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Biomedical subjects

M Farnararo

Publications and source records attributed to M Farnararo.

At least 37 records · Page 2Linked to original sources
PubMed1994

Bradykinin stimulates fructose 2,6-bisphosphate metabolism in human fibroblasts.

Bradykinin (BK), a peptide released during inflammatory response, has been investigated for its ability to regulate glucose metabolism in human fibroblasts. The peptide is able to significantly increase glycolytic flux in these cells. The strict relationship between the glycolytic rate and the levels of fructose 2,6-bisphosphate (Fru-2,6-P2) strongly suggests that the metabolite plays a key role in the regulation of glucose metabolism by bradykinin. The mechanism by which bradykinin increases Fru-2,6-P2 content involves the activation of 6-phosphofructo-2-kinase (PFK-2), the enzyme responsible for the synthesis of the metabolite. The study of the multiple signalling systems triggered by bradykinin demonstrates the involvement of the rise in intracellular Ca2+ concentration and of protein kinase C mediated pathway in the mechanism by which bradykinin increases Fru-2,6-P2 content and PFK-2 activity.

Bradykinin↗
PubMed1993

Glutamine utilization in resting and stimulated platelets.

Exogenous glutamine was metabolized by platelets to glutamate, aspartate, and CO2; whereas no lactate was formed. The amount of aspartate and CO2 produced from glutamine was reduced by the presence of glucose. On the other hand the rate of oxidation of glucose was reduced by the presence of glutamine. The potential energetic value of glutamine was lower than that of glucose, but the amino acid appeared to be a preferential respiratory substrate. The energy provision from glutamine also plays a role in the process of platelet activation, known to require an extra supply of ATP, since thrombin increased the rate of glutamine utilization in platelets. Upon cell activation an increase in aspartate and CO2 formation was observed and the stimulatory effect on glutamine oxidation by thrombin was also maintained in the presence of glucose.

Aspartic Acid↗
PubMed1993

Effect of aging on insulin regulation of fructose 2,6-bisphosphate metabolism in human fibroblasts.

Fructose 2,6-bisphosphate (Fru-2,6-P2) content in human fibroblasts is under hormonal control and is strictly related to glycolytic flux. In the present study it has been examined whether aging process is accompanied with an impairment in the control exerted by insulin on the metabolite content. Upon insulin stimulation old fibroblasts show a reduced increase in Fru-2,6-P2 content and glycolytic flux. Similarly, 6-phosphofructo-2-kinase (PFK-2) activity in old fibroblasts is increased at a lesser extent by insulin treatment, suggesting that an impairment at post-receptor level in the signalling pathway of insulin might occur with aging. In addition in unstimulated senescent fibroblasts PFK-2 displays higher activity and reduced Km for substrate, suggesting either that during senescence PFK-2 undergoes a post-translational modification or that a different PFK-2 isoenzyme is expressed.

Cell Line↗
PubMed1992

Role of the glycosylphosphatidylinositol/inositol phosphoglycan system in human fibroblast proliferation.

The involvement of the glycosylphosphatidylinositol/inositol phosphoglycan (gly-PtdIns/IPG) system in the stimulation of macromolecular syntheses in human fibroblasts has been investigated. The study demonstrates that an insulin sensitive gly-PtdIns/IPG system is present in human fibroblasts, that IPG can significantly stimulate DNA, RNA, and protein synthesis, and that the action of insulin on DNA synthesis as well as that of IPG can be significantly reduced by a specific anti-IPG antibody. These results strongly support the hypothesis that the gly-PtdIns/IPG system is involved in the signal transduction pathway leading to the stimulation of cell proliferation.

Cell Division↗
PubMed1991

An inositol phosphoglycan stimulates glycolysis in human platelets.

Upon hydrolysis of membrane glycosyl-phosphatidylinositol (gly-PtdIns), an inositol phosphoglycan (IPG) is generated, responsible for multiple biological activities and recently proposed as mediator of the action of a variety of hormones and growth factors. The present study shows that IPG is able to significantly stimulate platelet glycolysis, which represents the major energy producing pathway in this cell system. The activation of glycolytic flux induced by IPG appears to be specific and very rapid even though the molecular mechanism involved remains to be elucidated.

