The causal effects between gut microbiota and hemorrhagic stroke: a bidirectional two-sample Mendelian randomization study

Exploring the genetic causal inference between plasma lipidome and hemorrhagic stroke

OBJECTIVES

Recent research indicates that the plasma lipidome composition may undergo alterations following hemorrhagic stroke. Nevertheless, the causal inference between plasma lipidome and hemorrhagic stroke remains elusive.

MATERIALS AND METHODS

Exposure data were achieved from a recent Genome-wide Association Study (GWAS) study of 179 lipid species involving 7174 individuals, while the outcome data were obtained from the FinnGen consortium (R10), including intracerebral hemorrhage (ICH), subarachnoid hemorrhage (SAH), and non-traumatic intracranial hemorrhage (nITH). Two-sample bidirectional Mendelian randomization (MR) analyses were used to assess the causal inference between lipidome and hemorrhagic stroke, and inverse variance weighted served as the main method. Genetic correlations between lipidome and hemorrhagic stroke were assessed using linkage disequilibrium score regression (LDSC).

RESULTS

After the false discovery rate (FDR) correction, Phosphatidylcholine (O-18:2_20:4) was identified as a substantial risk factor for ICH (OR,1.199; 95 % CI, 1.073-1.341; PFDR = 0.073). Alternatively, Phosphatidylinositol (16:0_18:1) was a relevant protective factor (OR, 0.773; 95 % CI, 0.666-0.896; PFDR = 0.069). Furthermore, the Sterol ester (27:1/20:3) (OR, 1.138; 95 % CI, 1.024-1.264; PFDR = 0.086) was identified as the prominent risk factor for SAH. Finally, Sterol ester (27:1/20:4) (OR, 1.073; 95 % CI, 1.026-1.121; PFDR = 0.030) and Phosphatidylinositol (16:0_18:1) levels (OR, 0.794; 95 % CI, 0.709-0.889; PFDR = 0.007) was identified as risk and protective factors for nITH, respectively.

CONCLUSIONS

The causal relationship between plasma lipidome and hemorrhagic stroke is evident. Studying the plasma lipidome offers promising preventive strategies and potential therapeutic approaches for hemorrhagic stroke.

Intestinal flora was associated with occurrence risk of chronic non-communicable diseases

BACKGROUND

The intestinal flora (IF) has been linked to risks of non-communicable diseases, especially various cancers, stroke, and Alzheimer's disease. However, many uncertainties of these associations during different stages of growth, development, and aging still exist. Therefore, further in-depth explorations are warranted.

AIM

To explore the associations of the human IF with disease risks during different stages of growth, development, and aging to achieve more accurate and convincing conclusions.

METHODS

Cohort, cross-sectional, case-control, and Mendelian randomization studies published in the PubMed and Web of Science databases until December 31, 2023 were systematically reviewed to clarify the associations of the IF at the genus level with the risks of various non-communicable diseases, which were grouped in accordance with the 10th revision of the International Classification of Diseases.

RESULTS

In total, 57 studies were included to quantitatively examine the influence of the IF on the risks of 30 non-communicable diseases during different stages of growth, development, and aging. Population studies and Mendelian randomization studies confirmed positive associations of the abundances of Bifidobacterium and Ruminococcus with multiple sclerosis.

CONCLUSION

These findings contribute to a deeper understanding of the roles of the IF and provide novel evidence for effective strategies for the prevention and treatment of non-communicable diseases. In the future, it will be necessary to explore a greater variety of research techniques to uncover the specific mechanisms by which gut microbiota trigger diseases and conduct in-depth studies on the temporal relationship between microbiota alterations and diseases, so as to clarify the causal relationship more accurately.

