It sounds bonkers that a tick bite might make meat eaters allergic to their steaks and ribs, but it’s true. Now new research has added a potential twist: The source of this tick-related sensitivity to red meat may also be linked to coronary artery disease.
A bite from the lone star tick, Amblyomma americanum, can trigger antibodies to a sugar called alpha-gal, found in many mammals but not humans. For some of the tick-bitten, that produces an allergic reaction to alpha-gal in red meats like beef and pork. A new study also finds that heart patients with the antibodies had more plaque buildup in their artery walls. Of 118 people with coronary artery disease, 31 who tested positive for the antibodies had about 25 percent more plaque in their artery walls than those who were negative, researchers report in the July Arteriosclerosis, Thrombosis and Vascular Biology.
Study participants were aged 30 to 80; the connection between extra gummed-up arteries and the presence of antibodies was strongest in those 65 and younger. For the antibody-positive participants in that group, the plaques penetrating the walls of the arteries were of the sort more likely to rupture and cause a heart attack (SN Online: 5/5/09).
Elevated levels of allergen-targeting antibodies have been previously linked with coronary artery disease, but this study is the first to identify a specific allergen, says cardiologist Coleen McNamara of University of Virginia School of Medicine in Charlottesville. The study also tested for possible links to antibodies to other common allergens such as peanut, ragweed and dust mites but didn’t find a connection. She and her colleagues want to see if the link to alpha-gal antibodies holds up among a larger group.
Eating red meat is associated with an increased risk of heart disease, and the new work adds to the story of why that may be, says biochemist Guo-Ping Shi of Brigham and Women’s Hospital in Boston, who was not involved with the study.
Still, the study only shows an association. To search for a possible mechanism, McNamara’s team plans to study alpha-gal and artery inflammation in mice; inflammatory cells released via the immune system contribute to plaques.