calcimycin and Diabetes-Mellitus--Type-2

Clinical manifestations of diabetic nephropathy are an expression of diabetic microangiopathy. This review revisits the previously proposed Steno hypothesis and advances our hypothesis that development of endothelial cell dysfunction represents a common pathophysiological pathway of diabetic complications. Specifically, the ability of glucose to scavenge nitric oxide is proposed as the initiation phase of endothelial dysfunction. Gradual accumulation of advanced glycated end products and induction of plasminogen activator inhibitor-1, resulting in the decreased expression of endothelial nitric oxide synthase and reduced generation of nitric oxide, are proposed to be pathophysiologically critical for the maintenance phase of endothelial dysfunction. The proposed conceptual shift toward the role of endothelial dysfunction in diabetic complications may provide new strategies for their prevention.

Topics: Albuminuria; Animals; Bradykinin; Calcimycin; Cells, Cultured; Diabetes Mellitus, Type 2; Diabetic Angiopathies; Diabetic Nephropathies; Down-Regulation; Endothelium, Vascular; Glucose; Glycation End Products, Advanced; Humans; Hyperglycemia; Nitric Oxide; Nitric Oxide Synthase; Nitric Oxide Synthase Type III; Plasminogen Activator Inhibitor 1

We hypothesized that the maintenance of vascular homeostasis is critically dependent on the expression and reciprocal regulation of caveolin-1 (Cav-1) and endothelial nitric oxide synthase (eNOS) in endothelial cells (ECs). Skeletal muscle biopsies from subjects with type 2 diabetes showed 50% less Cav-1 and eNOS than those from lean healthy controls. The Cav-1:eNOS expression ratio was 200:1 in primary culture human ECs. Cav-1 small interfering RNA (siRNA) reduced eNOS protein and gene expression in association with a twofold increase in eNOS phosphorylation and nitrate production per molecule of eNOS, which was reversed in cells overexpressing Adv-Cav-1-GFP. Upon addition of the Ca

Topics: Adult; Albumins; Biopsy; Calcimycin; Calcium; Case-Control Studies; Caveolin 1; Cell Membrane; Diabetes Mellitus, Type 2; Endothelial Cells; HEK293 Cells; Human Umbilical Vein Endothelial Cells; Humans; Insulin; Intercellular Junctions; Ionophores; Middle Aged; Molecular Weight; Nitric Oxide; Nitric Oxide Synthase Type III; Nitrosation; Phosphorylation; Protein Transport; RNA, Small Interfering; src-Family Kinases

Insulin decreased A23187-induced hyperpolarization of the erythrocyte membrane in healthy donors. These data indicate that insulin plays a role in the regulation of Ca(2+)-activated potassium channels in human erythrocytes. However, insulin had little effect on hyperpolarization response of cells induced by artificial ascorbate--phenazine methosulfate donor-acceptor system. Addition of insulin to cell suspension from patients with type 2 diabetes mellitus did not modulate hyperpolarization of the erythrocyte membrane induced by A23187 or ascorbate-phenazine methosulfate, which reflects impairment of regulatory mechanisms for Ca(2+)-activated potassium channels in erythrocytes.

Topics: Arteries; Ascorbic Acid; Calcimycin; Calcium; Carbonyl Cyanide m-Chlorophenyl Hydrazone; Case-Control Studies; Diabetes Mellitus, Type 2; Erythrocytes; Female; Humans; Hydrogen-Ion Concentration; Hypertension; Insulin; Ionophores; Male; Methylphenazonium Methosulfate; Oxidation-Reduction

Increase in intracellular Ca2+ concentration caused by calcium ionophore A23187 or ascorbate+phenazine methosulphate electron donor system added to erythrocyte suspension induced similar shifts in erythrocyte membrane potential. These processes are most likely mediated by Ca2+-activated potassium channels. Changes in the osmolarity of the incubation medium produced opposite effects on membrane hyperpolarization induced by A23187 or ascorbate+phenazine methosulphate in erythrocyte isolated from healthy donors, which attests to the existence of different mechanisms of regulation of Ca2+-activated potassium channels. There was no difference in the volume-dependent changes of potassium permeability in cells from patients with type II diabetes mellitus combined with arterial hypertension induced by application A23187 or electron-donor system.

