Association of Gut Microbial Genera with Heart Rate Variability in the General Japanese Population: The Iwaki Cross-Sectional Research Study

Multi-species probiotic supplement enhances vagal nerve function - results of a randomized controlled trial in patients with depression and healthy controls

Major depression (MD) significantly impacts individual well-being and society. The vagus nerve plays a pivotal role in the gut-brain axis, facilitating bidirectional communication between these systems. Recent meta-analyses suggest potential antidepressant effects of probiotics, although their mechanisms remain unclear. This study aimed to assess the impact of a multi-species probiotic (OMNi-BiOTiC® STRESS Repair) on vagus nerve function in 43 MD patients and 43 healthy controls (HC). Participants received either probiotics or placebo twice daily. Serum and stool samples were collected at baseline, 7 days, 28 days, and 3 months. Vagus nerve (VN) function was evaluated using 24-hour electrocardiography (ECG) for heart rate variability (HRV), alongside stool microbiome analysis via 16S rRNA sequencing. After 3 months, MD patients receiving probiotics demonstrated significantly improved morning VN function compared to HC. MD participants who were in the probiotic group showed a significant increase in Christensellales, particularly Akkermansia muciniphila along with improved sleep parameters (use of sleep medication, sleep latency) as measured by the Pittsburgh Sleep Quality Inventory (PSI). This study highlights potential physiological benefits of probiotics in MD, potentially mediated through VN stimulation. Understanding these mechanisms could lead to novel therapeutic approaches for MD management.

Improved oxygen saturation and acclimatization with bacteriotherapy at high altitude

High altitude imposes physiological stress on the human body due to reduced oxygen availability, and options to improve acclimatization are limited. Seventeen participants underwent a randomized, doubled-blinded, placebo-controlled study to test the effects of a multi-strain probiotic on acclimatization to high altitude (3,800 m). The primary outcome was oxygen saturation (SpO2) during both daytime and nighttime. Secondary measurements included acute mountain sickness (AMS) score, sleep measurements, ventilation, resting heart rate, blood pressure, heart rate variability, and fasting glucose levels. The probiotic group exhibited a higher daytime and nighttime SpO2 compared to the placebo group at high altitude. The probiotic group also exhibited a lower AMS score and enhanced acclimatization relative to the placebo group at high altitude, evidenced by higher SpO2 and lower AMS scores in treatment versus placebo groups. These results suggest bacteriotherapy as a novel, non-invasive intervention for high-altitude acclimatization.

Heart rate variability, daily cortisol indices and their association with psychometric characteristics and gut microbiota composition in an Italian community sample

The microbiota-gut-brain axis is a complex communication system that plays a crucial role in influencing various aspects of our physical and mental health. The goal of this study was to determine the extent to which individual differences in resting measures of vagally-mediated heart rate variability (HRV) and cortisol levels were associated with psychometric and specific gut microbiota characteristics in seventy-five (38 females) healthy individuals. Participants were assessed for vagally-mediated HRV, daily salivary cortisol levels, psychometric characteristics, and gut microbiota composition. Using a categorical approach based on the median split of HRV and cortisol values, we identified an association between low vagally-mediated HRV, greater depressive symptomatology, and altered gut microbiota (e.g., a higher abundance of Prevotella and a smaller abundance of Faecalibacterium, Alistipes, and Gemmiger). This suggests that vagally-mediated HRV may be a useful biomarker of microbiota-gut brain axis function, and that low vagally-mediated HRV may play an important role in the bidirectional link between gut dysbiosis and depression. On the other hand, daily cortisol parameters (e.g., cortisol awakening response, diurnal cortisol slope) were associated either with higher anxiety and perceived stress, or with a specific gut microbiota profile. Therefore, their utility as biomarkers of microbiota-gut-brain axis function needs further scrutiny.

Association of constipation with all-cause mortality among individuals with type 2 diabetes: A retrospective cohort study

BACKGROUND

Constipation is a common complication in type 2 diabetes mellitus (T2DM), yet its impact on mortality remains unclear. This study aimed to investigate the association between constipation and all-cause mortality in patients with T2DM.

