Eating fatty foods in the days before surgery can trigger a heightened inflammatory response in the brain that interferes for weeks with memory-related cognitive function in older adults and, new animal research suggests, even in young adults.
The study, based on previous research from the same Ohio State University lab, also showed that taking a DHA omega-3 fatty acid supplement for a month before the unhealthy diet and surgical procedure prevented related memory effects. with both the high fat diet and surgery in young and aged adult rats.
Three days on a high-fat diet alone were detrimental to a specific type of fear-related memory in aged rats up to two weeks later—the same type of impairment seen in younger rats that ate fatty foods and underwent a surgical procedure. . The team has traced the brain inflammation behind these effects to a protein that activates the immune response.
“These data suggest that these multiple insults have a compounding effect,” said lead author Ruth Barrientos, a researcher at Ohio State’s Behavioral Medicine Research Institute and an associate professor of psychiatry, behavioral health and neuroscience at the College of Medicine.
“We have shown that an unhealthy diet, even in the short term, especially when consumed so close to surgery, which itself will cause an inflammatory response, can have detrimental outcomes,” Barrientos said. “The high-fat diet alone might increase inflammation in the brain a little bit, but then you do surgery that does the same thing, and when combined in a short period of time, you get a synergistic response that can put the things in motion.” towards a long-term memory problem.
The study was recently published in the journal Brain, behavior and immunity.
Barrientos’ lab studies how everyday life events could trigger inflammation in the aging brain as the nervous system responds to signals from the immune system reacting to a threat. Decades of research have suggested that with aging comes a long-term “priming” of the brain’s inflammatory profile and a loss of brain cell reserve to recover.
The researchers fed young and old adult rats a diet high in saturated fat for three days before a procedure resembling exploratory abdominal surgery, an event already known to cause about a week of cognitive problems in an elderly brain. Control rats ate normal food and were anesthetized, but did not undergo surgery. (Barrientos’ lab has determined that anesthesia alone does not cause memory problems in rats.)
In this study, as in previous research with aged rats treated with morphine after surgery, the team showed that an immune system receptor called TLR4 was to blame for brain inflammation and related memory problems generated by both surgery and high-fat diet, said first author Stephanie Muscat, assistant clinical professor of neuroscience at Ohio State.
“Blocking the TLR4 signaling pathway before diet and surgery completely prevented the neuroimmune response and memory impairments, confirming this specific mechanism,” Muscat said. “And as we had discovered before in another unhealthy diet model, we showed that DHA supplementation mitigated those inflammatory effects and prevented memory deficits after surgery.”
There were some surprising findings about memory in the new work. Different behavioral tasks are used to assess two types of memory: hippocampus-based contextual memory and amygdala-based fear memory. In tests of contextual memory, rats with normal memory freeze when they re-enter a room in which they had an unpleasant experience. Cued fear memory is evident when rats freeze in a new environment when they hear a sound related to that previous bad experience.
For the aged rats in this study, as expected, the combination of a high-fat diet and surgery caused problems with contextual and fear memory that persisted for at least two weeks, a longer-lasting effect than researchers had observed. researchers. before.
The high-fat diet alone also affected the aged rats’ fear memory. And in young adult rats, the combination of a high-fat diet and surgery caused only fear memory deficits, but no problems with memory governed by the hippocampus.
“What this tells us in elderly animals, along with the fact that we are seeing this same deterioration in young animals after high-fat diet and surgery, is that induced fear memory is uniquely vulnerable to the effects of the diet. And we don’t know why,” Barrientos said. “One of the things we hope to understand in the future is the vulnerability of the amygdala to these challenges of an unhealthy diet.”
With increasing evidence suggesting that fatty and highly processed foods can trigger inflammation-related memory problems in brains of all ages, consistent findings that DHA, one of the two omega-3 fatty acids present in fish and other shellfish and available in supplement form, it has a protective effect are compelling, Barrientos said.
“DHA was really effective in preventing these changes,” he said. “And that’s surprising: It really suggests that this could be a possible pretreatment, especially if people know they’re going to have surgery and their diet is unhealthy.”
This work was supported by grants from the National Institute on Aging and the National Institute of Neurological Disorders and Stroke.
Co-authors included Michael Butler, Menaz Bettes, James DeMarsh, Emmanuel Scaria and Nicholas Deems, all from Ohio State.