Genetic approach to the role of cysteine proteases in the expansion of abdominal aortic aneurysms

Comparison of Genes Associated with Thoracic and Abdominal Aortic Aneurysms

Aneurysms impacting the ascending thoracic aorta and the abdominal aorta affect patient populations with distinct clinical characteristics. Through a literature review, this paper compares the genetic associations of ascending thoracic aortic aneurysm (ATAA) with abdominal aortic aneurysms (AAA). Genes related to atherosclerosis, lipid metabolism, and tumor development are associated specifically with sporadic AAA, while genes controlling extracellular matrix (ECM) structure, ECM remodeling, and tumor growth factor β function are associated with both AAA and ATAA. Contractile element genes uniquely predispose to ATAA. Aside from known syndromic connective tissue disease and poly-aneurysmal syndromes (Marfan disease, Loeys-Dietz syndrome, and Ehlers-Danlos syndrome), there is only limited genetic overlap between AAA and ATAA. The rapid advances in genotyping and bioinformatics will elucidate further the various pathways associated with the development of aneurysms affecting various parts of the aorta.

Association Between Increased Levels of Cystatin C and the Development of Cardiovascular Events or Mortality: A Systematic Review and Meta-Analysis

BACKGROUND

Cystatin C seems promising for evaluating the risk of cardiovascular events and mortality.

OBJECTIVE

To evaluate the association between high levels of cystatin C and the development of cardiovascular events or mortality.

METHODS

The articles were selected in the Medline/PubMed, Web of Science, and Scielo databases. The eligibility criteria were prospective cohort observational trials that assessed the association of high serum levels of cystatin C with the development of cardiovascular events or mortality in individuals with normal renal function. Only studies that evaluated the mortality outcome compared the fourth with the first quartile of cystatin C and performed multivariate Cox's proportional hazard regression analysis were included in the meta-analysis. A p value < 0,05 was considered significant.

RESULTS

Among the 647 articles found, 12 were included in the systematic review and two in the meta-analysis. The risk of development of adverse outcomes was assessed by eight studies using the hazard ratio. Among them, six studies found an increased risk of cardiovascular events or mortality. The multivariate regression analysis was performed by six studies, and the risk of developing adverse outcomes remained significant after the analysis in four of these studies. The result of the meta-analysis [HR = 2.28 (1.70-3.05), p < 0.001] indicated that there is a significant association between high levels of cystatin C and the risk of mortality in individuals with normal renal function.

CONCLUSION

There is a significant association between high levels of cystatin C and the development of cardiovascular events or mortality in individuals with normal renal function.

Systematic Review of Circulating, Biomechanical, and Genetic Markers for the Prediction of Abdominal Aortic Aneurysm Growth and Rupture

BACKGROUND

The natural course of abdominal aortic aneurysms (AAA) is growth and rupture if left untreated. Numerous markers have been investigated; however, none are broadly acknowledged. Our aim was to identify potential prognostic markers for AAA growth and rupture.

METHODS AND RESULTS

Potential circulating, biomechanical, and genetic markers were studied. A comprehensive search was conducted in PubMed, Embase, and Cochrane Library in February 2017, following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Study selection, data extraction, and methodological quality assessment were conducted by 2 independent researchers. Plausibility of markers was based on the amount of publications regarding the marker (more than 3), pooled sample size (more than 100), bias risk and statistical significance of the studies. Eighty-two studies were included, which examined circulating (n=40), biomechanical (n=27), and genetic markers (n=7) and combinations of markers (n=8). Factors with an increased expansion risk included: AAA diameter (9 studies; n=1938; low bias risk), chlamydophila pneumonia (4 studies; n=311; medium bias risk), S-elastin peptides (3 studies; n=205; medium bias risk), fluorodeoxyglucose uptake (3 studies; n=104; medium bias risk), and intraluminal thrombus size (5 studies; n=758; medium bias risk). Factors with an increased rupture risk rupture included: peak wall stress (9 studies; n=579; medium bias risk) and AAA diameter (8 studies; n=354; medium bias risk). No meta-analysis was conducted because of clinical and methodological heterogeneity.

