Biomedical subjects

Alessandra Gallo

Publications and source records attributed to Alessandra Gallo.

4 recordsLinked to original sources

PubMed2006

Insulin generates free radicals in human fibroblasts ex vivo by a protein kinase C-dependent mechanism, which is inhibited by pravastatin.

Insulin can generate oxygen free radicals. Statins, 3-hydroxy-3-methylglutaryl-coenzyme A reductase inhibitors, exert a powerful antioxidant effect. The present study aimed to clarify the mechanisms through which insulin generates free radicals and to assess whether pravastatin modulates such effects. In cultured skin fibroblasts from human volunteers exposed to high insulin concentration, either in the presence or in the absence of pravastatin, insulin induced translocation of the p47(phox) subunit of NAD(P)H oxidase from the cytosol to the membrane and generation of radical oxygen species through a PKC delta-dependent mechanism. The insulin-induced translocation of p47(phox) was PKC delta dependent and attenuated by pravastatin, but independent of the activation of Akt and Rac1. Insulin-induced Akt phosphorylation was increased by pravastatin and ERK1/2 phosphorylation attenuated. The present study demonstrates a novel mechanism by which insulin stimulates the generation of free radicals in human fibroblasts, ex vivo. It involves phosphatidylinositol 3-kinase, PKC delta, and p47(phox) translocation and promotes ERK1/2 phosphorylation. Pravastatin inhibited radical oxygen species production by inhibiting PKC delta. These observations offer a robust explanation for the positive effects of pravastatin treatment in patients with insulin resistance syndrome.

Cells, Cultured↗

PubMed2006

Endothelial dysfunction in type 2 diabetes mellitus.

AIMS: Vascular endothelial cells play a major role in maintaining cardiovascular homeostasis in health. Diabetes mellitus (DM) substantially impairs the vasodilating properties of the endothelium and leads to endothelial dysfunction, which can thus be considered the first step in the progression of cardiovascular disease. The aim of the present study is to illustrate possible mechanisms responsible for endothelial dysfunction in DM. DATA SYNTHESIS: We have shown that NADPH oxidase gene expression is increased in circulating lymphomonocytes from patients with DM, and that this increased gene expression is dependent upon metabolic control. Hyperglycemia can mediate its adverse effects through the activation of protein kinase C. We have shown an increase in membrane-associated PKC beta 2 activity in monocytes from patients with DM. This activity was reduced by 40% in the euglycemic condition. Finally, we show a reduction of the circulating endothelial progenitor cells, a subset of bone marrow-derived endothelial-oriented stem cells, which can give rise to mature endothelial cells. CONCLUSION: Endothelial dysfunction, the initial step of the atherosclerotic process, is reversible. Thus, major efforts should be made to control not only hyperglycemia but also the other risk factors for cardiovascular disease, in order to prevent the onset of all these processes that eventually leads the diabetic patient to premature death.

Diabetes Complications↗

PubMed2005

Metformin prevents glucose-induced protein kinase C-beta2 activation in human umbilical vein endothelial cells through an antioxidant mechanism.

Hyperglycemia determines the vascular complications of diabetes through different mechanisms: one of these is excessive activation of the isoform beta2 of protein kinase C (PKC-beta2). Metformin, a widely used antidiabetic agent, is associated with decreased cardiovascular mortality in obese type 2 diabetic patients. Therefore, we assessed the role of metformin in glucose-induced activation of PKC-beta2 and determined the mechanism of its effect in human umbilical venous endothelial cells grown to either normo- (5 mmol/l) or hyperglycemia (10 mmol/l) and moderately and acutely exposed to 25 mmol/l glucose. We studied PKC-beta2 activation by developing adenovirally expressed chimeras encoding fusion protein between green fluorescent protein (GFP) and conventional beta2 isoform (PKC-beta2-GFP). Glucose (25 mmol/l) induced the translocation of PKC-beta2-GFP from the cytosol to the membrane in cells grown to hyperglycemia but not in those grown in normal glucose medium. Metformin (20 micromol/l) prevented hyperglycemia-induced PKC-beta2-GFP translocation. We also assessed oxidative stress under the same conditions with a 4-((9-acridine-carbonyl)amino)-2,2,6,6-tetramethylpiperidin-oxyl,free radical (TEMPO-9-AC) fluorescent probe. We observed significantly increased radical oxygen species production in cells grown in hyperglycemia medium, and this effect was abolished by metformin. We show that in endothelial cells, metformin inhibits hyperglycemia-induced PKC-beta2 translocation because of a direct antioxidant effect. Our data substantiate the findings of previous large intervention studies on the beneficial effect of this drug in type 2 diabetic patients.

Cells, Cultured↗

PubMed2002

Epinephrine effects on insulin-glucose dynamics: the labeled IVGTT two-compartment minimal model approach.

The hyperglycemic effects of epinephrine (Epi) are established; however, the modulation of Epi-stimulated endogenous glucose production (EGP) by glucose and insulin in vivo in humans is less clear. Our aim was to determine the effect of exogenously increased plasma Epi concentrations on insulin and glucose dynamics. In six normal control subjects, we used the labeled intravenous glucose tolerance test (IVGTT) interpreted with the two-compartment minimal model, which provides not only glucose effectiveness (S(G)(2*)), insulin sensitivity (S(I)(2*)), and plasma clearance rate (PCR) at basal state, but also the time course of EGP. Subjects were randomly studied during either saline or Epi infusion (1.5 microg/min). Exogenous Epi infusion increased plasma Epi concentration to a mean value of 2,034 +/- 138 pmol/l. During the stable-label IVGTT, plasma glucose, tracer glucose, and insulin concentrations were significantly higher in the Epi study. The hormone caused a significant (P < 0.05) reduction in PCR in the Epi state when compared with the basal state. The administration of Epi has a striking effect on EGP profiles: the nadir of the EGP profiles occurs at 21 +/- 7 min in the basal state and at 55 +/- 13 min in the Epi state (P < 0.05). In conclusion, we have shown by use of a two-compartment minimal model of glucose kinetics that elevated plasma Epi concentrations have profound effects at both hepatic and tissue levels. In particular, at the liver site, this hormone deeply affects, in a time-dependent fashion, the inhibitory effect of insulin on glucose release. Our findings may explain how even a normal subject may have the propensity to develop glucose intolerance under the influence of small increments of Epi during physiological stress.

Adult↗