Active glucocorticoid levels are elevated in the adipose tissue of obesity due to the enzyme 11 beta-hydroxysteroid dehydrogenase type 1. Glucocorticoids can bind and activate both glucocorticoid receptor (GR) and mineralocorticoid receptor (MR), and pharmacological blockades of MR prevent high-fat diet-induced obesity and glucose intolerance. To determine the significance of MR in adipocytes, we generated adipocyte-specific MR-knockout mice (AdipoMR-KO) and fed them high-fat/high-sucrose diet. We found that adipocyte-specific deletion of MR did not affect the body weight, fat weight, glucose tolerance or insulin sensitivity. While liver weight was slightly reduced in AdipoMR-KO, there were no significant differences in the mRNA expression levels of genes associated with lipogenesis, lipolysis, adipocytokines and oxidative stress in adipose tissues between the control and AdipoMR-KO mice. The results indicated that MR in mature adipocytes plays a minor role in the regulation of insulin resistance and inflammation in high-fat/high-sucrose diet-induced obese mice.
Tomoaki Hayakawa, Tomomi Minemura, Toshiharu Onodera, Jihoon Shin, Yosuke Okuno, Atsunori Fukuhara, Michio Otsuki and Iichiro Shimomura
Lovisa Lundholm, Milica Putnik, Michio Otsuki, Sandra Andersson, Claes Ohlsson, Jan-Åke Gustafsson and Karin Dahlman-Wright
Obesity has become a major health problem in many parts of the world. Estrogens are known to reduce adipose tissue mass in both humans and animals but the molecular mechanisms are not well characterized. We used gene expression profiling to study long-term effects of estrogen on gene expression in mouse white adipose tissue and hypothalamus. Overall, the effects of estrogen on hypothalamic gene expression were much smaller than the corresponding effects on white adipose tissue gene expression. We characterize in detail estrogenic regulation of glutathione peroxidase 3 (GPX3). Our studies suggest that GPX3 is a direct estrogen receptor α target gene in white adipose tissue. Since obesity is correlated with oxidative stress, and GPX3 has been demonstrated to be lower in obesity and higher after weight loss, we hypothesize that GPX3 is one important mediator of effects of estrogen in relation to fat mass. Additional genes that were affected by estrogen in adipose tissue include cell death-inducing DNA fragmentation factor, α-subunit-like effector A (CIDEA), a gene shown to be related to body fat in mice. We conclude that estrogen has large effects on gene expression in white adipose tissue and hypothesize that GPX3 and CIDEA could be important mediators of the effects of estrogen on fat mass.