Gut microbiome sheds light on the development and treatment of abdominal aortic aneurysm

Metabolomics, Genetics, and Environmental Factors: Intersecting Paths in Abdominal Aortic Aneurysm

Abdominal aortic aneurysm represents a significant public health concern, particularly in men aged 55 to 64, where it occurs in about 1%. We investigated the metabolomics and genetics of AAA by analyzing a cohort including 76 patients with AAA and randomly selected 228 controls. Utilizing the Metabolon DiscoveryHD4 platform for non-targeted metabolomics profiling, we identified several novel metabolites significantly associated with AAA. These metabolites were primarily related to environmental and lifestyle factors, notably smoking and pesticide exposure, which underscores the influence of external factors on the progression of AAA. Additionally, several genetic variants were associated with xenobiotics, highlighting a genetic predisposition that may exacerbate the effects of these environmental exposures. The integration of metabolomic and genetic data provides compelling evidence that lifestyle, environmental, and genetic factors are intricately linked to the etiology of AAA. The results of our study not only deepen the understanding of the complex pathophysiology of AAA but also pave the way for the development of targeted therapeutic strategies.

Assessing the relationships of 1,400 blood metabolites with abdominal aortic aneurysm: a Mendelian randomization study

Background

Abdominal aortic aneurysm (AAA) is one of the most dangerous types of vascular diseases worldwide. Metabolic disturbance affects disease risk and provide underlying therapeutic targets. Previous studies have reported an association between metabolic disorders and AAA. However, evidence of a causal relationship between blood metabolites and AAA is still lacking at present.

Methods

Using Mendelian randomization (MR), we assessed the causal association between 1,400 serum metabolites and AAA. The inverse variance weighted method (IVW), weighted median, MR-Egger regression, simple mode, as well as weighted mode methods were used for evaluating the causality between blood metabolites and AAA. Pleiotropy and heterogeneity tests were further conducted.

Results

Through strict screening, 17 known metabolites, 7 unknown metabolites and 5 metabolite ratios related to AAA were identified. Among all the metabolites, 24 were found to have negative associations, while 5 exhibited positive associations. The top five metabolites associated with an increased risk of AAA were Oleoyl-linoleoyl-glycerol (18:1/18:2) [2], Glycosyl-N-(2-hydroxynervonoyl)-sphingosine (d18:1/24:1(2OH)), Glycochenodeoxycholate 3-sulfate, X-21441 and X-24328. In contrast, the top five metabolites that were linked to a reduced risk of AAA included Uridine to pseudouridine ratio, Octadecanedioate, Phosphate to oleoyl-linoleoyl-glycerol (18:1 to 18:2) [2] ratio, 1-(1-enyl-palmitoyl)-GPE (p-16:0), and 1-stearoyl-GPG (18:0).

Conclusion

Among the 1,400 blood metabolites, we identified 17 known metabolites, 7 unknown metabolites, and 5 metabolite ratios associated with AAA. This MR study may provide a novel significant insight for the screening and prevention of AAA.

Impact of Reduced Saliva Production on Intestinal Integrity and Microbiome Alterations: A Sialoadenectomy Mouse Model Study

This study investigates the effect of reduced saliva production on intestinal histological structure and microbiome composition using a sialoadenectomy murine model, evaluating differences in saliva secretion, body weight, intestinal histopathological changes, and microbiome alteration using 16S rRNA gene sequencing across three groups (control, sham, and sialoadenectomy). For statistical analysis, one-way analysis of variance and multiple comparisons using Bonferroni correction were performed. p-values < 0.05 were considered statistically significant. Microbiome analysis was performed using Qiime software. The results show that reduced saliva secretion leads to structural changes in the intestinal tract, including shorter and atrophic villi, deformed Paneth cells, decreased goblet cell density, and immunohistochemical changes in epidermal growth factor and poly(ADP-ribose) polymerase-1, especially at three months after surgery. They also showed significant alterations in the intestinal microbiome, including increased Lactobacillaceae and altered populations of Ruminococcaceae and Peptostreptococcaceae, suggesting potential inflammatory responses and decreased short-chain fatty acid production. However, by 12 months after surgery, these effects appeared to be normalized, indicating potential compensatory mechanisms. Interestingly, sham-operated mice displayed favorable profiles, possibly due to immune activation from minor surgical intervention. This study underscores saliva's essential role in intestinal condition, emphasizing the "oral-gut axis" and highlighting broader implications for the relationship between oral and systemic health.

