Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.10.1 (ERK)
 95,504 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Leptin is presumed to be related to body mass index (BMI) and body fat stores and is involved together with neuropeptid Y (NPY) in the regulation of appetite. As pregnancy is accompanied both by changes of BMI and appetite, performance of studies presented in this paper were fully justified. In 43 healthy pregnant women and in 18 pregnant women with mild or moderate EPH-gestosis, concentrations of leptin and NPY were estimated in maternal venous blood, umbilical cord blood and in amniotic fluid. The control group consisted of 26 healthy nonpregnant women. Healthy nonpregnant women showed a BMI of 23.08+/-0.65 kg/m2 which was significantly lower than in healthy pregnant women (26.9+/-0.4 kg/m2, p < 0.001) and in women with EPH-gestosis (29.7+/-0.9, p < 0.0001). Also in healthy pregnant women the BMI was significantly lower than in EPH-gestosis subjects (p < 0.001). In healthy nonpregnant women plasma leptin levels were significantly lower than in healthy pregnant and EPH-gestosis women (10.9+/-1.68 vs 14.99+/-1.28 vs 21.89+/-2.58 ng/ml, respectively). In umbilical cord blood plasma leptin levels were significantly lower than in maternal blood only in healthy pregnant women (7.37+/-0.69 vs 14.99+/-1.28 ng/ml) but not in EPH-gestosis subjects (18.06+/-3.38 vs 21.89+/-2.58 ng/ml). Leptin levels in amniotic fluid were significantly lower than in umbilical cord blood both in healthy pregnant women (2.25+/-0.20 vs 7.37+/-0.69 ng/ml) and EPH-gestosis women (6.58+/-2.62 vs 18.06+/-3.38 ng/ml). In EPH-gestosis women leptin levels were significantly higher than in healthy pregnant women in maternal blood (21.89+/-2.58 vs 14.99+/-1.28 ng/ml), umbilical cord blood (18.06+/-3.38 vs 7.37+/-0.69 ng/ml) and amniotic fluid (6.58+/-2.62 vs 2.25+/-0.2 ng/ml). In both examined pregnant groups plasma NPY levels were nonsignificantly lower in healthy pregnant and EPH-gestosis women (42.28+/-4.09 and 43.68+/-8.45 pg/ml, respectively) than in nonpregnant women 50.65+/-6.13 pg/ml). In normal pregnancy a significantly higher NPY level was found in umbilical cord blood as compared with respective values in EPH-gestosis women (116.28+/-17.0 vs 49.65+/-7.01 pg/ml). Finally in both examined groups of pregnant women the amniotic fluid NPY level was of similar magnitude (13.85+/-1.52 and 13.89+/-2.46 pg/ml in healthy pregnant and EPH-gestosis women respectively). No significant correlation was found between fetal birth weight and cord-serum leptin and NPY levels respectively.
 ...
PMID:Concentrations of leptin and neuropeptide Y in maternal plasma, umbilical cord blood and in amniotic fluid in pregnant women with EPH-gestosis. 983 71

We have previously shown that murine recombinant leptin directly stimulates catecholamine synthesis through the long form of the leptin receptor (Ob-Rb) expressed in cultured porcine chromaffin cells. Additionally, we found that leptin activates IP3 production after PLC activation. It is well established that activation of PLC elicits IP3 production as well as an increase in diacylglycerol, a compound that stimulates PKC. Therefore, we investigated the involvement of PKC in leptin-induced catecholamine synthesis. Leptin was found to induce significant increases in PKC activity in a dose-dependent manner (1, 10, and 100 nM); chelation of extracellular Ca(2+) by EDTA abolished this PKC stimulatory activity. We also confirmed by Western blot analysis that leptin (at 100 nM) induced significant increases in Ca(2+)-dependent PKC alpha, -beta(I), and -gamma expression. The activity of the rate-limiting enzyme tyrosine hydroxylase (TH) in the biosynthesis of catecholamine is regulated at the transcriptional and posttranscriptional levels. TH enzyme activity and TH mRNA levels induced by 100 nM leptin were significantly inhibited by the PKC inhibitor Ro 32-0432 as well as by EDTA. In addition, increases in TH protein and intracellular catecholamine content stimulated by leptin were completely inhibited by Ro 32-0432. Leptin markedly activated ERKs and, to a lesser extent, JNK; these stimulatory effects on ERKs and JNK were completely inhibited by Ro 32-0432 as well as EDTA. In contrast, leptin did not activate P38 MAPK. Similar to leptin, PMA activated ERK and JNK. Nicardipine and omega-conotoxin GVIA, each at 1 microM, were effective at inhibiting leptin-induced TH enzyme activity, TH mRNA accumulation, PKC activity, and ERK activity. Leptin increased activating protein-1 DNA-binding activity, and this was diminished by Ro 32-0432 as well as EDTA, similar to the reduction of TH mRNA levels. In addition, using supershift analysis, we documented the involvement of c-Fos and, to a lesser extent, c-Jun in leptin-induced activating protein-1 activity. These results indicate that leptin stimulates Ca(2+)-dependent PKC isoform-dependent catecholamine synthesis in porcine chromaffin cells. Previously, we had shown that leptin stimulated cAMP. The present study also showed that H89 (a PKA inhibitor) moderately, but significantly, inhibited leptin-induced ERK and TH mRNA. Consistent with this finding, leptin is shown here to activate novel PKC epsilon, which is assumed to stimulate Raf, upstream of ERKs, via cAMP, supporting the suggestion that Ca(2+)-independent novel PKC may also play some physiological role in regulating catecholamine synthesis.
 ...
PMID:Leptin stimulates catecholamine synthesis in a PKC-dependent manner in cultured porcine adrenal medullary chromaffin cells. 1160 54

