Neurocentre Magendie



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13/04/2018 | Mol Metab   IF 6.8
mTORC1-dependent increase in oxidative metabolism in POMC neurons regulates food intake and action of leptin.
Haissaguerre M, Ferriere A, Simon V, Saucisse N, Dupuy N, Andre C, Clark S, Guzman-Quevedo O, Tabarin A, Cota D

OBJECTIVE: Nutrient availability modulates reactive oxygen species (ROS) production in the hypothalamus. In turn, ROS regulate hypothalamic neuronal activity and feeding behavior. The mechanistic target of rapamycin complex 1 (mTORC1) pathway is an important cellular integrator of the action of nutrients and hormones. Here we tested the hypothesis that modulation of mTORC1 activity, particularly in Proopiomelanocortin (POMC)-expressing neurons, mediates the cellular and behavioral effects of ROS. METHODS: C57BL/6J mice or controls and their knockout (KO) littermates deficient either for the mTORC1 downstream target 70-kDa ribosomal protein S6 kinase 1 (S6K1) or for the mTORC1 component Rptor specifically in POMC neurons (POMC-rptor-KO) were treated with an intracerebroventricular (icv) injection of the ROS hydrogen peroxide (H2O2) or the ROS scavenger honokiol, alone or, respectively, in combination with the mTORC1 inhibitor rapamycin or the mTORC1 activator leptin. Oxidant-related signal in POMC neurons was assessed using dihydroethidium (DHE) fluorescence. RESULTS: Icv administration of H2O2 decreased food intake, while co-administration of rapamycin, whole-body deletion of S6K1, or deletion of rptor in POMC neurons impeded the anorectic action of H2O2. H2O2 also increased oxidant levels in POMC neurons, an effect that hinged on functional mTORC1 in these neurons. Finally, scavenging ROS prevented the hypophagic action of leptin, which in turn required mTORC1 to increase oxidant levels in POMC neurons and to inhibit food intake. CONCLUSIONS: Our results demonstrate that ROS and leptin require mTORC1 pathway activity in POMC neurons to increase oxidant levels in POMC neurons and consequently decrease food intake.

The pathophysiology of body weight gain that is observed in patients suffering from myeloproliferative neoplasms treated with inhibitors of the janus kinase (Jak) 1 and 2 pathway remains unknown. Here we hypothesized that this class of drugs interferes with the metabolic actions of leptin, as this hormone requires functional Jak2 signaling. To test this, C57BL/6J chow-fed mice received either chronic intraperitoneal (ip) or repeated intracerebroventricular (icv) administration of the selective Jak2 inhibitor NVP-BSK805, which was proven efficacious in treating polycythemia in rodents. Changes in food intake, body weight and body composition were recorded. Icv NVP-BSK805 was combined with ip leptin to evaluate ability to interfere with the action of this hormone on food intake and on induction of hypothalamic phosphorylation of signal transducer and activator of transcription 3 (STAT3). We found that chronic peripheral administration of NVP-BSK805 did not alter food intake, but increased fat mass and feed efficiency. The increase in fat mass was more pronounced during repeated icv administration of the compound, suggesting that metabolic effects were related to molecular interference in brain structures regulating energy balance. Accordingly, acute icv administration of NVP-BSK805 prevented the ability of leptin to decrease food intake and body weight by impeding STAT3 phosphorylation within the hypothalamus. Consequently, acute icv administration of NVP-BSK805 at higher dose induced hyperphagia and body weight gain. Our results provide evidence for a specific anabolic effect exerted by antineoplastic drugs targeting the Jak2 pathway, which is due to interference with the actions of leptin. Consequently, assessment of metabolic variables related to increased fat mass gain should be performed in patients treated with Jak2 inhibitors.