Topics: Calcimycin; Diabetes Mellitus, Type 2; Erythrocyte Membrane; Erythrocytes; Humans; Hypertension; Membrane Potentials; Osmolar Concentration; Potassium Channels, Calcium-Activated

Non-insulin-dependent diabetes mellitus (NIDDM) is characterized by the presence of abnormally active platelets in the circulation, leading to increased incidence of thrombotic complications. In this study, we have attempted to understand the pathophysiology of the platelets in NIDDM.. Platelet aggregation was induced by thrombin receptor-activating peptide or epinephrine. Membrane fluidity was derived from the steady-state fluorescence anisotropy of diphenylhexatriene incorporated in the membrane. The phosphotyrosine content of the platelet proteins was probed using specific monoclonal antibodies. The extent of calpain activity was assessed from the proteolysis of calpain substrates.. Aggregation was significantly enhanced (p<0.001) in the platelets obtained from the cases of NIDDM. Anisotropy measurements reflected a significant increase in the microviscosity of platelet membranes from 3.315 (+/-0.103) in the control to 4.153 (+/-0.119) in NIDDM. Proteins of relative mobilities of 131, 100, 47 and 38 kDa were found to remain phosphorylated on tyrosine in the resting platelets obtained from NIDDM patients, while they were not phosphorylated in the control counterparts. This was associated with heightened activity of the calcium-dependent thiol protease, calpain, in NIDDM.. Taken together, these data indicated significant changes in the signaling mechanism in the platelets obtained from NIDDM, which could lead to platelet hyperactivity in this disease.

Topics: Adult; Blood Platelets; Calcimycin; Calpain; Case-Control Studies; Cell Membrane; Diabetes Mellitus, Type 2; Epinephrine; Humans; Middle Aged; Phosphorylation; Pilot Projects; Platelet Activation; Platelet Aggregation; Reference Values; Signal Transduction; Tyrosine

The L-arginine uptake of resting platelets from type-2 diabetic patients and control subjects was measured and the kinetic parameters defined. The effect of platelet stimulation with agonists was also investigated. Kinetic studies showed that the K(m) value for L-arginine transport was not different in patients compared with control subjects, while V(max) was significantly decreased in patients compared with controls. Moreover, agonists able to mobilize Ca(2+) produced a further decrease in the L-arginine uptake in controls and in patients, suggesting that Ca(2+) intracellular levels down-regulate L-arginine transport in platelets from both control subjects and patients. Data suggest that drugs designed to control intracellular Ca(2+) might restore platelet function in diabetic patients.

Topics: Aged; Arginine; Blood Platelets; Calcimycin; Calcium; Diabetes Mellitus, Type 2; Dose-Response Relationship, Drug; Down-Regulation; Female; Humans; Kinetics; Male; Middle Aged; Nitric Oxide; Time Factors

In order to evaluate polymorphonuclear leukocyte (PMN) activity in diabetes mellitus, leukotriene B4 (LTB4) levels were measured in sixty patients, 31 affected with Type 1 diabetes mellitus and 29 affected with Type 2 diabetes mellitus. The LTB4 levels (12.1+/-0.2 pg/100 microl) in diabetic patients were higher compared to those of the control group (7.9+/-0.1 pg/100 microl) (P < 0.001), and remained significantly higher (P < 0.001) (12.8+/-0.2 pg/100 microl) than in the control group (11.0+/-0.2 pg/100 microl) after stimulation with calcium ionophore. A significant and positive correlation between glycated hemoglobin and LTB4 was demonstrated (P < 0.001, r = 0.80). This study demonstrates that in diabetic patients there is a PMN activation and that this activation is correlated to glycated hemoglobin level.

