Your Gut Diseases May Be Quietly Raising Your Heart Attack Risk, New Genetics Study Finds

Digestive diseases and cardiovascular diseases have long been treated as separate medical territories, but a growing body of genetic evidence suggests the boundary between them is far more porous than clinicians assumed. A new study published in the International Journal of Surgery by J J Li and colleagues mapped the shared genetic architecture across 20 digestive diseases and 29 cardiovascular conditions, and the connections they uncovered carry real clinical weight. The findings are emerging rather than definitive, but the scale and rigor of the analysis make them difficult to dismiss.

Ulcerative Colitis, Acute Appendicitis, and Gallstones Linked to Heart Risk

Three digestive diseases stood out in the causal analysis. Ulcerative colitis was associated with a roughly fourfold-higher odds of atrioventricular block, the heart rhythm disorder involving disrupted electrical signaling between the upper and lower chambers, and also raised the risk of deep vein thrombosis in the lower extremities. Acute appendicitis showed the broadest cardiovascular footprint: a causal association with heart failure (effect size β = 0.13), ischemic stroke (β = 0.16), and stroke overall (β = 0.14). Cholelithiasis, better known as gallstones, produced the study's most counterintuitive result, appearing to protect against coronary artery disease (β = −0.05). Earlier research linking genetic susceptibility to GI and heart disease had flagged similar directional associations, but this study pushes the resolution considerably higher by identifying the specific genes involved.

Why These Associations Matter for Cardiovascular Risk Management

In 2019, digestive diseases accounted for roughly one-third of all prevalent disease cases globally, and cardiovascular disease killed at a rate of 235.2 per 100,000 people in 2021. If a substantial fraction of patients with common gut conditions carry elevated heart risk encoded in their DNA, that changes the calculus for screening and early intervention. Inflammatory bowel disease was already known to raise risks of deep vein thrombosis, stroke, and ischemic heart disease through inflammatory pathways. Prior Mendelian randomization work found that GERD treatment may help prevent common CVD events, and the new study extends that logic by showing the genetic underpinning of multiple gut-heart connections is real, not just a confounding artifact of shared lifestyle or comorbidities. For clinicians managing patients with ulcerative colitis or recurrent appendicitis, these data suggest that cardiovascular surveillance deserves a place in the care pathway.

How the Team Mapped Genetic Overlap Across 49 Disease Combinations

The study assembled GWAS datasets from large international consortia including FinnGen, CARDIoGRAMplusC4D, the MEGASTROKE consortium, and the Atrial Fibrillation Consortium. Genome-wide association studies scan hundreds of thousands of genetic markers across large populations to find variants tied to disease, and the team layered multiple analytical approaches on top of the raw GWAS data. Linkage disequilibrium score regression and a method called generalized pleiotropic analysis identified 119 and 301 trait pairs, respectively, with statistically meaningful genetic correlations or overlaps. Polygenic risk score analysis in 407,026 UK Biobank participants followed for a median of 8.79 years confirmed 30 gut-heart pairs with positive associations at genome-wide significance. To move from correlation to causation, the researchers applied five Mendelian randomization methods, including inverse variance weighted and MR-Egger, a strategy that uses genetic variants as natural experiments to test whether one trait actually influences another. Prior Mendelian randomization work on gut microbiome and cardiovascular disease used similar two-sample approaches, but this study spans a far broader set of disease pairings simultaneously.

The Specific Genes Bridging Gut and Heart

Pinpointing the biological mechanism is where the study makes its most granular contribution. The gene LTBR, which encodes a receptor involved in inflammation signaling and is expressed in cardiac, vascular, gastrointestinal, and haematological tissues, emerged as a key connector between acute appendicitis and its cardiovascular sequelae including heart failure, ischemic stroke, and stroke. The implication is that appendicitis-related inflammation may propagate cardiovascular harm through this shared gene. For the ulcerative colitis and atrioventricular block pairing, two genes drove the signal: GNA12, expressed in cardiac and intestinal tissue and linked to electrophysiologic pathways, and SMAD3, a regulator of inflammatory signaling. The cholelithiasis-coronary artery disease protective association traced to ABCG5 and ABCG8, cholesterol transporter genes already recognized as gallstone susceptibility factors that also attenuate diet-induced hypercholesterolemia and appear to protect against myocardial infarction. Multi-trait GWAS analysis further identified hundreds of novel risk SNPs, including 339 for the cholelithiasis and coronary artery disease pair and 49 for the acute appendicitis and heart failure pair, providing a starting point for deeper functional work.

