Association between use of oral-antidiabetic drugs and the risk of aortic aneurysm: a nested case-control analysis

Glycaemic Status and Risk of Abdominal Aortic Aneurysm: A Nationwide Cohort Study of Four Million Adults using Korean National Health Screening Data

OBJECTIVE

This retrospective cohort study aimed to confirm the previously reported inverse association between diabetes mellitus (DM) and abdominal aortic aneurysm (AAA) using large population based data. It also investigated the associations between AAA and impaired fasting glucose (IFG) and new onset DM (not yet treated).

METHODS

A representative dataset was obtained from the Korean National Health Insurance Service. Participants who were aged ≥ 50 years and received a national health examination in 2009 were included and followed until 31 December 2019. Glycaemic status was defined based on fasting plasma glucose level and the relevant diagnostic codes. AAA was ascertained using medical facility use records with relevant diagnostic codes or aneurysm repair surgery. A Cox proportional hazards model was used to examine the association between glycaemic status and AAA, with adjustment for confounders. Additionally, the interactions between glycaemic status and subgroups based on baseline characteristics were examined.

RESULTS

The study population comprised 4 162 640 participants. Participants with IFG or DM were significantly more likely to be male, older, and have comorbidities compared with normoglycaemic participants at baseline. The incidence of AAA was lower in participants with IFG or DM compared with normoglycaemic participants. The AAA risk was lower in patients with DM than in patients with IFG, and decreased linearly according to glycaemic status: the adjusted hazard ratio was 0.88 (95% confidence interval [CI] 0.85 - 0.91) for IFG, 0.72 (95% CI 0.67 - 0.78) for newly diagnosed DM, 0.65 (95% CI 0.61 - 0.69) for DM duration < 5 years, and 0.47 (95% CI 0.44 - 0.51) for DM duration ≥ 5 years compared with the normoglycaemia group. Both IFG and DM were related to reduced AAA risk in all subgroups, suggesting an independent association.

CONCLUSION

Both IFG and DM, even when not treated with antihyperglycaemic medication, were associated with a lower incidence of AAA. The AAA risk decreased linearly according to DM duration.

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.

Metformin Therapeutic Targets for Aortic Aneurysms: A Mendelian Randomization and Colocalization Study

Background

Identifying effective pharmacological interventions to prevent the progressive enlargement and rupture of aortic aneurysms (AAs) is critical. Previous studies have suggested links between metformin use and a decreased incidence of AAs. In this study, we employed Mendelian randomization (MR) to investigate causal effects of metformin's targets on AA risk and to explore the underlying mechanisms underlying these effects.

Methods

To examine the relationship between metformin use and AA risk, we implemented both two-sample MR and multivariable MR analyses. Utilizing genetic instrumental variables, we retrieved cis-expression quantitative trait loci (cis-eQTL) data for potential targets of metformin from the Expression Quantitative Trait Loci Genetics Consortium (eQTLGen) Consortium and Genotype-Tissue Expression (GTEx) project. Colocalization analysis was employed to ascertain the probability of shared causal genetic variants between single nucleotide polymorphisms (SNPs) associated with eQTLs and AA.

Results

Our findings reveal that metformin use reduces AA risk, exhibiting a protective effect with an odds ratio (OR) of 4.88 × 10 - 3 (95% confidence interval [CI]: 7.30 × 10 - 5 -0.33, p = 0.01). Furthermore, the protective effect of type 2 diabetes on AA risk appears to be driven by metformin use ( OR MVMR = 1.34 × 10 - 4 , 95% CI: 3.97 × 10 - 8 -0.45, p = 0.03). Significant Mendelian randomization (MR) results were observed for the expression of two metformin-related genes in the bloodstream: NADH:ubiquinone oxidoreductase subunit A6 (NDUFA6) and cytochrome b5 type B (CYB5B), across two independent datasets ( OR CYB5B = 1.35, 95% CI: 1.20-1.51, p = 2.41 × 10 - 7 ; OR NDUFA6 = 1.12; 95% CI: 1.07-1.17, p = 1.69 × 10 - 6 ). The MR analysis of tissue-specific expression also demonstrated a positive correlation between increased NDUFA6 expression and heightened AA risk. Lastly, NDUFA6 exhibited evidence of colocalization with AA.

Conclusions

Our study suggests that metformin may play a significant role in lowering the risk of AA. This protective effect could potentially be linked to the mitigation of mitochondrial and immune dysfunction. Overall, NDUFA6 has emerged as a potential mechanism through which metformin intervention may confer AA protection.

Treatment With Small Molecule Inhibitors of Advanced Glycation End-Products Formation and Advanced Glycation End-Products-Mediated Collagen Cross-Linking Promotes Experimental Aortic Aneurysm Progression in Diabetic Mice

Background Although diabetes attenuates abdominal aortic aneurysms (AAAs), the mechanisms by which diabetes suppresses AAAs remain incompletely understood. Accumulation of advanced glycation end- (AGEs) reduces extracellular matrix (ECM) degradation in diabetes. Because ECM degradation is critical for AAA pathogenesis, we investigated whether AGEs mediate experimental AAA suppression in diabetes by blocking AGE formation or disrupting AGE-ECM cross-linking using small molecule inhibitors. Methods and Results Male C57BL/6J mice were treated with streptozotocin and intra-aortic elastase infusion to induce diabetes and experimental AAAs, respectively. Aminoguanidine (AGE formation inhibitor, 200 mg/kg), alagebrium (AGE-ECM cross-linking disrupter, 20 mg/kg), or vehicle was administered daily to mice from the last day following streptozotocin injection. AAAs were assessed via serial aortic diameter measurements, histopathology, and in vitro medial elastolysis assays. Treatment with aminoguanidine, not alagebrium, diminished AGEs in diabetic AAAs. Treatment with both inhibitors enhanced aortic enlargement in diabetic mice as compared with vehicle treatment. Neither enhanced AAA enlargement in nondiabetic mice. AAA enhancement in diabetic mice by aminoguanidine or alagebrium treatment promoted elastin degradation, smooth muscle cell depletion, mural macrophage accumulation, and neoangiogenesis without affecting matrix metalloproteinases, C-C motif chemokine ligand 2, or serum glucose concentration. Additionally, treatment with both inhibitors reversed suppression of diabetic aortic medial elastolysis by porcine pancreatic elastase in vitro. Conclusions Inhibiting AGE formation or AGE-ECM cross-linking enhances experimental AAAs in diabetes. These findings support the hypothesis that AGEs attenuate experimental AAAs in diabetes. These findings underscore the potential translational value of enhanced ECM cross-linking as an inhibitory strategy for early AAA disease.

The association between diabetes and abdominal aortic aneurysms in men: results of two Danish screening studies, a systematic review, and a meta-analysis of population-based screening studies

BACKGROUND

A paradoxical protective effect of diabetes on the development and progression of abdominal aortic aneurysms (AAA) has been known for years. This study aimed to investigate whether the protective role of diabetes on AAAs has evolved over the years.

METHODS

A cross-sectional study, a systematic review and meta-analysis. This study was based on two large, population-based, randomised screening trials of men aged 65-74; VIVA (2008-2011) and DANCAVAS (2014-2018), including measurement of the abdominal aorta by ultrasound or CT, respectively. Analyses were performed using multiple logistic regressions to estimate the odds ratios (ORs) for AAAs in men with diabetes compared to those not having diabetes. Moreover, a systematic review and meta-analysis of population-based screening studies of AAAs to visualise a potential change of the association between diabetes and AAAs. Studies reporting only on women or Asian populations were excluded.

