16 December 2015

Microflora and diabetes

The researchers described the changes in the intestinal microflora characteristic of diabetes

Type 2 diabetes, also known as insulin-dependent diabetes, is a serious metabolic disorder. In this disease, the body's cells lose their ability to respond to insulin, the hormone that controls glucose uptake. Due to the inability to interact with insulin, cells stop absorbing glucose and begin to starve even with sufficient nutrition, high blood glucose levels and sufficient insulin (in type 1 diabetes, insulin synthesis is disrupted and cells face glucose deficiency due to the lack of a hormone).

According to the World Health Organization, there are about 285 million patients with type 2 diabetes in the world. The prevalence of the disease and the severity of its complications (for example, the risk of gangrene of the lower extremities increases 20 times in patients) forces doctors and scientists to look for both the causes of disorders and new ways to combat them. Recently, researchers have begun to have serious arguments in favor of the fact that diabetes may be associated, among other things, with the composition of the microbial community inside our intestines, with the intestinal microbiota. It was the changes in the microbiota of the large intestine that were studied by specialists from four Russian research centers, whose work is presented in the journal Endocrinology Connections (Egshatyan et al., Gut microbiota and diet in patients with different glucose tolerance).

Scientists analyzed the composition of the intestinal microbiota in 92 people, including 20 patients with diabetes mellitus and 48 healthy people without any chronic diseases; another 24 showed signs of metabolic disorders, which doctors attributed to prediabetes - a condition that can lead to the development of type 2 diabetes over time. Glucose levels, as the most important indicator of metabolism, were also monitored in the study participants using a blood test.

The gut microbiota is the totality of all living microorganisms living in it (including even some unicellular fungi and archaea). You can also often hear that the inhabitants of the intestine are called microflora – this is a historical term that developed at a time when bacteria were considered plants. 

The "main characters" of this study were bacteria. To determine which bacteria the researchers are dealing with, they analyzed DNA isolated from stool samples. Having isolated DNA, scientists sequenced (counted and decoded the sequence of nucleotide pairs in DNA) the gene encoding ribosomal RNA, rRNA – an important component of ribosomes, microscopic structures for protein synthesis. All classes of bacteria have a gene encoding this structure, and there is a database that allows you to identify bacteria by the sequence of nucleotides in this gene. This section of bacterial DNA is a kind of passport of the bacterium.

Comparing the composition of the microbiome with the diagnosis (diabetes/prediabetes/the absence of violations) and the diet of the volunteers participating in the study, the scientists made several conclusions.

First of all, the researchers were able to link the level of glucose intolerance to the presence of three specific representatives of the microbiota: bacteria of the genera Blautia, Serratia and Akkermansia. Healthy people have all of them, but with prediabetes and diabetes, their proportion increases significantly.

But the increase in the levels of bifidobacteria (there are most of them in the intestines of children who feed on mother's milk and they are considered to be one of the most important components of the microbiota) was associated with a high consumption of dietary fiber, that is, fiber. 

Bifidobacteria under an electron microscope. 
Their length is about 5 micrometers. Picture: Julie6301 / Wikimedia

This echoes the results of an earlier study of the gut microbiota of cities and villages in Russia, conducted with the participation of the same group of scientists. Then the researchers found out that residents of the villages of the Tuva region have significantly more bifidobacteria than residents of other regions: presumably, this is due to the fact that natural products predominate in the diet of the rural population, and the proportion of "industrial" food with a reduced fiber content, on the contrary, is small.

The data obtained bring scientists and physicians closer to understanding the complex mutual causal relationships between changes in the proportion of certain types of bacteria, metabolic disorders and diet. As the authors of the study indicate in the discussion of the results, one of the possible mechanisms of the influence of microbes on diabetes may be provoking an immune reaction – this theory was previously expressed by Finnish experts.

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