CONCLUSIONS

We identified 5 potential markers with a prognostic value for AAA growth and 2 for rupture. While interpreting these data, one must realize that conclusions are based on small sample sizes and clinical and methodological heterogeneity. Prospective and methodological consonant studies are strongly urged to further study these potential markers.

Association of different biomarkers of renal function with D-dimer levels in patients with type 1 diabetes mellitus (renal biomarkers and D-dimer in diabetes)

Objective This study aimed to evaluate the association between different renal biomarkers with D-Dimer levels in diabetes mellitus (DM1) patients group classified as: low D-Dimer levels (< 318 ng/mL), which included first and second D-Dimer tertiles, and high D-Dimer levels (≥ 318 ng/mL), which included third D-Dimer tertile. Materials and methods D-Dimer and cystatin C were measured by ELISA. Creatinine and urea were determined by enzymatic method. Estimated glomerular filtration rate (eGFR) was calculated using CKD-EPI equation. Albuminuria was assessed by immunoturbidimetry. Presence of renal disease was evaluated using each renal biomarker: creatinine, urea, cystatin C, eGFR and albuminuria. Bivariate logistic regression analysis was performed to assess which renal biomarkers are associated with high D-Dimer levels and odds ratio was calculated. After, multivariate logistic regression analysis was performed to assess which renal biomarkers are associated with high D-Dimer levels (after adjusting for sex and age) and odds ratio was calculated. Results Cystatin C presented a better association [OR of 9.8 (3.8-25.5)] with high D-Dimer levels than albuminuria, creatinine, eGFR and urea [OR of 5.3 (2.2-12.9), 8.4 (2.5-25.4), 9.1 (2.6-31.4) and 3.5 (1.4-8.4), respectively] after adjusting for sex and age. All biomarkers showed a good association with D-Dimer levels, and consequently, with hypercoagulability status, and cystatin C showed the best association among them. Conclusion Therefore, cystatin C might be useful to detect patients with incipient diabetic kidney disease that present an increased risk of cardiovascular disease, contributing to an early adoption of reno and cardioprotective therapies.

Arterial indices and serum cystatin C level in individuals with occupational wide band noise exposure

BACKGROUND

Chronic exposure to noise is known to cause a wide range of health problems including extracellular matrix (ECM) proliferation and involvement of cardiovascular system. There are a few studies to investigate noise-induced vascular changes using noninvasive methods. In this study we used carotid artery intima-media thickness (CIMT) and aortic augmentation as indices of arterial properties and cystatin C as a serum biomarker relating to ECM metabolism.

MATERIALS AND METHODS

Ninety-three male participants were included in this study from aeronautic technicians: 39 with and 54 without a history of wide band noise (WBN) exposure. For better discrimination, the participants were divided into the two age groups: <40 and >40 years old. Adjusted aortic augmentation index (AI) for a heart rate equal to 75 beats per minute (AIx@HR75) were calculated using pulse wave analysis (PWA). CIMT was measured in 54 participants who accepted to undergo Doppler ultrasonography. Serum cystatin C was also measured.

RESULTS

Among younger individuals the mean CIMT was 0.85 ± 0.09 mm and 0.75 ± 0.22 mm in the in the exposed and the control groups respectively. Among older individuals CIMT had a mean of 1.04 ± 0.22 mm vs. 1.00 ± 0.25 mm for the exposed vs. the control group. However, in both age groups the difference was not significant at the 0.05 level. A comparison of AIx@HR75 between exposure group and control group both in younger age group (5.46 ± 11.22 vs. 8.56 ± 8.66) and older age group (17.55 ± 10.07 vs. 16.61 ± 5.77) revealed no significant difference. We did not find any significant correlation between CIMT and AIx@HR75 in exposed group (r = 0.314, P value = 0.145) but the correlation was significant in control group (r = 0.455, P value = 0.019). Serum cystatin C level was significantly lower in individuals with WBN exposure compared to controls (441.10 ± 104.70 ng/L vs. 616.89 ± 136.14, P value < 0.001) both in younger and older groups.

