Eating more luteolin — a plant compound present in peppers, carrots, celery, olive oil, peppermint, chamomile, rosemary and others — directly results in having fewer inflammatory molecules in the brain.
With less inflammatory molecules, researchers believe it reduces age-related inflammation and its corresponding memory problems, according to a new study by the University of Illinois.
Inflammation in the brain appears to be a key contributor to age-related memory problems, said study leader and animal sciences professor Rodney Johnson.
The study’s focus was on microglial cells, specific immune cells that reside in the brain and spinal cord. Infections trigger microglia to produce signaling molecules, called cytokines, which prompt a surge of chemical changes in the brain.
Some of these signaling molecules, the inflammatory cytokines, cause the traits associated with feeling ill: sleepiness, memory deficits, loss of appetite and depressive behaviors.
“We found previously that during normal aging, microglial cells become dysregulated and begin producing excessive levels of inflammatory cytokines,” Johnson said.
“We think this contributes to cognitive aging and is a predisposing factor for the development of neurodegenerative diseases.”
For nearly a decade, Johnson has been researching the anti-inflammatory properties of nutrients and various bioactive plant compounds, including luteolin. Earlier studies have revealed that luteolin has anti-inflammatory effects in the body.
However, this is the first study to show that luteolin improves mental health by acting directly on the microglial cells to decrease their production of inflammatory cytokines in the brain.
In the study, microglial cells exposed to a bacterial toxin produced inflammatory cytokines that attacked neurons. However, if the microglia were exposed to luteolin before they encountered the toxin, the neurons lived.
“The neurons survived because the luteolin inhibited the production of neurotoxic inflammatory mediators,” Johnson said.
Interestingly, the researchers found that exposing only the neurons to luteolin before the experiment did not affect their survival.
“This demonstrated that luteolin isn’t protecting the neurons directly,” he said. “It’s doing it by affecting the microglial cells.”
Next, scientists studied the effects of luteolin on the brains and behavior of adult (3- to 6-month-old) and aged (2-year-old) mice. For four weeks, the mice were given a control diet or a luteolin-supplemented diet. The scientists observed their spatial memory and measured levels of inflammatory markers in the hippocampus, a region in the brain associated with memory and spatial awareness.
Normally, older mice will have more inflammatory molecules in the hippocampus and perform more poorly on memory tests than younger adult mice. However, the aged mice on the luteolin-supplemented diet did better on the learning and memory tasks than the younger mice, and the levels of inflammatory cytokines in the brains were nearly the same for all ages.
“When we provided the old mice luteolin in the diet it reduced inflammation in the brain and at the same time restored working memory to what was seen in young cohorts,” Johnson said.
“We believe dietary luteolin accesses the brain and inhibits or reduces activation of microglial cells and the inflammatory cytokines they produce. This anti-inflammatory effect is likely the mechanism which allows their working memory to be restored to what it was at an earlier age.”
“These data suggest that consuming a healthy diet has the potential to reduce age-associated inflammation in the brain, which can result in better cognitive health,” he said.
The study can be found in the current issue of the Journal of Nutrition.
Source: University of Illinois