Obesity-associated mouse adipose stem cell secretion of monocyte chemotactic protein-1

Studies showed that monocyte chemotactic protein-1 (MCP-1) concentrations are increased in obesity. In our current study, we demonstrate that plasma MCP-1 level in leptin-deficient ob/ob mice is significantly higher than in lean mice. Furthermore, we determined that basal adipose tissue MCP-1 mRNA levels are significantly higher in ob/ob mice compared with lean mice. To determine the mechanisms underlying obesity-associated increases in plasma and adipose tissue MCP-1 levels, we determined adipose tissue cell type sources of MCP-1 production. Our data show that adipose tissue stem cells (CD34⁺), macrophages (F4/80⁺), and stromal vascular fraction (SVF) cells express significantly higher levels of MCP-1 compared with adipocytes under both basal and lipopolysaccharide (LPS)-stimulated conditions. Furthermore, basal and LPS-induced MCP-1 secretion levels were the same for both adipose F4/80 ⁺ and CD34⁺ cells, whereas adipose CD34⁺ cells have twofold higher cell numbers (30% of total SVF cells) compared with F4/80⁺ macrophages (15%). Our data also show that CD34⁺ cells from visceral adipose tissue depots secrete significantly higher levels of MCP-1 ex vivo when compared with CD34⁺ cells from subcutaneous adipose tissue depots. Taken together, our data suggest that adipose CD34 ⁺ stem cells may play an important role in obesity-associated increases in plasma MCP-1 levels.