Impact of the gut microbiota and associated metabolites on cardiometabolic traits, chronic diseases and human longevity: a Mendelian randomization study

Causal Associations Between Gut Microbiota, Gut Microbiota-Derived Metabolites, and Alzheimer's Disease: A Multivariable Mendelian Randomization Study

Background

Multiple studies have demonstrated that the gut microbiome is closely related to the onset of Alzheimer's disease, but the causal relationship between the gut microbiome and AD, as well as potential mediating factors, have not been fully explored.

Objective

Our aim is to validate the causal relationship between the gut microbiome and the onset of AD and determine the key mechanism by which the gut microbiome mediates AD through blood metabolites using Mendelian randomization (MR) analysis methods.

Methods

We first conducted bidirectional and mediating MR analyses using gut microbiota, blood amino acid metabolites, and AD-related single nucleotide polymorphisms as research data. In the analysis process, the inverse variance-weighted average method was mainly used as the primary method, with other methods serving as supplementary evidence.

Results

Ultimately, we found that six types of gut bacteria and two blood amino acid metabolites have a causal effect on AD. Subsequent mediation analysis proved that decreased glutamine concentration mediates the negative causal effect of Holdemanella bacteria on AD (mediation ratio of 14.5%), and increased serum alanine concentration mediates the positive causal effect of Parabacteroide bacteria on AD (mediation ratio of 9.4%).

Conclusions

Our study demonstrates the causality of Holdemanella and Parabacteroides bacteria in the onset of AD and suggests that the reduced glutamine and increased alanine serums concentration may be key nodes in mediating this effect.

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.

Structural characteristics of gut microbiota in longevity from Changshou town, Hubei, China

The gut microbiota (GM) and its potential functions play a crucial role in maintaining host health and longevity. The aim of this study was to investigate the potential relationship between GM and longevity. We collected fecal samples from 92 healthy volunteers (middle-aged and elderly: 43-79 years old; longevity: ≥ 90 years old) from Changshou Town, Zhongxiang City, Hubei, China. In addition, we collected samples from 30 healthy middle-aged and elderly controls (aged 51-70 years) from Wuhan, Hubei. The 16S rDNA V3 + V4 region of the fecal samples was sequenced using high-throughput sequencing technology. Diversity analysis results showed that the elderly group with longevity and the elderly group with low body mass index (BMI) exhibited higher α diversity. However, no significant difference was observed in β diversity. The results of the microbiome composition indicate that Firmicutes, Proteobacteria, and Bacteroidota are the core phyla in all groups. Compared to younger elderly individuals, Akkermansia and Lactobacillus are significantly enriched in the long-lived elderly group, while Megamonas is significantly reduced. In addition, a high abundance of Akkermansia is a significant characteristic of elderly populations with low BMI values. Furthermore, the functional prediction results showed that the elderly longevity group had higher abilities in short-chain fatty acid metabolism, amino acid metabolism, and xenobiotic biodegradation. Taken together, our study provides characteristic information on GM in the long-lived elderly population in Changshou Town. This study can serve as a valuable addition to the current research on age-related GM. KEY POINTS: • The gut microbiota of elderly individuals with longevity and low BMI exhibit higher alpha diversity • Gut microbiota diversity did not differ significantly between genders in the elderly population • Several potentially beneficial bacteria (e.g., Akkermansia and Lactobacillus) are enriched in long-lived individuals.

Non-traumatic osteonecrosis of the femoral head induced by steroid and alcohol exposure is associated with intestinal flora alterations and metabolomic profiles

OBJECTIVE

Osteonecrosis of the femoral head (ONFH) is a severe disease that primarily affects the middle-aged population, imposing a significant economic and social burden. Recent research has linked the progression of non-traumatic osteonecrosis of the femoral head (NONFH) to the composition of the gut microbiota. Steroids and alcohol are considered major contributing factors. However, the relationship between NONFH caused by two etiologies and the microbiota remains unclear. In this study, we examined the gut microbiota and fecal metabolic phenotypes of two groups of patients, and analyzed potential differences in the pathogenic mechanisms from both the microbial and metabolic perspectives.

METHODS

Utilizing fecal samples from 68 NONFH patients (32 steroid-induced, 36 alcohol-induced), high-throughput 16 S rDNA sequencing and liquid chromatography with tandem mass spectrometry (LC-MS/MS) metabolomics analyses were conducted. Univariate and multivariate analyses were applied to the omics data, employing linear discriminant analysis effect size to identify potential biomarkers. Additionally, functional annotation of differential metabolites and associated pathways was performed using the Kyoto Encyclopedia of Genes and Genomes (KEGG) database. Subsequently, Spearman correlation analysis was employed to assess the potential correlations between differential gut microbiota and metabolites.

