Lipid-associated macrophages are more abundant in subcutaneous than visceral adipose tissue in patients with obesity.

Objective: Because white adipose tissue is infiltrated by several immune cells and their signature in individuals with obesity has not been fully characterized, we wanted to study the most abundant population, which is macrophages, a subtype of myeloid cell.

Methods: To address this objective, we performed transcriptomic analysis of subcutaneous adipose tissue (SAT)- and visceral adipose tissue (VAT)-infiltrated CD11b⁺ myeloid cells from individuals with severe obesity.

Results: Our results showed that gene expression in human white adipose tissue-infiltrated CD11b⁺ myeloid cells was depot-dependent. The expression of lipid-associated macrophage biomarkers was higher in SAT- than VAT-infiltrated CD11b⁺ cells (TREM2, CD9, GPNMB, CD68). In contrast, VAT-infiltrated CD11b⁺ cells overexpressed genes associated with a perivascular M2-like adipose tissue macrophage signature (LYVE1, TIMD4, MRC1). In addition, no classical gene expression polarization (M1 and M2) was shown when VAT and SAT CD11b⁺ cells were compared. Finally, high levels of CD248, a sensor of lipids associated with insulin resistance, were found to be overexpressed in SAT- compared with VAT-infiltrated CD11b⁺ myeloid cells.

Conclusions: This study characterizes for the first time the macrophage biomarker signature in human VAT- and SAT-infiltrated CD11b⁺ myeloid cells from individuals with severe obesity. Further studies are required to elucidate their potential role and specific function in the immunometabolism of individuals with obesity.