RESULTS

In VIVA, the prevalence of AAA was 3.3%, crude OR for AAA in men with diabetes 1.04 (95% confidence interval, CI, 0.80-1.34), and adjusted OR 0.64 (CI 0.48-0.84). In DANCAVAS, the prevalence of AAA was 4.2%, crude OR 1.44 (CI 1.11-1.87), and adjusted OR 0.78 (CI 0.59-1.04). Twenty-three studies were identified for the meta-analysis (N = 224 766). The overall crude OR was 0.90 (CI 0.77-1.05) before 2000 and 1.16 (CI 1.03-1.30) after 1999. The overall adjusted OR was 0.63 (CI 0.59-0.69) before 2000 and 0.69 (CI 0.57-0.84) after 1999.

CONCLUSION

Both the crude and adjusted OR showed a statistically non-significant trend towards an increased risk of AAA by the presence of diabetes. If this represents an actual trend, it could be due to a change in the diabetes population.

TRIAL REGISTRATION

DANCAVAS: Current Controlled Trials: ISRCTN12157806. VIVA: ClinicalTrials.gov NCT00662480.

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.

The influence of dipeptidyl peptidase-4 inhibitor on the progression of type B intramural hematoma

Objectives

Investigating whether dipeptidyl peptidase-4 inhibitors (DPP4i) could influence the progression of type B intramural hematoma (IMHB) in patients with diabetes mellitus (DM).

Materials and methods

Uncomplicated IMHB patients were matched by age, sex, and body mass index. Cox proportional hazard models were constructed to identify risk factors. A Kaplan–Meier survival analysis was used to estimate all-cause and aorta-related mortality.

Results

Ninety-six matched IMHB patients were divided into Group A (n = 32, IMHB patients without DM), Group B (n = 32, IMHB patients with DMreceiving oral antidiabetic drugs [without DPP4i]) and Group C (n = 32, IMHB patients with DM receiving oral antidiabetic drugs [with DPP4i]). Group C had the lowest rate of aorta-related adverse events (3.1%), aorta-related mortality (0.0%) and reintervention (3.1%). Cox proportional hazard models revealed that a lower eosinophil count (per 0.1, HR, 0.48; 95% CI, 0.29–0.79, P = 0.004) and a higher neutrophil to lymphocyte ratio (NLR) (HR, 1.13; 95% CI, 1.05–1.21, P = 0.001) were associated with higher occurrences of aorta-related adverse events. A lower eosinophil count (per 0.1, HR, 0.40; 95% CI, 0.18–0.89, P = 0.025) and a higher NLR (HR, 1.19; 95% CI, 1.08–1.32, P = 0.001) were also associated with increased aorta-related mortality.

Conclusion

DPP4i administration in DM patients with IMHB was associated with lower aorta-related mortality and more benign progression than in those who did not receive DPP4i or those without DM. Furthermore, a higher eosinophil count and a lower NLR ratio are potential protective factors that may explain the potential therapeutic benefit of DPP4i.

Chronic Thoracic Aortic Dissection: How to Treat, When to Intervene

Thoracic aortic dissection (AD) is associated with increased morbidity and mortality. Acute aortic syndrome is the first presentation of the disease in most cases. While acute AD management follows concrete guidelines because of its urgent and life-threatening nature, chronic AD is usually overlooked, although it concerns a wide spectrum of patients surviving an acute event. Acute AD survivors ultimately enter a chronic aortic disease course. Patients with chronic thoracic AD (CTAD) require lifelong surveillance and a proportion of them may present with symptoms and late complications demanding further surgical or endovascular treatment. However, the available data concerning the management of CTAD is sparse in the literature. The management of patients with CTAD is challenging as far as determining the best medical therapy and deciding on intervention are concerned. Until recently, there were no guidelines or recommendations for imaging surveillance in patients with chronic AD. The diagnostic methods for imaging aortic diseases have been improved, while the data on new endovascular and surgical approaches has increased significantly. In this review, we summarize the current evidence in the diagnosis and management of CTAD and the latest recommendations for the surgical/endovascular aortic repair of CTAD.

Association Between Metformin and Abdominal Aortic Aneurysm: A Meta-Analysis

Objective

To systematically examine the association between metformin and abdominal aortic aneurysm (AAA) and provide a basis for the treatment of AAA.

Methods

Pubmed, Embase, Cochrane Library, and Ovid databases were searched by computer to identify the literature related to metformin and AAA published until February 2022. The literature was screened according to the inclusion and exclusion criteria, data were extracted, and a quality assessment was conducted. The meta-analysis was performed using Stata 16.0 and RevMan 5.3 software.

Results

Seven articles containing a total of 10 cohort studies (85,050 patients) met the inclusion criteria and were included in the review. Meta-analysis showed that metformin can limit the expansion of AAA (MD = – 0.72, 95% CI: – 1.08 ~ −0.37, P < 0.00001), as well as reduce AAA repair or AAA rupture-related mortality (OR = 0.80, 95% CI:0.66 ~ 0.96, P = 0.02). The difference was statistically significant (P < 0.05).

Conclusion

Metformin can limit the expansion of AAA and reduce the incidence of AAA and postoperative mortality. However, further biological experiments and clinical trials still need to be conducted to support this.

Treatment with the Prolyl Hydroxylase Inhibitor JNJ Promotes Abdominal Aortic Aneurysm Progression in Diabetic Mice

OBJECTIVE

Prolyl hydroxylase domain containing proteins (PHD) rigorously regulate intracellular hypoxia inducible factor-1 (HIF-1) protein expression and activity. Diabetes impairs PHD activity and attenuates abdominal aortic aneurysm (AAA) progression. The extent to which dysregulated PHD activity contributes to diabetes mediated AAA suppression remains undetermined.

METHODS

AAAs were induced in diabetic and non-diabetic male C57BL/6J mice via intra-aortic elastase infusion. A PHD inhibitor (JNJ-42041935, aka "JNJ", 150 mmol/kg) or vehicle alone was administered daily starting one day prior to AAA induction for 14 days. Influences on AAA progression was assessed via ultrasonography and histopathology. Expression of aortic HIF-1α, three of its target genes and macrophage derived mediators were assayed via quantitative reverse transcription polymerase chain reaction. Aneurysmal sections from AAA patients with and without diabetes (two patients in each group) were immunostained for HIF-1α and vascular endothelial growth factor (VEGF)-A.

RESULTS

Expression of HIF-1α target genes (erythropoietin, VEGF-A, and glucose transporter-1) was reduced by 45% - 95% in experimental diabetic aortas. Diameter enlargement was similarly limited, as were mural elastin degradation, leukocyte infiltration, and neo-angiogenesis (reduced capillary density and length) on histopathology. Pre-treatment with JNJ prior to AAA initiation augmented aortic HIF-1α target gene expression and aneurysm progression in diabetic mice, along with macrophage VEGF-A and matrix metalloproteinase 2 mRNA expression. No differences were noted in HIF-1α or VEGF-A expression on aortic immunohistochemical staining of human aortic tissue as a function of diabetes status.

CONCLUSION

Small molecule PHD inhibitor treatment reduces or offsets impairment of experimental AAA progression in hyperglycemic mice, highlighting the potential contribution of dysregulated PHD activity to diabetes mediated aneurysm suppression.

