Evaluation of an immunoassay (Abbott-IMX Analyzer) allowing routine determination of sirolimus: comparison with LC-MS method

BACKGROUND

The use of the immunosuppressive agent sirolimus is increasing in renal transplantation but its monitoring often requires high-performance liquid chromatography (HPLC) with ultra-violet (UV) or tandem mass spectrometric (MS-MS) detection. The aim of this study was to compare a new microparticle enzyme immunoassay (MEIA, Microparticle Enzyme Immunoassay) on IMx Abbott Analyser with a liquid chromatography-mass spectometry (LC-MS) method.

METHOD

The accuracy of immunoassay analytical performance including within run and between run imprecision and linearity was tested. For comparison studies, sirolimus level was then determined with the two methods on 98 samples from 52 transplant patients.

RESULTS

Total intra-assay and inter-assay variation coefficients were below 10% at the three levels tested, and the coefficient of linearity was r = 0.99. The values obtained were highly correlated with the LC-MS method (MEIA = 1.02LC-MS + 0.91; r(2) = 0.87). As a result, the immunoassay showed good performance, and clinical sample measurements were not affected by the method. The MEIA may be a useful alternative for routine monitoring of sirolimus.

New onset dyslipidemia after renal transplantation: is there a difference between tacrolimus and cyclosporine?

Lipid abnormalities including increased total cholesterol (TC), triglycerides (TG) and low density lipoprotein cholesterol (LDL-C) have been frequently reported in renal transplantation and could be involved in the high frequency of cardiovascular diseases in this population.

PATIENTS AND METHODS

Two hundred ninety-five patients were transplanted between January 1995 and October 2000 in our center. Two hundred two patients were included in this study. Seventy-six patients received tacrolimus (Tac), and 126 patients cyclosporine (CsA). Lipid parameters were assessed the day of transplantation and 1 year posttransplantation.

RESULTS

Serum lipids were similar between the two groups at D0. At M12, TC and LDL-C were significantly higher in the CsA group (6.14 +/- 1.37 vs 5.28 +/- 1.32 mmol/L; P < .05 and 3.98 +/- 1.05 vs 3.26 +/- 1.03 mmol/L; P < .05 CsA vs Tac, respectively). TG were comparable in both groups (1.86 +/- 1.07 vs 1.62 +/- 0.92 mmol/L; P = .55; CsA vs Tac). Incidence of de novo hypercholesterolemia was significantly higher in the CsA group (28 vs 8%) whereas incidence of hyperTG was similar in both groups. Prevalence of LDL-C was significantly higher in the CsA group (65% vs 31%; P < .001), whereas there was no difference in high density lipoprotein (HDL)-C levels.

DISCUSSION

Mean serum lipid levels and incidence and prevalence of hyperTC, especially LDL-C, was significantly higher in patients receiving CsA when compared with Tac. TG and HDL-C levels were similar. Although the study was retrospective, our results confirm that CsA increases lipid levels, whereas Tac does not.

CONCLUSION

Lipid disorders are frequently observed in renal transplant recipients. CsA, but not Tac, significantly increases incidence and prevalence of high TC and LDL-C.

Renal transplantation decreases osteoprotegerin levels

Vascular calcifications are an important risk factor for cardiovascular mortality and morbidity in patients with chronic renal failure. Osteoprotegerin, a soluble decoy receptor for receptor activator NFkB ligand, has emerged as an independent predictive factor of atherosclerosis and vascular calcification in hemodialysis patients. Sparse data are available on the evolution of osteoprotegerin after renal transplantation. The aim of this study was to follow the evolution of serum osteoprotegerin levels and biochemical risk factors after renal transplantation. Forty patients were included. Blood samples for analysis were collected before and 3 months after renal transplantation. Besides the expected diminution in calcium-phosphate product, we have shown an early normalization of osteoprotegerin (10.05 +/- 4.77 pmol/L to 4.59 +/- 2.26 pmol/L). This study demonstrates that kidney transplantation improves this risk factor for vascular calcifications. However, these preliminary results should be confirmed and extended by the follow-up of vascular calcifications in the long term.

Small dense low-density lipoprotein in renal transplant recipients: a potential target for prevention of cardiovascular complications?