01/01/2016 | dis model mech   IF 4.7
The cannabinoid CB1 receptor and mTORC1 signalling pathways interact to modulate glucose homeostasis in mice.
Bermudez-Silva FJ, Romero-Zerbo SY, Haissaguerre M, Ruz-Maldonado I, Lhamyani S, El Bekay R, Tabarin A, Marsicano G, Cota D

The endocannabinoid system (ECS) is an intercellular signalling mechanism that is present in the islets of Langerhans and plays a role in the modulation of insulin secretion and expansion of the beta-cell mass. The downstream signalling pathways mediating these effects are poorly understood. Mammalian target of rapamycin complex 1 (mTORC1) signalling is a key intracellular pathway involved in energy homeostasis and is known to importantly affect the physiology of pancreatic islets. We investigated the possible relationship between cannabinoid type 1 (CB1) receptor signalling and the mTORC1 pathway in the endocrine pancreas of mice by using pharmacological analysis as well as mice genetically lacking the CB1 receptor or the downstream target of mTORC1, the kinase p70S6K1. In vitro static secretion experiments on islets, western blotting, and in vivo glucose and insulin tolerance tests were performed. The CB1 receptor antagonist rimonabant decreased glucose-stimulated insulin secretion (GSIS) at 0.1 microM while increasing phosphorylation of p70S6K1 and ribosomal protein S6 (rpS6) within the islets. Specific pharmacological blockade of mTORC1 by 3 nM rapamycin, as well as genetic deletion of p70S6K1, impaired the CB1-antagonist-mediated decrease in GSIS. In vivo experiments showed that 3 mg/kg body weight rimonabant decreased insulin levels and induced glucose intolerance in lean mice without altering peripheral insulin sensitivity; this effect was prevented by peripheral administration of low doses of rapamycin (0.1 mg/kg body weight), which increased insulin sensitivity. These findings suggest a functional interaction between the ECS and the mTORC1 pathway within the endocrine pancreas and at the whole-organism level, which could have implications for the development of new therapeutic approaches for pancreatic beta-cell diseases.

11/2014 | J Clin Endocrinol Metab   IF 5.5
Per-operative hemodynamic instability in normotensive patients with incidentally discovered pheochromocytomas.
Lafont M, Haissaguerre M, Tabarin A


10/2014 | Ann Endocrinol (Paris)   IF 0.9
[New insights in adrenal Cushing syndrome].
Haissaguerre M, Tabarin A

The development of molecular biology tools has allowed major advances in the genetic determinism and the pathophysiology of pheochromocytomas and Conn's adenomas. However, the molecular pathophysiology of ACTH-independent Cushing's Syndrome was mostly unknown until recently. In 2014, major new insights concerning the physiopathology of ACTH-independent macronodular adrenal hyperplasias (AIMAH) and the cortisol-secreting adenomas have been published. Elsewhere, the cardiovascular consequences of the subclinical hypercortisolism due to adrenal incidentalomas, was described only in some cross-sectional studies. The natural history of these lesions has been documented in two large follow-up studies. These new data presented during the Endocrine Congress are summarized herein.

15/09/2014 | Int J Obes (Lond)   IF 5.5
The corticotrophin-releasing factor/urocortin system regulates white fat browning in mice through paracrine mechanisms.
Lu B, Diz-Chaves Y, Markovic D, Contarino A, Penicaud L, Fanelli F, Clark S, Lehnert H, Cota D, Grammatopoulos DK, Tabarin A

Objectives:The corticotrophin-releasing factor (CRF)/urocortin system is expressed in the adipose tissue of mammals, but its functional role in this tissue remains unknown.Methods:Pharmacological manipulation of the activity of CRF receptors, CRF1 and CRF2, was performed in 3T3L1 white pre-adipocytes and T37i brown pre-adipocytes during in vitro differentiation. The expression of genes of the CRF/urocortin system and of markers of white and brown adipocytes was evaluated along with mitochondrial biogenesis and cellular oxygen consumption. Metabolic evaluation of corticosterone-deficient or supplemented Crhr1-null (Crhr1-/-) mice and their wild-type controls was performed along with gene expression analysis carried out in white (WAT) and brown (BAT) adipose tissues.Results:Peptides of the CRF/urocortin system and their cognate receptors were expressed in both pre-adipocyte cell lines. In vitro pharmacological studies showed an inhibition of the expression of the CRF2 pathway by the constitutive activity of the CRF1 pathway. Pharmacological activation of CRF2 and, to a lesser extent, inhibition of CRF1 signaling induced molecular and functional changes indicating transdifferentiation of white pre-adipocytes and differentiation of brown pre-adipocytes. Crhr1-/- mice showed increased expression of CRF2 and its agonist Urocortin 2 in adipocytes that was associated to brown conversion of WAT and activation of BAT. Crhr1-/- mice were resistant to diet-induced obesity and glucose intolerance. Restoring physiological circulating corticosterone levels abrogated molecular changes in adipocytes and the favorable phenotype of Crhr1-/- mice.Conclusions:Our findings suggest the importance of the CRF2 pathway in the control of adipocyte plasticity. Increased CRF2 activity in adipocytes induces browning of WAT, differentiation of BAT and is associated with a favorable metabolic phenotype in mice lacking CRF1. Circulating corticosterone represses CRF2 activity in adipocytes and may thus regulate adipocyte physiology through the modulation of the local CRF/urocortin system. Targeting CRF receptor signaling specifically in the adipose tissue may represent a novel approach to tackle obesity.International Journal of Obesity advance online publication, 14 October 2014; doi:10.1038/ijo.2014.164.

