Obesity rates have been steadily rising around the world for many years. Obesity has been linked to a variety of health problems including metabolic disorders such as type 2 diabetes and cardiovascular disease, as well as other issues, like an increased risk of cancer or infection. It is also linked to chronic inflammation that is low-grade, but could also be leading to other problems. Studies have shown that there are biomarkers of this inflammation increase in both circulation and in fat tissue.
Now researchers have used a mouse model to show how a high-fat diet could interfere with the immune system and leave the body susceptible to infection. The work suggested that a diet high in fats increases the number of neutrophils, a type of immune cell that helps fight infections. But the neutrophils that are abundant after a high-fat diet show signs of immune cells that are aged or dysfunctional, and are not good at fighting infectious pathogens like bacteria or viruses. The findings have been reported in The Journal of Immunology.
"We hope that by understanding how neutrophil function is altered with exposure to high fat diet, we can take future steps to restore function and improve patient health outcomes," said corresponding study author Dr. Kanakadurga Singer, an Associate Professor at the University of Michigan Medical School. "We hope this study lets investigators and clinicians know that although neutrophils may be increased in number in individuals with elevated BMI or diet-induced obesity, these neutrophils may not be functional."
This study used mice that were put into a group fed a normal diet, or a group fed a high-fat diet. Then the researchers collected neutrophils from these mice and analyzed them. Neutrophils from mice given a fatty diet showed that there were disruptions in gene expression, cellular metabolism, and an immune signal called TNF-alpha that helps control inflammation.
When the isolated neutrophils were exposed to a bacterial pathogen known as Pseudomonas aeruginosa, the high-fat neutrophils were less able to respond to the bacteria and destroy it.
The researchers suggested that this work has shown how high fat diets and diet-related obesity can significantly influence immune cells and immune function.
"We hope to build on these findings by uncovering what is causing the impairment of neutrophils exposed to [a high-fat diet]. My team plans to conduct further studies on why these neutrophils are defective, especially in their bacterial killing function, and if these neutrophils are impaired in killing specific types of bacteria or a wide range," added Singer.
Sources: American Association of Immunologists, Journal of Immunology
