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<front>
<journal-meta>
<journal-id journal-id-type="publisher-id">Front. Aging Neurosci.</journal-id>
<journal-title>Frontiers in Aging Neuroscience</journal-title>
<abbrev-journal-title abbrev-type="pubmed">Front. Aging Neurosci.</abbrev-journal-title>
<issn pub-type="epub">1663-4365</issn>
<publisher>
<publisher-name>Frontiers Media S.A.</publisher-name>
</publisher>
</journal-meta>
<article-meta>
<article-id pub-id-type="doi">10.3389/fnagi.2023.1116065</article-id>
<article-categories>
<subj-group subj-group-type="heading">
<subject>Neuroscience</subject>
<subj-group>
<subject>Original Research</subject>
</subj-group>
</subj-group>
</article-categories>
<title-group>
<article-title>Predictive microbial feature analysis in patients with depression after acute ischemic stroke</article-title>
</title-group>
<contrib-group>
<contrib contrib-type="author">
<name><surname>Yao</surname> <given-names>Shanshan</given-names></name>
<xref ref-type="aff" rid="aff1"><sup>1</sup></xref>
<xref ref-type="author-notes" rid="fn002"><sup>&#x2020;</sup></xref>
<uri xlink:href="http://loop.frontiersin.org/people/2099958/overview"/>
</contrib>
<contrib contrib-type="author">
<name><surname>Xie</surname> <given-names>Huijia</given-names></name>
<xref ref-type="aff" rid="aff1"><sup>1</sup></xref>
<xref ref-type="author-notes" rid="fn002"><sup>&#x2020;</sup></xref>
<uri xlink:href="http://loop.frontiersin.org/people/2099248/overview"/>
</contrib>
<contrib contrib-type="author">
<name><surname>Wang</surname> <given-names>Ya</given-names></name>
<xref ref-type="aff" rid="aff1"><sup>1</sup></xref>
<xref ref-type="author-notes" rid="fn002"><sup>&#x2020;</sup></xref>
</contrib>
<contrib contrib-type="author">
<name><surname>Shen</surname> <given-names>Nan</given-names></name>
<xref ref-type="aff" rid="aff1"><sup>1</sup></xref>
<xref ref-type="author-notes" rid="fn002"><sup>&#x2020;</sup></xref>
<uri xlink:href="http://loop.frontiersin.org/people/2241147/overview"/>
</contrib>
<contrib contrib-type="author">
<name><surname>Chen</surname> <given-names>Qionglei</given-names></name>
<xref ref-type="aff" rid="aff1"><sup>1</sup></xref>
<uri xlink:href="http://loop.frontiersin.org/people/2241143/overview"/>
</contrib>
<contrib contrib-type="author">
<name><surname>Zhao</surname> <given-names>Yiting</given-names></name>
<xref ref-type="aff" rid="aff1"><sup>1</sup></xref>
<uri xlink:href="http://loop.frontiersin.org/people/2241756/overview"/>
</contrib>
<contrib contrib-type="author">
<name><surname>Gu</surname> <given-names>Qilu</given-names></name>
<xref ref-type="aff" rid="aff1"><sup>1</sup></xref>
</contrib>
<contrib contrib-type="author">
<name><surname>Zhang</surname> <given-names>Junmei</given-names></name>
<xref ref-type="aff" rid="aff1"><sup>1</sup></xref>
<uri xlink:href="http://loop.frontiersin.org/people/2100775/overview"/>
</contrib>
<contrib contrib-type="author" corresp="yes">
<name><surname>Liu</surname> <given-names>Jiaming</given-names></name>
<xref ref-type="aff" rid="aff2"><sup>2</sup></xref>
<xref ref-type="corresp" rid="c001"><sup>&#x002A;</sup></xref>
<uri xlink:href="http://loop.frontiersin.org/people/414582/overview"/>
</contrib>
<contrib contrib-type="author" corresp="yes">
<name><surname>Sun</surname> <given-names>Jing</given-names></name>
<xref ref-type="aff" rid="aff1"><sup>1</sup></xref>
<xref ref-type="corresp" rid="c002"><sup>&#x002A;</sup></xref>
<uri xlink:href="http://loop.frontiersin.org/people/845618/overview"/>
</contrib>
<contrib contrib-type="author" corresp="yes">
<name><surname>Tong</surname> <given-names>Qiuling</given-names></name>
<xref ref-type="aff" rid="aff3"><sup>3</sup></xref>
<xref ref-type="corresp" rid="c003"><sup>&#x002A;</sup></xref>
</contrib>
</contrib-group>
<aff id="aff1"><sup>1</sup><institution>Department of Geriatrics, The Second Affiliated Hospital of Wenzhou Medical University</institution>, <addr-line>Wenzhou, Zhejiang</addr-line>, <country>China</country></aff>
<aff id="aff2"><sup>2</sup><institution>Department of Preventive Medicine, School of Public Health and Management, Wenzhou Medical University</institution>, <addr-line>Wenzhou, Zhejiang</addr-line>, <country>China</country></aff>
<aff id="aff3"><sup>3</sup><institution>Department of Neurology, The First Affiliated Hospital of Wenzhou Medical University</institution>, <addr-line>Wenzhou, Zhejiang</addr-line>, <country>China</country></aff>
<author-notes>
<fn fn-type="edited-by"><p>Edited by: Touqeer Ahmed, Johns Hopkins Medicine, Johns Hopkins University, United States</p></fn>
<fn fn-type="edited-by"><p>Reviewed by: Jun-Jie Zhang, Indiana University Bloomington, United States; Huidi Wang, Southern Medical University, China</p></fn>
<corresp id="c001">&#x002A;Correspondence: Jiaming Liu, <email>wzjiaming_liu@163.com</email></corresp>
<corresp id="c002">Jing Sun, <email>sunjwz@126.com</email></corresp>
<corresp id="c003">Qiuling Tong, <email>tongqiuling2013@126.com</email></corresp>
<fn fn-type="equal" id="fn002"><p><sup>&#x2020;</sup>These authors have contributed equally to this work</p></fn>
<fn fn-type="other" id="fn004"><p>This article was submitted to Neurocognitive Aging and Behavior, a section of the journal Frontiers in Aging Neuroscience</p></fn>
</author-notes>
<pub-date pub-type="epub">
<day>23</day>
<month>03</month>
<year>2023</year>
</pub-date>
<pub-date pub-type="collection">
<year>2023</year>
</pub-date>
<volume>15</volume>
<elocation-id>1116065</elocation-id>
<history>
<date date-type="received">
<day>05</day>
<month>12</month>
<year>2022</year>
</date>
<date date-type="accepted">
<day>06</day>
<month>03</month>
<year>2023</year>
</date>
</history>
<permissions>
<copyright-statement>Copyright &#x00A9; 2023 Yao, Xie, Wang, Shen, Chen, Zhao, Gu, Zhang, Liu, Sun and Tong.</copyright-statement>
<copyright-year>2023</copyright-year>
<copyright-holder>Yao, Xie, Wang, Shen, Chen, Zhao, Gu, Zhang, Liu, Sun and Tong</copyright-holder>
<license xlink:href="http://creativecommons.org/licenses/by/4.0/"><p>This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.</p></license>
</permissions>
