APOE alleles are not associated with calcific aortic stenosis

Genetics of Calcific Aortic Stenosis: A Systematic Review

Background: Calcific aortic stenosis is the most prevalent valvular abnormality in the Western world. Factors commonly associated with calcific aortic stenosis include advanced age, male sex, hypertension, diabetes and impaired renal function. This review synthesises the existing literature on genetic associations with calcific aortic stenosis. Methods: A systematic search was conducted in the PubMed, Ovid and Cochrane libraries from inception to 21 July 2024 to identify human studies investigating the genetic factors involved in calcific aortic stenosis. From an initial pool of 1392 articles, 78 were selected for full-text review and 31 were included in the final qualitative synthesis. The risk of bias in these studies was assessed using the Newcastle Ottawa Scale. Results: Multiple genes have been associated with calcific aortic stenosis. These genes are involved in different biological pathways, including the lipid metabolism pathway (PLA, LDL, APO, PCSK9, Lp-PLA2, PONS1), the inflammatory pathway (IL-6, IL-10), the calcification pathway (PALMD, TEX41) and the endocrine pathway (PTH, VIT D, RUNX2, CACNA1C, ALPL). Additional genes such as NOTCH1, NAV1 and FADS1/2 influence different pathways. Mechanistically, these genes may promote a pro-inflammatory and pro-calcific environment in the aortic valve itself, leading to increased osteoblastic activity and subsequent calcific degeneration of the valve. Conclusions: Numerous genetic associations contribute to calcific aortic stenosis. Recognition of these associations can enhance risk stratification for individuals and their first-degree relatives, facilitate family screening, and importantly, pave the way for targeted therapeutic interventions focusing on the identified genetic factors. Understanding these genetic factors can also lead to gene therapy to prevent calcific aortic stenosis in the future.

Pilot candidate gene analysis of patients ≥ 60 years old with aortic stenosis involving a tricuspid aortic valve

The potential genetic basis of aortic stenosis in older people is poorly understood. A total of 265 patients with aortic stenosis involving tricuspid aortic valves and 961 controls were genotyped for ≤660 candidate single nucleotide polymorphisms (SNPs). After dividing the patients and controls into training and validation sets, we tested the correlation of the SNPs with the age-adjusted aortic valve area, determined by echocardiography or cardiac catheterization. A bootstrapped global p value of ≤0.005 was considered evidence of a possible significant correlation. The cases were aged 73 ± 7 years, and 72.7% were men. The median aortic valve area was 1.0 cm(2) (interquartile range 0.7 to 1.5). The controls were aged 69 ± 6 years, and 69.8% were men. The minor allele frequency was 21% ± 15% (37% <0.20). Three SNPs met the criteria for significant correlation (rs2276288 [MYO7A], p = 0.001; rs5194 [AGTR1], p = 0.004; rs207 307 [ELN], p = 0.005). Another 2 SNPs reached borderline significance (p ≤0.008). In conclusion, we report 3 SNPs to be associated with aortic stenosis involving tricuspid aortic valves in older subjects. Given the concerns regarding the problem of multiple statistical testing, validation studies are required to further assess these correlations.

Replication of genetic association studies in aortic stenosis in adults

Only a handful of studies have attempted to unravel the genetic architecture of calcific aortic valve stenosis (AS). The goal of this study was to validate genes previously associated with AS. Seven genes were assessed: APOB, APOE, CTGF, IL10, PTH, TGFB1, and VDR. Each gene was tested for a comprehensive set of single-nucleotide polymorphisms (SNPs). SNPs were genotyped in 457 patients who underwent surgical aortic valve replacement, and allele frequencies were compared to 3,294 controls. A missense mutation in the APOB gene was significantly associated with AS (rs1042031, E4181K, p = 0.00001). A second SNP located 5.6 kilobases downstream of the APOB stop codon was also associated with the disease (rs6725189, p = 0.000013). Six SNPs surrounding the IL10 locus were strongly associated with AS (0.02 > p > 6.2 × 10⁻¹¹). The most compelling association for IL10 was found with a promoter polymorphism (rs1800872) well known to regulate the production of the encoded anti-inflammatory cytokine. The frequency of the low-producing allele was greater in cases compared to controls (30% vs 20%, p = 6.2 × 10⁻¹¹). SNPs in PTH, TGFB1, and VDR had nominal p values <0.05 but did not resist Bonferroni correction. In conclusion, this study suggests that subjects carrying specific polymorphisms in the IL10 and APOB genes are at higher risk for developing AS.

Statins for calcific aortic valve stenosis: into oblivion after SALTIRE and SEAS? An extensive review from bench to bedside

Calcific aortic stenosis is the most frequent heart valve disease and the main indication for valve replacement in western countries. For centuries attributed to a passive wear and tear process, it is now recognized that aortic stenosis is an active inflammatory and potentially modifiable pathology, with similarities to atherosclerosis. Statins were first-line candidates for slowing down progression of the disease, as established drugs in primary and secondary cardiovascular prevention. Despite promising animal experiments and nonrandomized human trials, the prospective randomized trials SEAS and SALTIRE did not confirm the expected benefit. We review SEAS and SALTIRE starting with the preceding studies and discuss basic science experiments covering the major known contributors to the pathophysiology of calcific aortic valve disease, to conclude with a hypothesis on the absent effect of statins, and suggestions for further research paths.

Lipid-mediated inflammation and degeneration of bioprosthetic heart valves

BACKGROUND

The durability of bioprosthetic valves is limited by structural valve degeneration (SVD) leading to bioprostheses (BPs) stenosis or regurgitation. We hypothesized that a lipid-mediated inflammatory mechanism is involved in the SVD of BPs.

