High-fat diet weakens immune response in mice

A new study shows that a high-fat diet (HFD) may weaken the immune system's response to infections. Published in The Journal of Immunology, the research focuses on neutrophils, which are crucial immune cells that respond quickly to infections caused by bacteria or viruses. In the study, male mice were given a high-fat diet to induce obesity. The results showed that these mice had more neutrophils, but many of these cells were either immature or old and less effective at killing bacteria. This suggests that a high-fat diet can damage the function of these important immune cells. Obesity is a growing problem in the U.S., with over 40% of adults affected. It often develops when people consume more calories than they burn, particularly from high-fat or sugary diets. Researchers noted that obesity is linked to chronic inflammation, which can make infections more likely and worsen related health issues. Dr. Kanakadurga Singer, who led the study, said understanding how a high-fat diet impacts neutrophil function could help improve health outcomes for patients. She pointed out that while obese individuals may have more neutrophils, these cells may not work effectively. The study compared neutrophils from mice on a normal diet with those on a high-fat diet. It found that neutrophils from HFD mice could not store and release an important immune signal, TNF-alpha, as well as those from normal diet mice. HFD neutrophils also showed changes in genes that affect fat storage and metabolism. When exposed to the harmful bacterium Pseudomonas aeruginosa, neutrophils from HFD mice struggled to fight off the infection. This indicates that diet-related obesity can significantly impair the immune system. Dr. Singer expressed intent to conduct further research on why neutrophils are weakened in those on high-fat diets, specifically regarding their ability to kill bacteria. The goal is to explore ways to improve the function of these immune cells.