Infections love junk food

A study published in The Journal of Immunology examined how a high-fat diet (HFD) can impair the immune system, potentially making individuals more susceptible to infections. Researchers found that obesity induced by HFD altered the function of neutrophils, a type of white blood cell that serves as a first responder to infections.

The study, conducted on male mice, demonstrated that those fed a high-fat diet had an increased number of neutrophils. However, many of these cells displayed markers of immaturity or aging and were less effective at eliminating bacteria. Researchers also discovered that neutrophils from HFD-fed mice had a reduced ability to store and release TNF-alpha, a critical immune signaling molecule that regulates inflammation.

“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 Kanakadurga Singer, MD, lead researcher and associate professor at the University of Michigan Medical School.

The findings contribute to the growing body of research linking obesity with chronic inflammation and increased vulnerability to infections. With 40.3% of American adults classified as obese, understanding how diet-induced obesity affects immune cell function is crucial for addressing public health concerns.

Neutrophils from HFD-fed mice were also found to express different genes related to fat storage and metabolism compared to those on a normal diet. When exposed to Pseudomonas aeruginosa, a bacterium that can cause pneumonia, neutrophils from obese mice had a diminished ability to ingest and kill bacteria.

“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,” Singer said.

The research team aims to further investigate the specific mechanisms behind neutrophil impairment in individuals with obesity and explore potential ways to restore their function. “Hopefully, we can identify other implications of neutrophil dysfunction due to HFD and if there are ways to improve this impaired function,” Singer said.