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Novel regulatory mechanisms for generation of the soluble leptin receptor: implications for leptin action.

ABSTRACT: The adipokine leptin realizes signal transduction via four different membrane-anchored leptin receptor (Ob-R) isoforms in humans. However, the amount of functionally active Ob-R is affected by constitutive shedding of the extracellular domain via a so far unknown mechanism. The product of the cleavage process the so-called soluble leptin receptor (sOb-R) is the main binding protein for leptin in human blood and modulates its bioavailability. sOb-R levels are differentially regulated in metabolic disorders like type 1 diabetes mellitus or obesity and can, therefore, enhance or reduce leptin sensitivity.To describe mechanisms of Ob-R cleavage and to investigate the functional significance of differential sOb-R levels we established a model of HEK293 cells transiently transfected with different human Ob-R isoforms. Using siRNA knockdown experiments we identified ADAM10 (A Disintegrin And Metalloproteinase 10) as a major protease for constitutive and activated Ob-R cleavage. Additionally, the induction of lipotoxicity and apoptosis led to enhanced shedding shown by increased levels of the soluble leptin receptor (sOb-R) in cell supernatants. Conversely, high leptin concentrations and ER stress reduced sOb-R levels. Decreased amounts of sOb-R due to ER stress were accompanied by impaired leptin signaling and reduced leptin binding.Lipotoxicity and apoptosis increased Ob-R cleavage via ADAM10-dependent mechanisms. In contrast high leptin levels and ER stress led to reduced sOb-R levels. While increased sOb-R concentrations seem to directly block leptin action, reduced amounts of sOb-R may reflect decreased membrane expression of Ob-R. These findings could explain changes of leptin sensitivity which are associated with variations of serum sOb-R levels in metabolic diseases.

SUBMITTER: Schaab M

PROVIDER: S-EPMC3335825 | biostudies-literature | 2012

REPOSITORIES: biostudies-literature

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Novel regulatory mechanisms for generation of the soluble leptin receptor: implications for leptin action.

Schaab Michael M Kausch Henriette H Klammt Juergen J Nowicki Marcin M Anderegg Ulf U Gebhardt Rolf R Rose-John Stefan S Scheller Juergen J Thiery Joachim J Kratzsch Juergen J

PloS one 20120424 4

<h4>Background</h4>The adipokine leptin realizes signal transduction via four different membrane-anchored leptin receptor (Ob-R) isoforms in humans. However, the amount of functionally active Ob-R is affected by constitutive shedding of the extracellular domain via a so far unknown mechanism. The product of the cleavage process the so-called soluble leptin receptor (sOb-R) is the main binding protein for leptin in human blood and modulates its bioavailability. sOb-R levels are differentially reg ...[more]

PMID: 22545089

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Project description:Background: Lower-limb peripheral artery disease (PAD) is one of the major complications of diabetes mellitus. PAD is associated with poor limb and cardiovascular prognoses, along with a dramatic decrease in life expectancy. Despite major medical advances in the treatment of diabetes, a substantial therapeutic gap remains in the PAD population. Praliciguat is an orally available soluble guanylate cyclase (sGC) stimulator that has been reported both pre-clinically and in early-stage clinical trials to have favorable effects in metabolic and hemodynamic outcomes, suggesting that it may have a potential beneficial effect in PAD. Objective: We evaluated the effect of praliciguat on hind limb ischemia (HLI) recovery in a mouse model of type 2 diabetes. Methods: HLI was induced in leptin receptor-deficient (Leprdb/db) mice by ligation and excision of the left femoral artery. Praliciguat (10 mg/kg/day) was administered in the diet starting 3 days before surgery. Results: 28 days after surgery, ischemic foot perfusion and function parameters were better in praliciguat-treated mice than in vehicle controls. Improved ischemic foot perfusion was not associated with either improved traditional cardiovascular risk factors (i.e., weight, glycemia) or increased angiogenesis. However, treatment with praliciguat significantly increased arteriole diameter, decreased intercellular adhesion molecule 1 (ICAM1) expression, and prevented the accumulation of oxidative pro-angiogenic and pro-inflammatory muscle fibers. While investigating the mechanism underlying the beneficial effects of praliciguat therapy, we found that praliciguat significantly downregulated Myh2 and Cxcl12 mRNA expression in cultured myoblasts and that conditioned medium form praliciguat-treated myoblast decreased ICAM-1 mRNA expression in endothelial cells. These results suggest that praliciguat therapy may decrease ICAM-1 expression in endothelial cells by downregulating Cxcl12 in myocytes. Conclusion: Our results demonstrated that praliciguat promotes blood flow recovery in the ischemic muscle of mice with type 2 diabetes, at least in part by increasing arteriole diameter and by downregulating ICAM-1 expression.

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Novel regulatory mechanisms for generation of the soluble leptin receptor: implications for leptin action.

Publications

Novel regulatory mechanisms for generation of the soluble leptin receptor: implications for leptin action.

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