Oral microbiome composition, but not diversity, is associated with adolescent anxiety and depression symptoms

Association between oral microbiome and depression: A population-based study

OBJECTIVE

Depression is a global mental health issue, particularly affecting adolescents and young adults. While the role of gut microbiota in depression has been extensively studied, the influence of the oral microbiome remains underexplored. Recent studies suggest that the oral microbiome may affect systemic and brain health through the oral-brain axis. This study aimed to investigate the relationship between oral microbiome diversity and depression using data from 6212 participants in the National Health and Nutrition Examination Survey (NHANES) 2009-2012.

METHODS

Oral microbiome diversity was assessed through oral rinse samples using 16S rRNA sequencing, focusing on α-diversity metrics (observed ASVs and Faith's phylogenetic diversity) and β-diversity measures. Depressive symptoms were evaluated with the Patient Health Questionnaire (PHQ-9). Weighted logistic regression models were employed to assess associations between α-diversity and depression, while linear regression was used to examine the relationship between α-diversity and PHQ-9 scores. β-diversity differences were analyzed via permutational analysis of variance (PERMANOVA).

RESULTS

10.03% of the participants were diagnosed with depression. Higher α-diversity in the oral microbiome was negatively correlated with depression: observed ASVs (OR: 0.713 [CI: 0.508-0.999], P = 0.050) and Faith's phylogenetic diversity (OR: 0.584 [CI: 0.367-0.931], P = 0.025). Linear regression indicated that greater α-diversity was associated with lower PHQ-9 scores, reflecting fewer depressive symptoms. Furthermore, β-diversity analysis revealed significant differences in the microbiome composition between depressed and non-depressed individuals.

CONCLUSION

Reduced oral microbiome diversity is associated with an increased risk and severity of depression. The study underscores the importance of exploring the oral-brain axis and highlights the need for further research into the mechanisms and therapeutic strategies targeting this relationship.

Oral microbiota among treatment-naïve adolescents with depression: A case-control study

BACKGROUND

Adolescent depression has profound impacts on physical, cognitive, and emotional development. While gut microbiota changes have been linked to depression, the relationship between oral microbiota and depression remains elusive. Our study aims to investigate the oral microbiota in treatment-naïve adolescents experiencing depression and examine their potential associations with cognitive function.

METHODS

Our case-control study comprised two groups of adolescents aged 12-17: the depression group, including treatment-naïve individuals diagnosed with DSM-5 major depressive disorder (MDD), and a healthy control group of non-depressed individuals (HC). Participants underwent structured neuropsychiatric assessments, and fasting morning saliva samples were collected for the 16S rRNA sequencing to investigate the oral microbiota.

RESULTS

Significant differences were identified in the α- and β-diversities of the oral microbiota between MDD and HC groups. Specific bacterial taxa, including genera Streptococcus, Neisseria, Hemophilus, Fusobacterium, and g_norank_f_norank_o_Absconditabacteriales_SR1, were significantly associated with MDD. The association extends to cognitive functions, where correlations were observed between certain oral bacteria and cognitive scores, including instant and delayed memory, visual breadth, and speech features for the combined MDD and HC individuals (p < 0.05). Random forest analysis identified ten genera of oral microbes with the highest predictive values for MDD. The area under the curve (AUC) is 0.78 in the receiver operating characteristic (ROC) curve analysis.

CONCLUSION

Our results highlight the oral microbiota's role as a biomarker for adolescent depression and its impact on cognitive functions. These insights underscore the need for further research into the links between oral health, mental health, and cognitive functions.

Oropharyngeal microbiota in patients with psychotic disorders: A scoping review on compositional and functional alterations

BACKGROUNDS

Oropharyngeal microbiota may be implicated in the onset and progression of psychotic disorders. This scoping review aims to map the existing evidence concerning the composition, diversity, and metabolic pathways of the oropharyngeal microbiota in patients aged 18 to 65 with a main diagnosis of a psychotic disorder, including individuals at clinical high-risk for psychosis (CHRP) or experiencing first episode psychosis (FEP).

METHODS

The scoping review was performed according to the PRISMA-ScR checklist. The systematic literature search was conducted using PubMed, Web of Science, and CINAHL until February 2024.

RESULTS

Seven cross-sectional studies were included, comprising 43 individuals at CHRP, 13 with FEP, 85 with first-episode of schizophrenia (FES), 171 with schizophrenia, and 8 with another schizophrenia spectrum disorder. The oropharyngeal microbiota showed an increase in Lactobacillus gasseri abundance in schizophrenia, and in Firmicutes/Proteobacteria phylum ratio in patients experiencing CHR-P and FES. In schizophrenia, an altered β-diversity was observed alongside increased metabolic pathways related to metabolite transporters. In FES, higher α-diversity and disruptions in amino acid, carbohydrate, and xenobiotic metabolism pathways were found. Hydrogen sulfide (H2S)-producing bacteria were generally enriched in all the stages of disease. Correlations were observed between oropharyngeal microbiota and psychotic symptom domains.

CONCLUSIONS

Potential microbial signatures, such as Lactobacillus gasseri and H2S-producing bacteria, were identified in the oropharyngeal microbiota. Alterations in the oropharyngeal microbiota composition and function may be associated with different stages of psychotic disorders, with some overlap between CHR-P and FES.

Association of Oral Microbiome Diversity With Depression Status: NHANES 2009-2012

OBJECTIVES

To investigate the relationship between oral microbial diversity and depression symptoms in the U.S.

POPULATION

METHODS

We utilized the US National Health and Nutrition Examination Survey (NHANES; 2009-2012) to assess the association between oral microbial diversity and depression symptoms. A cut-off PHQ-9 score of 15 was used to define severe depression symptoms. We conducted the multivariate linear regression to explore the association of the amplicon sequence variants (ASVs) with PHQ-9 scores. A restricted cubic spline (RCS) model was introduced to curve the dose-response relationship. A logistic regression model was used to calculate the odds ratio (OR) and 95% confidence interval (CI) of the association between ASVs and the risk of severe depression symptoms. Based on Bray-Curtis dissimilarity of beta diversity, analysis of similarity (ANOSIM) is used to assess the dissimilarity between different depression groups.

RESULTS

A total of 1497 participants were included, with 111 (7.41%) meeting the criteria for severe depression. After adjusting for confounders, we found that ASVs were negatively correlated with PHQ-9 scores (β = -0.008, p = 0.014). The RCS plot showed a linear relationship (pnon-linear = 0.232). Logistic regression showed that ASVs were associated with a decreased risk of severe depression symptoms (OR = 0.992, p = 0.003). Analysis of β diversity identified a statistically significant difference (R = 0.087, p = 0.003). Additionally, we developed a nomogram to estimate an individual's risk of severe depression symptoms.

CONCLUSIONS

Alpha diversity of the oral microbiota was associated with a reduced risk of severe depression symptoms, which could contribute to the early identification and intervention of severe depression.

Dysbiotic oral microbiota-derived kynurenine, induced by chronic restraint stress, promotes head and neck squamous cell carcinoma by enhancing CD8+ T cell exhaustion

BACKGROUND

Chronic restraint stress (CRS) is a tumour-promoting factor. However, the underlying mechanism is unknown.

OBJECTIVE

We aimed to investigate whether CRS promotes head and neck squamous cell carcinoma (HNSCC) by altering the oral microbiota and related metabolites and whether kynurenine (Kyn) promotes HNSCC by modulating CD8+ T cells.

DESIGN

4-nitroquinoline-1-oxide (4NQO)-treated mice were exposed to CRS. Germ-free mice treated with 4NQO received oral microbiota transplants from either CRS or control mouse donors. 16S rRNA gene sequencing and liquid chromatography-mass spectrometry were performed on mouse saliva, faecal and plasma samples to investigate alterations in their microbiota and metabolites. The effects of Kyn on HNSCC were studied using the 4NQO-induced HNSCC mouse model.

RESULTS

Mice subjected to CRS demonstrated a higher incidence of HNSCC and oral microbial dysbiosis than CRS-free control mice. Pseudomonas and Veillonella species were enriched while certain oral bacteria, including Corynebacterium and Staphylococcus species, were depleted with CRS exposure. Furthermore, CRS-altered oral microbiota promoted HNSCC formation, caused oral and gut barrier dysfunction, and induced a host metabolome shift with increased plasma Kyn in germ-free mice exposed to 4NQO treatment. Under stress conditions, we also found that Kyn activated aryl hydrocarbon receptor (AhR) nuclear translocation and deubiquitination in tumour-reactive CD8+ T cells, thereby promoting HNSCC tumourigenesis.

CONCLUSION

CRS-induced oral microbiota dysbiosis plays a protumourigenic role in HNSCC and can influence host metabolism. Mechanistically, under stress conditions, Kyn promotes CD8+ T cell exhaustion and HNSCC tumourigenesis through stabilising AhR by its deubiquitination.