BACKGROUND

Immunosuppressive therapy is frequently associated with dyslipidemia, which is involved in cardiovascular morbidity and mortality in transplant patients. Beyond classical factors, such as low-density lipoprotein (LDL) cholesterol (LDL-C), qualitative abnormalities of lipoproteins, such as presence of the atherogenic factor, small dense LDL, may be of interest for a cardiovascular risk assessment. This study was designed to explore LDL size in renal transplant recipients in relation to quantitative lipid parameters and apolipoprotein (apo) CIII polymorphism.

METHODS

Total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), LDL-C, apoA1, apoB, apoCIII, and LDL size were measured in 62 patients of mean age 45 +/- 13 years including 71% men at 2 +/- 0.5 years after renal transplantation. Thirty-two patients received cyclosporine (CsA), while 30 received tacrolimus (FK). ApoCIII Sstl genotype was determined by restriction fragment length polymorphism.

RESULTS

The CsA group exhibited higher TC (P = .001), LDL-C (P = .004), non-HDL-C (P = .009), HDL-C (P = .03), apoB (P = .008), and apoCIII (P = .002) levels than the FK group. However, LDL-C (CsA: 3.7 +/- 1.2, FK: 3.0 +/- 0.6 mmol/L) and triglyceride levels (CsA: 1.55 mmol/L, FK: 1.37 mmol/L) were near the normal range in both groups. Allelic frequency of the sparse A2 allele associated with hypertriglyceridemia was 6%, similar to the general population. LDL size, which was comparable in the CsA and FK groups (25.87 +/- 0.89 vs 25.75 +/- 0.62 nm, respectively), inversely correlated with TG/HDL ratio (P = 10(-4)). Prevalence of small dense LDL (defined as <25.5 nm) was 26% in the CsA group and 33% in the FK group.

CONCLUSION

After LDL-C goal has been achieved, LDL size modulation may be taken into account in order to prevent cardiovascular complications.

Beta2-microglobulin, a uremic toxin with a double meaning

beta(2)M is a strong and independent indicator of hemodialysis patient outcomes and an excellent surrogate for middle molecules, and deserves to be routinely monitored and incorporated into dialysis adequacy targets. beta(2)M has a double meaning, reflecting both dialysis efficacy in terms of solute mass transfer and patient bioactivity. The work of Ward et al. in this issue warrants a study to test the hypothesis that long daily hemodiafiltration treatment would be the optimal renal replacement modality to improve dialysis patient outcomes.

Evaluation of a capillary zone electrophoresis system versus a conventional agarose gel system for routine serum protein separation and monoclonal component typing

Capillary zone electrophoresis of serum proteins is increasingly gaining impact in clinical laboratories. During 2003, we compared the fully automated capillary electrophoresis (CE) system from Beckman (Paragon CZE 2000) with the method agarose gel electrophoresis Sebia (Hydrasis-Hyris, AGE). This new study focused on the evaluation of analytical performance and a comparison including 115 fresh routine samples (group A) and a series of 97 frozen pathologic sera with suspicion of monoclonal protein (group B). Coefficients of variation (CVs %) for the five classical protein fractions have been reported to be consistenly < 9% in within-run and < 10% in between-run imprecision studies with the Paragon 2000 system. The results of the comparison study (group A) demonstrated a good correlation between the CE system and AGE, except for beta-globulin (r = 0.65). Among the 97 pathologic serum samples (group B), there were 90 in which we detected a monoclonal protein by immunofixation (IF) (immunosubtraction (IS) was not used). AGE and Paragon 2000 failed to detect 7 and 12 monoclonal proteins, respectively, leading to a concordance to 92% for AGE and 87% for Paragon 2000 for identifying electrophoretic abnormalities in this group. Beta-globulin abnormalities and M paraprotein were well detected with Paragon 2000. Only 81% (21 vs 26) of the gammopathies were immunotyped with IS by two readers blinded to the IF immunotype. The Paragon 2000 is a reliable alternative to conventional agarose gel electrophoresis combining the advantages of full automation (rapidity, ease of use and cost) with high analytical performance. Qualified interpretation of results requires an adaptation period which could further improve concordance between the methods. Recently, this CE system has been improved by the manufacturer (Beckman) concerning the migration buffer and detection of beta-globulin abnormalities.

