White adipocytes are less prone to apoptotic stimuli than brown adipocytes in rodent

Obesity in rodents is related to a functional atrophy of brown adipose tissue (BAT), and consequent impairment of adaptive thermogenesis and increased white adipose tissue (WAT) mass.1 Further to defects in molecular processes of the adaptive thermogenesis, the BAT atrophy may be due to an increased rate of brown fat cell death.2 The expression of tumor necrosis factor (TNF)- is elevated in WAT of a variety of obese animals3 and humans,4 and TNF-receptor 1 (TNFR-1) stimulation induces brown adipocyte apoptosis both in vitro and in vivo.2, 5 Although there is some evidence that apoptosis of white adipocytes may be relevant in certain situations,6, 7 its role in WAT accumulation is not clearly defined. Here, a different sensitivity to apoptotic stimuli is reported in brown and white adipocytes, concomitant with a cell-specific expression of pro- and anti-apoptotic molecules. This difference is evident also in BAT and WAT of rats either subjected to starvation or genetically obese.