High-fat diets affect your brain, not just your physical appearance
September 9, 2019
Science Daily/Yale University
Much research has pointed to how an unhealthy diet correlates to obesity, but has not explored how diet can bring about neurological changes in the brain. A recent Yale study has discovered that high-fat diets contribute to irregularities in the hypothalamus region of the brain, which regulates body weight homeostasis and metabolism.
Led by Sabrina Diano, the Richard Sackler Family Professor of Cellular & Molecular Physiology and professor of neuroscience and comparative medicine, the study evaluated how the consumption of a high-fat diet -- specifically diets that include high amounts of fats and carbohydrates -- stimulates hypothalamic inflammation, a physiological response to obesity and malnutrition.
The researchers reaffirmed that inflammation occurs in the hypothalamus as early as three days after consumption of a high-fat diet, even before the body begins to display signs of obesity. "We were intrigued by the fact that these are very fast changes that occur even before the body weight changes, and we wanted to understand the underlying cellular mechanism," said Diano who is also a member of the Yale Program in Integrative Cell Signaling and Neurobiology of Metabolism.
The researchers observed hypothalamic inflammation in animals on a high fat diet and discovered that changes in physical structure were occurring among the microglial cells of animals. These cells act as the first line of defense in the central nervous system that regulate inflammation. Diano's lab found that the activation of the microglia was due to changes in their mitochondria, organelles that help our bodies derive energy from the food we consume. The mitochondria were substantially smaller in the animals on a high-fat diet. The mitochondria's change in size was due to a protein, Uncoupling Protein 2 (UCP2), which regulates the mitochondria's energy utilization, affecting the hypothalamus' control of energy and glucose homeostasis.
The UCP2-mediated activation of microglia affected neurons in the brain that, when receiving an inflammatory signal due to the high fat diet, stimulated the animals in the high-fat diet group to eat more and become obese. However, when this mechanism was blocked by removing the UCP2 protein from microglia, animals exposed to a high fat diet ate less and were resistant to gain weight.
The study not only illustrates how high-fat diets affect us physically, but conveys how an unhealthy diet can alter our food intake neurologically. "There are specific brain mechanisms that get activated when we expose ourselves to specific type of foods. This is a mechanism that may be important from an evolutionary point of view. However, when food rich in fat and carbs is constantly available it is detrimental."
Diano's long-standing goal is to understand the physiological mechanisms that regulate how much food we consume, and she continues to perform research on how activated microglia can affect various diseases in the brain, including Alzheimer's disease, a neurological disorder that is associated with changes in the brain's microglial cells and has been shown to have higher incidence among obese individuals.
https://www.sciencedaily.com/releases/2019/09/190909121234.htm
High-fat diet in utero protects against Alzheimer's later
August 27, 2019
Science Daily/Temple University Health System
A high-fat diet can carry health risks, but for mothers-to-be, it may make all the difference when it comes to Alzheimer's disease prevention for their children. In a report published online August 26 in the journal Molecular Psychiatry, researchers at the Lewis Katz School of Medicine at Temple University show for the first time in animals that high maternal fat consumption during gestation protects offspring against changes in the brain that are characteristic of late-onset Alzheimer's disease.
"In humans, it has been known that individuals whose mothers develop Alzheimer's disease after age 65 are at increased risk of also developing the disease around the same age," said senior investigator Domenico Praticò, MD, Scott Richards North Star Foundation Chair for Alzheimer's Research, Professor in the Departments of Pharmacology and Microbiology, and Director of the Alzheimer's Center at Temple at the Lewis Katz School of Medicine.
Genetic factors transmitted by mothers to their offspring seem like an obvious explanation behind this phenomenon, but so far no genes have been identified that could explain the maternal transmission of Alzheimer's disease. This fact would suggest that environmental factors, such as lifestyle and diet, adopted during the gestation period, a time in which mother and baby are in tight interaction, could significantly influence the offspring's risk of developing the disease later in life.
Diet is of particular interest as a risk factor, especially a diet rich in animal fat and cholesterol. High-fat intake previously has been shown in young/adult mice to directly exacerbate the types of changes in brain function that ultimately may contribute to Alzheimer's disease.
To better understand the unique relationship between maternal Alzheimer's disease and risk in her offspring, Dr. Praticò and colleagues looked at maternal fat intake specifically during the gestation period in mice engineered to develop Alzheimer's disease. Pregnant mice were fed a high-fat diet from the beginning until the end of gestation. The moment offspring were born, mothers were switched to a regular diet, which was maintained during the lactation period. Offspring of these mothers were always kept at the same regular, or standard, diet throughout their life.
At 11 months of age, offspring underwent behavioral tests to assess learning ability and memory. "Surprisingly, we found that animals from mothers fed a high-fat diet during gestation had better learning and memory skills than their counterparts born to mothers fed a regular diet during gestation," Dr. Praticò said.
The observed improvements in memory and learning were associated with the maintenance of good synaptic integrity. In fact, offspring from mothers exposed to a high-fat diet had significant improvement of synapse function when compared with offspring from mothers on a regular diet. Synapses, the places where neurons come together to relay information, play a vital role in learning and memory formation.
In addition, compared to animals born to mothers fed a regular diet, offspring from mothers on a high-fat diet had lower levels of amyloid-beta, an abnormal protein that builds up in neurons, contributing to nerve cell dysfunction and eventually significant impairments in memory and learning
When the team searched for possible mechanisms responsible for the beneficial effect, they discovered that offspring from mothers fed a high-fat diet exhibited reduced levels of three important genes involved in Alzheimer's disease: beta-secretase, tau, and the pathological tau-regulating gene CDK5. Dr. Praticò's team found that already in the early developmental stages, the three genes were effectively switched off in offspring because the high-fat diet had increased activity of a protein called FOXP2. They demonstrated that the repressive activity of FOXP2 on these genes ultimately protected offspring from later declines in brain function and Alzheimer's disease development.
"Our findings suggest that, to be effective, Alzheimer's disease prevention probably needs to start very early in life, during gestation," Dr. Praticò said. "Diet at this specific life stage can have critical, but underestimated, long-term impacts on brain health."
Dr. Praticò and colleagues plan next to compare the effects of a high-fat diet to those of other diets, including diets high in sugar and protein and diets resembling the Mediterranean diet in humans. "We also want to see whether our findings can be replicated in wild-type animals" Dr. Praticò added.
https://www.sciencedaily.com/releases/2019/08/190827084717.htm