Foxp3+ regulatory T cells control hypothalamic inflammation

The central nervous system (CNS) hypothalamus controls systemic metabolism. Inflammatory CNS processes evolving upon exposure to calorie-rich diet are thought to promote impaired metabolic CNS control, thereby triggering obesity and Type-2 diabetes (T2D). However, immune cells relevant for maintaining hypothalamic integrity remain incompletely understood. Here, we identify hypothalamic CD4+Foxp3+regulatory T(Treg) cells which control local tissue-inflammation. Specifically, upon exposure to a calorie-rich diet, a significant decline in hypothalamus-residing Foxp3+Tregs occurred and was accompanied by increased immune activation of CD4+T cells, infiltrating macrophages and microglia. Microglial proteomes of mice exposed to the hypercaloric challenge confirmed characteristics of immune activation; specifically, mRNA expression profiling of hypothalamic CD4+T cells indicated a Th1-mediated inflammatory state evidenced by high levels of Tbx21, Cxcr3, Cd226 and reduced expression of Ccr7 and S1P1 receptors relevant for recruitment to and retention at inflammatory sites. Using Treg depletion and transfer experiments in vivo, we found that Foxp3+Tregs critically limit hypothalamic immune activation induced by hyper-caloric challenge. Our findings open new avenues in the design of tailored concepts to improve immunometabolic health in obesity and T2D.