Open Questions About Causality and Generalizability

The authors are explicit about what the analysis cannot yet establish. Mendelian randomization points toward potential causality rather than confirming it; residual pleiotropy, where one gene influences multiple traits through independent pathways, remains a possible confounder. The UK Biobank cohort is predominantly of White European ancestry, limiting how far these results generalize to other populations. Disease ascertainment relied on ICD-10 codes, which can miss early or subclinical cases and introduce misclassification. Several key covariates were measured only at baseline despite being time-varying. Separately, while gut microbiome research has flagged unclear causality in cardiovascular outcomes, the genetic signals identified here operate upstream of the microbiome and involve heritable variants, which strengthens the causal inference somewhat, but replication in multi-ancestry cohorts with stronger instruments is still needed.

What Comes Next for Gut-Heart Genetics

The identified genes, particularly LTBR, ABCG5/8, GNA12, and SMAD3, are now candidate targets for experimental work and, potentially, therapeutic intervention. Research into shared genetic architecture across autoimmune and cardiovascular diseases has already demonstrated that cross-disease genetic mapping can accelerate drug target discovery, and the same logic applies here. The novel SNPs catalogued in this study offer a roadmap for functional genomics studies aimed at understanding exactly how, for instance, appendicitis-associated inflammation translates into lasting cardiovascular vulnerability. Clinically, if these findings replicate, they argue for integrating polygenic cardiovascular risk scores into the routine management of patients with common gut diseases, shifting care from reactive treatment to earlier, genetically informed prevention.

Evidence rating

EMERGING — 86/100

Caveats:

• Mendelian randomization suggests causal direction but cannot establish definitive proof — residual confounding and horizontal pleiotropy remain possible.
• Participants were predominantly of White European ancestry, limiting generalizability to other populations.
• Funding source was not disclosed by the authors.
• Several findings diverge from prior studies and have not yet been independently replicated.

Large-scale multi-method genomic analysis drawing on GWAS data from hundreds of thousands of participants and UK Biobank prospective follow-up (n=407,026). Mendelian randomization supports causal inference over simple association, but MR estimates remain probabilistic and are subject to pleiotropy, weak instrument bias, and potential sample overlap. Findings have not yet been independently replicated and are derived from a predominantly White European ancestry population, limiting broader generalizability.

References

1. Jiaqi Li, Haoyang Zhang, Jieyi Chen, et al. (2026). Investigating the shared genetic architecture between digestive diseases and cardiovascular diseases. International Journal of Surgery. https://doi.org/10.1097/js9.0000000000005025
2. Zhuoxi Wang, Jifang Ban, Yabin Zhou, Rui Qie (2024). Causal association between gastrointestinal diseases and coronary artery disease: a bidirectional Mendelian randomization study. Frontiers in Endocrinology. https://doi.org/10.3389/fendo.2024.1458196
3. A Mendelian randomization study to assess the genetic liability of gastroesophageal reflux disease for cardiovascular diseases and risk factors – PubMed. academic.oup.com. https://academic.oup.com/hmg/article/31/24/4275/6873559
4. Genome-Wide Association Studies Fact Sheet. genome.gov. https://www.genome.gov/about-genomics/fact-sheets/Genome-Wide-Association-Studies-Fact-Sheet
5. Yuxuan Zhang, Xinyi Zhang, Delong Chen, et al. (2022). Causal associations between gut microbiome and cardiovascular disease: A Mendelian randomization study. Frontiers in Cardiovascular Medicine. https://doi.org/10.3389/fcvm.2022.971376
6. Understanding How the Gut Microbiome Affects Heart Health – CVRTI. cvrti.utah.edu. https://cvrti.utah.edu/understanding-how-the-gut-microbiome-affects-heart-health/
7. Jie Zhang, Xinyu Fang, Qianling Ye, Xianyong Yin, Dongqing Ye (2026). The shared genetic architecture underlying the autoimmune and cardiovascular disease: a multivariate genome-wide analysis. Cardiovascular Diabetology. https://doi.org/10.1186/s12933-025-03041-8