The secret to healthy aging could be bacteria. Specifically, the trillions of bacteria that live in our gut.
Cardiovascular disease is the leading cause of death worldwide and increases in incidence as we age. Typically, age-associated cardiovascular disease results from multiple morbidities, including high blood pressure, high cholesterol, diabetes and obesity. And while our genetics and a healthy, active lifestyle play an important role in modulating these risk factors, new research suggests another key factor may be at play: the gut microbiome.
We are increasingly learning that our gut bacteria play a role in everything from digestion to depression, as well as our risk of developing numerous diseases. Indeed, there is an accumulating body of evidence that our gut microbiomes may hold the key to healthy aging. But while previous research has identified microbial patterns associated with healthy aging, the interplay among our gut microbiome, age and metabolism in cardiovascular disease risk is less well researched.
In a study published in the journal Nature Medicine, scientists from the Shanghai Jiao Tong University School of Medicine set about investigating whether age-associated microbial signatures could affect the development of cardiovascular disease in those with known risk factors for cardiovascular disease.
"We designed this prospective study to identify metabolically healthy and unhealthy [individuals,] investigate age-associated and metabolism-associated gut microbial signatures and dissect the interplay among the gut microbiome, age and metabolism with long-term cardiovascular disease risk," the researchers wrote.
To begin with, the researchers classified a cohort of 19,268 individuals, aged between 40 and 93, into what they describe as "multi-morbidity clusters." These groupings described participants according to their presentation of multiple disease risk factors.
For example, individuals in multi-morbidity cluster 1 (or MC1) were considered to be metabolically healthy, while those in MC4 exhibited metabolic disturbances associated with obesity. Those in MC5, meanwhile, exhibited metabolic disturbances associated with high blood sugar.
Over a 10- to 11-year period, those in MC4 saw a 75 percent higher risk of developing cardiovascular disease compared with MC1, while those in MC5 saw a 117 percent increased risk. Of these participants, fecal samples were taken from 4,491 individuals and analyzed to establish any clear patterns in the gut microbes of each multi-morbidity cluster group.
In a separate analysis, the team also found a clear change in microbiome composition with age, which was validated using an external cohort of 4,425 individuals. From this, the researchers created a "gut microbial age" metric—a measurement to describe how "old" an individual's gut microbiome is, regardless of his or her chronological age.
Among individuals over 60, those in groups MC4 and MC5 with a higher microbial age showed an increased risk of cardiovascular disease, compared with those with a lower microbial age, independent of chronological age, sex and other lifestyle factors. In other words, those with "younger" gut microbiomes were less likely to develop cardiovascular disease in spite of having multiple cardiovascular disease risk factors.
"[We] found that a younger microbial age...effectively counteracted the cardiovascular disease risk in metabolically unhealthy older individuals, independent of chronological age, sex, educational attainment, lifestyle and dietary factors and medication use," the researchers write.
"This pattern...implies a modulating role of microbial age in cardiovascular health for metabolically unhealthy older people," they said.
Further research is needed to confirm these associations, but previous studies in animals have suggested that transplanting the gut microbes of younger individuals into older ones could ameliorate age-associated diseases and extend life spans in older individuals.
And how do you transplant someone's microbes? By transferring their poop!
However, the researchers add that this intervention—known as a fecal microbial transplant—may pose potential risks, such as increased inflammation. "Hence, turning back the aging clock with fecal microbial transplant might not be an optimal strategy for maintaining healthy aging," they write.
"Future microbiome-based approaches tailored to individual health status are crucial for promoting health across the human lifespan," they said.
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