At the Kahn Center, we learned in 2011 of a new pathway of disease and harm due to elevated levels of a gut metabolite called TMAO. When the lab test for it became available, we started measuring it at least once in all patients. When elevated, we advised eliminating red meat, egg yolks, L-carnitine and choline supplements, and some fish like cod.
Now, a new study further relates elevated TMAO levels to a serious vascular condition, abdominal aortic aneurysms or AAA.
An AAA is a bulge in the part of the aorta that runs through the abdomen. Normally, the aorta's wall is strong enough to manage the constant pressure of blood pumped out by the heart. However, various factors like aging, smoking and other medical conditions can weaken it.
AAAs affect millions of patients annually and can rupture with an increased risk as they enlarge. An aneurysm repair by either endovascular (performed inside the blood vessels) or open surgery is typically recommended for larger aneurysms. AAAs usually have no symptoms until they rupture or are close to rupturing.
This was a prospective cohort study using 2 independent clinical cohorts undergoing aorta imaging surveillance: a European cohort and a US cohort. Included in this study were patients undergoing serial imaging surveillance of the aorta and long-term outcome monitoring. Patients were recruited from single-center studies in Uppsala, Sweden, and Cleveland, Ohio. Study data were analyzed from October 2023 to May 2025. The study focus was the association of TMAO levels with AAA risk, fast-growing AAA (≥4.0 mm per year), and recommended surgical intervention (≥4.0 mm per year or ≥5.5 cm diameter).
The European cohort included 237 individuals and the US cohort included 658 individuals. In the European cohort, elevated circulating TMAO was significantly associated with AAA risk independent of traditional risk factors and kidney function. Moreover, elevated TMAO predicted both greater risk for fast-growing AAA and recommended surgical intervention.
Similar patterns were observed in the US cohort and the combined European and US cohort, with heightened circulating TMAO corresponding with significantly increased adjusted risk for fast-growing AAA and recommended surgical intervention.
Addition of TMAO to base models containing traditional cardiovascular risk factors resulted in significant improvement in both risk estimation for fast-growing AAA and predicting recommended surgical intervention.
CONCLUSION
Results of this study suggest that elevated circulating TMAO levels were associated with increased risk of AAA and identified patients at heightened risk for fast-growing AAA and recommended surgical intervention.
TMAO may help identify individuals who may benefit from more frequent surveillance imaging and early surgical intervention to prevent aortic dissection or rupture.
TMAO can be lowered by removing the dietary components that drive its production in the gut: red meat, egg yolks, some fish like cod, and supplements like L-carnitine and choline.
We will continue to measure TMAO levels at the Kahn Center and lower them when elevated.