Blood Platelets↗
PubMed1990

A phospho-oligosaccharide can reproduce the stimulatory effect of insulin on glycolytic flux in human fibroblasts.

It has been recently demonstrated that insulin promotes the hydrolysis of a glycosyl-phosphatidylinositol, stimulating the release of a phospho-oligosaccharide which displays several insulin-like effects. In the present study we have investigated whether the compound is able to mimic insulin action on glucose metabolism in human fibroblasts. Similarly to the hormone, the phospho-oligosaccharide elicited a dose dependent increase in lactate output and fructose 2,6-bisphosphate content. The effect of the compound was time dependent with a progressive increase starting from 2 hours of incubation. 1 microM phospho-oligosaccharide had half maximal effect on both parameters, increasing glycolytic flux by approximately 30% and fructose 2,6-bisphosphate content by 70%. Therefore the phospho-oligosaccharide appears to be able to strictly reproduce insulin action on glucose metabolism in human fibroblasts.

Cells, Cultured↗
PubMed1989

Synthesis of diacylglycerol de novo is responsible for permanent activation and down-regulation of protein kinase C in transformed cells.

We measured the synthesis of diacylglycerol de novo in normal NIH/3T3 fibroblasts and in cells transformed by ras, src, sis and abl oncogenes. Analysis of the incorporation of glucose-derived 14C into diacylglycerol indicated that neosynthesis of diacylglycerol was constitutively active in the transformed cell lines. Elevated levels of diacylglycerol and persistent activation/down-regulation of protein kinase C reduced the binding of phorbol dibutyrate to transformed cells. This phenomenon could be reversed by blocking the glycolytic pathway, thus indicating that neosynthesized diacylglycerol was responsible for persistent activation and down-regulation of protein kinase C. In transformed cells, protein kinase C activity could not be stimulated by the addition of diolein; however, inhibition of glycolysis restored the ability of transformed cells to respond to diolein. Taken together these data indicate that constitutive synthesis of diacylglycerol de novo is responsible for activation and down-regulation of protein kinase C in transformed cells, and it may play a role in altered mitogenic signalling.

Animals↗
PubMed1989

pH sensitivity of the thrombin-induced rise in fructose 2,6-bisphosphate content of human platelets.

The stimulation of human platelets with thrombin results in a rapid and sustained increase in the fructose 2,6-bisphosphate content which may play an important role in the potentiation of glycolytic flux induced by the agonist. The investigation of the effect of pH on thrombin-induced rise in platelet fructose 2,6-bisphosphate content is reported here. The results indicate that the early intracellular alkalinization which follows platelet stimulation may contribute to mediate the positive effect of thrombin on the regulatory metabolite.

Blood Platelets↗
PubMed1989

An endpoint enzymatic assay for fructose 2,6-bisphosphate performed in 96-well plates.

An endpoint enzymatic assay for fructose 2,6-bisphosphate based on the ability of the compound to stimulate pyrophosphate 6-phosphofructo-1-kinase and performed in a 96-well plate is reported here. The method presents a low detection limit and a high sensitivity that could be further improved; moreover, the use of 96-well plates greatly increases the number of samples that can be simultaneously assayed.

Enzyme-Linked Immunosorbent Assay↗
PubMed1989

Fructose 2,6-bisphosphate and insulin stimulation of glycolysis in 3T3-L1 adipocytes.

1. Insulin is able to stimulate lactate production and to enhance fructose 2,6-bisphosphate (Fru-2,6-P2) content in 3T3-L1 adipocytes. 2. Phorbol 12-myristate 13-acetate is more efficacious than insulin in rising Fru-2,6-P2 content and less effective in the stimulation of glycolysis. 3. 3T3-L1 adipocyte 6-phosphofructo-l-kinase appears to be very sensitive to exogenous Fru-2,6-P2. 4. Insulin treatment does not affect the maximum activity of 6-phosphofructo-1-kinase whereas it markedly increases the affinity of pyruvate kinase for phosphoenolpyruvate. 5. The role of Fru-2,6-P2 in the insulin induced enhancement of glycolytic flux is discussed.