<abstract>
<sec>
<title>Introduction</title>
<p>Post-stroke depression (PSD) is the most common emotional problem following a stroke, which requires early diagnosis to improve the prognosis. Gut microbiota plays important role in the pathological mechanisms of acute ischemic stroke and influences the outcome of patients. However, the relationship between PSD and gut microbiota remains unknown. Here, we explored whether the microbial signatures of gut microbiota in the patients with stroke could be an appropriate predictor of PSD.</p>
</sec>
<sec>
<title>Methods</title>
<p>Fecal samples were collected from 232 acute ischemic stroke patients and determined by 16s rRNA sequencing. All patients then received 17-Hamilton Depression Rating Scale (HAMD-17) assessment 3 months after discharge, and were further divided into PSD group and non-PSD group. We analyzed the differences of gut microbiota between these groups. To identify gut microbial biomarkers, we then established microbial biomarker model.</p>
</sec>
<sec>
<title>Results</title>
<p>Our results showed that the composition of gut microbiota in the PSD patients differed significantly from that in non-PSD patients. The genus <italic>Streptococcus</italic>, <italic>Akkermansia</italic>, and <italic>Barnesiella</italic> were significantly increased in PSD patients compared to non-PSD, while the genus <italic>Escherichia-Shigella, Butyricicoccus</italic>, and <italic>Holdemanella</italic> were significantly decreased. Correlation analyses displayed that <italic>Akkermansia, Barnesiella</italic>, and <italic>Pyramidobacter</italic> were positively correlated with HAMD score, while <italic>Holdemanella</italic> was negatively correlated with HAMD score. The optimal microbial markers were determined, and the combination achieved an area under the curve (AUC) value of 0.705 to distinguish PSD from non-PSD.</p>
</sec>
<sec>
<title>Conclusions</title>
<p>Our findings suggest that PSD patients had distinct gut microbiota compared to non-PSD patients, and explore the potential of microbial markers, which might provide clinical decision-making in PSD.</p>
</sec>
</abstract>
<kwd-group>
<kwd>16s rRNA</kwd>
<kwd>stroke</kwd>
<kwd>gut microbiota</kwd>
<kwd>depression</kwd>
<kwd>microbial signatures</kwd>
</kwd-group>
<counts>
<fig-count count="7"/>
<table-count count="1"/>
<equation-count count="0"/>
<ref-count count="46"/>
<page-count count="11"/>
<word-count count="6047"/>
</counts>
</article-meta>
</front>
<body>
<sec id="S1" sec-type="intro">
<title>1. Introduction</title>
<p>Post-stroke depression (PSD) is the most common emotional disorder after stroke (<xref ref-type="bibr" rid="B19">GBD 2015 Neurological Disorders Collaborator Group, 2017</xref>), which can increase the risk of mortality and stroke recurrence (<xref ref-type="bibr" rid="B20">Hackett et al., 2014</xref>; <xref ref-type="bibr" rid="B9">Cai et al., 2019</xref>). About 31% of acute ischemic stroke (AIS) patients may suffer from PSD within 5 years after stroke (<xref ref-type="bibr" rid="B21">Hackett and Pickles, 2014</xref>). A meta-analysis showed that delayed diagnosis and treatment of PSD may lead to stroke recurrence and suicide (<xref ref-type="bibr" rid="B9">Cai et al., 2019</xref>). Early recognition of patients who were prone to develop PSD was crucial, especially at clinical admission. Close monitoring and early intervention may prevent the adverse outcome (<xref ref-type="bibr" rid="B35">Maaijwee et al., 2016</xref>; <xref ref-type="bibr" rid="B4">Baccaro et al., 2019</xref>; <xref ref-type="bibr" rid="B17">Fantu et al., 2022</xref>; <xref ref-type="bibr" rid="B27">Ladwig et al., 2022</xref>). A series of studies evaluated the prediction potential of a variety of scoring systems for PSD, but none were robust enough. Thus, more efficient methods for prediction of PSD were needed.</p>
<p>Risk factors of PSD were multifactorial and complex, including the severity and location of the stroke, social support and personal factors such as gender, age and medical history (<xref ref-type="bibr" rid="B16">Elias et al., 2022</xref>; <xref ref-type="bibr" rid="B29">Li et al., 2022</xref>; <xref ref-type="bibr" rid="B45">Zhang et al., 2023</xref>). Recently, numerous studies revealed the potential association between changes in gut microbiota and prognosis after acute ischemic stroke (<xref ref-type="bibr" rid="B42">Tian et al., 2022</xref>; <xref ref-type="bibr" rid="B43">Wang et al., 2022</xref>). Previous studies showed that oral administration of antibiotics could reduce neurological impairment and the cerebral infarct volume, relieve cerebral edemas by altering the gut microbiota, while probiotic administration could ameliorate patients&#x2019; mood though the regulation of gut microbiota (<xref ref-type="bibr" rid="B11">Chen et al., 2019</xref>; <xref ref-type="bibr" rid="B34">Liu et al., 2020</xref>). Meanwhile, changes of gut microbiota could also be considered as a prognostic factor in acute ischemic stroke (<xref ref-type="bibr" rid="B6">Benakis and Liesz, 2022</xref>; <xref ref-type="bibr" rid="B42">Tian et al., 2022</xref>). In recent years, microbial marker severs as a non-invasive diagnosis tool for some diseases (<xref ref-type="bibr" rid="B3">Arnoldussen et al., 2017</xref>). Gut microbial marker had the potential to predict the development of AIS, and they may be an effective target tool to influence clinical outcome of AIS. Our previous study showed that the microbiota composition of patients with post stroke cognitive impairment (PSCI) was different from that of non-PSCI patients, characterized by an increase in the abundance of <italic>Proteobacteria</italic> (<xref ref-type="bibr" rid="B30">Ling et al., 2020a</xref>). Moreover, we also revealed that patients with post-stroke comorbid cognitive impairment and depression (PSCCID) had lower abundance of short-chain fatty acids (SCFAs) producing bacteria compared with non-PSCCID patients, and revealed that the abundance of Gammaproteobacteria and Enterobacteriaceae was negatively correlated with MoCA score (<xref ref-type="bibr" rid="B31">Ling et al., 2020b</xref>). These studies inspired the potential role of the microbiota in PSD progression. There was a correlation between gut microbiota and some complications of acute ischemic stroke, but the link between gut microbiota and PSD has not been well described.</p>
