New research, which appears in The Journal of Physiology, examines the role that gut bacteria might play in preserving the health of our arteries.
An increasing number of studies suggest that the bacteria in our guts hold the key to healthy aging.
For instance, a recent conference that Medical News Today reported on featured research in the worm Caenorhabditis elegans. The results suggested that colonizing the gut with specific strains of bacteria, for example, can delay aging and prevent a host of age-related chronic diseases.
Now, research in mice strengthens the idea that gut bacteria mediate the aging process. Specifically, scientists have examined the link between the composition of the gut microbiota in mice and vascular aging.
Vienna Brunt, a postdoctoral researcher in the Department of Integrative Physiology at the University of Colorado, Boulder, is the study’s lead author. Doug Seals, a professor and the director of the university’s Integrative Physiology of Aging Laboratory, is the senior author.
Brunt and colleagues administered a “cocktail of broad‐spectrum, poorly absorbed antibiotics” to a group of young mice and a group of old mice. They added the antibiotics to the drinking water of the rodents for a period of 3–4 weeks to suppress their gut microbiota.
Next, the researchers examined the health of the rodents’ vascular systems by measuring their arterial stiffness and the health of the endothelium — that is, the layer of cells that line the inside of the arteries.
Brunt and her team also examined the rodents’ blood samples for markers of inflammation and oxidative stress, such as harmful free radicals.
Oxidative stress occurs when the body produces too many free radicals and does not have enough antioxidants to degrade them. Studies indicate that this phenomenon contributes to hypertension, cardiovascular disease, and aging in general.
The researchers also measured levels of nitric oxide, a compound that expands the blood vessels. Finally, they examined the “age-related changes” in each rodent’s gut microbiota.
At the end of the study period, the scientists found that the old mice benefited greatly from the antibiotic treatment, while the intervention had no effect on young mice.
Specifically, “When you suppressed the microbiome of the old mice, their vascular health was restored to that of young mice,” reports Prof. Seals.
Next, the scientists set out to identify certain age-related changes in the microbiota of rodents. Their aim was to understand how suppressing the microbiota may preserve vascular health.
To do so, they genetically sequenced the fecal samples of another group of old mice and compared them with those of young mice.
“In general, in the old mice, we saw an increased prevalence of microbes that are pro-inflammatory and have been previously associated with diseases,” says lead author Brunt.
These included taxa of microbes that previous studies had linked with gut dysbiosis — an imbalance between the “friendly” bacteria in our guts and other pathogens.
For example, the study found that the old mice had a higher concentration of proteobacteria — a major class that includes well-known pathogens such as Escherichia coli, Salmonella, and Campylobacter bacteria.
The scientists also analyzed blood plasma levels of a compound called trimethylamine N‐oxide, or TMAO. This is a “gut-derived metabolite,” which means that it is a compound produced when microorganisms in the gut break down nutrients from food.
Although the role of TMAO in chronic disease remains uncertain, some previous studies found high levels of TMAO in people with “cardiovascular disease, kidney disease, type 2 diabetes mellitus, and cancer.”
In the current study, the old mice had three times as much TMAO in their blood as the young mice, and the researchers found that antibiotic treatment suppressed TMAO levels.
Brunt and her team conclude:
“The results of the present study provide the first evidence for the gut microbiome being an important mediator of age-related arterial dysfunction and oxidative stress.”
The findings, continue the authors, also indicate “that therapeutic strategies targeting gut microbiome health may hold promise for preserving arterial function and reducing cardiovascular risk with aging in humans.”
The researchers suggest that eating foods rich in probiotics, such as kefir, yogurt, or kimchi, may help preserve cardiovascular health well into old age.
Prof. Seals comments on the results, saying, “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.”
“We now suspect that, with age, the gut microbiota begins producing toxic molecules, including TMAO, which get into the bloodstream, cause inflammation and oxidative stress, and damage tissue,” he continues.
In other words, say the authors, “The fountain of youth may actually lie in the gut.”
“This is the first study to show that changes in the gut microbiome with aging have an adverse impact on vascular health. […] It opens up a whole new avenue of potential interventions to prevent cardiovascular disease.”
Vienna Brunt, Ph.D.