Committed subcutaneous preadipocytes are reduced in human obesity

Aims/hypothesis: The aim of this study was to test whether the availability of committed preadipocytes in abdominal and femoral subcutaneous adipose tissue varies with obesity and body fat distribution. Methods: Body composition, fat cell size, committed preadipocytes and macrophages were measured in subcutaneous abdominal and femoral adipose depots of 17 lean, 16 upper-body-obese (UBO) and 13 lower-body-obese (LBO) women. Preadipocytes and macrophages were identified by simultaneous staining with the respective markers aP2 and CD68. In a subset of samples we measured preadipocyte proliferation, differentiation and susceptibility to apoptosis. Results: Abdominal adipocytes were smaller in lean than in obese women. Committed preadipocytes represented a greater fraction of stromovascular cells in lean than in obese women but were similar between UBO and LBO women (abdomen: ∼30 ± 3 vs ∼17 ± 2%; thigh: ∼30 ± 3 vs ∼17 ± 2%). Preliminary data suggested that preadipocyte kinetics were similar in LBO and lean women, whereas preadipocytes of UBO women differentiated less and were more susceptible to apoptotic stimuli. The fraction of stromovascular cells that were macrophages was greater in both depots in obese women (UBO and LBO) than in normal-weight women, but the difference was not statistically significant. Conclusions/interpretation: The proportion of subcutaneous adipose tissue stromovascular cells that are committed preadipocytes is reduced with obesity. This could be due to greater recruitment of preadipocytes to adipogenesis or greater preadipocyte apoptosis, depending upon the obesity phenotype. These data are consistent with the concept that body fat distribution may be regulated partly through differences in adipogenesis.