RESULTS

High-throughput 16 S rDNA sequencing revealed significant gut microbial differences. At the genus level, the alcohol group had higher Lactobacillus and Roseburia, while the steroid group had more Megasphaera and Akkermansia. LC-MS/MS metabolomic analysis indicates significant differences in fecal metabolites between steroid- and alcohol-induced ONFH patients. Alcohol-induced ONFH (AONFH) showed elevated levels of L-Lysine and Oxoglutaric acid, while steroid-induced ONFH(SONFH) had increased Gluconic acid and Phosphoric acid. KEGG annotation revealed 10 pathways with metabolite differences between AONFH and SONFH patients. Correlation analysis revealed the association between differential gut flora and differential metabolites.

CONCLUSIONS

Our results suggest that hormones and alcohol can induce changes in the gut microbiota, leading to alterations in fecal metabolites. These changes, driven by different pathways, contribute to the progression of the disease. The study opens new research directions for understanding the pathogenic mechanisms of hormone- or alcohol-induced NONFH, suggesting that differentiated preventive and therapeutic approaches may be needed for NONFH caused by different triggers.

Highly crystalline cellulose microparticles from dealginated seaweed waste ameliorate high fat-sugar diet-induced hyperlipidemia in mice by modulating gut microbiota

The effects of seaweed cellulose (SC) on high fat-sugar diet (HFSD)-induced glucolipid metabolism disorders in mice and potential mechanisms were investigated. SC was isolated from dealginated residues of giant kelp (Macrocystis pyrifera), with a crystallinity index of 85.51 % and an average particle size of 678.2 nm. Administering SC to C57BL/6 mice at 250 or 500 mg/kg BW/day via intragastric gavage for six weeks apparently inhibited the development of HFSD-induced obesity, dyslipidemia, insulin resistance, oxidative stress and liver damage. Notably, SC intervention partially restored the structure and composition of the gut microbiota altered by the HFSD, substantially lowering the Firmicutes to Bacteroidetes ratio, and greatly increasing the relative abundance of Lactobacillus, Bifidobacterium, Oscillospira, Bacteroides and Akkermansia, which contributed to improved short-chain fatty acid (SCFA) production. Supplementing with a higher dose of SC led to more significant increases in total SCFA (67.57 %), acetate (64.56 %), propionate (73.52 %) and butyrate (66.23 %) concentrations in the rectal contents of HFSD-fed mice. The results indicated that highly crystalline SC microparticles could modulate gut microbiota dysbiosis and ameliorate HFSD-induced obesity and related metabolic syndrome in mice. Furthermore, particle size might have crucial impact on the prebiotic effects of cellulose as insoluble dietary fiber.

Exploring the impact of gut microbiota on abdominal aortic aneurysm risk through a bidirectional Mendelian randomization analysis

OBJECTIVE

The abdominal aortic aneurysm (AAA) is associated with alterations in the composition of the gut microbiota; however, the precise causal relationship remains unclear. Elucidating this complex interplay could provide new insights into the pathogenesis of AAA.

METHODS

A bidirectional two-sample Mendelian randomization analysis was conducted using genome-wide association study summary data on the gut microbiota (n = 18,340) and AAA (n = 353,087). A total of 196 gut microbial taxa across taxonomic levels were examined for their potential causal effects on AAA risk. Conversely, the effect of AAA on these microbial taxa was also analyzed.

RESULTS

Nine microbial taxa were identified as having a causal influence on AAA risk. Specifically, increased risk were associated with genus Bilophila (odds ratio [OR], 1.359; P = .0119), genus Catenibacterium (OR, 1.348; P = .0058), genus family XIII AD3011 group (OR, 1.507; P = .004), genus Oxalobacter (OR, 1.157; P = .0449), and genus Prevotella 7 (OR, 1.194; P = .0306), whereas decreased risks were linked to class Lentisphaeria (OR, 0.829; P = .0361), order Victivallales (OR, 0.829; P = .0361), family Victivallaceae (OR, 0.814; P = .0057), and genus Anaerotruncus (OR, 0.773; P = .0497). Furthermore, AAA was found to influence the abundance of 14 microbial taxa across various taxonomic levels. Notably, bidirectional associations were observed with the class Lentisphaeria and the order Victivallales.

