An intriguing new study, led by scientists from the University of Colorado Boulder, suggests an aging gut microbiome may be somewhat responsible for the degradation in cardiovascular heath that tends to appear as we grow older. The study is yet another addition to the growing body of evidence affirming the role gut bacteria plays in age-related disease.

Age-related cardiovascular disease is primarily driven by stress‐mediated arterial dysfunction. We know that as a human body grows older the risk of cardiovascular disease increases. A striking 70 percent of all people in the United States between the ages of 60 and 79 suffer from some form of cardiovascular disease.

Inspired by the accumulating research pointing to the gut microbiome as a primary modulator of oxidative stress and inflammation, a new study looked at whether there was a direct connection between gut bacteria alterations and arterial dysfunction. To examine this, scientists used antibiotics to eliminate the microbiome of both old and young mice. After a few weeks of broad-spectrum antibiotic treatment, the young mice displayed no changes to their arterial health, however, the older mice showed major improvements across several vascular health measures.

"When you suppressed the microbiome of the old mice, their vascular health was restored to that of young mice," says Doug Seals, senior author on the new study. "This suggests there is something about those microorganisms that is causing vascular dysfunction."

We know that as we age the variety of bacteria in our microbiome diminishes. This lack of microbial diversity can result in an imbalance, called dysbiosis, which some hypothesize as the cause of many age-related diseases. To try to home in on how certain bacteria could be driving cardiovascular disease, the researchers closely analyzed the differences between the old and young animals' microbiome.

"In general, in the old mice, we saw an increased prevalence of microbes that are pro-inflammatory and have been previously associated with diseases," explains Vienna Brunt, lead author on the research.

Significantly, one particular metabolite appeared in much higher levels in the old mice compared to the younger mice. Trimethylamine N-oxide, or TMAO, is a metabolite that has been strongly linked to atherosclerosis and stroke, and high levels of TMAO can appear in a person's blood when large volumes of certain bacteria are present in the gut.

"We have long known that oxidative stress and inflammation are involved in making arteries unhealthy over time, but we didn't know why arteries begin to get inflamed and stressed. Something is triggering this," says Seals. "We now suspect that, with age, the gut microbiota begins producing toxic molecules, including TMAO, which get into the blood stream, cause inflammation and oxidative stress and damage tissue."

It's too early to jump to any conclusions as to what all this research ultimately means. The researchers do strenuously note that decimating your microbiome with antibiotics is not the recommended solution. However, maintaining a diverse microbiome in older age may be a beneficial way to reduce cardiovascular disease risk. This, of course, is not as simple as eating a particular probiotic, but the researchers are currently investigating the impact of different diets on gut health and cardiovascular disease in human subjects.

An additional, more specific, investigation is also underway into a compound called dimethyl butanol. This compound has been found to block the production of TMAO, and it is traditionally found in some red wines and olive oils.

While an impressive volume of research is building supporting the idea that our microbiome may play a role in everything from auto-immune disease to Alzheimer's, it will still be some time before we find effective ways to translate these discoveries into clinical treatments.

The new study was published in The Journal of Physiology.