Estrogen-Related Receptor

Estrogen receptors operate similarly to a lock and key. Estrogen works as the key to a receptor (lock) on the outside of a specific cell. These locks are not the same in every organ. Estrogen stimulates the growth of breast cells and may also stimulate the growth of breast cancer. Drugs referred to as selective estrogen receptor modulators (SERMs) were developed to prevent estrogen from stimulating the growth of breast cells that could become cancerous by blocking the estrogen receptors in the breast.

Estrogen-related receptors (ERRs), specifically ERR α, are an orphan member of the superfamily of nuclear receptors. An orphan receptor is one that has no known ligands (proteins that bind to it). ER and ERR α are related in that they bond to DNA sites. ERR α binds to DNA targets by the process of transcription.

Research has been conducted with mice as to the role ERR α may play in the body. This research hypothesizes a possible connection to intestinal fat transport and may play a role in bone remodeling. It is also thought that ERR α is present at high levels in tissues having high oxidative properties. It is theorized that there may be a linkage to estrogen signaling and oxidative metabolism An increase in energy demand such as during fasting, exercise, or cold exposure requires [Page 232]an elevated level of ERR α. In studies on mice, ERR α was removed, creating a defect in thermogenic function. ERR α appears to be high in tissue which has high oxidative capacity.

Estrogen, the female hormone produced by the ovaries, has been linked to both breast cancer and obesity.

It is theorized that ERR α plays a role during times of metabolic stress and dietary lipid digestion and absorption. There may be a link to high expression of ERR α in brown fat by lipid metabolism and transport, which are significant, factors in energy balance.

Research is continuing to determine the role ERR plays in thermogenic function and homeostasis. ERR may play a role in lipid metabolism and energy balance.