What causes some people to develop chronic diseases such as rheumatoid arthritis, cancer and metabolic syndrome while others stay healthy? A major clue could be found in their gut microbiome, the trillions of microbes living inside the digestive system that regulate various bodily functions.
To distinguish a healthy microbiome from one that is diseased, Mayo Clinic researchers have developed a Gut Microbiome Health Index. In a new study published on September 15 in the Nature Communications, the researchers reveal how their index can take a gut microbiome profile from a person's stool sample to reveal the likelihood of having a disease independent of the clinical diagnosis.
"This discovery advances our understanding of the composition of a healthy gut microbiome that has been long sought after. Our index predicts how closely a gut microbiome sample resembles healthy or unhealthy conditions," says lead author Jaeyun Sung in a report published on the Mayo Clinic website.
For the new study, Dr. Sung and his team analyzed 4,347 human stool shotgun metagenomes, which allow researchers to extensively sequence all genes in all known organisms present in a stool sample. The samples were pooled across 34 published studies spanning healthy conditions and 12 non-healthy disease conditions. Nearly 1,700 of the gut microbiome samples were from non-healthy people, that is, those with a clinically diagnosed disease or abnormal body weight based on BMI. Nearly 2,600 samples were from people reported as healthy, that is, with no overt disease or adverse symptoms.
"We pooled together the non-healthy samples into one group and the healthy samples into another. 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," Dr. Sung explains.
The analysis led to a microbiome signature of the healthy human gut composed of 50 microbial species. The discovery of a healthy gut microbiome signature helped develop a mathematical formula that predicts how closely a gut microbiome sample resembles healthy or non-healthy conditions.
"Based on this formula, we can tell anyone 'Your microbiome resembles that of a healthy population', and tell another 'Your microbiome resembles very close to what a microbiome would be in a disease population'," he concludes.