An ovine-specific RIA, shown to be reliable for bovine leptin determination, was used to study the effects of breed, body fatness, feeding level, and meal intake on plasma leptin level in adult cattle. Eighteen fat Charolais, fat Holstein, and lean Holstein adult cows were either well-fed (130% of maintenance energy requirements [MER]) or underfed (60% of MER) for 3 wk. The breed tended to have a small effect on plasma leptin level, which was decreased by 70% (P < 0.05) in lean compared to fat Holstein cows. A strong curvilinear relationship was found between mean adipocyte volume and plasma leptin concentrations in well-fed (r = +0.95) and underfed (r = +0.91) cows. Underfeeding caused a significant decrease in plasma leptin levels from 8.0+/-3.1 to 6.1+/-2.3 ng/mL (P < 0.01). Nine adult Holstein cows initially fed at 130% of MER (control) were underfed to 21% of MER for 7 d, and five of them were refed to 237% of MER for 21 d. Plasma leptin measured 1 h before meal distribution was decreased from 5.9+/-0.4 to 3.8+/-0.2 ng/mL (P < 0.01) by underfeeding and increased to reach 8.8+/-1.0 ng/mL (P < 0.01) after refeeding. It was positively related to plasma glucose (r = +0.52, P < 0.01) and negatively related to plasma NEFA (r = -0.67, P < 0.001). Plasma leptin measured 4 h after meal distribution was positively related to feeding level and to plasma 3-OH-butyrate (r = +0.61, P < 0.005) and negatively related to plasma NEFA (r = -0.56, P < 0.01). Differences between pre- and postprandial leptin concentrations showed a decrease after meal intake in control and well-fed cows (-7 and -19%, P < 0.01, respectively) and an increase in underfed cows (+12%, P < 0.01). Leptin response to meal intake was positively related to glucose response (r = +0.66, P < 0.001) and negatively related to 3-OH-butyrate response (r = -0.78, P < 0.001). By using the "multispecies" commercial RIA, leptin concentrations were lower and we observed similar physiological responses, although less related to other hormones or metabolites. These data provide evidence, first, that a specific RIA for ruminant leptin determination is necessary to better understand leptin regulation, and second, that plasma leptin is strongly related to adipose cell size and positively related to feeding level in adult cattle, and that an effect of meal intake could be mediated by glucose and(or) ketone bodies.
 ...
PMID:Plasma leptin concentration in adult cattle: effects of breed, adiposity, feeding level, and meal intake. 1201 21

Migration of endothelial cells (EC) is a key event in angiogenesis that contributes to neovascularization in diabetic vasculopathy. Leptin induces angiogenesis and is elevated in obesity and hyperinsulinemia. The antidiabetic thiazolidinediones (TZD) inhibit leptin gene expression and vascular smooth muscle cell migration through activation of the peroxisome proliferator-activated receptor-gamma (PPARgamma). This study investigates the role of leptin in EC migration, the chemotactic signaling pathways involved, and the effects of the TZD-PPARgamma ligands troglitazone (TRO) and ciglitazone (CIG) on EC migration. We demonstrate that leptin induces EC migration. Because activation of two signaling pathways, the phosphatidylinositol-3 kinase (PI3K)-->Akt-->eNOS and the ERK1/2 MAPK pathway, is known to be involved in cell migration, we used the pharmacological inhibitors wortmannin and PD98059 to determine if chemotactic signaling by leptin involves Akt or ERK1/2, respectively. Both wortmannin and PD98059 significantly inhibited leptin-induced migration. Treatment with the TZD-PPARgamma-ligands TRO and CIG significantly inhibited the chemotactic response toward leptin. Both PPARgamma-ligands inhibited leptin-stimulated Akt and eNOS phosphorylation, but neither attenuated ERK 1/2 activation in response to leptin. The inhibition of Akt-phosphorylation was accompanied by a PPARgamma-ligand-mediated upregulation of PTEN, a phosphatase that functions as a negative regulator of PI3K-->Akt signaling. These experiments provide the first evidence that activation of Akt and ERK 1/2 are crucial events in leptin-mediated signal transduction leading to EC migration. Moreover, inhibition of leptin-directed migration by the PPARgamma-ligands TRO and CIG through inhibition of Akt underscores their potential in the prevention of diabetes-associated complications.
 ...
PMID:Leptin induces endothelial cell migration through Akt, which is inhibited by PPARgamma-ligands. 1241 72