CONCLUSIONS

This study provides novel evidence for a reciprocal causal relationship between gut microbiota and AAA risk, thereby offering new insights into the pathogenesis of AAA. These findings also suggest promising avenues for microbiome-based therapeutic interventions.

Association between gut microbiota and onset of type 2 diabetes mellitus: a two-sample Mendelian randomization study

Aim

Mendelian randomization (MR) analysis has been used in the exploration of the role of gut microbiota (GM) in type 2 diabetes mellitus (T2DM); however, it was limited to the genus level. This study herein aims to investigate the relationship of GM, especially at the species level, with T2DM in order to provide some evidence for further exploration of more specific GM taxa and pathway abundance in T2DM.

Methods

This two-sample MR study was based on the summary statistics of GM from the available genome-wide association study (GWAS) meta-analysis conducted by the MiBioGen consortium as well as the Dutch Microbiome Project (DMP), whereas the summary statistics of T2DM were obtained from the FinnGen consortium released data. Inverse variance weighted (IVW), MR-Egger, strength test (F), and weighted median methods were used to examine the causal association between GM and the onset of T2DM. Cochran's Q statistics was employed to quantify the heterogeneity of instrumental variables. Bonferroni's correction was conducted to correct the bias of multiple testing. We also performed reverse causality analysis.

Results

The corrected IVW estimates suggested the increased relative abundance of family Oxalobacteraceae (OR = 1.0704) and genus Oxalobacter (OR = 1.0874), respectively, were associated with higher odds of T2DM, while that of species faecis (OR = 0.9460) had a negative relationship with T2DM. The relationships of class Betaproteobacteria, family Lactobacillaceae, species finegoldii, and species longum with T2DM were also significant according to the IVW results (all P < 0.05).

Conclusions

GM had a potential causal association with T2DM, especially species faecis, finegoldii, and longum. Further studies are still needed to clarify certain results that are contradictory with previous findings.

Investigation of the causal relationship between inflammatory bowel disease and type 2 diabetes mellitus: a Mendelian randomization study

Background: Type 2 diabetes mellitus (T2DM) and inflammatory bowel disease (IBD) have been associated, according to various epidemiological research. This study uses Mendelian randomization (MR) to investigate the causal link between T2DM and IBD. Methods: To investigate the causal relationship between IBD and T2DM risk using European population data from the genome-wide association study (GWAS) summary datasets, we constructed a two-sample MR study to evaluate the genetically predicted impacts of liability towards IBD outcomes on T2DM risk. As instrumental variables (IVs), we chose 26 single nucleotide polymorphisms (SNPs) associated with IBD exposure data. The European T2DM GWAS data was obtained from the IEU OpenGWAS Project database, which contains 298,957 cases as the outcome data. The causal relationship between T2DM and IBD using a reverse MR analysis was also performed. Results: The two-sample MR analysis, with the Bonferroni adjustment for multiple testing, revealed that T2DM risk in Europeans is unaffected by their IBD liability (odds ratio (OR): 0.950-1.066, 95% confidence interval (CI): 0.885-1.019, p = 0.152-0.926). The effects of liability to T2DM on IBD were not supported by the reverse MR analysis either (OR: 0.739-1.131, 95% confidence interval (CI): 0.651-1.100, p = 0.058-0.832). MR analysis of IBS on T2DM also have no significant causal relationship (OR: 0.003-1.007, 95% confidence interval (CI): 1.013-5.791, p = 0.069-0.790). FUMA precisely mapped 22 protein-coding genes utilizing significant SNPs of T2DM acquired from GWAS. Conclusion: The MR study showed that the existing evidence did not support the significant causal effect of IBD on T2DM, nor did it support the causal impact of T2DM on IBD.

Genomics-Microbiome Based Assessment of Bidirectional Causality Between Gut Microbiota and Psoriasis

Background

Traditional observational studies have found a possible risk association of the gut microbiota for psoriasis. Meanwhile, psoriasis may also affect the changes in the gut microbiota. However, the available evidence does not demonstrate a reciprocal relationship between the gut microbiota and psoriasis. This limits our understanding on the role of the gut microbiota in the mechanisms of psoriasis.

Methods

To address this question we used Mendelian randomization, a novel epidemiological approach, and acquired the largest current gut microbiota GWAS data from the MiBioGen consortium as well as psoriasis GWAS data from the FinnGen consortium, and performed two-sample bidirectional MR analyses using a multiple MR analysis approach. Finally, the robustness of the results was assessed by sensitivity analysis.

