Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.6.1.3 (ATPase)
 65,361 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Systemic hyperinsulinemia induces vasodilation in human skeletal muscle. This vasodilation contributes to insulin-stimulated glucose uptake and has been found to be reduced in various insulin-resistant states. The mechanism of the effect of insulin on vascular tone is not completely understood. We hypothesized that activation of the sodium-potassium pump (Na+, K(+)-ATPase) located in endothelial or smooth muscle cells would be involved in the insulin-mediated vasodilation. Therefore, in 24 healthy, nonsmoking, nonobese, normotensive volunteers, we infused ouabain, a specific inhibitor of Na+, K(+)-ATPase, into the brachial artery before and during euglycemic hyperinsulinemia. As expected, insulin (systemic concentrations, approximately 700 [low] and 1400 [high] pmol.L-1) induced vasodilation in the control arm (forearm blood flow [FBF, plethysmography] from 1.6 +/- 0.2 to 2.1 +/- 0.4 mL.dL-1.min-1 [low insulin] and from 1.6 +/- 0.2 to 2.1 +/- 0.2 [high insulin], P < .05 for both), but the increase in FBF was abolished in the ouabain-infused forearm (from 1.3 +/- 0.1 to 1.4 +/- 0.2 mL.dL-1.min-1 [low] and from 1.3 +/- 0.1 to 1.3 +/- 0.1 [high], P = NS). Ouabain-induced increases in forearm potassium release were partly reversed by insulin. To investigate whether the mechanism of action could be at the endothelial level, we infused NG-monomethyl-I-arginine (L-NMMA), an inhibitor of endothelial nitric oxide synthase (0.05, 0.1, and 0.2 mg.dL-1.min-1) intra-arterially in 12 subjects and induced a clear dose-dependent decrease of FBF from 1.7 +/- 0.2 to 1.2 +/- 0.1 mL.dL-1.min-1 (P < .01). In contrast, after ouabain (and continued insulin) infusion, L-NMMA had no effect on FBF (from 1.6 +/- 0.4 to 1.5 +/- 0.3 mL.dL-1.min-1, n = 6, P = .66). These results demonstrate that insulin induces vasodilation by stimulation of Na+, K(+)-ATPase. This activation of Na+, K(+)-ATPase could occur at the level of the endothelium rather than that of vascular smooth muscle and contributes to the endothelium-dependent vasodilator response to insulin.
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PMID:Activation of the sodium-potassium pump contributes to insulin-induced vasodilation in humans. 879 28

This study was conducted to evaluate the influence of proinsulin C-peptide on erythrocyte Na(+),K(+)-ATPase and endothelial nitric oxide synthase activities in patients with type I diabetes. In a randomized double-blind study design, ten patients with type I diabetes received intravenous infusions of either human C-peptide or physiological saline on two different occasions. C-peptide was infused at a rate of 3 pmol.min(-1).kg(-1) for 60 min, and thereafter at 10 pmol.min(-1).kg(-1) for 60 min. At baseline and after 60 and 120 min, laser Doppler flow (LDF) was measured following acetylcholine iontophoresis or mild thermal stimulation (44 degrees C), and venous blood samples were collected to determine plasma cGMP levels and erythrocyte membrane Na(+),K(+)-ATPase activity. The LDF response to acetylcholine increased during C-peptide infusion and decreased during saline infusion [18.6+/-19.2 and -13.2+/-9.4 arbitrary units respectively; mean+/-S.E.M.; P<0.05). No significant change in LDF was observed after thermal stimulation. The baseline plasma concentration of cGMP was 5.5+/-0.6 nmol.l(-1); this rose to 6.8+/-0.9 nmol.l(-1) during C-peptide infusion (P<0.05). Erythrocyte Na(+),K(+)-ATPase activity increased from 140+/-29 nmol of P(i).h(-1).mg(-1) in the basal state to 287+/-5 nmol of P(i). h(-1).mg(-1) during C-peptide infusion (P<0.01). There was a significant linear relationship between plasma C-peptide levels and erythrocyte Na(+),K(+)-ATPase activity during the C-peptide infusion (r=0.46, P<0.01). No significant changes in plasma cGMP levels or Na(+),K(+)-ATPase activity were observed during saline infusion. This study demonstrates an effect of human proinsulin C-peptide on microvascular function, which might be mediated by an increase in NO production and an activation of the erythrocyte Na(+),K(+)-ATPase. These mechanisms are compatible with the previous observed microvascular effects of C-peptide in patients with type I diabetes.
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PMID:Effects of proinsulin C-peptide on nitric oxide, microvascular blood flow and erythrocyte Na+,K+-ATPase activity in diabetes mellitus type I. 1067 86