The mind, brain, and body study: A protocol for examining the effects of the gut-brain-immune axis on internalizing symptoms in youth exposed to caregiving-related early adversity

Experiences of caregiving-related adversity are common and one of the strongest predictors of internalizing psychopathology (i.e., anxiety and depression). Specifically, individuals who have been exposed to such early adversities have altered affective neurodevelopment, impaired memory systems, increased risk of developing internalizing disorders, greater inflammation, and differences in gastrointestinal (gut) microbiome composition. Crucially, the gut microbiome undergoes a sensitive period of development that precedes neural and immune sensitive periods, thus making it a potentially fruitful target for intervention. Though previous work has assessed neural, immune, and gut microbiome systems in individuals exposed to early adversity, studies have primarily looked at these biological systems independently. The Mind, Brain, and Body study (MBB) implements multimodal and longitudinal design to assess how changes in the gut microbiome following caregiving-related adversity may underlie altered affective neurodevelopment, memory, and immune functioning in youth and contribute to internalizing symptoms. Across three waves, spread approximately 12-18 months apart, youth with and without previous experiences of caregiving-related adversity completed self-report measures of mental and physical health, provided stool, saliva, hair, and blood samples, and completed an MRI scan. Results of this study will expand our knowledge on how the gut microbiome shapes several biological and cognitive systems and motivate future work investigating the gut microbiome as potential target for intervention.

Stress and mental health symptoms in early pregnancy are associated with the oral microbiome

BACKGROUND

Research has revealed associations between microbes of the gastrointestinal tract and stress, anxiety and depression in pregnant or postpartum women. While these studies suggest a gut-brain-behaviour axis, no studies have examined microbes of the oral cavity in relation to maternal mental health.

OBJECTIVE

To explore a potential oral-brain-behaviour axis related to maternal mental health.

METHODS

Microbes were measured in saliva obtained from 224 second-trimester (mean±SD = 17±2 weeks) women oversampled for stress. Oralome data were associated with women's recent or cumulative pregnancy stress, trait and state anxiety, depression symptoms and post-traumatic stress disorder (PTSD) symptoms. Covariates explored included age, income, alcohol and tobacco use, dental issues and physical health problems.

RESULTS

Pregnant women in the high trait anxiety or depression symptom groups had higher oral alpha diversity, indicating higher richness of species within samples. Groups with high and low PTSD symptoms differed in beta diversity, reflecting differences in community composition. Linear discriminant analysis showed differently abundant microbes in women with high stress versus low life stress, anxiety, depression, and PTSD, with the affected microbes mostly differing by symptom. Notably, members of phylum Proteobacteria were more abundant in women with high recent life stress and Spirochaetes was more abundant in women with high depression symptoms. Members of phylum Firmicutes were more abundant in the high trait anxiety and high depression groups. Genus Dialister (previously found to be lower in the gut of depressed non-pregnant people) was higher in women experiencing either high trait or state anxiety, or experiencing high depression symptoms, while genus Eikenella was elevated with high trait anxiety, depression or PTSD.

CONCLUSIONS

The oral microbiome is associated with stress and mental health in pregnant women, in ways different from the gut microbiome or what has been found in non-pregnant people.

CLINICAL IMPLICATIONS

Understanding oral microbiome-mental health relations may reveal future microbial targets to improve maternal psychological well-being.

Characteristics of the oral microbiome in youth exposed to caregiving adversity

Caregiving adversity (CA) exposure is robustly linked to increased risk for poor oral, physical, and mental health outcomes. Increasingly, the gut microbiome has garnered interest as a contributor to risk for and resilience to such health outcomes in CA-exposed individuals. Though often overlooked, the oral microbiome of CA-exposed individuals may be just as important a contributor to health outcomes as the gut microbiome. Indeed, outside the context of CA, the oral microbiome is well-documented as a regulator of both oral and systemic health, and preliminary data suggest its association with mental health. However, research examining the association between CA and the oral microbiome is extremely sparse, especially in childhood, when the community composition of such organisms is still stabilizing. To address that sparsity, in the current study, we examined composition and differential abundance metrics of the oral microbiome in 152 youth aged 6-16 years, who had either been exposed to significant caregiving adversity (significant separation from or maltreatment by a caregiver; N = 66, CA) or who had always remained with their biological/birth families (N = 86, Comparison). We identified a significant negative association between hair cortisol and oral microbiome richness in the Comparison group that was significantly blunted in the CA group. Additionally, youth in the CA group had altered oral microbiome composition and elevated abundance of potentially pathogenic bacteria relative to youth in the Comparison group. Questionnaire measures of fatigue, somatic complaints, and internalizing symptoms had limited associations with oral microbiome features that were altered in CA. Although we found differences in the oral microbiomes of CA-exposed youth, further research is required to elucidate the implications of those differences for health and well-being.

Probing the oral-brain connection: oral microbiome patterns in a large community cohort with anxiety, depression, and trauma symptoms, and periodontal outcomes

The role of the oral microbiome in mental health has recently been appreciated within the proposed oral-brain axis. This study examined the structure and composition of the salivary microbiome in a large-scale population-based cohort of individuals reporting mental health symptoms (n = 306) compared to mentally healthy controls (n = 164) using 16S rRNA sequencing. Mental health symptoms were evaluated using validated questionnaires and included depression, anxiety, and posttraumatic stress disorder (PTSD), with accompanying periodontal outcomes. Participants also indicated current or previous diagnoses of anxiety, depression, periodontitis, and gingivitis. Mental and periodontal health variables influenced the overall composition of the oral microbiome. PTSD symptoms correlated with a lower clr-transformed relative abundance of Haemophilus sputorum and a higher clr-transformed relative abundance of Prevotella histicola. The clr-transformed relative abundance of P. histicola was also positively associated with depressive scores and negatively associated with psychological quality of life. Anxiety disorder diagnosis was associated with a lower clr-transformed relative abundance of Neisseria elongate and a higher clr-transformed relative abundance of Oribacterium asaccharolyticum. A higher clr-transformed relative abundance of Shuttleworthia and lower clr-transformed relative abundance of Capnocytophaga were evident in those who reported a clinical periodontitis diagnosis. Higher Eggerthia and lower Haemophilus parainfluenzae clr-transformed relative abundances were associated with reported clinical periodontitis diagnoses and psychotherapeutic efficacy. Functional prediction analysis revealed a potential role for tryptophan metabolism/degradation in the oral-brain axis, which was confirmed by lower plasma serotonin levels across symptomatic groups. This study sheds light on the intricate interplay between oral microbiota, periodontal and mental health outcomes, and a potential role for tryptophan metabolism in the proposed oral-brain axis, emphasizing the need for further exploration to pave the way for novel therapeutic interventions and predicting therapeutic response.

Balancing the Oral-Gut-Brain Axis with Diet

Background: The oral microbiota is the second largest microbial community in humans. It contributes considerably to microbial diversity and health effects, much like the gut microbiota. Despite physical and chemical barriers separating the oral cavity from the gastrointestinal tract, bidirectional microbial transmission occurs between the two regions, influencing overall host health. Method: This review explores the intricate interplay of the oral-gut-brain axis, highlighting the pivotal role of the oral microbiota in systemic health and ageing, and how it can be influenced by diet. Results: Recent research suggests a relationship between oral diseases, such as periodontitis, and gastrointestinal problems, highlighting the broader significance of the oral-gut axis in systemic diseases, as well as the oral-gut-brain axis in neurological disorders and mental health. Diet influences microbial diversity in the oral cavity and the gut. While certain diets/dietary components improve both gut and oral health, others, such as fermentable carbohydrates, can promote oral pathogens while boosting gut health. Conclusions: Understanding these dynamics is key for promoting a healthy oral-gut-brain axis through dietary interventions that support microbial diversity and mitigate age-related health risks.

Oral microbiome diversity shapes the association between sleep duration and depression

Background

Emerging research suggests the relationship between the oral microbiome and sleep duration with depression, however, the precise mechanisms by which oral microbial diversity influences the sleep-depression nexus remain to be elucidated.

Methods

We analyzed data from 4,692 participants in the National Health and Nutrition Examination Survey (NHANES), incorporating key demographic variables, oral microbiome diversity metrics, sleep duration, and depression assessment variables. Classical multidimensional scaling facilitated dimensionality reduction, while unsupervised clustering divided participants into groups based on β-diversity dissimilarity matrices. We examined the moderating effects of oral microbiome diversity on the sleep-depression relationship by incorporating interaction terms sleep-oral microbiome diversity into multiple linear regression models.

Results

Our analysis revealed a U-shaped relationship between sleep duration and depression. Specifically, α-diversity was a significant moderator, with reduced diversity linked to an increased depression risk in participants with insufficient sleep. Regarding β-diversity, using both Bray-Curtis and UniFrac distance measures, Cluster 2 exhibited the strongest associations in sleep-deprived individuals (Bray-Curtis: β = 1.02, p < 0.001; Weighted UniFrac: β = 0.91, p < 0.001). In contrast, Cluster 1 displayed notable effects in individuals with excessive sleep (Bray-Curtis: β = 0.63, p = 0.008). Additionally, Cluster 3 was prominently associated with depression in sleep-deprived participants using unweighted UniFrac distance (β = 0.93, p < 0.001), and Cluster 2 was significant among those with excessive sleep across both unweighted (β = 0.80, p = 0.0004) and weighted UniFrac distances (β = 0.60, p = 0.001).

Conclusion

This study highlights the crucial role of oral microbiome diversity in moderating the U-shaped relationship between sleep duration and depression risk.