24/07/2014 | J Clin Endocrinol Metab   IF 5.5
Novel somatic mutations in the catalytic subunit of the protein kinase A as a cause of adrenal Cushing's syndrome: a European multicentric study.
Di Dalmazi G, Kisker C, Calebiro D, Mannelli M, Canu L, Arnaldi G, Quinkler M, Rayes N, Tabarin A, Laure Jullie M, Mantero F, Rubin B, Waldmann J, Bartsch DK, Pasquali R, Lohse M, Allolio B, Fassnacht M, Beuschlein F, Reincke M

Context. Somatic mutations in PRKACA gene, encoding the catalytic subunit of protein kinase A (PKA), have been recently found in a high proportion of sporadic adenomas associated with Cushing's syndrome (CS). The aim was to analyze the PRKACA mutation in a large cohort of patients with adrenocortical masses. Methods. Samples from nine European centers were included (Germany, n=4; Italy, n=4; France, n=1). Samples were drawn from 149 patients with non-secreting adenomas (n=32 + 2 peritumoral), subclinical hypercortisolism (n=36), CS (n=64 + 2 peritumoral), androgen-producing tumors (n=4), adrenocortical carcinomas (n=5 + 2 peritumoral), and primary bilateral macronodular adrenal hyperplasias (n=8). Blood samples were available from patients with non-secreting adenomas (n=15), subclinical hypercortisolism (n=10), and CS (n=35). Clinical and hormonal data were collected. DNA amplification by PCR of exons 6 and 7 of the PRKACA gene and direct sequencing were performed. Results. PRKACA heterozygous mutations were found in 22/64 samples of CS patients (34%). No mutations were found in peritumoral tissue and blood samples or in other tumors examined. The c.617A>C (p.Leu206Arg) occurred in 18/22 patients. Furthermore, two novel mutations were identified: c.600 601insGTG/p.Cys200 Gly201insVal in three patients and c.639C>G+c.638 640insATTATCCTGAGG/p.Ser213Arg+p.Leu212 Lys214insIle-Ile-Leu-Arg) in one. All the mutations involved a region implicated in interaction between PKA regulatory and catalytic subunits. Patients with somatic PRKACA mutations showed higher levels of cortisol after dexamethasone test and a smaller adenoma size, compared to non-mutated subjects. Conclusions. These data confirm and extend previous observations that somatic PRKACA mutations are specific for adrenocortical adenomas causing CS.

26/06/2014 | Clin Endocrinol (Oxf)   IF 3.3
Accuracy of repeated measurements of late-night salivary cortisol to screen for early-stage recurrence of Cushing's disease following pituitary surgery.
Danet-Lamasou M, Asselineau J, Perez P, Vivot A, Nunes ML, Loiseau H, San-Galli F, Cherifi-Gatta B, Corcuff JB, Tabarin A