High Prevalence of Small Dense LDL as an Underestimated Component of Heart Transplantation–Induced Dyslipidemia: Potential Role in Graft Coronary Vasculopathy?

Heart transplantation-induced dyslipidemia is a recognized risk factor for cardiac allograft vasculopathy that affects survival prognosis. Beyond increased lipids, low-density lipoprotein (LDL) size and systemic factors, including glucose intolerance, oxidative stress, and inflammation, must be taken into account as components of the atherosclerotic risk. The aim of this study was to explore the atherogenic profile of heart transplant recipients (HTR) by assessing lipid parameters, glycemia, oxidative stress status, and inflammation in 59 transplant patients (follow-up of 6 +/- 3 years) compared to 20 healthy volunteers. Classical hypercholesterolemia and hypertriglyceridemia were observed in HTR compared to controls, associated with increased apoCIII levels (0.13 +/- 0.6 vs 0.07 +/- 0.03 g/L, P < .01). Mean LDL size was reduced in HTR compared to controls (25.22 +/- 0.72 vs 26.06 +/- 0.54 nm, P < .001) with an abnormally high prevalence (69% vs 0%, P < .001) of small dense LDL (<25.5 nm). Hyperglycemia (7.3 +/- 3 vs 5.4 +/- 0.8 mmol/L, P < .05) and inflammation (high-sensitive CRP: 3.1 +/- 3 vs 1.6 +/- 0.9 mg/L, P < .001) were evidenced in HTR since no difference in oxidative stress parameters was observed. In conclusion, a high prevalence of small dense LDL is an important component of posttransplantation dyslipidemia.

[Study of lipoprotein (a) phenotypes in Ivorian subject]

The objective of this study was to identify the apo (a) phenotypes and to find a correlation between apo (a) isoform size and Lp (a) plasma level in Ivorian subjects. This study involved 30 healthy subjects (11 females and 19 males) aged of 35 +/- 2 years. Lp (a) plasma levels have been determined by technical ELISA, while phenotypes of apo (a) have been identified by agarose high resolution electrophoresis followed by Western blot. The Lp (a) plasma level in our population was 329 +/- 291 mg/l and 30% of our population's Lp (a) plasma levels were above 300 mg/l. 70% of our subjects have homozygous phenotype and 30% have heterozygous phenotype. Three apo (a) isoforms (S2, S3, S4) have been identified in homozygous subjects whereas four apo (a) isoforms (B, S2, S3, S4) have been detected in heterozygous subjects. Their sizes varied from 13 to 33 kringle 4.77% of our subjects had apo (a) isoforms whose sizes were above 22 kringle 4. No correlation has been observed between the size of apo (a) isoforms and the Lp (a) plasma level in homozygous subjects. Our results highlight apo (a) polymorphism in Ivorians. Homozygous phenotypes and large size apo (a) isoforms predominate in this population.

Changes in osteoprotegerin/RANKL system, bone mineral density, and bone biochemicals markers in patients with recent spinal cord injury

This study analyzed the temporal and regional variations in bone loss and explored bone cell activities via biochemical markers during an extended follow-up in patients with spinal cord injury (SCI). In parallel, the possible role of the osteoprotegerin (OPG)/RANKL system in disuse osteoporosis was investigated. Seven male patients with acute and complete SCI (31.3 +/- 9.5 years) and 12 able-bodied (AB) men (26.9 +/- 4.2 years) participated in the study. Measurements were performed 16, 24, 36, 48, and 71 weeks after injury. At week 16, marked calcium homeostasis disturbance and a concomitant increase in bone resorption markers were observed, reflecting an intense bone degradation process. Resorption activity decreased continuously with time. Contrasting with the great rise in the resorption markers, the bone formation markers showed little variation. During the period of investigation, a loss in bone mineral density (BMD) was demonstrated for the total body (-4.3%), pelvis (-15.7%) and lower limbs (-15.2%), whereas BMD did not change at the lumbar spine, upper limbs, or skull. At all stages, SCI patients had lower serum RANKL levels and higher serum OPG levels than did AB controls, but no significant variation with time was observed for either cytokine. These findings suggest that bone resorption persisted long after SCI and specifically affected BMD at sublesional sites. The marked modification of serum OPG/RANKL levels in SCI patients suggests that this system is affected, in disuse osteoporosis. However, the precise biologic role of the OPG/RANKL system in the bone tissue of SCI patients has yet to be determined.

