Metformin Inhibits Abdominal Aortic Aneurysm Formation through the Activation of the AMPK/mTOR Signaling Pathway

Medical treatments for abdominal aortic aneurysm: an overview of clinical trials

INTRODUCTION

Abdominal aortic aneurysm is a progressive, segmental, abdominal aortic dilation associated with a high mortality rate. Abdominal aortic aneurysms with diameters larger than 55 mm are associated with a high risk of rupture, and the most effective treatment options are surgical repair. Close observation and lifestyle adjustments are recommended for smaller abdominal aortic aneurysms with lower rupture risk. The development of medical therapies that limit or prevent the progression, expansion, and eventual rupture of abdominal aortic aneurysms remains an unmet clinical need.

AREAS COVERED

This review provides an overview of completed and ongoing clinical trials examining the efficacies of various drug classes, including antibiotics, antihypertensive drugs, hypolipidemic drugs, hypoglycemic drugs, and other potential therapies for abdominal aortic aneurysms. A search of PubMed, Web of Science, Clinical Trials, and another six clinical trial registries was conducted in January 2024.

EXPERT OPINION

None of the drugs have enough evidence to indicate that they can effectively inhibit the dilation of abdominal aortic aneurysm. More clinical trial data is required to support the efficacy of propranolol. Future research should also explore different drug delivery mechanisms, such as nanoparticles, to elevate drug concentration at the aneurysm wall.

Association of metformin use with abdominal aortic aneurysm: A systematic review and meta-analysis

BACKGROUND

Abdominal aortic aneurysm (AAA) is a cardiovascular disease characterized by a high mortality rate when ruptured. Some studies suggest a potential inverse correlation between AAA and diabetes patients, especially those undergoing metformin treatment. However, this relationship remains unclear. This paper offers a systematic review and meta-analysis with the objective of clarifying the influence of metformin on AAA.

METHODS

A search for relevant articles was performed across multiple databases including PubMed, ScienceDirect, Cochrane and Scopus. The focus was on studies that examined the comparative effects of metformin and non-metformin treatments on AAA patients. Data from appropriate studies were consolidated to estimate the effects. Our study encompassed 11 articles, comprising 13 cohorts that compared metformin (n = 32,250) with a control group (n = 116,339).

RESULTS

The random effects meta-analysis revealed that metformin was associated with a slower growth rate (weighted mean difference (WMD) -0.86 mm; 95% CI: -1.21 to -0.52; p < 0.01; I2: 81.4%) and fewer AAA-related events (OR: 0.54; 95% CI: 0.34 to 0.86; p = 0.01; I2: 60.9%). The findings suggest that metformin may be linked to a reduced risk of aortic aneurysm. A meta-regression analysis indicated that the association between metformin and AAA growth was significantly influenced by male gender (p = 0.027), but not by age (p = 0.801), hypertension (p = 0.256), DM (p = 0.689), smoking history (p = 0.786), use of lipid-lowering agents (p = 0.715), or baseline diameter (p = 0.291).

CONCLUSION

These results hint at a potential role for metformin in limiting annual AAA growth, AAA-related events, and the risk of AAA.

Unveiling the dual role of autophagy in vascular remodelling and its related diseases

Vascular remodelling is an adaptive response to physiological and pathological stimuli that leads to structural and functional changes in the vascular intima, media, and adventitia. Pathological vascular remodelling is a hallmark feature of numerous vascular diseases, including atherosclerosis, hypertension, abdominal aortic aneurysm, pulmonary hypertension and preeclampsia. Autophagy is critical in maintaining cellular homeostasis, and its dysregulation has been implicated in the pathogenesis of various diseases, including vascular diseases. However, despite emerging evidence, the role of autophagy and its dual effects on vascular remodelling has garnered limited attention. Autophagy can exert protective and detrimental effects on the vascular intima, media and adventitia, thereby substantially influencing the course of vascular remodelling and its related vascular diseases. Currently, there has not been a review that thoroughly describes the regulation of autophagy in vascular remodelling and its impact on related diseases. Therefore, this review aimed to bridge this gap by focusing on the regulatory roles of autophagy in diseases related to vascular remodelling. This review also summarizes recent advancements in therapeutic agents targeting autophagy to regulate vascular remodelling. Additionally, this review offers an overview of recent breakthroughs in therapeutic agents targeting autophagy to regulate vascular remodelling. A deeper understanding of how autophagy orchestrates vascular remodelling can drive the development of targeted therapies for vascular diseases.

