）的Oddball 刺激下，P3 振幅才会显著增强，并且在去除细菌后观察到。通过使用机器学习方法，我们证明了在实验操作后，EEG 特征可以以较高的准确率（>88%）进行分离。我们的结果表明皮肤微生物群和大脑功能之间存在关系。我们希望我们的发现能够激励对潜在机制的进一步研究。最终，了解皮肤微生物群和大脑功能之间的关系有助于治疗和干预与该途径相关的疾病。
