Submitted on March 23, 2007
Accepted on August 11, 2007
Obesity-associated mouse adipose stem cell secretion of monocyte chemotactic protein-1 (MCP-1)
Hui Ren Zhou1, Eun-Kyoung Kim2, Hyojung Kim1, and Kate J Claycombe1*
1 Food Science and Human Nutrition, Michigan State University, East Lansing, Michigan, United States
2 Food Science and Human Nutrition, Neurology and Ophthalmology, Michigan State University, East Lansing, Michigan, United States
* To whom correspondence should be addressed. E-mail: claycom3{at}msu.edu.
Studies showed that 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 the ob/ob mice compared to lean mice. In order 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 to 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 while adipose CD34+ cells have two-fold higher cell numbers (30% of total SVF cells) compared to 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 to CD34+ cells from subcutaneous adipose tissue depots. Taken together, our data suggest that adipose CD34+ stem cell may play an important role in obesity-associated increases in plasma MCP-1 levels.
