New Study Reveals How Microbiome From Young Mice 'Reverse Aging' in Mouse Brains

Russian Nobel prize-winning scientist and discoverer of innate immunity, Elie Metchnikoff, suddenly became anxious of aging as he turns 50, leading him to study intestinal bacteria in health and disease that makes people live longer.

In some parts of eastern Europe, people eat lot of fermented foods with lactic acid bacteria, and theories say these gut microbes are essential to healthy aging.

It was just recently that scientists found that trillions of bacteria, known as the gut microbiome, helps regulate health and disease and its composition changes with age.

A 2012 study suggests that gut microbiota have a correlation to diet and health in the elderly, and diversity in the microbiome was linked to health outcomes in later life, including frailty.

This made scientists become increasingly curious about the effect of the microbiome on brain aging.

Immune impairments caused by brain aging can be reversed

Scientists in later study of University College Cork revisited Metchnikoff's 2017 study of age-related alterations in microbiota-gut-brain of a mouse, which suggests that aging induced changes in the microbiota and immune system, and was associated with cognitive decline and anxiety.

Then again, gaps on correlation among aging and many factors are still unfulfilled, which led to a subsequent study of mouse brains that went 'a step further' to show how a microbiota-targeted diet could lessen the effects of brain aging.

Researchers of the latest study used a prebiotic inulin-enriched microbiota, a prebiotic that feeds beneficial bacteria in the gut, to lessen the effects of aging in the brains of middle-aged mice. However, it was unclear whether the microbiota itself caused the slowing of brain aging.

By transplanting the microbiome from young mice into old mice, the team found that many effects of aging on learning and memory and immune impairments are reversible.

To test this in mice, they used a maze to see if the fecal microbiota transplant from young to old mice led the old mice to find the hidden platform faster.

Microbiome is essential for a healthy brain in old age

Basically, inflammation across all systems in the body, including the brain, increases as you age. The brain itself has its own immune system, and that immune process, specifically controlled by the microglia, ironically can cause harm.

While the microglia are involved in brain development to protect against diseases such as meningitis and Alzheimer's, they are also vulnerable to 'physiological disturbances' such as aging.

The same class of cells visualized by Metchnikoff down a microscope was found to have been activated and regulated by gut microbiome.

In the next puzzle, scientists found that the negative effects of aging on immunity are also reversible, as inflammation lessened when scientists transplanted the microbiota from young mice to the old mice.

"Finally, we showed that chemicals in a region of the brain involved in learning and memory (the hippocampus) were more like that of young mice following the microbiota transplant," researchers wrote.

"Our results show conclusively that the microbiome is important for a healthy brain in old age."