Altered macrophage-like functions of preadipocytes in inflammation and genetic obesity

Abstract

We recently demonstrated that preadipocytes exhibit functional features of macrophages, such as phagocytosis and anti-microbial activity, suggesting that preadipose cells could play a role in the inflammatory process or immune response. The aim of this study was to compare these functions of both macrophages and cells from stroma-vascular fraction (SVF) of the adipose tissue in two different situations, obesity and inflammation, characterized by alterations in immune responsiveness. We demonstrated that ob/ob mice exhibited strong decrease in antimicrobial activity of both macrophages and SVF. This defect is compensated in SVF, at least in part, by an enhancement of phagocytosis that does not seem to be due to an increased macrophage number. In vitro leptin treatment of SVF and macrophages from obese mice did not restore their immune defects. Thioglycollate treatment of lean and obese mice induced an inflammatory process that led to an increase in macrophage activity in both strains. This stimulation also observed in SVF from lean mice is not present in obese ones. This work demonstrated that SVF immune functions could be modified in different pathological situations such as inflammation and obesity and sustained the new physiological role of preadipocytes in these processes.

Increased expression of inflammation-related genes in cultured preadipocytes/stromal vascular cells from obese compared with non-obese Pima Indians

“…For example, it has been postulated that macrophages resident in adipose tissue contribute to obesity-associated inflammation and insulin resistance [4,5]. Furthermore, it has been shown that preadipocytes/SVC can function as macrophage-like cells and may play a direct role in inflammation response and obesity [6,7].…”

Absence of CC Chemokine Ligand 2 Does Not Limit Obesity-Associated Infiltration of Macrophages Into Adipose Tissue

“…These have been implicated in the pathogenesis of insulin resistance and cardiovascular disease (3,4,6,11). Recent studies have shown that obese adipose tissue exhibits increased infiltration by macrophages and, moreover, that macrophages may be a primary source of proinflammatory factors (12)(13)(14)(15)(16). Thus, macrophage infiltration into adipose tissue may be an important contributor to the enhanced inflammatory activity in obesity.…”

Semicarbazide-Sensitive Amine Oxidase/Vascular Adhesion Protein-1 Deficiency Reduces Leukocyte Infiltration into Adipose Tissue and Favors Fat Deposition

“…[7][8][9] Macrophages have been observed in crown-like structures aggregating around adipocytes. 10,11 Furthermore, a correlation between adipocyte size or fat mass and macrophage marker expression has been found in adipose depots of different murine models of obesity.…”