Highlight
- Lipoprotein(a) [Lp(a)] elevation is a well-known risk factor for coronary artery disease (CAD) and aortic valve stenosis (AS), but risk varies widely across individuals.
- Interleukin 6 (IL-6), an inflammatory cytokine, significantly modifies the risk of incident CAD associated with high Lp(a) levels.
- Elevated IL-6 amplifies Lp(a)-related CAD risk, whereas lower IL-6 concentrations attenuate this association.
- No significant interaction between inflammatory markers and Lp(a) levels was found for risk of AS, suggesting divergent pathophysiological mechanisms.
Study Background
Lipoprotein(a), a genetically determined lipoprotein particle distinct from low-density lipoprotein, has been established as an independent risk factor for cardiovascular disease, particularly coronary artery disease and aortic valve stenosis. However, the clinical expression of risk associated with elevated Lp(a) is heterogeneous—some individuals with high Lp(a) develop cardiovascular events, while others remain event-free. This variability has led to investigation of potential modifiers, among which low-grade systemic inflammation has been proposed as a plausible factor. Prior research exploring inflammatory biomarkers such as interleukins and leukocyte ratios have yielded conflicting results regarding their role in modulating Lp(a)-related cardiovascular risk. Understanding this interplay may refine risk stratification and inform targeted prevention in primary care populations.
Study Design
This epidemiological study leveraged data from the UK Biobank, a large population-based cohort containing extensive biomarker and clinical outcome data. Participants were recruited between 2006 and 2010, inclusive of 43,512 adults without prior coronary artery disease or aortic valve stenosis at baseline who underwent plasma proteomic profiling. Lp(a) levels were categorized as high (≥125 nmol/L) or low (<125 nmol/L). Concurrent inflammatory biomarkers assayed included interleukin-1β (IL-1β), interleukin-18 (IL-18), interleukin-6 (IL-6), and the neutrophil-to-lymphocyte ratio (NLR). The primary outcome was incident coronary artery disease (CAD), and the secondary outcome was incident aortic valve stenosis (AS), both assessed over a median 13.5-year follow-up. Cox proportional hazards models adjusted for traditional cardiovascular risk factors evaluated the interaction between Lp(a) and inflammation markers.
Key Findings
Among the cohort, 16% had elevated Lp(a) levels (≥125 nmol/L), with a mean age of 56.5 years and a female majority (55.3%). Over follow-up, the risk of incident CAD was delineated according to Lp(a) level and inflammatory status.
IL-6 emerged as the most robust inflammatory biomarker modifying Lp(a)-associated CAD risk. Specifically, in the highest quartile of IL-6, individuals with elevated Lp(a) had a significantly increased hazard ratio (HR) of 1.43 (95% CI, 1.25–1.63) for incident CAD compared to those with lower Lp(a). In contrast, among those in the lowest IL-6 quartile, the HR was reduced to 1.09 (95% CI, 0.85–1.38), indicating attenuation of risk (P for interaction = .008). This interaction supports a synergistic effect of systemic inflammation and Lp(a) on coronary atherosclerosis progression.
The neutrophil-to-lymphocyte ratio also showed a suggestive interaction with Lp(a) (P = .02); however, significance was lost after correction for multiple comparisons, indicating weaker evidence for this biomarker.
No interactions were observed between Lp(a) levels and any inflammatory biomarkers regarding the risk of incident aortic valve stenosis. This suggests that the pathogenesis of AS may be less influenced by systemic inflammatory milieu or that other specific inflammatory pathways might be involved.
Expert Commentary
These findings shed light on the biological interplay between lipoprotein(a) and systemic inflammation in augmenting coronary artery disease risk. IL-6, a central mediator of inflammation, is well known to influence atherogenesis through modulation of endothelial dysfunction, monocyte recruitment, and plaque instability. The observed modification of Lp(a) risk by IL-6 aligns with mechanistic studies implicating inflammation as a crucial accelerator of lipid-driven atherosclerosis.
Clinically, measuring IL-6 could refine cardiovascular risk stratification within patients exhibiting elevated Lp(a), guiding more personalized preventive interventions. Inflammation-targeted therapies, such as IL-6 receptor antagonists, may have a potential role in mitigating the heightened risk in this subgroup, although prospective trials are needed.
The lack of interaction between inflammation and Lp(a) for aortic valve stenosis underscores the distinct pathophysiology of valvular calcification compared to coronary atheroma. It raises questions about the differential contribution of immune mechanisms in valve versus vascular disease.
Limitations include the observational design, which precludes causal inference, and potential confounding by unmeasured variables. The study population, predominantly middle-aged UK adults, may limit generalizability to other ethnicities or older individuals. Proteomic profiling measured a subset of interleukins; other inflammatory pathways may also be relevant.
Conclusion
This landmark cohort study demonstrates that interleukin-6 levels significantly modify the coronary artery disease risk associated with elevated lipoprotein(a) in a large primary prevention population. The synergy between Lp(a) and systemic inflammation offers an important insight into heterogeneous cardiovascular risk and identifies IL-6 as a potential biomarker for refined risk stratification and therapeutic targeting. Future research should focus on interventional trials to evaluate whether inflammation reduction can mitigate Lp(a)-mediated atherothrombotic risk and explore the mechanistic basis behind non-significant interaction in aortic valve stenosis.
Funding and ClinicalTrials.gov
Information on funding sources was not detailed in the abstract. No clinical trial registration was noted as this was an observational cohort analysis.
References
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5. UK Biobank Coordinating Centre. UK Biobank protocol. 2014. https://www.ukbiobank.ac.uk/media/gnkeyh2q/study-rationale.pdf