Gut bacteria is associated with cardiovascular and age-related diseases

In two recent studies, researchers demonstrated how gut microbiota—the vast array of intestinal microorganisms—are involved in aspects of cardiovascular and age-related diseases. These investigations also indicated that treating or restoring healthy microbial levels in the gut might just reverse such conditions.

Gut microbes’ effect on BMI and lipid levels

Gut microbiota have been found to influence factors involved in cardiovascular disease—namely, changes in body mass index (BMI) and lipid levels—independent of age, gender, and host genetics. In a study published in Circulation Research, researchers reported these findings from the largest study to date that links gut bacteria to blood lipids.

The findings also indicate the potential for therapies that would alter the gut microbiome to control BMI, triglycerides, and high-density lipoproteins (HDL) in order to prevent cardiovascular disease (CVD).

Although research into gut microbiota has risen dramatically in recent years, no large-scale human studies have found firm evidence of the gut microbiome’s role in the development of CVD.

In this analysis of 893 subjects from a population-based cohort of people in the Netherlands, researchers led by geneticists from the University Medical Center in Groningen, the Netherlands, used DNA sequencing to identify a total of 34 types of intestinal bacteria that contribute to changes in BMI and blood lipids.

“We observed that the gut microbiome makes a significant contribution, beyond that of clinical risk factors and genetics, to the individual variance seen in BMI and to the blood levels of triglycerides and HDL, but that it has little effect on LDL or total cholesterol levels,” the authors wrote.

Specifically, gut microbiota explain 4.5% of the variance in BMI, 6% in triglycerides, and 4% in HDL, the researchers found. But additional, yet-to-be discovered associations are also likely, the researchers noted.

“Our results highlight the potential of therapies that alter the gut microbiome to control body mass, triglycerides, and HDL in CVD prevention,” the authors concluded. “In moving from potential to action, it will be essential to identify the causal axis of microbiome-lipids-CVD and to gain more mechanistic insight into the gut bacteria functions.”

Gut microbes and age-related illness

Microbiota in the elderly, which is different than that in younger adults, correlates with measures of frailty, comorbidity, and inflammation. But how this association works is not well known. In a study published August 27, 2015 in Cell Reports, researchers discovered changes within intestinal microbes that occur before the end of life, and may predict the death, in experiments with fruit flies.

The findings of this study also hold the promise that restoring the health of gut microbiota may delay the onset of age-related conditions.

“Age-onset decline is very tightly linked to changes within the community of gut microbes,” said the study’s senior author David Walker, PhD, professor of Integrative Biology and Physiology at the University of California Los Angeles (UCLA), in Los Angeles, CA. “With age, the number of bacterial cells increase substantially and the composition of bacterial groups changes.”

The researchers studied fruit flies in part because, although their typical life span is just 8 weeks, some live to the age equivalent of humans’ 80s and 90s, while others age and die much younger. In addition, scientists have identified all of the fruit fly’s genes and know how to switch individual ones on and off.

In a previous study, the researchers found that flies displayed a loss of intestinal barrier function a few days before dying.

In this study, in which the scientists analyzed more than 10,000 female flies, they were able to detect bacterial changes in the intestine before intestinal barrier failure began. As part of the study, the researchers gave some fruit flies antibiotics, which significantly reduce bacterial levels in the intestine. The researchers found that the antibiotics prevented the age-related increase in bacteria levels and improved intestinal function during aging.

This experiment also showed that reducing harmful bacterial levels in old flies significantly prolonged their life span. “When we prevented the changes in the intestinal microbiota that were linked to the flies’ imminent death by feeding them antibiotics, we dramatically extended their lives and improved their health,” Dr. Walker said.

Flies that demonstrated intestinal barrier dysfunction and were given antibiotics lived an average of 20 days after the dysfunction began—a substantial part of the fly’s life span. But flies with intestinal barrier dysfunction that received no antibiotics died within a week.

“The health of the intestine—in particular the maintenance of the barrier protecting the rest of the body from the contents of the gut—is very important and might break down with aging,” said the study’s lead author Rebecca Clark, PhD, who was postdoctoral scholar at UCLA during the study.

The researchers cautioned that establishing cause-and-effect relationships between microbial dynamics and a given phenotype is a significant challenge for this research field. Yet, “our findings will facilitate a better understanding of the mechanisms by which life-extending manipulations impact pathophysiology and/or microbiota dynamics to improve organismal survival,” they concluded.