Site-specific regulation of oestrogen receptor-alpha and -beta by oestradiol in human adipose tissue

Aim To examine the expression of oestrogen receptors alpha and alpha (ER al pha and ER beta) and their regulation by 17 beta -oestradiol (E-2) in strom al cells and adipocytes from human subcutaneous (s.c.) and omental (o.m.) a dipose tissue. Methods Subcutaneous and o.m. abdominal adipose tissues were obtained from 10 women (mean age 63.5 +/-4.8 years; mean weight 75.6 +/-6.7 kg) undergoin g elective or cosmetic surgery. Immunohistochemistry and RT-PCR analysis we re used to detect the presence of ER alpha and ER beta. The regulation of E R alpha and ER beta by E-2 (10(-7) M to 10-(9) M) was examined using Wester n immunoblotting analysis in both s.c. and o.m. stromal cells and mature ad ipocytes cultured in serum-free, phenol red-free medium. Results Immunostaining of s.c. and o.m. adipose tissue showed that the ER s ubtypes were localized predominantly within the nucleus. Western analysis d emonstrated that E-2 treatments differentially altered ER alpha and ER beta expression in s.c. and o.m. adipocytes. In s.c. and o.m. stromal cells, E- 2 (10(-8) M) produced a significant up regulation relative to control of 66 kDa ERa (s.c.:1.87 +/-0.22; o.m.:1.97 +/-0.17; p<0.05) and 60 kDa ER<beta> (s.c.:1.66 +/-0.3; o.m.: 1.68 +/-0.16; p<0.05). In s.c. adipocytes, howeve r, ER<alpha> expression significantly decreased with E-2 10(-8) M relative to control while ER beta expression increased (ER alpha 0.58 +/-0.06, ER be ta: 1.47 +/-0.11; p<0.05). In o.m. adipocytes, the inhibition of ER<alpha> with E-2 was not observed (ER alpha 1.86 +/-0.36, ER beta :1.03 +/-0.15, p< 0.05) Conclusions ER<alpha> and ER beta are expressed but differentially regulate d by E2 in s.c. and o.m. adipocytes and stromal cells. The upregulation of ER beta by E-2 suggests that E-2 maintains the expression of these receptor s. The feed-back inhibition of ER alpha expression by E-2 in s.c. but not o .m. adipocytes observed in vitro is consistent with the data from ER alpha knock out mice where s.c. fat is increased. Selective ER modulators may hav e different effects in different adipose sites.