Evidence against a direct role of klotho in insulin resistance

The klotho gene may be involved in the aging process. Klotho is a coactivator of FGF23, a regulator of phosphate and vitamin D metabolism. It has also been reported to be downregulated in insulin resistance syndromes and paradoxically to directly inhibit IGF-1 and insulin signaling. Our aim was to study klotho's regulation and effects on insulin and IGF-1 signaling to unravel this paradox. We studied klotho tissue distribution and expression by quantitative real-time polymerase chain reaction and Western blotting in obese Zucker rats and high-fat fed Wistar rats, two models of insulin resistance. Klotho was expressed in kidneys but at much lower levels (<1.5%) in liver, muscle, brain, and adipose tissue. There were no significant differences between insulin resistant and control animals. We next produced human recombinant soluble klotho protein (KLEC) and studied its effects on insulin and IGF-1 signaling in cultured cells. In HEK293 cells, FGF23 signaling (judged by FRS2-α and ERK1/2 phosphorylation) was activated by conditioned media from KLEC-producing cells (CM-KLEC); however, IGF-1 signaling was unaffected. CM-KLEC did not inhibit IGF-1 and insulin signaling in L6 and Hep G2 cells, as judged by Akt and ERK1/2 phosphorylation. We conclude that decreased klotho expression is not a general feature of rodent models of insulin resistance. Further, the soluble klotho protein does not inhibit IGF-1 and/or insulin signaling in HEK293, L6, and HepG2 cells, arguing against a direct role of klotho in insulin signaling. However, the hypothesis that klotho indirectly regulates insulin sensitivity via FGF23 activation remains to be investigate

Incorporation of Imidazolium Ionic Liquids in GC Stationary Phases via the Sol–Gel Process

International audienceRoom-temperature ionic liquids (RTILs) have proven to be efficient polar or highly polar stationary phases for GC. Nevertheless, the thermal stability of monocationic RTILs limits their use in high-temperature GC. To improve the thermal stability, an RTIL based on a 1-methylimidazolium derivative was anchored in a three-dimensional network using the sol-gel process. Three different strategies were compared: using the derivative pure, in combination with a polymer or copolymerised with diethoxydimethylsilane. This last method allowed for the preparation of hybrid stationary phases with satisfactory efficiency (3500 plates per meter determined by the injection of n-tetradecane at 80 °C, k = 8.19) and very good thermal stability up to 340 °C using the NTf2 counter ion. The stationary phases demonstrated a good ability to separate positional isomers and polycyclic aromatic hydrocarbons. Polarity and molecular interactions with analytes were characterized by calculating the Rohrschneider-McReynolds constants and Abraham system constants. A classification of the polarity of the new stationary phases relative to 44 stationary phases, including commercial and non-commercial ones, was performed based on the RTILs using principal component analysis. Finally, the maximal operating temperature of these new stationary phases was compared with those of the most thermally stable conventional or RTIL-based stationary phases, demonstrating that th

Physical Ionic Liquid/Polysiloxane Mixtures for Tuning the Polarity and the Selectivity of the Polysiloxane Stationary Phase for GC Analysis

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Protein kinase C-delta mediates von Willebrand factor secretion from endothelial cells in response to vascular endothelial growth factor (VEGF) but not histamine

