Interaction between glycosaminoglycans, platelets, and leukocytes.
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Amino Acid Sequence↗
Biomedical subjects
E Marchi
Publications and source records attributed to E Marchi.
Human pharmacokinetics of glycosaminoglycans using deuterium-labeled and unlabeled substances: evidence for oral absorption.
In the present study, the pharmacokinetics of extractive GAGs used as therapeutic agents have been studied after intravenous and oral administration on volunteers. The use of native or deuterium-labeled compounds, followed by HPLC/MS detection, allowed the quantitation of exogenous heparin and DS as major disaccharide fragments, obtained either by enzymatic or chemical depolymerization. In particular the high level of labeling reached in DS allowed its differentiation from structurally related endogenous species. The estimated plasmatic bioavailability was about 18% for DS. Notwithstanding the impossibility of evaluating the same parameters for heparin species, due to the interferences of endogenous GAGs, the results obtained provided clear evidence of oral availability of heparin and DS through detection and quantitation of structures specifically related to these GAGs. Due to the selectivity of the lyases used, the enzymatic degradation specifically allowed the detection of both DS and heparin species still retaining the original sulfation pattern. Additionally, the chemical degradation could detect the main metabolites of the drugs, consisting of partially to totally desulfated GAGs showing a more or less marked reduction in their molecular weight.
Administration, Oral↗
Organ glycosaminoglycan distribution after intravenous and oral administration in rats.
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Administration, Oral↗
High-dose methotrexate treatment and liver function in patients with osteosarcoma.
OBJECTIVES: To study the effects of short-term high-dose methotrexate therapy on liver function in patients with osteosarcoma. DESIGN: Open prospective study. SETTING: Department of Internal Medicine and Oncology, Istituto Ortopedico Rizzoli, Bologna, Italy. SUBJECTS: Fourteen patients with osteosarcoma, with no evidence of previous or actual liver disease at the time of diagnosis. INTERVENTIONS: All patients received a cumulative dose of 30-57 gm-2 of methotrexate within 6 months as neo-adjuvant chemotherapy (pre- and post-surgery). Each course of chemotherapy included methotrexate at a dose of 8-12 gm-2 and, in addition, adriamycin and cisplatinum. MAIN OUTCOME MEASURES: Galactose elimination capacity and antipyrine clearance were measured at baseline, after the first course of chemotherapy, at the end of the pre-operative period and at the end of chemotherapy. In each case they were carried out after transaminase levels had returned to normal. RESULTS: Galactose elimination capacity decreased from 2.45 (+/- 0.48) mM min-1 to 2.04 (+/- 0.60) mM min-1 after the five planned courses of chemotherapy (P = 0.013, Wilcoxon signed-rank test), without any change in routine liver function tests. No differences in antipyrine clearance and half-life were demonstrated (n = 8). CONCLUSIONS: The data are consistent with a decreased reserve capacity of the liver after short-term, high-dose methotrexate. Long-term survivors deserve monitoring of liver function for safer methotrexate use, in the light of progressive dosage increments to improve prognosis in neoplastic diseases.
Adolescent↗
Effects of glycosaminoglycans on platelet and leucocyte function: role of N-sulfation.
The effect of glycosaminoglycans (GAGs) such as sulodexide, low molecular mass dermatan sulfate, heparin and some derivatives with different degrees and types of sulfation was studied on cathepsin G- or thrombin-stimulated platelets and n-formyl-methionyl-leucyl-phenylalanine (fMLP)-stimulated polymorphonuclear leucocytes (PMNs). All GAGs (0.01-20 micrograms/mL) inhibited both platelet aggregation induced by cathepsin G and its catalytic activity. Thrombin-induced platelet aggregation in contrast was only prevented by heparin, sulodexide and dermatan (2-100 micrograms/mL). All GAGs, except 2-O,N-desulfated heparin, inhibited beta-glucuronidase and lysozyme release, as well as beta-glucuronidase activity and PMN superoxide production by the peptide fMLP. The efficacy of GAGs was clearly dependent on the degree and type of sulfation since dermatan and N-desulfated heparins were comparatively less effective. The observation that heparin and other GAGs inhibit platelet activation induced by the PMN protease cathepsin G may help determine whether mechanisms of action other than anticoagulation are critical in the antithrombotic activity of heparin and related compounds.
Blood Platelets↗
Antithrombotic activity of Desmin 370. Comparison with a high molecular weight dermatan sulfate.
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Animals↗
Effect of the desulfation of heparin on its anticoagulant and anti-proliferative activity.
