From the Journals

Heart disease risk rises with gut metabolite linked to red meat



Changes in gut microbiota linked to red meat intake over time were significantly associated with increased risk of coronary heart disease, regardless of baseline microbiota measures, based on data from 760 participants in the Nurses’ Health Study.

“A gut microbiota–related metabolite, trimethylamine N-oxide (TMAO), has been related to risks of major adverse cardiovascular events including myocardial infarction and coronary heart disease (CHD) in epidemiological studies,” but previous studies have not examined the impact of long-term changes in TMAO on CHD risk, wrote Yoriko Heianza, RD, PhD, of Tulane University, New Orleans, and colleagues.

Red meat has been shown to increase TMAO levels, whereas discontinuation of red meat intake reduced plasma TMAO levels (Eur Heart J 2019;40:583-94), the investigators wrote.

In their study, published in the Journal of the American College of Cardiology, the researchers evaluated blood samples from 760 women who were participants in the Nurses’ Health Study. The samples were collected at two time points: 1989-1990 and 2000-2002. The researchers identified 360 incident cases of CHD over the study period and compared them with matched controls.

Over roughly 10 years, increases in TMAO over time were significantly associated with increased CHD risk, with a relative risk of 1.58 for the top tertile and a relative risk of 1.33 per each standard deviation.

Women with elevated levels of TMAO both at baseline and at the 10-year point had the highest CHD risk (relative risk 1.79), compared with women with low TMAO levels at baseline and 10 years later.

The researchers also found an impact of diet on the TMAO-CHD relationship. Individuals with unhealthy eating patterns based on the Alternate Healthy Eating Index showed greater increases in TMAO and greater CHD risk. By contrast, greater adherence to healthy eating habits attenuated the impact of TMAO and CHD.

The study findings were limited by several factors, including the inability to assess the timing of the changes in the metabolites that contributed to CHD, the reliance on self-reports for dietary patterns and other variables, and the inclusion only of women health professionals in the study population, the researchers noted. However, the results were strengthened by the availability of long-term blood samples and a patient population free of disease at baseline.

In addition, “adherence to healthy dietary patterns may modulate the adverse relationship between TMAO changes and CHD, suggesting that TMAO as a potential intermediate endpoint of interventions focusing on dietary modifications for CHD prevention,” the researchers wrote.

“The findings of the study provide further evidence for the role of TMAO as a predictive biomarker for atherosclerotic heart disease and strengthen the case for TMAO as a potential intervention target in CV [cardiovascular] disease prevention,” wrote Paul A. Heidenreich, MD, and Petra Mamic, MD, of Stanford (Calif.) University, in an accompanying editorial.

In addition, “It is increasingly clear that GMB [gut microbiota] metabolites have biological activity, and that dietary changes alter the GMB and its metabolic output, with subsequent modulation of downstream host effects,” they wrote.

“While acknowledging the limitations of self-reported dietary pattern assessment, this is an important finding because it suggests that healthy dietary patterns may in some ways neutralize TMAO’s harmful effects on the CV system, potentially through other identified and unidentified GMB-mediated pathways,” they added.

The study was sponsored in part by the National Institutes of Health, the Boston Obesity Nutrition Research Center, and the United States–Israel Binational Science Foundation. Neither the researchers nor the editorialists had any financial conflicts to disclose.

SOURCES: Heianza Y et al. J Am Coll Cardiol. 2020 Feb 17. doi: 0.1016/j.jacc.2019.11.060; Heidenreich PA, Mamic P. J Am Coll Cardiol. 2020 Feb 17. doi: 10.1016/j.jacc.2019.12.023.

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