Aim: To examine the expression of oestrogen receptors alpha and beta (ERalpha and ERbeta) and their regulation by 17beta-oestradiol (E2) 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 ERalpha and ERbeta. The regulation of ERalpha and ERbeta 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 E2 treatments differentially altered ERalpha and ERbeta 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 ERalpha (s.c.:1.87 +/- 0.22; o.m.:1.97 +/- 0.17; p < 0.05) and 60 kDa ERbeta (s.c.:1.66 +/- 0.3; o.m.: 1.68 +/- 0.16; p < 0.05). In s.c. adipocytes, however, ERalpha expression significantly decreased with E(2) 10(-8) M relative to control while ERbeta expression increased (ERalpha 0.58 +/- 0.06, ERbeta: 1.47 +/- 0.11; p < 0.05). In o.m. adipocytes, the inhibition of ERalpha with E(2) was not observed (ERalpha 1.86 +/- 0.36, ERbeta:1.03 +/- 0.15, p < 0.05)
Conclusions: ERalpha and ERbeta are expressed but differentially regulated by E(2) in s.c. and o.m. adipocytes and stromal cells. The upregulation of ERbeta by E(2) suggests that E(2) maintains the expression of these receptors. The feed-back inhibition of ERalpha expression by E(2) in s.c. but not o.m. adipocytes observed in vitro is consistent with the data from ERalpha knock out mice where s.c. fat is increased. Selective ER modulators may have different effects in different adipose sites.