Relationship between human oral microbiome dysbiosis and neuropsychiatric diseases: An updated overview

The role of the gut-brain axis in mental health disorders has been extensively studied. As the oral cavity is the starting point of the digestive tract, the role that the oral microbiota plays in mental health disorders has gained recent attention. Oral microbiota can enter the bloodstream and trigger inflammatory responses or translocate to the brain through the trigeminal nerve or olfactory system. Hence, the concept of the oral microbiota-brain axis has emerged. Several hypotheses have been suggested that the oral microbiota can enter the gastrointestinal tract and affect the gut-brain axis; however, literature describing oral-brain communication remains limited. This review summarizes the characteristics of oral microbiota and its mechanisms associated with mental health disorders. Through a comprehensive examination of the relationship between oral microbiota and various neuropsychiatric diseases, such as anxiety, depression, schizophrenia, autism spectrum disorder, epilepsy, Parkinson's disease, and dementia, this review seeks to identify promising avenues of future research.

Whole-Genome Metagenomic Analysis of the Oral Microbiota in Patients with Obstructive Sleep Apnea Comorbid with Major Depressive Disorder

Background

Obstructive sleep apnea (OSA) patients commonly experience high rates of depression. This study aims to examine the oral microbiota characteristics of OSA and those with comorbid major depressive disorder (OSA+MDD) patients.

Methods

Participants were enrolled from Aug 2022 to Apr 2023. Polysomnography, psychiatrist interviews, and scales were used to diagnose OSA and MDD. Oral samples were collected from participants by rubbing swabs on buccal mucosa, palate, and gums. Oral microbiota was analyzed via whole-genome metagenomics and bioinformatic analysis followed sequencing. Venous blood was drawn to detect plasma inflammatory factor levels.

Results

The study enrolled 33 OSA patients, 28 OSA+MDD patients, and 28 healthy controls. Significant differences were found in 8 phyla, 229 genera, and 700 species of oral microbiota among the three groups. Prevotellaceae abundance in the OSA and OSA+MDD groups was significantly lower than that in healthy controls. Linear discriminant analysis effect size (LEfSe) analysis showed that Streptococcaceae and Actinobacteria were the characteristic oral microbiota of the OSA and OSA+MDD groups, respectively. KEGG analysis indicates 30 pathways were changed in the OSA and OSA+MDD groups compared with healthy controls, and 23 pathways were changed in the OSA group compared with the OSA+MDD group. Levels of IL-6 in the OSA+MDD group were significantly higher than in the healthy group, correlating positively with the abundance of Schaalia, Campylobacter, Fusobacterium, Alloprevotella, and Candidatus Nanosynbacter in the oral, as well as with Hamilton Anxiety Rating Scale and Hamilton Depression Rating Scale scores.

Conclusion

Significant differences in oral microbiota populations and gene function were observed among the three groups. OSA patients were characterized by a decreased abundance of Prevotellaceae and an increased abundance of Streptococcaceae. OSA+MDD patients had an increased abundance of Actinobacteria. IL-6 might regulate the relationship between depression and the oral microbiota in OSA+MDD patients.

Adolescent alcohol use is associated with differences in the diversity and composition of the oral microbiome

BACKGROUND

Adolescence is a sensitive stage of oral microbial development that often coincides with the initiation and escalation of alcohol use. Thus, adolescents may be particularly susceptible to alcohol-induced alterations in the oral microbiome, though minimal research has been done in this area. Understanding the connection between the oral microbiome and alcohol use during adolescence is important to understand fully the biological consequences of alcohol use to mitigate potential adverse outcomes.

METHODS

Saliva samples were collected from adolescents aged 17-19 who used alcohol heavily (n = 21, 52.4% female) and those who did not use alcohol or any other substances (n = 18, 44.4% female). We utilized 16S rRNA sequencing to examine differences in microbial diversity and composition between the groups.

RESULTS

For alpha diversity, evenness was significantly lower in the drinking group than the control group as indicated by Pielou's evenness, Shannon, and Simpson indices. There were no statistically significant findings for beta diversity. Differential abundance analyses revealed higher abundances of Rothia and Corynebacterium in the alcohol-using group using both centered-log-ratio and relative abundance normalization. These genera are known for their high capacity to convert alcohol into acetaldehyde, a toxic metabolite reported to play a role in the neurobiological effects of alcohol. An unclassified Clostridia UCG-014, Streptobacillus, Comamonas, unclassified Lachnospiraceae, and Parvimonas were also identified as significantly different between groups when using only one of the normalization techniques.

CONCLUSIONS

This is the first study designed specifically to compare the oral microbiome of adolescents who use alcohol with that of control participants. Our findings reveal distinct alcohol-related differences in microbial composition and taxon abundance, emphasizing the importance of understanding the impact on the oral microbiome of alcohol use during adolescence. Because the oral microbiome is malleable, this study provides foundational work for future prevention and intervention studies.

Oral microbiota dysbiosis alters chronic restraint stress-induced depression-like behaviors by modulating host metabolism

Studies have shown that the microbiota-gut-brain axis is highly correlated with the pathogenesis of depression in humans. However, whether independent oral microbiome that do not depend on gut microbes could affect the progression of depression in human beings remains unclear, neither does the presence and underlying mechanisms of the microbiota-oral-brain axis in the development of the condition. Hence this study that encompasses clinical and animal experiments aims at investigating the correlation between oral microbiota and the onset of depression via mediating the microbiota-oral-brain axis. We compared the oral microbial compositions and metabolomes of 87 patients with depressive symptoms versus 70 healthy controls. We found that the oral microbial and metabolic signatures were significantly different between the two groups. Significantly, germ-free (GF) mice transplanted with saliva from mice exposing to chronic restraint stress (CRS) displayed depression-like behavior and oral microbial dysbiosis. This was characterized by a significant differential abundance of bacterial species, including the enrichment of Pseudomonas, Pasteurellaceae, and Muribacter, as well as the depletion of Streptococcus. Metabolomic analysis showed the alternation of metabolites in the plasma of CRS-exposed GF mice, especially Eicosapentaenoic Acid. Furthermore, oral and gut barrier dysfunction caused by CRS-induced oral microbiota dysbiosis may be associated with increased blood-brain barrier permeability. Pseudomonas aeruginosa supplementation exacerbated depression-like behavior, while Eicosapentaenoic Acid treatment conferred protection against depression-like states in mice. These results suggest that oral microbiome and metabolic function dysbiosis may be relevant to the pathogenesis and pathophysiology of depression. The proposed microbiota-oral-brain axis provides a new way and targets for us to study the pathogenesis of depression.

Uncovering the characteristics of the gut microbiota in patients with ischemic stroke and hemorrhagic stroke

This study aimed to explore the gut microbiota characteristics of ischemic and hemorrhagic stroke patients. A case-control study was conducted, and high-throughput sequencing of the V4-V5 region of 16S rRNA was used to analyze the differences in gut microbiota. The results showed that Proteobacteria was significantly increased in the ischemic stroke group compared with the healthy control group, while Fusobacteria was significantly increased in the hemorrhagic stroke group. In the ischemic stroke group, Butyricimonas, Alloprevotella, and Escherichia were significantly more abundant than in the healthy control group. In the hemorrhagic stroke group, Atopobium, Hungatella, Eisenbergiella, Butyricimonas, Odonbacter, Lachnociostridium, Alistipes, Parabacteroides, and Fusobacterium were significantly more abundant than in the healthy control group. Additionally, Alloprevotella, Ruminococcus, and Prevotella were significantly more abundant in the ischemic stroke group than in the hemorrhagic stroke group. The gut microbiota of ischemic and hemorrhagic stroke patients has significant diversity characteristics. These results provide new theoretical basis for exploring the prevention and treatment of different types of stroke through gut microbiota research.

Exploring the Association between Anxiety, Depression, and Gut Microbiota during Pregnancy: Findings from a Pregnancy Cohort Study in Shijiazhuang, Hebei Province, China

Negative emotions and gut microbiota during pregnancy both bear significant public health implications. However, the relationship between them has not been fully elucidated. This study, utilizing data from a pregnancy cohort, employed metagenomic sequencing to elucidate the relationship between anxiety, depression, and gut microbiota's diversity, composition, species, and functional pathways. Data from 87 subjects, spanning 225 time points across early, mid, and late pregnancy, were analyzed. The results revealed that anxiety and depression significantly corresponded to lower alpha diversity (including the Shannon entropy and the Simpson index). Anxiety and depression scores, along with categorical distinctions of anxiety/non-anxiety and depression/non-depression, were found to account for 0.723%, 0.731%, 0.651%, and 0.810% of the variance in gut-microbiota composition (p = 0.001), respectively. Increased anxiety was significantly positively associated with the abundance of Oscillibacter sp. KLE 1745, Oscillibacter sp. PEA192, Oscillibacter sp. KLE 1728, Oscillospiraceae bacterium VE202 24, and Treponema socranskii. A similar association was significantly noted for Oscillibacter sp. KLE 1745 with elevated depression scores. While EC.3.5.3.1: arginase appeared to be higher in the anxious group than in the non-anxious group, vitamin B12-related enzymes appeared to be lower in the depression group than in the non-depression group. The changes were found to be not statistically significant after post-multiple comparison adjustment.

A Holistic Approach for Ethics and Sustainability in the Food Chain: The Gateway to Oral and Systemic Health

Food production is a complex matter, affecting people's lives, organizations' profits, and the well-being of the whole planet, and has multifaceted ethical considerations surrounding its production, distribution, and consumption. This paper addresses the pressing need to confront ethical challenges within the food system, encompassing issues such as environmental sustainability, food security, and individual food choices for better oral and systemic health of all individuals around the globe. From agricultural practices to global trade and food waste, ethical implications are addressed across various domains, highlighting the interconnectedness of ethical decision-making in the food industry. Central themes explored include the ethical dimensions of food production methods, the impact of global trade on food ethics, and the role of individuals in making ethically informed food choices. Additionally, this paper considers the spiritual and physical significance of food, particularly through the lens of oral health as a gateway to holistic well-being. Recognizing the complexity of the food and mouth ecosystem, this paper calls for serious interventions in legislation and economics to promote ethical protocols and techniques for sustainability reasons. It emphasizes the importance of ethical considerations in food safety management systems, regulatory frameworks, and quality standards. Moreover, this paper underlines the need for a comprehensive approach to address ethical dilemmas and moral values inherent in the food industry and oral health policies, adopting the precautionary principle and ethical decision-making frameworks. This article finally aims to serve as a call to action for stakeholders across the food industry and the healthcare sector, to prioritize ethical practices, promote transparency, rearrange economic parameters, and work towards a more sustainable and equitable food system for inner and outer oral and systemic health and human sustainability for all.

Development and validation of a nomogram for predicting depressive symptoms in dentistry patients: A cross-sectional study

Depressive symptoms are frequently occur among dentistry patients, many of whom struggle with dental anxiety and poor oral conditions. Identifying the factors that influence these symptoms can enable dentists to recognize and address mental health concerns more effectively. This study aimed to investigate the factors associated with depressive symptoms in dentistry patients and develop a clinical tool, a nomogram, to assist dentists in predicting these symptoms. Methods: After exclusion of ineligible participants, a total of 1355 patients from the dentistry department were included. The patients were randomly assigned to training and validation sets at a 2:1 ratio. The LASSO regression method was initially employed to select highly influrtial features. This was followed by the application of a multi-factor logistic regression to determine independent factors and construct a nomogram. And it was evaluated by 4 methods and 2 indicators. The nomograms were formulated based on questionnaire data collected from dentistry patients. Nomogram2 incorporated factors such as medical burden, personality traits (extraversion, conscientiousness, and emotional stability), life purpose, and life satisfaction. In the training set, Nomogram2 exhibited a Concordance index (C-index) of 0.805 and an Area Under the Receiver Operating Characteristic Curve (AUC) of 0.805 (95% CI: 0.775-0.835). In the validation set, Nomogram2 demonstrated an Area Under the Receiver Operating Characteristic Curve (AUC) of 0.810 (0.768-0.851) and a Concordance index (C-index) of 0.810. Similarly, Nomogram1 achieved an Area Under the Receiver Operating Characteristic Curve (AUC) of 0.816 (0.788-0.845) and a Concordance index (C-index) of 0.816 in the training set, and an Area Under the Receiver Operating Characteristic Curve (AUC) of 0.824 (95% CI: 0.784-0.864) and a Concordance index (C-index) of 0.824 in the validation set. Net Reclassification Improvement (NRI) and Integrated Discrimination Improvement (IDI) indicated that Nomogram1, which included oral-related factors (oral health and dental anxiety), outperformed Nomogram2. We developed a nomogram to predict depressive symptoms in dentistry patients. Importantly, this nomogram can serve as a valuable psychometric tool for dentists, facilitating the assessment of their patients' mental health and enabling more tailored treatment plans.

Stress and depression-associated shifts in gut microbiota: A pilot study of human pregnancy

Background

Psychosocial stress and mood-related disorders, such as depression, are prevalent and vulnerability to these conditions is heightened during pregnancy. Psychosocial stress induces consequences via several mechanisms including the gut microbiota-brain axis and associated signaling pathways. Previous preclinical work indicates that prenatal stress alters maternal gut microbial composition and impairs offspring development. Importantly, although the fecal and vaginal microenvironments undergo alterations across pregnancy, we lack consensus regarding which shifts are adaptive or maladaptive in the presence of prenatal stress and depression. Clinical studies interrogating these relationships have identified unique taxa but have been limited in study design.

Methods

We conducted a prospective cohort study of pregnant individuals consisting of repeated administration of psychometrics (Perceived Stress Scale (PSS) and Center for Epidemiological Studies Depression Scale (CES-D)) and collection of fecal and vaginal microbiome samples. Fecal and vaginal microbial community composition across psychometric responses were interrogated using full-length 16S rRNA sequencing followed by α and β-diversity metrics and taxonomic abundance.

Results

Early pregnancy stress was associated with increased abundance of fecal taxa not previously identified in related studies, and stress from late pregnancy through postpartum was associated with increased abundance of typical vaginal taxa and opportunistic pathogens in the fecal microenvironment. Additionally, in late pregnancy, maternal stress and depression scores were associated with each other and with elevated maternal C-C motif chemokine ligand 2 (CCL2) concentrations. At delivery, concordant with previous literature, umbilical CCL2 concentration was negatively correlated with relative abundance of maternal fecal Lactobacilli. Lastly, participants with more severe depressive symptoms experienced steeper decreases in prenatal vaginal α-diversity.

Conclusion

These findings a) underscore previous preclinical and clinical research demonstrating the effects of prenatal stress on maternal microbiome composition, b) suggest distinct biological pathways for the consequences of stress versus depression and c) extend the literature by identifying several taxa which may serve critical roles in mediating this relationship. Thus, further interrogation of the role of specific maternal microbial taxa in relation to psychosocial stress and its sequelae is warranted.

Mood Disorders: The Gut Bacteriome and Beyond

Knowledge of the microbiome-gut-brain axis has revolutionized the field of psychiatry. It is now well recognized that the gut bacteriome is associated with, and likely influences, the pathogenesis of mental disorders, including major depressive disorder and bipolar disorder. However, while substantial advances in the field of microbiome science have been made, we have likely only scratched the surface in our understanding of how these ecosystems might contribute to mental disorder pathophysiology. Beyond the gut bacteriome, research into lesser explored components of the gut microbiome, including the gut virome, mycobiome, archaeome, and parasitome, is increasingly suggesting relevance in psychiatry. The contribution of microbiomes beyond the gut, including the oral, lung, and small intestinal microbiomes, to human health and pathology should not be overlooked. Increasing both our awareness and understanding of these less traversed fields of research are critical to improving the therapeutic benefits of treatments targeting the gut microbiome, including fecal microbiome transplantation, postbiotics and biogenics, and dietary intervention. Interdisciplinary collaborations integrating systems biology approaches are required to fully elucidate how these different microbial components and distinct microbial niches interact with each other and their human hosts. Excitingly, we may be at the start of the next microbiome revolution and thus one step closer to informing the field of precision psychiatry to improve outcomes for those living with mental illness.

Longitudinal Influence of Prescribed Antidepressants on Fecal and Oral Microbiomes Among Veterans With Major Depressive Disorder

OBJECTIVE

The purpose of this study was to evaluate the influence of a new course of antidepressant monotherapy on gut and oral microbiomes and the relationship to depressive symptoms.

METHODS

Longitudinal microbiome samples obtained from 10 U.S. veterans were analyzed. Baseline samples were taken before a new course of antidepressant monotherapy (either switching from a previous treatment or starting a new treatment). Targeted genomic sequencing of the microbiome samples was used to analyze changes in taxonomy and diversity across participants, medications, and medication class. Associations between these changes and Patient Health Questionnaire-9 (PHQ-9) scores were analyzed.

RESULTS

Taxonomic variability was observed across participants, with the individual being the main microbial community driver. In terms of the fecal microbiome, antidepressants were associated with shifts toward Bacteroides being less abundant and Blautia, Pseudomonas, or Faecalibacterium being more abundant. Likewise, the composition of the oral microbiome was variable, with individual participants being the primary drivers of community composition. In the oral samples, the relative abundance of Haemophilus decreased after antidepressants were started. Increases in Blautia and decreases in Bacteroides were associated with lower PHQ-9 scores.

CONCLUSIONS

Antidepressants were found to influence fecal and oral microbiomes such that a new course of antidepressant monotherapy was associated with taxonomic alterations toward healthier states in both fecal and oral microbiomes, which were associated with decreases in depressive symptoms. Additional longitudinal research is required to increase understanding of microbiomes and symptom-based changes, with a particular focus on potential differences between medication classes and underlying mechanisms.

Probiotics and Fecal Microbiota Transplantation in Major Depression: Doxa or Episteme?

In the human body, eukaryotic somatic cells and prokaryotic microorganisms live together. In this state, the body can be viewed as a "superorganism." Symbiotic life with commensal microorganisms can be observed in almost every part of the body. Intestinal microbiota plays an important role in health and disease, and in shaping and regulating neuronal functions from the intrauterine period to the end of life. Microbiota-based treatment opportunities are becoming more evident in both understanding the etiopathogenesis and treatment of neuropsychiatric disorders, especially depression. Antidepressant drugs, which are the first choice in the treatment of depression, also have antimicrobial and immunomodulatory mechanisms of action. From these perspectives, direct probiotics and fecal microbiota transplantation are treatment options to modulate microbiota composition. There are few preclinical and clinical studies on the effectiveness and safety of these applications in depression. The information obtained from these studies may still be at a doxa level. However, the probability that this information will become episteme in the future seems to be increasing.