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Acetylation↗
Therapeutic effect of a low molecular weight dermatan sulphate (Desmin 370) in rat venous thrombosis--evidence for an anticoagulant-independent mechanism.
We evaluated the capacity of a low molecular weight dermatan sulphate (D370) to prevent thrombus formation and to induce a reduction of a stabilized thrombus in a rat venous thrombosis model. Injection of D370, 10 min before induction of venous stasis (prevention model), prevented thrombus formation in a dose-dependent way (ED50: 2.3 mg/kg). When given to rats 6 h after induction of venous stasis (therapeutic model), D370 caused a time- and dose-dependent reduction in thrombus size (60% to 70% reduction 2 h after injection of 10 mg/kg). At comparable antithrombotic dosages (i.e. minimum dose giving complete inhibition of thrombus formation), heparin (0.5 mg/kg) only caused 40% reduction of a preformed thrombus while hirudin (1 mg/kg) was virtually ineffective (less than 10% reduction in weight). All three compounds inhibited 125I-fibrin(ogen) deposition on 6-h aged thrombi by more than 85%, suggesting that D370 and, to a lesser extent, heparin reduce thrombus size via mechanisms other than inhibition of thrombus accretion. The involvement of a fibrinolysis-mediated mechanism in the D370-induced effect is suggested by the following. EACA (1 g/kg), when given to thrombus-bearing control animals, did not influence thrombus weight. However, when administered before D370 treatment, it prevented the expected reduction in thrombus weight by more than 80%, without influencing the effect of D370 on 125I-fibrin(ogen) accumulation onto preexisting thrombi. D370 injection caused neither an enhancement of fibrinolytic activity nor a reduction of PAI in plasma. In vitro, D370 (200 microns/ml) was unable to potentiate the spontaneous or PA-induced lysis of 125I-fibrinogen labelled blood, plasma, or purified fibrin clots.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
Defective methionine metabolism in cirrhosis: relation to severity of liver disease.
A block in the transsulfuration pathway has previously been suggested in cirrhosis on the basis of increased fasting methionine concentrations, decreased methionine elimination and low levels of methionine end products. To date, methionine elimination has never been studied under controlled steady-state conditions, and the relation of the severity of liver disease to impaired methionine metabolism has not been clarified. We measured methionine plasma clearance in 6 control subjects and in 12 patients with cirrhosis during steady-state conditions obtained by a primed, continuous methionine infusion. In the presence of high-normal fasting methionine concentrations (range = 14 to 69 mumol.L-1 in controls and 26 to 151 mumol.L-1 in cirrhotic patients), methionine plasma clearance was reduced in cirrhotic patients (2.25 +/- S.D. 0.43 ml.sec-1 vs. 2.86 +/- S.D. 0.43 ml.sec-1 in controls; p less than 0.05), whereas methionine half-life was increased (282 +/- 90 min vs. 187 +/- 25 min in controls; p less than 0.05). Fasting methionine significantly correlated with methionine clearance. The infused methionine was not degraded to urea to any significant extent in cirrhotic patients, whereas a threefold increase in urinary urea nitrogen excretion rate was observed in controls. Similarly, taurine concentrations significantly increased both in plasma and in the urine in controls but not in cirrhotic patients. In cirrhotic patients methionine plasma clearance significantly correlated with galactose elimination capacity (r = 0.818) and with the Child-Pugh score (rs = -0.795). The study supports a major role of impaired liver cell function in the reduced metabolism of methionine and decreased formation of methionine end products that occur in cirrhosis.(ABSTRACT TRUNCATED AT 250 WORDS)
Adult↗
Antithrombotic and thrombolytic activity of sulodexide in rats.
We evaluated the ability of sulodexide, an extracted glycosaminoglycan, to prevent thrombus formation and to reduce a stabilized thrombus in a rat venous thrombosis model (vena cava ligature). Injection of sulodexide 10 min before induction of venous stasis, prevented thrombus formation in a dose-dependent manner (median effective dose 0.55 mg/kg). When given to rats with 6-h-old thrombi, sulodexide caused a marked reduction in thrombus size which reached 70% after 2 h with the highest dose tested (2 mg/kg). The effect of sulodexide on established thrombi appears to be due, at least in part, to a fibrinolysis-mediated mechanism, since it was significantly inhibited by epsilon-aminocaproic acid, a well-known antifibrinolytic drug. Treatment with sulodexide did not noticeably affect plasma levels of plasminogen activator and its specific inhibitor. We also showed that fluorescein-labelled sulodexide, when given to animals with 6-h-old thrombi, was present within the thrombi harvested 2 h later, but was then absent from blood. The fluorescence was mainly located in areas filled with amorphous material, that was identified as fibrin by staining with phosphotungstic acid-hematoxylin. No fluorescein-labelled material could be detected in rats treated with fluorescein alone. These findings indicate that, besides preventing venous thrombus formation, sulodexide is able to promote thrombus dissolution by a mechanism that is partly related to local fibrinolysis stimulation.
