The findings raise the possibility that obesity in humans has a similar effect, scientists say.
Compared to other mice of normal weight, which were otherwise identical, obese mice were 10 times as likely to die when infected with the flu virus. Four percent of lean mice died during the experiments, compared with 40 percent of the extra fat ones.
The study, presented in San Diego Saturday (April 2) at an American Society of Nutritional Sciences scientific meeting, part of a larger experimental biology meeting, is the first of its kind to examine the effects of obesity on the immune response to infection with influenza.
Nutrition doctoral student Alexia Smith and Dr. Melinda A. Beck, associate professor of pediatrics at the UNC School of Medicine, led the research and reported the findings.
"Numerous marked alterations seen in the mice's immune response suggest that the growing obese population is at increased risk for immune dysfunction during influenza infection, which may lead in humans, as it did in the mice, to increased mortality," Beck said. "Influenza virus currently is responsible for 36,000 deaths and 114,000 hospitalizations in the United States each year."
Mice are a common model in influenza virus infection studies, Beck said. In her UNC laboratory, 35 mice fed a high-fat, high-sugar diet for five months grew 37 percent heavier than 35 mice fed a regular rodent diet high in carbohydrates. The obese mice had a body fat percentage of 31 percent, compared to 21 percent in the lean mice.
"Following influenza infection at five months, which is adulthood for mice, the obese mice demonstrated significantly decreased capacity in every step of the inflammatory immune response i
Contact: David Williamson
University of North Carolina at Chapel Hill