CONCLUSION

We could not find any evidence for the association of WBN exposure with arterial properties, but cystatin C was significantly lower in the exposed group.

Abdominal Aortic Aneurysms and Risk Factors for Adverse Events

An abdominal aortic aneurysm (AAA) is a focal full thickness dilatation of the abdominal aorta, greater than 1.5 times its normal diameter. Although some patients with AAA experience back or abdominal pain, most remain asymptomatic until rupture. The prognosis after AAA rupture is poor. Management strategies for patients with asymptomatic AAAs include risk factor reduction, such as smoking cessation, optimizing antihypertensive treatment, and treating dyslipidemia, as well as surveillance by ultrasound. Currently, aneurysm diameter alone is often used to assess risk of rupture. Once the aneurysm diameter reaches 5.5 cm, the risk of rupture is considered greater than the risk of intervention and elective aneurysm repair is undertaken. There is increasing interest in detecting AAAs early, and national screening programs are now in place. Furthermore, there is increasing research interest in biomarkers, genetics, and functional imaging to improve detection of AAAs at risk of progression and rupture. In this review, we discuss risk factors for AAA rupture, which should be considered during the management process, to advance current deficiencies in management pathways.

The potential of Cystatin C and small dense LDL as biomarkers of coronary artery disease risk in a young Indian population

Coronary artery disease (CAD) affects Indians 5-6 years earlier than in the west, is diffuse and malignant, and poses a heavy burden on India's developing economy. Traditional risk factors have failed to explain this high incidence of premature CAD and hence this study investigated the association of two novel risk biomarkers, cystatin C and small dense LDL (sdLDL) with the presence and severity of CAD. Cystatin C and sdLDL were estimated in 204 CAD patients ≤45 years of age and compared with 161 age-matched healthy controls. The traditional lipid profile parameters, i.e., cholesterol, LDL, HDL, triglycerides, apolipoproteins A1 and B, and Lp(a) were also measured in both groups. Cystatin C was significantly raised and mean LDL particle size significantly reduced in CAD patients as compared to controls. 62.7 % of CAD patients showed pattern B while 37.3 % patients showed pattern A. Of the traditional lipid tests, only HDL and apolipoprotein A1 showed a significant decrease in the CAD group. sdLDL was significantly associated with the severity of CAD, while cystatin C was not. Both cystatin C and sdLDL emerged as independent risk factors, however, of the two, sdLDL was a more sensitive predictor of CAD events. Cystatin C and mean LDL particle size are significantly and independently associated with the presence of CAD events in patients ≤45 years with normal kidney function. Hence, these novel risk biomarkers can be useful tools in reducing the morbidity and mortality associated with CAD in the productive Indian workforce.

How to understand the association between cystatin C levels and cardiovascular disease: Imbalance, counterbalance, or consequence?

The association of cystatin C with renal function has been studied for more than 25 years. Cystatin C has been described to have a better diagnostic performance than creatinine to assess renal function, particularly to detect small reductions in glomerular filtration rate. Recently, cystatin C has emerged as a strong predictor of incident or recurrent cardiovascular events and adverse outcomes in patients without kidney disease. Furthermore, it has been suggested that cystatin C concentrations are directly related to both inflammation and atherosclerosis. Nevertheless, the link between inflammation, atherogenesis, cardiovascular risk, and cystatin C is still poorly understood. This brief report discusses recent data, contrasting findings and possible mechanisms involved in this interaction.

Plasma cathepsin S and cystatin C levels and risk of abdominal aortic aneurysm: a randomized population-based study

BACKGROUND

Human abdominal aortic aneurysm (AAA) lesions contain high levels of cathepsin S (CatS), but are deficient in its inhibitor, cystatin C. Whether plasma CatS and cystatin C levels are also altered in AAA patients remains unknown.