METHODS

We conducted a retrospective cohort study using data from the National Health and Nutrition Examination Survey (NHANES) 2005-2010. Mortality outcomes were ascertained through linkage to National Death Index records until December 31, 2019. The association between constipation and all-cause mortality was assessed using weighted Cox proportional hazards regression models. Kaplan-Meier curves were then employed to visualize survival probabilities. Effect modification was explored through stratified analyses and interaction tests.

RESULTS

Of 1,339 participants with T2DM, 146 (10.90%) reported constipation. During a median follow-up of 10.75 years, 411 deaths occurred (57 in the constipation group, 354 in the non-constipation group). Fully adjusted weighted Cox regression analysis revealed that constipation was associated with increased all-cause mortality (HR 1.50, 95% CI 1.01-2.22, P = 0.04). Kaplan-Meier analysis demonstrated a significantly lower survival probability in patients with constipation (log-rank P < 0.05). Stratified analyses and interaction tests corroborated these findings across various subgroups.

CONCLUSIONS

Constipation is associated with elevated all-cause mortality risk in T2DM patients. These findings suggest that constipation management may be an important consideration in improving long-term outcomes for individuals with T2DM.

Biological, environmental, and psychological stress and the human gut microbiome in healthy adults

Emerging research suggests that the gut microbiome plays a crucial role in stress. We assess stress-microbiome associations in two samples of healthy adults across three stress domains (perceived stress, stressful life events, and biological stress /Respiratory Sinus Arrhythmia; RSA). Study 1 (n = 62; mean-age = 37.3 years; 68% female) and Study 2 (n = 74; mean-age = 41.6 years; female only) measured RSA during laboratory stressors and used 16S rRNA pyrosequencing to classify gut microbial composition from fecal samples. Phylogenetic Investigation of Communities by Reconstruction of Unobserved States was used to predict functional pathways of metagenomes. Results showed differences in beta diversity between high and low stressful life events groups across both studies. Study 1 revealed differences in beta diversity between high and low RSA groups. In Study 1, the low perceived stress group was higher in alpha diversity than the high perceived stress group. Levels of Clostridium were negatively associated with RSA in Study 1 and levels Escherichia/Shigella were positively associated with perceived stress in Study 2. Associations between microbial functional pathways (L-lysine production and formaldehyde absorption) and RSA are discussed. Findings suggest that certain features of the gut microbiome are differentially associated with each stress domain.

Sympathovagal quotient and resting-state functional connectivity of control networks are related to gut Ruminococcaceae abundance in healthy men

INTRODUCTION

Heart rate variability (HRV), brain resting-state functional connectivity (rsFC), and gut microbiota (GM) are three recognized indicators of health status, whose relationship has not been characterized. We aimed to identify the GM genera and families related to HRV and rsFC, the interaction effect of HRV and rsFC on GM taxa abundance, and the mediation effect of diet on these relationships.

METHODS

Eighty-eight healthy, young Colombian men were included in this cross-sectional study. HRV metrics were extracted from 24-hour Holter monitoring data and the resting functional connectivity strength (FCS) of 15 networks were derived from functional magnetic resonance imaging. Gut microbiota composition was assessed using the sequences of the V3-V4 regions of the 16 S rRNA gene, and diet was evaluated using a food frequency questionnaire. Multivariate linear regression analyses were performed to evaluate the correlations between the independent variables (HRV metrics and FCS) and the dependent variables (GM taxa abundance or alpha diversity indexes). Mediation analyses were used to test the role of diet in the relationship between HRV and GM.

RESULTS

The sympathovagal quotient (SQ) and the FCS of control networks were positively correlated with the abundance of the gut Ruminococcaceae family and an unclassified Ruminococcaceae genus (Ruminococcaceae_unc). Additionally, the interaction between the FCS of the control network and SQ reduced the individual main effects on the Ruminococcaceae_unc abundance. Finally, reduced habitual fiber intake partially mediated the relationship between SQ and this genus.

CONCLUSION

Two indicators of self-regulation, HRV and the rsFC of control networks, are related to the abundance of gut microbiota taxa in healthy men. However, only HRV is related to habitual dietary intake; thus, HRV could serve as a marker of food choice and GM composition in the future.