Evidence for a Role of Gut Microbiota and Probiotics in Aneurysmal Pathogenesis and Possible Therapeutics: A Systematic Review of the Literature

INTRODUCTION

Several studies investigated the implication of the gut microbiota (GM) in the formation and progression of aneurysms, suggesting a key role for GM metabolites in aneurysmal pathogenesis and prognosis.

AIM

This systematic review aims to collect key findings concerning the impact of gut bacterial compositions, GM-related metabolites, probiotics administration, and inflammatory markers in aneurysmal development and rupture.

METHODS

A PubMed, Medline, Embase, and Web of Science database search was conducted in accordance with PRISMA guidelines for systematic reviews, targeting all studies assessing the GM's role in aneurysms till 2023.

RESULTS

Data from 19 out of 292 non-duplicated studies were included. Based on the published literature, aneurysmal incidents in several locations were accompanied by an alteration in specific intestinal bacteria that may affect the prognosis of the aneurysm. The gut dysbiosis was also accompanied by modifications in the metabolic pathways. Hence, the administration of specific probiotics showed a significant implication in reversing the GM-related changes that were affecting the aneurysm, leading to a decrease in its severity, a better prognosis, and even serving as a prophylactic approach.

CONCLUSIONS

The outcomes of this review highlight the role of GM in the pathogenesis of aneurysms, assessing some involved mechanistic pathways such as gut dysbiosis, inflammation, and the alteration of gut-derived metabolites levels, which orient new research on developing therapeutic strategies.

Aortic aneurysm: pathophysiology and therapeutic options

Aortic aneurysm (AA) is an aortic disease with a high mortality rate, and other than surgery no effective preventive or therapeutic treatment have been developed. The renin-angiotensin system (RAS) is an important endocrine system that regulates vascular health. The ACE2/Ang-(1-7)/MasR axis can antagonize the adverse effects of the activation of the ACE/Ang II/AT1R axis on vascular dysfunction, atherosclerosis, and the development of aneurysms, thus providing an important therapeutic target for the prevention and treatment of AA. However, products targeting the Ang-(1-7)/MasR pathway still lack clinical validation. This review will outline the epidemiology of AA, including thoracic, abdominal, and thoracoabdominal AA, as well as current diagnostic and treatment strategies. Due to the highest incidence and most extensive research on abdominal AA (AAA), we will focus on AAA to explain the role of the RAS in its development, the protective function of Ang-(1-7)/MasR, and the mechanisms involved. We will also describe the roles of agonists and antagonists, suggest improvements in engineering and drug delivery, and provide evidence for Ang-(1-7)/MasR's clinical potential, discussing risks and solutions for clinical use. This study will enhance our understanding of AA and offer new possibilities and promising targets for therapeutic intervention.

Relationship between Gut, Blood, Aneurysm Wall and Thrombus Microbiome in Abdominal Aortic Aneurysm Patients

Previous research confirmed gut dysbiosis and translocation of selected intestinal bacteria into the vessel wall in abdominal aortic aneurysm patients. We studied the stool, blood, thrombus and aneurysm microbiomes of 21 abdominal aortic aneurysm patients using 16S rRNA sequencing. Our goals were to determine: 1. whether the microbiome characteristic of an aneurysm differs from that of a healthy vessel, 2. whether bacteria detectable in the aneurysm are translocated from the gut through the bloodstream, 3. whether the enzymatic activity of the aneurysm microbiome can contribute to the destruction of the vessel wall. The abundance of Acinetobacter, Burkholderia, Escherichia, and Sphingobium in the aneurysm samples was significantly higher than that in the microbiome of healthy vessels, but only a part of these bacteria can come from the intestine via the blood. Environmental bacteria due to the oral cavity or skin penetration route, such as Acinetobacter, Sphingobium, Enhydrobacter, and Aquabacterium, were present in the thrombus and aneurysm with a significantly higher abundance compared to the blood. Among the enzymes of the microbiome associated with the healthy vessel wall, Iron-chelate-transporting ATPase and Polar-amino-acid-transporting ATPase have protective effects. In addition, bacterial Peptidylprolyl isomerase activity found in the aneurysm has an aggravating effect on the formation of aneurysm.