Topics: Adult; Aged; Blood Glucose; Calcimycin; Diabetes Mellitus, Type 1; Diabetes Mellitus, Type 2; Female; Glycated Hemoglobin; Humans; In Vitro Techniques; Leukotriene B4; Male; Middle Aged; Neutrophils; Reference Values; Regression Analysis

There has been a prejudice that diabetes modulates the function of saphenous vein in a manner that predisposes to bypass graft failure, although most of the evidence accrues from animal studies. We have investigated the effect of diabetes on the vasodilator responses and ultrastructure of saphenous vein harvested from patients undergoing infrainguinal bypass surgery for limb salvage and the development of stenoses within the vein grafts. Of 55 consecutive patients undergoing vein bypass surgery for critical ischemia, 16 (29%) were diabetic: diabetes was not a risk factor for graft stenosis, which occurred in 17 of 56 (30%) grafts. Endothelium-dependent relaxation by nitric oxide pathways stimulated after receptor activation (bradykinin and thrombin) was not different in vein rings from diabetic (n = 12) and nondiabetic patients (n = 12). Prostarioid-mediated vasorelaxation was absent in vein rings from diabetic patients, and the production of 6-keto prostaglandin F(1alpha) (PGF(1alpha)) from diabetic vein was only 66 +/- 27 pg x cm-2 x min-1 compared with 112 +/- 20 pg x cm-2 x min-1 from control vein (P = 0.011). Fibrinogen-mediated vasorelaxation, normally inhibited by K+ channel blockers, was negligible in vein from diabetic patients. No ultrastructural differences were observed between the endothelium of saphenous vein harvested from diabetic and nondiabetic patients. However, diabetes was associated significantly with the presence of spiraled collagen in media. The maintenance of receptor-activated stimulation of nitric oxide pathways and the damping of the response to fibrinogen in saphenous vein endothelium may provide, in part, for the good prognosis of vein graft surgery in diabetic patients: diabetes is not a risk factor for early (12 months) infrainguinal vein graft stenosis.

Topics: Aged; Aged, 80 and over; Amputation, Surgical; Blood Vessel Prosthesis; Bradykinin; Calcimycin; Collagen; Diabetes Mellitus, Type 1; Diabetes Mellitus, Type 2; Diabetic Angiopathies; Endothelium, Vascular; Female; Fibrinogen; Humans; In Vitro Techniques; Indomethacin; Ischemia; Leg; Male; Microscopy, Electron; Middle Aged; NG-Nitroarginine Methyl Ester; Postoperative Complications; Saphenous Vein; Time Factors; Vascular Diseases; Vascular Surgical Procedures; Vasodilation

A long-term study to identify age-dependent alterations in vascular reactivity in obese Zucker rats, a model for non-insulin-dependent diabetes mellitus, was carried out. On aortic rings of 12-week-old obese Zucker rats, but not in older animals (36 and 52 weeks), the following different effects in comparison to the lean rat control group were observed: (i) a significantly enhanced maximal relaxation to acetylcholine and A23187, which was abolished by the nitric oxide-synthase inhibitor L-nitro-arginine methyl ester (L-NAME); relaxation of aortic rings to the endothelium-independent vasodilator nitroglycerin was similar; (ii) more pronounced maximal 5-hydroxytryptamine-induced-contractions in the presence of L-NAME, and (iii) a more pronounced reduction in phenylephrine-induced contractions by verapamil. These results are suggestive of an altered calcium metabolism in the first weeks of development in the obese rat strain, which is probably responsible for the hypotension seen in this early time period.

