A Mechanism by which Gut Bacteria Mediate the Effects of Dietary Fiber on Inflammation

Dietary fiber is known to reduce chronic inflammation; the modest but reliable degree to which it does so is well studied. In recent years researchers have been turning their attention to the diverse microbes of the gut in order to understand how this and other dietary effects on the immune system and tissues are mediated. Some attention has been given to the production of butyrate by gut bacteria involved in digesting fiber, for example. Researchers here find an analogous mechanism in the bacterial production of propionate from fiber, and make some inroads into understanding how exactly it functions to reduce inflammation.

To a large extent our well-being depends on what bacterial guests in our digestive tract consume. That's because gut flora help the human body to utilize food and produce essential micronutrients, including vitamins. Beneficial gut microbes can produce metabolites from dietary fiber, including a fatty acid called propionate. This substance protects against the harmful consequences of high blood pressure. Researchers have now shown why this is the case. The researchers fed propionate to mice with elevated blood pressure. Afterwards, the animals had less pronounced damage to the heart or abnormal enlargement of the organ, making them less susceptible to cardiac arrhythmia. Vascular damage, such as atherosclerosis, also decreased in mice.

"Our study made it clear that the substance takes a detour via the immune system and thus affects the heart and blood vessels." T helper cells, which enhance inflammatory processes and contribute to high blood pressure, were calmed. This has a direct effect on the functional ability of the heart. The research team triggered heart arrhythmia in 70 percent of the untreated mice through targeted electrical stimuli. However, only one-fifth of the animals treated with the fatty acid were susceptible to an irregular heartbeat. Further investigations with ultrasound, tissue sections, and single-cell analyses showed that propionate also reduced blood pressure-related damage to the animals' cardiovascular system, significantly increasing their survival rate. But when researchers deactivated a certain T cell subtype in the mice's bodies, known as regulatory T cells, the positive effects of propionate disappeared. The immune cells are therefore indispensable for the substance's beneficial effect.

Propionate still has to prove itself in everyday clinical practice. The research team now hopes to validate their findings by examining the substance's effects on human subjects. It is already known that propionate is safe for human consumption and can also be produced economically: The substance has been used for centuries as a preservative, for example. It is already approved as a food additive. "With these favorable conditions, hopefully propionate will soon make the leap from the lab to patients who need it."

Link: https://www.mdc-berlin.de/news/press/how-dietary-fiber-and-gut-bacteria-protect-cardiovascular-system