<p>To determine the prediction potential of gut microbiota for PSD outcome on admission, we performed a prospective study. In this study, we compared the difference between the gut microbiota of PSD patients and non-PSD patients, and further explored the &#x201C;key microbial signatures&#x201D; of gut microbiota of PSD patients, and searched for possible marker for the diagnosis of PSD patients. Further, through in-depth study on the relationship between the characteristics of gut microbiota and their clinical efficacy, we try to find potential biomarkers for clinical diagnosis, providing a new direction for the screening PSD patients on admission.</p>
</sec>
<sec id="S2" sec-type="materials|methods">
<title>2. Materials and methods</title>
<sec id="S2.SS1">
<title>2.1. Patients and sample collection</title>
<p>We enrolled 588 AIS patients at Second Affiliated Hospital of Wenzhou Medical University from September 2020 to July 2021. These patients came from Zhejiang Province with a long-term settlement. Patients with AIS diagnosed according to American Heart Association/American Stroke Association were included (<xref ref-type="bibr" rid="B39">Sacco et al., 2013</xref>). The inclusion criteria for this study were: ischemic stroke patients within 3 days after onset, aged 40&#x2013;95 years, without special diets, such as vegetarianism, no communication deficit (e.g., aphasia and deafness). Patients following conditions were excluded: transient ischemic attack or lacunar infarction; depression, anxiety or other mental illnesses diagnosed or psycho-emotional drug used before the onset of stroke; accompanied with severe systemic diseases (renal failure, respiratory failure, and circulatory failure); medical histories of other central nervous system diseases; failure to complete psychological assessment; use antidepressants, antibiotics or probiotics within 3 months. Eighty-one AIS patients were excluded according to the exclusion criteria, 116 AIS patients failed to collect stool samples, 159 AIS patients lost follow-up, 232 AIS patients that could be analyzed (<xref ref-type="supplementary-material" rid="FS1">Supplementary Figure 1</xref>). The protocol was approved by the Medical Ethics Committee of the Second Affiliated Hospital of Wenzhou Medical University. All clinical features were recorded according to standard procedures. The peripheral venous blood of the participants was measured at admission. We collected stool samples from each AIS patients at admission.</p>
</sec>
<sec id="S2.SS2">
<title>2.2. Demographic and clinical data</title>
<p>Demographic and clinical baseline data were collected, such as age, gender, marital status, education level, smoking and alcohol drinking, past disease history, education level, NIHSS scale, MMSE scale, baseline Barthel Index (BI), baseline blood pressure, baseline blood glucose and lipid levels, other lab results, imaging data, severity stratification, complications, and outcomes. The National Institute of Health Stroke Scale (NIHSS) was used to evaluate the degree of neurological impairment. The cognitive level was assessed by Minimum Mental State Examination (MMSE). PSD was diagnosed with a HAMD score &#x2265;8 according to 17-item Hamilton Depression Scale (HAMD-17) for 3 months after AIS onset (<xref ref-type="bibr" rid="B46">Zimmerman et al., 2013</xref>).</p>
</sec>
<sec id="S2.SS3">
<title>2.3. Fecal sample collection and analysis</title>
<p>All patients provided fresh stool within 1 week of admission. Fecal samples were collected and immediately transferred to the laboratory. The 200 mg feces samples were placed into a 2 ml sterile centrifuge tube and labeled. All specimens were stored at &#x2212;80&#x00B0;C within 30 min of preparation. DNA of fecal samples was extracted by DNA Kit (Omega Bio-tek, Norcross, GA, USA.) according to the manufacturer. The DNA concentration and purity were determined using NanoDrop 2000 UV-vis spectrophotometer (Thermo Scientific, Wilmington, DE, USA), and quantified by 1% agarose gel. After DNA extraction, the V3-V4 16S ribosomal RNA gene region was amplified with forward primer (5&#x2032;-ACTCCTACGGGAGGCAGCAG-3&#x2032;) and the reverse primer (5&#x2032;-GGACTACHVGGGTWTCTAAT-3&#x2032;). Sequencing was performed on the Illumina MiSeq platform (Illumina, San Diego, CA, USA). Raw fastq files were quality-filtered by Trimmomatic and merged by FLASH.</p>
<p>Chao1 and Shannon indexes were applied to analyze the alpha diversity of gut microbiota. A Wilcoxon rank sum test was performed to compare the alpha diversity of groups. Use the rarefaction curves to assess differences in richness between the two groups. The linear discriminant analysis (LDA) effect size (LEfSe) was performed using the Kruskal&#x2013;Wallis test with LDA score of &#x003E;2 used as thresholds. Differences in microbiota composition between groups were analyzed using Wilcoxon rank sum test. The Spearman correlation coefficients were calculated and visualized by heatmap. To determine the correlation between the microbial communities in the PSD and Non-PSD group, we constructed correlation network diagram inferred from the abundance of ASV with the threshold of 0.6. Spearman correlation was applied to determine the positive or negative relationship between the ASVs. Nodes were colored by phylum and size was related to the abundance of taxa. ROC curves and the AUC were used to confirm the specificity and sensitivity of the characteristic gut microbiota to the diagnosis of PSD.</p>
</sec>
<sec id="S2.SS4">
<title>2.4. Statistical analysis</title>
