The main physiological functions of the intestinal bacterial flora, the nutrient stream

An obligatory condition for food assimilation is the disassembly of its complex structures to simple compounds that occurs during digestion. The liberated monomers (amino acids, monosaccharides, fatty acids, etc.) are devoid of species specificity and are predominantly the same for all organisms. In some cases, oligomers (di-, tri-, and occasionally tetramers) can be formed, which can also be assimilated. In higher organisms, the transport of oligomers is demonstrated by the example of dipeptides. Thus, the assimilation of food is realized in three stages: extracellular (cavity) digestion - membrane digestion - absorption, and in a number of organisms - in four, involving intracellular digestion.

The flow of hormones and other physiologically active compounds

Recently, it has been shown that the endocrine cells of the gastrointestinal tract also synthesize thyroid-stimulating hormone and ACTT, that is, hormones typical of the hypothalamus and pituitary gland, and the pituitary cells are gastrin. Consequently, the hypothalamic-pituitary and gastrointestinal systems appeared to be related to certain hormonal effects. There are also data that cells of the gastrointestinal tract secrete some steroid hormones.

For a long time it was believed that the endocrine cells of the gastrointestinal tract secrete hormones and other physiologically active factors involved primarily in the self-regulation of digestion and absorption of nutrients. However, it is now known that physiologically active substances control not only the functions of the digestive apparatus, but also the most important endocrine and metabolic functions of the whole organism. It turned out that the so-called classical hormones of the gastrointestinal tract (secretin, gastrin, cholecystokinin) and a number of unidentified hypothetical hormones, besides local, or local, actions, perform various functions for the regulation of other organs. An example of hormones of general action are also somatostatin and artereter.

Violation of the endogenous flow of physiologically active factors from the gastrointestinal tract into the internal environment of the organism causes severe consequences. We have demonstrated that the removal of even part of the endocrine system of the digestive apparatus under certain conditions leads either to death or to severe illness of the animal.

Exogenous flow of physiologically active substances consists mainly of specific substances formed during the splitting of food. So, when hydrolyzing pepsin proteins of milk and wheat, substances called exorphins, that is, natural morphine-like (by action) compounds are formed. Under certain conditions, the resulting peptides can penetrate into the blood in some quantities and participate in the modulation of the overall hormonal background of the organism. It can also be assumed that certain peptides, including those formed during the normal digestion of certain food components, perform regulatory functions. Such peptides belong to the casomorphine, a product of hydrolysis of milk protein (casein).

The role of nutrition in the formation of physiological and psychological standards of man is further enhanced by the discovery of the functions of certain amino acids as neurotransmitters and their predecessors.

Thus, nutrition is not a simple act of eating that can be reduced to enriching the body with nutrients. Simultaneously, a complex stream of hormonal factors coexists, which is extremely important, and perhaps vital for the regulation of food assimilation, metabolism and, as it is revealed, certain functions of the nervous system.

Flows of bacterial metabolites

With the participation of the bacterial flora of the intestine, three streams are formed, directed from the gastrointestinal tract into the internal environment of the body. One of them is a flow of nutrients modified by microflora (for example, amines that arise during decarboxylation of amino acids), the second is the flow of living products of the bacteria themselves and the third is the flow of modified ballast substances by the bacterial flora. With the participation of microflora, secondary nutrients are formed, including monosaccharides, volatile fatty acids, vitamins, essential amino acids, etc., substances that, at today's level of knowledge, appear indifferent, and toxic compounds. It was the presence of toxic compounds that gave rise to the idea of the expediency of suppressing the intestinal microflora, expressed by II. Mechnikovym. However, possibly toxic substances, if their number does not cross certain boundaries, are physiological and are constant and unavoidable companions of exotrophy.

Some toxic substances, in particular toxic amines formed in the digestive apparatus under the influence of bacterial flora, have long attracted attention. Among amines with high physiological activity, cadaverine, histamine, octopamine, tyramine, pyrrolidine, piperidine, dimethylamine, etc. Are described. A certain idea of the content of these amines in the body gives the level of their excretion in the urine. Some of them significantly affect the state of the body. With various forms of diseases, in particular dysbacteriosis, the level of amines can dramatically increase and be one of the causes of disturbances in a number of body functions. The production of toxic amines can be suppressed by antibiotics.

