Increased fruit and vegetable consumption prevents dysregulated immune and inflammatory responses in high-fat diet-induced obese mice.

ABSTRACT

BACKGROUND: Obesity is often associated with impaired immune responses, including enlarged spleen, increased inflammation, and impaired T cell-mediated function, which may lead to increased susceptibility to infections. Bioactive compounds found in various fruits and vegetables (F&V) have been shown to have strong anti-inflammatory effects. However, few prospective studies have examined the effects of F&V on preventing obesity-associated dysregulation of immune and inflammatory responses. OBJECTIVE: To determine the impact of different levels of a mixture of F&V incorporated in a high-fat diet (HFD) on immune function changes in a diet-induced obesity animal model. METHODS: Six-week-old male C57BL/6J mice were randomly assigned to one of five groups (n = 12/group) matched low-fat control (LF, 10% kcal fat) or high-fat diet (HFD, 45% kcal fat) supplemented with 0%, 5%, 10%, or 15% (wt/wt) freeze-dried powder of the most consumed F&V (human equivalent of 0, 3, 5-7, 8-9 servings/d, respectively) for 20 weeks. Spleen weight was recorded, and the immunophenotype of splenocytes was evaluated by flow cytometry. Ex vivo splenic lymphocyte proliferation was assessed by thymidine incorporation and serum cytokines were measured by Meso Scale Discovery. RESULTS: Mice fed the HFD had significantly higher spleen weight, decreased splenic CD8+ lymphocytes, suppressed T lymphocyte proliferation, and reduced serum IL-1ß and IFN-γ levels compared to those fed the LF diet. Feeding mice with the HFD supplemented with 10% or 15% F&V restored HFD-associated changes of these affected biomarkers compared to those fed HFD only. Further, a significant correlation was found between immunological markers and F&V level. CONCLUSIONS: These results suggest that increased consumption of F&V has beneficial effects in preventing HFD-associated dysregulation of immune function.