Eosinophils protect from metabolic alterations triggered by obesity

Background Eosinophils are generally related to helminth infections or allergies. Their association with metabolic alterations and adipose tissue (AT) remodeling has been demonstrated mainly in animal models of obesity. However, their physiological role in driving metabolic features has not yet been well described. Herein, we aimed to evaluate the participation of eosinophils in metabolic and adipose tissue homeostasis in mice and humans, focusing on a translational perspective. Material and methods Male BALB/c wild-type (WT) mice and GATA-1 knockout (Δdb/GATA-1−/−) mice were followed until 16-week-age in a regular diet or were fed with a high-refined-carbohydrate (HC) diet or high-fat (HF) diet for eight weeks. In subjects with obesity, clinical parameters and omental AT gene expression were evaluated. Results Eosinophils lack in mice fed a regular diet induced insulin resistance and increased adiposity. Their adipose tissue showed augmented cytokine levels, which could be attributed to increased leukocytes in the tissue, such as neutrophils and pro-inflammatory macrophages. Bone marrow transplant from WT mice to Δdb/GATA-1−/− mice showed some improvement in glucose metabolism with lower adipose tissue mass accretion. Upon an unhealthy diet challenge, Δdb/GATA-1−/− mice fed HC diet showed a mild degree of adiposity and glucose metabolic dysfunction severe in those mice fed HF diet. The expression of eosinophil markers in omental AT from humans with severe obesity was positively correlated to eosinophil cytokines and insulin sensitivity surrogate markers and negatively correlated to systemic insulin, HOMA-IR, and android fat mass. Conclusions Eosinophils seem to have a physiological role by controlling systemic and adipose tissue metabolic homeostasis by modulating glucose metabolism, inflammation, and visceral fat expansion, even in lean mice. Indeed, eosinophils also seem to modulate glucose homeostasis in human obesity.