Dexmedetomidine Alleviates Abdominal Aortic Aneurysm by Activating Autophagy Via AMPK/mTOR Pathway

BACKGROUND

Abdominal aortic aneurysms (AAA) are a critical global health issue with increasing prevalence. Dexmedetomidine (DEX) is a highly selective α2-adrenoceptor agonist that has previously been shown to play a protective role in AAA. Nevertheless, the mechanisms underlying its protection effect remain not fully understood.

METHODS

A rat AAA model was established via intra-aortic porcine pancreatic elastase perfusion with or without DEX administration. The abdominal aortic diameters of rats were measured. Hematoxylin-eosin and Elastica van Gieson staining were conducted for histopathological observation. TUNEL and immunofluorescence staining were utilized to detect cell apoptosis and α-SMA/LC3 expression in the abdominal aortas. Protein levels were determined using western blotting.

RESULTS

DEX administration repressed the dilation of aortas, alleviated pathological damage and cell apoptosis, and suppressed phenotype switching of vascular smooth muscle cells (VSMCs). Moreover, DEX activated autophagy and regulated the AMP-activated protein kinase/mammalian target of the rapamycin (AMPK/mTOR) signaling pathway in AAA rats. Administration of the AMPK inhibitor attenuated the DEX-mediated ameliorative effects on AAA in rats.

CONCLUSION

DEX ameliorates AAA in rat models by activating autophagy via the AMPK/mTOR pathway.

Pathogenesis and management of abdominal aortic aneurysm

Abdominal aortic aneurysm (AAA) causes ∼170 000 deaths annually worldwide. Most guidelines recommend asymptomatic small AAAs (30 to <50 mm in women; 30 to <55 mm in men) are monitored by imaging and large asymptomatic, symptomatic, and ruptured AAAs are considered for surgical repair. Advances in AAA repair techniques have occurred, but a remaining priority is therapies to limit AAA growth and rupture. This review outlines research on AAA pathogenesis and therapies to limit AAA growth. Genome-wide association studies have identified novel drug targets, e.g. interleukin-6 blockade. Mendelian randomization analyses suggest that treatments to reduce low-density lipoprotein cholesterol such as proprotein convertase subtilisin/kexin type 9 inhibitors and smoking reduction or cessation are also treatment targets. Thirteen placebo-controlled randomized trials have tested whether a range of antibiotics, blood pressure-lowering drugs, a mast cell stabilizer, an anti-platelet drug, or fenofibrate slow AAA growth. None of these trials have shown convincing evidence of drug efficacy and have been limited by small sample sizes, limited drug adherence, poor participant retention, and over-optimistic AAA growth reduction targets. Data from some large observational cohorts suggest that blood pressure reduction, particularly by angiotensin-converting enzyme inhibitors, could limit aneurysm rupture, but this has not been evaluated in randomized trials. Some observational studies suggest metformin may limit AAA growth, and this is currently being tested in randomized trials. In conclusion, no drug therapy has been shown to convincingly limit AAA growth in randomized controlled trials. Further large prospective studies on other targets are needed.

Mechanisms and efficacy of metformin-mediated suppression of established experimental abdominal aortic aneurysms

Objective

Metformin treatment attenuates experimental abdominal aortic aneurysm (AAA) formation, as well as reduces clinical AAA diameter enlargement in patients with diabetes. The mechanisms of metformin-mediated aneurysm suppression, and its efficacy in suppressing established experimental aneurysms, remain uncertain.

