Angiotensin-II mediates norepinephrine and neuropeptide-Y secretion in a human pheochromocytoma.

The potential role of angiotensin-II in mediating catecholamine and neuropeptide-Y release in a human pheochromocytoma has been investigated. Angiotensin-II type I receptors are transcribed and translated into functional proteins in a surgically removed pheochromocytoma. Primary cell culture of the tumor has been studied in a perfused system. Angiotensin-II increased the release of norepinephrine and neuropeptide-Y by the pheochromocytes. Activation of the angiotensin-II type I receptors by angiotensin-II was associated with a rise in cytosolic free calcium. The renin-angiotensin system may, therefore, contribute to the secretion of catecholamines and NPY occurring in patients with pheochromocytoma and when stimulated trigger hypertensive crisis.

Functional interaction between the estrogen receptor and CTF1: analysis of the vitellogenin gene B1 promoter in yeast.

Eukaryotic gene expression depends on a complex interplay between the transcriptional apparatus and chromatin structure. We report here a yeast model system for investigating the functional interaction between the human estrogen receptor (hER) and CTF1, a member of the CTF/NFI transcription factor family. We show that a CTF1-fusion protein and the hER transactivate a synthetic promoter in yeast in a synergistic manner. This interaction requires the proline-rich transactivation domain of CTF1. When the natural estrogen-dependent vitellogenin B1 promoter is tested in yeast, CTF1 and CTF1-fusion proteins are unable to activate transcription, and no synergy is observed between hER, which activates the B1 promoter, and these factors. Chromatin structure analysis on this promoter reveals positioned nucleosomes at -430 to -270 (+/-20 bp) and at -270 to - 100 (+/-20 bp) relative to the start site of transcription. The positions of the nucleosomes remain unchanged upon hormone-dependent transcriptional activation of the promoter, and the more proximal nucleosome appears to mask the CTF/NFI site located at - 101 to -114. We conclude that a functional interaction of hER with the estrogen response element located upstream of a basal promoter occurs in yeast despite the nucleosomal organization of this promoter, whereas the interaction of CTF1 with its target site is apparently precluded by a nucleosome.

Involvement of 4E-BP1 in the protection induced by HDLs on pancreatic beta cells.

High-density lipoproteins (HDLs) protect pancreatic beta cells against apoptosis. This property might relate to the increased risk to develop diabetes in patients with low HDL blood levels. The mechanisms by which HDLs protect beta cells are poorly characterized however. Here we used a transcriptomic approach to identify genes differentially modulated by HDLs in beta cells subjected to apoptotic stimuli. The transcript encoding 4E-BP1 was up-regulated by serum starvation and HDLs blocked this increase. 4E-BP1 inhibits cap-dependent translation in its non- or hypo-phosphorylated state but it looses this ability when hyper-phosphorylated. At the protein level, 4E-BP1 was also up-regulated in response to starvation and IL1beta and this was blunted by HDLs. While an ectopic increase of 4E-BP1 expression induced beta cell death, silencing 4E-BP1 increase with shRNAs inhibited the apoptotic-inducing capacities of starvation. HDLs can therefore protect beta cells by blocking 4E-BP1 protein expression but this is not the sole protective mechanism activated by HDLs. Indeed, HDLs blocked apoptosis induced by ER stress with no associated decrease in total 4E-BP1 induction. Although, HDLs favored the phosphorylation, and hence the inactivation of 4E-BP1 in these conditions, this appeared not to be required for HDL protection. Our results indicate that HDLs can protect beta cells through modulation of 4E-BP1 depending on the type of stress stimuli.

Prioritizing genetic testing in patients with kallmann syndrome using clinical phenotypes.