Gut microbiota dysbiosis and neurological function recovery after intracerebral hemorrhage: an analysis of clinical samples

We aimed to investigate the microbial community composition in patients with intracerebral hemorrhage (ICH) and its effect on prognosis. We designed two clinical cohort studies to explore the gut dysbiosis after ICH and their relationship with neurological function prognosis. First, fecal samples from patients with ICH at three time points: T1 (within 24 h of admission), T2 (3 days after surgery), and T3 (7 days after surgery), and healthy volunteers were subjected to 16S rRNA sequencing using Illumina high-throughput sequencing technology. When differential gut microbiota was identified, the correlation between clinical indicators and microbiotas was analyzed. Subsequently, the patients with ICH were categorized into GOOD and POOR groups based on their Glasgow Outcome Scale Extended (GOS-E) score, and the disparities in gut microbiota between the two groups were assessed. Univariate and multivariate logistic regression analyses were performed to identify independent risk factors. The composition and diversity of the gut microbiota in patients with ICH were different from those in the control group and changed dynamically with the extension of the course of cerebral hemorrhage. The abundances of Enterococcaceae, Clostridiales incertae sedis XI, and Peptoniphilaceae were significantly increased in patients with ICH, whereas Bacteroidaceae, Ruminococcaceae, Lachnospiraceae, and Veillonellaceae were significantly reduced. The relative abundance of Enterococcus gradually increased with the extension of the duration of ICH after surgery, and the abundance of Bacteroides gradually decreased. The abundance of Enterococcus before surgery was found to be negatively associated with patient neurological function prognosis. The original ICH score and Lachnospiraceae status were independent risk factors for predicting the prognosis of neurological function in patients with ICH (P < 0.05). Changes in the gut microbiota diversity in patients with ICH were related to prognosis. Lachnospiraceae may have a protective effect on prognosis.IMPORTANCEAcute central nervous system injuries like hemorrhagic stroke are major global health issues. While surgical hematoma removal can alleviate brain damage, severe cases still have a high 1-month mortality rate of up to 40%. Gut microbiota significantly impacts health, and treatments like fecal microbiota transplantation (FMT) and probiotics can improve brain damage by correcting gut microbiota imbalances caused by ischemic stroke. However, few clinical studies have explored this relationship in hemorrhagic stroke. This study investigated the impact of cerebral hemorrhage on the composition of gut microbiota, and we found that Lachnospiraceae were the independent risk factors for poor prognosis in intracerebral hemorrhage (ICH). The findings offer potential insights for the application of FMT in patients with ICH, and it may improve the prognosis of patients.

Patients' Characteristics Associated With Size of Ruptured and Unruptured Intracranial Aneurysms

OBJECTIVE

The size of unruptured intracranial aneurysms (UIA) remains the most crucial risk factor for treatment decisions. On the other side, there is a non-negligible portion of small ruptured IA and large stable UIA. This study aimed to identify the patients' characteristics related to IA size in the context of IA rupture status.

METHODS

A total of 2152 patients, with 1002 being hospitalized for an acute aneurysmal subarachnoid hemorrhage (SAH), were included from our institutional IA database. Different demographic and clinical characteristics of patients and IA were collected. IA size was the study endpoint, assessed as continuous variable in univariate and multivariable linear regression analysis, separately for ruptured (R) IA and UIA.

RESULTS

The mean IA size was 8.3 and 7.3 mm in the UIA and RIA subpopulations, respectively. Higher age (p = 0.003) and baseline blood urea level (p < 0.001) were independently associated with increasing UIA size. In contrast, location at the posterior circulation (p < 0.001), familiar intracranial aneurysms (p < 0.001), serum potassium (p = 0.006), and total serum protein (p = 0.019) were related to smaller UIA size in the multivariate analysis. For RIA, a statistically significant and independent association was detected for location (p = 0.019), history of gastrointestinal diseases (p = 0.042), and levothyroxine intake (p = 0.002).

CONCLUSIONS

Identification of clinical characteristics related to the size of ruptured and unruptured IA allows a more differentiated view on the genesis of RIA and UIA and the value of sack size as a basis for therapeutic decision-making. More research is needed to verify the identified risk factors.

Causal associations of gut microbiota and pulmonary tuberculosis: a two-sample Mendelian randomization study

Background

The prevalence of pulmonary tuberculosis (PTB) as an infectious disease continues to contribute significantly to global mortality. According to recent studies, the gut microbiota of PTB patients and healthy controls (HCs) show significant disparities. However, the causal relationship between them has yet to be elucidated.