Proinsulin C-peptide ameliorates renal and autonomic nerve function and increases skeletal muscle blood flow, oxygen uptake and glucose transport in patients with insulin-dependent diabetes mellitus. These effects have in part been ascribed to the stimulatory influence of C-peptide on Na+,K+-ATPase and endothelial nitric oxide synthase. To evaluate the capacity of C-peptide to insert into lipid bilayers and form ion channels, C-peptide secondary structure and membrane interactions were studied with circular dichroism spectroscopy and size exclusion chromatography. C-peptide is shown to lack a stable secondary structure, both when part of proinsulin and when free in aqueous solution, although the N-terminal third of the peptide exhibits an alpha-helical conformation in trifluoroethanol. Moreover, C-peptide remains disordered in the aqueous solvent in the presence of lipid vesicles, regardless of vesicle composition. In conclusion, C-peptide is unlikely to elicit physiological effects through stable conformation-dependent interactions with lipid membranes.
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PMID:Unordered structured of proinsulin C-peptide in aqueous solution and in the presence of lipid vesicles. 1076 28

The C-peptide of proinsulin is important for the biosynthesis of insulin but has for a long time been considered to be biologically inert. Data now indicate that C-peptide in the nanomolar concentration range binds specifically to cell surfaces, probably to a G protein-coupled surface receptor, with subsequent activation of Ca(2+)-dependent intracellular signaling pathways. The association rate constant, K(ass), for C-peptide binding to endothelial cells, renal tubular cells, and fibroblasts is approximately 3. 10(9) M(-1). The binding is stereospecific, and no cross-reaction is seen with insulin, proinsulin, insulin growth factors I and II, or neuropeptide Y. C-peptide stimulates Na(+)-K(+)-ATPase and endothelial nitric oxide synthase activities. Data also indicate that C-peptide administration is accompanied by augmented blood flow in skeletal muscle and skin, diminished glomerular hyperfiltration, reduced urinary albumin excretion, and improved nerve function, all in patients with type 1 diabetes who lack C-peptide, but not in healthy subjects. The possibility exists that C-peptide replacement, together with insulin administration, may prevent the development or retard the progression of long-term complications in type 1 diabetes.
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PMID:Role of C-peptide in human physiology. 1078 Sep 30

Studies have demonstrated that proinsulin C-peptide stimulates the activities of Na(+),K(+)-ATPase and endothelial nitric oxide synthase, both of which are enzyme systems of importance for nerve function and known to be deficient in type 1 diabetes. The aim of this randomized double-blind placebo-controlled study was to investigate whether C-peptide replacement improves nerve function in patients with type 1 diabetes. Forty-nine patients without symptoms of peripheral neuropathy were randomized to either 3 months of treatment with C-peptide (600 nmol/24 h, four doses s.c.) or placebo. Forty-six patients (15 women and 31 men, aged 29 years, diabetes duration 10 years, and HbA(1c) 7.0%) completed the study. Neurological and neurophysiological measurements were performed before and after 6 and 12 weeks of treatment. At baseline the patients showed reduced nerve conduction velocities in the sural nerve (sensory nerve conduction velocity [SCV]: 50.9 +/- 0.70 vs. 54.2 +/- 1.2 m/s, P < 0.05) and peroneal nerve (motor nerve conduction velocity: 45.7 +/- 0.55 vs. 53.5 +/- 1.1 m/s, P < 0.001) compared with age-, height-, and sex-matched control subjects. In the C-peptide treated group there was a significant improvement in SCV amounting to 2.7 +/- 0.85 m/s (P < 0.05 compared with placebo) after 3 months of treatment, representing 80% correction of the initial reduction in SCV. The change in SCV was accompanied by an improvement in vibration perception in the patients receiving C-peptide (P < 0.05 compared with placebo), whereas no significant change was detectable in cold or heat perception. In conclusion, C-peptide administered for 3 months as replacement therapy to patients with early signs of diabetic neuropathy ameliorates nerve dysfunction.
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PMID:Amelioration of sensory nerve dysfunction by C-Peptide in patients with type 1 diabetes. 1254 Jun 32

