Researchers at the Mayo Clinic have developed a test that can predict a person’s general health status by measuring the levels of 50 gut microbial species. Called the Gut Microbiome Health Index (GMHI), the formula does not diagnose specific diseases at this stage, but instead offers a general indication of one’s health.
Trillions of microbes live inside our gut, and a rapidly expanding body of research is discovering how profoundly influential these micro-organisms are on our general health. While these microbiome discoveries present some of the most promising medical science advances in recent times, there is one huge hurdle slowing down progress.
The more researchers learn about the relationship between human disease and gut bacteria, the more we realize how heterogenous microbiomes are. Every person’s gut bacteria population is different, so perhaps the biggest challenge scientists face is finding some kind of universal bacterial signature that can apply to all patients.
Instead of focusing on just one specific disease this new study, published in the journal Nature Communications, set out to understand what a generally healthy microbiome looks like. The researchers began by analyzing 4,347 stool samples. Around 2,600 of those samples came from healthy subjects with no diagnosed illness. The rest of the samples were from “non-healthy phenotypes,” such as individuals with colon cancer, diabetes, arthritis, heart disease or obesity.
"We pooled together the non-healthy samples into one group and the healthy samples into another," explains Jaeyun Sung, from the Mayo Clinic College of Medicine and Science, and corresponding author on the new study. "Then we did a comparison of the frequencies of the microbes that were observed in both groups. We found some microbes are much more frequently observed in the healthy group, compared to the non-healthy group and vice versa.”
The study ultimately homed in on 50 specific microbial species that could be used to ascertain a healthy microbiome signature – 43 species being scarce and seven species prevalent. This microbiome signature was then validated in an independent cohort of 679 stool samples, with the newly derived formula able to distinguish healthy subjects from non-healthy subjects with 73.7 percent accuracy.
Essentially, Sung says, the system presents a person with a number that offers a general indication of one’s microbiome health. It does not necessarily detect specific disease, but instead can offer doctors a biomarker for underlying disease that other diagnostic tools can home in on.
"So a higher number is going to tell you: 'Oh, you look very healthy. Your microbiome resembles that of a healthy population,'" says Sung. "But a low number reveals: 'Oh, we can't tell yet exactly which disease you may have, but we can tell that something looks off. Your microbiome resembles very close to what a microbiome would be in a disease population.' And that's what we call the Gut Microbiome Health Index. You can view it as a 'credit score for your gut.'"
At this stage the GMHI is still in preliminary stages of development. The researchers suggest there are several factors that need to be incorporated into the GMHI to enhance its accuracy. Including more disease phenotypes, focusing on microbial strains more specifically rather than species, and including a greater spread of ethnic and geographical populations, are all factors that should be incorporated into the system.
Sung suggests this kind of generalized microbiome analysis could be incorporated into routine health check-ups in the future. With further refinement the GMHI could offer a consistent way to predict one’s general heath, as well as a way to monitor the effect of certain medical treatments on the microbiome.
"Our proposed quantitative stool metric for indexing microbiome health is a conceptual and technical innovation, and has the potential to inform treatments for maintaining or restoring health through gut microbiome modulation," adds Sung. "Our index provides a destination point of what you want your microbiome to resemble, especially after a massive perturbation, such as food poisoning or antibiotics.”
The new study was published in the journal Nature Communications.
Source: Mayo Clinic