Abdominal aortic aneurysms occur when the main artery, the aorta, swells and potentially ruptures, causing life-threatening internal bleeding. Obstructive sleep apnea is typically a chronic condition where people repeatedly stop and start breathing while sleeping and can increase the risk of developing cardiovascular problems. Citing studies that indicate a higher prevalence of abdominal aortic aneurysms in patients with obstructive sleep apnea, MU researchers examined the link between the two using mouse models.

The research team found that intermittent hypoxia — when the body isn’t getting enough oxygen for a given period of time — caused by obstructive sleep apnea increased the susceptibility of mice to develop abdominal aortic aneurysms.

“Chronic intermittent hypoxia by itself is not enough to cause abdominal aortic aneurysms, but for a patient with obstructive sleep apnea who also has additional metabolic problems like obesity, our findings suggest it may help degrade aortic structures and promote aneurysm development,” said Luis Martinez-Lemus, study author and a professor of medical pharmacology and physiology.

Intermittent hypoxia happens during obstructive sleep apnea when throat muscles relax and block the flow of air into the lungs. According to the research, the loss of oxygen triggers certain enzymes called MMPs. The increased enzyme activity can degrade the extracellular matrix, which acts like a cell scaffolding network, weakening the aorta.

“Patients with abdominal aortic aneurysms usually don’t notice any symptoms, except for some back and belly pain, until the aneurysm bursts. Once that happens, it’s crucial to get the patient to surgery quickly so doctors can repair the aorta,” said Neekun Sharma, the lead author of the study. “Learning how these aneurysms develop can help us find ways to monitor or slow down their progression, especially for patients who have obstructive sleep apnea.”

Luis Martinez-Lemus is a professor of medical pharmacology and physiology, the James O. Davis Distinguished Professorship in Cardiovascular Research, and a NextGen Precision Health investigator. He earned his PhD at Texas A&M University and is a Doctor of Veterinary Medicine. Neekun Sharma is an assistant research professor in the Division of Endocrinology and Metabolism in the Department of Medicine.

“Chronic Intermittent Hypoxia Facilitates the Development of Angiotensin II-Induced Abdominal Aortic Aneurysm in Male Mice” was recently published in the Journal of Applied Physiology. In addition to Martinez-Lemus and Sharma, MU study authors include Abdelnaby Khalyfa, associate research professor in the Department of Pediatrics; Dunpeng Cai, assistant professor of surgery; Mariana Morales-Quinones, senior research specialist; Shi-You Chen, Division Chief of Surgical Research; Jaume Padilla, associate professor of Nutrition and Exercise Physiology; Camila Manrique-Acevedo, MU Health Care endocrinologist; and Bysani Chandrasekar, a professor of medicine in the Department of Cardiology. Rogerio Soares, Yusuke Higashi and David Gozal also contributed.