Antibiotic-induced gut dysbiosis elicits gut-brain axis relevant multi-omic signatures and behavioral and neuroendocrine changes in a nonhuman primate model

Emerging evidence indicates that antibiotic-induced dysbiosis can play an etiological role in the pathogenesis of neuropsychiatric disorders. However, most of this evidence comes from rodent models. The objective of this study was to evaluate if antibiotic-induced gut dysbiosis can elicit changes in gut metabolites and behavior indicative of gut-brain axis disruption in common marmosets (Callithrix jacchus) - a nonhuman primate model often used to study sociability and stress. We were able to successfully induce dysbiosis in marmosets using a custom antibiotic cocktail (vancomycin, enrofloxacin and neomycin) administered orally for 28 days. This gut dysbiosis altered gut metabolite profiles, behavior, and stress reactivity. Increase in gut Fusobacterium spp. post-antibiotic administration was a novel dysbiotic response and has not been observed in any rodent or human studies to date. There were significant changes in concentrations of several gut metabolites which are either neurotransmitters (e.g., GABA and serotonin) or have been found to be moderators of gut-brain axis communication in rodent models (e.g., short-chain fatty acids and bile acids). There was an increase in affiliative behavior and sociability in antibiotic-administered marmosets, which might be a coping mechanism in response to gut dysbiosis-induced stress. Increase in urinary cortisol levels after multiple stressors provides more definitive proof that this model of dysbiosis may cause disrupted communication between gut and brain in common marmosets. This study is a first attempt to establish common marmosets as a novel model to study the impact of severe gut dysbiosis on gut-brain axis cross-talk and behavior.

Microbiota-Induced Epigenetic Alterations in Depressive Disorders Are Targets for Nutritional and Probiotic Therapies

Major depressive disorder (MDD) is a complex disorder and a leading cause of disability in 280 million people worldwide. Many environmental factors, such as microbes, drugs, and diet, are involved in the pathogenesis of depressive disorders. However, the underlying mechanisms of depression are complex and include the interaction of genetics with epigenetics and the host immune system. Modifications of the gut microbiome and its metabolites influence stress-related responses and social behavior in patients with depressive disorders by modulating the maturation of immune cells and neurogenesis in the brain mediated by epigenetic modifications. Here, we discuss the potential roles of a leaky gut in the development of depressive disorders via changes in gut microbiota-derived metabolites with epigenetic effects. Next, we will deliberate how altering the gut microbiome composition contributes to the development of depressive disorders via epigenetic alterations. In particular, we focus on how microbiota-derived metabolites such as butyrate as an epigenetic modifier, probiotics, maternal diet, polyphenols, drugs (e.g., antipsychotics, antidepressants, and antibiotics), and fecal microbiota transplantation could positively alleviate depressive-like behaviors by modulating the epigenetic landscape. Finally, we will discuss challenges associated with recent therapeutic approaches for depressive disorders via microbiome-related epigenetic shifts, as well as opportunities to tackle such problems.

Salivary signatures of oral-brain communication in sleep bruxers

Introduction

Microbiota and their interaction with hosts have been of great interest in brain research in recent years. However, the role of oral microbiota in mental illness and the underlying mechanism of oral-brain communication remains elusive. Sleep bruxism (SB) is an oral parafunctional activity related to the nervous system and is considered a risk factor for harmful clinical consequences and severe systemic conditions. Exploring the connection between oral microbiota and sleep bruxism may deepen our understanding of the complex relationship between oral-brain axis and provide insights for treatment.

Methods

In this study, salivary samples were collected from 22 individuals with SB and 21 healthy controls, and metagenomics with metabolomics was performed. Nonparametric Wilcoxon test were applied for the statistical analysis between the two groups. Microbial dysbiosis and altered oral metabolites were found in the SB individuals.

Results

The characteristic metabolite N-acetylglucosamine (GlcNAc) (VIP=8.4823, P<0.05) was correlated to a statistically lower Streptococcus mitis level in SB individuals. Salivary IFN-g level and IFN-g/IL-4 ratio were detected with significant changes in a chip assay. Amino acid metabolism pathways were upregulated, and the pathway with the largest number of differentially expressed genes is related to amino-tRNA charging pathway, while the most significantly enriched pathway is related to arginine biosynthesis. Neurotransmitter-associated pathways with glutamatergic and GABAergic synapses and cardiovascular system-related pathways were enriched in the SB group.

Discussion

These results indicate a possible neuroimmune regulatory network of oral-brain communication in SB, which helps explain the mechanism of the oral microbiome with the host in sleep bruxers and provides a reference for early clinical and therapeutic intervention to improve the diagnosis and treatment of SB and similar diseases.

Sweet Orange Juice Processing By-Product Extracts: A Caries Management Alternative to Chlorhexidine

Dental caries is one of the most prevalent chronic diseases globally in both children and adults. This study investigated the potential of industrial sweet orange waste extracts (ISOWE) as a substitute for chlorhexidine (CHX) in managing dental caries. First, the cytotoxicity of ISOWE (40, 80, 120 mg/mL) and CHX (0.1 and 0.2%) on buccal epithelial cells was determined. ISOWE exhibited no overall toxicity, whereas CHX strongly affected cell viability. The combination of ISOWE and CHX significantly enhanced cell proliferation compared to CHX alone. Next, the antimicrobial efficacy of ISOWE, CHX, and their combination was assessed against a 7-day complex biofilm model inoculated with oral samples from human volunteers. CHX exhibited indiscriminate antimicrobial action, affecting both pathogenic and health-associated oral microorganisms. ISOWE demonstrated lower antimicrobial efficacy than CHX but showed enhanced efficacy against pathogenic species while preserving the oral microbiome's balance. When applied to a cariogenic biofilm, the combined treatment of ISOWE with 0.1% CHX showed similar efficacy to 0.2% CHX treatment alone. Overall, the findings suggest that ISOWE is a promising natural anti-cariogenic agent with lower toxicity and enhanced selectivity for pathogenic species compared to CHX.

Salivary microbiome of healthy women of reproductive age

IMPORTANCE

The salivary microbiome has been proven to play a crucial role in local and systemic diseases. Moreover, the effects of biological and lifestyle factors such as oral hygiene and smoking on this microbial community have already been explored. However, what was not yet well understood was the natural variation of the saliva microbiome in healthy women and how this is associated with specific use of hormonal contraception and with the number of different sexual partners with whom microbiome exchange is expected regularly. In this paper, we characterized the salivary microbiome of 255 healthy women of reproductive age using an in-depth questionnaire and self-sampling kits. Using the large metadata set, we were able to investigate the associations of several host-related and lifestyle variables with the salivary microbiome profiles. Our study shows a high preservation between individuals.

Gut and oral microbiome modulate molecular and clinical markers of schizophrenia-related symptoms: A transdiagnostic, multilevel pilot study

Although increasing evidence links microbial dysbiosis with the risk for psychiatric symptoms through the microbiome-gut-brain axis (MGBA), the specific mechanisms remain poorly characterized. In a diagnostically heterogeneous group of treated psychiatric cases and nonpsychiatric controls, we characterized the gut and oral microbiome, plasma cytokines, and hippocampal inflammatory processes via proton magnetic resonance spectroscopic imaging (1H-MRSI). Using a transdiagnostic approach, these data were examined in association with schizophrenia-related symptoms measured by the Positive and Negative Syndrome Scale (PANSS). Psychiatric cases had significantly greater heterogeneity of gut alpha diversity and an enrichment of pathogenic taxa, like Veillonella and Prevotella, in the oral microbiome, which was an accurate classifier of phenotype. Cases exhibited significantly greater positive, negative, and general PANSS scores that uniquely correlated with bacterial taxa. Strong, positive correlations of bacterial taxa were also found with cytokines and hippocampal gliosis, dysmyelination, and excitatory neurotransmission. This pilot study supports the hypothesis that the MGBA influences psychiatric symptomatology in a transdiagnostic manner. The relative importance of the oral microbiome in peripheral and hippocampal inflammatory pathways was highlighted, suggesting opportunities for probiotics and oral health to diagnose and treat psychiatric conditions.

Microbiome and immuno-metabolic dysregulation in patients with major depressive disorder with atypical clinical presentation

Depression is highly prevalent (6% 1-year prevalence) and is the second leading cause of disability worldwide. Available treatment options for depression are far from optimal, with response rates only around 50%. This is most likely related to a heterogeneous clinical presentation of major depression disorder (MDD), suggesting different manifestations of underlying pathophysiological mechanisms. Poorer treatment outcomes to first-line antidepressants were reported in MDD patients endorsing an "atypical" symptom profile that is characterized by preserved reactivity in mood, increased appetite, hypersomnia, a heavy sensation in the limbs, and interpersonal rejection sensitivity. In recent years, evidence has emerged that immunometabolic biological dysregulation is an important underlying pathophysiological mechanism in depression, which maps more consistently to atypical features. In the last few years human microbial residents have emerged as a key influencing variable associated with immunometabolic dysregulations in depression. The microbiome plays a critical role in the training and development of key components of the host's innate and adaptive immune systems, while the immune system orchestrates the maintenance of key features of the host-microbe symbiosis. Moreover, by being a metabolically active ecosystem commensal microbes may have a huge impact on signaling pathways, involved in underlying mechanisms leading to atypical depressive symptoms. In this review, we discuss the interplay between the microbiome and immunometabolic imbalance in the context of atypical depressive symptoms. Although research in this field is in its infancy, targeting biological determinants in more homogeneous clinical presentations of MDD may offer new avenues for the development of novel therapeutic strategies for treatment-resistant depression.