Methods

We conducted a study using Mendelian Randomization (MR) to explore the potential causal link between gut microbiota and pulmonary tuberculosis (PTB). The summary statistics of the gut microbiota were acquired from the MiBioGen consortium, while data on PTB were sourced from pheweb.jp. A range of statistical methodologies were employed to evaluate causality, encompassing inverse variance weighting (IVW), MR-Egger, weighted median (WM), weighted model, and simple model. We utilized instrumental variables (IVs) that have a direct causal relationship with PTB to annotate SNPs, aiming to discover the genes harboring these genetic variants and uncover potential associations between host genes and the microbiome in patients with PTB.

Results

Among the 196 bacterial traits in the gut microbiome, we have identified a total of three microbiomes that exhibit a significant association with PTB. The occurrence of Dorea (P = 0.0458, FDR-adjusted P = 0.0458) and Parasutterella (P = 0.0056, FDR-adjusted P = 0.0168) was linked to an elevated risk of PTB, while the presence of Lachnoclostridium (P = 0.0347, FDR-adjusted P = 0.0520) demonstrated a protective effect against PTB. Our reverse Two-Sample Mendelian Randomization (TSMR) analysis did not yield any evidence supporting the hypothesis of reverse causality from PTB to alterations in the intestinal flora.

Conclusion

We have established a connection between the gut microbiota and PTB through gene prediction analysis, supporting the use of gut microecological therapy in managing PTB and paving the way for further understanding of how gut microbiota contributes to PTB's development.

Irisin alleviated the reproductive endocrinal disorders of PCOS mice accompanied by changes in gut microbiota and metabolomic characteristics

Introduction

Folliculogenesis and oligo/anovulation are common pathophysiological characteristics in polycystic ovary syndrome (PCOS) patients, and it is also accompanied by gut microbiota dysbiosis. It is known that physical activity has beneficial effects on improving metabolism and promoting ovulation and menstrual cycle disorder in PCOS patients, and it can also modulate the gastrointestinal microbiota in human beings. However, the mechanism remains vague. Irisin, a novel myokine, plays a positive role in the mediating effects of physical activity.

Methods

Mice were randomly divided into the control group, PCOS group and PCOS+irisin group. PCOS model was induced by dehydroepiandrosterone (DHEA) and high-fat diet (HFD). The PCOS+irisin group was given irisin 400μg/kg intraperitoneal injection every other day for 21 days. The serum sex hormones were measured by radioimmunoassay. Hematoxylin and Eosin (H&E) Staining and immunohistochemistry (IHC) were conducted on ovarian tissue. The feces microbiota and metabolomic characteristics were collected by 16S rRNA gene sequencing and liquid chromatography-mass spectrometry (LC-MS).

Results

In this study, we demonstrated that irisin supplementation alleviated reproductive endocrine disorders of PCOS mice, including estrous cycle disturbance, ovarian polycystic degeneration, and hyperandrogenemia. Irisin also improved the PCOS follicles dysplasia and ovulation disorders, while it had no significant effect on the quality of oocytes. Moreover, irisin could mitigate the decreased bacteria of Odoribacter and the increased bacteria of Eisenbergiella and Dubosiella in PCOS mice model. Moreover, irisin could alleviate the increased fecal metabolites: Methallenestril and PS (22:5(4Z,7Z,10Z,13Z,16Z)/ LTE4).

Conclusion

These results suggest that irisin may alleviate the status of PCOS mice model by modulating androgen-induced gut microbiota dysbiosis and fecal metabolites. Hence, our study provided evidence that irisin may be considered as a promising strategy for the treatment of PCOS.

Anorexia nervosa and bulimia nervosa: a Mendelian randomization study of gut microbiota

Background

Anorexia nervosa (AN) and bulimia nervosa (BN) poses a significant challenge to global public health. Despite extensive research, conclusive evidence regarding the association between gut microbes and the risk of AN and BN remains elusive. Mendelian randomization (MR) methods offer a promising avenue for elucidating potential causal relationships.

