149 research outputs found
β-trace protein is highly removed during haemodialysis with high-flux and super high-flux membranes
Background: Serum β-trace protein (βTP, MW 23-29 kDa) is a marker of GFR impairment in renal patients. Recent papers propose to predict residual renal function (RRF) in maintenance haemodialysis (MHD) patients from serum concentrations of βTP and other small proteins, avoiding the collection of urine. Few data are available on the removal of βTP in patients treated with dialysis membranes with different flux characteristics. The aim of this study was to evaluate the effects of haemodialysis with low-flux, high-flux and super high-flux membranes on serum concentrations of ßTP in MHD patients with null RRF. Methods: Serum ßTP concentrations were measured before and after the first dialysis of the week in 51 MDH patients treated by low-flux (n = 24), high-flux (n = 17), or super high-flux (n = 10) membranes. The removal of β2-microglobulin (β2M, MW 11.8), cystatin C (Cys, MW 13.3), urea and creatinine was also analyzed. Results: Low-flux membranes did not remove βTP, β2M and Cys whose concentration increased at the end of dialysis. High-flux membrane removed more efficiently β2M and Cys than ßTP. Super high-flux membrane had the highest efficiency to remove ßTP: mean reduction ratio (RR) 53.4%, similar to β2M (59.5%), and Cys (62.0%). Conclusions: In conclusion, the plasma clearance of small proteins and particularly of βTP is dependent from the permeability of the dialysis membranes Therefore, the reliability of the formulas proposed to predict RRF from serum βTP and other LMWP may be affected by the different permeability of the dialysis membranes
The potential roles of gamma-glutamyltransferase activity in the progression of atherosclerosis and cardiovascular diseases.
The oxidation of low density lipoproteins (LDL) is regarded as a critical factor in the pathogenesis of atherosclerosis,
especially the initial steps of the disease. In addition, other oxidative events have been shown to participate in
the progression of atherosclerosis and precipitation of cardiovascular events, through modulation of important components
of lesions of the vessel wall (smooth muscle cell proliferation, protease/antiprotease balance, endothelial functions).
Our recent studies have provided evidence that the enzyme gamma-glutamyltransferase (GGT), normally found in serum,
is often accumulated within the plaque environment in substantial amounts, and that this activity is a potential source of a
variety of prooxidant species. Concurrently, epidemiological research has conclusively documented that the serum levels
of GGT are an independent factor in prognosis of myocardial infarction and stroke in atherosclerotic patients. Several
signs suggest that the GGT appearing in plaque tissue may originate from the serum enzyme, which in facts associates
with the circulating lipoprotein fractions. Thus, data seem to point out that pathogenesis of atherosclerosis – and in particular
of the events leading to progression of the disease and acute cardiovascular events – might include an as yet unexplored
pathway, based on the prooxidant effects of gamma-glutamyltransferase accumulating as a result of LDL entry in
the vessel wall
Plasma membrane gamma-glutamyltransferase activity facilitates the uptake of vitamin C in melanoma cells.
Adequate cellular transport of ascorbic acid (AA) and its oxidation product dehydroascorbate (DHA) is
assured through specific carriers. It was shown that vitamin C is taken up as DHA by most cell types, including cancer
cells, via the facilitative GLUT transporters. Thus, AA oxidation to DHA can be considered a mechanism favoring
vitamin C uptake and intracellular accumulation. We have investigated whether such an AA-oxidizing action might be
provided by plasma membrane g-glutamyltransferase (GGT), previously shown to function as an autocrine source of
prooxidants. The process was studied using two distinct human metastatic melanoma clones. It was observed that the
Me665/2/60 clone, expressing high levels of membrane GGT activity, was capable of effecting the oxidation of
extracellular AA, accompanied by a marked increase of intracellular AA levels. The phenomenon was not observed with
Me665/2/21 cells, possessing only traces of membrane GGT. On the other hand, AA oxidation and stimulation of cellular
uptake were indeed observed after transfection of 2/21 cells with cDNA coding for GGT. The mechanism of GGTmediated
AA oxidation was investigated in acellular systems, including GGT and its substrate glutathione. The process
was observed in the presence of redox-active chelated iron(II) and of transferrin or ferritin, i.e., two physiological iron
sources. Thus, membrane GGT activity—often expressed at high levels in human malignancies—can oxidize
extracellular AA and promote its uptake efficiently
Discrepancy between FLC assays: Only a problem of quantification?
Immunoglobulin light chains not associated with heavy chains (free light chains, FLC) are found in serum. A growing clinical importance has been assigned to the quantification of the kappa and lambda FLC in serum in the management of plasma cell dyscrasias. At present, automated immunoassays are the only available techniques allowing quantitative determination of serum FLC.