Animals↗
Effect of S-adenosyl-L-methionine administration on plasma levels of sulphur-containing amino acids in patients with liver cirrhosis.
An impaired transsulphuration pathway has been described in patients with liver cirrhosis. The defective metabolic step is located at the site of S-adenosyl-L-methionine (SAMe) formation from methionine. In a placebo-controlled study, we measured the fasting plasma levels of sulphur-containing amino-acids in cirrhotic patients with hypermethioninemia and/or severe hepatocellular failure, during treatment with exogenous SAMe (1.2 g i.v. for 3 days, followed by an oral administration of 1.2 g for an additional 30 days; 8 cases) or saline and placebo tablets (8 cases). All subjects were initially treated during hospital admission, and completed the oral study as out-patients. In patients given SAMe, long-term treatment doubled the plasma concentration of the secondary sulphur-containing amino acid cystine (from 36 [SD 18] mumol.l(-1) to 67 [36]) and taurine (from 42 [13] mumol.l(-1) to 89 [33]), which were on average low-normal at baseline, without any change in the concentration of methionine, of neutral amino acids, and of polyamines. No changes in plasma amino acids were observed in the control group. Two-factor, repeated measures of analysis of variance revealed differences between SAMe- and placebo-treated patients, consistent with an effect of long-term SAMe administration on secondary sulphur-containing amino acids. The potential therapeutic advantage of such treatment remains to be determined in clinical studies.
Journal Article↗
Glycosaminoglycans prevent morphological renal alterations and albuminuria in diabetic rats.
Abnormal glycosaminoglycan metabolism is involved in the onset of anatomo-functional derangements in diabetic nephropathy, and determines the loss of glomerular basement membrane anionic charges leading to albuminuria. Glycosaminoglycan administration was shown to increase the negative electrical potential of the vessel wall, inhibit mesangial cell proliferation, which is an anatomical hallmark of diabetic nephropathy, and slow down the progression to uremia in subtotally nephrectomized rats, a model that shares some pathogenetic key events with diabetic nephropathy. Based on these considerations, we verified the effect of exogenous glycosaminoglycans on renal involvement in streptozotocin diabetic rats. Long-term administration of two glycosaminoglycans (low-molecular weight heparin and dermatan sulphate) prevented glomerular basement membrane thickening, glomerular anionic charge reduction, as well as the onset of albuminuria without affecting glomerular filtration rate and metabolic control of the disease. Our data demonstrate that the long-term administration of glycosaminoglycans has a favorable effect on morphological and functional renal abnormalities in diabetic rats.
Albuminuria↗
Effect of physical exercise on one-sample antipyrine clearance.
Moderate physical exercise for a few hours is not expected to reduce the hepatic elimination of drugs exhibiting capacity-limited metabolism (low-clearance drugs such as antipyrine). However, previous studies have shown that antipyrine half-life, measured by the multiple-sampling technique, is increased by exercise. A simplified one-sample procedure for antipyrine clearance determination is increasingly being used as a liver function test. The effects of exercise on this measurement have never been evaluated. We measured antipyrine clearance, using the one-sample, simplified procedure in a group of 50 young Italian army soldiers, while at rest and during a 6 hour march in the mountains (extra energy expenditure: 7.43 kjoule per min). Mean antipyrine clearance was on average 46.6 (SD 10.2) ml/min (range 30.5-65.4) while resting, and 46.2 (10.5) (range 25.5-64.8) while exercising (not different). No specific advice regarding physical exercise is needed whenever liver function is measured in outpatients by the one-sample, simplified antipyrine clearance test.
Adult↗
Protein C deficiency in insulin-dependent diabetes: a hyperglycemia-related phenomenon.
In 30 insulin-dependent diabetic patients protein C (PC) antigen and PC activity were significantly lower than those of matched control healthy subjects. An inverse correlation between fasting plasma glucose and both PC concentration and activity was present in diabetics, while a direct correlation between PC concentration and PC activity was observed. Induced hyperglycemia in diabetic and normal subjects was able to decrease both PC antigen levels and PC activity, and heparin reversed in part this effect. In diabetic patients euglycemia obtained by insulin infusion restored to normal the depressed PC levels. Heparin did not alter both the basal PC concentration and activity in healthy controls. These data stress the major role of hyperglycemia in determining PC decrease in diabetics, and suggest that PC reduction is probably associated to hyperglycemia-enhanced thrombin formation.