BACKGROUND: Vascular endothelial growth factor (VEGF) and histamine induce von Willebrand factor (VWF) release from vascular endothelial cells. Protein kinase C (PKC) is involved in the control of exocytosis in many secretory cell types. OBJECTIVES: We investigated the role of PKC and the interactions between PKC and Ca2+ signaling in both VEGF-induced and histamine-induced VWF secretion from human umbilical vein endothelial cells (HUVECs). RESULTS: Several PKC inhibitors (staurosporine, Ro31-8220, myristoylated PKC peptide inhibitor and Go6983) block VEGF-induced but not histamine-induced VWF secretion. PKC-alpha and novel PKCs (PKC-delta, PKC-epsilon, and PKC-eta), but not PKC-beta, are expressed in HUVECs. Both VEGF and histamine activate PKC-delta. However, gene inactivation experiments using small interfering RNA indicate that PKC-delta (but not PKC-alpha) is involved in the regulation of VEGF-induced but not histamine-induced secretion. Both VEGF and histamine induce a rise in cytosolic free Ca2+ ([Ca2+]c), but the response to VEGF is weaker and even absent in a significant subset of cells. Furthermore, VEGF-induced secretion is largely preserved when the rise in [Ca2+]c is prevented by BAPTA-AM. CONCLUSIONS: Our study identifies striking agonist specificities in signal-secretion coupling. Histamine-induced secretion is dependent on [Ca2+]c but not PKC, whereas VEGF-induced secretion is largely dependent on PKC-delta and significantly less on [Ca2+]c. Our data firmly establish the key role of PKC-delta in VEGF-induced VWF release, but suggest that a third, VEGF-specific, signaling intermediate is required as a PKC-delta coactivator

Improved adhesion of poly(3,4-ethylenedioxythiophene) (PEDOT) thin film to solid substrates using electrografted promoters and application to efficient nanoplasmonic devices

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Vingt ans de transitions agricoles et rurales à l'Est. Quels enseignements? Vingt ans après la rupture systémique de 1990 et six ans après le premier élargissement de l'Union européenne à l'Est, la thématique de ce numéro double se veut être un bilan des différentes dispositions structurelles et fonctionnelles des agricultures et des politiques publiques qui se sont mises en place dans les pays d’Europe centrale et orientale. S'appuyant sur l'observation de terrains très divers, douze chercheurs se sont penchés sur les nouveaux enjeux économiques et sociaux dus aux transitions postcommunistes. Comment se sont manifestés les obstacles face à la nouvelle concurrence des marchés ? Comment s’est recomposée la ruralité ? Quels enseignements tirés des bouleversements intervenus dans tous les secteurs de la production agricole ? Les analyses par pays, sur une région ou sur un village viennent opportunément compléter les enseignements synthétiques présentés, montrant ainsi le profond renouvellement des cadres théoriques et méthodologiques. Le rôle de la politique agricole commune reste présent à chacun des niveaux. Note de lecture L’Allemagne du XXIe siècle, une nouvelle nation

Evidence against a direct role of klotho in insulin resistance.

The klotho gene may be involved in the aging process. Klotho is a coactivator of FGF23, a regulator of phosphate and vitamin D metabolism. It has also been reported to be downregulated in insulin resistance syndromes and paradoxically to directly inhibit IGF-1 and insulin signaling. Our aim was to study klotho's regulation and effects on insulin and IGF-1 signaling to unravel this paradox. We studied klotho tissue distribution and expression by quantitative real-time polymerase chain reaction and Western blotting in obese Zucker rats and high-fat fed Wistar rats, two models of insulin resistance. Klotho was expressed in kidneys but at much lower levels (&lt;1.5%) in liver, muscle, brain, and adipose tissue. There were no significant differences between insulin resistant and control animals. We next produced human recombinant soluble klotho protein (KLEC) and studied its effects on insulin and IGF-1 signaling in cultured cells. In HEK293 cells, FGF23 signaling (judged by FRS2-alpha and ERK1/2 phosphorylation) was activated by conditioned media from KLEC-producing cells (CM-KLEC); however, IGF-1 signaling was unaffected. CM-KLEC did not inhibit IGF-1 and insulin signaling in L6 and Hep G2 cells, as judged by Akt and ERK1/2 phosphorylation. We conclude that decreased klotho expression is not a general feature of rodent models of insulin resistance. Further, the soluble klotho protein does not inhibit IGF-1 and/or insulin signaling in HEK293, L6, and HepG2 cells, arguing against a direct role of klotho in insulin signaling. However, the hypothesis that klotho indirectly regulates insulin sensitivity via FGF23 activation remains to be investigated