Dangerous gut-heart liaison

When it comes to matters of the heart, don’t always trust your gut.

Researchers at the Kantonsspital St.Gallen have identified a new risk factor for inflammatory heart disease. As the scientific magazine Science reports in its November 15, 2019 issue, harmless gut bacteria can instruct the immune system to attack the heart, exacerbating damage and inflammation. These new findings make it possible for the first time to use targeted therapeutic approaches in this potentially fatal disease.

Myocarditis, or inflammatory disease of the heart muscle, is one of the causes of cardiac damage. In most patients myocarditis presents with mild to moderate severity symptoms such as shortness of breath, tachycardia and possibly months of prolonged physical weakness. Nevertheless, persistent (chronic) myocarditis can lead to inflammatory cardiomyopathy and heart failure, a common reason for heart transplantation. Although viral infections or myocardial infarction, heart attacks, may trigger myocarditis, in the majority of cases the cause cannot be identified and factors aggravating disease severity remain unclear. "The disease-causing processes leading to myocarditis have not been sufficiently studied.” Prof. Burkhard Ludewig, head of the study at the Medical Research Centre of the Kantonsspital St.Gallen, explains the starting point for the study. The St. Gallen research group has shown that the composition of intestinal bacteria plays an important role in the development of myocarditis and inflammatory cardiomyopathy. Harmless intestinal bacteria, such as Bacteroides thetoiotaomicron, can reprogram immune cells and thus promote an attack on heart cells. So-called T-helper cells recognize components of intestinal bacteria that are very similar to certain structural elements of heart cells and are thus activated. The researchers from St. Gallen were able to show the causal relationship of such cross-reactivity in preclinical studies with mice.

Prof. Hans Rickli, chief physician of the Division of Cardiology in St. Gallen, sees the clinical importance of the previously unknown connection between the bacterial milieu and myocarditis: "For the first time, the new findings obtained in this way open up ways of treating this disease by specifically influencing the composition of the ‘intestinal microbiome’. The work would not have been possible without the international cooperation between basic researchers and clinically researching physicians from cardiology and laboratory medicine." In collaboration with scientists from ETH Zurich and the University of Calgary in Canada, a relationship between the genetic predisposition, the intestinal microbiome and myocarditis was established and confirmed in patients.

"We believe that the serious consequences of myocarditis could be prevented or at least alleviated by testing therapeutic approaches for the targeted alteration of the intestinal milieu in myocarditis patients," says Prof. Ludewig, describing the future plans for the possible implementation of the study results in everyday clinical practice.

Inflammatory cardiomyopathy