Dichotomous responses of inter and postprandial hyperglycaemia to short-term calorie restriction in patients with type 2 diabetes

BACKGROUND

In type 2 diabetes the effects of short-term calorie restrictions on glycaemia are usually judged on fasting plasma glucose. As fasting duration rarely exceeds 2-3 h, we determined the effects of calorie restriction over different daytime periods using a continuous glucose monitoring system (CGMS) in noninsulin-using patients with type 2 diabetes.

DESIGN

Fourteen poorly controlled (mean HbA1c = 9.3%) overweight or obese patients (mean body mass index = 30.1 +/- 0.7 kg m(-2)) with type 2 diabetes were investigated twice with a CGMS, at baseline and at the end of a 18-day calorie-restricted diet (1490 kcal day(-1)). Areas under curves (AUCs) of 24-h glucose monitoring were measured and divided into postprandial and interprandial AUCs according to meal times.

RESULTS

Areas under curves of 24-h glucose monitoring were significantly decreased after dieting: -37%, P = 0.0047. Both post and interprandial AUCs were significantly diminished (-26%, P = 0.0186 and -48%, P = 0.0037, respectively), but changes in interprandial AUCs were more marked than changes in postprandial AUCs (P = 0.0060). Nycthemeral peaks of glucose were observed at mid-morning times and were not significantly different before (242 +/- 15 mg dL(-1)) and after dieting (227 +/- 16 mg dL(-1)).

CONCLUSIONS

Short-term calorie restriction in overweight or obese patients with type 2 diabetes resulted in dichotomous responses between interprandial and postprandial glycaemic excursions. The resistance of mid-morning glucose peaking to calorie restriction should result in additional dietary or pharmacological measures at breakfast.

A thromboxane effect of a hydroxytyrosol-rich olive oil wastewater extract in patients with uncomplicated type I diabetes

OBJECTIVE

To assess the antioxidant/non-antioxidant effects of a hydroxytyrosol (HT)-rich phenolic extract from olive mill wastewaters administered with a breakfast.

DESIGN, SETTING AND SUBJECTS

Five type I diabetic patients received 25 mg of HT the first day and 12.5 mg/day the following 3 days. Blood sampling was carried out at T(0) (baseline) and T(4d) just before the breakfast + HT administration and at time points 1, 2, 3 and 4 h after T(0). Urines (24-h) were collected from T(0) to T(4d). Baseline HbA1c was generally inferior to 10%, glycemia was within the range 6-24 mmol/l, whereas total cholesterol, HDL-chol and triglycerides were normal.

RESULTS

The major finding was the 46% decrease in the serum TXB(2) production after blood clotting at T(4d). Plasma vitamin A, E, beta-carotene were not changed. Vitamin C tended to increase (P = 0.075). Plasma antioxidant capacity was enhanced at T(0)+1 h only, whereas its main determinants (albumin, bilirubin, uric acid) were not modified. Urinary 8-isoPGF(2alpha) levels were highly variable and were not affected significantly by HT administration.

CONCLUSION

The major effect of HT accounts for an antiaggregating platelet action, leading to a possible prevention of thrombotic and microthrombotic processes.

The V-Twin system (Dade Behring Laboratories): A useful tool for immunosuppressive drug monitoring