Adult↗
Evidence for a hyperglycaemia-dependent decrease of antithrombin III-thrombin complex formation in humans.
In the presence of increased levels of fibrinopeptide A, decreased antithrombin III biological activity, and thrombin-antithrombin III complex levels are seen in diabetic patients. Induced-hyperglycaemia in diabetic and normal subjects decreased antithrombin III activity and thrombin-antithrombin III levels, and increased fibrinopeptide A plasma levels, while antithrombin III concentration did not change; heparin was shown to reduced these phenomena. In diabetic patients, euglycaemia induced by insulin infusion restored antithrombin III activity, thrombin-antithrombin III complex and fibrinopeptide A concentrations; heparin administration had the same effects. These data stress the role of a hyperglycaemia-dependent decrease of antithrombin III activity in precipitating thrombin hyperactivity in diabetes mellitus.
Adult↗
Non-enzymatic glycation reduces heparin cofactor II anti-thrombin activity.
The effects of non-enzymatic glycation on heparin cofactor II activity, at glucose concentrations which might be expected in physiological or diabetic conditions have been evaluated in this study. Radiolabelled glucose incorporation was associated with a loss of heparin cofactor anti-thrombin activity. The heparin cofactor heparin and dermatan sulfate-dependent inhibition of thrombin was significantly reduced, showing a remarkable decrease of the maximum second order rate constant. This study shows that heparin cofactor can be glycated at glucose concentrations found in the blood, and that this phenomenon produces a loss of heparin cofactor-antithrombin activity. These data suggest, furthermore, a possible link between heparin cofactor glycation and the pathogenesis of thrombosis in diabetes mellitus.
Antithrombins↗
The role of hyperglycaemia-induced alterations of antithrombin III and factor X activation in the thrombin hyperactivity of diabetes mellitus.
Factor X concentration and factor X activation, antithrombin III anti-Xa activity and plasma concentration, and fibrinopeptide A were measured in 20 diabetic patients and 20 normal subjects. Although factor X activation (81.3 +/- 2.2 vs 97.3 +/- 2.1%, p less than 0.01; mean +/- SE) and antithrombin III activity (76.5 +/- 2.2 vs 96.3 +/- 1.8%, p less than 0.01) were reduced in the diabetic patients, fibrinopeptide A concentration was increased (3.7 +/- 0.4 vs 1.7 +/- 0.2 ng ml-1, p less than 0.01). The ratio of factor X activation to antithrombin III anti-factor Xa activity was increased in the diabetic patients (1.10 +/- 0.01 vs 1.01 +/- 0.02, p less than 0.01). Induced hyperglycaemia was able to mimic all these abnormalities, without changing factor X or antithrombin III concentration. The results suggest that in vivo hyperglycaemia produces a decrease of factor X activation, but at the same time increases fibrinopeptide A formation due to a greater decrease of antithrombin III anti-Xa activity.
Adult↗
Analysis of the deterioration rates of liver function in cirrhosis, based on galactose elimination capacity.
The prognosis of cirrhotic patients may depend on their liver function, but very few data are available to predict life expectancy in individual subjects on the basis of their liver function tests. The yearly changes in liver function, based on galactose elimination capacity (GEC), were retrospectively analyzed in 76 cirrhotic patients. The first GEC measurement had always been performed at the time of diagnosis. From that time on, mean GEC changes (in mmol/min per year) were +0.13 [SD 0.60] in the 1st year (range: +1.42/-1.35), and -0.03 [0.30] in the 2nd year (P = ns). Only after 36 months could a significant deterioration in liver function be demonstrated, but GEC changes still ranged from +0.14 to -0.35. The trend in liver function was similar in patients with alcoholic and non-alcoholic cirrhosis, but in alcoholics a favourable effect of abstinence was proved. In individual subjects, 2 consecutive GEC measurements, at least 6 months apart, failed to predict the following GEC values. The coefficients of determination between expected and measured GEC or delta GEC were 0.13 and 0.36, respectively (n = 58). When forecasting was limited to 2 years (n = 38), still only 31% and 55% of GEC values and delta GEC variance was predictable on the basis of preceding GEC values. The study shows that no definite trends in liver function deterioration rates can be observed in cirrhosis. This limits the usefulness of liver function tests in predicting prognosis in cirrhotic patients.
Adult↗