HomeLifestyleHealth & FitnessMom’s High-Fat Diet Affects Female And Male Brains Differently

Mom’s High-Fat Diet Affects Female And Male Brains Differently

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When they become pregnant, more than half of all American women are overweight or obese. While being overweight or gaining weight during pregnancy may pose health problems for mothers, there are also indications that it may raise the risk that their children would have psychological illnesses like autism or depression, which often affect one gender more than the other.

But how the buildup of adipose tissue in the mother may send sex-specific signals across the placenta and reorganize the growing child’s brain is still unknown.

In order to close this knowledge gap, Staci Bilbo, a professor of psychology and neuroscience at Duke University, collaborated with postdoctoral researcher Alexis Ceasrine to study pregnant mice on a high-fat diet. In a study published today in the journal Nature Metabolism, they discovered that mother’s high-fat diet causes immune cells in the developing brains of male but not female mouse pups to overconsume the mood-regulating brain chemical serotonin, resulting in depressive-like behavior.

There’s a possibility that this phenomenon is also occurring in people, according to the experts.

When someone has a mood disorder like depression, they often lose interest in things that make them happy. One naturally enjoyable pastime for mice is sipping sugar water. When given the option, mice would choose sugar water over normal tap water, therefore Ceasrine assessed this preference as a proxy for depression. Males, but not females, born to mothers who consumed a lot of fat did not prefer simple syrup over regular tap water. Ceasrine thought that the mom’s diet while she was pregnant must have changed the brains of their male offspring while they were growing up.

Serotonin was a prime suspect at first. Serotonin, sometimes known as the “happy” neurotransmitter, is a molecular brain messenger that is generally decreased in depressed individuals.

The findings of Ceasrine and her colleagues imply that these early effects have long-lasting effects since depressed-like male mice from high-fat diet mothers have less serotonin in their brains both in the womb and as adults. When tryptophan, a chemical that turns into serotonin, was added to mom’s high-fat rodent food, the males’ preference for sugar water and serotonin levels in the brain returned. However, it was still unclear how the mother’s weight gain affected their children’s serotonin levels.

To find out, the team looked into microglia, which are immune cells that live in the brain.

Microglia are sometimes referred to as the brain’s “understudied Swiss Army knives.” Their duties include acting as a hearse to transport away dead nerve cells and a security watchdog for diseases. Additionally, microglia have a large enough stomach and hunger to eat complete healthy brain cells.

Ceasrine used 3D imaging to examine the contents of the phagosome, the microglia’s cellular “stomach,” to determine whether they were overindulging in serotonin. She discovered that males born to mothers who consumed high fat diets had microglia that were packed with more serotonin than those born to mothers who consumed a typical diet. This proved that increased fat storage during pregnancy signals to microglia to overeat serotonin cells through the male but not the female placenta. But no one knew how fat can send signals through the placental barrier.

One theory suggested that germs were responsible.

“There’s a lot of evidence that when you eat a high fat diet, you actually end up with endotoxemia,” Ceasrine explains. “It basically means that you have an increase in circulating bacteria in your blood, or endotoxins, which are just parts of bacteria.”

To see if endotoxins could be the key message from mom to fetus, the team measured their presence and found that high-fat diets during pregnancy did increase endotoxin levels in both the placenta and the developing brain of the fetus. According to Ceasrine, this may help to explain how fat accumulation causes microglia to overproduce brain cells in male mice by inducing an immunological response.

Ceasrine collaborated with Susan Murphy, Ph.D., an associate professor of obstetrics and gynecology at the Duke School of Medicine, who supplied placental and fetal brain tissue from a prior research, to see if this would apply to people as well. The researchers discovered that, similar to what they saw in mice, the greater the amount of fat in human placental tissue, the less serotonin was identified in the brains of men but not females.

Bilbo and Ceasrine are only beginning to understand the unique effects that maternal obesity has on female children. Fat doesn’t make female mice depressed, but it does make them less social. This may be because they get too much of the hormone oxytocin, which makes them more social, instead of serotonin, which makes them sad.

For the time being, the findings of this study suggest that not all placentas are created equal. This research could one day help doctors and parents better understand the causes of some mood disorders and find ways to treat or prevent them by looking at early environmental factors, like the amount of fat that builds up in the womb.

So why would the placenta react differently to male and female fetuses? After Ceasrine gave a talk to Bilbo’s class, a student asked her the same question. At first, she didn’t know what to say. After a chuckle, Bilbo asked again. However, they now believe they have it figured out.

“I was hugely pregnant at the time, and I was like, ‘Oh, wait. Pregnancy!’” Ceasrine recalls. “Men never have to carry a fetus, so they never have to worry about the kind of immune response of self versus non-self that you have to do when you’re a woman and you carry a baby.”

Source: 10.1038/s42255-022-00693-8

Image Credit: Getty

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