Insulin action and resistance are dependent on a GSK3ß-FBXW7-ERRα transcriptional axis.

Insulin resistance, a harbinger of the metabolic syndrome, is a state of compromised hormonal response resulting from the dysregulation of a wide range of insulin-controlled cellular processes. However, how insulin affects cellular energy metabolism via long-term transcriptional regulation and whether boosting mitochondrial function alleviates insulin resistance remains to be elucidated. Herein we reveal that insulin directly enhances the activity of the nuclear receptor ERRα via a GSK3ß/FBXW7 signaling axis. Liver-specific deletion of GSK3ß or FBXW7 and mice harboring mutations of ERRα phosphosites (ERRα3SA) co-targeted by GSK3ß/FBXW7 result in accumulated ERRα proteins that no longer respond to fluctuating insulin levels. ERRα3SA mice display reprogrammed liver and muscle transcriptomes, resulting in compromised energy homeostasis and reduced insulin sensitivity despite improved mitochondrial function. This crossroad of insulin signaling and transcriptional control by a nuclear receptor offers a framework to better understand the complex cellular processes contributing to the development of insulin resistance.

Integrated multi-omics analysis of adverse cardiac remodeling and metabolic inflexibility upon ErbB2 and ERRα deficiency.

Functional oncogenic links between ErbB2 and ERRα in HER2+ breast cancer patients support a therapeutic benefit of co-targeted therapies. However, ErbB2 and ERRα also play key roles in heart physiology, and this approach could pose a potential liability to cardiovascular health. Herein, using integrated phosphoproteomic, transcriptomic and metabolic profiling, we uncovered molecular mechanisms associated with the adverse remodeling of cardiac functions in mice with combined attenuation of ErbB2 and ERRα activity. Genetic disruption of both effectors results in profound effects on cardiomyocyte architecture, inflammatory response and metabolism, the latter leading to a decrease in fatty acyl-carnitine species further increasing the reliance on glucose as a metabolic fuel, a hallmark of failing hearts. Furthermore, integrated omics signatures of ERRα loss-of-function and doxorubicin treatment exhibit common features of chemotherapeutic cardiotoxicity. These findings thus reveal potential cardiovascular risks in discrete combination therapies in the treatment of breast and other cancers.

Divergent Role of Estrogen-Related Receptor α in Lipid- and Fasting-Induced Hepatic Steatosis in Mice.

Given the increasing prevalence of obesity and the metabolic syndrome, identification of intrinsic molecular programs responsible for ensuring fuel homeostasis and preventing metabolic disease is needed. We investigated whether the orphan nuclear receptor estrogen-related receptor α (ERRα), a major regulator of energy metabolism, plays a role in lipid homeostasis and the development of nonalcoholic fatty liver disease (NAFLD) in response to chronic high-fat diet (HFD) consumption and long-term fasting. Systemic ablation of ERRα in mice demonstrated clear beneficial effects for loss of ERRα function in protection from HFD-provoked body weight gain manifested not only from a reduction in white adipose tissue stores but also from an impediment in intrahepatic lipid accumulation. The prevention of HFD-induced NAFLD in ERRα-null mice was underscored by transcriptional repression of de novo lipogenesis, which was upregulated in wild-type mice, a known contributing factor to lipid-stimulated hepatic steatosis. Surprisingly, given these findings, ERRα deficiency had no significant impact on the degree of fasting-induced NAFLD, involving the mobilization of adipocyte triglyceride (TG) stores into the liver. However, the presence of ERRα was essential for acute refeeding-mediated reversal of fasting-induced hepatic TG accretion, underpinned by impaired downregulation of adipose TG lipolysis and reduced hepatic mitochondrial oxidative activity. Taken together, the regulation of lipid handling by ERRα depended on the nutritional state, suggesting that negative modulation of ERRα activity could be envisaged to prevent lipid-induced NAFLD, whereas inducing its activity would be useful to treat and reverse the instilled disease.

Androgen-Dependent Repression of ERRγ Reprograms Metabolism in Prostate Cancer.

How androgen signaling contributes to the oncometabolic state of prostate cancer remains unclear. Here, we show how the estrogen-related receptor γ (ERRγ) negatively controls mitochondrial respiration in prostate cancer cells. Sustained treatment of prostate cancer cells with androgens increased the activity of several metabolic pathways, including aerobic glycolysis, mitochondrial respiration, and lipid synthesis. An analysis of the intersection of gene expression, binding events, and motif analyses after androgen exposure identified a metabolic gene expression signature associated with the action of ERRγ. This metabolic state paralleled the loss of ERRγ expression. It occurred in both androgen-dependent and castration-resistant prostate cancer and was associated with cell proliferation. Clinically, we observed an inverse relationship between ERRγ expression and disease severity. These results illuminate a mechanism in which androgen-dependent repression of ERRγ reprograms prostate cancer cell metabolism to favor mitochondrial activity and cell proliferation. Furthermore, they rationalize strategies to reactivate ERRγ signaling as a generalized therapeutic approach to manage prostate cancer. Cancer Res; 77(2); 378-89. ©2016 AACR.