Human Microbiome Project: Stage 2
The Human Microbiome project has established a link between microbiota and intestinal inflammation, diabetes and premature birth
And predicted the development of diabetes in one patient even before the appearance of classic symptoms
Polina Loseva, "The Attic"
The Human Microbiome Project (HMP, Human Microbiome Project) has published the results of the second stage of its work. Three groups of American researchers have established links between microbes living on human mucous membranes, concentrations of substances in the blood and common pathologies: intestinal inflammation, prediabetes and premature birth. One way or another, these diseases were associated with a violation of the microbial composition: in patients, the main inhabitants of the intestine were displaced by strangers and provoked inflammation. Now scientists expect that the data they have obtained will help doctors make long-term predictions about the condition of patients.
The Human Microbiome is a project that brought together dozens of scientists from different parts of the United States in order to conduct a general census of microscopic human symbionts, as detailed as possible. And since the set of bacteria in humans varies quite a lot, in order to find some common patterns, we have to collect thousands of samples. At the first stage of the project, the researchers compiled a portrait of a healthy microflora, and also created a database of genomes of intestinal, skin and vaginal bacteria.
In the new issue of Nature, the project reports on the second stage completed. This time, the subject of the study was individual diseases in which scientists tried to find a bacterial component.
The first article is devoted to intestinal inflammation – Crohn's disease and ulcerative colitis. After studying the tests in 132 patients over the course of a year, the authors found that the most common intestinal inhabitants in patients become smaller. Accordingly, there are fewer short-chain fatty acids produced by these bacteria, which feed the cells of the intestinal wall and transmit signals to the human brain, including a saturation signal. In place of the usual bacteria, new opportunistic species are coming. In response to this, inflammation develops in the intestinal wall, so strangers do not stay in the intestine for a long time. Anyway, the microflora of sick people is constantly changing, approaching a healthy composition during periods of remission.
The second branch of the project worked with premature births. The researchers suggested that they, too, may be caused by a change in the composition of the microbiome. And indeed, in cases where the pregnancy ended prematurely, there were very few bacteria in the mothers' vagina Lactobacillus, while in healthy mothers who gave birth on time, their population was very significant. As a rule, the first trimester of pregnancy is accompanied by mild inflammation – a reaction to changes in the uterine wall and the appearance of a foreign body. Then, in the second trimester, the immune response, on the contrary, subsides so as not to interfere with the development of the embryo, and increases in the third: childbirth becomes the culmination of rejection of the fetus. Apparently, premature birth is caused by inflammation: starting in the first trimester, it no longer stops, because the bacteria that should suppress it are not enough. Interestingly, preterm labor is more common in women of African descent, so the next stage of the work should be the search for correlations between the microbiota and the genetic characteristics of patients.
The third area of research was prediabetes – an extremely urgent (at least for the USA) problem. The first signs of diabetes (which are called prediabetes) appear in almost every third American, and in 70% of cases they turn into a full-fledged disease. But despite the fact that in the early stages, patients differ from healthy people almost only by their insulin resistance, the differences were much stronger at the microbial and immunological level. It turned out that people with prediabetes have an increased amount of pro-inflammatory proteins, that is, the body exists in a constant "inflammation" mode. However, when they get a respiratory viral infection, the response to it develops weaker and later than in healthy people, and the microbial composition of the nasal cavity changes much less.
In several cases, the work of scientists has acquired predictive power. In one patient, they found abnormalities in blood tests indicating liver problems, and five months later, doctors diagnosed him with steatosis (accumulation of fat) in the liver. In another patient with prediabetes, researchers noticed an increase in pro-inflammatory markers and microbial waste products, indicating a violation of glucose metabolism. She was officially diagnosed with diabetes only 10 months later, so we can assume that scientists managed to catch the earliest signs of the disease from the microbiota long before the symptoms appeared.
However, the project participants have yet to work on the development of early diagnosis of diseases by microflora. In the first two stages, they were rather busy collecting data and looking for directions for future work.
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