Demonstration of estrogen receptor subtypes alpha and beta in human adipose tissue: influences of adipose cell differentiation and fat depot localization

A novel ER-subtype, the ER-beta has recently been characterized in various tissues, furthermore five isoforms of the ER-beta are known (ER-beta1 -ER-b eta5). Using immunoblotting and real- time RT-PCR, ER-alpha and beta were s tudied in human adipose tissue. The expression of ER-alpha mRNA was equal i n subcutaneous gluteal adipose tissue. subcutaneous abdominal and intra-abd ominal adipose tissue. similar findings were obtained at the protein level. In contrast the amount of ER-beta1 (protein and mRNA) was significantly lo wer in intra-abdominal adipose tissue as compared with the subcutaneous adi pose tissue (five-fold lower in women, P < 0.005 and three-fold lower in me n, P < 0.005) whereas the expression of ER-beta4 and -beta5 mRNA isoforms w ere significantly higher in gluteal adipose tissue compared to subcutaneous abdominal adipose tissue. No significant gender differences in ER expressi on was detected in any of the fat depots investigated. During adipocyte dif ferentiation the expression of ER-alpha, -beta4 and -beta5 mRNA declined, w hereas, the expression of ER-beta1 mRNA was constant. In conclusion, the ex istence of ER-beta isoforms in human adipose tissue was demonstrated and th e amount of these receptors was dependent upon fat depot localization, with much reduced expression of ER-beta1 in intra-abdominal adipose tissue comp ared to subcutaneous adipose tissue. These findings may indicate that estro gens could have differentiation and depot specific effects in human adipose tissue. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved.