The role of estrogen and estrogen receptor-alpha in male adipose tissue

Males and females both express estrogen receptor (ER) in white adipose tiss ue (WAT), and estrogens appear to play an important role in regulating WAT in females. However, the role of ER in male WAT was unclear. In this review , we describe our work, which used wild type (WT) and ER alpha -knockout (a lpha ERKO) male and female mice to determine the rule of ER alpha in regula ting WAT and blown adipose tissue (BAT). There were progressive increases i n WAT with advancing age in alpha ERKO compared with WT males; weights of v arious WAT depots in alpha ERKO males were increased by more than 100% comp ared with WT controls during adulthood. Conversely, BAT weight was similar in alpha ERKO and WT males at all ages. Adipocyte areas and numbers were al so increased in WAT from alpha ERKO compared with WT males. Compared with W T controls, alpha ERKO females also had increases in WAT. The alpha ERKO mi ce also had insulin resistance and impaired glucose tolerance, similar to h umans lacking ER alpha or aromatase. The obesity in alpha ERKO males appear ed to involve decreased energy expenditure rather than hyperphagia. In summ ary, ER alpha absence causes adipocyte hyperplasia and hypertrophy in WAT. but not BAT, and is accompanied by insulin resistance and glucose intoleran ce in both males and females. These results are the first evidence that the estrogen/ER alpha signaling system is critical in female and male WAT depo sition, and may have clinical implications. (C) 2001 Elsevier Science irela nd Ltd. All rights reserved.