Exploring the Correlation and Protective Role of Diabetes Mellitus in Aortic Aneurysm Disease

Introduction: Diabetes mellitus is recognised as a significant risk factor for cardiovascular and peripheral vascular disease, as the abnormal metabolic state increases the risk for atherosclerosis, occlusive arterial disease and vascular dysfunction. There have been reports of potential association across the literature that illustrates a link between diabetes mellitus and aortic aneurysm, with the former having a protective role on the development of the latter.

Methods: A thorough literature search was performed through electronic databases, to provide a comprehensive review of the study's reporting on the association of diabetes mellitus and aortic aneurysm, discussing the mechanisms that have been reported; furthemore, we reviewed the reports of the impact of oral hypoglycameic agents on aortic aneurysms.

Results: Various proposed mechanisms are involved in this protective process including endothelial dysfunction, chronic hyperglycemia and insulin resistance. The evidence suggests a negative association between these disease process, with prevelance of diabetes mellitus resulting in lower rates of aortic aneurysm, via its protective mechanistic action. The increase in advanced glycation end products, increased arterial stiffness and vascular remodelling seen in diabetes, was found to have a profound impact on aneurysm development, its slow progression and lower rupture rate in these individuals. This review has also highlighted the role of oral hypoglycaemic agents having a protective effect against AA disease.

Conclusion: A decrease in development, progression and mortality from aortic aneurysms as well as reduced rates of dissection, have been observed in those with diabetes. This review has provided a comprehensive insight on the effect of diabetes and its physiological processes, and elements of its con-committant treatment, having a protective role against these aortic diseases.

Inhibition of angiotensin-induced aortic aneurysm by metformin in apolipoprotein E-deficient mice

Objective

Metformin is associated with a reduced incidence and growth of abdominal aortic aneurysms (AAAs). The aim of the present study was to investigate the inhibitory effects of metformin on AAA development and possible underlying mechanisms in experimentally induced AAAs in mice, along with the possible synergistic effects of metformin and imatinib.

Methods

Angiotensin II was used to induce AAAs in apolipoprotein E knockout (ApoE ^-/- ) mice for 28 days. The mice were treated with metformin (n = 11), metformin combined with imatinib (n = 7), or vehicle (n = 12), starting 3 days before angiotensin II infusion. Ultrasound examination was used to analyze aneurysm formation. Cholesterol and blood pressure levels were measured at the start and end of the study. Gene array and quantitative polymerase chain reaction were used to analyze the changes in gene expression in the aorta. Wire myography was used to study vascular function.

Results

Metformin (n = 11) suppressed the formation and progression of AAAs by 50% compared with the vehicle controls (n = 12), with no further effects from imatinib (n = 7). Metformin reduced total cholesterol and mRNA expression of SPP1 (encoding osteopontin), MMP12, and the glycoprotein genes Gpnmb and Clec7a. Furthermore, metformin inhibited blood pressure increases and reduced vascular contractions, as determined by wire myography, and restored the anticontractile function of perivascular adipose tissue.

Conclusion

Metformin inhibited aneurysm formation and progression and normalized vascular function in ApoE ^-/- mice with no additional effect of imatinib. This might be mediated by the protective effects on vascular endothelial function and perivascular adipose tissue via reduced expression of genes promoting inflammation, including SPP1, MMP12, Gpnmb, and Clec7a.

Clinical relevance

Retrospective studies of the effects of metformin in patients with aneurysm have so far only been performed of those with type 2 diabetes. The present study shows that metformin has effects on nondiabetic mice and revealed the mechanistic effects mediated by the drug that could also be important to study as outcomes in humans. Future clinical trials using metformin are warranted in patients without diabetes with abdominal aortic aneurysms.

Editor's Choice - Association Between Metformin Prescription and Abdominal Aortic Aneurysm Growth and Clinical Events: a Systematic Review and Meta-Analysis

OBJECTIVE

A meta-analysis of the association between metformin prescription and abdominal aortic aneurysm (AAA) growth and events (rupture or surgical repair) was performed.

METHODS

Open source databases were searched for observational studies reporting the association between metformin prescription and AAA growth or events. Meta-analyses were performed using random effects models. The risk of bias of included studies was assessed using a quality assessment tool developed in a previous systematic review. Sensitivity analyses restricted to people with diabetes, leave one out analyses, and an individual patient risk factor adjusted sub-analysis were performed. Funnel plots assessed reporting bias.

RESULTS

Eight studies comprising 153 553 patients were included, of whom 35 240 were and 118 313 were not prescribed metformin. Pooled weighted mean (± standard deviation) AAA growth was significantly reduced in patients prescribed metformin (0.9 ± 0.4 mm/year) compared with those not receiving the medication (1.8 ± 0.4 mm/year; weighted mean difference [WMD] 0.8 mm/year, 95% confidence interval [CI] 0.5 - 1.1; p < .001; I² = 89%). Leave one out analysis suggested that the significance of findings did not change after removal of individual studies. A sub-analysis within people with diabetes suggested that metformin reduced AAA growth (WMD 0.7 mm/year, 95% CI 0.3 - 1.0). Metformin prescription was associated with a reduced risk of AAA events (risk ratio 0.6, 95% CI 0.4 - 0.9, p = .028). Three, four, and one studies had low, moderate, and high risk of bias, respectively. Individual patient data analysis suggested that metformin prescription slowed annual AAA growth by 0.5 mm/year (95% CI 0.2 - 0.7). The GRADE summary suggested that the certainty of evidence that metformin limited AAA growth and prevented AAA events was very low.

CONCLUSION

Observational studies suggest that metformin prescription is associated with a clinically important significant reduction in both growth and clinically relevant events in people with AAA. These findings support the need for randomised trials to examine the benefit of metformin.

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.

Risk reduction and pharmacological strategies to prevent progression of aortic aneurysms

INTRODUCTION

While size thresholds exist to determine when aortic aneurysms warrant surgical intervention, there is no consensus on how best to treat this disease before aneurysms reach the threshold for intervention. Since a landmark study in 1994 first suggested ß-blockers may be useful in preventing aortic aneurysm growth, there has been a surge in research investigating different pharmacologic therapies for aortic aneurysms - with very mixed results.

AREAS COVERED

We have reviewed the existing literature on medical therapies used for thoracic and abdominal aortic aneurysms in humans. These include ß-blockers, angiotensin II receptor blockers, and angiotensin-converting enzyme inhibitors as well as miscellaneous drugs such as tetracyclines, macrolides, statins, and anti-platelet medications.

EXPERT OPINION

While multiple classes of drugs have been explored for risk reduction in aneurysm disease, with few exceptions results have been disappointing with an abundance of contradictory findings. The vast majority of studies have been done in patients with abdominal aortic aneurysms or thoracic aortic aneurysm patients with Marfan Syndrome. There exists a striking gap in the literature when it comes to pharmacologic management of non-Marfan Syndrome patients with thoracic aortic aneurysms. Given the differences in pathogenesis, this is an important future direction for aortic aneurysm research.

Current pharmacological management of aortic aneurysm

ABSTRACT

Aortic aneurysm (AA) remains one of the primary causes of death worldwide. Of the major treatments, prophylactic operative repair is used for AA to avoid potential aortic dissection (AD) or rupture. To halt the development of AA and alleviate its progression into AD, pharmacological treatment has been investigated for years. Currently, β-adrenergic blocking agents, losartan, irbesartan, angiotensin-converting-enzyme inhibitors, statins, antiplatelet agents, doxycycline, and metformin have been investigated as potential candidates for preventing AA progression. However, the paradox between preclinical successes and clinical failures still exists, with no medical therapy currently available for ideally negating the disease progression. This review describes the current drugs used for pharmacological management of AA and their individual potential mechanisms. Preclinical models for drug screening and evaluation are also discussed to gain a better understanding of the underlying pathophysiology and ultimately find new therapeutic targets for AA.