Proinsulin C-peptide was for long considered to be without biological activity of its own. New findings demonstrate, however, that it is capable of eliciting both molecular and physiological effects, suggesting that C-peptide is in fact a bioactive peptide. When administered in replacement doses to animal models or to patients with type 1 diabetes, C-peptide ameliorates diabetes-induced functional and structural changes in both the kidneys and the peripheral nerves. It augments blood flow in a number of tissues, notably skeletal muscle, myocardium, skin and nerve. These effects are thought to be mediated via a stimulatory influence on Na+,K(+)-ATPase and on endothelial nitric oxide synthase. Specific binding of C-peptide to cell membranes of intact cells and to detergent-solubilized cellular components has been demonstrated, indicating the existence of cell-surface binding sites for C-peptide. A number of intracellular responses are elicited by C-peptide, including a rise in Ca2+ concentration and activation of MAP-kinase signaling pathways. Many but not all of C-peptide's intracellular effects can be inhibited by pertussis toxin, supporting the notion that C-peptide may interact via a G-protein-coupled receptor. Additional data suggest that C-peptide may interact synergistically also in the insulin signaling pathway. Combined, the available observations show conclusively that C-peptide is biologically active, even though its molecular mechanism of action is not as yet fully understood. The possibility that replacement of C-peptide in patients with type 1 diabetes may serve to retard or prevent the development of long-term complications should be evaluated.
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PMID:C-peptide makes a comeback. 1295 45

Statins, 3-hydroxy-3-methylglutaryl CoA reductase inhibitors, acutely increase endothelial nitric oxide synthase (eNOS) activity and chronically increase eNOS expression in endothelial cells. NO decreases transport in thick ascending limbs (TAL). We hypothesized that statins inhibit TAL transport by acutely activating eNOS, thereby increasing NO production and chronically enhancing eNOS expression. Oxygen consumption (QO(2)) by TAL suspensions from Sprague-Dawley rats was used as a measure of active NaCl reabsorption. Na/K ATPase activity was assessed by measuring ATP hydrolysis in the presence and absence of ouabain. eNOS expression was measured by Western blot. A total of 50 micro M pravastatin decreased QO(2) by 18.6 +/- 3.4% (P < 0.01). In the presence of 500 micro M furosemide and 200 micro M amiloride, transport blockers, QO(2) remained the same after pravastatin was added. Na/K ATPase activity was not different from controls and TAL treated with 50 micro M pravastatin (0.33 +/- 0.07 versus 0.29 +/- 0.04 nmol P(i)/ micro g protein/min, where P(i) is inorganic phosphate). Nystatin stimulated QO(2) to 178 +/- 13.7 in pravastatin-treated TAL and 195 +/- 11.5 in furosemide-treated TAL. The inhibitory effect of pravastatin on QO(2) was blocked by L-nitroarginine methyl ester, an NOS inhibitor. In addition, pravastatin increased NO production as measured by the fluorescent dye DAF-2A. Pravastatin at a dose of 10 mg/kg per d had no effect on eNOS protein at 1 d (24.1 +/- 2.7 versus 25.5 +/- 1.1 arbitrary units [AU]) or 7 d (24.1 +/- 2.7 versus 20.9 +/- 1.3 AU). Similarly, at 1 d, 50 mg/kg per d had no effect on expression (24.1 +/- 2.7 versus 21.2 +/- 3.6 AU). At 7 d, this dose decreased eNOS protein from 24.1 +/- 2.7 to 11.8 +/- 4.4 AU. It is concluded that pravastatin acutely decreases NaCl entry into the TAL by releasing NO. Pravastatin does not chronically increase eNOS expression in TAL.
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PMID:Acute and chronic regulation of thick ascending limb endothelial nitric oxide synthase by statins. 1474 73