<p>Data were analyzed by SPSS 22.0 software. Categorical variables were presented as numbers with percentages, and continuous variables were shown as means with standard deviation (SD), or medians with interquartile range (IQR) according to the Kolmogorov-Smirnov normality test. Mann&#x2013;Whitney U-test was used for continuous variables and the Chi-squared test was used for categorical variables. All variables showing a trend in association in univariate analysis (<italic>P</italic> &#x003C; 0.10) were included in the multivariable model. The relative risk was expressed as the odds ratio (OR) with a 95% confidence interval (CI). <italic>P</italic> values &#x003C; 0.05 was considered significant.</p>
</sec>
</sec>
<sec id="S3" sec-type="results">
<title>3. Results</title>
<sec id="S3.SS1">
<title>3.1. Clinical characteristics of enrolled patients</title>
<p>There were 88 patients diagnosed with PSD (37.93%) after 3-month follow-up. The baseline characteristics of the patients in the two groups are shown in <xref ref-type="table" rid="T1">Table 1</xref>. In the PSD group, the mean age was 65.43 years old, 46.6% were female, and median education level 2 (2&#x2013;2). The mean age was 64.57 years old in the non-PSD group, with 29.9% being female and with 2 (2&#x2013;3) being education level. Univariate analysis showed that the differences between the two groups were gender, education level, diabetes mellitus, alcohol drinking, Barthel Index, FT3, baseline NHISS scores, baseline MMSE scores, and baseline PSQI scores (all <italic>P</italic> &#x003C; 0.05). Multivariable logistic regression showed that lower MMSE score was an independent risk factors for PSD (<italic>P</italic> = 0.040, OR 0.840, 95% CI 0.711&#x2013;0.992).</p>
<table-wrap position="float" id="T1">
<label>TABLE 1</label>
<caption><p>Demographic and clinical characteristics of two groups.</p></caption>
<table cellspacing="5" cellpadding="5" frame="box" rules="all">
<thead>
<tr>
<td valign="top" align="left" style="color:#ffffff;background-color: #7f8080;">Variables</td>
<td valign="top" align="center" style="color:#ffffff;background-color: #7f8080;">PSD (<italic>n</italic> = 88)</td>
<td valign="top" align="center" style="color:#ffffff;background-color: #7f8080;">Non-PSD (<italic>n</italic> = 144)</td>
<td valign="top" align="center" style="color:#ffffff;background-color: #7f8080;"><italic>P</italic>-value</td>
</tr>
</thead>
<tbody>
<tr>
<td valign="top" align="left" colspan="4" style="background-color: #dcdcdc;"><bold>Demographic parameters</bold></td>
</tr>
<tr>
<td valign="top" align="left">Age (years), mean (SD)</td>
<td valign="top" align="center">65.43 &#x00B1; 11.52</td>
<td valign="top" align="center">64.57 &#x00B1; 11.81</td>
<td valign="top" align="center">0.056</td>
</tr>
<tr>
<td valign="top" align="left">Female, <italic>n</italic> (%)</td>
<td valign="top" align="center">41 (46.6)</td>
<td valign="top" align="center">43 (29.9)</td>
<td valign="top" align="center">0.010</td>
</tr>
<tr>
<td valign="top" align="left">Education level, median (IQR)</td>
<td valign="top" align="center">2 (2&#x2013;2)</td>
<td valign="top" align="center">2 (2&#x2013;3)</td>
<td valign="top" align="center">0.012</td>
</tr>
<tr>
<td valign="top" align="left">Marriage, <italic>n</italic> (%)</td>
<td valign="top" align="center">74 (84.1)</td>
<td valign="top" align="center">131 (91.0)</td>
<td valign="top" align="center">0.113</td>
</tr>
<tr>
<td valign="top" align="left" colspan="4" style="background-color: #dcdcdc;"><bold>Vascular risk factors</bold></td>
</tr>
<tr>
<td valign="top" align="left">Hypertension, <italic>n</italic> (%)</td>
<td valign="top" align="center">67 (78.4)</td>
<td valign="top" align="center">107 (74.3)</td>
<td valign="top" align="center">0.755</td>
</tr>
<tr>
<td valign="top" align="left">Diabetes mellitus, <italic>n</italic> (%)</td>
<td valign="top" align="center">40 (45.5)</td>
<td valign="top" align="center">46 (31.9)</td>
<td valign="top" align="center">0.039</td>
</tr>
<tr>
<td valign="top" align="left">Hyperlipidemia, <italic>n</italic> (%)</td>
<td valign="top" align="center">52 (59.1)</td>
<td valign="top" align="center">88 (61.1)</td>
<td valign="top" align="center">0.294</td>
</tr>
<tr>
<td valign="top" align="left">History of CVD, <italic>n</italic> (%)</td>
<td valign="top" align="center">17 (19.3)</td>
<td valign="top" align="center">24 (16.7)</td>
<td valign="top" align="center">0.607</td>
</tr>
<tr>
<td valign="top" align="left">Smoking, <italic>n</italic> (%)</td>
<td valign="top" align="center">26 (29.5)</td>
<td valign="top" align="center">55 (40.5)</td>
<td valign="top" align="center">0.180</td>
</tr>
<tr>
<td valign="top" align="left">Alcohol drinking, <italic>n</italic> (%)</td>
<td valign="top" align="center">18 (20.5)</td>
<td valign="top" align="center">54 (37.5)</td>
<td valign="top" align="center">0.006</td>
</tr>
<tr>
<td valign="top" align="left">SBP (mmHg), mean (SD)</td>
<td valign="top" align="center">153.77 &#x00B1; 23.95</td>
<td valign="top" align="center">154.07 &#x00B1; 19.53</td>
<td valign="top" align="center">0.963</td>
</tr>
<tr>
<td valign="top" align="left">DBP (mmHg), median (IQR)</td>
<td valign="top" align="center">85 (76&#x2013;99)</td>
<td valign="top" align="center">89 (76&#x2013;96.25)</td>
<td valign="top" align="center">0.061</td>
</tr>
<tr>
<td valign="top" align="left" colspan="4" style="background-color: #dcdcdc;"><bold>Clinical characteristics</bold></td>
</tr>
<tr>
<td valign="top" align="left">Right side lesion location, <italic>n</italic> (%)</td>
<td valign="top" align="center">46 (52.3)</td>
<td valign="top" align="center">69 (47.9)</td>
<td valign="top" align="center">0.520</td>
</tr>
<tr>
<td valign="top" align="left">BI at discharge, median (IQR)</td>
<td valign="top" align="center">75 (60&#x2013;95)</td>
<td valign="top" align="center">95 (65&#x2013;100)</td>
<td valign="top" align="center">0.001</td>
</tr>
<tr>
<td valign="top" align="left">NIHSS, median (IQR)</td>
<td valign="top" align="center">2 (1&#x2013;3)</td>
<td valign="top" align="center">2 (1&#x2013;4)</td>
<td valign="top" align="center">0.015</td>
</tr>
<tr>
<td valign="top" align="left">MMSE, median (IQR)</td>
<td valign="top" align="center">24 (20&#x2013;26)</td>
<td valign="top" align="center">25 (22&#x2013;27.25)</td>
<td valign="top" align="center">0.005</td>
</tr>
<tr>
