Red meat allergy linked to increased risk of CVD

Sensitivity to an allergen in red meat may portend plaque buildup in coronary arteries, particularly in persons aged 65 years and older, according to a study recently published in Arteriosclerosis, Thrombosis, and Vascular Biology.

“This novel finding from a small group of subjects from Virginia raises the intriguing possibility that allergy to red meat may be an underrecognized factor in heart disease,” said lead researcher Coleen McNamara, MD, professor of medicine, Cardiovascular Research Center, University of Virginia Health System, Charlottesville, VA. “These preliminary findings underscore the need for further clinical studies in larger populations from diverse geographic regions and additional laboratory work.”

Galactose-α-1,3-galactose (alpha-Gal) is a type of complex sugar that is the main allergen in red meat. A bite from the Lone Star tick can sensitize people to this allergen. Consequently, red meat allergies may be more common in areas where the Lone Star tick is more prevalent, including the southeastern United States and areas such as Long Island, NY.

Although only 1% of the population in some areas of the United States may have a red meat allergy, estimates of the number of persons who develop serum antibodies to this allergen without exhibiting full-blown symptoms may be higher, possibly as much as 20% of the population in affected areas.

For this study, Dr. McNamara and colleagues sought to identify the immunoglobulin (IgE) specific to the alpha-Gal allergen. They analyzed serum samples from 118 adults aged 30 to 80 years undergoing medically warranted cardiac catheterization. Patients did not differ in baseline risk factors or markers of coronary artery disease (CAD), including hypertension, lipid levels, or diabetes. However, more men and African Americans were sensitized to alpha-Gal Antibodies to alpha-Gal were present in 26% of subjects. Upon conducting intravascular ultrasound, researchers found that plaque quantities were 30% higher in subjects sensitized to alpha-Gal compared with non-sensitized subjects (P=0.02).

Researchers further stratified patients by age and discovered that the strength of the association with atheroma burden was stronger (P < 0.001) in those 65 years or older, a “striking difference,” they noted. Plaques in older, sensitized subjects also tended to be more structurally unstable and more fibrofatty, necrotic, calcified but with less fibrous content, increasing the likelihood of myocardial infarction and stroke.

To test the specificity of the association between IgE to alpha-Gal, Dr. McNamara and fellow researchers assayed IgE to inhalants—including dust mite, timothy grass, oak, and ragweed—and to peanuts but did not have a significant association with atheroma burden, atheroma volume, or maximal stenosis.

They also identified a strong association between total IgE and alpha-Gal specific IgE, the strongest relationship occurred between atheroma burden and alpha-Gal specific IgE, which remained significant even when adjusted for sex, diabetes, hypertension, statin use, and total IgE (regression coefficient: 12.2; SE: 5.2; P=0.02).

“To our knowledge, this is the first report that has described an association between the IgE response to α-Gal, or any specific allergen, and the burden of CAD. A link between a food allergen and CAD may not seem a priori obvious, but there are several elements of the immune response to α-Gal that argue for biological plausibility,” wrote Dr. McNamara and colleagues.

Although the link between red meat allergens and CAD is preliminary, they plan further studies to confirm these findings.

“As the causal agent of a delayed allergic reaction to mammalian meat, which is IgE mediated, the glycolipid form of α-Gal may be particularly relevant to understanding its role in atherosclerosis. Mechanistic studies in animal models are suggested, but ultimately, efforts to translate this finding into clinical relevance will benefit from analysis of larger cohorts, including disparate geographic areas and prospective studies of adult subjects, which include information on diet, allergic history, and detailed investigation into sIgE (selective IgE) antibodies,” they added.

Ahmed Hasan, MD, PhD, medical officer and program director, National Heart, Lung, and Blood Institute’s (NHLBI’s) Atherothrombosis & Coronary Artery Disease Branch also commented on these results.

“While more studies are needed, the current work provides a potential new approach or target for preventing or treating heart disease in a subgroup of people who are sensitized to red meat.”

This study was supported by the NHLBI and the National Institute of Allergy and Infectious Diseases, both part of the National Institutes of Health.