Novel insights into glucocorticoid‐mediated diabetogenic effects: towards expansion of therapeutic options?

At pharmacological concentrations, glucocorticoids (GCs) display potent anti-inflammatory effects, and are therefore frequently prescribed by physicians to treat a wide variety of diseases. Despite excellent efficacy, GC therapy is hampered by their notorious metabolic side effect profile. Chronic exposure to increased levels of circulating GCs is associated with central adiposity, dyslipidaemia, skeletal muscle wasting, insulin resistance, glucose intolerance and overt diabetes. Remarkably, many of these side-effects of GC treatment resemble the various components of the metabolic syndrome (MetS), in which indeed subtle disturbances in the hypothalamic-pituitary-adrenal (HPA) axis and/or increased tissue sensitivity to GCs have been reported. Recent developments have led to renewed interest in the mechanisms of GC's diabetogenic effects. First, 'selective dissociating glucocorticoid receptor (GR) ligands', which aim to segregate GC's anti-inflammatory and metabolic actions, are currently being developed. Second, at present, selective 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) inhibitors, which may reduce local GC concentrations by inhibiting cortisone to cortisol conversion, are evaluated in clinical trials as a novel treatment modality for the MetS.
In this review, we provide an update of the current knowledge on the mechanisms that underlie GC-induced dysmetabolic effects. In particular, recent progress in research into the role of GCs in the pathogenesis of insulin resistance and beta-cell dysfunction will be discussed.     

Dissociation kinetics of the thyrotropin-receptor complex. Characterization of a slowly dissociable component

The kinetics of the dissociation of thyrotropin (TSH) from human thyroid plasma membranes were studied in an attempt to further understand the molecular dynamics of the TSH--receptor interaction. Dissociation of bound [125I]TSH from thyroid plasma membranes was a biphasic process consisting of rapidly and slowly dissociable components, RDC and SDC, respectively. The dilution induced dissociation of bound [125I]TSH was enhanced by the addition of excess TSH (DEC). DEC was proportional to the dose of unlabeled TSH and its magnitude increased linearly with temperature. These results are in contrast to those reported for the kinetics of [125I]insulin dissociation. The functional significance of DEC remains largely unexplained. It was found that the fraction of SDC was dependent upon time of association in a temperature-dependent and apparently saturable process. It could not be attributed to alterations in the electrophoretic, immunologic or binding properties of [125I]TSH. Furthermore, no correlation was observed between generation of SDC and change in the Scatchard profile of TSH binding, in contrast to studies on growth hormone. These data suggest that, like some other polypeptide hormones, binding of TSH to its receptor does not proceed according to laws describing simple, rapidly reversible, bimolecular reactions. Furthermore, bound TSH undergoes a receptor-mediated conversion from a rapidly to a slowly dissociable state with time of incubation.     

人表皮干细胞改良培养及其组织工程皮肤的构建

目的：改良传统人表皮干细胞（hESCs）分离、培养方法,为组织工程皮肤构建提供产率更高、活力更好的种子细胞。方法：应用改良的酶消化法（改良法）及传统酶消化法（传统法）分离、培养hESCs,倒置显微镜观察细胞形态,MTT法绘制生长曲线、免疫组化法测定hESCs标志物角蛋白19（K19）和β1整合素的表达,并且进一步比较上述两种方法所获种子细胞构建的组织工程皮肤的形态学的特性。结果：台盼蓝染色显示改良法细胞消化分离数为92.25±15.61个,传统法细胞消化分离数为68.50±26.91个（P〈0.01）;改良法活细胞比率是（94±0.01）%,传统法活细胞比率是（75±0.04）%（P〈0.05）。在8天时改良法细胞MTT法OD值为1.300,传统法为0.779,改良法较传统法活力好,增殖快;细胞免疫组织化学染色显示表皮干细胞标志物角蛋白19（K19）和β1整合素均为阳性染色;HE染色结果显示采用改良法hESCs构建的组织工程皮肤表皮细胞复层层数为5～6层、基底细胞排列整齐,传统法hESCs构建的组织工程皮肤表皮细胞复层层数为3～4层、基底细胞排列散乱。结论：利用改良的酶消化法可获得数量更多、活力更好的人表皮干细胞,为以hESCs为种子细胞构建组织工程皮肤奠定基础。     

急性分离Meynert核团神经元方法及其应用

目的 建立急性分离Meynert核团神经元方法.方法 切取活脑组织切片,经Protease酶解消化、孵育后,机械分离Meynert核团神经元.作形态学观察,通过单细胞膜片钳技术记录电活动.结果 分离出的Meynert核团神经元,倒置相差显微镜下形态保持良好,突起较完整.90%以上细胞可以记录出电活动.结论 本方法可以获取活的Meynert核团单个神经元,用于单细胞膜片钳、激光共聚焦、流式细胞术等研究.     

Pharmacology of glucocorticoids: beyond receptors

Glucocorticoid hormones are important regulators of homeostasis. They are used clinically as highly effective anti-inflammatory compounds and have been prescribed for more than fifty years for a variety of conditions. They mediate their genomic actions by binding to two different intracellular receptors in target cells. The pharmacology of glucocorticoids largely depends on ligand concentration and receptor expression levels in target tissue. However, their genomic actions also critically depend on coactivators and corepressors recruitment. We discuss how various non-receptor factors affect glucocorticoid potency and efficacy with respect to their genomic effects. Differential recruitment of coregulators may account for many ligand- and cell-specific effects of glucocorticoids. This is best illustrated by the recent identification of selective glucocorticoid receptor agonists that induce distinct conformational changes to the receptors resulting in altered protein–protein interactions and consequently different regulation of gene expression. We conclude that these new molecular insights will contribute to the design of safer glucocorticoids that retain full pharmacological properties with reduced side-effects.