Oral Microbiome, Mental Health, and Sleep Outcomes During the COVID-19 Pandemic: An Observational Study in Chinese and Korean American Immigrants

COVID-19 is a systemic disease whose effects are not limited to the respiratory system. The oral microbiome (OM)-brain axis is of growing interest in understanding the broader, neuropsychiatric, impacts of the COVID-19 pandemic through a systems biology lens. In this context, mental health and sleep disturbance are often reported by Asian Americans. In a cross-sectional observational study design, we examined the associations of the oral microbiome with mental health among Asian Americans during the COVID-19 pandemic (between November 2020 and April 2021). Participants (n = 20) were adult Chinese and Korean American immigrants in Atlanta, Georgia, and primarily born outside the United States (60%) with a mean age of 34.8 years ±14 (standard deviation). Participants reported depressive symptoms, anxiety, and sleep disturbance, as measured by standard questionnaires. The OM was characterized by 16S rRNA V3-V4 gene using saliva. Depressive symptoms and anxiety were reported by 60% (n = 12) of participants, whereas 35% (n = 7) reported sleep disturbance. The α-diversity was significantly associated with depressive symptoms, and marginally with anxiety. Participants with depressive symptoms and anxiety had enriched Rothia and Scardovia, respectively, whereas those without symptoms had enriched Fusobacterium. Individuals with sleep disturbance had enriched Kingella. In conclusion, this study suggests significant associations of the OM diversity with certain mental health dimensions such as depressive symptoms and anxiety. Specific taxa were associated with these symptoms. The present observations in a modest sample size suggest the possible relevance of the OM-brain axis in studies of mental health during COVID-19.

Oral microbiome changes associated with the menstrual cycle in healthy young adult females

The relationship between the menstrual cycle and the oral microbiome has not been clarified. The purpose of this study was to assess potential changes in the oral microbiome of healthy young adults using 16S rRNA-based sequencing. Eleven females (aged 23–36 years) with stable menstrual cycles and without any oral problems were recruited. Saliva samples were collected before brushing every morning during the menstrual period. Based on basal body temperatures, menstrual cycles were divided into four phases, namely the menstrual, follicular, early luteal, and late luteal phases. Our results showed that the follicular phase had a significantly higher abundance ratio of the Streptococcus genus than the early and late luteal phases, whereas the abundance ratios of the Prevotella 7 and Prevotella 6 genera were significantly lower in the follicular phase than those in the early and late luteal phases and that in the early luteal phase, respectively. Alpha diversity by the Simpson index was significantly lower in the follicular phase than that in the early luteal phase, and beta diversity showed significant differences among the four phases. Using the relative abundance data and copy numbers of the 16S rRNA genes in the samples, the bacterial amounts in the four phases were compared, and we observed that the follicular phase had significantly lower amounts of the Prevotella 7 and Prevotella 6 genera than the menstrual and early luteal phase, respectively. These results indicate reciprocal changes with the Streptococcus genus and Prevotella genera, particularly in the follicular phase. In the present study, we showed that the oral microbiome profiles are affected by the menstrual cycles of healthy young adult females.

Influence of mental health medication on microbiota in the elderly population in the Valencian region

Spain has an aging population; 19.93% of the Spanish population is over 65. Aging is accompanied by several health issues, including mental health disorders and changes in the gut microbiota. The gut-brain axis is a bidirectional network linking the central nervous system with gastrointestinal tract functions, and therefore, the gut microbiota can influence an individual’s mental health. Furthermore, aging-related physiological changes affect the gut microbiota, with differences in taxa and their associated metabolic functions between younger and older people. Here, we took a case–control approach to study the interplay between gut microbiota and mental health of elderly people. Fecal and saliva samples from 101 healthy volunteers over 65 were collected, of which 28 (EE|MH group) reported using antidepressants or medication for anxiety or insomnia at the time of sampling. The rest of the volunteers (EE|NOMH group) were the control group. 16S rRNA gene sequencing and metagenomic sequencing were applied to determine the differences between intestinal and oral microbiota. Significant differences in genera were found, specifically eight in the gut microbiota, and five in the oral microbiota. Functional analysis of fecal samples showed differences in five orthologous genes related to tryptophan metabolism, the precursor of serotonin and melatonin, and in six categories related to serine metabolism, a precursor of tryptophan. Moreover, we found 29 metabolic pathways with significant inter-group differences, including pathways regulating longevity, the dopaminergic synapse, the serotoninergic synapse, and two amino acids.

Oral microbiome variations related to ageing: possible implications beyond oral health

The global population is getting older due to a combination of longer life expectancy and declining birth rates. Growing evidence suggests that the oral microbiota composition and distribution may have a profound effect on how well we age. The purpose of this study was to investigate age-related oral microbiome variations of supragingival plaque and buccal mucosa samples in the general population in Latvia. Our results indicated significant difference between supragingival plaque bacterial profiles of three age groups (20-40; 40-60; 60 + years). Within supragingival plaque samples, age group 20-40 showed the highest bacterial diversity with a decline during the 40-60 age period and uprise again after the age of 60. Among other differences, the important oral commensal Neisseria had declined after the age of 40. Additionally, prevalence of two well-documented opportunistic pathogens Streptococcus anginosus and Gemella sanguinis gradually rose with age within our samples. Furthermore, supragingival plaque and buccal mucosa samples significantly differed in overall bacterial composition.

Microbiota-ear-brain interaction is associated with generalized anxiety disorder through activation of inflammatory cytokine responses

Introduction

Generalized anxiety disorder (GAD) is one of the most enduring anxiety disorders, being associated with increased systemic inflammation. However, the trigger and mechanisms underlying the activation of inflammatory cytokine responses in GAD remain poorly understood.

Materials and methods

We characterized the ear canal microbiome in GAD patients through 16S rRNA gene sequencing and metagenomic sequencing and identified the serum inflammatory markers in GAD patients. Spearman correlations were applied to test the relationship between the microbiota changes and systemic inflammation.

Results

Our findings showed the higher microbial diversity, accompanied with the significantly increased abundance of Proteobacteria, and decreased abundance of Firmicutes in the ear canal of GAD participants compared to that of the age- and sex-matched healthy controls (HC). Metagenomic sequencing showed that Pseudomonas aeruginosa were significantly increased at species-level in GAD patients. Furthermore, we observed the relative abundance of Pseudomonas aeruginosa was positively associated with elevated systemic inflammatory markers and the severity of disease, suggesting that these ear canal microbiota alterations might be correlated with GAD by activating the inflammatory response.

Conclusions

These findings indicate that microbiota-ear-brain interaction via upregulating inflammatory reaction involve in the development of GAD, as well as suggest that ear canal bacterial communities may be a target for therapeutic intervention.

Unlocking Modifiable Risk Factors for Alzheimer's Disease: Does the Oral Microbiome Hold Some of the Keys?

Advancing age is recognized as the primary risk factor for Alzheimer's disease (AD); however approximately one third of dementia cases are attributable to modifiable risk factors such as hypertension, diabetes, smoking, and obesity. Recent research also implicates oral health and the oral microbiome in AD risk and pathophysiology. The oral microbiome contributes to the cerebrovascular and neurodegenerative pathology of AD via the inflammatory, vascular, neurotoxic, and oxidative stress pathways of known modifiable risk factors. This review proposes a conceptual framework that integrates the emerging evidence regarding the oral microbiome with established modifiable risk factors. There are numerous mechanisms by which the oral microbiome may interact with AD pathophysiology. Microbiota have immunomodulatory functions, including the activation of systemic pro-inflammatory cytokines. This inflammation can affect the integrity of the blood-brain barrier, which in turn modulates translocation of bacteria and their metabolites to brain parenchyma. Amyloid-β is an antimicrobial peptide, a feature which may in part explain its accumulation. There are microbial interactions with cardiovascular health, glucose tolerance, physical activity, and sleep, suggesting that these modifiable lifestyle risk factors of dementia may have microbial contributors. There is mounting evidence to suggest the relevance of oral health practices and the microbiome to AD. The conceptual framework presented here additionally demonstrates the potential for the oral microbiome to comprise a mechanistic intermediary between some lifestyle risk factors and AD pathophysiology. Future clinical studies may identify specific oral microbial targets and the optimum oral health practices to reduce dementia risk.

