Gut Bugs Promote Blood Vessel Growth

11 March 2012
Posted by Ben Valsler.

The bacteria that live in your intestines change the way that blood vessels form inside your gut.  New research, published in the journal Nature, identifies how this happens and offers potential new targets for treating intestinal diseases and obesity.

There are more bacterial cells in your body than human cells, but they are not mere passengers or parasites.  Healthy intestinal flora helps to educate the immune system as well as playing an important role in vitamin production and absorption of nutrients.  Disturbed or unbalanced gut flora is known to be associated with disease, such as inflammatory intestinal disease, obesity and allergies.

Low magnification micrograph of small intestinal mucosa. H&E stain. The inside of the intestine is lined with villi -protrusions that increase the surface area and therefore the amount of nutrients that can be absorbed.  When mice are bred in germ free environments, and so have no bacteria in their gut, these are long and narrow, but introducing bacteria causes the villi to become significantly wider and increases the density of blood vessels nearby.  This suggests that the presence of bacteria can modify the absorptive capacity of the gut.

Now, Fredrik Bäckhed at the University of Gothenburg and colleagues in Sweden and Germany have identified three factors responsible for this effect - Tissue Factor (TF), Protease-Activated Receptor 1 (PAR1) and Angiopoietin-1 (Ang-1), all of which are known to be involved in blood vessel creation and proliferation.

The presence of bacteria leads to a sugar molecule being attached to the surface of the Tissue Factor protein, which then causes it to migrate to the surface of the cell, where it signals to other factors to start creating blood vessels.  This increases the density of local blood vessels and alters the amount of nutrient that can be absorbed across the intestine wall. Altering these pathways, therefore, could lead to the ability to artificially modulate how the gut absorbs nutrients; a potential treatment for obesity and intestinal disorders.

Professor Bäckhed acknowledged that this is only a first step towards treatment, saying:  "It will take time before the results can be applied in a clinical context and converted into new therapies. But our discovery is exciting, and is a result of fundamental basic research which teaches us a great deal about how we live in cooperation with the normal gut microobiota."

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