The intestinal microbiota and cardiovascular disease

The intestinal microbiota of human hosts is the community of microorganisms living in the small and, mainly, the large intestine of humans. This microbial ecosystem has co-evolved with humans across the millennia, has come to play an important interactive role in human physiology and has been aptly called our forgotten organ. Significant properties of the microbiota benefiting its host include energy harvest from food sources indigestible by humans, protection from pathogen colonization, and vitamin synthesis. Mounting evidence has linked changes in the composition or metabolic profiles of the microbiota with human disease, including disorders of the cardiovascular spectrum. Although cause and effect mechanisms are as yet essentially unproven in the relevant literature, the established associations point to the importance of the microbiota in the pathophysiology of cardiovascular disease (CVD). In this review, we first summarize key information on the gut microbial communities and the elaborate tools developed to analyse their structure and metabolic functions. Ecological terms are explained and analytical techniques are simplified, to enhance the understanding of published studies. Statistical methods used in microbial analysis are also described in simple terms. We then present published literature on the association of the compositional and functional changes of the microbiota with CVD, including heart failure, hypertension, and atherosclerosis. Each section of the review deals with the underlying pathophysiology of the relevant associations, connecting the observational and mechanistic aspects. Finally, we discuss the challenges that remain to be met before this field of research can generate knowledge which can impact everyday clinical practice.