Estrogen as a key regulator of energy homeostasis and metabolic health

Over the last two decades, it has become evident that estrogens preserve the integrity of energy homeostasis at central and peripheral levels. Estrogen deficiency, such as that caused by menopause or ovariectomy, has been linked to obesity and metabolic disorders that can be resolved or reversed by estrogen therapy. 17β-estradiol (E2), as the major estrogen in the body, primarily regulates energy balance via estrogen receptor alpha (ERα). At the central level, E2 plays its catabolic role predominantly by interacting with hypothalamic arcuate neurons and sending signals via ventromedial hypothalamic neurons to control brown adipose tissue-mediated thermogenesis. In peripheral tissues, several organs, particularly the liver, brown and white adipose tissues, and pancreatic β cells, have attracted considerable attention. In this review, we focused on the current state of knowledge of "central and peripheral" estrogen signaling in regulating energy balance via "nuclear and extranuclear pathways" in both "females and males". In this context, according to an exploratory approach, we tried to determine the principal estrogen receptor subtype/isoform in each section, the importance of extranuclear-initiated estrogen signaling on metabolic functions, and how sex differences related to ER signaling affect the prevalence of some of the metabolic disorders. Moreover, we discussed the data from a third viewpoint, understanding the clinical significance of estrogen signaling in abnormal metabolic conditions such as obesity or being on a high-fat diet. Collectively, this review exposes novel and important research gaps in our current understanding of dysmetabolic diseases and can facilitate finding more effective treatment options for these disorders.