A new study published in The Journal of Immunology has revealed that a high-fat diet (HFD) can weaken the immune system’s ability to respond to infections. Researchers found that a high-fat diet negatively affects neutrophils, a type of immune cell that plays a critical role in the body’s defense against bacteria and viruses.
Impact of High-Fat Diet on Neutrophils
The study, led by Dr. Kanakadurga Singer from the University of Michigan Medical School, demonstrated that male mice fed a high-fat diet to induce obesity showed an increased number of neutrophils. However, these neutrophils were immature or aged and had a reduced ability to kill bacteria. This finding points to a compromised immune response in individuals with obesity, which is often linked to chronic inflammation and higher susceptibility to infections.
Dr. Singer explained, “We hope that by understanding how neutrophil function is altered with exposure to high-fat diets, we can take future steps to restore function and improve patient health outcomes.”
The Link Between Obesity and Chronic Inflammation
Obesity affects nearly 40% of American adults and is often caused by consuming more calories than the body can burn, especially from fat- and sugar-rich diets. In recent years, obesity has been closely tied to chronic, low-grade inflammation, which contributes to several health problems, including an increased risk of infection.
Dr. Singer highlighted that while neutrophil numbers may rise in individuals with elevated body mass index (BMI) or diet-induced obesity, these cells may not function effectively. “Although neutrophils may be increased in number in individuals with elevated BMI or diet-induced obesity, these neutrophils may not be functional,” she said.
Findings on Neutrophil Dysfunction
In the study, neutrophils were collected from the blood and bone marrow of mice fed either a normal diet or a high-fat diet. Researchers found that the high-fat diet impaired the neutrophils’ ability to store and release TNF-alpha, an immune signal important for regulating inflammation. Additionally, the neutrophils from high-fat diet mice expressed genes related to fat storage and metabolism that were absent in the neutrophils from normal diet mice.
When these neutrophils were exposed to Pseudomonas aeruginosa, a bacterium known to cause pneumonia, they showed a reduced ability to ingest and kill bacteria. This further supports the idea that diet-induced obesity can weaken the immune system by affecting neutrophil function.
Next Steps for Research
The researchers plan to further investigate the reasons behind the impaired function of neutrophils exposed to a high-fat diet. Dr. Singer’s team aims to explore whether the dysfunction is specific to certain types of bacteria or if it affects a wide range of pathogens. They also hope to identify potential solutions to improve neutrophil function in individuals with obesity.
“We hope to build on these findings by uncovering what is causing the impairment of neutrophils exposed to HFD,” Dr. Singer said. “Hopefully, we can identify other implications of neutrophil dysfunction due to HFD and if there are ways to improve this impaired function.”
This study emphasizes the potential negative impact of diet on immune health, highlighting the need for further research into how dietary habits may influence the body’s ability to fight infections.
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