Context: The complexity of genetic testing in Kallmann syndrome (KS) is growing and costly. Thus, it is important to leverage the clinical evaluations of KS patients to prioritize genetic screening. Objective: The objective of the study was to determine which reproductive and nonreproductive phenotypes of KS subjects have implications for specific gene mutations. Subjects: Two hundred nineteen KS patients were studied: 151 with identified rare sequence variants (RSVs) in 8 genes known to cause KS (KAL1, NELF, CHD7, HS6ST1, FGF8/FGFR1, or PROK2/PROKR2) and 68 KS subjects who remain RSV negative for all 8 genes. Main Outcome Measures: Reproductive and nonreproductive phenotypes within each genetic group were measured. Results: Male KS subjects with KAL1 RSVs displayed the most severe reproductive phenotype with testicular volumes (TVs) at presentation of 1.5 ± 0.1 mL vs 3.7 ± 0.3 mL, P < .05 vs all non-KAL1 probands. In both sexes, synkinesia was enriched but not unique to patients with KAL1 RSVs compared with KAL1-negative probands (43% vs 12%; P < .05). Similarly, dental agenesis and digital bone abnormalities were enriched in patients with RSVs in the FGF8/FGFR1 signaling pathway compared with all other gene groups combined (39% vs 4% and 23% vs 0%; P < .05, respectively). Hearing loss marked the probands with CHD7 RSVs (40% vs 13% in non-CHD7 probands; P < .05). Renal agenesis and cleft lip/palate did not emerge as statistically significant phenotypic predictors. Conclusions: Certain clinical features in men and women are highly associated with genetic causes of KS. Synkinesia (KAL1), dental agenesis (FGF8/FGFR1), digital bony abnormalities (FGF8/FGFR1), and hearing loss (CHD7) can be useful for prioritizing genetic screening.

Leptin inhibits directly glucocorticoid secretion by normal human and rat adrenal gland.

Different interactions have been described between glucocorticoids and the product of the ob gene leptin. Leptin can inhibit the activation of the hypothalamo-pituitary-adrenal axis by stressful stimuli, whereas adrenal glucocorticoids stimulate leptin production by the adipocyte. The present study was designed to investigate the potential direct effects of leptin to modulate glucocorticoid production by the adrenal. Human adrenal glands from kidney transplant donors were dissociated, and isolated primary cells were studied in vitro. These cells were preincubated with recombinant leptin (10(-10)-10(-7) M) for 6 or 24 h, and basal or ACTH-stimulated cortisol secretion was subsequently measured. Basal cortisol secretion was unaffected by leptin, but a significant and dose-dependent inhibition of ACTH-stimulated cortisol secretion was observed [down by 29 +/- 0.1% of controls with the highest leptin dose, P &lt; 0.01 vs. CT (unrelated positive control)]. This effect of leptin was also observed in rat primary adrenocortical cells, where leptin inhibited stimulated corticosterone secretion in a dose-dependent manner (down by 46 +/- 0.1% of controls with the highest leptin dose, P &lt; 0.001 vs. CT). These effects of leptin in adrenal cells are likely mediated by the long isoform of the leptin receptor (OB-R), because its transcript was found to be expressed in the adrenal tissue and leptin had no inhibitory effect in adrenal glands obtained from db/db mice. Therefore, leptin inhibits directly stimulated cortisol secretion from human and rat adrenal glands, and this may represent an important mechanism to modulate glucocorticoid levels in various metabolic states.

Association between C-reactive protein and adiposity in women.

Context: The link between C-reactive protein (CRP) and adiposity deserves to be further explored considering the controversial diabetogenic role of CRP. Objective: We explored the potential causal role of CRP on measures of adiposity. Design: We used a Mendelian randomization approach with the CRP and LEPR genes as instrumental variables in a cross-sectional Caucasian population-based study comprising 2526 men and 2836 women. Adiposity was measured using body mass index (BMI), fat and lean mass estimated by bioelectrical impedance, and waist circumference. Results: Log-transformed CRP explained by the rs7553007 SNP tagging the CRP gene was significantly associated with BMI (regression coefficient: 1.22 [0.18;2.25], P=0.02) and fat mass (2.67 [0.65;4.68], P=0.01), but not with lean mass in women, whereas no association was found in men. Log-transformed CRP explained by the rs1805096 LEPR SNP was also positively associated, although not significantly, with BMI or fat mass. The combined CRP-LEPR instrument explained 2.24% and 0.77% of CRP variance in women and in men, respectively. Log-transformed CRP explained by this combined instrument was significantly associated with BMI (0.98 [0.32;1.63], P=0.004), fat mass (2.07 [0.79;3.34], P=0.001) and waist (2.09 [0.39;3.78], P=0.01) in women, but not in men. Conclusion: Our data suggest that CRP is causally and positively related to BMI in women, and that this is mainly due to fat mass. Results on the combined CRP-LEPR instrument suggest that leptin may play a role in the causal association between CRP and adiposity in women. Results in men were not significant.

An Essential Role for Insulin and IGF1 Receptors in Regulating Sertoli Cell Proliferation, Testis Size, and FSH Action in Mice.