METHODS AND RESULTS

Plasma samples were collected from 476 male AAA patients and 200 age-matched male controls to determine CatS and cystatin C levels by ELISA. Student's t test demonstrated higher plasma levels of total, active, and pro-CatS in AAA patients than in controls (P<0.001). ROC curve analysis confirmed higher plasma total, active, and pro-CatS levels in AAA patients than in controls (P<0.001). Logistic regression suggested that plasma total (odds ratio [OR] = 1.332), active (OR = 1.21), and pro-CatS (OR = 1.25) levels were independent AAA risk factors that associated positively with AAA (P<0.001). Plasma cystatin C levels associated significantly, but negatively, with AAA (OR = 0.356, P<0.001). Univariate correlation demonstrated that plasma total and active CatS levels correlated positively with body-mass index, diastolic blood pressure, and aortic diameter, but negatively with the lowest ankle-brachial index (ABI). Plasma cystatin C levels also correlated negatively with the lowest ABI. Multivariate linear regression showed that plasma total, active, and pro-CatS levels correlated positively with aortic diameter and negatively with the lowest ABI, whereas plasma cystatin C levels correlated negatively with aortic diameter and the lowest ABI, after adjusting for common AAA risk factors.

CONCLUSIONS

Correlation of plasma CatS and cystatin C with aortic diameter and the lowest ABI suggest these serological parameters as biomarkers for human peripheral arterial diseases and AAA.

Genes and abdominal aortic aneurysm

Abdominal aortic aneurysm (AAA) is a multifactorial disease with a strong genetic component. Since the first candidate gene studies were published 20 years ago, approximately 100 genetic association studies using single nucleotide polymorphisms (SNPs) in biologically relevant genes have been reported on AAA. These studies investigated SNPs in genes of the extracellular matrix, the cardiovascular system, the immune system, and signaling pathways. Very few studies were large enough to draw firm conclusions and very few results could be replicated in another sample set. The more recent unbiased approaches are family-based DNA linkage studies and genome-wide genetic association studies, which have the potential of identifying the genetic basis for AAA, only when appropriately powered and well-characterized large AAA cohorts are used. SNPs associated with AAA have already been identified in these large multicenter studies. One significant association was of a variant in a gene called contactin-3, which is located on chromosome 3p12.3. However, two follow-up studies could not replicate this association. Two other SNPs, which are located on chromosome 9p21 and 9q33, were replicated in other samples. The two genes with the strongest supporting evidence of contribution to the genetic risk for AAA are the CDKN2BAS gene, also known as ANRIL, which encodes an antisense ribonucleic acid that regulates expression of the cyclin-dependent kinase inhibitors CDKN2A and CDKN2B, and DAB2IP, which encodes an inhibitor of cell growth and survival. Functional studies are now needed to establish the mechanisms by which these genes contribute toward AAA pathogenesis.

Cystatin C: a better marker to detect coronary artery sclerosis

BACKGROUND

Nowadays, early detection and treatment can often keep chronic kidney disease patients from getting worse and prevent the occurrence of cardiovascular disease. Cystatin C (Cys-C) is a new marker for renal dysfunction. This study investigated whether Cys-C played an important role for screening coronary artery disease.

METHODS

The consecutive 88 outpatients (51 males and 37 females), who were suspected of having effort angina pectoris or asymptomatic ischemic heart disease, were enrolled. Serum Cys-C, which was obtained within 3 months before coronary angiography, was assessed with the presence or absence of coronary arteriosclerosis, the number of culprit arteries, and blood biochemical parameters.

RESULTS

Mean serum Cys-C was 0.82+/-0.29 mg/l. Significant differences in the estimated creatinine clearance (p=0.036), hemoglobin A1c (p=0.01), left ventricular ejection fraction (p=0.01), creatinine (p=0.007), Cys-C (p=0.006), and high-density lipoprotein (HDL) cholesterol (p=0.001) were observed between the patients with or without coronary arteriosclerosis. Serum Cys-C was significantly greater in the multi-vessel disease (MVD) group than the 0 vessel disease (0VD) group (p<0.001). HDL cholesterol was significantly lower in the MVD group than the 0VD and single-vessel disease groups (p=0.002 and p=0.005, respectively).

CONCLUSION

The results of this study suggest Cys-C might be one of the risk factors for coronary arteriosclerosis in the patients with suspected ischemic heart disease without any history of coronary artery disease. Cys-C was a useful marker to detect coronary artery disease and the level of Cys-C could reflect the severity of coronary arteriosclerosis.