Results

Our results indicate that five bacterial genera are causally related to psoriasis and psoriasis is causally related to four bacterial genera.

Conclusion

These results suggest a bidirectional causal influence of psoriasis on the gut microbiota. Our results somewhat challenge the causal inferences of previous observational studies. We found that the specific bacterial genera with a risk effect on psoriasis were different from those found to characterize psoriasis in previous observational studies, and that these psoriasis-characterizing genera were inversely associated with psoriasis.

Association between Gut Microbiota and Biological Aging: A Two-Sample Mendelian Randomization Study

Recent observational studies revealed an association between gut microbiota and aging, but whether gut microbiota are causally associated with the aging process remains unknown. We used a two-sample Mendelian randomization approach to investigate the causal association between gut microbiota and biological age acceleration using the largest available gut microbiota GWAS summary data from the MiBioGen consortium and GWAS data on biological age acceleration. We further conducted sensitivity analysis using MR-PRESSO, MR-Egger regression, Cochran Q test, and reverse MR analysis. Streptococcus (IVW, β = 0.16, p = 0.0001) was causally associated with Bioage acceleration. Eubacterium (rectale group) (IVW, β = 0.20, p = 0.0190), Sellimonas (IVW, β = 0.06, p = 0.019), and Lachnospira (IVW, β = -0.18, p = 0.01) were suggestive of causal associations with Bioage acceleration, with the latter being protective. Actinomyces (IVW, β = 0.26, p = 0.0083), Butyricimonas (IVW, β = 0.21, p = 0.0184), and Lachnospiraceae (FCS020 group) (IVW, β = 0.24, p = 0.0194) were suggestive of causal associations with Phenoage acceleration. This Mendelian randomization study found that Streptococcus was causally associated with Bioage acceleration. Further randomized controlled trials are needed to investigate its role in the aging process.

Mendelian randomization study supports effect of gut microflora on fractures

To investigate the possible causal relationship between intestinal microflora and fractures using Mendelian randomization (MR). A 2-sample MR study of gut microbiota and fractures was conducted using a weighted inverse variance analysis with tests for heterogeneity, horizontal pleiotropy, and sensitivity. A causal association between fracture risk and specific bacterial taxa was identified at various taxonomic levels: 2 (Bacteroidia, P = .0304; Deltaproteobacteria P = .0304) at the class level, 3 (Bacteroidales, P = .0428; Desulfovibrionales, P = .0428; Enterobacteriales, P = .0208) at the order level, 2 (FamilyXI, P = .0304; Enterobacteriaceae P = .0332) at the family level, and 1 (Alistipes, P = .0405) at the genus level. This study revealed a causal relationship between gut microflora and fracture risk, demonstrating that the effect of different flora taxa flora abundance on fracture risk differs. It provides a reference for further studies.

Genetic evidence on the causality between gut microbiota and various asthma phenotypes: a two-sample Mendelian randomization study

Introduction

Asthma is a multifarious disease that manifests in various phenotypes. Among the various factors that contribute to the development of asthma, the gut microbiota has recently emerged as a compelling area of investigation. This study aims to investigate the causal relationships between gut microbiota and distinct asthma phenotypes.

Methods

The genome-wide association study (GWAS) summary statistics for 211 gut microbial taxa were used as study exposure. Five traits pertaining to various asthma phenotypes (asthma, allergic asthma, childhood asthma, suggestive for eosinophilic asthma and obesity-related asthma) were included as study outcome. We conducted Mendelian randomization (MR) analysis and sensitivity analysis for each bacterial taxa and asthma phenotypes.

Result

We discovered a total of 58 associations that exhibited evidence of causality. Out of these, 4 associations remained significant even after applying multiple correction. An increased risk of asthma was causally associated with higher abundance of genus Holdemanella (OR = 1.11; CI: 1.05-1.17; p = 0.027), genus Oxalobacter (OR = 1.09; CI: 1.04-1.15; p = 0.025) and genus Butyricimonas (OR = 1.14; CI: 1.06-1.22; p = 0.027). Order NB1n was causally linked with an increased risk of obesity-related asthma (OR = 1.17; CI: 1.07-1.29; p = 0.015). There was limited overlap among the taxa that exhibited potential causal relationships with distinct asthma phenotypes.

Conclusion

Our research has provided genetic evidence that establishes multiple causal relationships between the gut microbiota and distinct asthma phenotypes, supporting the role of the gut microbiota in various asthma phenotypes. It is possible that different taxa play a role in the development of distinct asthma phenotypes. The causal relationships identified in this study require further investigation.