Testis size and sperm production are directly correlated to the total number of adult Sertoli cells (SCs). Although the establishment of an adequate number of SCs is crucial for future male fertility, the identification and characterization of the factors regulating SC survival, proliferation, and maturation remain incomplete. To investigate whether the IGF system is required for germ cell (GC) and SC development and function, we inactivated the insulin receptor (Insr), the IGF1 receptor (Igf1r), or both receptors specifically in the GC lineage or in SCs. Whereas ablation of insulin/IGF signaling appears dispensable for GCs and spermatogenesis, adult testes of mice lacking both Insr and Igf1r in SCs (SC-Insr;Igf1r) displayed a 75% reduction in testis size and daily sperm production as a result of a reduced proliferation rate of immature SCs during the late fetal and early neonatal testicular period. In addition, in vivo analyses revealed that FSH requires the insulin/IGF signaling pathway to mediate its proliferative effects on immature SCs. Collectively, these results emphasize the essential role played by growth factors of the insulin family in regulating the final number of SCs, testis size, and daily sperm output. They also indicate that the insulin/IGF signaling pathway is required for FSH-mediated SC proliferation.

Glucagon-like peptide-1-(7-36) amide, oxyntomodulin, and glucagon interact with a common receptor in a somatostatin-secreting cell line.

Glucagon-like peptide-1(7-36)amide (tGLP-1), oxyntomodulin (OXM), and glucagon are posttranslational end products of the glucagon gene expressed in intestinal L-cells. In vivo, these peptides are potent inhibitors of gastric acid secretion via several pathways, including stimulation of somatostatin release. We have examined the receptors through which these peptides stimulate somatostatin secretion using the somatostatin-secreting cell line RIN T3. tGLP-1, OXM, and glucagon stimulated somatostatin release and cAMP accumulation in RIN T3 cells to similar maximum levels, with ED50 values close to 0.2, 2, and 50 nM and 0.02, 0.3, and 8 nM, respectively. Binding of [125I]tGLP-1, [125I]OXM, and [125I]glucagon to RIN T3 plasma membranes was inhibited by the three peptides, with relative potencies as follows: tGLP-1 &gt; OXM &gt; glucagon. Whatever the tracer used, the IC50 for tGLP-1 was close to 0.15 nM and was shifted rightward for OXM and glucagon by about 1 and 2-3 orders of magnitude, respectively. Scatchard analyses for the three peptides were compatible with a single class of receptor sites displaying a similar maximal binding close to 2 pmol/mg protein. In the hamster lung fibroblast cell line CCL39 transfected with the receptor for tGLP-1, binding of [125I]tGLP-1 was inhibited by tGLP-1, OXM, and glucagon, with relative potencies close to those obtained with RIN T3 membranes. Chemical cross-linking of [125I]tGLP-1, [125I]OXM, and [125I]glucagon revealed a single band at 63,000 mol wt, the intensity of which was dose-dependently reduced by all three peptides. These data suggest that in the somatostatin-secreting cell line RIN T3, OXM and glucagon stimulate somatostatin release through a tGLP-1-preferring receptor. This suggests that some biological effects, previously described for these peptides, might be due to their interaction with this receptor.

Immunolocalization of GLUTX1 in the testis and to specific brain areas and vasopressin-containing neurons.

GLUTX1 or GLUT8 is a newly characterized glucose transporter isoform that is expressed at high levels in the testis and brain and at lower levels in several other tissues. Its expression was mapped in the testis and brain by using specific antibodies. In the testis, immunoreactivity was expressed in differentiating spermatocytes of type 1 stage but undetectable in mature spermatozoa. In the brain, GLUTX1 distribution was selective and localized to a variety of structures, mainly archi- and paleocortex. It was found in hippocampal and dentate gyrus neurons as well as amygdala and primary olfactory cortex. In these neurons, its location was close to the plasma membrane of cell bodies and sometimes in proximal dendrites. High GLUTX1 levels were detected in the hypothalamus, supraoptic nucleus, median eminence, and the posterior pituitary. Neurons of these areas synthesize and secrete vasopressin and oxytocin. As shown by double immunofluorescence microscopy and immunogold labeling, GLUTX1 was expressed only in vasopressin neurons. By immunogold labeling of ultrathin cryosections microscopy, GLUTX1 was identified in dense core vesicles of synaptic nerve endings of the supraoptic nucleus and secretory granules of the vasopressin positive neurons. This localization suggests an involvement of GLUTX1 both in specific neuron function and endocrine mechanisms.

PPARgamma in placental angiogenesis.