MATERIAL AND METHODS

Eighteen Freestyle stentless BP valves were explanted for SVD at a mean time of 5.9 +/- 3 years after implantation and were analysed by immunohistochemistry and transmission electron microscopy (TEM).

RESULTS

The mean age of the patients was 65 +/- 8 years and there were 11 male and seven female patients. Two of the 18 BPs had macroscopic calcification, whereas the other valves had minimal or no macroscopic calcification. Tears at the commissures leading to regurgitation was present in 16 BPs. Immunohistochemistry showed the presence of oxidized low-density lipoprotein (ox-LDL) and glycosaminoglycans in the fibrosa layer of 13 BPs. Areas with ox-LDL were infiltrated by macrophages (CD68(+)) co-expressing the scavenger receptor CD36 and metalloproteinase-9 (MMP-9). Zymogram showed the active form of MMP-9 within explanted BPs. EM studies revealed the presence of lipid-laden cells featuring foam cells and fragmented collagen. Nonimplanted control BPs obtained from the manufacturer (n = 4) had no evidence of lipid accumulation, inflammatory cell infiltration or expression of MMP9 within the leaflets.

CONCLUSIONS

These results support the concept that lipid-mediated inflammatory mechanisms may contribute to the SVD of BPs. These findings suggest that modification of atherosclerotic risk factors with the use of behavioural or pharmacological interventions could help to reduce the incidence of SVD.

Epidemiology and genetics of calcific aortic valve disease

Calcific aortic valve disease is a common condition in the elderly and is associated with significant morbidity and mortality. Although biologically plausible roles in disease pathogenesis have been proposed for both lipoproteins and the renin-angiotensin system, no properly controlled, randomized trials have demonstrated that any pharmacologic therapy slows development of the disease. This review defines the stages of calcific aortic valve disease; discusses the role of nonechocardiographic techniques, such as cardiac computed tomography, that may allow identification and study of earlier-stage disease; reviews associated epidemiologic factors; and summarizes recent studies of "novel" risk factors, such as metabolic syndrome and inflammatory biomarkers. Finally, the role of genetics in this disease is receiving greater attention, and recent studies are reviewed that examine genetic polymorphisms and identify single-gene defects associated with this disease. Together these latter sets of studies emphasize that unique "nonatherosclerotic" factors can influence calcific aortic valve disease development, suggesting the possibility of novel therapeutic strategies for this condition.

Aortic valve stenosis: an active atheroinflammatory process

PURPOSE OF REVIEW

To summarize the current understanding of the pathobiology of aortic valve stenosis and portray the major advances in this field.

RECENT FINDINGS

Stenotic aortic valves are characterized by atherosclerosis-like lesions, consisting of activated inflammatory cells, including T lymphocytes, macrophages, and mast cells, and of lipid deposits, calcific nodules, and bone tissue. Active mediators of calcification and cells with osteoblast-like activity are present in diseased valves. Extracellular matrix remodeling, including collagen synthesis and elastin degradation by matrix metalloproteinases and cathepsins, contributes to leaflet stiffening. In experimental animals, hypercholesterolemia induces calcification and bone formation in aortic valves, which can be inhibited by statin treatment. The potential of statins to retard progression of aortic valve stenosis has also been recognized in clinical studies; however, further prospective trials are needed. Angiotensin II-forming enzymes are upregulated in stenotic valves. Angiotensin II may participate in profibrotic progression of aortic valve stenosis and may serve as a possible therapeutic target.

SUMMARY

Recent findings regarding the interaction of inflammatory cells, lipids, mediators of calcification, and renin-angiotensin system in stenotic valves support the current opinion of aortic valve stenosis being an actively regulated disease, potentially amenable to targeted molecular therapy. Evidence from prospective clinical studies is eagerly awaited.

Genome-wide linkage mapping for valve calcification susceptibility loci in hypertensive sibships: the Hypertension Genetic Epidemiology Network Study

It remains unclear whether genetic factors contribute to the susceptibility to valve calcification. Accordingly, echocardiograms and genotyping were performed in 1871 hypertensive siblings who participated in the Hypertension Genetic Epidemiology Network Study. Genome-wide affected sibpair nonparametric linkage analysis was conducted using the allele-sharing method implemented in the Merlin computer program. A total of 1014 sibships from 858 families were evaluated for aortic valve sclerosis or mitral annular calcification. Of these, 78 sibships from 68 families contained > or =2 affected siblings with > or =1 type of valve calcification (142 affected siblings). All 3 of the traits showed a modest degree of familial aggregation, with sibling recurrence risk (SD) and sibling recurrence risk ratio (95% CI) being 0.25 (0.035) and 2.31 (1.72 to 3.11) for aortic valve sclerosis, 0.25 (0.035) and 1.78 (1.36 to 2.33) for mitral annular calcification, and 0.31 (0.030) and 1.52 (1.24 to 1.85) for aortic valve sclerosis and mitral annular calcification, respectively. Affected sibpair linkage analysis revealed the highest logarithm of odds score (3.14) in chromosome 16 at 105.6 cM for aortic valve sclerosis. Other chromosomal regions with logarithm of odds score > or =1.9 were found in chromosomes 19 (2.88), 16 (2.63), 1 (2.12), and 2 (2.03) for aortic valve sclerosis and chromosome 13 (2.12) for any valve calcification. There was no logarithm of odds score > or =1.9 for mitral annular calcification. Our study shows strong linkage of aortic valve sclerosis to chromosome 16q22.1-q22.3 and suggestive linkage to chromosome 19p13.11-p11 and identifies several other promising genomic regions that may contain specific susceptibility loci for valve calcification.