The predose trough cyclosporine (CsA) level (C0) was widely used to assess the possibility of drug nephrotoxicity. Owing to its potential limitation as an indicator of total drug exposure, 2-hour postdose (C2) monitoring has been considered to be a more accurate marker. The V-Twin analyzer (Vital SC, Netherlands) conceived for EMIT technologies (Dade Behring Laboratories) is proposed herein to determine CsA levels using a specific calibrator without any dilution, as well as tacrolimus (FK) and mycophenolate mofetil (MMF) levels. Both CsA (C0: n = 133 and C2: n = 55) and FK (n = 121) EMIT assays were compared to the RIA CsA assay (DiaSorin Laboratory) and to the MEIA tacrolimus assay (Abbott Laboratory), respectively. In addition, the feasibility of MMF EMIT assay was evaluated. Overall, 309 transplant patients were included in this study. For all parameters tested, total imprecision studies were lower than 10%, and the coefficient of linearity was r(2) > .99. For the CsA kit, the range of linearity was between 25 and 500 ng/mL for the C0 and 400 and 2000 ng/mL for the C2 assay. The values obtained were highly correlated with the RIA for the C0 levels (EMIT = 0.9 RIA+3.66; r = .97) and for the C2 levels (EMIT = 0.89 RIA-14.2; r = .956). Similar results were obtained with the EK EMIT kit, with a linearity range between 3 and 30 ng/mL, and a high concordance with the MEIA test (EMIT = 0.98 RIA+1.09; r = .96). Preliminary MMF results in 59 sera, containing from 0.1 to 30 microg/mL, showed that this examination could be included as a routine. The V-twin system is a useful tool for routine monitoring with a single method for C0 and C2 cyclosporine, tacrolimus, and mycophenolate levels.

Preliminary evaluation of a new chemiluminescence assay (liaison cyclosporine; diasorin laboratories) allowing both C0 and C2 cyclosporine levels determination: Comparison with RIA method

Cyclosporine (CsA) monitoring is generally assessed by trough concentration determinations (C0). Recently, the 2-hour postdose CsA level (C2) has been proposed to be a better measurement to predict graft outcome and prevent toxicity. However, using the available methods, C2 determinations require external dilution, which impairs the precision and practicability of the assay. This study assessed the performance characteristics of a new competitive chemiluminescence immunoassay (CLIA, DiaSorin Laboratories, Anthony, France) for the determination of both C0 and C2 CsA concentrations in whole blood on a Liaison analyzer. The results were compared with the RIA method (DiaSorin) used in our laboratory as a reference technique. Analytical performances showed that the total intra-assay variation coefficients (CVs) on the CLIA Liaison ranged from 7.6% to 11.3%, while the between-day imprecision was 11% (15.2%, 11.5%, and 6.5%). The linearity of the method was estimated over the range of 30 to 2400 ng/mL as a correlation coefficient of r = .997. Recoveries, which were checked by adding pure CsA to CsA-free blood, showed a mean value of 86%. A total of 236 whole-blood samples (31% women, 69% men of mean age 45 +/- 17 years) were subjected to a comparative study of CLIA-CsA versus RIA (radioimmunoassay) values, yielding a correlation coefficient >0.90 (CLIA = 0.825RIA+21.611; r(2) > .90). In conclusion, the CLIA Liaison CsA kit represents an alternative to the radioisotopic method, which allows both C0 and C2 determinations without any preanalytical step. The chemiluminescence method demonstrated good analytical performance and practicability in routine use.

Immunonephelometric determination of fibrinogen on citrated or heparinized plasma: comparison with functional Clauss method

BACKGROUND

Fibrinogen is routinely determined by functional assay on citrated plasma in the hematology department. However, immunoassay can be performed easily with nephelometric analyzer in the clinical chemistry laboratory allowing automatization. The aim of this study was first to compare the clotting von Clauss method (activity assay) with an immunonephelometric method (antigen assay) on the BN ProSpec (Dade Behring). Moreover, we evaluated the possibility of collecting blood samples on heparin to facilitate blood collection for clinicians and reduce required blood collection volumes for dosages.

METHODS

In a first step of experiment, the accuracy of immunonephelometric analytical performance was tested on heparinized and citrated tubes. For comparison studies, fibrinogen activity was then determined on citrated tubes in the hematology department and antigen measurement was performed on both citrated and heparinized plasma from 130 consecutive patients.

RESULTS

As a result, the immunonephelometric method shows reliable performance and clinical sample measurements are not affected by the method used, validating the use of heparinized plasma samples for fibrinogen antigen determination with Dade Behring reagents.

Lack of oxidative stress in a selenium deficient area in Ivory Coast--potential nutritional antioxidant role of crude palm oil

BACKGROUND

Previous studies have described an important selenium deficiency in a mountain region (Glanle) in the west of Ivory Coast.

AIM OF THE STUDY

To assess the antioxidant capacity of subjects from a selenium deficient area in Ivory Coast (Glanle region).