Along with the endogenous, there is an exogenous histamine, which is formed mainly in the intestines as a result of bacterial activity. Therefore, the use of antibiotics can lead to a number of shifts in the hormonal status of the body. Perhaps many pathological changes in the body are provoked not by hyperfunction of the stomach cells secreting histamine, but due to its excess production in the intestine by the bacterial flora. So, with the hyperproduction of histamine by the bacterial flora of the intestine, stomach ulcers appear, a tendency to disrupt the hypothalamic-pituitary functions, to allergies, and so on.

The physiological importance of secondary nutrients is indicated by a sharp increase in the demand for vitamins in humans and animals in which the bacterial flora is suppressed by antibiotics.

The tranformation of ballast substances in the intestine occurs mainly under the influence of anaerobic microflora.

In addition to these streams, there is a flow of substances coming from food contaminated as a result of various industrial and agricultural technologies, or from a polluted environment. This stream also includes xenobiotics.

Now it is firmly established that dietary fibers play an important role in normalizing the activity of the gastrointestinal tract (especially the small and large intestine), increase the mass of the muscle layer, affect its motor activity, the rate of absorption of nutrients in the small intestine, pressure in the cavity of the digestive organs , electrolyte metabolism in the body, mass and electrolyte composition of feces, etc. It is important that dietary fibers have the ability to bind water and bile acids, as well as adsorb toxic compounds I. The ability to bind water has a significant effect on the rate of transit of the contents along the gastrointestinal tract. In the literature there are reports that bran food fibers bind 5 times more water than their own weight, and fibers of such vegetables as carrots and turnips are 30 times larger. Finally, dietary fibers affect the habitat of bacteria in the intestine and are for them one of the sources of nutrition. In particular, microorganisms use cellulose, hemicellulose and pectin, partially metabolizing them into acetic, propionic and butyric acids.

Dietary fibers are necessary for the normal activity of not only the digestive apparatus, but also the whole organism. A number of disorders, including atherosclerosis, hypertension, ischemic heart disease, gastrointestinal pathology, diabetes, etc., in many cases, not only the result of excessive consumption of proteins and carbohydrates, but also the consequence of insufficient use of ballast substances. There is evidence that the lack of dietary fiber in the diet can provoke colon cancer. Without dietary fiber, the metabolism of not only bile acids, but also cholesterol and steroid hormones is disturbed. (It is striking that Avicenna and his predecessors already knew about the harm of purified foods.)

Many forms of pathology of the gastrointestinal tract and metabolism are susceptible to prevention and treatment due to dietary fiber introduced into the diet. So, these fibers can increase glucose tolerance and modify its absorption, which can be used to prevent and treat diabetes, hyperglycemia and obesity. An increase in the amount of dietary fiber in the diet reduces the level of cholesterol in the blood, which is associated with the participation of fibers in the bile acid circulation. The antitoxic effect of vegetable dietary fiber is also shown. At the same time, when using a number of dietary fibers, the absorption of certain trace elements, especially zinc, decreases.

Prolonged use of dietary fiber leads to a decrease in the severity of irritable bowel syndrome and diverticulosis of the colon. Dietary fibers contribute to the successful treatment of constipation, hemorrhoids, Crohn's disease and other diseases of the gastrointestinal tract, and can also serve as a preventative against relapses of peptic ulcer of the stomach and duodenum. In particular, with chronic pancreatitis, a diet enriched with fiber, that is, with dietary fiber, in most cases produces a positive therapeutic effect.

Therefore, it is necessary that not only proteins, fats, carbohydrates, trace elements, vitamins, etc., be included in food rations, but also dietary fiber, which is a valuable component of food.

So, on the basis of the classical theory, attempts were made to create improved and enriched food by removing dietary fibers, which led to the development of many diseases, the so-called diseases of civilization. Currently, the opposite direction is intensively being developed - searches are being made for adequate food rations corresponding to the needs of the organism that arose in the course of evolution. In humans, such an evolutionarily adequate food includes a significant proportion of substances that have been unsuccessfully called ballast for a long time.

[1], [2], [3], [4], [5], [6], [7], [8], [9], [10]