The imbalance of the gut microbiome or dysbiosis has been implicated as a cause of obesity [1] and brain disorders [2]. Eat well is one of the most effective tools to relief metabolic or brain disorders. However, this practice is difficult to be followed by health agents and patients. Transcranial direct current stimulation (tDCS) is a non-invasive neuromodulation method that has been widely investigated in recent years [3]. The method consists of applying a low intensity continuous electric current over the scalp. When applied for 20e30 minutes it is able to alter significantly the cortical excitability. For this reason, this method has been used in the treatment of food craving and overweight [4]. On the other hand, none of the studies evaluated the impact of tDCS on the gut microbiome. Considering the bidirectional mechanisms of the brain-gut axis, it is conceivable to think that tDCS could also induce a significant change in the composition of the gut microbiome and, therefore, induce therapeutic effects. A 38-year-old woman diagnosed with overweight and cravings for sugary foods ten years ago, according to the WHO specification, presented herself in October 2019 at the Neuromodulation Clinic in Porto Alegre-RS. According to her unsuccessful weight loss attempts history, a 10-week treatment of transcranial direct current stimulation (tDCS) was provided. Therefore, the patient filled out the free and informed consent form, agreeing with the use of the tDCS and microbiome analysis using the 16S molecular technique. The tDCS involved the application of weak direct electric current (2 mA) through two electrodes (5 5 cm) embedded in saline solution and placed on the scalp, with the anode on the right dorsolateral prefrontal cortex and the cathode on the contralateral supraorbital region, for 20 minutes a day, twice a week [5]. This montage was based on previous studies for the treatment of cravings by drugs and food [4]. Three stool samples were also collected by swab for intestinal microbiome analysis in the pre-intervention moments, after a session of tDCS (acute effect) and after 20 sessions of tDCS (chronic effect), through the sequencing of the human fecal 16S ribosomal RNA gene. No dietary intervention was performed during treatment. It was observed a decrease in the bacteroidetes/firmicutes ratio from 8.5 to 5.2 after a single session of tDCS and from 5.7 after 20 sessions, represent an improvement of 38.8% and 33% for acute and chronic effects respectively. The patient showed a quick and significant decrease in the firmicutes proportions which were most prevalent, with an increase in Roseburia intestinalis and Faecalibacterium prausnitzii, a gradual and sustained effect until the 10th week. There was also an increasing number in the bacteroidetes

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经颅直流电刺激对肠道微生物群的影响：病例报告

肠道微生物组的不平衡或生态失调被认为是导致肥胖 [1] 和脑部疾病 [2] 的原因。吃得好是缓解代谢或脑部疾病的最有效工具之一。然而，这种做法很难被健康代理人和患者所遵循。经颅直流电刺激（tDCS）是近年来得到广泛研究的一种非侵入性神经调节方法[3]。该方法包括在头皮上施加低强度的连续电流。当应用 20e30 分钟时，它能够显着改变皮质兴奋性。出于这个原因，这种方法已被用于治疗渴望食物和超重 [4]。另一方面，没有一项研究评估了 tDCS 对肠道微生物群的影响。考虑到脑 - 肠轴的双向机制，可以想象 tDCS 也可以诱导肠道微生物组的组成发生显着变化，从而产生治疗效果。根据世界卫生组织的规范，一名 38 岁的女性在十年前被诊断出超重并渴望吃含糖食物，她于 2019 年 10 月在阿雷格里港的神经调节诊所就诊。根据她不成功的减肥尝试史，提供了为期 10 周的经颅直流电刺激 (tDCS) 治疗。因此，患者填写了自由知情同意书，同意使用16S分子技术进行tDCS和微生物组分析。tDCS 涉及通过两个电极（5 5 厘米）嵌入盐水溶液并放置在头皮上，施加弱直流电流（2 mA），阳极位于右侧背外侧前额叶皮层，阴极位于对侧眶上区域，每天 20 分钟，每周两次 [5]。这个蒙太奇是基于以前关于药物和食物治疗渴望的研究 [4]。在干预前、tDCS（急性效应）和 20 次 tDCS（慢性效应）后，通过人类粪便 16S 核糖体 RNA 基因测序，还通过拭子采集了三个粪便样本用于肠道微生物组分析. 治疗期间未进行饮食干预。观察到在单次 tDCS 和从 5 之后，拟杆菌/厚壁菌的比率从 8.5 减少到 5.2。20 次治疗后 7 次，急性和慢性影响分别提高了 38.8% 和 33%。患者表现出最普遍的厚壁菌比例迅速而显着的下降，随着罗斯氏肠杆菌和普拉梭菌的增加，这种影响逐渐持续，直到第 10 周。拟杆菌的数量也在增加