Importance of NLRP3 Inflammasome in Abdominal Aortic Aneurysms

Abdominal aortic aneurysm (AAA) is a chronic inflammatory degenerative aortic disease, which particularly affects older people. Nucleotide-binding oligomerization domain-like receptor family protein 3 (NLRP3) inflammasome is a multi-protein complex and mediates inflammatory responses by activating caspase 1 for processing premature interleukin (IL)-1β and IL-18. In this review, we first summarize the principle of NLRP3 inflammasome activation and the functionally distinct classes of small molecule NLRP3 inflammasome inhibitors. Next, we provide a comprehensive literature review on the expression of NLRP3 inflammasome effector mediators (IL-1β and IL-18) and components (caspase 1, apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC) and NLRP3) in clinical and experimental AAAs. Finally, we discuss the influence of genetic deficiency or pharmacological inhibition of individual effector mediators and components of NLRP3 inflammasome on experimental AAAs. Accumulating clinical and experimental evidence suggests that NLRP3 inflammasome may be a promise therapeutic target for developing pharmacological strategies for clinical AAA management.

Sex Differences in Rupture Risk and Mortality in Untreated Patients With Intact Abdominal Aortic Aneurysms

Background

Studies on intact abdominal aortic aneurysms mainly focus on treated patients, and data on untreated patients are sparse. The objective was to investigate sex differences among untreated patients regarding rupture and mortality rates and to determine predictors for these events. Sex‐specific causes of death were evaluated.

Methods and Results

All patients ≥40 years diagnosed from 2001 to 2015 (n=32 393) with intact abdominal aortic aneurysms were identified in national registries; 60% (n=19 569) were untreated. Comorbid loads, crude rupture, and mortality rates were assessed. Predictors of 5‐year rupture and mortality were analyzed in Cox models (sex, age, comorbidities, income, and marital status). The proportion of men and women with multiple comorbidities was similar. Within 5 years, 798 ruptures occurred (9.7% women versus 6.9% men, P<0.001). Ruptures were independently predicted by female sex (hazard ratio [HR], 1.23; 95% CI, 1.07–1.42; P=0.004), chronic obstructive pulmonary disease (HR, 1.36; 95% CI, 1.15–1.62; P<0.001), age (HR, 11.49; 95% CI, 5.68–23.25 for ≥80 years; P<0.001), and income (HR, 0.63; 95% CI, 0.53–0.75 for highest tertile; P<0.001). After 5 years, 56.5% women and 50.4% men were deceased. Mortality was not independently predicted by female sex. Rupture was the third most common cause of death (11.9% women versus 8.7% men; P<0.001). The median time‐to‐events was 2.8 years.

Conclusions

A considerable proportion of patients with intact abdominal aortic aneurysms in surveillance remain untreated. Despite surveillance algorithms, the healthcare system fails to prevent a high number of ruptures, especially among women. The time‐to‐event data highlight the urgency to develop more individualized surveillance.

Lower risk of subarachnoid haemorrhage in diabetes: a nationwide population-based cohort study

Background and purpose

Diabetes mellitus (DM) is a common metabolic disorder with increased risk of cardiovascular and cerebrovascular complications. However, its relationship with risk of subarachnoid haemorrhage (SAH), the most devastating form of stroke, remains controversial.

Methods

To evaluate the relationship between DM and risk of SAH, we performed a retrospective cohort study using a nationwide, population‐based, health screening database in Korea. We included participants without history of stroke who underwent a nationwide health screening programme between 2003 and 2004. Primary outcome was occurrence of SAH. Participants were followed up until development of SAH or December 2015. Multivariate Cox proportional hazards regression analysis was performed with adjustments for age, sex, systolic blood pressure, total cholesterol, body mass index, physical activity, smoking status, alcohol habit, household income and treatment with antihypertensive agents and statins.

Results

Among 421 768 study participants, prevalence of DM was 9.6%. During a mean follow-up period of 11.6±1.9 years, 1039 patients developed SAH. Presence of DM was significantly associated with decreased risk of SAH (adjusted HR 0.68; 95% CI 0.53 to 0.86; p<0.001). Elevated level of fasting blood glucose was also negatively associated with risk of SAH (adjusted HR per 1 mmol/L increase 0.90; 95% CI 0.86 to 0.95; p<0.001).

Conclusion

DM and elevated level of fasting blood glucose were inversely associated with risk of SAH. Further studies may elucidate the possibly protective, pathophysiological role played by hyperglycaemia in patients at risk of SAH.

Outcomes of uncomplicated Type B intramural hematoma patients with Type 2 diabetes mellitus

OBJECTIVES

We aimed to summarize the clinical presentations, therapeutic approaches, and outcomes of Type B intramural hematoma (IMHB) patients with and without Type 2 diabetes mellitus (DM).

METHODS

Patients with uncomplicated IMHBs were included between January 2016 and January 2018 and divided into two groups according to whether or not they had DM. We also assessed the potential diagnostic value of serum matrix metalloproteinase-9 (MMP-9) level and the association of it with the disease progression of uncomplicated IMHB patients with and without DM.

RESULTS

A total of 149 patients were included (DM group [n = 60] and non-DM group [n = 89]). Patients in the non-DM group underwent thoracic endovascular aortic repair treatment more frequently (12% vs 2%, p = .028) and had a higher reintervention rate during the follow-up (9 in 81 patients, 11% vs. 2%, p = .043). There were significant differences between the two groups regarding the aorta-related mortality rate during the acute phase (9% vs. 0%, p = .042) and the all-cause mortality rate (22% vs. 7%, p = .011). Ulcer-like projection (ULP) development (during the acute phase; hazard ratio [HR], 1.21; 95% confidence interval [CI], 1.15-1.79, p = .005), C-reactive protein (CRP) levels (HR, 2.08; 95% CI, 1.91-3.91, p = .003), and MMP-9 levels (HR, 15.77; 95% CI, 6.48-21.62, p < .001) were associated with an elevated risk for aorta-related mortality.

CONCLUSIONS

IMHBs with DM have a considerably better prognosis and serum MMP-9 level appear to be a potential biomarker to predict the disease progression. ULP development (during the acute phase) and CRP levels are also associated with an elevated risk for aorta-related mortality.

The Protective Effect of Metformin on Abdominal Aortic Aneurysm: A Systematic Review and Meta-Analysis

BACKGROUND

Type 2 diabetes mellitus (T2DM) patients have a lower risk of abdominal aortic aneurysm (AAA) and its comorbidities, which might be associated with the usage of metformin. The objective of the study was to evaluate the role of metformin in the process of AAA development.

METHOD

PubMed, Embase and Cochrane Library were searched up to May 15^th, 2021. We implemented several methods including the risk of bias graph, GRADE system and funnel plot to assess the quality and possible bias of this study. Subgroup analysis and sensitivity analysis were applied to address quality differences and validate the robustness of the final results.

RESULT

Ten articles were enrolled after screening 151 articles searched from databases. The pooled results showed that, compared with T2DM patients without metformin, metformin prescription was associated with a slower annual growth rate of the aneurysm (mean difference (MD) -0.67 cm [95% confidence interval (CI) -1.20 ~ -0.15 cm]). Besides, metformin exposure was associated with a lower frequency of AAA events (odds ratio (OR) 0.61 [95% CI 0.41-0.92]).

