RESUMO
Leptin, an adipocyte-derived hormone, has emerged as a critical regulator of energy homeostasis. The leptin receptor (Lepr) is expressed in discrete regions of the brain; among the sites of highest expression are several mediobasal hypothalamic nuclei known to play a role in energy homeostasis, including the arcuate nucleus, the ventromedial hypothalamic nucleus (VMH), and the dorsomedial hypothalamic nucleus. Although most studies have focused on leptin's actions in the arcuate nucleus, the role of Lepr in these other sites has received less attention. To explore the role of leptin signaling in the VMH, we used bacterial artificial chromosome transgenesis to target Cre recombinase to VMH neurons expressing steroidogenic factor 1, thereby inactivating a conditional Lepr allele specifically in steroidogenic factor 1 neurons of the VMH. These knockout (KO) mice, designated Lepr KO(VMH), exhibited obesity, particularly when challenged with a high-fat diet. On a low-fat diet, Lepr KO(VMH) mice exhibited significantly increased adipose mass even when their weights were comparable to wild-type littermates. Furthermore, these mice exhibited a metabolic syndrome including hepatic steatosis, dyslipidemia, and hyperleptinemia. Lepr KO(VMH) mice were hyperinsulinemic from the age of weaning and eventually developed overt glucose intolerance. These data define nonredundant roles of the Lepr in VMH neurons in energy homeostasis and provide a model system for studying other actions of leptin in the VMH.
Assuntos
Adiposidade/genética , Síndrome Metabólica/genética , Receptores para Leptina/genética , Núcleo Hipotalâmico Ventromedial/metabolismo , Animais , Composição Corporal/genética , Peso Corporal/genética , Ingestão de Alimentos/genética , Sistema Endócrino/fisiologia , Metabolismo Energético/genética , Feminino , Glucose/metabolismo , Homeostase/genética , Integrases/genética , Masculino , Camundongos , Camundongos Knockout , Neurônios/metabolismo , Especificidade de Órgãos , Receptores para Leptina/metabolismoRESUMO
OBJECTIVE: Steroidogenic factor 1 (SF1), officially designated NR5A1, is a nuclear receptor that plays key roles in endocrine development and function. Previous reports of human SF1 mutations revealed a spectrum of phenotypes affecting adrenal function and/or gonadal development and sex differentiation. We present the clinical phenotype and functional effects of a novel SF1 mutation. PATIENT: The patient is a 22-year-old 46, XY Japanese patient who presented with dysgenetic testes, atrophic vasa deferentia and epididymides, lack of Müllerian structures, and clitoromegaly. Endocrine studies revealed normal adrenal function. RESULTS: Analysis of the SF1 gene revealed compound heterozygosity for a previously described p.G146A polymorphism and a novel missense mutation (p.R84C) in the accessory DNA-binding domain. The father carried the p.G146A polymorphism and the mother had the p.R84C mutation; both were clinically and reproductively normal. Functional studies demonstrated that the p.R84C SF1 had normal nuclear localization but decreased DNA-binding affinity and transcriptional activity compared with wild-type SF1; it did not exhibit any dominant negative activity. CONCLUSIONS: These results describe the human phenotype that results from compound heterozygosity of the p.G146A polymorphism and a novel p.R84C mutation of SF1, thereby extending the spectrum of human SF1 mutations that impair testis development and sex differentiation in a sex-limited manner while preserving normal adrenal function.
Assuntos
Proteínas de Ligação a DNA/genética , Disgenesia Gonadal 46 XY/genética , Proteínas de Homeodomínio/genética , Receptores Citoplasmáticos e Nucleares/genética , Fatores de Transcrição/genética , Insuficiência Adrenal/genética , Insuficiência Adrenal/fisiopatologia , Adulto , Células Cultivadas , Análise Mutacional de DNA , Proteínas de Ligação a DNA/metabolismo , Ensaio de Desvio de Mobilidade Eletroforética , Feminino , Imunofluorescência , Disgenesia Gonadal 46 XY/metabolismo , Proteínas de Homeodomínio/metabolismo , Humanos , Luciferases/genética , Mutação/fisiologia , Plasmídeos/genética , Polimorfismo Genético/genética , Polimorfismo Genético/fisiologia , Receptores Citoplasmáticos e Nucleares/metabolismo , Fator Esteroidogênico 1 , Receptores alfa dos Hormônios Tireóideos/genética , Fatores de Transcrição/metabolismo , Transcrição GênicaRESUMO
The nuclear receptor steroidogenic factor 1 (Sf1, Nr5a1) is essential for adrenal development and regulates genes that specify differentiated adrenocortical function. The transcriptional coactivator beta-catenin reportedly synergizes with Sf1 to regulate a subset of these target genes; moreover, Wnt family members, signaling via beta-catenin, are also implicated in adrenocortical development. To investigate the role of beta-catenin in the adrenal cortex, we used two Sf1/Cre transgenes to inactivate conditional beta-catenin alleles. Inactivation of beta-catenin mediated by Sf1/Cre(high), a transgene expressed at high levels, caused adrenal aplasia in newborn mice. Analysis of fetal adrenal development with Sf1/Cre(high)-mediated beta-catenin inactivation showed decreased proliferation in presumptive adrenocortical precursor cells. By contrast, the Sf1/Cre(low) transgene effected a lesser degree of beta-catenin inactivation that did not affect all adrenocortical cells, permitting adrenal survival to reveal age-dependent degeneration of the cortex. These results define crucial roles for beta-catenin--presumably as part of the Wnt canonical signaling pathway--in both embryonic development of the adrenal cortex and in maintenance of the adult organ.