Revitalizing the Gut Microbiome in Chronic Kidney Disease: A Comprehensive Exploration of the Therapeutic Potential of Physical Activity

Both physical inactivity and disruptions in the gut microbiome appear to be prevalent in patients with chronic kidney disease (CKD). Engaging in physical activity could present a novel nonpharmacological strategy for enhancing the gut microbiome and mitigating the adverse effects associated with microbial dysbiosis in individuals with CKD. This narrative review explores the underlying mechanisms through which physical activity may favorably modulate microbial health, either through direct impact on the gut or through interorgan crosstalk. Also, the development of microbial dysbiosis and its interplay with physical inactivity in patients with CKD are discussed. Mechanisms and interventions through which physical activity may restore gut homeostasis in individuals with CKD are explored.

Causal impact of gut microbiota and associated metabolites on pulmonary arterial hypertension: a bidirectional Mendelian randomization study

BACKGROUND

Patients with pulmonary arterial hypertension (PAH) exhibit a distinct gut microbiota profile; however, the causal association between gut microbiota, associated metabolites, and PAH remains elusive. We aimed to investigate this causal association and to explore whether dietary patterns play a role in its regulation.

METHODS

Summary statistics of gut microbiota, associated metabolites, diet, and PAH were obtained from genome-wide association studies. The inverse variance weighted method was primarily used to measure the causal effect, with sensitivity analyses using the weighted median, weighted mode, simple mode, MR pleiotropy residual sum and outlier (MR-PRESSO), and MR-Egger methods. A reverse Mendelian randomisation analysis was also performed.

RESULTS

Alistipes (odds ratio [OR] = 2.269, 95% confidence interval [CI] 1.100-4.679, P = 0.027) and Victivallis (OR = 1.558, 95% CI 1.019-2.380, P = 0.040) were associated with an increased risk of PAH, while Coprobacter (OR = 0.585, 95% CI 0.358-0.956, P = 0.032), Erysipelotrichaceae (UCG003) (OR = 0.494, 95% CI 0.245-0.996, P = 0.049), Lachnospiraceae (UCG008) (OR = 0.596, 95% CI 0.367-0.968, P = 0.036), and Ruminococcaceae (UCG005) (OR = 0.472, 95% CI 0.231-0.962, P = 0.039) protected against PAH. No associations were observed between PAH and gut microbiota-derived metabolites (trimethylamine N-oxide [TMAO] and its precursors betaine, carnitine, and choline), short-chain fatty acids (SCFAs), or diet. Although inverse variance-weighted analysis demonstrated that elevated choline levels were correlated with an increased risk of PAH, the results were not consistent with the sensitivity analysis. Therefore, the association was considered insignificant. Reverse Mendelian randomisation analysis demonstrated that PAH had no causal impact on gut microbiota-derived metabolites but could contribute to increased the levels of Butyricicoccus and Holdemania, while decreasing the levels of Clostridium innocuum, Defluviitaleaceae UCG011, Eisenbergiella, and Ruminiclostridium 5.

CONCLUSIONS

Gut microbiota were discovered suggestive evidence of the impacts of genetically predicted abundancy of certain microbial genera on PAH. Results of our study point that the production of SCFAs or TMAO does not mediate this association, which remains to be explained mechanistically.

Gut microbiota short-chain fatty acids and their impact on the host thyroid function and diseases

Thyroid disorders are clinically characterized by alterations of L-3,5,3',5'-tetraiodothyronine (T4), L-3,5,3'-triiodothyronine (T3), and/or thyroid-stimulating hormone (TSH) levels in the blood. The most frequent thyroid disorders are hypothyroidism, hyperthyroidism, and hypothyroxinemia. These conditions affect cell differentiation, function, and metabolism. It has been reported that 40% of the world's population suffers from some type of thyroid disorder and that several factors increase susceptibility to these diseases. Among them are iodine intake, environmental contamination, smoking, certain drugs, and genetic factors. Recently, the intestinal microbiota, composed of more than trillions of microbes, has emerged as a critical player in human health, and dysbiosis has been linked to thyroid diseases. The intestinal microbiota can affect host physiology by producing metabolites derived from dietary fiber, such as short-chain fatty acids (SCFAs). SCFAs have local actions in the intestine and can affect the central nervous system and immune system. Modulation of SCFAs-producing bacteria has also been connected to metabolic diseases, such as obesity and diabetes. In this review, we discuss how alterations in the production of SCFAs due to dysbiosis in patients could be related to thyroid disorders. The studies reviewed here may be of significant interest to endocrinology researchers and medical practitioners.