CONCLUSION

Metformin alleviated both annual expansion rate and aneurysm rupture frequency in AAA patients with T2DM.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO, identifier https://www.crd.york.ac.uk/PROSPERO/display_record.php?RecordID=217859 (CRD42020217859).

Diabetes, its duration, and the long-term risk of abdominal aortic aneurysm: The Atherosclerosis Risk in Communities (ARIC) Study

BACKGROUND AND AIMS

We aimed at comprehensively evaluate the independent association of diabetes and its duration with incident abdominal aortic aneurysm (AAA) and aortic diameter.

METHODS AND RESULTS

We prospectively studied incident AAA according to baseline glycemic status (diabetes, prediabetes, normal glycemia) in 13,116 ARIC participants (1990-1992) and the time-varying exposure of duration post incident diabetes in 11,675 participants (1987-1989) using Cox models. Additionally, we cross-sectionally explored ultrasound-based abdominal aortic diameter by glycemic status and cumulative duration of diabetes in 4710 participants (2011-2013) using linear regression models. Over ~20 years of follow-up, diabetes (vs. normal glycemia) at baseline was independently associated with lower AAA risk (489 cases) (hazard ratio: 0.71 [95%CI 0.51-0.99]), especially after 10 years (hazard ratio: 0.58 [0.38-0.87]). Prediabetes did not demonstrate an independent association. The inverse association was more evident with longer duration of diabetes (p for trend = 0.045), with 30-50% lower risk in eight years after diabetes diagnosis. The cross-sectional analysis demonstrated smaller aortic diameters with longer duration of diabetes (e.g., -0.76 mm [-1.24, -0.28] in diabetes with 8-12 years) compared to non-diabetes, whereas prediabetes consistently showed nominally greater diameter.

CONCLUSIONS

Diabetes, especially with longer duration, but not prediabetes, was independently associated with lower risk of AAA and smaller aortic diameter. Our findings suggest that long lasting clinical hyperglycemia plays an important role in the reduced AAA risk, and the reduced aortic diameter may be a structural mechanism behind this paradoxical association.

Diabetes Mellitus and Noncardiac Atherosclerotic Vascular Disease-Pathogenesis and Pharmacological Treatment Options

Diabetes mellitus (DM) is also a cause of cardiovascular (CV) disease (CVD). Addressing the atherosclerotic CVD (ASCVD) burden in DM should reduce premature death and improve quality of life. Diabetes mellitus-associated ASCVD can lead to complications in all vascular beds (carotids as well as coronary, lower extremity, and renal arteries). This narrative review considers the diagnosis and pharmacological treatment of noncardiac atherosclerotic vascular disease (mainly in patients with DM). Based on current knowledge and the fact that modern DM treatment guidelines are based on CV outcome trials, it should be noted that patients with noncardiac CVD may not have the same benefits from certain drugs compared with patients who predominantly have cardiac complications. This leads to the conclusion that in the future, consideration should be given to conducting well-designed trials that will answer which pharmacological treatment modalities will be of greatest benefit to patients with noncardiac ASCVD.

Outcomes of type A intramural hematoma: Influence of diabetes mellitus

OBJECTIVES

We aimed to investigate whether uncomplicated type A intramural hematoma (IMHA) patients with type 2 diabetes mellitus (DM) who underwent a "wait-and-watch strategy" and tight glycemic control had similar clinical outcomes as patients without DM who received the same treatment strategy.

METHODS

Between January 2010 and December 2016, uncomplicated IMHA patients with and without diabetes mellitus were included and were propensity score-matched to improve the balance between the two groups. Cox proportional hazard models were constructed to identify the specific factors associated with aorta-related mortality. The Fine-Gray model for the competing risk analysis was used to estimate the aorta-related and nonaorta-related mortality in different groups during the follow-up period.

RESULTS

A total of 109 IMHA patients were included in this study, and 66 patients were included after matching. Patients without DM experienced significantly more aorta-related adverse events (51.6% vs 13.3%; P = .001) and reinterventions than patients in the DM group (29.0% vs 6.7%; P = .023). Cox regression analysis revealed that a higher matrix metalloproteinase-9 level (hazard ratio [HR], 1.70; 95% confidence interval [CI], 1.39-2.09; P < .001) and larger maximum aortic diameter (HR, 1.41; 95% CI, 1.11-1.80; P = .005) were associated with higher aorta-related mortality. The competing risk analysis revealed a significantly higher aorta-related mortality during the follow-up period in the no DM group than in the DM group (36.4%; 95% CI, 11.6%-82.3%; P = .0294).

CONCLUSIONS

Uncomplicated IMHA patients with DM (receiving the "wait-and-watch strategy" and tight glycemic control) may have lower aorta-related mortality and rates of aorta-related adverse events and reinterventions than the no DM group.

Background and Proposed Design for a Metformin Abdominal Aortic Aneurysm Suppression Trial

Abdominal aortic aneurysm (AAA) may lead to rupture and death if left untreated. While endovascular or surgical repair is generally recommended for AAA greater than 5–5.5 cm, the vast majority of aneurysms detected by screening modalities are smaller than this threshold. Once discovered, there would be a significant potential benefit in suppressing the growth of these small aneurysms in order to obviate the need for repair and mitigate rupture risk. Patients with diabetes, in particular those taking the oral hypoglycaemic medication metformin, have been shown to have lower incidence, growth rate, and rupture risk of AAA. Metformin therefore represents a widely available, non-toxic, potential inhibitor of AAA growth, but thus far no prospective clinical studies have evaluated this. Here, we present the background, rationale, and design for a randomised, double-blind, placebo-controlled clinical trial of metformin for growth suppression in patients with small AAA.

Metformin Prescription Associated with Reduced Abdominal Aortic Aneurysm Growth Rate and Reduced Chemokine Expression in a Swedish Cohort

BACKGROUND

Recent reports suggest that the negative association between diabetes mellitus and abdominal aortic aneurysm (AAA) may be driven by metformin, the world's most common antidiabetic drug rather than diabetes per se. We sought to investigate the association among AAA growth rate, chemokine profile, and metformin prescription in a contemporary Swedish cohort.

METHODS

Patients under surveillance for small AAA were identified at 4 Swedish vascular centers with active AAA screening programs. Annual AAA growth rate, medical history, and prescribed medications were recorded for linear regression analysis. In a subset of patients with AAA and control subjects without AAA or diabetes, plasma samples were available and analyzed for 40 inflammatory chemokines.

RESULTS

A total of 526 patients were included for AAA growth analysis: 428 without type 2 diabetes mellitus (T2DM), 65 with T2DM and metformin prescription, and 33 with T2DM but without metformin prescription. Patients were included from 2005 to 2017 with mean follow-up of 3.2 (1.7) years and median annual AAA growth rate 1.6 mm, range -4.8 to 15.4 mm. Mean (standard deviation) annual AAA growth rates were 2.3 (2.2) mm in non-T2DM patients versus 1.1 (1.1) mm in patients with T2DM with metformin prescription and 1.6 (1.4) mm among those with T2DM without metformin prescription. With non-T2DM patients as reference in an unadjusted and 2 adjusted models, metformin prescription was significantly associated with reduced AAA growth rate (P < 0.001, P = 0.005, and P = 0.024, respectively), but not T2DM without metformin prescription (P = 0.137, P = 0.331, and P = 0.479, respectively). Among 240 patients with AAA (152 without T2DM, 51 with T2DM and metformin, and 37 with T2DM without metformin) and 59 without AAA or T2DM, metformin prescription was associated with reduced expression of chemokines representing all classes of leukocytes.