<td valign="top" align="left" colspan="4" style="background-color: #dcdcdc;"><bold>Laboratory index</bold></td>
</tr>
<tr>
<td valign="top" align="left">Hs-CRP (mg/L), median (IQR)</td>
<td valign="top" align="center">1.54 (0.60&#x2013;3.46)</td>
<td valign="top" align="center">1.21 (0.71&#x2013;2.86)</td>
<td valign="top" align="center">0.517</td>
</tr>
<tr>
<td valign="top" align="left">Folic acid (ng/ml), median (IQR)</td>
<td valign="top" align="center">8.79 (7.21&#x2013;12.49)</td>
<td valign="top" align="center">9.41 (7.21&#x2013;11.91)</td>
<td valign="top" align="center">0.798</td>
</tr>
<tr>
<td valign="top" align="left">Vitamin B12 (pg/ml), median (IQR)</td>
<td valign="top" align="center">315 (237&#x2013;601)</td>
<td valign="top" align="center">321 (123.25&#x2013;408.75)</td>
<td valign="top" align="center">0.253</td>
</tr>
<tr>
<td valign="top" align="left">Uric acid (&#x03BC;mol/L), median (IQR)</td>
<td valign="top" align="center">300 (241.5&#x2013;337.5)</td>
<td valign="top" align="center">317 (256.75&#x2013;374.5)</td>
<td valign="top" align="center">0.065</td>
</tr>
<tr>
<td valign="top" align="left">TSH (&#x03BC;IU/ml), median (IQR)</td>
<td valign="top" align="center">2.18 (1.39&#x2013;3.12)</td>
<td valign="top" align="center">1.77 (1.18&#x2013;2.73)</td>
<td valign="top" align="center">0.744</td>
</tr>
<tr>
<td valign="top" align="left">FT3 (pmol/ml), median (IQR)</td>
<td valign="top" align="center">2.96 &#x00B1; 0.39</td>
<td valign="top" align="center">3.05 &#x00B1; 0.37</td>
<td valign="top" align="center">0.029</td>
</tr>
<tr>
<td valign="top" align="left">FT4 (pmol/L), mean (SD)</td>
<td valign="top" align="center">1.20 &#x00B1; 0.17</td>
<td valign="top" align="center">1.17 &#x00B1; 0.16</td>
<td valign="top" align="center">0.260</td>
</tr>
</tbody>
</table>
<table-wrap-foot>
<fn><p>CVD, cerebrovascular disease; HAMD, Hamilton Depression Scale; IQR, interquartile range; MMSE, Mini-mental State Examination; BI, Barthel Index; NIHSS, National Institute of Health Stroke Scale; PSD, post-stroke depression; PSQI, Pittsburgh Sleep Quality Index; SD, standard deviation.</p></fn>
</table-wrap-foot>
</table-wrap>
</sec>
<sec id="S3.SS2">
<title>3.2. Diversity and distribution of gut microbiota in PSD and non-PSD groups</title>
<p>The alpha diversity of the bacterial community was assessed by Shannon and Chao1 indexes. There was no significant difference between PSD and non-PSD groups (<italic>P</italic> = 0.9029, 0.3832), indicating similarity in community richness and diversity between PSD and non-PSD patients (<xref ref-type="fig" rid="F1">Figures 1A, B</xref>). The rarefaction curves (<xref ref-type="fig" rid="F1">Figure 1C</xref>) showed that the richness of PSD group tended to be higher than that of the non-PSD group. The Venn diagram (<xref ref-type="fig" rid="F1">Figure 1D</xref>) showed the common and unique ASVs detected in PSD and non-PSD groups. The number of shared ASVs was 1,839. The number of unique ASVs in PSD group was 1,300, while that in PSND group was 2,445. As shown in <xref ref-type="supplementary-material" rid="FS2">Supplementary Figure 2</xref>, the gut microbiota beta-diversity between PSD and non-PSD groups was different.</p>
<fig id="F1" position="float">
<label>FIGURE 1</label>
<caption><p>Distribution of gut microbiota in PSD and non-PSD groups. <bold>(A)</bold> Chao1 indexes of gut microbiota &#x03B1; diversity in PSD and non-PSD groups. <bold>(B)</bold> Shannon indexes of gut microbiota &#x03B1; diversity in PSD and non-PSD groups. <bold>(C)</bold> A refraction curve demonstrating richness. <bold>(D)</bold> Venn diagram of gene numbers in PSD and non-PSD groups.</p></caption>
<graphic mimetype="image" mime-subtype="tiff" xlink:href="fnagi-15-1116065-g001.tif"/>
</fig>
<p>Taxonomic profiles at different levels of two groups were presented in <xref ref-type="fig" rid="F2">Figure 2</xref>. phylum Firmicutes, Bacteroidota, Proteobacteria, and Actinobacteria were the predominant in two groups (<xref ref-type="fig" rid="F2">Figure 2A</xref>). Taxonomic classification at the family level showed that most of the intestinal bacteria detected fell into Lachnospiraceae, Ruminococcaceae, Bacteroidaceae, Enterobacteriaceae, Streptococcaceae, Lactobacillaceae, Bifidobacteriaceae, Veillonellaceae, Peptostreptococcaceae, Prevotellaceae, and Oscillospiraceae, which occupied &#x003E;80% of the total microbiota in PSD group (<xref ref-type="fig" rid="F2">Figure 2B</xref>). Compared with the non-PSD group, PSD group showed lower relative abundances of Enterobacteriaceae and higher relative abundance of Bacteroidacea and Streptococcaceae. At the genera level (<xref ref-type="fig" rid="F2">Figure 2C</xref>), the top five enriched genera were <italic>Bacteroides, Blautia, Escherichia-Shigella, Streptococcus</italic>, and <italic>Lactobacillus</italic>. PSD group showed lower relative abundances of <italic>Escherichia-Shigella</italic> and higher relative abundance of <italic>Bacteroides and Streptococcus</italic> compared with the non-PSD group. Co-occurrence clustering analysis of the top 200 genera of relative abundance were presented in <xref ref-type="fig" rid="F3">Figure 3</xref>. The absolute value of coefficient was set as more than 0.6. The network of PSD contained a total of 45 nodes and 50 edges with the average degree of 2.22 and average clustering of 0.16. The network of non-PSD contained a total of 27 nodes and 42 edges with the average degree of 3.03 and average clustering of 0.21. The results showed that the microbial networks in PSD were sparser than in non-PSD. The clustering coefficient of gut microbiota network in PSD group was lower than that in non-PSD group, indicating that the compactness of the network was reduced (from 6 to 5).</p>
<fig id="F2" position="float">
<label>FIGURE 2</label>
<caption><p>Composition of gut microbiota between PSD and non-PSD groups. <bold>(A)</bold> Predominant bacteria at the phylum level, each bar represents one sample. Relative abundances of bacteria between groups at the family level <bold>(B)</bold> and genus <bold>(C)</bold> level.</p></caption>
<graphic mimetype="image" mime-subtype="tiff" xlink:href="fnagi-15-1116065-g002.tif"/>
