Obesity is one of the most common health problems affecting millions across the world. It has been, over the years, linked to several chronic diseases like heart disease and diabetes. However, a new research study has come up with a new dimension for its impacts: it causes a significant reduction in sperm count by changing the functioning of the brain.
In a landmark study, University of California-Riverside researchers teased apart the complex mechanisms through which obesity leads to reduced fertility. According to a study in the Journal of Neuroscience, using mice fattened up on a high-fat diet to model aspects of human obesity, scientists demonstrated how chronic changes in the brain disrupt reproductive function.
According to research, obesity leads to a decreased number of neuronal connections and receptors in the brain responsible for the signaling of energy sufficiency. That perturbation might be able to explain why, even after continuing to overeat, obese subjects do not cut back on their calorie intake. Djurdjica Coss, biomedical sciences professor at UC Riverside and lead author of the study, explained, “This could explain why we don’t cut back on our calorie intake.”
Key among the findings of this study was dysregulation of the hypothalamic-pituitary-gonadal axis, a critical pathway underpinning reproductive function. In obese mice, lower levels of pituitary gland hormones contributed to lower testosterone and sperm counts. The primary site where the effects of obesity manifest is in the brain rather than in the testes or pituitary gland, according to Coss, disrupting the normal functioning of neurons that govern reproduction.
Fewer synaptic connections were found in neurons responsible for reproduction in mice fed a high-fat diet similar to mechanisms found in humans. “We counted the numbers of synapses in the neurons that regulate reproduction in the brain and identified fewer synaptic connections in the mice that were fed a high-fat diet,” Coss explained.
While the study did not investigate whether these changes in the brain might be passed down the generations, the team plans to explore if reversal of the high-fat diet would be enough to restore normal brain function. Coss said that he hopes that eventually when people struggling with obesity finally reach the point where they begin to lose weight, their brains will reset how much food their bodies require.
“For many people, the fight against obesity is a losing battle. We hope to show that after a certain amount of time following weight loss, the brain is able to reset the body’s food intake, which would help people struggling to lose weight,” Coss said.
It highlights how, at the very center, the brain is working to play a pivotal role in this complex interplay of obesity on reproductive health. As obesity rates continue to climb, understanding these mechanisms will become increasingly important for the development of effective interventions against this global health crisis.