Peroxisome proliferator-activated receptor γ (PPARγ) is a nuclear receptor involved in diverse biological processes including adipocyte differentiation, glucose homeostasis, and inflammatory responses. Analyses of PPARγ knockout animals have been so far preempted by the early embryonic death of PPARγ-/- embryos as a consequence of the severe alteration of their placental vasculature. Using Sox2Cre/PPARγL2/L2 mice, we obtained fully viable PPARγ-null mice through specific and total epiblastic gene deletion, thereby demonstrating that the placental defect is the unique cause of PPARγ-/- embryonic lethality. The vasculature defects observed in PPARγ-/- placentas at embryonic d 9.5 correlated with an unsettled balance of pro- and antiangiogenic factors as demonstrated by increased levels of proliferin (Prl2c2, PLF) and decreased levels of proliferin-related protein (Prl7d1, PRP), respectively. To analyze the role of PPARγ in the later stage of placental development, when its expression peaks, we treated pregnant wild-type mice with the PPARγ agonist rosiglitazone. This treatment resulted in a disorganization of the placental layers and an altered placental microvasculature, accompanied by the decreased expression of proangiogenic genes such as Prl2c2, vascular endothelial growth factor, and Pecam1. Together our data demonstrate that PPARγ plays a pivotal role in controlling placental vascular proliferation and contributes to its termination in late pregnancy.

Pancreatic islet adaptation to fasting is dependent on peroxisome proliferator-activated receptor alpha transcriptional up-regulation of fatty acid oxidation.

The cellular response to fasting and starvation in tissues such as heart, skeletal muscle, and liver requires peroxisome proliferator-activated receptor-alpha (PPARalpha)-dependent up-regulation of energy metabolism toward fatty acid oxidation (FAO). PPARalpha null (PPARalphaKO) mice develop hyperinsulinemic hypoglycemia in the fasting state, and we previously showed that PPARalpha expression is increased in islets at low glucose. On this basis, we hypothesized that enhanced PPARalpha expression and FAO, via depletion of lipid-signaling molecule(s) for insulin exocytosis, are also involved in the normal adaptive response of the islet to fasting. Fasted PPARalphaKO mice compared with wild-type mice had supranormal ip glucose tolerance due to increased plasma insulin levels. Isolated islets from the PPARalpha null mice had a 44% reduction in FAO, normal glucose use and oxidation, and enhanced glucose-induced insulin secretion. In normal rats, fasting for 24 h increased islet PPARalpha, carnitine palmitoyltransferase 1, and uncoupling protein-2 mRNA expression by 60%, 62%, and 82%, respectively. The data are consistent with the view that PPARalpha, via transcriptionally up-regulating islet FAO, can reduce insulin secretion, and that this mechanism is involved in the normal physiological response of the pancreatic islet to fasting such that hypoglycemia is avoided.

CDK9 regulates AR promoter selectivity and cell growth through serine 81 phosphorylation.

Previously we determined that S81 is the highest stoichiometric phosphorylation on the androgen receptor (AR) in response to hormone. To explore the role of this phosphorylation on growth, we stably expressed wild-type and S81A mutant AR in LHS and LAPC4 cells. The cells with increased wild-type AR expression grow faster compared with parental cells and S81A mutant-expressing cells, indicating that loss of S81 phosphorylation limits cell growth. To explore how S81 regulates cell growth, we tested whether S81 phosphorylation regulates AR transcriptional activity. LHS cells stably expressing wild-type and S81A mutant AR showed differences in the regulation of endogenous AR target genes, suggesting that S81 phosphorylation regulates promoter selectivity. We next sought to identify the S81 kinase using ion trap mass spectrometry to analyze AR-associated proteins in immunoprecipitates from cells. We observed cyclin-dependent kinase (CDK)9 association with the AR. CDK9 phosphorylates the AR on S81 in vitro. Phosphorylation is specific to S81 because CDK9 did not phosphorylate the AR on other serine phosphorylation sites. Overexpression of CDK9 with its cognate cyclin, Cyclin T, increased S81 phosphorylation levels in cells. Small interfering RNA knockdown of CDK9 protein levels decreased hormone-induced S81 phosphorylation. Additionally, treatment of LNCaP cells with the CDK9 inhibitors, 5,6-dichloro-1-β-D-ribofuranosylbenzimidazole and Flavopiridol, reduced S81 phosphorylation further, suggesting that CDK9 regulates S81 phosphorylation. Pharmacological inhibition of CDK9 also resulted in decreased AR transcription in LNCaP cells. Collectively these results suggest that CDK9 phosphorylation of AR S81 is an important step in regulating AR transcriptional activity and prostate cancer cell growth.