The most common microvascular diabetic complication, diabetic peripheral polyneuropathy (DPN), affects type 1 diabetic patients more often and more severely. In recent decades, it has become increasingly clear that perpetuating pathogenetic mechanisms, molecular, functional, and structural changes and ultimately the clinical expression of DPN differ between the two major types of diabetes. Impaired insulin/C-peptide action has emerged as a crucial factor to account for the disproportionate burden affecting type 1 patients. C-peptide was long believed to be biologically inactive. However, it has now been shown to have a number of insulin-like glucose-independent effects. Preclinical studies have demonstrated dose-dependent effects on Na+,K(+)-ATPase activity, endothelial nitric oxide synthase (eNOS), and endoneurial blood flow. Furthermore, it has regulatory effects on neurotrophic factors and molecules pivotal to the integrity of the nodal and paranodal apparatus and modulatory effects on apoptotic phenomena affecting the diabetic nervous system. In animal studies, C-peptide improves nerve conduction abnormalities, prevents nodal degenerative changes, characteristic of type 1 DPN, promotes nerve fiber regeneration, and prevents apoptosis of central and peripheral nerve cell constituents. Limited clinical trials have confirmed the beneficial effects of C-peptide on autonomic and somatic nerve function in patients with type 1 DPN. Therefore, evidence accumulates that replacement of C-peptide in type 1 diabetes prevents and even improves DPN. Large-scale food and drug administration (FDA)-approved clinical trials are necessary to make this natural substance available to the globally increasing type 1 diabetic population.
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PMID:Type 1 diabetic neuropathy and C-peptide. 1519 72

Cardiac hypertrophy leading to heart failure is a major cause of morbidity and mortality worldwide. The 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors, or statins, have been shown to inhibit cardiac hypertrophy and improve symptoms of heart failure by cholesterol-independent mechanisms. Statins block the isoprenylation and function of members of the Rho guanosine triphosphatase family, such as Rac1 and RhoA. Because Rac1 is a requisite component of reduced nicotinamide adenine dinucleotide phosphate oxidase, which is a major source of reactive oxygen species in cardiovascular cells, the ability of statins to inhibit Rac1-mediated oxidative stress contributes importantly to their inhibitory effects on cardiac hypertrophy. Furthermore, inhibition of RhoA by statins leads to the activation of protein kinase B/Akt and up-regulation of endothelial nitric oxide synthase in the endothelium and the heart. This results in increased angiogenesis and myocardial perfusion, decreased myocardial apoptosis, and improvement in endothelial and cardiac function. Because these effects of statins occur independently of cholesterol lowering, statins may have therapeutic benefits in nonhyperlipidemic patients with cardiac hypertrophy and heart failure.
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PMID:Statin therapy for cardiac hypertrophy and heart failure. 1552 46

Nitric oxide is implicated in a variety of signaling pathways in different systems, notably in endothelial cells. Some of its effects can be exerted through covalent modifications of proteins and, among these modifications, increasing attention is being paid to S-nitrosylation as a signaling mechanism. In this work, we show by a variety of methods (ozone chemiluminescence, biotin switch, and mass spectrometry) that the molecular chaperone Hsp90 is a target of S-nitrosylation and identify a susceptible cysteine residue in the region of the C-terminal domain that interacts with endothelial nitric oxide synthase (eNOS). We also show that the modification occurs in endothelial cells when they are treated with S-nitroso-l-cysteine and when they are exposed to eNOS activators. Hsp90 ATPase activity and its positive effect on eNOS activity are both inhibited by S-nitrosylation. Together, these data suggest that S-nitrosylation may functionally regulate the general activities of Hsp90 and provide a feedback mechanism for limiting eNOS activation.
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PMID:S-nitrosylation of Hsp90 promotes the inhibition of its ATPase and endothelial nitric oxide synthase regulatory activities. 1593 23


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