Topics: Acetylcholine; Aging; Animals; Arginine; Calcimycin; Diabetes Mellitus, Experimental; Diabetes Mellitus, Type 2; Endothelium, Vascular; In Vitro Techniques; Muscle Contraction; Muscle Relaxation; Muscle, Smooth, Vascular; NG-Nitroarginine Methyl Ester; Nitric Oxide; Rats; Rats, Zucker

Enhanced platelet functions have been reported in patients with diabetes mellitus. Our recent study demonstrated that phosphoinositide turnover is increased in platelets from diabetic patients. In the present study, we evaluated the abnormality in platelet intracellular calcium mobilization in patients with Type 2 (non-insulin-dependent) diabetes mellitus using fura-2, a fluorescent calcium indicator. Washed platelets were prepared from six diabetic patients with increased platelet aggregation rates (DM-A group), seven diabetic patients with normal platelet aggregation rates (DM-B group), and eight age-matched healthy control subjects. The basal intracellular free calcium concentrations in platelets were similar among the three groups. Thrombin (0.025-0.1 U/ml) induced a dose-dependent increase in intracellular calcium in both the presence and the absence of extracellular calcium. This increase in the presence of extracellular calcium, which depends on calcium influx and release, was significantly higher in the DM-A group than in the DM-B and control groups. However, there was no significant difference between the control group and the DM-B group. In the absence of extracellular calcium, thrombin-induced calcium increase, which depends only on calcium release, was also significantly enhanced in the DM-A group. Furthermore, the calcium increase stimulated by platelet-activating factor (10 nmol/l) with and without extracellular calcium was significantly higher in the DM-A group than in the other groups. Additionally, calcium ionophore A23187 (100 nmol/l) caused a significantly higher calcium increase in the DM-A group with extracellular calcium, while the calcium increase without extracellular calcium showed no significant difference among the three groups. These observations suggest that enhanced intracellular calcium mobilization due to increased calcium influx and release may be closely related to platelet hyperfunctions in diabetes mellitus.

Topics: Analysis of Variance; Blood Glucose; Blood Platelets; Calcimycin; Calcium; Calcium Chloride; Diabetes Mellitus, Type 2; Egtazic Acid; Female; Glycated Hemoglobin; Humans; In Vitro Techniques; Kinetics; Male; Middle Aged; Platelet Activating Factor; Platelet Aggregation; Reference Values; Thrombin

The hypoglycemic effect of gliclazide is mainly due to its action on ATP stimulated K+ channels, but the calcium ionophoretic effect of this drug may also be involved in its physiological properties. Using 1H NMR we demonstrated the antiionophoretic effect of nifedipine and diltiazem. We attempted to verify whether this in vitro interaction also occurs in vivo. A clinical trial, was performed on patients treated concomitantly with gliclazide and nifedipine or diltiazem. Results showed that no in vivo interaction occurred. The discrepancy between in vivo and in vitro results may be explained by a too weak plasma concentration in the case of nifedipine and by a large plasma protein binding in the case of diltiazem.

Topics: Adenosine Triphosphate; Aged; Binding Sites; Blood Glucose; Calcimycin; Calcium; Chromatography, Gas; Chromatography, High Pressure Liquid; Diabetes Mellitus, Type 2; Diltiazem; Drug Interactions; Female; Gliclazide; Humans; Insulin; Magnetic Resonance Spectroscopy; Male; Middle Aged; Nifedipine; Potassium Channels

The diminished insulin secretion of type 2 diabetes might result from abnormal regulation of the potassium permeability which leads to beta-cell depolarization. The possibility of a generalized defect has been investigated in vitro by the stimulation of 86Rb efflux from red cells of type 2 diabetic patients by calcium ionophore and its inhibition by quinine. Diabetic subjects and control subjects had identical 86Rb efflux stimulated by 0.2-0.6 microM calcium ionophore A23187 and identical inhibition by quinine with mean Ki 6 microM and 4 microM quinine respectively for 0.2 microM ionophore and mean Ki 38 microM and 37 microM quinine respectively for 0.6 microM ionophore.

Topics: Adult; Calcimycin; Calcium; Diabetes Mellitus, Type 2; Erythrocytes; Humans; Ion Channels; Middle Aged; Potassium; Quinine