Macrophage-colony stimulating factor in obese adipose tissue: studies with heterozygous op/+ mice.

OBJECTIVE: We examined the gene expression of macrophage-colony stimulating factor (M-CSF) in mice with diet-induced obesity and in genetically obese mice. We also examined the effect of decreased M-CSF signaling on the susceptibility to obesity and macrophage recruitment into the adipose tissue of mice. RESEARCH METHODS AND PROCEDURES: The adipose tissue from mice with diet-induced obesity, obese KKA(y) mice, and ob/ob obese mice was used for RNA preparation. Production of M-CSF and monocyte chemoattractant protein-1 (MCP-1) was examined by quantitative real-time polymerase chain reaction (PCR) and enzyme-linked immunosorbent assay. The op/+ heterozygous mice, with decreased functional M-CSF expression, were placed on a high-fat diet or crossed with KKA(y) mice to study the susceptibility to obesity. The gene expression of macrophage markers in adipose tissue was examined.
RESULTS: The expression of M-CSF was not significantly changed in mice on a high-fat diet or in either type of genetic obesity (KKA(y) or ob/ob mice). No change in the degree of obesity or macrophage-related gene expression (F4/80, CD68, and MCP-1) in the adipose tissue was observed in op/+ mice compared with +/+ control mice, which were either treated with a high-fat diet or crossed with KKA(y) mice. DISCUSSION: This study demonstrated that there was no significant change in the expression of M-CSF in the adipose tissue from obese mice and only a minor phenotypic change, such as macrophage infiltration, in the adipose tissue from op/+ mice, suggesting that M-CSF does not play a major role in macrophage recruitment in the adipose tissue of obese mice.