Role of the Androgen Receptor in Insulin Secretion in the Male

这项续订申请的目的是进一步阐明睾酮作用于 雄性胰岛素分泌胰腺β细胞的雄激素受体(AR)通过扩增促进胰岛素分泌 胰升糖素样肽-1(GLP-1)的作用。睾酮缺乏在胰腺β细胞发病中的作用 男性易患2型糖尿病(T2D)的功能障碍的研究很少。虽然已经确定 睾酮的作用是通过配体激活的转录因子AR介导的，AR在β细胞中的作用 人们对其功能仍知之甚少。在此功勋奖I01BX003725的资助下，新近出版的 来自我们实验室研究AR在β细胞功能中的作用的深远的初步数据提供了 以下信息：1)β细胞AR有条件缺失的雄性小鼠(βARKO)表现为减少 葡萄糖刺激的胰岛素分泌(GSI)和β细胞无法产生足够的胰岛素，导致 T2D；2)AR的促胰岛素功能在男性捐赠者的胰岛中重现 将循环中的睾酮转化为有效的AR激动剂双氢睾酮(DHT)的酶机械； 3)DHT激活小鼠和人类β细胞的核外AR，通过放大GSIS来增强GSI 胰升糖素样肽-1在GLP-1受体上的作用，促进血浆cAMP的产生 4)DHT选择性地促进GLP-1介导的cAMP的产生和GSIS，但不能 葡萄糖-促胰岛素多肽(GIP)或胰高血糖素(GCN)的表达；5)胰岛GSIS的DHT扩增 需要酪氨酸激酶SRC，雷帕霉素复合体2(MTORC2)的哺乳动物靶标，以及 跨膜型(TMAC)和可溶性(SAC)腺苷环化酶。根据这些广泛的初步数据和 在申请中提出的先前研究的科学严谨性，我们的首要假设是在男性 β细胞、双羟色胺对质膜附近AR的作用与肌醇磷脂3-激酶结合 (PI3K)，从而募集mTORC2并增加TMAC和SAC在质膜和 内噬菌体。这增强了cAMP和GSIS的GLP-1受体(GLP-1R)的产生。DHT激活的AR IS 选择性地偏向GLP-1R，因为AR和GLP-1R唯一地融合在mTORC2信令上，以 激活TMAC和SAC，在相似的微区产生cAMP。这项拟议的工作使用了基因， 转基因小鼠以及人类胰岛和β细胞中的生理学和药理学工具。 这项工作尤其与衰老和雄激素缺乏的男性退伍军人和T2D相关 流行病，因为AR是一个特征很好的药物靶标。本申请中提出的工作目标 是阐明DHT激活的AR刺激cAMP产生并增强 GLP-1在质膜和内体发出信号以增加男性胰岛素的分泌。因此， 这项应用的具体目的是1)检验人类β细胞中AR激活增强的假设 GLP-1在与SRC对接、mTORC2招募和TMAC和TMAC激活后的促胰岛素作用 SAC，增加质膜和内小体cAMP的产生；2)揭开新型雄激素的面纱 人β细胞AR相互作用组和功能信号网络对胰岛素分泌的作用； 3)用雄激素翻译雄激素刺激小鼠体内胰岛素分泌的结果 树枝状大分子结合物，选择性激活AR膜/核外活动。拟议的工作将填补 在我们对b细胞功能的基本机制的理解上的关键差距将会有持久的 对患有糖尿病的雄激素缺乏的男性退伍军人的科学影响和开辟临床相关途径。

The goal of this renewal application is to further elucidate the mechanisms by which testosterone action on the androgen receptor (AR) in male insulin-producing pancreatic β-cells enhances insulin secretion by amplifying glucagon-like peptide-1 (GLP-1) actions. The role of testosterone deficiency as a cause of pancreatic β–cell dysfunction predisposing to type 2 diabetes (T2D) in men is poorly studied. While it is established that testosterone action is mediated via the AR, a ligand-activated transcription factor, the role of the AR in β-cell function is still poorly understood. Funded by this Merit Award I01BX003725, the new and recently published far-reaching preliminary data from our laboratory investigating the role of the AR in β-cell function provides the following information: 1) male mice with conditional deletion of the AR in β-cells (βARKO) exhibit decreased glucose-stimulated insulin secretion (GSIS) and develop β-cell failure to produce enough insulin, leading to T2D; 2) the insulinotropic function of AR is recapitulated in islets from male human donors that have the enzymatic machinery to convert circulating testosterone to the potent AR agonist dihydrotestosterone (DHT); 3) DHT activates an extranuclear AR in mouse and human β-cells that enhances GSIS by amplifying the actions of glucagon-like peptide-1 (GLP-1) on the GLP-1 receptor, increasing cAMP production at the plasma membrane and endosomes; 4) DHT selectively enhances GLP-1-mediated cAMP production and GSIS but not that of glucose-insulinotropic polypeptide (GIP) or glucagon (GCN); 5) DHT amplification of GSIS from islets requires the tyrosine kinase SRC, the mammalian target of rapamycin complex 2 (mTORC2), and the activities of transmembrane (tmAC) and soluble (sAC) adenylate cyclases. Based on this extensive preliminary data and the scientific rigor of previous research presented in the application, our overarching hypothesis is that in male β-cells, DHT action on AR in the vicinity of the plasma membrane binds SRC and phosphoinositide 3-kinase (PI3K), thus recruiting mTORC2 and increasing the activities of tmAC and sAC at the plasma membrane and endosomes. This enhances GLP-1 receptor (GLP-1R) production of cAMP and GSIS. DHT-activated AR is selectively biased toward the GLP-1R, because AR and GLP-1R uniquely converge on mTORC2 signaling to activate tmAC and sAC to produce cAMP in similar microdomains. The proposed work uses genetic, physiological and pharmacological tools in genetically modified mice, as well as in human islets and β-cells. This work is particularly relevant against to the aging and androgen-deficient male Veterans and the T2D epidemic, because the AR is a well-characterized drug target. The goal of the work proposed in this application is to elucidate the molecular bases by which DHT-activated AR stimulates cAMP production and enhances GLP-1 signaling at the plasma membrane and endosomes to increase insulin secretion in males. Accordingly, the specific aims of this application are to 1) Test the hypothesis that AR activation in human β cells enhances GLP-1 insulinotropic action following docking to SRC, recruitment of mTORC2, and activation of tmAC and sAC, which increases cAMP production at the plasma membrane and endosomes; 2) Unmask novel androgen actions on insulin secretion by mapping the AR interactome and functional signaling network in human β cells; 3) Translate the findings of androgen stimulation of insulin secretion in vivo in mice using an androgen dendrimer conjugate that selectively activates AR membrane/extranuclear actions. The proposed work will fill key gaps in our understanding of the fundamental mechanisms of b-cell function and will have a lasting scientific impact and open clinically relevant avenues for androgen-deficient male Veterans with diabetes.