Disaccharidase deficiency enteropathies - Causes

Causes and pathogenesis of disaccharide deficiency enteropathies

The following enzymes, disaccharidases, are produced in the intestinal mucosa:

• isomaltase breaks down isomaltose;
• thermostable maltase II and III - breaks down maltose;
• invertase - breaks down sucrose;
• trehalase - breaks down trehalose;
• lactase - breaks down lactose.

The enzymes listed break down disaccharides into monosaccharides (in particular, invertase breaks down sucrose into fructose and glucose; maltase breaks down maltose into two glucose molecules; lactase breaks down lactose into glucose and galactose).

The most common deficiency is lactase, which causes milk intolerance (it contains lactose), invertase (sugar intolerance), and trehalase (fungal intolerance).

Due to the deficiency of disaccharidases, disaccharides are not broken down and, under the influence of bacteria, disintegrate in the intestine; carbon dioxide, hydrogen, and organic acids are formed. These substances irritate the mucous membrane of the small intestine, causing the development of fermentative dyspepsia.

Disaccharidase deficiency can be primary, congenital (inherited in an autosomal recessive manner) and secondary (due to various gastrointestinal diseases and the use of certain medications - neomycin, progesterone, etc.). Diseases such as chronic enteritis, nonspecific ulcerative colitis, Crohn's disease can cause the development of secondary disaccharidase deficiency. Lactase deficiency is especially common, and the activity of this enzyme decreases with age even in healthy people.

By breaking down disaccharides into monosaccharides (lactase into glucose and galactose, sucrose into glucose and fructose, maltose into two glucose molecules, etc.), disaccharidases create conditions for their absorption. Disruption of the production of these enzymes leads to the development of disaccharide intolerance, which was first described 30 years ago. Thus, lactase deficiency was noted by A. Holzel et al. in 1959, and sucrase deficiency by H. A. Weijers et al. in 1960. Publications in recent years indicate a fairly high prevalence of disaccharidase deficiency, and deficiency of several enzymes that break down disaccharides is often observed simultaneously. The most common deficiencies are lactase (milk intolerance), invertase (sucrose intolerance), trehalase (fungi intolerance), and cellobiase (intolerance to foods containing large amounts of fiber). As a result of the absence or insufficient production of disaccharidases, unsplit disaccharides are not absorbed and serve as a substrate for the active reproduction of bacteria in the small and large intestines. Under the influence of bacteria, disaccharides decompose to form tricarbon compounds, CO2, hydrogen, and organic acids, which irritate the intestinal mucosa, causing a symptom complex of fermentative dyspepsia.

A particularly common cause of disaccharidase deficiency is lactase deficiency in the small intestinal mucosa, which occurs in 15-20% of adult residents of Northern and Central Europe and the white population of the United States and in 75-100% of the indigenous peoples of Africa, America, East and Southeast Asia. The results of studies conducted on American blacks, residents of Asia, India, some regions of Africa and other population groups showed that a fairly large part of the indigenous population of a number of countries and continents feels practically healthy. In Finland, lactase deficiency occurs in 17% of the adult population. Lactase deficiency is observed more often among Russians (16.3%) than among Finns, Karelians, Vepsians living in the Karelian ASSR (11.0%), and residents of the Mordvin nationality (11.5%). According to the authors, the same frequency of hypolactasia in Finns, Karelians and Mordvins is explained by the fact that in ancient times these peoples constituted one nation and dairy cattle breeding arose among them at the same time. The authors emphasize that these data confirm the correctness of the cultural-historical hypothesis, according to which the degree of repression of the lactase gene can serve as a kind of genetic marker.

The results of some researchers' studies have led to the conclusion that under certain environmental conditions, the nature of nutrition over a long historical period can lead to significant genetic changes in humans. In certain situations, during the process of evolution, the nature of nutrition can affect the ratio of individuals in populations with different gene pools, causing an increase in the number of people with the most favorable set of genes.

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