Exercise effect on the gut microbiota in young adolescents with subthreshold depression: A randomized psychoeducation-controlled Trial

This 3-month randomized psychoeducation-controlled trial (RCT) of exercise was undertaken in young adolescents with subthreshold depression to examine the impact on gut microbiota. Participants (aged 12-14 years) were randomly assigned to an exercise or a psychoeducation-controlled group. The exercise intervention arm took moderate-intensity exercise, comprised of 30 min of running per day, 4 days a week for 3 months. Psychoeducation intervention consisted of 6 sessions of group activity including gaming, reading, and singing. The gut microbiota was assessed by metagenomic sequencing. After 3-month moderate-intensity exercise, the intervention group increased the relative abundance of Coprococcus, Blautia, Dorea, Tyzzerella at the genus level, as well as Tyzzerella nexilis, Ruminococcus obeum at species level when compared to the psychoeducation-controlled group. Moreover, EggNOG analyses showed that the defense and signal transduction mechanism were highly enriched after the active intervention, and changes were correlated with improvements in depressive symptoms measured by Chinese Patient Depression Questionnaire 9. The KEGG pathway of neurodegenerative diseases was depleted in the microbiome in young adolescents with subthreshold depression after exercise intervention. This 3-month RCT suggests that at both the genus and species levels, aerobic group exercise intervention improved in depressive symptoms and revealed changes in gut microbiota suggesting beneficial effects.

Toward a Deeper Understanding of Gut Microbiome in Depression: The Promise of Clinical Applicability

The emergence of the coronavirus disease 2019 pandemic has dramatically increased the global prevalence of depression. Unfortunately, antidepressant drugs benefit only a small minority of patients. Thus, there is an urgent need to develop new interventions. Accumulating evidence supports a causal relationship between gut microbiota dysbiosis and depression. To advance microbiota-based diagnostics and therapeutics of depression, a comprehensive overview of microbial alterations in depression is presented to identify effector microbial biomarkers. This procedure generated 215 bacterial taxa from humans and 312 from animal models. Compared to controls, depression shows significant differences in β-diversity, but no changes in microbial richness and diversity. Additionally, species-specific microbial changes are identified like increased Eggerthella in humans and decreased Acetatifactor in rodent models. Moreover, a disrupted microbiome balance and functional changes, characterized by an enrichment of pro-inflammatory bacteria (e.g., Desulfovibrio and Escherichia/Shigella) and depletion of anti-inflammatory butyrate-producing bacteria (e.g., Bifidobacterium and Faecalibacterium) are consistently shared across species. Confounding effects of geographical region, depression type, and intestinal segments are also investigated. Ultimately, a total of 178 species and subspecies probiotics are identified to alleviate the depressive phenotypes. Current findings provide a foundation for developing microbiota-based diagnostics and therapeutics and advancing microbiota-oriented precision medicine for depression.

Oral microbiota signatures in post-traumatic stress disorder (PTSD) veterans

Post-traumatic stress disorder (PTSD) represents a global public health concern, affecting about 1 in 20 individuals. The symptoms of PTSD include intrusiveness (involuntary nightmares or flashbacks), avoidance of traumatic memories, negative alterations in cognition and mood (such as negative beliefs about oneself or social detachment), increased arousal and reactivity with irritable reckless behavior, concentration problems, and sleep disturbances. PTSD is also highly comorbid with anxiety, depression, and substance abuse. To advance the field from subjective, self-reported psychological measurements to objective molecular biomarkers while considering environmental influences, we examined a unique cohort of Israeli veterans who participated in the 1982 Lebanon war. Non-invasive oral 16S RNA sequencing was correlated with psychological phenotyping. Thus, a microbiota signature (i.e., decreased levels of the bacteria sp_HMT_914, 332 and 871 and Noxia) was correlated with PTSD severity, as exemplified by intrusiveness, arousal, and reactivity, as well as additional psychopathological symptoms, including anxiety, hostility, memory difficulties, and idiopathic pain. In contrast, education duration correlated with significantly increased levels of sp_HMT_871 and decreased levels of Bacteroidetes and Firmicutes, and presented an inverted correlation with adverse psychopathological measures. Air pollution was positively correlated with PTSD symptoms, psychopathological symptoms, and microbiota composition. Arousal and reactivity symptoms were correlated with reductions in transaldolase, an enzyme controlling a major cellular energy pathway, that potentially accelerates aging. In conclusion, the newly discovered bacterial signature, whether an outcome or a consequence of PTSD, could allow for objective soldier deployment and stratification according to decreases in sp_HMT_914, 332, 871, and Noxia levels, coupled with increases in Bacteroidetes levels. These findings also raise the possibility of microbiota pathway-related non-intrusive treatments for PTSD.

Immune signaling as a node of interaction between systems that sex-specifically develop during puberty and adolescence

Adolescence is pivotal for neural and behavioral development across species. During this period, maturation occurs in several biological systems, the most well-recognized being activation of the hypothalamic-pituitary-gonadal axis marking pubertal onset. Increasing comparative studies of sex differences have enriched our understanding of systems integration during neurodevelopment. In recent years, immune signaling has emerged as a key node of interaction between a variety of biological signaling processes. Herein, we review the age- and sex-specific changes that occur in neural, hypothalamic-pituitary, and microbiome systems during adolescence. We then describe how immune signaling interacts with these systems, and review recent preclinical evidence indicating that immune signaling may play a central role in integrating changes in their typical and atypical development during adolescence. Finally, we discuss the translational relevance of these preclinical studies to human health and wellness.

Mental health and periodontal and peri-implant diseases

Mental health disorders, particularly depression and anxiety, affect a significant number of the global population. Several pathophysiological pathways for these disorders have been identified, including the hypothalamic-pituitary-adrenal axis, autonomic nervous system, and the immune system. In addition, life events, environmental factors, and lifestyle affect the onset, progression, and recurrence of mental health disorders. These may all overlap with periodontal and/or peri-implant disease. Mental health disorders are associated with more severe periodontal disease and, in some cases, poorer healing outcomes to nonsurgical periodontal therapy. They can result in behavior modification, such as poor oral hygiene practices, tobacco smoking, and alcohol abuse, which are also risk factors for periodontal disease and, therefore, may have a contributory effect. Stress has immunomodulatory effects regulating immune cell numbers and function, as well as proinflammatory cytokine production. Stress markers such as cortisol and catecholamines may modulate periodontal bacterial growth and the expression of virulence factors. Stress and some mental health disorders are accompanied by a low-grade chronic inflammation that may be involved in their relationship with periodontal disease and vice versa. Although the gut microbiome interacting with the central nervous system (gut-brain axis) is thought to play a significant role in mental illness, less is understood about the role of the oral microbiome. The evidence for mental health disorders on implant outcomes is lacking, but may mainly be through behaviourial changes. Through lack of compliance withoral hygiene and maintenance visits, peri-implant health can be affected. Increased smoking and risk of periodontal disease may also affect implant outcomes. Selective serotonin reuptake inhibitors have been linked with higher implant failure. They have an anabolic effect on bone, reducing turnover, which could account for the increased loss.

Changes in Oral Microbial Diversity in a Piglet Model of Traumatic Brain Injury

Dynamic changes in the oral microbiome have gained attention due to their potential diagnostic role in neurological diseases such as Alzheimer's disease and Parkinson's disease. Traumatic brain injury (TBI) is a leading cause of death and disability in the United States, but no studies have examined the changes in oral microbiome during the acute stage of TBI using a clinically translational pig model. Crossbred piglets (4-5 weeks old, male) underwent either a controlled cortical impact (TBI, n = 6) or sham surgery (sham, n = 6). The oral microbiome parameters were quantified from the upper and lower gingiva, both buccal mucosa, and floor of the mouth pre-surgery and 1, 3, and 7 days post-surgery (PS) using the 16S rRNA gene. Faith's phylogenetic diversity was significantly lower in the TBI piglets at 7 days PS compared to those of sham, and beta diversity at 1, 3, and 7 days PS was significantly different between TBI and sham piglets. However, no significant changes in the taxonomic composition of the oral microbiome were observed following TBI compared to sham. Further studies are needed to investigate the potential diagnostic role of the oral microbiome during the chronic stage of TBI with a larger number of subjects.

Effect of Orthodontic Appliances on the Oral Environment and Microbiome

Orthodontic treatment is an appliance-intensive endeavor, where an array of mechanical devices is used to bring about tooth movement. By virtue of remaining in close proximity to the enamel, gingiva and periodontal ligament intra-orally over a prolonged period of time, orthodontic appliances have a significant impact on the paradental tissues, oral environment and oral microbiome. Orthodontic appliances by acting as anchors for biofilm and plaque formation, accumulate bacteria and other micro-organisms in amounts unfavorable for maintenance of healthy equilibrium. The resulting loss of balance in the oral microbiome causes dysbiosis which manifests clinically as increased enamel demineralization, dental caries and periodontal disease. Mechanical removal of the accumulated plaque by maintaining rigorous oral hygiene has been proven to be the single most important factor to mitigate the harmful effects of dysbiosis. This review investigates how each of the various components of the orthodontic appliances, different types of appliances and unique surface properties of biomaterials have contributory effects at the interface of orthodontic biomaterials and oral biology. The information thus obtained will be critical in instituting the best diagnostic and therapeutic measures at the clinical level. It will also be instrumental in devising improvements and providing new directions for future research in general and precision orthodontics in particular.

