Researchers at the University of California, Riverside, has found that male mice who were fed a high-fat diet experienced neuroinflammation, or activation of the immune system’s response in the brain. They also showed low testosterone and reduced sperm count. Female mice were unaffected, according to a study in the Frontiers in Immunology journal.
Researchers believe females are protected against weight gain when they are young because of ovarian estrogen. It is thought that women gain weight after menopause because of a drop in estrogen, resulting in a decline in health parameters, including obesity. “We addressed this assumption by removing ovaries in young mice,” said Djurdjica Coss, an associate professor of biomedical sciences in the UCR School of Medicine, who led the study. “We found that the mice proceed to gain weight when fed a high-fat diet, suggesting that ovarian hormones are indeed protective against weight gain. But we found, too, that these female mice exhibit neither neuroinflammation, nor changes in reproductive hormones, suggesting that they are protected by factors other than ovarian estrogen. This is a novel finding.”
The findings, derived from the mouse study, are likely to have applications in humans, Coss added. “Mice on high-fat diet develop metabolic syndrome — a constellation of pathologies that includes Type 2 diabetes and insulin insensitivity — similarly to obese humans,” she said. “Obese men have lower testosterone levels, contributing to low libido, low energy, and reduced muscle strength. We see this in mice, too; obese male mice showed nearly 50 percent decreases in testosterone and sperm number. Interestingly, 18 percent of couples in the United States now need medical interventions — hormonal treatments, in vitro fertilization — to conceive a child. Obesity is a likely factor.”