OBJECTIVE: The performance of late-night salivary cortisol (LNSC) to accurately screen for post-operative recurrence of Cushing's disease (CD) at an early-stage is unknown. The aim of this study was to compare the accuracy of multiple sampling strategies to suggest the optimal number of LNSC samples needed for diagnosing post-surgical recurrences of CD at an early stage. DESIGN: Retrospective analysis in a single center. PATIENTS AND MEASUREMENTS: 36 patients in surgical remission of CD had successive measurements of LNSC, defined as 'sequences', using a locally modified RIA assay as part of long-term follow-up (69.2 +/- 10.6 mo). Patients underwent an extensive biochemical evaluation within 3 months before or after a sequence of saliva sampling and were classified as being in remission or in early-stage recurrence. The accuracy of three diagnostic strategies combining two, three or four LNSC results from a sequence was estimated using areas under the ROC curves (AUC), sensitivity, specificity and predictive values. RESULTS: 44 sequences of LNSC measurements were available. 52% of sequences were performed during early-stage recurrence. The intra-sequence variability of LNSC was higher during recurrence than during remission (medians of SDs: 2.1 vs. 0.5 nmol/L; p<0.0001). AUCs from ROC curves ranged from 0.93 to 0.96 depending on the strategy. For 90% sensitivities, the best specificities (92.9 and 90.9%) were achieved by strategies taking into account three or four measurements summarized either by their mean or their maximum value. CONCLUSIONS: Increase in LNSC concentration is an early abnormality during post-surgical recurrence of CD. However, due to a major within-patient variability of LNSC from one day to another, a screening strategy using three or four samples collected on successive days may be recommended to detect early-stage recurrence of CD with a high accuracy. This article is protected by copyright. All rights reserved.

06/2014 | Nat Genet   IF 28
Integrated genomic characterization of adrenocortical carcinoma.
Assie G, Letouze E, Fassnacht M, Jouinot A, Luscap W, Barreau O, Omeiri H, Rodriguez S, Perlemoine K, Rene-Corail F, Elarouci N, Sbiera S, Kroiss M, Allolio B, Waldmann J, Quinkler M, Mannelli M, Mantero F, Papathomas T, De Krijger R, Tabarin A, Kerlan V, Baudin E, Tissier F, Dousset B, Groussin L, Amar L, Clauser E, Bertagna X, Ragazzon B, Beuschlein F, Libe R, de Reynies A, Bertherat J

Adrenocortical carcinomas (ACCs) are aggressive cancers originating in the cortex of the adrenal gland. Despite overall poor prognosis, ACC outcome is heterogeneous. We performed exome sequencing and SNP array analysis of 45 ACCs and identified recurrent alterations in known driver genes (CTNNB1, TP53, CDKN2A, RB1 and MEN1) and in genes not previously reported in ACC (ZNRF3, DAXX, TERT and MED12), which we validated in an independent cohort of 77 ACCs. ZNRF3, encoding a cell surface E3 ubiquitin ligase, was the most frequently altered gene (21%) and is a potential new tumor suppressor gene related to the beta-catenin pathway. Our integrated genomic analyses further identified two distinct molecular subgroups with opposite outcome. The C1A group of ACCs with poor outcome displayed numerous mutations and DNA methylation alterations, whereas the C1B group of ACCs with good prognosis displayed specific deregulation of two microRNA clusters. Thus, aggressive and indolent ACCs correspond to two distinct molecular entities driven by different oncogenic alterations.

06/2014 | Presse Med   IF 1.1
[Malignant insulinoma: recommendations for workup and treatment].
Baudin E, Caron P, Lombard-Bohas C, Tabarin A, Mitry E, Reznick Y, Taieb D, Pattou F, Goudet P, Vezzosi D, Scoazec JY, Cadiot G, Borson-Chazot F, Do Cao C

Insulinoma are malignant in 4 to 14 % of cases. Their rarity and the sparse data available in the literature have limited publication of specific guidelines for their management. The following review aim to provide up-to-date recommendations on initial evaluation including pathologic grading, measures to control hypoglycemia, antitumor strategies and long term follow-up. Will be discussed in detail respective indications of surgery, diazoxide, somatostatin analogs, everolimus, sunitinib, liver directed treatments including arterial embolization, chemotherapy and radiometabolic therapy. A Medline search using terms 'insulinoma', 'neuroendocrine pancreatic tumors', 'islet cell carcinoma', 'malignant insulinoma' was performed limiting the selection to English language articles and adult age cases, along with cross referencing.