The pear-shaped body is healthier than the shape of the apple

Whether we like it or not, everyone accumulates fat.

For women, it usually builds up around the hips, giving a pear-shaped appearance. In men, the fat tends to accumulate around the abdomen, thus creating an apple shape.

In fact, it is healthier to be a pear than an apple.

A research team at the University of California at Riverside found that only male mice suffered neuroinflammation or activation of the immune system response in the brain after receiving a high-fat diet. Although females were not affected, males showed low testosterone and decreased sperm count, in addition to neuroinflammation.

The results of the study appear in the review Frontiers in immunology.

Clinical studies have led researchers to believe that females are protected against weight gain when they are young due to the presence of estrogen in the ovary. The understanding was that women gain weight after menopause due to a precipitous drop in estrogen, resulting in lower health parameters, including obesity.

"We addressed this hypothesis by eliminating the ovaries in young mice," said Djurdjica Coss, an associate professor of biomedical sciences at UCR's Faculty of Medicine, who led the study. "We found that mice gain weight when they follow a high-fat diet, suggesting that ovarian hormones provide good protection against weight gain, but we also found that these female mice showed no neuroinflammation. that they are protected by factors other than ovarian estrogen.

Coss added that the results, derived from the mouse study, could have applications in humans.

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"Fat-rich mice develop a metabolic syndrome – a constellation of conditions including type 2 diabetes and insulin insensitivity – in the same way as obese humans," she said. "Obese men have lower testosterone levels, contributing to low libido, low energy, and reduced muscle strength." Male obese mice also had a nearly 50% decrease in testosterone and sperm. It is interesting to note that 18% of couples in the US now require medical interventions – hormone treatments, in vitro fertilization – to conceive a child, is a likely factor. "

The increase in obesity is a public health problem in the United States, where more than 30% of people are obese and over two-thirds are overweight. Obesity has been associated with mental decline and increased rates of stroke, in addition to other internal organ problems. In the United States, some minority ethnic groups are disproportionately affected by obesity.

Women and female mice lay fat differently from their male counterparts. Females deposit fat subcutaneously just below the skin, while males accumulate fat deeper in the visceral area of ​​the body, which can affect internal organs.

Finally, even in women, the subcutaneous regions are submerged with fat and the abdominal area begins to show obesity, which leads to neuroinflammation.

"Although overweight, women are more protected than men when it comes to neuroinflammation," Coss said. "This could be an evolutionary protection for women who need to change weight because of pregnancy.This protection is significantly reduced when overweight women become obese and fat is gathered around the waist."

Then, Coss and his team will explore, in mice, the link between abdominal weight and neuroinflammation.

"We know that abdominal fat – that is, fat around visceral organs – becomes more inflamed with fat overload," she said. "This fat then recruits immune cells from the bloodstream that are activated."

Another important finding reported in the study is that peripheral immune cells, especially macrophages, cross the blood-brain barrier – the protective barrier that stops the flow of most blood compounds to the brain . This infiltration of peripheral immune cells into the brain occurs in addition to the activation of resident immune cells.

"The brain has been considered an" immune site ", but we show that peripheral inflammation" overflows "into the brain, which can cause neuronal problems mentioned above," Coss said.

Coss explained that the causes of this activation are unclear and that his research team is planning additional investigations.

"We know that immune cells secrete cytokines, inflammatory markers, into the blood.These cytokines may travel in the blood from adipose tissue and activate immune cells to cross the blood-brain barrier." "It is also possible that other immune cells contribute to neuroinflammation, and obviously our work has generated a number of research questions that we would like to answer."

Coss acknowledged that weight is a sensitive topic, even for clinicians who have trouble talking to patients.

"After all, we associate food with happiness, social interaction and family reunions," she said. "Still, my advice is:" Watch your diet! And keep an eye on the weight of the body, especially around the abdomen. "