CONCLUSIONS

Metformin prescription is associated with reduced AAA growth rate, possibly mediated by broad anti-inflammatory effects. A randomized controlled trial is needed to determine what role metformin may play in AAA disease, particularly in the absence of T2DM.

Abdominal aortic aneurysm: a review on the role of oral antidiabetic drugs

INTRODUCTION

A paradoxical negative association between diabetes mellitus and abdominal aortic aneurysm (AAA) prevalence and growth is established. However, so far is not possible to determine whether this protection comes from the disease itself or the medication for Diabetes. The aim of this manuscript is to review the association between oral antidiabetic drugs and AAA incidence and growth.

EVIDENCE ACQUISITION

A search was conducted on PubMed and Scopus databases until December 2019 to identify publications reporting on the association between oral antidiabetic drugs (biguanides/metformin, sulfonylureas(SU), thiazolidinediones(TZD), dipeptidyl-peptidase 4(DPP-4) inhibitors, glucagon-like peptide 1(GLP-1) agonists, sodium-glucose transporter protein-2(SGLT2) inhibitors) and the outcomes AAA incidence and growth. Only data from human studies were considered, with a minimum of 3 months follow-up.

EVIDENCE SYNTHESIS

Six studies enrolling 25,810 patients were included: one reporting on the AAA risk and five reporting on AAA growth. Metformin prescription was associated with a 28% reduction in AAA occurrence, while SU and TZD were associated with a 18% decrease in AAA risk. Regarding AAA enlargement, results were concordant for a slower expansion rate associated with metformin, with a decrease ranging from -0.30 mm/y to -1.30 mm/y, but not consistent for other antidiabetic drugs.

CONCLUSIONS

Metformin seems to be associated with a decrease in AAA risk and enlargement rate. Evidence for the other classes is lacking. Studies evaluating the association between oral antidiabetic drugs and AAA progression, independently of the diabetic status, are needed.

Association between metformin and abdominal aortic aneurysm in diabetic and non-diabetic US veterans

We sought to examine the progression from abdominal aortic aneurysm (AAA) diagnosis to surgery and death among diabetics with and without exposure to metformin as well as non-diabetics. We conducted a retrospective cohort study (January 2000 to July 2019) comparing 3 transitions (AAA surgery, death, and death after AAA surgery) among propensity score-matched metformin-exposed and unexposed diabetic veterans and non-diabetic veterans using the VA Informatics and Computing Infrastructure database. We fit an adjusted Cox proportional hazards model with transition-specific effects. There were 43,073 metformin-unexposed diabetics, 24,361 metformin-exposed diabetics and 56,006 non-diabetics. Compared with the non-diabetic cohort, both diabetic cohorts have a lower risk of surgery (no metformin (HR=0.740, 95% CI 0.706 to 0.776); with metformin (HR=0.770, 95% CI 0.730 to 0.813)). However, the non-metformin diabetic cohort has a higher risk of death (HR=1.024, 95% CI 1.004 to 1.045) and death after surgery (HR=1.086, 95% CI 1.013 to 1.165). The metformin-exposed diabetic cohort has a lower risk of death in the first 10 years after AAA diagnosis (HR=0.877, 95% CI 0.855 to 0.899), yet a higher risk of death 10 years after AAA diagnosis (HR=1.177, 95% CI 1.092 to 1.270) compared with non-diabetic cohort. Non-diabetics have the highest rate of AAA surgery compared with both diabetic cohorts. However, diabetics without metformin have the highest risk of death prior to, and after surgery. This research provides novel findings for patients diagnosed with AAA. The use of metformin after both AAA diagnosis and surgery should be further investigated.

Diabetes Is Not Associated with the Risk of Rupture Among Patients with Abdominal Aortic Aneurysms - Results From a Large Danish Register Based Matched Case Control Study From 1996 to 2016

OBJECTIVE

Numerous studies have shown a paradoxical protective effect of diabetes on the development and progression of abdominal aortic aneurysm (AAA). The aim of this study was to investigate whether the protective role of diabetes on AAA extends to rupture, given the presence of an AAA.

METHODS

This was a register based case control study. Patients with ruptured AAA (RAAA) were matched 1:1 with patients undergoing elective surgery for AAA by sex, age, and year of diagnosis. Multiple conditional logistic regression was performed to estimate the odds ratio (OR) associating a diagnosis of diabetes with RAAA. No protocol was registered.

RESULTS

From 1996 to 2016, there were 6293 potential people with RAAA. A total of 898 people with a RAAA were excluded since no matching controls existed. This left 5 395 cases in the study. The cases had a median age of 75, and 85.4% were men. Diabetes was defined by hospital diagnosis or the redemption of antidiabetic prescriptions within one year. Comparing cases with controls and the presence of diabetes, a significant crude OR of 0.82 (95% confidence interval [CI] 0.71-0.95) was found. When adjusting for confounders OR increased to 0.97 (CI 0.83-1.14). Stratifying by age and year of diagnosis did not change the results markedly. OR associating RAAA with diabetes was significantly elevated in women (adjusted OR 1.82 [CI 1.17-2.81]). Of the 5395 cases, the overall 30 days mortality was 58% (n = 3145). Using Cox regression, a crude hazard ratio (HR) of 1.06 (CI 0.93-1.22) was found for the 30 day mortality and having diabetes compared with not having diabetes. Adjusting for index year, male sex, and age had little effect on this estimate (HR 1.11 [CI 0.97-1.28]).

CONCLUSION

Diabetes was not found to protect against RAAA, given the presence of an AAA. Furthermore, diabetes did not increase the risk of dying within 30 days of RAAA.

Relationship between metformin and abdominal aortic aneurysm

Abdominal aortic aneurysm (AAA) is a life-threatening disease and pharmacologic agents to treat the disease remain lacking for clinical practice. Epidemiologic studies have highlighted a negative association between the use of antidiabetic drugs, including metformin, and AAA. Metformin is well-known for its blood glucose-lowering effect, but its action on both metabolism and inflammatory response has led to propose it as a potential therapeutic target in several cardiovascular diseases. In this review, we summarize the current knowledge on the link between metformin and AAA. Based on the known effects of the drug on the aortic wall, translational applications and clinical trials investigating the interest of metformin in the management of patients with AAA are discussed.

Diabetes and aortic aneurysm: current state of the art

Aortic aneurysm is a life-threatening disease due to the risk of aortic rupture. The only curative treatment available relies on surgical approaches; drug-based therapies are lacking, highlighting an unmet need for clinical practice. Abdominal aortic aneurysm (AAA) is frequently associated with atherosclerosis and cardiovascular risk factors including male sex, age, smoking, hypertension, and dyslipidaemia. Thoracic aortic aneurysm (TAA) is more often linked to genetic disorders of the extracellular matrix and the contractile apparatus but also share similar cardiovascular risk factors. Intriguingly, a large body of evidence points to an inverse association between diabetes and both AAA and TAA. A better understanding of the mechanisms underlying the negative association between diabetes and aortic aneurysm could help the development of innovative diagnostic and therapeutic approaches to tackle the disease. Here, we summarize current knowledge on the relationship between glycaemic parameters, diabetes, and the development of aortic aneurysm. Cellular and molecular pathways that underlie the protective effect of diabetes itself and its treatment are reviewed and discussed, along with their potential implications for clinical translation.