Genetically predicted basal metabolic rate and venous thromboembolism risk: a Mendelian randomization study

Background

Basal metabolic rate (BMR) is the minimum amount of energy needed by the body to carry out essential physiological functions. The goal of this study was to evaluate whether BMR causally influences venous thromboembolism (VTE) and its subtypes in European individuals.

Methods

A two-sample Mendelian randomization (MR) was performed. Within a genome-wide association study (GWAS) involving 454,874 people, genetic variants were chosen as instrumental variables based on their significant associations (p < 5 × 10-8) with BMR and their limited linkage disequilibrium (r2 < 0.001). The FinnGen project served as sources for summary statistics of VTE, encompassing different subtypes.

Results

Using the multiplicative random-effect inverse variance weighted method, our investigation revealed that one standard deviation higher BMR was associated with VTE (odds ratio [OR] = 1.684, 95% confidence interval [CI]: 1.465-1.936, p = 2.339 × 10-13), PE (OR = 1.824, 95% CI: 1.512-2.200, p = 3.399 × 10-10), and DVT of lower extremities (OR = 1.887, 95% CI: 1.562-2.280, p = 4.778 × 10-11). The consistency of these associations was observed in sensitivity analyses using various MR techniques like Mendelian randomization pleiotropy residual sum and outlier, MR-Egger, weighted median, and contamination mixture method. In addition, multivariable MR revealed direct effects of BMR on VTE and its subtypes when taking body mass index and current tobacco smoking into account.

Conclusion

Higher BMR may increase the risk of VTE and its subtypes including PE and DVT of lower extremities.

Microbiome and its implications in oncogenesis: a Mendelian randomization perspective

The human microbiome, an intricate ecological network, has garnered significant attention due to its potential implications in oncogenesis. This paper delves into the multifaceted relationships between the microbiome, its metabolites, and cancer development, emphasizing the human intestinal tract as the primary microbial habitat. Highlighting the potential causative associations between microbial disturbances and cancer progression, we underscore the role of specific bacterial strains in various cancers, such as stomach and colorectal cancer. Traditional causality assessment methods, like randomized controlled trials (RCTs), have limitations. Therefore, we advocate using Mendelian Randomization (MR) as a powerful alternative to study causal relationships, leveraging genetic variants as instrumental variables. With the proliferation of genome-wide association studies, MR harnesses genetic variations to infer causality, which is especially beneficial when addressing confounders like diet and lifestyle that can skew microbial research. We systematically review MR's application in understanding the microbiome-cancer nexus, emphasizing its strengths and challenges. While MR offers a unique perspective on causality, it faces hurdles like horizontal pleiotropy and weak instrumental variable bias. Integrating MR with multi-omics data, encompassing genomics, transcriptomics, proteomics, and metabolomics, holds promise for future research, potentially heralding groundbreaking discoveries in microbiology and genetics. This comprehensive review underscores the critical role of the human microbiome in oncogenesis and champions MR as an indispensable tool for advancing our understanding in this domain.

Genetic insights into the association of statin and newer nonstatin drug target genes with human longevity: a Mendelian randomization analysis

BACKGROUND

It remains controversial whether the long-term use of statins or newer nonstatin drugs has a positive effect on human longevity. Therefore, this study aimed to investigate the genetic associations between different lipid-lowering therapeutic gene targets and human longevity.

METHODS

Two-sample Mendelian randomization analyses were conducted. The exposures comprised genetic variants that proxy nine drug target genes mimicking lipid-lowering effects (LDLR, HMGCR, PCKS9, NPC1L1, APOB, CETP, LPL, APOC3, and ANGPTL3). Two large-scale genome-wide association study (GWAS) summary datasets of human lifespan, including up to 500,193 European individuals, were used as outcomes. The inverse-variance weighting method was applied as the main approach. Sensitivity tests were conducted to evaluate the robustness, heterogeneity, and pleiotropy of the results. Causal effects were further validated using expression quantitative trait locus (eQTL) data.

RESULTS

Genetically proxied LDLR variants, which mimic the effects of lowering low-density lipoprotein cholesterol (LDL-C), were associated with extended lifespan. This association was replicated in the validation set and was further confirmed in the eQTL summary data of blood and liver tissues. Mediation analysis revealed that the genetic mimicry of LDLR enhancement extended lifespan by reducing the risk of major coronary heart disease, accounting for 22.8% of the mediation effect. The genetically proxied CETP and APOC3 inhibitions also showed causal effects on increased life expectancy in both outcome datasets. The lipid-lowering variants of HMGCR, PCKS9, LPL, and APOB were associated with longer lifespans but did not causally increase extreme longevity. No statistical evidence was detected to support an association between NPC1L1 and lifespan.

