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I K Lund, J A Hansen, H S Andersen, N P H Møller and N Billestrup

hypothalamus, through which it exerts its key regulatory role by controlling the overall energy homeostasis, i.e. induction of reduced food intake and promotion of weight loss ( Ahima & Flier 2000 , Korner & Aronne 2003 ). Defective leptin signalling due to

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N Martínez-Micaelo, N González-Abuín, A Ardévol, M Pinent, E Petretto, J Behmoaras and M Blay

system ( Myers et al . 2008 ). In addition to its key role in the maintenance of energy homeostasis, leptin modulates both humoral and cell-mediated immunity ( La Cava & Matarese 2004 ). Leptin signalling is dependent on the presence of the long isoform

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NM Morton, V Emilsson, P de Groot, AL Pallett and MA Cawthorne

Leptin is a cytokine secreted from adipose tissue at a rate commensurate with the size of the body's fat stores. In addition to its anorectic and thermogenic central actions, leptin is known to act on peripheral tissues, including the pancreatic beta-cell where it inhibits insulin secretion and reduces insulin transcript levels. However, the role of leptin signalling through its full-length receptor, OB-Rb, in the beta-cell remains unclear. In the present study, we show that leptin activates a signal transducer and activator of transcription (STAT)3 signalling mechanism in pancreatic islets and in a rat model of the pancreatic beta-cell, RINm5F. Leptin induced DNA binding to a STAT consensus oligonucleotide and resulted in transcriptional activation from STAT reporter constructs in a manner consistent with STAT3 activation. Western blot analysis confirmed activation of STAT3 in RINm5F and isolated rat islets. Conditions that mimic increased metabolic activity resulted in attenuation of leptin-mediated STAT DNA binding but had no significant effect on STAT3 tyrosine phosphorylation in RINm5F cells. In addition, leptin activated the mitogen activated protein (MAP) kinase pathway in RINm5F cells. The present study provides a framework for OB-Rb signalling mechanisms in the programming of the beta-cell by leptin and suggests that increased metabolic activity may modulate this function.

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Martina Holubová, Lucie Hrubá, Barbora Neprašová, Zuzana Majerčíková, Zdeňka Lacinová, Jaroslav Kuneš, Lenka Maletínská and Blanka Železná

2013 ). It connected leptin signaling to the anorexigenic effect of PrRP, but the mechanism has not been explained yet. After termination of long-term administration of an anti-obesity drug, it is necessary to sustain the decrease in body weight in

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CP Briscoe, S Hanif, Arch JR and M Tadayyon

The effect of treatment with a 0.03% fatty acid (FA) cocktail on leptin-receptor-mediated STAT (signal transducers and activators of transcription) activation in the rat insulinoma cell line BRIN-BD11 was investigated. Leptin (10 nM) stimulated the tyrosine phosphorylation of STAT3 and STAT5b. Acute treatment with FAs prevented leptin-stimulated STAT3 tyrosine phosphorylation and significantly raised basal STAT5 phosphorylation. A chronic treatment (5 days) of BRIN-BD11 cells with FAs similarly attenuated leptin-stimulated STAT tyrosine phosphorylation. Chronic FA treatment also attenuated prolactin-stimulated STAT5b tyrosine phosphorylation but not interleukin-6-stimulated STAT3 tyrosine phosphorylation, suggesting that the effect is receptor/ligand specific. TaqMan analysis of gene expression following chronic FA treatment showed neither a decrease in the amount of leptin receptor (Ob-R) mRNA, nor an increase in the negative regulators of STAT signalling, SOCS3 (suppressors of cytokine signalling) or cytokine inducible sequence (CIS). These data demonstrate that FAs modulate leptin and prolactin signalling in beta-cells, implying that high levels of circulating FAs present in obese individuals affect the action of selective cytokines in beta-cell function.

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Laura Marroquí, Alejandro Gonzalez, Patricia Ñeco, Ernesto Caballero-Garrido, Elaine Vieira, Cristina Ripoll, Angel Nadal and Ivan Quesada

different direct effects on the β-cell. Additionally, it has been proposed that alterations in leptin signaling in the β-cell might be involved in diabetes in obese individuals ( Seufert 2004 ). In the next sections we will focus on the different leptin

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N T Lam, S D Covey, J T Lewis, S Oosman, T Webber, E C Hsu, A T Cheung and T J Kieffer

prevail causes insulin resistance and hyperglycemia which, if left untreated, may lead to diabetes mellitus. Leptin signaling is similarly regulated; signaling begins with phosphorylation and activation of janus kinase 2 (JAK2) ( Ghilardi & Skoda 1997

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J Bian, X M Bai, Y L Zhao, L Zhang and Z J Liu

location, the final success rate of the animal model was 54%. Leptin signaling studies To examine the role of Lrb knockdown on leptin signaling, the rats treated with Lrb -shRNA or scrambled shRNA (described earlier) were placed on a CD or a HFD for 8

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Zhi Zhang, Fang Wang, Bing-jian Wang, Guang Chu, Qunan Cao, Bao-Gui Sun and Qiu-Yan Dai

study, which indicated that SOCS3 negatively regulates leptin signalling ( Handy et al . 2010 ). Furthermore, collectively, these findings provide a plausible molecular explanation for why adiponectin exerted no influence on the expression of MMP2

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Maggie C Evans and Greg M Anderson

GABAergic neurons in the control of HPG axis function, our lab generated mice exhibiting GABA-specific deletion of LepR ( Zuure et al . 2013 ) and InsR (Evans et al . 2014 b ) and demonstrated that leptin signaling, but not insulin signaling, via GABAergic