Causal association between gut microbiomes and different types of aneurysms: a Mendelian randomization study

Background

Previous studies suggests that gut microbiomes are associated with the formation and progression of aneurysms. However, the causal association between them remains unclear.

Methods

A two-sample Mendelian randomization was conducted to investigate whether gut microbiomes have a causal effect on the risk of intracerebral aneurysm (IA), thoracic aortic aneurysm (TAA) and abdominal aortic aneurysm (AAA), and aortic aneurysm (AA). Single nucleotide polymorphisms (SNPs) smaller than the locus-wide significance level (1 × 10-5) were selected as instrumental variables. We used inverse-variance weighted (IVW) test as the primary method for the evaluation of causal association. MR-Egger, weighted median, weighted mode, and MR Pleiotropy Residual Sum and Outlier (MR-PRESSO) methods were conducted for sensitive analysis. The p-value was adjusted by the false discovery rate (FDR) which adjust the results of multiple comparisons, a p < 0.05 and q < 0.1 was considered a significant causal association. Additionally, a p < 0.05 and q > 0.1 was considered a suggestive causal effect. Additionally, reverse MR was also performed to exclude the possibility of reverse causality.

Results

The phylum Firmicutes (OR = 0.62; 95% CI, 0.48-0.81), class Lentisphaeria (OR = 0.75; 95% CI, 0.62-0.89), and order Victivallales (OR = 0.75; 95% CI, 0.62-0.89) have a causal protective effect on the risk of AAA. Additionally, class Verrucomicrobia, class Deltaproteobacteria, order Verrucomicrobiale, family Verrucomicrobiacea, genus Eubacterium rectale group, genus Akkermansia, and genus Clostridium innocuum group were negatively associated with the risk of different types of aneurysms, whereas class Negativicutes, order Selenomonadales, and genus Roseburia had positive causal association with different types of aneurysms (p < 0.05; q > 0.1). Further sensitivity analysis validated the robustness of our MR results, and no reverse causality was found with these gut microbiomes (p > 0.05).

Conclusion

Our MR analysis confirmed the causal association of specific gut microbiomes with AAA, and these microbiomes were considered as protective factors. Our result may provide novel insights and theoretical basis for the prevention of aneurysms through regulation of gut microbiomes.

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.

Integrated analysis of bulk RNA-seq and single-cell RNA-seq reveals the function of pyrocytosis in the pathogenesis of abdominal aortic aneurysm

Pyrocytosis is involved in the development of abdominal aortic aneurysm (AAA), we explored the pyrocytosis-related hub genes in AAA and conducted a diagnostic model based on the pyrocytosis-related genes score (PRGs). A total of 2 bulk RNA-seq (GSE57691 and GSE47472) datasets and pyrocytosis-related genes were integrated to obtain 24 pyrocytosis-related different expression genes (DEGs). The LASSO Cox regression analysis was conducted to filter out 7 genes and further establish the nomogram signature based on the PRGs that exhibited a good diagnosis value. Weighted gene co-expression network analysis (WGCNA) established 14 gene modules and further identified 6 hub genes which were involved in the regulatory process of pyrocytosis in AAA. At the single cell level, we further identified 3 immune cells were highly associated with the pyrocytosis process in AAA. Finally, the cell-cell communication demonstrated that fibroblasts and endothelial cells and myeloid cells maintained close communications. Here, we identified the dysfunctional expressed pyrocytosis-related genes and immune cells in AAA, which provide a comprehensive understanding of the pathogenesis of AAA.

Gut Microbiota and Microbial Metabolism in Early Risk of Cardiometabolic Disease

Cardiometabolic disease comprises cardiovascular and metabolic dysfunction and underlies the leading causes of morbidity and mortality, both within the United States and worldwide. Commensal microbiota are implicated in the development of cardiometabolic disease. Evidence suggests that the microbiome is relatively variable during infancy and early childhood, becoming more fixed in later childhood and adulthood. Effects of microbiota, both during early development, and in later life, may induce changes in host metabolism that modulate risk mechanisms and predispose toward the development of cardiometabolic disease. In this review, we summarize the factors that influence gut microbiome composition and function during early life and explore how changes in microbiota and microbial metabolism influence host metabolism and cardiometabolic risk throughout life. We highlight limitations in current methodology and approaches and outline state-of-the-art advances, which are improving research and building toward refined diagnosis and treatment options in microbiome-targeted therapies.