Assessment of Metabolic Regulation by Estrogen Receptors

Estrogens, predominantly 17β-estradiol (E2), are a class of steroid hormones critical for diverse functions in the body both during normal physiology and disease. Primary actions of E2 include reproduction and development of secondary sexual characteristics. In addition, E2 action is involved in the nervous, immune, vascular, muscular, skeletal, and endocrine systems, all of which contribute to multiple aspects of metabolism. The actions of E2 have traditionally been attributed to the classical nuclear estrogen receptors (ERα and ERβ) that largely mediate transcriptional/genomic activities. However, over the last decade, the G protein-coupled estrogen receptor (GPER/GPR30) has become recognized as a mediator of rapid as well as transcriptional actions of E2, employing both in vitro and in vivo approaches. Recent evidence strongly supports the role of GPER in metabolic regulation. Murine genetic knockout (KO) models and pharmacological tools (agonists and antagonists) represent important approaches to understand the mechanisms of E2 action in physiology and disease via GPER. Studies in cells and GPER KO mice have revealed functions for GPER in the regulation of body weight and metabolism. This chapter focuses on methods relevant for the evaluation of metabolic parameters in vivo, ex vivo, and in vitro. We have emphasized glucose homeostasis through the determination of glucose and insulin tolerance, pancreatic islet function, and glucose uptake. In addition, we describe methods of adipocyte isolation, differentiation of preadipocytes, and evaluation of mitochondrial function.