Methods

Experimental AAAs were created in male C57BL/6J mice via intra-aortic infusion of porcine pancreatic elastase. Metformin alone (250 mg/kg), or metformin combined with the 5' AMP-activated protein kinase (AMPK) antagonist Compound C (10 mg/kg), were administered to respective mouse cohorts daily beginning 4 days following AAA induction. Further AAA cohorts received either the AMPK agonist AICA riboside (500 mg/kg) as positive, or vehicle (saline) as negative, controls. AAA progression in all groups was assessed via serial in vivo ultrasonography and histopathology at sacrifice. Cytokine-producing T cells and myeloid cellularity were determined by flow cytometric analyses.

Results

Metformin limited established experimental AAA progression at 3 (-85%) and 10 (-68%) days following treatment initiation compared with saline control. Concurrent Compound C treatment reduced this effect by approximately 50%. In metformin-treated mice, reduced AAA progression was associated with relative elastin preservation, smooth muscle cell preservation, and reduced mural leukocyte infiltration and neoangiogenesis compared with vehicle control group. Metformin also resulted in reduced interferon-γ-, but not interleukin-10 or -17, producing splenic T cells in aneurysmal mice. Additionally, metformin therapy increased circulating and splenic inflammatory monocytes (CD11b⁺Ly-6C^high), but not neutrophils (CD11b⁺Ly-6G⁺), with no effect on respective bone marrow cell populations.

Conclusions

Metformin treatment suppresses existing experimental AAA progression in part via AMPK agonist activity, limiting interferon-γ-producing T cell differentiation while enhancing circulating and splenic inflammatory monocyte retention.

Protection of diabetes in aortic abdominal aneurysm: Are antidiabetics the real effectors?

Aortic aneurysms, including abdominal aortic aneurysms (AAAs), is the second most prevalent aortic disease and represents an important cause of death worldwide. AAA is a permanent dilation of the aorta on its infrarenal portion, pathologically associated with oxidative stress, proteolysis, vascular smooth muscle cell loss, immune-inflammation, and extracellular matrix remodeling and degradation. Most epidemiological studies have shown a potential protective role of diabetes mellitus (DM) on the prevalence and incidence of AAA. The effect of DM on AAA might be explained mainly by two factors: hyperglycemia [or other DM-related factors such as insulin resistance (IR)] and/or by the effect of prescribed DM drugs, which may have a direct or indirect effect on the formation and progression of AAAs. However, recent studies further support that the protective role of DM in AAA may be attributable to antidiabetic therapies (i.e.: metformin or SGLT-2 inhibitors). This review summarizes current literature on the relationship between DM and the incidence, progression, and rupture of AAAs, and discusses the potential cellular and molecular pathways that may be involved in its vascular effects. Besides, we provide a summary of current antidiabetic therapies which use could be beneficial for AAA.

Dietary therapy in abdominal aortic aneurysm - Insights from clinical and experimental studies

Abdominal aortic aneurysm (AAA) is a prevalent vascular disease with high mortality rates upon rupture. Despite its prevalence in elderly populations, there remain limited treatment options; invasive surgical repair, while risky, is the only therapeutic intervention with proven clinical benefits. Dietary factors have long been suggested to be closely associated with AAA risks, and dietary therapies recently emerged as promising avenues to achieve non-invasive management of a wide spectrum of diseases. However, the role of dietary therapies in AAA remains elusive. In this article, we will summarize the recent clinical and pre-clinical efforts in understanding the therapeutic and mechanistic implications of various dietary patterns and therapeutic approaches in AAA.

Development of pharmacotherapies for abdominal aortic aneurysms

The cardiovascular field is still searching for a treatment for abdominal aortic aneurysms (AAA). This inflammatory disease often goes undiagnosed until a late stage and associated rupture has a high mortality rate. No pharmacological treatment options are available. Three hallmark factors of AAA pathology include inflammation, extracellular matrix remodeling, and vascular smooth muscle dysfunction. Here we discuss drugs for AAA treatment that have been studied in clinical trials by examining the drug targets and data present for each drug's ability to regulate the aforementioned three hallmark pathways in AAA progression. Historically, drugs that were examined in interventional clinical trials for treatment of AAA were repurposed therapeutics. Novel treatments (biologics, small-molecule compounds etc.) have not been able to reach the clinic, stalling out in pre-clinical studies. Here we discuss the backgrounds of previous investigational drugs in hopes of better informing future development of potential therapeutics. Overall, the highlighted themes discussed here stress the importance of both centralized anti-inflammatory drug targets and rigor of translatability. Exceedingly few murine studies have examined an intervention-based drug treatment in halting further growth of an established AAA despite interventional treatment being the therapeutic approach taken to treat AAA in a clinical setting. Additionally, data suggest that a potentially successful drug target may be a central inflammatory biomarker. Specifically, one that can effectively modulate all three hallmark factors of AAA formation, not just inflammation. It is suggested that inhibiting PGE₂ formation with an mPGES-1 inhibitor is a leading drug target for AAA treatment to this end.

