Summary: Obesity generates a pro-inflammatory state contributing to immune dysregulation and metabolic disease. In response to overnutrition, adipose tissue immune cells undergo dynamic changes featuring a shift from a type 2 anti-inflammatory phenotype in lean adipose tissue to a pro-inflammatory phenotype in obese adipose tissue, contributing to obesity associated adipose tissue inflammation featuring an accumulation of macrophages and T cells. However, the mechanism(s) that regulate the balance between anti-inflammatory and pro-inflammation ATT phenotypes with obesity are not understood. We sought to investigate how and if ATT cells respond to early obesity. We characterized the temporal and phenotypic changes in ATTs in response to initial adipose tissue remodeling, using short-term high fat diet (stHFD) as a model. We enriched for CD45+ immune cells from the eWAT of male mice fed a ND or a HFD for 14d, FACS sorted CD3+ CD11b- ATTs, and performed Cellular Indexing of Transcriptomes and Epitopes by sequencing (CITE-Seq) with immune cell profiling. CITE-seq demonstrated a decrease in Tregs and γδ T cells with an increase in a novel Th2 cell population with immune regulatory capacities featuring expression of the immunoregulatory cytokine Tgfb1, and an activated gene expression profile featuring an increase in Nr4a1 and Itk, in VAT with 14 days of HFD. This study represents the first description of a Th2 regulatory cell population in adipose tissue, and its increase with short-term HFD suggests underexplored mechanisms of ATT subpopulation activation and regulation.

Contributed by: Ramiah D. Jacks, Peizi Wu, Jennifer L. Delproposto, Carey N. Lumeng