Estrogen Receptor α Protects Against Obesity-Induced Metabolic Dysfunction by Regulating VAT Tregs

Estrogens are important for metabolic health. Individuals with low levels of circulating estrogens, including men and postmenopausal women, exhibit an elevated risk for developing obesity-associated metabolic syndromes. Chronic low-grade inflammation in the visceral adipose tissue (VAT) is a major contributor to metabolic dysfunction during obesity. Regulatory T cells (Tregs) in the VAT limit tissue inflammation and protect against obesity-associated metabolic disease. In this study, we identify opposing roles of estrogen receptor α (ERα) in regulating VAT Tregs in female mice under steady-state and obese conditions. At steady state, ERα restrained the age-dependent clonal expansion of specific VAT Treg subsets expressing the IL-33 receptor ST2. However, during obesity, ERα-deficiency predisposed females to the loss of ST2+ VAT Tregs, exacerbating VAT inflammation and insulin resistance. These findings indicate that ERα signaling protects against obesity-induced metabolic diseases by preserving metabolically protective ST2+ VAT Treg subsets, and the loss of this protection may contribute to the heightened metabolic risk in estrogen-deficient individuals.