METHODS

This study involved 57 subjects, 18 to 69 years old, living in the Glanle region and 56 healthy controls living in the southern coastal region (Bodou). In the Glanle region families consume basically a vegetarian and crude palm oil diet, whereas in the Bodou region, families eat a fish-based diet with principally refined palm oil. Fasting blood samples were collected to assess the following parameters: lipid status (plasma total lipids; total-, HDL and LDL-cholesterol; triglycerides; phospholipids; fatty acid composition), plasma protein status (total protein, albumin, transthyretin, orosomucoid, CRP, transferrin), antioxidant capacity (plasma selenium, uric acid, retinol, alpha-tocopherol and tocotrienols levels, plasma seleno-glutathione peroxidase (GSHPx) activity) and oxidative stress markers (malondialdehyde (MDA) and advanced oxidation protein products (AOPP)).

RESULTS

The mountain region samples (Glanle) were characterized by significantly lower plasma albumin, total-, HDL- and LDL-cholesterol, retinol and selenium levels, plasma PUFA content and GSHPx activity, but significantly higher alpha-tocopherol index and total tocotrienol level, than controls from the coastal area (Bodou). These results suggest a higher exposure risk to oxidative stress for the mountain region subjects. However, the absence of oxidative damage in this group provides evidence of a selenium independent protection mechanism against oxidative stress. This protection is related to lower plasma LDL cholesterol and PUFA content, and to higher alpha-tocopherol index, delta and total tocotrienols.

CONCLUSION

The long-term consumption of crude palm oil could be considered as an effective protective factor against oxidative stress.

Mechanism of in vitro heme-induced LDL oxidation: effects of antioxidants

BACKGROUND

Heme protein toxicity, owing to generation of reactive oxygen species most likely by direct interaction between heme iron and hydrogen peroxide (H2O2), may be involved in various pathologies, including atherogenesis and pigmentary acute renal failure. The aim of this study was to investigate the mechanism of heme cytotoxicity and the effects of antioxidant therapies in an in vitro model of heme-induced low-density lipoprotein (LDL) oxidation.

MATERIALS AND METHODS

Human LDLs were exposed to heme, iron (Fe), protoporphyrin (PPIX) and PPIX-Zinc (Zn) with or without H2O2. Lipid peroxidation was monitored by measurement of conjugated diene formation (at the 234-nm absorbance). The effect of various antioxidants, such as vitamin E and vitamin C, reduced glutathione (GSH), and oxidized glutathione (GSSG), mannitol and desferoxamine (DFO) was further investigated in the established in vitro model of LDL oxidation.

RESULTS

Incubation of LDLs in the presence of heme/H2O2 induced lipid peroxidation with the optimal oxidation rate being at 5 microm heme/100 microm H2O2 doses. By contrast, incubation of LDL with H2O2, Fe, Fe/H2O2, PPIX, PPIX/H2O2, heme or PPIX-Zn did not initiate any LDL oxidation. In vitro, the vitamin E load protected native LDLs against heme/H2O2 oxidative modifications. Incubation of LDLs with increasing doses of vitamin C, GSH and DFO conferred a dose-dependent protection, while mannitol and GSSG had no effect.

CONCLUSIONS

Initiation and propagation of heme-induced lipid peroxidation is not mediated by a Fenton reaction but depends on specific interactions between heme and H2O2. It may result from the generation of ferryl and perferryl radicals derived from hemic Fe and H2O2 interactions. A protective effect of vitamins E, C, GSH and DFO was demonstrated in this model.

Does systemic inflammation trigger local exercise-induced oxidative stress in COPD?

Inflammatory abnormalities may be involved in the inadequate basal oxidant/antioxidant balance and local exercise-induced oxidative stress in chronic obstructive pulmonary disease (COPD) patients. The time course of oxidative stress and inflammation was investigated in 10 COPD patients and seven healthy subjects before and after local dynamic quadriceps endurance exercise at 40% of maximal strength. Venous samples were collected before, immediately after and up to 48 h after exercise. At rest, levels of an oxidant released by stimulated phagocytes, the superoxide anion, were significantly higher in patients, as were plasma levels of C-reactive protein, tumour necrosis factor-alpha and interleukin-6, inflammatory markers. An inverse relationship was found between baseline C-reactive protein levels and endurance time in patients. Six hours after exercise, superoxide anion release and levels of protein oxidation products, an index of oxidative stress, increased similarly in both groups, whereas thiobarbituric acid reactive substance levels, another index of oxidative stress, increased significantly only in patients. Plasma nonenzymatic antioxidant and inflammatory cytokine levels were unchanged by the exercise protocol. The increased baseline systemic inflammation in chronic obstructive pulmonary disease patients could be related to disturbed oxidant/antioxidant balance, and, together, these may have triggered the exercise-induced oxidative stress. The absence, however, of local exercise-induced systemic inflammation suggests that additional mechanisms explain local exercise-induced oxidative stress.

