Coordinate regulation of neuropeptide Y and agouti-related peptide gene expression by estrogen depends on the ratio of estrogen receptor (ER) α to ERβ in clonal hypothalamic neurons

Abstract

Neuropeptide Y (NPY) and agouti-related peptide (AgRP) stimulate feeding, whereas NPY also facilitates the estrogen-mediated preovulatory GnRH surge. In addition to regulating reproductive function, estrogen also acts as an anorexigenic hormone, although it is not yet known which hypothalamic neurons are involved in this process. We hypothesize that estrogen may directly control hypothalamic NPY and/or AgRP synthesis to influence energy homeostasis. Using two clonal, murine hypothalamic neuronal cell models, N-38 and N-42, we demonstrate that 17β-estradiol differentially regulates estrogen receptor (ER)α and ERβ levels, as well as NPY and AgRP gene expression in a manner that is temporally coordinated with the changes in ER abundance. The estrogen-mediated repression of NPY and AgRP mRNA levels in N-38 and N-42 neurons require either ERα and ERβ or ERα alone, respectively, whereas the induction of NPY and AgRP in N-38 neurons is strictly ERβ dependent, as assessed by ER-specific agonists and small interfering RNA knockdown of ERα or ERβ. Through transient transfection analysis in N-38 neurons, we have mapped the estrogen-mediated repression of NPY to within -1078 of the 5′ regulatory region of the NPY gene. Our results provide the first evidence that NPY and AgRP gene expression is directly regulated by estrogen in specific hypothalamic neurons, and that this regulation is dependent upon the ratio of ERβ to ERα. The biphasic control of neuronal NPY/AgRP transcription may be a mechanism by which estrogen has distinct effects on both energy homeostasis and reproduction. Copyright © 2006 by The Endocrine Society.