Endocrine Abstracts

Dehydroepiandrosterone (DHEA) is an adrenal sex steroid whose levels decline during normal aging. Epidemiological studies demonstrate inverse correlation between circulating DHEA-sulphate and body fat mass while DHEA administration in elderly subjects reduces visceral and subcutaneous fat accumulation. Although previous studies have shown that some effects may be mediated via DHEA-induced inhibition of white pre-adipocyte proliferation, mechanisms remain unknown. Furthermore, comparative analyses with brown pre-adipocytes, now recognised to have important thermogenic properties in adipose tissue, are lacking.

We aimed to compare the effects of DHEA on white and brown pre-adipocyte proliferation/differentiation.

3T3-L1 (murine white pre-adipocyte) and PAZ6 (human brown pre-adipocyte) cells were exposed to increasing concentrations of DHEA and cell numbers determined using Coulter counting. Cell cycle analysis was performed using flow Cytometry. Spontaneous and PPARγ-induced pre-adipocyte differentiation was determined via colourimetric measurement of oil red O accumulation.

DHEA caused a concentration-dependent inhibition of 3T3-L1 and PAZ6 proliferation at 24 (1 μM DHEA: 71.55±1.79% of controls (3T3-L1) P<0.001; 84.4±4.7% (PAZ6) non-significant) and 48 hours (1 μM DHEA: 29.3±1.97% (3T3-L1) P<0.001; 50.4±4.2% (PAZ6) P<0.001). Cell cycle analysis demonstrated that inhibition was not mediated by increased apoptosis but was accompanied by an increase in the proportion of cells accumulating in G₂/M, (1μM DHEA for 48 hours: 18.2±0.07% (3T3L1), 14.4±1.1% (control) P<0.001; 34.8±0.76% (PAZ6), 32.5±1.42% (control) P=0.0038).In contrast, our results suggest DHEA stimulates spontaneous differentiation in PAZ6 but not 3T3-L1 cells.

DHEA inhibits white and brown pre-adipocyte cell proliferation by either blocking cell division or causing cell cycle arrest. It appears to stimulate differentiation of brown adipose cells. These results are potentially important in disorders of adipose tissue excess.