CONCLUSION

This study suggests that LDLR is a promising genetic target for human longevity. Lipid-related gene targets, such as PCSK9, CETP, and APOC3, might potentially regulate human lifespan, thus offering promising prospects for developing newer nonstatin therapies.

Impact of intraspecific variation in insect microbiomes on host phenotype and evolution

Microbes can be an important source of phenotypic plasticity in insects. Insect physiology, behaviour, and ecology are influenced by individual variation in the microbial communities held within the insect gut, reproductive organs, bacteriome, and other tissues. It is becoming increasingly clear how important the insect microbiome is for insect fitness, expansion into novel ecological niches, and novel environments. These investigations have garnered heightened interest recently, yet a comprehensive understanding of how intraspecific variation in the assembly and function of these insect-associated microbial communities can shape the plasticity of insects is still lacking. Most research focuses on the core microbiome associated with a species of interest and ignores intraspecific variation. We argue that microbiome variation among insects can be an important driver of evolution, and we provide examples showing how such variation can influence fitness and health of insects, insect invasions, their persistence in new environments, and their responses to global environmental changes. A and B are two stages of an individual or a population of the same species. The drivers lead to a shift in the insect associated microbial community, which has consequences for the host. The complex interplay of those consequences affects insect adaptation and evolution and influences insect population resilience or invasion.

Casual effects of gut microbiota on risk of infections: a two-sample Mendelian randomization study

Background

The correlation between gut microbiota and infections has garnered significant attention in previous studies; nevertheless, our understanding of the causal relationships and mechanisms between specific microbial species and infections remains limited.

Methods

This study aimed to employ Mendelian randomization (MR) using single-nucleotide polymorphisms (SNPs) and genome-wide association study (GWAS) data of European ancestry to explore the genetic-level relationships between distinct types of gut microbiota and susceptibility to infections. Our analysis encompassed three prevalent infections: intestinal infections, pneumonia, and urinary tract infections, while concurrently examining various types of gut microbiota.

Results

We identified 18 protective gut microbiotas alongside 13 associated with increased infection risk. Particularly noteworthy are certain microbial communities capable of producing butyrate, such as the Ruminococcaceae and Lachnospiraceae families, which exhibited both favorable and unfavorable effects. Additionally, we observed a few certain communities linked to infection susceptibility, including ErysipelotrichaceaeUCG003 (OR = 0.13, 95% CI: 0.054-0.33, p = 1.24E-05), Collinsella (OR = 3.25, 95% CI: 2.00-5.27, p = 1.87E-06), and NB1n (OR = 1.24, 95% CI: 1.09-1.40, p = 1.12E-03).

Conclusion

This study reveals complex relationships between gut microbiota and various infections. Our findings could potentially offer new avenues for exploring prevention and treatment strategies for infectious diseases.

Gut microbiome causal impacts on the prognosis of breast cancer: a Mendelian randomization study

BACKGROUND

Growing evidence has shown that gut microbiome composition is associated with breast cancer (BC), but the causality remains unknown. We aimed to investigate the link between BC prognosis and the gut microbiome at various oestrogen receptor (ER) statuses.

METHODS

We performed a genome-wide association study (GWAS) to analyse the gut microbiome of BC patients, the dataset for which was collected by the Breast Cancer Association Consortium (BCAC). The analysis was executed mainly via inverse variance weighting (IVW); the Mendelian randomization (MR) results were verified by heterogeneity tests, sensitivity analysis, and pleiotropy analysis.

RESULTS

Our findings identified nine causal relationships between the gut microbiome and total BC cases, with ten and nine causal relationships between the gut microbiome and ER-negative (ER-) and ER-positive (ER+) BC, respectively. The family Ruminococcaceae and genus Parabacteroides were most apparent among the three categories. Moreover, the genus Desulfovibrio was expressed in ER- BC and total BC, whereas the genera Sellimonas, Adlercreutzia and Rikenellaceae appeared in the relationship between ER + BC and total BC.

CONCLUSION

Our MR inquiry confirmed that the gut microbiota is causally related to BC. This further explains the link between specific bacteria for prognosis of BC at different ER statuses. Considering that potential weak instrument bias impacts the findings and that the results are limited to European females due to data constraints, further validation is crucial.