Growth predictors and prognosis of small abdominal aortic aneurysms

OBJECTIVE

Evidence regarding the influence of cardiovascular risk factors, comorbidities, and patient characteristics on the growth of small abdominal aortic aneurysms (AAA) is limited. We assessed, in an observational cohort study, rupture rates, risks of mortality, and the effects of cardiovascular risk factors and patient demographics on growth rates of small AAAs.

METHODS

Between September 1996 and January 2005, 5057 patients with manifest arterial vascular disease or cardiovascular risk factors were included in the Second Manifestation of ARTerial disease (SMART) study. Measurements of the abdominal aortic diameter were performed in all patients. All patients with an initial AAA diameter between 30 and 55 mm were selected for this study. All AAA measurements during follow-up until August 2007 were collected. Multivariate regression analysis was performed to calculate the effects of demographic patient characteristics, initial AAA diameter, and cardiovascular risk factors on AAA growth.

RESULTS

Included were 230 patients, with a mean age of 66 years and 90% were male. Seven AAA ruptures (six fatal) occurred in 755 patient years of follow-up (rupture rate 0.9% per patient-year). In 147 patients, AAA measurements were performed for a period of more than 6 months. The median follow-up time was 3.3 years (mean 4.0, range 0.5 to 11.1 years, standard deviation (SD) 2.5). Mean AAA diameter was 38.8 mm (SD 6.8) and mean expansion rate 2.5 mm/y. Patients using lipid-lowering drugs had a 1.2 mm/y (95% confidence interval [CI] -2.34 to -0.060 mm/y) lower AAA growth rate compared to nonusers of these drugs. Initial AAA diameter was associated with a 0.09 mm/y (95% CI 0.01 to 0.18 mm/y) higher growth rate per millimetre increase of the diameter. No other factors, including blood lipid values, were independently associated with AAA growth.

CONCLUSIONS

Lipid-lowering drug treatment and initial AAA diameter appear to be independently associated with lower AAA growth rates. The risk of rupture of these small abdominal aortic aneurysms was low, which pleads for watchful waiting.

Effect of statins on proteolytic activity in the wall of abdominal aortic aneurysms

BACKGROUND

The aim of this study was to examine the effect of statin treatment on the activity of proteases in the wall of abdominal aortic aneurysms (AAAs).

METHODS

The activities of matrix metalloproteinases (MMPs) 9 and 3, cathepsins B, H, K, L and S, and the cystatin C level were measured in extracts of AAA wall taken from 82 patients undergoing AAA repair; 21 patients were receiving statin treatment before surgery. All values were standardized against soluble protein (SP) concentration in the extract, and reported as median (interquartile range) or mean(s.e.m.).

RESULTS

The two groups had similar demographics. Reduced activity of MMP-9 (43 (34-56) versus 80 (62-110) pg per mg SP; P < 0.001), cathepsin H (183 (117-366) versus 321 (172-644) nmol 4-methylcoumarin-7-amide released per mg SP; P = 0.016) and cathepsin L (102 (51-372) versus 287 (112-816) micromol 7-amino-4-trifluoromethylcoumarin released per mg SP; P = 0.020) was found in the statin-treated aortas compared with AAAs from patients not taking a statin. The statin-treated group had lower MMP-3 activity, but this did not reach statistical significance (P = 0.053). Cystatin C levels were higher in statin-treated aortas than in controls (41.3(3.1) versus 28.9(2.1) ng per mg SP; P = 0.003).

CONCLUSION

Statins decreased the activity of proteases that have been implicated in aneurysm disease.

Cysteine protease activity in the wall of abdominal aortic aneurysms

BACKGROUND

Cysteine proteases are potent elastolytic enzymes and together with their inhibitor, cystatin C, have been linked with the growth of abdominal aortic aneurysms (AAAs). These enzymes and their inhibitors have previously been studied in AAAs, but comparisons have always been made with wall from normal aorta. Atherosclerosis is a feature of aneurysmal disease and may therefore confound comparisons with normal wall. This study compared the expression and activity of cysteine proteases and their inhibitors in aneurysm wall with their expression in the aortic wall of patients with aortic occlusive disease (AOD).