Adipose Tissue↗
PubMed1987

Adenylate cyclase stimulating agents and mitogens raise fructose 2,6-bisphosphate levels in human fibroblasts. Evidence for a dual control of the metabolite.

Fructose 2,6-bisphosphate, the most potent activator of 6-phosphofructo-1-kinase, has been demonstrated to mediate the increase of glycolytic flux induced by mitogens human fibroblasts. In the present work the molecular basis of transmembrane control of fructose 2,6-bisphosphate has been investigated. Prostacyclin and isoprenaline, known to activate adenylate cyclase, are able to increase fructose 2,6-bisphosphate levels, indicating that in human fibroblasts cyclic AMP plays a positive role in the control of the metabolite concentration, opposite to that exerted in hepatocytes. Substances known to activate protein kinase C such as phorbol 12-myristate 13-acetate, or to stimulate phosphoinositide turnover such as thrombin and bradykinin are also effective in raising fructose 2,6-bisphosphate. Therefore, we conclude that cyclic AMP and protein kinase C are likely involved in the control of fructose 2,6-bisphosphate levels in human fibroblasts.

Adenylyl Cyclases↗
PubMed1987

Mechanism of thrombin-induced rise in platelet fructose 2,6-bisphosphate content. Studies using phorbol myristate acetate, dioctanoylglycerol and ionophore A23187.

The mechanism by which thrombin increases platelet fructose 2,6-bisphosphate content was investigated. The action of thrombin was mimicked by phorbol 12 myristate 13-acetate and 1,2-dioctanoylglycerol. Ca2+ with A23187 potentiated the action of both these compounds. The action of thrombin required mobilization of intracellular and extracellular Ca2+ and was not decreased by indomethacin. This study suggests that protein kinase C activation and Ca2+ mobilization are both involved in the activation of glycolysis by thrombin.

Blood Platelets↗
PubMed1986

Fructose 2,6-bisphosphate in human platelets: its possible role in the control of basal and thrombin-stimulated glycolysis.

Human platelets contain fructose 2,6-bisphosphate, 6-phosphofructo-l-kinase (ATP: D-Fructose-6-phosphate-1-phosphotransferase, E.C.2.7. 1.11), the rate-limiting enzyme in platelet glycolysis appear to be significantly activated by physiological concentration of the compound, suggesting for fructose 2,6-bisphosphate a key regulatory role in the control of the glycolytic flux. Incubation of human platelets with thrombin results in a parallel and rapid increase of fructose-2,6-bisphosphate levels and glycolytic flux, suggesting that the compound may also be involved in the enhancement of glycolysis elicited by the stimulating agent.

Blood Glucose↗
PubMed1986

Regulation of fructose 2,6-bisphosphate metabolism in human fibroblasts.

In the present work, the mechanism involved in the regulation of fructose 2,6-bisphosphate (fructose-2,6-P2) metabolism in human fibroblasts has been studied. Various agents like serum, insulin and adrenaline known to affect glycolysis have been investigated for their ability to influence fructose 2,6-P2 metabolism in confluent human fibroblasts. Serum appears to be the most potent activator of fructose-2,6-P2 levels and capable of inducing a marked increase in 6-phosphofructo-2-kinase (ATP: D-fructose-6-phosphate-2-phosphotransferase), EC 2.7.1. 105). To a lesser extent insulin has the same effects. The increase in enzyme activity elicited by serum and insulin does not require de novo protein synthesis since the process is insensitive to cycloheximide. Incubation of fibroblasts in the presence of adrenaline is responsible for a significant rise in fructose-2,6-P2 levels without affecting 6-phosphofructo-2-kinase. Similar experiments performed on glucose-starved or cytochalasin B-treated cells show that the effects elicited by all the agents are strictly dependent on glucose availability.

Cells, Cultured↗
PubMed1984

The effect of insulin on Fru-2,6-P2 levels in human fibroblasts.

We report that fructose 2,6-bisphosphate (Fru-2,6-P2) levels in quiescent human fibroblasts stimulated with insulin treatment increase in a time- and dose-dependent manner. The biochemical role of the sugar phosphate in the cellular response to the hormone which controls carbohydrate metabolism and acts as mitogenic factor is discussed.

Cells, Cultured↗