Macrophage-secreted factors impair human adipogenesis: involvement of proinflammatory state in preadipocytes

Endocrinology. 2007 Feb;148(2):868-77. doi: 10.1210/en.2006-0687. Epub 2006 Nov 2.

Abstract

Obesity is considered a chronic low-grade inflammatory state. The white adipose tissue produces a variety of inflammation-related proteins whose expression is increased in obese subjects. The nonadipose cell fraction, which includes infiltrated macrophages, is a determinant source of inflammation-related molecules within the adipose tissue. Our working hypothesis is that macrophage infiltration affects fat expansion through a paracrine action on adipocyte differentiation. Human primary preadipocytes were then differentiated in the presence of conditioned media obtained from macrophages differentiated from blood monocytes. Preadipocytes treated by macrophage-conditioned medium displayed marked reduction of adipogenesis as assessed by decreased cellular lipid accumulation and reduced gene expression of adipogenic and lipogenic markers. In addition to this effect, the activation of macrophages by lipopolysaccharides stimulated nuclear factor kappaB signaling, increased gene expression and release of proinflammatory cytokines and chemokines, and induced preadipocyte proliferation. This phenomenon was associated with increased cyclin D1 gene expression and maintenance of the fibronectin-rich matrix. Anti-TNFalpha neutralizing antibody inhibits the inflammatory state of preadipocytes positioning TNFalpha as an important mediator of inflammation in preadipocytes. Strikingly, conditioned media produced by macrophages isolated from human adipose tissue exerted comparable effects with activated macrophages, i.e. decreased adipogenesis and increased inflammatory state in the preadipocytes. These data show that macrophage-secreted factors inhibit the formation of mature adipocytes, suggesting possible role in limiting adipose tissue expansion in humans.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adipocytes / pathology*
  • Adipogenesis* / drug effects
  • Adipose Tissue / metabolism
  • Biomarkers / metabolism
  • Cell Differentiation
  • Cell Proliferation / drug effects
  • Cells, Cultured
  • Chemokines / metabolism
  • Culture Media / pharmacology
  • Cyclin D1 / genetics
  • Cytokines / metabolism
  • Female
  • Gene Expression / drug effects
  • Humans
  • Inflammation / pathology
  • Inflammation / physiopathology*
  • Inflammation Mediators / metabolism
  • Lipid Metabolism / drug effects
  • Lipopolysaccharides / pharmacology
  • Macrophages / drug effects
  • Macrophages / metabolism*
  • NF-kappa B / metabolism
  • Signal Transduction / drug effects
  • Stem Cells / metabolism
  • Stem Cells / pathology*

Substances

  • Biomarkers
  • Chemokines
  • Culture Media
  • Cytokines
  • Inflammation Mediators
  • Lipopolysaccharides
  • NF-kappa B
  • Cyclin D1