Estrogen Receptor-β-selective Ligands Alleviate High-fat Diet- and Ovariectomy-induced Obesity in Mice

Abstract

Obesity is an epidemic problem affecting millions of people in the Western hemisphere and costs the United States economy more than $200 billion annually. Currently, there are no effective treatments to combat obesity. Recent studies have implicated the constitutive activity of estrogen receptor (ER) ␤ as an important regulator of metabolic diseases. However, the potential of ER-␤-selective ligands to offset obesity is not clear. We evaluated the pharmacological effect of ER-␤-selective ligands (␤-LGNDs) in animal models of high-fat diet-and ovariectomyinduced obesity. Ligand binding, transactivation, and uterotrophic studies with ␤-LGNDs demonstrated selectivity for ER-␤ over ER-␣. Animals fed a high-fat diet showed a significant increase in body weight, and this weight gain was attenuated by ␤-LGNDs. High-fat diet-mediated increases in serum cholesterol, leptin, glucose, and fat accumulation in organs were also reduced by ␤-LGNDs. In addition, MRI scanning indicated that ␤-LGNDs altered body composition by reducing fat mass and increasing lean body mass. Organ weights and gene expression analyses demonstrated that adipose tissue is the center of action for ␤-LGNDs, and the reduction in body weight is likely due to increased energy expenditure. In vitro and in vivo mechanistic studies indicated that the anti-obesity effects of ␤-LGNDs were due to indirect peroxisome proliferator-activated receptor ␥ antagonistic actions requiring the ligand binding domain of ER-␤ and through abrogation of the ability of PGC-1 to coactivate peroxisome proliferator-activated receptor ␥. In conclusion, these studies indicate that ligand-activated ER-␤ is a potential therapeutic target to combat obesity and obesity-related metabolic diseases.Obesity is an epidemic disease affecting over 400 million people globally (1). Two-thirds of adults and children in the United States are either overweight or obese, making it a serious health risk and economic burden to society (2). Obesity is not a standalone disease, as its emergence leads to various complications, including type 2 diabetes mellitus (T2DM), 3 hypertension, atherosclerosis, and other cardiovascular diseases, osteoporosis, and clinical depression (3, 4). The United States Food and Drug Administration required an anti-obesity drug to reduce the body weight by 5% and/or better results than placebo in 12 months, indicating that even a marginal reduction in body weight will cause a significant improvement in the welfare of these patients (5). Despite the exponentially growing global obesity pharmaceutical market, only two Food and Drug Administration-approved drugs are available for this indication: 1) amphetamines and sibutramine that act on the hypothalamus to control appetite stimulation in the central nervous system, and 2) Orlistat, which is a lipase inhibitor that blocks gastrointestinal absorption of fat and decreases energy uptake (6). Despite mediocre performance, these drugs are commonly associated with side effects such as tachycardia, hypertension, fecal incontinence, ...

Role of Nuclear Receptors in Lipid Dysfunction and Obesity-Related Diseases

“…The results conclusively demonstrated that the effects were not due to the cross reactivity with ER-a, as evidenced by the lack of hypothalamus-pituitary-gonadal axis activation and uterine weight increase (Yepuru et al, 2010).…”

“…4) for 12 weeks. The body weights of mice fed with a high-fat diet and treated with an ER-b-selective agonist were significantly lower than those of vehicle-treated mice fed with a high-fat diet and were not different from the body weights of mice maintained on a normal diet (Yepuru et al, 2010). In addition to the body weight changes, we observed favorable changes in other biomarkers of metabolism, including cholesterol, leptin, and glucose tolerance.…”

“…Magnetic resonance imaging of mice in these obesity studies revealed that ER-b ligands not only reduced body fat but also increased the muscle mass (Yepuru et al, 2010). This observation is very unique to this class of anti-obesity drugs and has not been demonstrated as a function of ER-b or its ligands.…”

“…To further rule out the possibility that GPCRs could have played a role in the anti-obesity effect of ER-b-selective agonists, cross-reactivity against a panel of known GPCRs was evaluated. ER-b-selective ligands did not cross react with any of the tested GPCRs, indicating that these ligands and their anti-obesity effects are highly selective for ER-b (Yepuru et al, 2010).…”

“…4A), displaying 10-to 100-fold selectively toward ER-b over ER-a (Yepuru et al, 2010). Although their binding to and transactivation of ER-b was similar to that of estradiol, they bound and activated ER-a at much lower potency and efficacy.…”