</fig>
<fig id="F3" position="float">
<label>FIGURE 3</label>
<caption><p>Microbiota correlation network of PSD and non-PSD groups. Each circular node represents a genus. The connecting lines between the two samples represent their Spearman index correlation. <bold>(A)</bold> Correlation network of non-PSD. <bold>(B)</bold> Correlation network of PSD.</p></caption>
<graphic mimetype="image" mime-subtype="tiff" xlink:href="fnagi-15-1116065-g003.tif"/>
</fig>
</sec>
<sec id="S3.SS3">
<title>3.3. Differential signatures of gut microbiota in PSD and non-PSD groups</title>
<p>A LEfSe analysis was used to screen the differential biomarkers of the gut microbiota to explore the specific bacteria associated with PSD. The taxonomic cladogram showed the dominant species of gut microbiota in the two groups from phylum level to genus level (<xref ref-type="fig" rid="F4">Figure 4A</xref>). We marked 31 distinguishing taxa with differential abundances between two groups by LDA scores above 2.0 (<xref ref-type="fig" rid="F4">Figure 4B</xref>). Compared with the non-PSD group, the abundance of phylum Verrucomicrobiota (<italic>P</italic> = 0.048) and Cyanobacteria (<italic>P</italic> = 0.011) in PSD group is higher, and the abundance of phylum Synergistota (<italic>P</italic> = 0.014) is lower (<xref ref-type="fig" rid="F5">Figure 5A</xref>, all <italic>P</italic> &#x003C; 0.05). Compared with the non-PSD group, the abundance of family Akkermansiaceae (<italic>P</italic> = 0.035), Barnesiellaceae (<italic>P</italic> = 0.0016), Norank_o_Chloroplast (<italic>P</italic> = 0.035) and Staphylococaceae (<italic>P</italic> = 0.0015) in PSD group is higher, and the abundance of family Butyricicoccaceae (<italic>P</italic> = 0.0099) and Synergistaceae (<italic>P</italic> = 0.014) is lower (<xref ref-type="fig" rid="F5">Figure 5B</xref>). At the genus level, PSD exhibited a lower relative abundance of <italic>Escherichia-Shigella</italic> (<italic>P</italic> = 0.043), <italic>unclassified_f_Lachnospiraceae</italic> (<italic>P</italic> = 0.039), <italic>Butyricicoccus</italic> (<italic>P</italic> = 0.012), and <italic>Holdemanella</italic> (<italic>P</italic> = 0.025), and a higher relative abundance of <italic>Streptococcus</italic> (<italic>P</italic> = 0.042), <italic>Akkermansia</italic> (<italic>P</italic> = 0.035), and <italic>Barnesiella</italic> (<italic>P</italic> = 0.0043) (<xref ref-type="fig" rid="F5">Figure 5C</xref>).</p>
<fig id="F4" position="float">
<label>FIGURE 4</label>
<caption><p>Differential bacteria of gut microbiota between PSD and non-PSD groups. <bold>(A)</bold> Annotated branch diagram of the different bacteria between PSD and non-PSD patients. <bold>(B)</bold> LEfSe analysis showing the most differentially abundant taxa between PSD and non-PSD groups. Red and green bars represented species with relatively higher abundance in PSD and non-PSD patients, respectively. bacterial taxa are shown with a LDA score &#x003E;2.0.</p></caption>
<graphic mimetype="image" mime-subtype="tiff" xlink:href="fnagi-15-1116065-g004.tif"/>
</fig>
<fig id="F5" position="float">
<label>FIGURE 5</label>
<caption><p>Comparison of the significant bacteria in PSD and non-PSD groups. The relative abundances of the significant bacteria at the phylum level <bold>(A)</bold>, the family <bold>(B)</bold> and the genus level <bold>(C)</bold> in PSD patients compared with non-PSD patients. &#x002A;<italic>P</italic> &#x003C; 0.05.</p></caption>
<graphic mimetype="image" mime-subtype="tiff" xlink:href="fnagi-15-1116065-g005.tif"/>
</fig>
</sec>
<sec id="S3.SS4">
<title>3.4. Correlation analysis of gut microbiota composition and clinical indicators</title>
<p>As shown in <xref ref-type="fig" rid="F6">Figure 6</xref>, the correlations between differential species and diverse clinical indexes were estimated by the Spearman correlation analysis. The clinical indexes were mainly involving demographic characteristics (educational level, diabetes mellitus, alcohol drinking and Barthel index), laboratory examinations (FT3) and psychiatric outcomes evaluation (NIHSS and MMSE). <italic>Akkermansia</italic> (<italic>P</italic> &#x003C; 0.05), <italic>Barnesiella</italic> (<italic>P</italic> &#x003C; 0.05), and <italic>Pyramidobacter</italic> (<italic>P</italic> &#x003C; 0.01) were positively related with HAMD, while <italic>Holdemanella</italic> (<italic>P</italic> &#x003C; 0.01) and <italic>norank_f_norank_o_Chloroplast</italic> (<italic>P</italic> &#x003C; 0.01) negatively connected with HAMD. MMSE score was positively associated with <italic>Butyricicoccus</italic> (<italic>P</italic> &#x003C; 0.05), while negatively associated with <italic>Pyramidobacter</italic> (<italic>P</italic> &#x003C; 0.001).</p>
<fig id="F6" position="float">
<label>FIGURE 6</label>
<caption><p>The correlation analysis between the differential bacteria and clinical indexes. Spearman correlations between gut microbiota and clinical indicators. Red and blue indicate positive and negative correlations, respectively. &#x002A;<italic>P</italic> &#x003C; 0.05, &#x002A;&#x002A;<italic>P</italic> &#x003C; 0.01, &#x002A;&#x002A;&#x002A;<italic>P</italic> &#x003C; 0.001.</p></caption>
<graphic mimetype="image" mime-subtype="tiff" xlink:href="fnagi-15-1116065-g006.tif"/>
</fig>
</sec>
<sec id="S3.SS5">
<title>3.5. Diagnostic potential of PSD based on gut microbial markers</title>
<p>To further explore the value of microbial signatures in the prediction of PSD, this study picked out genera <italic>Akkermansia</italic> and <italic>Holdemanella</italic> which were closely related to HAMD with relatively high abundance, and the top seven bacteria. Then, receiver operating characteristic (ROC) curve analyses were carried out according to the relative abundance of the top seven bacteria. As shown in <xref ref-type="fig" rid="F7">Figure 7</xref>, <italic>Akkermansia</italic>, <italic>Holdemanella</italic> and the combination of seven bacteria in the distinguishing between PSD and non-PSD had AUC of 0.563, 0.565, and 0.705, respectively (95% CI: 0.486&#x2013;0.640;95% CI: 0.491&#x2013;0.640;95% CI: 0.634&#x2013;0.771), suggesting that the characteristic bacteria might be a well candidate for the diagnosis of PSD.</p>
