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Mineral metabolism disturbances are common in chronic kidney disease (CKD) and have been classified as a new clinical entity, also known as CKD-mineral and bone disorders (CKD-MBD). A decrease in the bone strength, whose clinical manifestation is a tendency for fracture, has been recognized as an important component of CKD-MBD. Because of ethical issues, measurements of the bone strength in the human body are usually limited to noninvasive techniques, such as radiography, dual-energy X-ray absorptiometry and the assays of bone turnover biomarkers. However, it has been postulated recently that the evidence concerning bone strength based solely on the determination of the bone quantity may be insufficient and that bone quality should also be examined. In this regard, an animal model of CKD can represent an experimental tool to test the effectiveness of new therapeutic strategies. Despite the many available methods that are used to diagnose metabolic bone disorders and predict fracture risk especially in small rodents with CKD, it turns out that the most appropriate are biomechanical tests, which can provide information about the structural and material properties of bone. The present review summarizes and discusses the principles for carrying out selected biomechanical tests (3-point bending test and compression test) and their application in clinical practice., (© 2015 S. Karger AG, Basel.)

Background/aims: Matrix metalloproteinases (MMPs), their inhibitors (TIMPs), oxidative stress (SOX) and kynurenine (KYN) pathway have been postulated in cardiovascular disease (CVD) progression. We hypothesized the possible association between the MMP/TIMP system, KYNs and CVD prevalence in continuous ambulatory peritoneal dialysis (CAPD) patients., Methods: We assessed MMP-2, MMP-9, TIMP-1, TIMP-2, KYN and its metabolite - quinolinic acid (QA), and SOX marker - Cu/Zn superoxide dismutase (Cu/Zn SOD) levels in CAPD patients both with and without CVD and healthy controls., Results: MMP-2, TIMP-2, Cu/Zn SOD, KYN and QA were significantly higher in CAPD patients with CVD than in patients without CVD and controls. MMP-2 and TIMP-2 were positively correlated with QA and Cu/Zn SOD levels, and the strong association was between MMP-2 and TIMP-2 levels. Multiple regression analyses identified Cu/Zn SOD, TIMP-2, QA and QA/KYN ratio as the factors independently associated with MMP-2, whereas MMP-2 and Cu/Zn SOD were independent variables affecting TIMP-2 levels., Conclusions: MMP-2 and TIMP-2 concentrations were higher in CAPD patients with CVD than in patients without CVD and healthy controls. Upregulation of the MMP-2/TIMP-2 system was associated with QA levels and increased oxidative status, suggesting the connection between KYN pathway activation, arterial remodeling and CVD prevalence in uremic patients on CAPD treatment., ((c) 2010 S. Karger AG, Basel.)

Aims: We designed a study to evaluate whether erythropoietin (EPO), given to patients on continuousambulatory peritoneal dialysis (CAPD) both with and without diabetes mellitus (DM), influences tissue factor (TF), tissue factor pathway inhibitor (TFPI) and oxidative stress (SOX)., Methods: We assessed TF, TFPI and a marker of SOX, Cu/Zn superoxide dismutase (Cu/Zn SOD) in 16 diabetic CAPD patients (8 with EPO therapy), 39 non-diabetic CAPD patients (23 with EPO therapy) and 18 healthy controls., Results: Patients on CAPD showed a significant increase in plasma concentrations of TF, TFPI and Cu/Zn SOD as compared to controls. EPO therapy was related to a decrease in these parameters in diabetic patients, whereas in non-diabetic patients EPO did not affect their levels. In diabetics, TF was positively correlated with TFPI and Cu/Zn SOD levels. There was a positive relationship between TFPI and Cu/Zn SOD, whereas inverse relationships existed between TFPI and haemoglobin, haematocrit (Ht), EPO dose and triglycerides. Multivariate analysis showed that independent variables linked to TFPI levels in diabetic patients were Cu/Zn SOD, Ht and EPO dose., Conclusion: Our data suggest that correction of anaemia with EPO therapy is associated with a significant decrease in TF, TFPI and SOX in diabetic CAPD patients., (Copyright 2007 S. Karger AG, Basel.)

