Over the last 10 years, the U.S. National Institutes of Health has invested $170 million to better understand the universe of bacteria that live within us—the so-called microbiome. In thefirst phase of the project, researchers focused on cataloguing the myriad types of microbes found throughout the body, including in the mouth, nose, gut, and reproductive tract.
The latest phase of the research focused on better understanding how changes in those microbial populations affect three conditions: diabetes, preterm birth and inflammatory bowel diseases. A growing body of research is finding links between how diet, weight, and environmental exposures, among other things, can affect the mix of bacteria that make up our microbiomes.
In thestudy on diabetes, a team of researchers followed 106 people for nearly four years, profiling their microbiomes from nasal swabs, stool samples, and blood every three months. The volunteers came in for extra visits when they caught colds or the flu, and, at their will, during stressful events such as job changes, weight gain, travel, or exposure to environmental elements that could affect their health. That way, the researchers could track how these experiences impacted their immune systems and the composition of microbes in their bodies.
They found that there is no true “normal” when it comes to the microbiome. Everybody’s healthy baseline is different but there were some commonalities in the microbiomes of people with certain disease states, including insulin resistance.
Diabetes often starts as insulin resistance, when people start to have trouble breaking down sugar and other carbohydrate foods. Insulin resistance can lead to pre-diabetes, and 70% of people with pre-diabetes go on to develop type 2 diabetes during their lifetime. People with insulin resistance tend to have different microbes, which then cause immune cells to act in different ways compared to people who are more sensitive to insulin. So when those who are insulin resistant or pre-diabetic get sick, their immune responses are often weaker those who are not.
An insulin resistance signature can be predicted from the microbiome. Currently, detecting insulin resistance requires a six-hour test that costs thousands of dollars, but a microbial assay, from stool samples, could cost a fraction of that. Having an assay for insulin resistance could be very powerful in catching people who might develop diabetes much earlier. That’s important because managing pre-diabetes before it becomes diabetes is critical, since it’s hard to reverse once diabetes occurs.
Using the microbiome may also predict which women might be at higher risk of delivering prematurely. They found that women who delivered early, at less than 37 weeks, were less likely to have Lactobacillus crispatus, which previous studies have linked to a healthy reproductive tract, and more likely to contain a diverse community of vaginal microbes, often including four specific taxa. Other recent studies have suggested that understanding the vaginal microbiome might also help to predict IVF success.
In a third paper, the Harvard T.H. Chan School of Public Health team followed 132 people, some with inflammatory bowel disease and others without, for a year. They collected stool, biopsy and blood samples in order to track whether and how their microbiomes changed during disease flare-ups, and during recovery periods. They were indeed able to identify changes in the types of bacteria that become active during flare-ups periods compared to during recovery periods, as well as changes in how those microbes were impacting the immune system.
All of the studies continue to build the list of key players in the microbiome, which include not just the specific microbes involved but also the other factors—such as immune cells and other metabolic chemicals—that interact with the microbes to affect human health.
One of the challenges in finding useful applications for the microbiome is how variable they are, both from person to person, and in any given individual over time. These early studies have enabled scientists to see many different ways across individual patients that the gut microbiome becomes [perturbed] and often restores itself over time. The goal is to start to put together all [the] different ways in which that can happen, and understand what is common about them.
My dad died when we couldn’t remember his blood type. As he died, he kept insisting for us to “be positive,” but it’s hard without him