Site-specific regulation of oestrogen receptor-α and -β by oestradiol in human adipose tissue

Aim To examine the expression of oestrogen receptors alpha and alpha (ER alpha and ER beta) and their regulation by 17 beta -oestradiol (E-2) in stromal cells and adipocytes from human subcutaneous (s.c.) and omental (o.m.) adipose 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) undergoing elective or cosmetic surgery. Immunohistochemistry and RT-PCR analysis were used to detect the presence of ER alpha and ER beta. The regulation of ER alpha and ER beta by E-2 (10(-7) M to 10-(9) M) was examined using Western immunoblotting analysis in both s.c. and o.m. stromal cells and mature adipocytes cultured in serum-free, phenol red-free medium. Results Immunostaining of s.c. and o.m. adipose tissue showed that the ER subtypes were localized predominantly within the nucleus. Western analysis demonstrated 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, however, 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 beta: 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 regulated 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 receptors. 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 have different effects in different adipose sites.