<fig id="F7" position="float">
<label>FIGURE 7</label>
<caption><p>Potential microbiota biomarkers distinguished PSD group from non-PSD group. ROC curve showed the ability to differentiate PSD group from non-PSD group based on specific bacteria.</p></caption>
<graphic mimetype="image" mime-subtype="tiff" xlink:href="fnagi-15-1116065-g007.tif"/>
</fig>
</sec>
</sec>
<sec id="S4" sec-type="discussion">
<title>4. Discussion</title>
<p>The pathogenesis of PSD was usually affected by many factors, including gut microbiota. Our analysis revealed a significant difference in gut microbiota composition between PSD and non-PSD groups. Then, we proposed that bacterial biomarkers, such as diversity, abundance feature and specific bacteria, might be useful to identify patients who were likely to develop PSD.</p>
<p>In this study, gender, education level, diabetes mellitus, alcohol drinking, Barthel Index, FT3 differ significantly in PSD and non-PSD, which may be attributed to the occurrence of PSD compared with non-PSD. Many researchers have investigated a series of scoring systems from PSD prediction (<xref ref-type="bibr" rid="B36">Pan et al., 2022</xref>; <xref ref-type="bibr" rid="B44">Yi et al., 2022</xref>). Prospective studies assessed the predictive power of HAMD score for PSD, which were commonly used in clinical (<xref ref-type="bibr" rid="B24">Kang et al., 2013</xref>). There were still flaws in this method. Besides, HAMD score was usually assessed 3 months after the stroke discharge, which is to the disadvantage of early clinical judgment of PSD. However, more relevant data should be included to improve the early recognition of patients.</p>
<p>A large amount of evidence showed that the balance of gut microbiota was disrupted in patients with various brain diseases, such as Parkinson&#x2019;s disease, Alzheimer&#x2019;s disease, Wilson&#x2019;s disease, depression, etc. (<xref ref-type="bibr" rid="B8">Bravo et al., 2011</xref>; <xref ref-type="bibr" rid="B14">Dinan and Cryan, 2013</xref>; <xref ref-type="bibr" rid="B2">Ait-Belgnaoui et al., 2014</xref>; <xref ref-type="bibr" rid="B25">Kennedy et al., 2017</xref>). Moreover, several clinical studies have reported that patients with AIS exhibit gut dysbiosis and, in turn, changes in the gut microbiota affected neuroinflammatory and functional outcome after brain injury (<xref ref-type="bibr" rid="B40">Singh et al., 2016</xref>). Patients with PSCI also had significantly different gut microbiota at multiple taxonomic levels, compared to AIS patients without cognitive impairment. Further study showed that fecal microbiota transplantation from patients to stroke mice was performed to examine the causal relationship between the gut microbiota and PSCI. These results indicated close contact between gut microbiota and complications after a stroke (<xref ref-type="bibr" rid="B5">Benakis et al., 2016</xref>). This study analyzed the characteristics of gut microbiota in patients with PSD. Although there was no significant difference in &#x03B1; diversity of PSD group compared with non-PSD group, but profound alteration in gut microbial structure were discovered in PSD patients. In this study, compared with the non-PSD group, the microbial composition of PSD group was characterized by a decrease in the abundance of the genus <italic>Escherichia-Shigella, Butyricicoccus</italic>, and <italic>Holdemanella</italic> as well as an increase in the abundance of the genus <italic>Streptococcus</italic>, <italic>Akkermansia</italic>, and <italic>Barnesiella.</italic> Moreover, three bacteria <italic>Akkermansia, Barnesiella</italic>, and <italic>Pyramidobacter</italic> were positively correlated with HAMD score, while <italic>Holdemanella</italic> was negatively correlated with HAMD score, which might predict PSD patients. <italic>Akkermansia</italic> is generally considered to be beneficial to human physiology (<xref ref-type="bibr" rid="B26">Kong et al., 2016</xref>), however, its changes are inconsistent in many brain diseases. The unpredictable restraint stress potentiated rotenone-induced effects in the colon including increased <italic>Akkermansia</italic> (<xref ref-type="bibr" rid="B15">Dodiya et al., 2018</xref>). Studies have shown that the abundance of <italic>Akkermansia</italic> in brain diseases including multiple sclerosis (<xref ref-type="bibr" rid="B10">Cantarel et al., 2015</xref>; <xref ref-type="bibr" rid="B7">Berer et al., 2017</xref>), PD (<xref ref-type="bibr" rid="B23">Heintz-Buschart et al., 2018</xref>), and AD patients (<xref ref-type="bibr" rid="B28">Li et al., 2019</xref>) were increased. Our previous studies demonstrated that the abundance of <italic>Akkermansia</italic> in the sepsis-induced cognitive impairment mice (<xref ref-type="bibr" rid="B33">Liu et al., 2021</xref>) and AD model mice (<xref ref-type="bibr" rid="B41">Sun et al., 2019</xref>) were significantly increased. This contrasts with former studies, where a decrease in the genus <italic>Akkermansia</italic> in PD (<xref ref-type="bibr" rid="B1">Aho et al., 2019</xref>) and APP/PS1 mouse model (<xref ref-type="bibr" rid="B22">Harach et al., 2017</xref>) were reported. The effect of <italic>Akkermansia</italic> was inconsistent, which has both beneficial effect and negative effect (<xref ref-type="bibr" rid="B13">Desai et al., 2016</xref>; <xref ref-type="bibr" rid="B26">Kong et al., 2016</xref>). <italic>Akkermansia</italic> was involved in immune regulation, which possessed both regulatory and pro-inflammatory properties (<xref ref-type="bibr" rid="B12">Derrien et al., 2004</xref>). <italic>Akkermansia</italic> can induce inflammatory responses, neurotoxicity, and blood-brain barrier disruption in the microenvironment of gliomas through its ability to degrade the intestinal mucosal layer (<xref ref-type="bibr" rid="B37">Patrizz et al., 2020</xref>), could aggravate inflammation during infection (<xref ref-type="bibr" rid="B18">Ganesh et al., 2013</xref>). <italic>Streptococcus</italic> has