METHODS

Aortic wall was obtained from 82 patients with AAA and 13 with AOD. Protein expression and activity of cathepsin B, H, K, L and S, and cystatins A, B, and C were measured by enzyme-linked immunosorbent assay and specific fluorogenic substrate assays. Matrix metalloproteinase 9 (MMP-9) activity was measured by quantitative bioimmunoassay in the same extracts.

RESULTS

AAA wall had 330% more cathepsin H protein (P = .007) and >30% less cystatin C (P = .03) than the aortic wall from patients with AOD. The activity of cathepsins B, H, L, and S was significantly greater in AAA than AOD (376%, [P < .0001], 191%, [P = 0.019], 223%, P = 0.002, and approximately 20% [P = 0.045] respectively). MMP-9 activity was also increased in AAA compared with AOD (P<0.0001) and levels in the wall of AAA correlated positively with cathepsin L activity (r = 0.42, P<.0001) and negatively with cystatin C (r = -0.75, P<.0001).

CONCLUSIONS

The activity of four cathepsins B, H, L, and S was higher in the aneurysm wall than in aortic wall of patients with occlusive disease. This was associated with a reduced level of cystatin C in the aneurysmal wall. Cathepsin H was the only protein in which there was a correlation between protein level and activity, which suggests that post-translational modifications were responsible for activation of the other cathepsins. Increased cathepsin activity may influence the activity of MMP-9, which is thought to have an important role in aneurysm development.

Do cathepsins play a role in abdominal aortic aneurysm pathogenesis?

Between 1998 and 1999 we suggested a role for cysteine proteases, particularly cathepsins S and K, in atherosclerosis and abdominal aortic aneurysm (AAA) formation. We also demonstrated the presence and activity of cathepsins S, K, and L in atherosclerotic and aneurysmal lesions in humans. Features unique to this family of extracellular enzymes indicate its likely participation in these vascular diseases. As very potent elastolytic enzymes, cathepsins are strong candidates as key participants in aneurysm development. Importantly, cathepsins express very high elastolytic activity in AAA due to reciprocal correlation with cystatin C, their most abundant endogenous inhibitor. Two opposite processes coexist in aneurysmal tissue: overexpression of elastolytic cathepsins, and severe suppression of cystatin C, probably due to differentially regulated expression and secretion of cathepsins and their inhibitors in response to inflammatory cytokines. Involvement of cathepsins in microvessel formation, a pathophysiological marker of human AAA, and programmed cell death (apoptosis), increases the likelihood of cathepsin participation in AAA formation and growth. We also summarize here results obtained in our and other laboratories that demonstrated reduced atherosclerosis and AAA in in vivo models using mice lacking different cathepsins. Deficiency of cysteine protease inhibitor cystatin C in atherosclerosis-prone ApoE-null mice leads to the development of specific features of AAA such as thinning of the tunica media and aortic dilatation. Taken together, such findings in humans in vitro with different cell types and in vivo in genetically altered mice demonstrate the importance of cysteine protease/protease inhibitor balance in dysregulated arterial integrity and remodeling during atherosclerosis and aortic aneurysm formation.

Proteinase systems and thoracic aortic aneurysm progression

Thoracic aortic aneurysms (TAAs) are a rare but potentially devastating condition. Current surgical treatment of TAAs usually involves a major operation, which conveys many risks to the patient. Better knowledge of the cellular events that lead to aneurysm formation may elucidate less morbid treatment options for this condition. A number of recent studies have identified that the relative abundance and activity of extracellular matrix (ECM) proteolytic systems are increased with TAAs. Specifically, the matrix metalloproteinases (MMPs) have been linked through numerous studies to TAA formation. MMPs comprise a family of ECM-degrading proteinases. Endogenous tissue inhibitors (TIMPs) normally regulate MMP activity, and the activation of MMPs is complex and tightly controlled. Aneurysm formation may be related to relative changes in the balance between MMP/TIMP abundance favoring proteolysis. Through ECM degradation, the medial layer will undergo structural remodeling and a loss of structural integrity, leading to TAA formation. The goals of this review are to examine the structure of the normal and aneurysmal thoracic aorta and to place the new findings regarding ECM proteolysis in perspective with regard to TAA formation and progression. Through an integration of basic and clinical studies regarding the underlying molecular basis for proteolysis of the thoracic aorta, improved diagnostic, prognostic, and therapeutic strategies for this disease process are likely to be realized.

