Unraveling the connection between eosinophils and obesity.

Obesity affects more than 650 million adults worldwide and is a major risk factor for a variety of serious comorbidities. The prevalence of obesity has tripled in the past forty years and continues to rise. Eosinophils have recently been implicated in providing a protective role against obesity. Decreasing eosinophils exacerbates weight gain and contributes to glucose intolerance in high fat diet-induced obese animals, while increasing eosinophils prevents high-fat diet-induced adipose tissue and body weight gain. Human studies, however, do not support a protective role for eosinophils in obesity. More recent animal studies have also reported conflicting results. Considering these contradictory findings, the relationship between eosinophils and obesity may not be unidirectional. In this mini-review, we summarize a recent debate regarding the role of adipose tissue eosinophils in metabolic disorders, and discuss local and systemic effects of eosinophils in obesity. Given that adipose eosinophils play a role in tissue homeostasis, more research is needed to understand the primary function of adipose tissue eosinophils in their microenvironment. Therapeutic interventions that target eosinophils in adipose tissue may have the potential to reduce inflammation and body fat, while improving metabolic dysfunction in obese patients. ©2020 Society for Leukocyte Biology.