Estrogen reduces pro-inflammatory cytokines in rodent adipose tissue: studies in vivo and in vitro.

Obesity is associated with an increased risk of developing insulin resistance, Type 2 diabetes, and cardiovascular disease. Reports have suggested that adipose tissue-derived cytokines such as tumor necrosis factor-alpha, interleukin-6 and interleukin-8 could be involved in the development of these health complications. Since estrogen has been suggested to attenuate the development of atherosclerosis and cardiovascular disease, we investigated whether ovariectomy affected the production and release of these three adipose tissue-derived cytokines with and without estrogen replacement in vivo and in vitro. Female Wistar rats were submitted to either a) ovariectomy, b) ovariectomy and estrogen replacement, or c) sham operation. After five months, animals were sacrificed and parametrial adipose tissue was removed and incubated for up to 24 hours with either interleukin-1beta (IL-1beta) (5 micro g/l), dexamethasone (50 nM) or estrogen (50 nM). Ovariectomy significantly increased interleukin-6 gene expression (p < 0.05) as well as interleukin-8 protein levels (p < 0.05) and gene expression (p < 0.05) in the adipose tissue, and estrogen replacement significantly reversed this increase (p < 0.05). However, no direct effects of estrogen were found in in vitro adipose tissue incubations. Neither ovariectomy nor estrogen replacement had any effects on tumor necrosis factor-alpha protein levels or gene expression. In conclusion, estrogen-deficient rats were found to have increased production of interleukin-6 and interleukin-8, which could be attenuated by estrogen-replacement. Since estrogen is suggested to be anti-atherosclerotic, this effect might be caused by a reduction in cytokine production from the adipose tissue.