N1-Methyladenosine (m1A) Regulation Associated With the Pathogenesis of Abdominal Aortic Aneurysm Through YTHDF3 Modulating Macrophage Polarization

Objectives

This study aimed to identify key AAA-related m1A RNA methylation regulators and their association with immune infiltration in AAA. Furthermore, we aimed to explore the mechanism that m1A regulators modulate the functions of certain immune cells as well as the downstream target genes, participating in the progression of AAA.

Methods

Based on the gene expression profiles of the GSE47472 and GSE98278 datasets, differential expression analysis focusing on m1A regulators was performed on the combined dataset to identify differentially expressed m1A regulatory genes (DEMRGs). Additionally, CIBERSORT tool was utilized in the analysis of the immune infiltration landscape and its correlation with DEMRGs. Moreover, we validated the expression levels of DEMRGs in human AAA tissues by real-time quantitative PCR (RT-qPCR). Immunofluorescence (IF) staining was also applied in the validation of cellular localization of YTHDF3 in AAA tissues. Furthermore, we established LPS/IFN-γ induced M1 macrophages and ythdf3 knockdown macrophages in vitro, to explore the relationship between YTHDF3 and macrophage polarization. At last, RNA immunoprecipitation-sequencing (RIP-Seq) combined with PPI network analysis was used to predict the target genes of YTHDF3 in AAA progression.

Results

Eight DEMRGs were identified in our study, including YTHDC1, YTHDF1-3, RRP8, TRMT61A as up-regulated genes and FTO, ALKBH1 as down-regulated genes. The immune infiltration analysis showed these DEMRGs were positively correlated with activated mast cells, plasma cells and M1 macrophages in AAA. RT-qPCR analysis also verified the up-regulated expression levels of YTHDC1, YTHDF1, and YTHDF3 in human AAA tissues. Besides, IF staining result in AAA adventitia indicated the localization of YTHDF3 in macrophages. Moreover, our in-vitro experiments found that the knockdown of ythdf3 in M0 macrophages inhibits macrophage M1 polarization but promotes macrophage M2 polarization. Eventually, 30 key AAA-related target genes of YTHDF3 were predicted, including CD44, mTOR, ITGB1, STAT3, etc.

Conclusion

Our study reveals that m1A regulation is significantly associated with the pathogenesis of human AAA. The m1A “reader,” YTHDF3, may participate in the modulating of macrophage polarization that promotes aortic inflammation, and influence AAA progression by regulating the expression of its target genes.

Dapagliflozin Ameliorates the Formation and Progression of Experimental Abdominal Aortic Aneurysms by Reducing Aortic Inflammation in Mice

