Eosinophils Sustain Adipose Alternatively Activated Macrophages Associated with Glucose Homeostasis

Eosinophils are associated with helminth immunity and allergy, often in conjunction with alternatively activated macrophages (AAMs). Adipose tissue AAMs are necessary to maintain glucose homeostasis and are induced by the cytokine interleukin-4 (IL-4). Here, we show that eosinophils are the major IL-4-expressing cells in white adipose tissues of mice, and, in their absence, AAMs are greatly attenuated. Eosinophils migrate into adipose tissue by an integrin-dependent process and reconstitute AAMs through an IL-4- or IL-13-dependent process. Mice fed a high-fat diet develop increased body fat, impaired glucose tolerance, and insulin resistance in the absence of eosinophils, and helminth-induced adipose tissue eosinophilia enhances glucose tolerance. Our results suggest that eosinophils play an unexpected role in metabolic homeostasis through maintenance of adipose AAMs.