Unfortunately, the two reagents available for FLC assay, provide sometimes divergent results. It has been proposed that the different results, unpredictably affecting individual serum samples, are due the different reactivity of reagents against FLC oligomers that are known to be present to a variable extent in serum, especially when lambda FLC are involved. We report a case where we demonstrated that the two reagents recognized differently FLC monomer and dimers
Development of a normothermic extracorporeal liver perfusion system toward improving viability and function of human extended criteria donor livers
Letter to the edito
YORP-Yarkowski evolution of asteroid families: the effects of collisions
The depletion of objects in the central part of an asteroid family,
which can be observed in the absolute magnitude vs. semimajor axis,
can be explained in terms of a coupling of the YORP and Yarkovsky
effects (Paolicchi and Knezevic, Icarus, 2016). In particular, it can
be ascribed to the obliquity evolution caused by YORP and on how it
influeces the Yarkovsky drift.With this work we intend to improve the
modeling of YORP-Yarkovsky evolution of asteroid families exploiting a
model which tracks the evolution of the spin vector of small
asteroids, including also the effects of collisions on the YORP
induced obliquity evolution. This allows a better modeling of the
asteroid spin evolution.In these preliminary steps, we will first
consider a few model families simulating their time evolution in the
magnitude vs. semimajor axis plots. The obtained results will be then
compared with observed families to determine and tune the intensity of
the effect
Association between plasma gamma-glutamyltransferase fractions and metabolic syndrome among hypertensive patients
Among the risk factors associated to metabolic syndrome (MetS), hypertension shows the highest prevalence in Italy. We investigated the relationship between the newly identified serum ĂŽÂł-glutamyltransferase (GGT) fractions, b-s-m-f-GGT, and risk factors associated to MetS in hypertensive patients. A total of ninety-five consecutive hypertensive patients were enrolled. GGT fractions were analysed by gel-filtration chromatography, and hepatic steatosis was evaluated by ultrasound. MetS was diagnosed in 36% of patients. Considering the whole group, b-And f-GGT showed the highest positive correlation with BMI, glucose, triglycerides and insulin, and the highest negative correlation with HDL cholesterol. While both serum triglycerides and insulin were independently associated with b-GGT levels, only triglycerides were independently associated with f-GGT. The values of b-GGT activity increased with steatosis grade (g0 = 1.19; g2 = 3.29; ratio g2/g0 = 2.75, p < 0.0001 linear trend). Patients with MetS showed higher levels of b-GGT, m-GGT and f-GGT [median (25th-75th) U/L: 3.19 (1.50-6.59); 0.55 (0.26-0.81); 10.3 (9.1-13.6); respectively] as compared to subjects presenting with one or two MetS criteria [1.75 (0.95-2.85), p < 0.001; 0.33 (0.19-0.60), p < 0.05; 8.8 (7.0-10.6), p < 0.001]. Our data point to a potential role for b-And f-GGT fractions in identifying MetS patients among hypertensive subjects, thus providing a minimally invasive blood-based tool for MetS diagnosis
Circulating gamma-glutamyltransferase fractions in cirrhosis.
Background: Four GGT fractions (b-, m-, s-, and f-GGT) have been identified in human plasma and their concentrations and ratios vary in different pathological conditions.
Aim: To assess the behavior of fractional GGT in cirrhotic patients evaluated for liver transplantation.
Methods: This was a single-center, cross-sectional study; GGT fractions were determined by gel-filtration chromatography.
Results: 264 cirrhotic patients (215 males; median age 54.5 years) were included and compared against a group of 200 healthy individuals (100 males; median age 41.5). Median (25th-75th percentile) total and fractional GGT were higher in cirrhotics, with s-GGT showing the greatest increase [36.6 U/L (21.0-81.4) vs. 5.6 U/L (3.2-10.2), (p<0.0001)], while the median b-GGT/s-GGT ratio was lower in cirrhotics than in healthy controls [0.06 (0.04-0.10)] vs. 0.28 (0.20-0.40), p<0.0001]. The ratio showed higher diagnostic accuracy (ROC-AUC, 95% CI: 0.951, 0.927-0.969) then either s-GGT (0.924, 0.897-0.947; p<0.05) or total GGT (0.900, 0.869-0.925; p<0.001). The diagnostic accuracy of the ratio was maintained (0.940, 0.907-0.963) in cirrhotic patients (n=113) with total GGT values within the reference range. The s-GGT fraction consisted of two components, with one (s2-GGT) showing a significant positive correlation with serum AST, ALT, LDH, ALP and bilirubin, and negative with albumin. The b-GGT fraction showed a positive correlation with albumin, fibrinogen, and platelet counts, and negative with INR, bilirubin and LDH.
Conclusions: The ratio performs as a sensitive biomarker of the liver parenchymal rearrangement, irrespective of etiology of cirrhosis and presence of hepatocellular carcinoma, even in patients with total GGT values within the reference range
A High Performance Gel Filtration Chromatography Method for gamma-Glutamyltransferase Fraction Analysis
The clinical relevance of serum c-glutamyltransferase (GGT) activity, in areas other than hepatic function, has recently been increased
by several epidemiological associations. Still, GGT remains a nonspecific test because of the influence of various pathophysiological factors.
We devised a procedure based on gel filtration chromatography, followed by postcolumn injection of fluorescent GGT substrate (cglutamyl-
7-amido-4-methylcoumarin), permitting the quantification of GGT fractions in serum or plasma. Plasma GGT molecular
weight distribution was analyzed in healthy volunteers (20 males; mean ± SD age 38 ± 10 years; 20 females; age 44 ± 13; total GGT
21 ± 11 for males vs 13 ± 7 for females; P < 0.01). The method is highly sensitive (determination limit: 0.5 U GGT/L), with a linear
dynamic range between 0.5 and 150 U/L for each fraction. Four GGT fractions of different molecular weight were detected in all subjects
of both genders: b-GGT, m-GGT, s-GGT (likely lipoprotein-bound, molecular masses >2000, 940, and 140 kDa, respectively), and a free
fraction (f-GGT, 70 kDa). f-GGT and s-GGT were the main fractions in subjects with lower and higher total GGT activity, respectively.
Higher total GGT activity in males is related mainly to f-GGT (P < 0.01). GGT fraction analysis may increase the sensitivity and specificity
of the GGT activity test
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