Background. Dapagliflozin, a sodium glucose transporter protein-2 (SGLT-2) inhibitor, reduces the risk for cardiovascular diseases. However, the influence of dapagliflozin on nondissecting abdominal aortic aneurysms (AAAs) remains unclear. Methods. AAAs were created in male C57BL/6 mice via intra-aortic porcine pancreatic elastase (PPE) infusion. Mice were daily treated with dapagliflozin (1 or 5 mg/kg body weight) or an equal volume of vehicle through oral gavage beginning one day prior to PPE infusion for 14 days. To investigate its translational value, dapagliflozin or vehicle was also administered to mice with existing AAAs in another cohort. Aortic diameters were measured prior to (day 0 for baseline) and 14 days after PPE infusion. After sacrifice, mice aortae were collected, and following histological analyses were performed. Results. Dapagliflozin treatment significantly reduced aneurysmal aortic expansion following PPE infusion as compared to vehicle treatment especially at 5 mg/kg body weight (approximately 21% and 33% decreases in 1 and 5 mg/kg treatment groups, respectively). The dose-dependent attenuation of AAAs by dapagliflozin was also confirmed on histological analyses. Dapagliflozin remarkably reduced aortic accumulation of macrophages, CD4+ T cells, and B cells particularly following dapagliflozin treatment at 5 mg/kg. Dapagliflozin treatment also markedly attenuated medial SMC loss. Though the difference was not significant, dapagliflozin treatment tended to attenuate CD8+ T cells and elastin degradation. Dapagliflozin treatment at 5 mg/kg caused a 53% reduction in neovessel density. Furthermore, dapagliflozin treatment mitigated further progress of existing AAAs. Conclusion. Dapagliflozin treatment ameliorated PPE-induced AAAs by inhibiting aortic leukocytes infiltration and angiogenesis.

Metformin therapy is not associated with the lower prevalence of ascending aortic aneurysm in diabetic patients

OBJECTIVES

Metformin therapy has previously been associated with reduced abdominal aortic aneurysm growth rate in diabetic patients and shown to suppress the formation and progression of abdominal aortic aneurysm in normoglycemic mice. Here, we investigated the association between Metformin treatment and prevalence of aneurysm in the ascending aorta (AscAA).

METHODS

A total of 734 patients undergoing open-heart surgery for AscAA and/or aortic valve disease were studied. Diabetes status and medication use were self-reported by the patients in a systematic questionnaire. Aortic dilatation was defined as an aortic root or ascending aortic diameter ≥4.0 cm. High-sensitivity C-reactive protein levels were assessed as a measure of systemic inflammation.

RESULTS

We could confirm the inverse association between diabetes and AscAA prevalence (16% vs 43.9%, for diabetic and non-diabetic patients, respectively; Odds ratio 0.243; 95% CI, 0.129-0.460, P < 0.001). Furthermore, in diabetic patients, Metformin treatment was associated with lower high-sensitivity C-reactive protein levels. There was, however, no difference in the prevalence of AscAA among diabetic patients with and without Metformin treatment (16% vs 16% for treated and non-treated patients, respectively; OR 1.039; 95% CI 0.26-4.19, P = 0.957).

CONCLUSIONS

Our data do not support a protective effect of Metformin therapy in AscAA formation.

SUBJ COLLECTION

161, 173.

The role of dipeptidyl peptidase-IV in abdominal aortic aneurysm pathogenesis: A systematic review

Abdominal aortic aneurysm (AAA) is an important vascular disease carrying significant mortality implications due to the risk of aneurysm rupture. Current management relies exclusively on surgical repair as there is no effective medical therapy. A key element of AAA pathogenesis is the chronic inflammation mediated by inflammatory cells releasing proteases, including the enzyme dipeptidyl peptidase IV (DPP-IV). This review sought to recapitulate available evidence on the involvement of DPP-IV in AAA development. Further, we assessed the experimental use of currently available DPP-IV inhibitors for AAA management in murine models. Embase, Medline, PubMed, and Web of Science databases were utilised to access the relevant studies. The review was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA). A narrative synthesis approach was used. Sixty-four studies were identified from the searched databases; a final 11 were included in the analysis. DPP-IV was reported to be significantly increased in both AAA tissue and plasma of patients and correlated with AAA growth. DPP-IV inhibitors (sitagliptin, vildagliptin, alogliptin, and teneligliptin) were all shown to attenuate AAA formation in murine models by reducing monocyte differentiation, the release of reactive oxygen species (ROS), and metalloproteinases (MMP-2 and MMP-9). DPP-IV seems to play a role in AAA pathogenesis by propagating the inflammatory microenvironment. This is supported by observations of decreased AAA formation and reduction in macrophage infiltration, ROS, matrix MMPs, and interleukins following the use of DPP-IV inhibitors in murine models. There is an existing translational gap from preclinical observations to clinical trials in this important and novel mechanism of AAA pathogenesis. This prior literature highlights the need for further research on molecular targets involved in AAA formation.