Determination of beta2-microglobulin in biological samples using an immunoenzymometric assay (chemiluminescence detection) or an immunoturbidimetric assay: comparison with a radioimmunoassay

Monitoring beta2-microglobulin (beta2M) in biological fluids has gained considerable interest in pathologies such as haematologic malignancies, renal diseases, and chronic inflammatory diseases. Due to limitations of the RIA in the routine laboratory, we measure beta2M with non-isotopic methods. 189 patients suffering from myeloma (n=66), end stage renal failure (n=54) or inflammation (n=69) were included in this study. beta2M was determined in serum, urine and dialysate using an immunoenzymometric assay with chemiluminescence detection [Immulite Diagnostic Products Corporation (DPC), La Garenne Colombes, France] and an immunoturbidimetric assay (Olympus, Rungis, France). The data were compared with a radioimmunoassay (Immunotech, Marseille, France) taken as a reference. Using serum samples, the immunoenzymometric assay with chemiluminescence detection and the immunoturbidimetric assay have reliable analytical performances. Values obtained with serum samples are highly correlated with the radioimmunoassay (DPC/RIA r2=0.84; Olympus/RIA r2=0.94) whatever the type of pathology; however an over-estimation which could be related to cross reactivity with beta2M fragments was observed with the RIA method as suggested by crossover calibration and recovery studies. Values obtained with urinary samples (n=96) are closely related to those obtained with the RIA (DPC/RIA r2 = 0.98; Olympus/RIA: r2=0.99). Despite the low levels observed in dialysate (n=57) good correlations were observed between Olympus vs DPC (r2=0.85). By contrast, the two non-isotope methods are poorly related with the RIA method (DPC vs RIA r2=0.47 and Olympus vs RIA r2=0.54). In conclusion, the immunoenzymometric assay with chemiluminescence detection or the immunoturbidimetric assay could be used in the routine laboratory in order to determine beta2M in plasma, urine and dialysate.

Decrease in LDL size in HIV-positive adults before and after lopinavir/ritonavir-containing regimen: an index of atherogenicity?

BACKGROUND

Hypertriglyceridemia (HTG) is frequently observed during highly active antiretroviral therapy (HAART) including protease inhibitor. Apolipoprotein (apo) CIII could be involved in this HTG by inhibition of triglyceride (TG) hydrolysis, which leads to the occurrence of small dense low density lipoprotein (sdLDL), a recognized cardiovascular risk factor.

OBJECTIVE

To characterize the influence of lopinavir/ritonavir-containing regimen on lipoprotein profile.

DESIGN AND METHODS

24 antiretroviral-experienced HIV infected adults (including 14 patients in therapeutic interruption of at least 2 months) and 14 HIV uninfected healthy controls were enrolled. Serum lipid parameters (total cholesterol (TC), HDL-C, LDL-C, TG, apoA1, apoB, apoCIII), lipoprotein composition and LDL size were determined before initiation of lopinavir/ritonavir-containing regimen, and at 1 and 3 months thereafter.

RESULTS

At baseline an atherogenic lipid profile was evidenced, characterized by a moderate HTG associated to a smaller mean LDL size (25.16 vs 25.93 nm, P<0.001), an enrichment in TG of LDL (11.4 vs 6.0%, P<0.01) and a high prevalence of sdLDL (75 vs 7%, P<0.01) when compared to controls. After 1 month of lopinavir/ritonavir-containing regimen, a significant reduction of LDL size (24.81 vs 25.16 nm, P<0.05) and a significant increase in cholesterol total (5.53 vs 4.49 mmol/l, P<0.001), in TG (4.20 vs 2.01 mmol/l, P<0.001), in apoA1 (1.28 vs 1.11 g/l, P<0.001), in apoB (1.08 vs 0.94 g/l, P<0.01), in apoCIII (0.16 vs 0.10 g/l, P<0.001), in TG percentage in LDL (14.4 vs 11.4, P<0.05) and in TG percentage in HDL (10.2 vs 8.3, P<0.05) were observed.