Translational applications of glucose metabolism in abdominal aortic aneurysm

Even though diabetes mellitus is a major risk for cardiovascular events and atherosclerosis-related diseases, it is negatively associated with abdominal aortic aneurysm. The understanding of the mechanisms underlying this negative association could bring new insights to identify prognostic and therapeutic targets. Here we summarize current knowledge of the relationship between glycemic parameters and clinical outcomes of patients with abdominal aortic aneurysm. Translational applications of glucose-targeted approaches as well as their potential interest for clinical practice are discussed in this context.

Association of abdominal aortic aneurysm diameter with insulin resistance index

Introduction

Epidemiological studies have highlighted a negative association between diabetes and abdominal aortic aneurysm (AAA). The aim of this study was to investigate the association between insulin resistance and AAA size.

Materials and methods

This prospective cross sectional monocentric study analysed fasting blood samples from 55 patients with AAA eligible for surgical repair. They were divided into 2 groups according to the median AAA diameter: diameter < 50 mm (N = 28) and diameter > 50 mm (N = 27). The median ages were respectively 73 years (62 - 79) and 72 years (67 - 81). Glucose and fructosamine concentrations were determined by spectrophotometry; insulin and C-peptide using chemiluminescent technology. Homeostasis model assessment 2 calculator was used to estimate insulin resistance index (HOMA2 IR).

Results

There was no significant difference for fasting glucose concentration between the groups (6.1 vs. 5.9 mmol/L, P = 0.825). C-peptide and insulin concentrations, as well as HOMA2 IR index were significantly higher in patients with AAA > 50 mm (0.82 vs. 0.54 nmol/L, P = 0.012; 9 vs. 5 mU/L, P = 0.019 and 1.72 vs. 1.26, P = 0.028, respectively). No linear correlation was identified between AAA diameter and HOMA2 IR. Fructosamine concentration was lower in patients with AAA > 50 mm (225.5 vs. 251 μmol/L, P = 0.005) and negatively correlated with AAA diameter (r = - 0.54, P < 0.001).

Conclusion

This study evidenced an association between AAA diameter and insulin resistance. Further studies are required to determine a causal link between insulin resistance and AAA development.

Metformin prescription and aortic aneurysm: systematic review and meta-analysis

OBJECTIVE

To assess the association of metformin prescription with the risk of aortic aneurysm, aortic aneurysm events and the enlargement of abdominal aortic aneurysm (AAA).

DESIGN

Systematic review and meta-analysis.

METHODS

We searched PubMed, Embase and Scopus for epidemiological studies up to November 2018. We included observational studies which evaluated the association of metformin prescription with the risk of aortic aneurysm disease, and we also included studies involving progression and enlargement of AAA. The Newcastle-Ottawa Scale was used to assess the quality of included studies. Random-effect meta-analyses were conducted in line with the between-study heterogeneity. Sensitivity analyses were performed to identify the source of heterogeneity.

RESULTS

Eight studies enrolling 29 587 participants met the inclusion criteria and were included in this systematic review. We found that metformin prescription could significantly limit the enlargement of aortic aneurysm (weighted mean difference: -0.83 mm/year, 95% CI -1.38 to -0.28, I²=89.6%) among patients with AAA. Metformin prescription status may be associated with a decreased risk of aortic aneurysm and aortic aneurysm events.

CONCLUSIONS

According to the available epidemiological evidence, metformin prescription could limit the expansion of AAA among patients with this disease, and may be involved with a lower incidence of aortic aneurysm and aortic aneurysm events. Randomised controlled trials are needed to confirm whether metformin could reduce the enlargement of AAA in patients with or without diabetes.

Metformin prescription status and abdominal aortic aneurysm disease progression in the U.S. veteran population

BACKGROUND

Identification of a safe and effective medical therapy for abdominal aortic aneurysm (AAA) disease remains a significant unmet medical need. Recent small cohort studies indicate that metformin, the world's most commonly prescribed oral hypoglycemic agent, may limit AAA enlargement. We sought to validate these preliminary observations in a larger cohort.

METHODS

All patients with asymptomatic AAA disease managed in the Veterans Affairs Health Care System between 2003 and 2013 were identified by International Classification of Diseases, Ninth Revision codes. Those with a concomitant diagnosis of diabetes mellitus who also received two or more abdominal imaging studies (computed tomography, magnetic resonance imaging, or ultrasound) documenting the presence and size of an AAA, separated by at least 1 year, were included for review. Maximal AAA diameters were determined from radiologic reports. Further data acquisition was censored after surgical AAA repair, when performed. Comorbidities, active smoking status, and outpatient medication records (within 6 months of AAA diagnosis) were also queried. Yearly AAA enlargement rates, as a function of metformin treatment status, were compared using two statistical models expressed in millimeters per year: a multivariate linear regression (model 1) and a multivariate mixed-effects model with random intercept and random slope (model 2).

RESULTS

A total of 13,834 patients with 58,833 radiographic records were included in the analysis, with radiology imaging follow-up of 4.2 ± 2.6 years (mean ± standard deviation). The average age of the patients at AAA diagnosis was 69.8 ± 7.8 years, and 39.7% had a metformin prescription within ±6 months of AAA. The mean growth rate for AAAs in the entire cohort was 1.4 ± 2.0 mm/y by model 1 analysis and 1.3 ± 1.6 mm/y by model 2 analysis. The unadjusted mean rate of AAA growth was 1.2 ± 1.9 mm/y for patients prescribed metformin compared with 1.5 ± 2.2 mm/y for those without (P < .001), a 20% decrease. This effect remained significant when adjusted for variables relevant on AAA progression: metformin prescription was associated with a reduction in yearly AAA growth rate of -0.23 mm (95% confidence interval, -0.35 to -0.16; P < .001) by model 1 analysis and 0.20 mm/y (95% confidence interval, -0.26 to -0.14; P < .001) by model 2 analysis. A subset analysis of 7462 patients with baseline AAA size of 35 to 49 mm showed a similar inhibitory effect (1.4 ± 2.0 mm/y to 1.7 ± 2.2 mm/y; P < .001). Patients' factors associated with an increased yearly AAA growth rate were baseline AAA size, metastatic solid tumors, active smoking, chronic obstructive pulmonary disease, and chronic renal disease. Factors associated with decreased yearly AAA growth rates included prescriptions for angiotensin II type 1 receptor blockers or sulfonylureas and the presence of diabetes-related complications.

CONCLUSIONS

In a nationwide analysis of diabetic Veterans Affairs patients, prescription for metformin was associated with decreased AAA enlargement. These findings provide further support for the conduct of prospective clinical trials to test the ability of metformin to limit progression of early AAA disease.

Dypeptidylpeptidase-4 inhibitors and the cardiovascular system: How to manage the fil rouge

Dypeptidylpeptidase-4 (DPP-4) inhibitors are a therapeutic option for improving glucose control in patients with type 2 diabetes. They can be prescribed at different stages of the natural history of the disease because of their low risk for hypoglycemia and associated weight gain. For all new drugs for diabetes, the US Food and Drug Administration requires the demonstration of the cardiovascular (CV) safety profile through pooled analyses of phase 3 studies or specifically designed trials. A significant superiority over placebo has been observed with a sodium-dependent glucose transporter-2 inhibitor, empagliflozin, and two glucagon-like peptide-1 receptor agonists, liraglutide and semaglutide, thus suggesting cardioprotective effects for some antidiabetic drugs. The neutral results of CV safety trials on DPP-4 inhibitors have been disappointing, appearing to contradict the data from pooled analyses and meta-analyses of early trials. The main aim of this review is to find a possible interpretation for the differences between the results of these early trials and the CV safety studies with DPP-4 inhibitors. We conclude that the hypothesis of additional beneficial effects by DPP-4 inhibitors (beyond the improvement of glucose control), on the CV system in low-risk patients in primary prevention, needs to be verified with specifically designed studies.