Materials and methods

Genome-wide association studies (GWAS) datasets of AN and BN were retrieved from the OpenGWAS database for analysis. Independent single nucleotide polymorphisms closely associated with 196 gut bacterial taxa from the MiBioGen consortium were identified as instrumental variables. MR analysis was conducted utilizing R software, with outlier exclusion performed using the MR-PRESSO method. Causal effect estimation was undertaken employing four methods, including Inverse variance weighted. Sensitivity analysis, heterogeneity analysis, horizontal multivariate analysis, and assessment of causal directionality were carried out to assess the robustness of the findings.

Results

A total of 196 bacterial taxa spanning six taxonomic levels were subjected to analysis. Nine taxa demonstrating potential causal relationships with AN were identified. Among these, five taxa, including Peptostreptococcaceae, were implicated as exerting a causal effect on AN risk, while four taxa, including Gammaproteobacteria, were associated with a reduced risk of AN. Similarly, nine taxa exhibiting potential causal relationships with BN were identified. Of these, six taxa, including Clostridiales, were identified as risk factors for increased BN risk, while three taxa, including Oxalobacteraceae, were deemed protective factors. Lachnospiraceae emerged as a common influence on both AN and BN, albeit with opposing effects. No evidence of heterogeneity or horizontal pleiotropy was detected for significant estimates.

Conclusion

Through MR analysis, we revealed the potential causal role of 18 intestinal bacterial taxa in AN and BN, including Lachnospiraceae. It provides new insights into the mechanistic basis and intervention targets of gut microbiota-mediated AN and BN.

Effect of the gut microbiome, plasma metabolome, peripheral cells, and inflammatory cytokines on obesity: a bidirectional two-sample Mendelian randomization study and mediation analysis

Background

Obesity is a metabolic and chronic inflammatory disease involving genetic and environmental factors. This study aimed to investigate the causal relationship among gut microbiota abundance, plasma metabolomics, peripheral cell (blood and immune cell) counts, inflammatory cytokines, and obesity.

Methods

Summary statistics of 191 gut microbiota traits (N = 18,340), 1,400 plasma metabolite traits (N = 8,299), 128 peripheral cell counts (blood cells, N = 408,112; immune cells, N = 3,757), 41 inflammatory cytokine traits (N = 8,293), and 6 obesity traits were obtained from publicly available genome-wide association studies. Two-sample Mendelian randomization (MR) analysis was applied to infer the causal links using inverse variance-weighted, maximum likelihood, MR-Egger, weighted median, weighted mode, and Wald ratio methods. Several sensitivity analyses were also utilized to ensure reliable MR results. Finally, we used mediation analysis to identify the pathway from gut microbiota to obesity mediated by plasma metabolites, peripheral cells, and inflammatory cytokines.

Results

MR revealed a causal effect of 44 gut microbiota taxa, 281 plasma metabolites, 27 peripheral cells, and 8 inflammatory cytokines on obesity. Among them, five shared causal gut microbiota taxa belonged to the phylum Actinobacteria, order Bifidobacteriales, family Bifidobacteriaceae, genus Lachnospiraceae UCG008, and species Eubacterium nodatum group. Furthermore, we screened 42 shared causal metabolites, 7 shared causal peripheral cells, and 1 shared causal inflammatory cytokine. Based on known causal metabolites, we observed that the metabolic pathways of D-arginine, D-ornithine, linoleic acid, and glycerophospholipid metabolism were closely related to obesity. Finally, mediation analysis revealed 20 mediation relationships, including the causal pathway from gut microbiota to obesity, mediated by 17 metabolites, 2 peripheral cells, and 1 inflammatory cytokine. Sensitivity analysis represented no heterogeneity or pleiotropy in this study.

Conclusion

Our findings support a causal relationship among gut microbiota, plasma metabolites, peripheral cells, inflammatory cytokines, and obesity. These biomarkers provide new insights into the mechanisms underlying obesity and contribute to its prevention, diagnosis, and treatment.