CONCLUSIONS

Advanced stage of HIV infection is associated with an atherogenic lipid profile including a high prevalence of sdLDL. Lopinavir/ritonavir-containing regimen accentuates the reduction of LDL size. Since fibrates decrease TG and increase LDL size, they appear as a logical option to manage HAART-induced HTG.

[Vascular access, an underestimated source of inflammation in dialysis patients]

The surveillance of inflammation in dialysis patient, by means of sensitive markers such as CRP, is strongly recommended in a continuous quality improvement treatment approach. Chronic inflammation being deleterious via several pathways including malnutrition, accelerated arteriosclerosis and beta 2M-amyloidosis, microinflammation must diagnosed and corrected as soon as possible in dialysis patients. Vascular access represents an underestimated source of inflammation in hemodialysis patients. In the absence of organic cause of inflammation, the vascular access should be always incriminated and meticulously investigated. Withdrawing the suspected prosthetic or unused material (PTFE or catheter) should be considered as the best way of correcting the inflammation and restoring the recombinant erythropoietin (EPO) activity in the dialysis patient.

[Is C-reactive protein a marker of inflammation?]

C-reactive protein (CRP) is the prototype of acute-phase protein which is secreted by the liver in response to a variety of inflammatory cytokines. Levels of CRP can increase up to 1000-fold very rapidly after the onset of inflammation and decrease just as rapidly with the resolution of aggression. CRP is a member of the ancient highly conserved pentraxin family of proteins and it is arranged in a cyclic homopentameric structure. The important role of CRP in innate immunity is largely due to its opsonizing abilities, its capability to activate human complement and to bind to immunoglobulin G receptors. CRP can bind phosphocholine largely present in bacterial membranes, cell membrane and lipoproteins, in addition CRP can recognize nuclear constituent in damaged cells. CRP can activate C3 convertase through the classical pathway but not C5 convertase resulting in generation of opsonic complement fragments. Interactions of CRP with Fc receptors lead to the generation of proinflammatory cytokines and reactive oxygen species by monocyte/macrophage while inhibit neutrophiles functions. Recently, CRP was demonstrated to play an active role in atherogenesis and it has been largely proven that a microinflammatory state as defined by a moderate increase in CRP (up to 3 mg/l), is associated with an increased risk for arterial disease. Moreover it has been postulated that CRP may be a useful tool for monitoring drug therapy.

Evidence of local exercise-induced systemic oxidative stress in chronic obstructive pulmonary disease patients

Chronic inactivity may not be the sole factor involved in the myopathy of chronic obstructive pulmonary disease (COPD) patients. One hypothesis is that exercise-induced oxidative stress that leads to muscle alterations may also be involved. This study investigated whether exercise localised to a peripheral muscle group would induce oxidative stress in COPD patients. Eleven COPD patients (FEV1 1.15+/-0.4 L (mean+/-SD)) and 12 healthy age-matched subjects with a similar low quantity of physical activity performed endurance exercise localised to a peripheral muscle group, the quadriceps of the dominant leg. The authors measured plasma levels of thiobarbituric reactive substances (TBARs) as an index of oxidative stress, the release in superoxide anion (O2*-) by stimulated phagocytes as an oxidant, and blood vitamin E as one antioxidant. Quadriceps endurance was significantly lower in the COPD patients compared with healthy subjects (136+/-16 s versus 385+/-69 s (mean+/-SEM), respectively). A significant increase in TBARs 6 h after quadriceps exercise was only found in the COPD patients. In addition, significantly higher O2*- release and lower blood vitamin E levels were found in COPD patients than in controls at rest. This blood vitamin E level was significantly correlated with the resting level of plasma TBARs in the COPD patients. This study mainly showed that quadriceps exercise induced systemic oxidative stress in chronic obstructive pulmonary disease patients and that vitamin E levels were decreased in these patients at rest. The exact relevance of these findings to chronic obstructive pulmonary disease myopathy needs to be elucidated.