Diabetes mellitus and the risk of abdominal aortic aneurysm: A systematic review and meta-analysis of prospective studies

BACKGROUND

Diabetes mellitus has been associated with reduced risk of abdominal aortic aneurysm in a number of epidemiological studies, however, until recently little data from prospective studies have been available. We therefore conducted a systematic review and meta-analysis of prospective studies to quantify the association.

MATERIAL AND METHODS

Two investigators searched the PubMed and Embase databases for studies of diabetes and abdominal aortic aneurysm up to May 8th 2018. Prospective studies were included if they reported adjusted relative risk (RR) estimates and 95% confidence intervals (95% CIs) of abdominal aortic aneurysm associated with a diabetes diagnosis. Summary relative risks were estimated by use of a random effects model.

RESULTS

We identified 16 prospective studies with 16,572 cases among 4,563,415 participants that could be included in the meta-analysis. The summary RR for individuals with diabetes compared to individuals without diabetes was 0.58 (95% CI: 0.51-0.66, I² = 40.4%, p_{heterogeneity} = 0.06). The results persisted when stratified by sex, duration of follow-up, and in most of the other subgroup analyses. There was no evidence of publication bias with Egger's test, p = 0.64 or by inspection of the funnel plots.

CONCLUSIONS

These results suggest that individuals with diabetes mellitus are at a reduced risk of abdominal aortic aneurysm, however, whether pharmacological agents for diabetes mellitus explain this observation needs to be clarified in future studies.

Diabetes Mellitus: Is It Protective against Aneurysm? A Narrative Review

Objectives: In the course of extensive clinical aortic surgery, we noticed that the aorta was quite thick and fibrotic in diabetic patients. We thought the diabetic aortic aorta might be inimitable to aortic dissection. On this basis, we set out to review information in the literature regarding aortic growth and dissection in diabetic patients. Methods: We used a 2-step search approach to the available literature on diabetes and aneurysm. Firstly, databases including PubMed, Cochrane, Embase and TRIP were searched. Secondly, relevant studies were identified through secondary sources including references of initially selected articles. We address the relationship between diabetes and the incidence, prevalence, growth, mortality and rupture of an aneurysm. Results: Diabetes is thought to exert a protective role in both thoracic aortic aneurysm (TAA) and abdominal aortic aneurysm (AAA). Diabetics were shown to have a slower aneurysm growth rate, lower rupture rate, delayed (> 65 years) age of rupture, decreased rate of mortality from an aneurysm and a decreased length of hospital stay. There was also noted a decreased rate of incidence and prevalence of TAA and AAA in diabetics, smaller aneurysm diameter, reduction in matrix metalloproteinases and an increased aortic wall stress in diabetics. Antidiabetic agents like metformin, thiazolidinediones and dipeptidyl peptidase-4 inhibitors may protect against an aneurysm. Conclusion: Our literature review provides strong (but often circumstantial) evidence that diabetic patients exhibit slower growth of aortic aneurysms and a lower rate of aortic dissection. Furthermore, clinical and experimental studies indicate that common antidiabetic medications on their own inhibit growth of aortic aneurysms. These findings indicate a paradoxically beneficial effect of the otherwise highly detrimental diabetic state.

Diabetes mellitus and abdominal aortic aneurysms: A review of the mechanisms underlying the negative relationship

INTRODUCTION

Diabetes mellitus appears to be negatively associated with abdominal aortic aneurysm; however, the mechanisms underlying this relationship remain poorly understood. The aim of this article is to provide a comprehensive review of the currently understood biological pathways underlying this relationship.

METHODS

A review of the literature ('diabetes' OR 'hyperglycaemia' AND 'aneurysm') was performed and relevant studies grouped into biological pathways.

RESULTS

This review identified a number of biological pathways through which diabetes mellitus may limit the presence, growth and rupture of abdominal aortic aneurysms. These include those influencing extracellular matrix volume, extracellular matrix glycation, the formation of advanced glycation end-products, inflammation, oxidative stress and intraluminal thrombus biology. In addition, there is an increasing evidence to suggest that the medications used to treat diabetes can also limit the development and progression of abdominal aortic aneurysms.

CONCLUSION

The negative association between diabetes and abdominal aortic aneurysm is robust. Future studies should attempt to target the pathways identified in this review to develop novel therapeutic agents aimed at slowing or even halting aneurysm progression.

Glucagon-Like peptide-1: A new therapeutic target to treat abdominal aortic aneurysm?

Recent antidiabetic drugs including GLP-1 receptor agonists and DPP-IV inhibitors have demonstrated protective effects in several cardiovascular diseases but their effect in abdominal aortic aneurysm (AAA) is far less known. AAA can be associated with extremely high rates of mortality and pharmacological treatments are still lacking underlining the real need to identify new therapeutic targets. The aim of this review was to summarize current knowledge on the role of GLP-1 pathway in AAA. A systematic literature review was performed and 6 relevant studies (2 clinical and 4 experimental) were included. Experimental studies demonstrated a protective effect of both GLP-1 receptor agonists and DPP-IV inhibitors through targeting the main pathophysiological mechanisms underlying AAA formation. The effects of these drugs in human AAA are still poorly known. In the limelight of clinical and experimental studies, we discuss current limits and future directions.

Metformin does not reduce inflammation in diabetics with abdominal aortic aneurysm or at high risk of abdominal aortic aneurysm formation

INTRODUCTION

The protective effect of diabetes mellitus on abdominal aortic aneurysm formation and growth has been repeatedly observed in population studies but continues to be poorly understood. However, recent investigations have suggested that metformin, a staple antihyperglycemic medication, may be independently protective against abdominal aortic aneurysm formation and growth. Therefore, we describe the effect of metformin in abdominal aortic aneurysm and at-risk patients on markers of inflammation, the driver of early abdominal aortic aneurysm formation and growth.

METHODS

Peripheral blood was collected from patients previously diagnosed with abdominal aortic aneurysm or presenting for their U.S. Preventive Task Force-recommended abdominal aortic aneurysm screening. Plasma and circulating peripheral blood mononuclear cells were isolated using Ficoll density centrifugation. Circulating plasma inflammatory and regulatory cytokines were assessed with enzyme-linked immunosorbent assays. CD4⁺ cell phenotyping was performed using flow cytometric analysis and expressed as a proportion of total CD4⁺ cells. To determine the circulating antibody to self-antigen response, a modified enzyme-linked immunosorbent assay was performed against antibodies to collagen type V and elastin fragments.

RESULTS

Peripheral blood was isolated from 266 patients without diabetes mellitus ( n=182), with diabetes mellitus not treated with metformin ( n=34), and with diabetes mellitus actively taking metformin ( n=50) from 2015 to 2017. We found no differences in the expression of Tr1, Th17, and Treg CD4⁺ fractions within diabetics ± metformin. When comparing inflammatory cytokines, we detected no differences in IL-1β, IL-6, IL-17, IL-23, IFN-γ, and TNF-α. Conversely, no differences were observed pertaining to the expression to regulatory cytokines IL-4, IL-10, IL-13, TSG-6, or TGF-β. Lastly, no differences in expression of collagen type V and elastin fragment antigen and/or antibodies were detected with metformin use in diabetics.

CONCLUSION

Metformin in diabetics at-risk for abdominal aortic aneurysm or diagnosed with abdominal aortic aneurysm does not seem to alter the peripheral inflammatory environment.