Mucus-eating bacteria in the human gut may help control cholesterol levels, new research in mice and laboratory dishes suggests.
Ackermanthia muciniphila is a bacterium that lives in the human body, and primarily in mouse studies, this microbe is thought to be associated with protection from bacteria. metabolic disease, neurological disorders and certain infections. as its name suggests, A. muciniphila It mainly consumes mucin. Mucin is a large, sugar-rich protein that forms most of the mucus that lines the intestinal lining.
Since mucin is typically difficult for microbes to digest, scientists were interested in investigating what might make digestion possible. A. muciniphila It settles in the human intestine and proliferates by feeding on proteins.
In their new study, published June 19 in the journal natural microbiologythe team first cultured A. muciniphila They studied mucin taken from pigs and observed the growing bacteria under a microscope. They discovered that bacteria store mucin in intracellular compartments, which scientists named mucinosomes. Interestingly, these compartments are Ackermanthia Since no seeds have been observed, bacteroides Theta Otaominanother mucin-loving microbe.
Related: People who live to be 100 have unique gut microbiota signatures
Scientists then created mutants A. muciniphila Strains that use “transposon mutagenesis”, a process that introduces genetic mutations into the DNA of microorganisms and propagates these mutants in mucin. Some mutant strains failed to produce amino acids, the building blocks of proteins, and these strains were unable to grow on mucin. This indicates that amino acid production is important for microorganisms to benefit from mucin.
The team then fed the mutants A. muciniphila For various genetically modified experimental mice. The growth pattern of the mutants in the cecum, part of the large intestine, reveals that bacteria lacking genes that produce amino acids are very difficult to grow, especially in the presence of other bacterial species. . Genes for four specific amino acids (alanine, asparagine, glutamine, arginine) A. muciniphila It successfully colonizes the gastrointestinal tract.
In further experiments with mice, the researchers discovered two groups of genes that are key to trafficking mucins to specific compartments of bacterial cells. These, called mucin utilization locus (MUL) genes, are important for bacterial growth and colonization in the gut.
The so-called MUL1 group of genes encode proteins that transport mucins into bacterial cells. The MUL2 gene group produces proteins that form pili (fine hair-like appendages that protrude from the cell surface) and may also help transport mucins into the bacterium.
In ‘germ-free’ mice bred to be free of gut bacteria, normal strains of gut bacteria A. muciniphila Mutants with dysfunctional MUL1 or MUL2 genes grew when all strains were mixed in the gut of mice. In addition, when grown alone, usually A. muciniphila It suppressed the expression of a mouse gene involved in cholesterol production, but the same cholesterol-producing gene was enhanced in mice with the following symptoms: A. muciniphila A mutant in which MUL1 is dysfunctional.
From this, the authors concluded that mucin-phagocytic bacteria may directly influence cholesterol production in the gut and thus serve as an important tool to control high cholesterol levels. .
‘This is an important and elegant study’ to establish a way to fine-tune genes A. muciniphila It shows how important mucins are for interactions between mucus-devouring microbes and their hosts and other bacteria. Willem Meindelt de VosEmeritus professors at Wageningen University and Helsinki University, who were not involved in the study, told Live Science in an email.
recently Proof-of-concept studiesDe Vos and colleagues tried to give A. muciniphila As an aid to human volunteers insulin resistance They found that the volunteers’ sensitivity to insulin improved and their cholesterol levels decreased over time. However, that trial was very small and provided more data. A. muciniphila Human supplementation is still needed.