Leptin, the Ob gene product, has emerged recently as a key regulator of bone mass. However, the mechanism mediating leptin effect remains controversial. Because the action of leptin is dependent on its receptors, we analyzed their expression in osteoblast-lineage primary human bone marrow stromal cells (hBMSC). Both the short and long forms of leptin receptors were detected in hBMSC. Leptin significantly decreased the viability of hBMSC. This cytotoxic effect was prevented by Z-Val-Ala-Asp-fluoromethylketone, a pan-caspase inhibitor, implicating that leptin-induced hBMSC death was caspase-dependent. Further investigation demonstrated that leptin activated caspase-3 and caspase-9, but not caspase-8, and increased the cleavage of poly-(ADP-ribose) polymerase and cytochrome c release into cytosol. Leptin activated ERK, but not p38 and JNK, and up-regulated cPLA2 activity; the latter was abolished by pre-treatment of cells with the MEK inhibitor (PD98059 or U0126) or cPLA2 inhibitor (AACOCF3). PD98059, U0126, and AACOCF3 also diminished the leptin-induced cytochrome c release into cytosol, cell death, and caspase-3 activation. These data indicated that leptin induced hBMSC apoptosis via ERK/cPLA2/cytochrome c pathway with activation of caspase-9 and caspase-3, and cleavage of poly(ADP-ribose) polymerase. To our knowledge, this is the first study demonstrating the direct detrimental effect of leptin on bone cells.
 ...
PMID:Leptin induces apoptosis via ERK/cPLA2/cytochrome c pathway in human bone marrow stromal cells. 1266 5

The hypertrophy of vascular smooth muscle cells (VSMCs) is critical in vascular remodeling associated with hypertension, atherosclerosis, and restenosis. Recently, leptin has appeared to play a pivotal role in vascular remodeling. However, the mechanism by which leptin induces hypertrophy in vascular smooth muscle cells is still unknown. We studied the role of leptin as a potential hypertrophic factor in rat VSMCs. In the present study, leptin significantly increased [(3)H]leucine incorporation and the total protein/DNA ratio in VSMCs. The maximal hypertrophic effect was at 100ng/ml of leptin. Leptin induced phosphorylation and activation of p38 mitogen-activated protein (p38 MAP) kinase and of signal transducers and activators of transcription 3 in a concentration- and time-dependent manner. A p38 MAP kinase inhibitor SB203580 significantly inhibited leptin-induced hypertrophy, AG490 (a JAK2 inhibitor) partially inhibited it, and other MAP kinase inhibitors, PD98059 (an ERK inhibitor) and SP600125 (a JNK inhibitor), had no effect. These results indicate that leptin directly stimulates cellular hypertrophy via p38 MAP kinase in rat VSMCs.
 ...
PMID:Leptin induces hypertrophy via p38 mitogen-activated protein kinase in rat vascular smooth muscle cells. 1572 Dec 67

Experimental evidence suggests that leptin operates on the tissues, including skeletal muscle, also by modulating gene expression. Using electrophoretic mobility shift assays, we have shown that physiological doses of leptin promptly increase the binding of C2C12 cell nuclear extracts to peroxisome proliferator-activated receptor (PPAR) response elements in oligonucleotide probes and that all three PPAR isoforms participate in DNA-binding complexes. We pre-treated C2C12 cells with AACOCF3, a specific inhibitor of cytosolic phospholipase A2 (cPLA2), an enzyme that supplies ligands to PPARs, and found that it abrogates leptin-induced PPAR DNA-binding activity. Leptin treatment significantly increased cPLA2 activity, evaluated as the release of [3H]arachidonic acid from pre-labelled C2C12 cells, as well as phosphorylation. Further, using MEK1 inhibitor PD-98059 we showed that leptin activates cPLA2 through ERK induction. These results support a direct effect of leptin on skeletal muscle cells, and suggest that the hormone may modulate muscle transcription also by precocious activation of PPARs through ERK-cPLA2 pathway.
 ...
PMID:Leptin rapidly activates PPARs in C2C12 muscle cells. 1590 98

