Hot new areas of biomedicine sometimes generate cool skepticism. Little more than a decade ago, investigators proposed that the gut microbiome might be contributing to obesity. Since then, the microbiome has been linked to numerous major diseases, including atherosclerosis, although some have been skeptical about this association.
How could the gut microbiome influence the course of any disease? The central argument is simple and compelling. Humans actually have 2 genomes: human genes and the collective genes (the “microbiome”) of the trillions of microbes (the “microbiota”) that coexist with each human.
The advent of rapid nucleic acid sequencing has revealed an astonishing fact: the microbiome contains more than 100 times as many genes as there are human genes. More remarkably, these microbial genes generate proteins, including hormones, neurotransmitters, and molecules of inflammation, that can enter the circulation and affect human physiology. Thus, the microbiome is not only a second genome: it is also like an additional endocrine organ.
Considerable evidence indicates that the human gut microbiome may affect the development and progression of atherosclerosis, both by influencing risk factors for atherosclerosis and by direct effects on the initiation and progression of atherosclerotic plaques.