Neurosteroid Regulation of Adiposity, Glucose Homeostasis and Energy Expenditure in Primates

雌激素（E2）在成年雌性啮齿动物中调节体重、肥胖、能量平衡、体力活动和葡萄糖稳态，如对卵巢切除术、E2替代和雌激素受体的遗传操纵的稳健代谢反应所证明的。然而，在雌性灵长类动物中，切除卵巢并不一定会导致肥胖、胰岛素抵抗或能量稳态改变。在最近的研究中，我们已经证实，无论是消融外周E2的生产，也不E2替代改变肥胖，血糖调节或能量稳态在绒猴，增加了以前的证据表明外周雌激素不发挥重要作用，在雌性灵长类动物的代谢调节。然而，我们最近的新发现证明了下丘脑雌激素受体α（ERα）在调节雌性非人灵长类动物（NHP）代谢功能中的重要性，因为下丘脑ERα基因表达的沉默会诱导成年雌性恒河猴肥胖和胰岛素抵抗。总之，这些发现表明，下丘脑ER α可能在NHP中起作用，就像在啮齿动物中一样，调节肥胖，葡萄糖调节和能量稳态，但外周产生的E2在参与这些行动中的重要性降低。最近的研究表明，神经甾体生成，特别是下丘脑的雄激素前体E2的CYP19A1芳构化，可以调节神经控制的代谢功能在NHP。因此，我们提出了一个新的假设，即在大脑中合成的E2，特别是在下丘脑腹内侧核（VMN）和弓状核（ARC）的神经元中，激活ERα来调节女性NHP的肥胖，葡萄糖调节和能量稳态。为了验证这一假设，我们将使用药理学和病毒载体介导的shRNA方法来确定肥胖、葡萄糖调节和能量代谢是否通过抑制CYP19A1芳香酶或通过永久沉默雌性恒河猴下丘脑中的CYP19A1基因而改变。我们还将通过微透析方法分析VMN和ARC中E2的合成，并确定VMN和ARC E2是否来源于下丘脑合成的雄激素。这些研究可能从根本上改变我们对女性NHP中性类固醇对肥胖、血糖调节和能量稳态的代谢控制的理解，并促进探索新的治疗策略以减少女性代谢疾病。

Estradiol (E2) in adult female rodents regulates body weight, adiposity, energy balance, physical activity and glucose homeostasis, as demonstrated by robust metabolic responses to ovariectomy, E2 replacement, and genetic manipulation of estrogen receptors. In female primates, however, removal of the ovaries does not reliably lead to increases in adiposity, insulin resistance or altered energy homeostasis. In recent studies, we have confirmed that neither ablation of peripheral E2 production nor E2 replacement alters adiposity, glucoregulation or energy homeostasis in marmoset monkeys, adding to previous evidence suggesting peripheral estrogens do not play important roles in female primate metabolic regulation. Our recent novel findings, however, demonstrate the critical importance of hypothalamic estrogen receptor alpha (ERα) in regulating metabolic function in a female nonhuman primate (NHP), as silencing of hypothalamic ERα gene expression induces obesity and insulin resistance in adult female rhesus monkeys. Taken together, these findings suggest that hypothalamic ERa may function in NHPs, as it does in rodents, to regulate adiposity, glucoregulation and energy homeostasis, yet peripherally produced E2 has diminished importance in engaging these actions. Recent studies have suggested that neurosteroidogenesis, specifically hypothalamic aromatization by CYP19A1 of androgen precursors to E2, may regulate neural control of metabolic function in NHPs. We have therefore formulated a new hypothesis that E2 synthesized in the brain, specifically in neurons of the ventromedial nucleus (VMN) and arcuate nucleus (ARC) of the hypothalamus, activates ERα to regulate adiposity, glucoregulation and energy homeostasis in female NHPs. To test this hypothesis, we will use both pharmacological and viral vector- mediated shRNA approaches to determine if adiposity, glucoregulation and energy metabolism are altered by inhibition of the CYP19A1 aromatase enzyme, or by permanent silencing of the CYP19A1 gene in the hypothalamus of female rhesus macaques. We will also analyze the synthesis of E2 in the VMN and ARC by a microdialysis approach, and determine whether VMN and ARC E2 originates from hypothalamically synthesized androgens. These studies may fundamentally change our understanding of metabolic control of adiposity, glucoregulation and energy homeostasis by sex steroids in female NHPs, and prompt exploration of new therapeutic strategies to diminish metabolic disease in women.