Written by By Jhinuk Sen, CNN
Scientists have uncovered a link between a Western diet and neurodegenerative diseases like Alzheimer’s.
The findings come from a two-year, worldwide study conducted by Johns Hopkins University. To be published in the November issue of the journal NeuroImage, they describe a process called “cytotoxicity” — the destruction of brain cells through toxins released by gut bacteria — which appears to be a contributor to cognitive decline and neurodegenerative diseases.
The researchers aimed to identify the various contributors to cytotoxicity in the mouse brain, and identified those that are linked to food.
“We’re now able to pinpoint what the vulnerable pathways in the mouse brain are, and we may be able to identify these pathways in humans as well,” says neuroscientist and study co-author Don Weber, MD, PhD, chair of the Department of Neuroscience at Johns Hopkins.
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The scientists studied three types of worms, and then fed each worm different types of food including the Western diet (a diet rich in red meat, fruits and vegetables, and not relying on animal fats) and the traditional diet of their home town.
Experiments showed the cells of the local diet consumed in the mice showed changes that were similar to those seen in the mice that were fed Western diets. This movement of brain cells into the region of the brain’s memory center was detected before the cells had fully died.
The scientists also discovered that the bacteria in the stomach had a stronger effect on the “cell-mediated pathology” of local diets.
In mouse models of two forms of Alzheimer’s disease, a Western diet — which has been shown to raise blood cholesterol and increases the risk of diabetes — drove the buildup of plaques and tangles of neurons. In addition, the levels of the cholesterol-producing “good” HDL cholesterol and the nitric oxide in the blood decreased as a result of the Western diet.
Ruth Eschbach, MD, PhD, a professor of neurology and lead investigator of the study in the Johns Hopkins laboratory, says, “Even after living in a mouse body in a lab for two years, we could observe that dietary changes can effect brain microenvironment. “
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“We see major changes in the brain. The lining of the brain’s memory center is now partly deprived of nitric oxide, which is a chemical that helps the cell function,” she says.
Moreover, the early changes in the mouse bodies, with localized alterations of the regions in the brain with a greater number of neurons, corresponded to the disease progression in humans.
“If we can understand how dietary changes lead to brain microenvironmental change, that would explain why there are differences between different populations of people, or why there is a common characteristic that can predict which type of Western diet a person would be more susceptible to,” says Eschbach.
Associate professor Uri Lotan, PhD, a co-author of the study in the neuroscience laboratory of Lotan Tsaffarim, MD, says, “We’re demonstrating that this cytokine circuit affects both inflammation and cognitive function and that the diet — specifically, a Western diet — has a direct role in this process. This is significant since the effects of dietary restriction alone are still difficult to evaluate.
Another professor, Yuqing Jia, MD, PhD, an epidemiologist in the department of epidemiology, says, “Even though the study was conducted in mice, it shows that there may be an increase in risk for Alzheimer’s and dementia in people with a Western diet. It’s not just dietary exercise and exercise in general; this is an important factor, and it needs to be studied.”
Western diet link to memory loss?
The investigation further suggests that changes in the gut microbiota are a cause of Alzheimer’s in the central nervous system. In addition, toxins that release into the brain through the gut are transmitted through the blood supply — hence their association with the inflammation that underlies the cognitive changes.
For now, “a cheap and easy way to reduce the risk of developing Alzheimer’s is to cut down on the number of burgers and fries,” says Dr. Weber. “There are so many unknowns and variables that affect the disease — from genes to diet — but since we have finally begun to tease apart the toxic effects of gut bacteria, this is a very promising direction.”