been shown to exhibit pro-inflammatory responses. In this study, the genus <italic>Streptococcus</italic> was significantly increased in PSD patients. A case-control study that genera <italic>Streptococcus</italic> were enriched in the depression school-aged children compared with healthy controls (<xref ref-type="bibr" rid="B32">Ling et al., 2022</xref>). It was reported that genus <italic>Streptococcus</italic> were significantly increased in the major depressive disorder and bipolar disorder with current major depressive episode groups compared with health participants (<xref ref-type="bibr" rid="B38">Rong et al., 2019</xref>). These were characterized by increased relative abundances of taxa that include strains with inflammatory properties, suggesting a potential mediator of inflammation between the gut microbiota and PSD. In addition to exploring the underlying pathogens, this study also evaluated the decreased abundance bacteria in PSD patients, including <italic>Escherichia-Shigella, Butyricicoccus</italic>, and <italic>Holdemanella</italic>. Therefore, bacteria alteration with the increase of opportunistic pathogens and the decrease of beneficial bacteria may be a risk factor for PSD. Moreover, a diagnostic model for PSD was established using seven abundant bacteria, and the AUC area exhibited satisfactory predictive performance. This finding suggested that PSD patients experienced more differences in gut microbial structure related to depressive symptoms, and characteristic bacteria can be used as diagnostic biomarkers for PSD.</p>
<p>There are several limitations to the present study. First, gut microbiota stool samples were collected at a single time point of admission. Future research needs longitudinal design to monitor the diversity and community composition of gut microbiota at different time points, so as to better understand the dynamic changes of microbiota in PSD patients. Second, although we tried to consider the influence of environmental factors (region, diet, educational background) on the depressive state and microbial population of AIS patients, there was still a lack of further detailed and comprehensive information (such as socioeconomic status, social support, seasonal factors, etc.). More detailed dietary and lifestyle factors information of the participants need provided to assess whether and how dietary habits affect the microbial composition of- PSD patients. The participants adopted different diet and style, which may lead to bacterial variations. Lastly, the sample size was limited, thus these conclusions may require careful interpretation. Large-scale multicenter and cross-regional studies are necessary to estimate the role of gut microbiota in predicting the diagnosis of PSD.</p>
<p>In conclusion, this study revealed that gut microbiome of PSD patients has changed, which is a predictor of PSD. <italic>Escherichia-Shigella, Butyricicoccus</italic>, <italic>Akkermansia</italic>, and <italic>Barnesiella</italic> were microbial biomarkers for PSD, which was worthy of further study on clinical application. Our findings may help to early predict PSD and provide information for clinical decision-making of patients.</p>
</sec>
<sec id="S5" sec-type="data-availability">
<title>Data availability statement</title>
<p>The datasets presented in this study can be found in online repositories. The names of the repository/repositories and accession number(s) can be found below: <ext-link ext-link-type="uri" xlink:href="https://www.ncbi.nlm.nih.gov/">https://www.ncbi.nlm.nih.gov/</ext-link>, <ext-link ext-link-type="DDBJ/EMBL/GenBank" xlink:href="PRJNA905676">PRJNA905676</ext-link>.</p>
</sec>
<sec id="S6" sec-type="ethics-statement">
<title>Ethics statement</title>
<p>This study was approved by Ethics Committee of the Second Affiliated Hospital of Wenzhou Medical University. The patients/participants provided their written informed consent to participate in this study.</p>
</sec>
<sec id="S7" sec-type="author-contributions">
<title>Author contributions</title>
<p>JL, JS, and QT: conception or design of the work. SY, HX, YW, NS, QC, YZ, QG, and JZ: data collection and analysis. All authors contributed to the article and approved the submitted version.</p>
</sec>
</body>
<back>
<sec id="S8" sec-type="funding-information">
<title>Funding</title>
<p>This work was supported by Clinical Medical Research Project of Zhejiang Medical Association (2022ZYC-D10).</p>
</sec>
<sec id="S9" sec-type="COI-statement">
<title>Conflict of interest</title>
<p>The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.</p>
</sec>
<sec id="S10" sec-type="disclaimer">
<title>Publisher&#x2019;s note</title>
<p>All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.</p>
</sec>
<sec id="S11" sec-type="supplementary-material">
<title>Supplementary material</title>
<p>The Supplementary Material for this article can be found online at: <ext-link ext-link-type="uri" xlink:href="https://www.frontiersin.org/articles/10.3389/fnagi.2023.1116065/full#supplementary-material">https://www.frontiersin.org/articles/10.3389/fnagi.2023.1116065/full#supplementary-material</ext-link></p>
<supplementary-material xlink:href="Image_1.tif" id="FS1" mimetype="image/tiff" xmlns:xlink="http://www.w3.org/1999/xlink">
<label>Supplementary Figure 1</label>
<caption><p>Flowchart of patients included in the study.</p></caption>
</supplementary-material>
<supplementary-material xlink:href="Image_2.tif" id="FS2" mimetype="image/tiff" xmlns:xlink="http://www.w3.org/1999/xlink">
<label>Supplementary Figure 2</label>
<caption><p>Composition of gut microbiota beta-diversity between PSD and non-PSD groups. Beta-diversity illustrating the grouping patterns of PSD and non-PSD groups by principal coordinate analysis.</p></caption>
</supplementary-material>
<supplementary-material xlink:href="Table_1.tiff" id="TS1" mimetype="image/tiff" xmlns:xlink="http://www.w3.org/1999/xlink"/>
<supplementary-material xlink:href="Table_2.tiff" id="TS2" mimetype="image/tiff" xmlns:xlink="http://www.w3.org/1999/xlink"/>
</sec>
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