The Oral Microbiota: Community Composition, Influencing Factors, Pathogenesis, and Interventions

The human oral cavity provides a habitat for oral microbial communities. The complexity of its anatomical structure, its connectivity to the outside, and its moist environment contribute to the complexity and ecological site specificity of the microbiome colonized therein. Complex endogenous and exogenous factors affect the occurrence and development of the oral microbiota, and maintain it in a dynamic balance. The dysbiotic state, in which the microbial composition is altered and the microecological balance between host and microorganisms is disturbed, can lead to oral and even systemic diseases. In this review, we discuss the current research on the composition of the oral microbiota, the factors influencing it, and its relationships with common oral diseases. We focus on the specificity of the microbiota at different niches in the oral cavity, the communities of the oral microbiome, the mycobiome, and the virome within oral biofilms, and interventions targeting oral pathogens associated with disease. With these data, we aim to extend our understanding of oral microorganisms and provide new ideas for the clinical management of infectious oral diseases.

Multi-Omics Analysis Reveals the Systematic Relationship Between Oral Homeostasis and Chronic Sleep Deprivation in Rats

Sleep disorders were associated with oral health. Inflammation has especially been thought to be a key factor in linking oral diseases and sleep deficiency. However, how chronic sleep deprivation (CSD) affects oral homeostasis, particularly oral inflammation and oral microbiota, is still unknown. This study aimed to uncover the systematic relationship between oral homeostasis and CSD in rats. The metabolomics in serum, proteomics in the tongue tissues, and microbiome analysis in the oral cavity in CSD rats were performed. Multi-omics data integration analysis was performed to uncover the systematic relationship between oral homeostasis and CSD through the weighted correlation network analysis. We found that CSD could lead to oral inflammation in rats. CSD significantly increased systemic inflammation by enhancing the serum levels of IL-1β, IL-6 and inhibiting the serum level of IL-10. Serum levels of adrenocorticotropin hormone, corticosterone, and triiodothyronine were increased in CSD rats, and the steroid hormone biosynthesis pathway was also found to be involved in the perturbation resulting from CSD, together suggesting the activation of the hypothalamic-pituitary-adrenocortical and hypothalamic‐pituitary‐thyroid axis. CSD led to changes of oral microbiota composition, and g_Acinetobacter, Candidatus Chryseobacterium massiliae, and g_Moraxella were significantly correlated with multiple proteins in bacterial invasion of epithelial cells pathway, which may partially responsible for oral inflammation resulting from CSD. The changes of proteomic profiling expression caused by CSD in tongue tissues were mainly enriched in neurodegenerative diseases pathways and immune/inflammation-related pathways. Multi-omics analysis indicated that the inflammatory response-related modules were significantly correlated with the neurodegenerative disease-related module suggesting a possible link between neurodegenerative diseases and oral inflammation. Together, CSD induced oral inflammation and subtle changes on oral microbiota. Our study is helpful to further understand the role that oral homeostasis plays in the process by which CSD affects human health and disease.

Gut Microbiota Research in Bipolar Disorder and Possible Implications for Precision Psychiatry: A Systematic Review

Bipolar disorder (BD) is a highly disabling condition with a chronic and relapsing nature. Despite the substantial socioeconomic burden associated with BD, there are still significant research gaps in risk stratification, diagnostic accuracy, and treatment selection, all key components of precision psychiatry. One possible strategy to increase the validity of precision psychiatry approaches in BD is to increase our knowledge of disorder-associated gut microbiota perturbations. To this end, we systematically reviewed the evidence on gut microbiota alterations in relation to precision psychiatry approaches on BD. We performed a systematic review on PubMed/MEDLINE and Web of Science to identify original articles investigating the possible clinical applications of microbiota analyses for pragmatic precision psychiatry in BD. A pearl growing strategy was employed to enlarge the scope of this review. The primary search strategy yielded one paper and an additional one was identified through reference tracking. The included studies were observational, with one study of good quality. The identified results justify the efforts devolved in this area of research and underscore the need to expand these investigations through additional larger and properly designed studies.

Exploring the relationship between the gut microbiome and mental health outcomes in a posttraumatic stress disorder cohort relative to trauma-exposed controls

Posttraumatic stress disorder (PTSD) imposes a significant burden on patients and communities. Although the microbiome-gut-brain axis has been proposed as a mediator or moderator of PTSD risk and persistence of symptoms, clinical data directly delineating the gut microbiome's relationship to PTSD are sparse. This study investigated associations between the gut microbiome and mental health outcomes in participants with PTSD (n = 79) and trauma-exposed controls (TECs) (n = 58). Diagnoses of PTSD, major depressive disorder (MDD), and childhood trauma were made using the Clinician-Administered PTSD Scale for DSM-5 (CAPS-5), MINI International Neuropsychiatric Interview (MINI), and Childhood Trauma Questionnaire (CTQ), respectively. Microbial communities from stool samples were profiled using 16S ribosomal RNA gene V4 amplicon sequencing and tested for associations with PTSD-related variables of interest. Random forest models identified a consortium of four genera, i.e.,  a combination of Mitsuokella, Odoribacter, Catenibacterium, and Olsenella, previously associated with periodontal disease, that could distinguish PTSD status with 66.4% accuracy. The relative abundance of this consortium was higher in the PTSD group and correlated positively with CAPS-5 and CTQ scores. MDD diagnosis was also associated with increased relative abundance of the Bacteroidetes phylum. Current use of psychotropics significantly impacted community composition and the relative abundances of several taxa. Early life trauma may prime the microbiome for changes in composition that facilitate a pro-inflammatory cascade and increase the risk of development of PTSD. Future studies should rigorously stratify participants into healthy controls, TECs, and PTSD (stratified by psychotropic drug use) to explore the role of the oral-gut-microbiome-brain axis in trauma-related disorders.

Altered Composition of the Oral Microbiota in Depression Among Cigarette Smokers: A Pilot Study

Alterations in the oral microbiota composition may influence mental health. However, linkages between compositional changes in the oral microbiota and their role in mental health among cigarette smokers remain largely unknown. In this study, we used shotgun metagenomics data for the oral microbiome of 105 participants. The data showed Bacteroidota, Fusobacteriota, Firmicutes, Proteobacteria, and Actinobacteria to be the most abundant phyla; Streptococcus, Haemophilus D, and Veillonella are the most abundant genera. Then, we clustered our subjects into avoidance and activation groups based on the behavioral activation for depression scale (BADS). Interestingly, the avoidance group exhibited a higher oral microbiome richness and diversity (alpha diversity). Differential abundance testing between BADS avoidance and activation groups showed the phyla Bacteroidota (effect size 0.5047, q = 0.0037), Campylobacterota (effect size 0.4012, q = 0.0276), Firmicutes A (effect size 0.3646, q = 0.0128), Firmicutes I (effect size 0.3581, q = 0.0268), and Fusobacteriota (effect size 0.6055, q = 0.0018) to be significantly increased in the avoidance group, but Verrucomicrobiota (effect size-0.6544, q = 0.0401), was found to be significantly decreased in the avoidance risk group. Network analysis of the 50 genera displaying the highest variation between both groups identified Campylobacter B, Centipeda, and Veillonella as hub nodes in the avoidance group. In contrast, Haemophilus and Streptococcus were identified as hub nodes in the activation group. Next, we investigated functional profiles of the oral microbiota based on BADS avoidance and activation groups and found Lysine degradations pathway was significantly enriched between both groups (ANCOM-BC, q = 0.0692). Altogether, we provide evidence for the presence of depression-related changes in the oral microbiota of smokers and possible functional contribution. The identified differences provide new information to enrich our understanding of oral microbiota-brain axis interplay and their potential impact on mental health.

A genetic association study reveals the relationship between the oral microbiome and anxiety and depression symptoms

BACKGROUND

Growing evidence supports that alterations in the gut microbiota play an essential role in the etiology of anxiety, depression, and other psychiatric disorders. However, the potential effect of oral microbiota on mental health has received little attention.

METHODS

Using the latest genome-wide association study (GWAS) summary data of the oral microbiome, polygenic risk scores (PRSs) of 285 salivary microbiomes and 309 tongue dorsum microbiomes were conducted. Logistic and linear regression models were applied to evaluate the relationship between salivary-tongue dorsum microbiome interactions with anxiety and depression. Two-sample Mendelian randomization (MR) was utilized to compute the causal effects between the oral microbiome, anxiety, and depression.

RESULTS

We observed significant salivary-tongue dorsum microbiome interactions related to anxiety and depression traits. Significantly, one common interaction was observed to be associated with both anxiety score and depression score, Centipeda periodontii SGB 224 × Granulicatella uSGB 3289 (P _{depressionscore} = 1.41 × 10^-8, P _anxietyscore = 5.10 × 10^-8). Furthermore, we detected causal effects between the oral microbiome and anxiety and depression. Importantly, we identified one salivary microbiome associated with both anxiety and depression in both the UKB database and the Finngen public database, Eggerthia (P _{IVW - majordepression - UKB} = 2.99 × 10^-6, P _{IVW - Self - reportedanxiety/panicattacks - UKB} = 3.06 × 10^-59, P _{IVW - depression - Finngen} = 3.16 × 10 , - 16 P _{IVW - anxiety - Finngen} = 1.14 × 10^-115).

CONCLUSION

This study systematically explored the relationship between the oral microbiome and anxiety and depression, which could help improve our understanding of disease pathogenesis and propose new diagnostic targets and early intervention strategies.