Leptin is now recognized as a proinflammatory cytokine and thought to be a progressive factor for non-alcoholic steatohepatitis (NASH). Here we showed the effects of leptin on the production of TNF-alpha (tumor necrosis factor-alpha) by Kupffer cells (KCs) with signal transduction. Leptin enhanced TNF-alpha production accompanied by a dose-dependent increase of MAPK activity in lipopolysaccharide (LPS)-stimulated KCs. SB203580 and JNK inhibitor I, specific inhibitors of P38 and JNK, inhibited TNF-alpha production in KCs but PD98059, an inhibitor of the ERK pathway, did not affect TNF-alpha production by KCs. Recombinant constitutively active adenovirus (Ad)-MKK6 and-MKK7 increased TNF-alpha production in KCs with activation of P38 and JNK without any change by Ad-MEK1 delivery. On the other hand, KCs isolated from the Zucker rat (fa/fa), a leptin receptor-deficient rat, showed reduced production of TNF-alpha on stimulation with LPS. The delivery of Ad-MKK6 and-MKK7, but not Ad-MEK1, increased TNF-alpha production in KCs of Zucker rats with activation of P38 and JNK. Addition of leptin to normal rats increased LPS-induced hepatic TNF-alpha production in vivo and leptin receptor-deficient Zucker rats showed reduced hepatic TNF-alpha production on addition of LPS in vivo. These findings indicate that P38 and JNK pathways are involved in the signal transduction of leptin enhancement of LPS-induced TNF-alpha production.
 ...
PMID:Leptin enhances TNF-alpha production via p38 and JNK MAPK in LPS-stimulated Kupffer cells. 1597 53

The role of two adipocytokines, adiponectin and leptin, in Taiwanese breast cancer patients remains to be determined. In this study, we analyzed the correlations between the serum levels of adiponectin and leptin and the various clinicopathological parameters in 100 newly diagnosed, histologically confirmed breast cancer patients and 100 controls. We found serum levels were decreased significantly for adiponectin in the breast cancer patients, in comparison to controls (Student t-test, P=0.003), while serum levels were increased significantly for leptin in the breast cancer patients in comparison to controls (Student t-test, P=0.025). Leptin/adiponectin (L/A ratio) were increased significantly in the breast cancer patients, in comparison to controls (Student t-test, P=0.009). Among the clinicopathological parameters, estrogen receptor, progesterone receptor, HER2/neu, lymph node metastasis, tumor stage, and tumor grade all showed no effect on the serum levels of adiponectin and leptin. BMI was negatively and positively correlated to serum adiponectin and leptin levels, respectively (Spearman's correlation, r=-0.333 and 0.323, respectively; P<0.001 for both). Intriguingly, serum L/A ratio disclosed a positive correlation to tumor size (r=0.21, P=0.036). In summary, our results suggest that low serum adiponectin levels and high serum leptin levels are associated with an increased risk for breast cancer. Also, independent of the effect of BMI, the increased serum ratio of L/A may indicate the presence of aggressive breast cancers.
 ...
PMID:Serum adiponectin and leptin levels in Taiwanese breast cancer patients. 1601 38

Leptin, a pleiotropic cytokine that regulates food intake and metabolic and endocrine responses, has emerged recently as an important regulator of mucosal inflammatory responses to bacterial infection. In this study, we report that in sublingual salivary gland acinar cells leptin plays a role in the suppression of up-regulation in endothelin-1 (ET-1), induced by the LPS of a periodontopathic bacterium P. gingivalis. We show that P. gingivalisLPS detrimental effect on salivary mucin synthesis, associated with up-regulation (3.9-fold) in ET-1 generation and the enhancement (3.2-fold) in endothelin-converting enzyme-1 (ECE-1) activity, was subject to a dose-dependent suppression by leptin. The impedance by leptin of the LPS inhibitory effect on mucin synthesis was blocked by wortmannin, an inhibitor of PI3K, as well as by ERK inhibitor, PD98059. However, while the blockade of ERK led also to amplification in the impedance by leptin of the LPS-induced expression of ECE-1 and ET-1, the effect was not observed in the presence of wortmannin. The findings are the first to demonstrate that leptin counters the pathological consequences of P. gingivalisinfection on the synthesis of salivary mucin through the involvement in signaling events of PI3K and ERK pathways. We also show that the ERK cascade represents a critical signaling target for leptin in the LPS-induced up-regulation in ET-1.
 ...
PMID:Role of leptin in modulation of Porphyromonas gingivalis lipopolysaccharide-induced up-regulation of endothelin-1 in salivary gland acinar cells. 1611 17


1 2 3 4 5 6 7 8 9 Next >>