A study published in the journal Translational Psychiatry demonstrated how a diet high in saturated fats could cause depression-like behavior in mice by disrupting the normal functions of the brain.
The link between obesity and depression
The researchers identified a connection between obesity and depression. However, whether obesity is a factor for developing depression, as well as the mechanisms behind this causality, remain unclear. To explore this, researchers from the University of Glasgow, in collaboration with the University of California and King's College London, investigated the molecular pathways that link the two disorders using laboratory mice. The team then identified the hypothalamus as the most probable connection between obesity and depression. (Related: Obesity causes depression, concludes "strongest evidence yet.")
The hypothalamus is a small part of the brain that helps stimulate essential functions like controlling appetite, releasing hormones, and regulating emotion responses.
In this study, the researchers used two groups of mice to test their hypothesis. One group was given a regular diet while the other was fed a high-fat diet (HFD), in which 60 percent of the caloric intake in the diet came from fat. The researchers then put the mice through a myriad of behavioral tests to measure the physical expressions of depression. These tests include forced swim tests, open field tests for locomotor activity, sugar preference tests, tail suspension tests, and a maze test to measure anxiety in the mice.
Three weeks into the experiment, the mice exhibited depression-like symptoms like immobility during tail suspension and forced swim tests. Mice that ate an HFD also consumed less sucrose solution, which the researchers relate to anhedonia, a characteristic feeling describing the inability to experience pleasure by enjoyable activities.
While mice under an HFD did gain more weight than those who took a normal diet, the researchers claimed that the weight gain did not correlate with any of their physical expression findings. This suggested that something in the mice's brain was responsible for causing depression-like symptoms.
After conducting a protein and mRNA analysis, the researchers identified that HFDs could disrupt the key signaling pathways in the hypothalamus due to an increase in fatty acids. The researchers observed that the saturated fatty acids in HFDs enter the brain through the bloodstream, which then accumulates and affects the brain signals related to depression.
The researchers noted that their findings were the first to show that consuming an HFD can induce an influx of dietary fatty acids in the body, which leads to the impairment of bodily signaling pathways. According to them, their findings can help develop a new way to treat obese patients suffering from depression in the near future.
“This is the first time anyone has observed the direct effects a high-fat diet can have on the signaling areas of the brain related to depression. This research may begin to explain how and why obesity is linked with depression and how we can potentially better treat patients with these conditions," said lead author George Baillie in a statement.
“We all know that a reduction in fatty food intake can lead to many health benefits, but our research suggests that it also promotes a happier disposition. Further to that, understanding the types of fats, such as palmitic acid, which are likely to enter the brain and affect key regions and signaling will give people more information about how their diet can potentially affect their mental health.”
Read up more on how diets can affect depression at MindBodyScience.news.
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