Smoking and Aortic Diseases

Cigarette smoking is a major vascular risk factor and in this context, it is an independent risk factor for the development of aortic disease, especially the formation and growth of abdominal aortic aneurysms (AAA). Medline was searched up to January 31, 2007 for the relevant literature for this review of the mechanisms by which smoking causes aortic wall damage and its subsequent impact on the clinical manifestation of this process. Idiopathic AAAs and aortic dissection are considered, as well as other aortic diseases (eg, Takayasu, Kawasaki, Behcet and Buerger). There is evidence suggesting an abnormal homeostasis between proteolytic and antiproteolytic activity in the vascular wall during the development of AAAs, and these mechanisms can be influenced by smoking. Smoking cessation plays an important role in the management of aortic disease.

Abdominal aortic aneurysm: pathogenesis and implications for management

Abdominal aortic aneurysm (AAA) affects approximately 5% of elderly men and is responsible for a significant number of deaths in Western Countries. At present surgery by open or endovascular means is the only widely used therapy for this condition. In this review we examine the risk factors, serum, and genetic associations of AAA. Epidemiology studies suggest that smoking cessation and control of cholesterol and blood pressure should reduce the number of patients developing AAA. Natural history studies suggest that smoking cessation should reduce the rate of progression of AAA. Clear level 1 evidence for drug treatments of AAA are presently lacking; however, animal and human in vitro studies suggest that medication targeted at reducing inflammation and proteolysis are most likely to be beneficial, with limited data to support the use of statins, Angiotensin II inhibitors, and macrolides. Work has commenced in understanding which patients, identified by clinical, serum, and genotype, are more at risk of AAA progression and thus should be selected out for aggressive treatment. Well designed large multicenter randomized controlled trials are required to examine the medical treatment of AAA.

Cystatin C, kidney function and cardiovascular disease

Cystatin C, an endogenous low-molecular-weight marker of glomerular filtration rate, has recently been shown to be associated with future cardiovascular disease in healthy elderly populations and patients with documented atherosclerosis in a dose-dependent manner that possibly reflects a very early stage of chronic renal dysfunction. At the same time, local cystatin C deficiency has been demonstrated in atherosclerotic and aneurismal lesions, suggesting a protective role of cystatin C in the vessel wall, possibly in concert with TGF-beta1. Although cystatin C is not an acute phase reactant, large epidemiological studies have documented a highly significant association between serum cystatin C and mildly increased C-reactive protein (CRP) levels, the hallmark of the chronic inflammatory state associated with atherosclerosis and chronic renal failure. Since cystatin C is produced by all nucleated cells, it is unlikely that local variations in cystatin C synthesis in diseased arteries--rather than global cystatin C production and renal elimination--should determine its serum concentration. Consequently, the present review proposes microinflammation as the unifying concept for both lines of evidence.

Abdominal aortic aneurysm

Abdominal aortic aneurysms cause 1.3% of all deaths among men aged 65-85 years in developed countries. These aneurysms are typically asymptomatic until the catastrophic event of rupture. Repair of large or symptomatic aneurysms by open surgery or endovascular repair is recommended, whereas repair of small abdominal aortic aneurysms does not provide a significant benefit. Abdominal aortic aneurysm is linked to the degradation of the elastic media of the atheromatous aorta. An inflammatory cell infiltrate, neovascularisation, and production and activation of various proteases and cytokines contribute to the development of this disorder, although the underlying mechanisms are unknown. In this Seminar, we aim to provide an updated review of the pathophysiology, current and new diagnostic procedures, assessment, and treatment of abdominal aortic aneurysm to provide family practitioners with a working knowledge of this disorder.