Data from 4,347 publicly available human stool shotgun metagenomes – of which about 1,700 were from ‘non-healthy’ people and about 2,600 from ‘healthy’ – revealed a microbiome signature of the healthy human gut composed of 50 microbial species.
The scientists then developed a mathematical formula that predicts how closely a gut microbiome sample resembles healthy or non-healthy conditions. The Gut Microbiome Health Index (GMHI) is a ratio between the health-abundant species and the health-scarce species, with a higher number indicating a that the microbiome is ‘healthier’.
“This discovery advances our understanding of the composition of a healthy gut microbiome that has been long sought after,” said Jaeyun Sung, PhD, an assistant professor of surgery, Mayo Clinic College of Medicine and Science, and researcher within the Mayo Clinic Center for Individualized Medicine Microbiome Program, and the study’s corresponding author.
“A higher number is going to tell you: 'Oh, you look very healthy. Your microbiome resembles that of a healthy population,'” said Dr 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.'”
On an independent validation cohort of close to 700 human subjects, healthy samples were distinguished from non-healthy samples 74% of the time.
Commenting independently on the study, Mark Miller, PhD, MBA, Principal at Kaiviti Consulting, told NutraIngredients-USA: “This large and ambitious study aimed to determine if the species that construct the gut microbiome could be used as an indicator of disease in general. Thus, supporting the concept that alterations in the pattern of the microbiome could be used to predict health status, although it does not determine if these aberrations drive the problem or is a result of the condition.
“The study is important given its scope, providing further evidence that our health and the construction of our microbiome are intimately intertwined.”
Dr Miller added a note of caution: “However, as a tool for prediction, I am worried that this GMHI result may be subject to over-interpretation given that it was accuracy in only 73.7%. Does this mean that a quarter of the time these diseases do not have a microbiome involvement, or that the test is insufficiently sensitive in its predictive powers, or elements of both?
“I would take it at superficial level of affirmation that, YES, disturbances in the microbiome play a role in a wide range of diseases. However, a lot more digging into the nuances is required before it fulfills the criteria of a useful diagnostic tool.”
Writing in Nature Communications, Dr Sung and his co-workers pooled together the data from 34 published studies across healthy and 12 different ‘non-healthy’ conditions, which were characterized as either a disease or abnormal bodyweight.
“Then we did a comparison of the frequencies of the microbes that were observed in both groups,” explained Dr Sung. “We found some microbes are much more frequently observed in the healthy group, compared to the non-healthy group and vice versa.”
Heart health & gut health
The researchers also identified a moderate correlation between the GMHI and HDL cholesterol in the blood. In other words, a higher GMHI was correlated with higher (ie. better) HDL levels.
“That we were able to find this correlation with a marker of cardiovascular health is really exciting, as now we're connecting gut microbiome information with clinical data,” said Dr Sung. “One area of research in my group is to identify how the gut microbiome talks to various tissues in the body through chemical signals. Currently, we're far from being able to conclude on specific mechanisms, but we have some promising leads we'd like to further pursue."
The researchers are planning to continue to develop the Gut Microbiome Health Index so that it may one day contribute toward comprehensive medical and preventive health screening programs.
“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,” he said.
“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. Moreover, this work demonstrates the power of integrating existing samples across various sources and health conditions to identify truly robust insight that benefits human health.”
Source: Nature Communications
2020, Volume 11, Article number: 4635, doi: 10.1038/s41467-020-18476-8
“A predictive index for health status using species-level gut microbiome profiling”
Authors: V.K. Gupta, et al.