Glucose metabolism, immune system and microflora

Immunity affects sugar metabolism through intestinal bacteria

Kirill Stasevich, "Science and Life"

We know that the intestinal microflora is given the widest powers in our body, which are especially clearly visible in how bacteria affect metabolism: it is believed that depending on the composition of the microflora, obesity and diabetes may or may not happen in us. Microbes of the digestive tract are able to increase the likelihood of atherosclerosis through metabolism, moreover, more and more data is gradually accumulating in favor of the fact that bacteria can actively interfere with the work of the nervous system – so, in May we wrote that normal microflora is needed in order for new neurons to appear in the brain.

The life of intestinal bacteria largely depends on how they interact with the immune system. Here a lot depends on the mutual configuration of both "contracting parties": if something goes wrong in the communication of microbes and the immune system, we are threatened with chronic inflammation, which, as is known, can provoke a whole bunch of diseases, including the notorious diabetes. On the other hand, it is difficult for the immune system to function normally without peaceful intestinal bacteria: symbiont microbes, on the one hand, help it fight dangerous infections, and on the other, regulate the activity of the immune system, protecting us from autoimmune and allergic reactions.

It is the close connection between immunity and intestinal microflora that can shed light on some strange physiological effects that are not always explicable yet. For example, there is evidence that the immune system affects metabolism. In particular, glucose metabolism depends on the level of one of the interferons – interferon-gamma: experiments on mice have shown that if interferon–gamma is low, then, firstly, less glucose is produced in the liver, and, secondly, insulin sensitivity increases in tissues. Hypersensitivity to insulin means that cells are able to actively absorb sugar from their environment by an insulin signal. High insulin sensitivity is good, low sensitivity is bad: then the cells do not "absorb" glucose, the level of which in the blood begins to rise. The inability of cells to perceive the insulin signal is one of the characteristic features of type 2 diabetes.

And so, it turns out that one of the interferons – whose function, we recall, is to activate the immune system in the case of a viral infection – somehow affects the insulin sensitivity of cells. Given the close interaction of immunity and microflora, could it be that some intestinal bacteria serve as intermediaries here? Indeed, as researchers from the University of Oregon write in Nature Communications, there is such a bacterial mediator, and it is called Akkermansia muciniphila (see the press release of OSU Immune system uses gut bacteria to control glucose metabolism). If the level of interferon-gamma was reduced in the experimental mice, A.muciniphila became more in their intestines, and in general the situation with sugar metabolism improved: the animals increased glucose resistance, that is, they could cope with elevated blood sugar levels by sending it to the cell in accordance with insulin instructions. If the level of interferon-gamma increased, the number of A.muciniphila bacteria decreased, which negatively affected glucose metabolism.

A similar relationship between A.muciniphila exists in humans: the more active the gene responsible for the synthesis of interferon, the less this bacterium lives in the intestine. It is known about A. muciniphila that it becomes scarce with obesity, and that it can be used to normalize metabolism – at least in mice. However, its connection with obesity and diabetes in humans remained largely confusing – perhaps because it was not known about the third player in the form of interferon.

Obviously, such an indirect influence from the immune system on metabolism is a rather conservative thing among mammals, and it is unlikely that everything is limited to A.muciniphila alone – after all, a whole lot of different microbes live in our digestive tract; and the more we know about what games they play with immunity and with our metabolism the sooner we learn how to prevent and treat various metabolic disorders.

Portal "Eternal youth" http://vechnayamolodost.ru  17.11.2016