The value of neutrophil-gelatinase-associated lipocalin (NGAL) was highlighted as a novel biomarker for the detection of acute renal failure. We tested the hypothesis whether NGAL could represent an early biomarker of contrast-induced nephropathy (CIN) in 100 patients with normal serum creatinine values undergoing percutaneous coronary interventions (PCI). In addition, we assessed serum and urinary NGAL in relation to cystatin C, estimated glomerular filtration rate, and serum and urinary creatinine in these patients. We measured urinary and serum NGAL values before and 2, 4, 8, 24, and 48 h after the PCI. We found a significant rise in serum NGAL levels 2, 4, and 8 h after the PCI and in urinary NGAL values 4, 8, and 24 h after a PCI procedure. Cystatin C rose significantly 24 h after the procedure. The prevalence of CIN was 11%. The NGAL levels were significantly higher 2 h after the PCI (serum NGAL) or 4 h after the PCI (urinary NGAL), whereas the cystatin C values were higher only 8 and 24 h after a PCI procedure in patients with CIN. In multivariate analysis, only serum creatinine was a predictor of serum NGAL before a PCI. NGAL may represent a sensitive early biomarker of renal impairment after PCI. Serum creatinine level, the presence of diabetes, and the duration of the PCI may affect serum NGAL values and kidney function following a PCI procedure., ((c) 2007 S. Karger AG, Basel.)

Background: Matrix metalloproteinases (MMPs) and their tissue inhibitors (TIMPs) play an important role in the atherosclerosis. Recombinant human erythropoietin (EPO) has become widely used to treat anemic hemodialyzed (HD) patients; however, an increased mortality has been reported for HD patients with cardiovascular disease when randomly assigned to normal hematocrit by EPO. Therefore, we conducted a study examining the effect of EPO on MMPs/TIMPs system, oxidative stress and inflammation in these patients., Methods: Assessment of MMP-2, MMP-9, TIMP-1 and TIMP-2 were performed in 20 stable HD patients and 15 healthy controls. Additionally, the effects of EPO on malondialdehyde (MDA)--a marker of SOX and C-reactive protein (CRP) levels--as a marker of inflammation were also investigated. Of the 20 patients, 10 were receiving EPO therapy [HD-EPO(+)] for 12 months or more and 10 were not receiving EPO therapy [HD-EPO(-)]. Both groups were not receiving iron supplementation., Results: All parameters, with the exception of MMP-9, were lower in the healthy subjects compared with the HD subjects, irrespective of EPO administration. There was no difference in MMPs/TIMPs system, MDA and C-reactive levels between HD-EPO(+) and HD-EPO(-) patients., Conclusion: Erythropoietin therapy did not influence MMPs/TIMPs system, inflammation, or SOX in a low-risk HD patient population, in the absence of concomitant iron supplementation and mean Hg levels within target., (2007 S. Karger AG, Basel)

Background: CC-chemokines are now widely accepted in the recruitment of leukocytes from the blood compartment into tissues, and their role in the progression of atherosclerosis has been documented. Recombinant human erythropoietin (EPO) has become widely used to treat anemic HD patients. However, little is known about the effect of EPO on the plasma CC-chemokine levels and intima-media thickness (IMT) in HD patients., Methods: Assessment of CC-chemokines: monocyte chemoattractant protein-1 (MCP-1), macrophage inflammatory proteins (MIP-1alpha, MIP-1beta), regulated upon activation, normal T cell expressed and secreted (RANTES) and IMT were performed in 26 stable HD patients and 15 healthy controls. The patients were divided into 3 groups: group I (n = 8, without EPO), group II (n = 9, EPO at a mean dose of 76 +/- 48 U/kg/week for more than 4 months), and group III (n = 9, EPO at a mean dose of 110.5 +/- 21 U/kg/week for more than 12 months), none of them on iron therapy., Results: MCP-1, MIP-1alpha, MIP-1beta and IMT values were significantly higher, whereas RANTES were significantly lower in HD patients without EPO therapy than those in healthy controls. CC-chemokine levels were found to be significantly lower in patients administered EPO when compared to subjects without EPO. In the patients treated with EPO for more than 12 months IMT values were significantly decreased compared to patients not receiving this hormone., Conclusion: These results suggest that long-term EPO therapy decreased CC-chemokine and IMT values in patients undergoing regular HD in the absence of concomitant iron supplementation., (Copyright (c) 2006 S. Karger AG, Basel.)

Background: Hepcidin synthesis in hepatocytes is modulated in response to anemia, hypoxia or inflammation. A cross-sectional study was performed to assess hepcidin correlations with markers of iron status, erythropoietin therapy and markers of inflammation in hemodialyzed patients and in the healthy volunteers., Methods: Iron status, complete blood count, creatinine, albumin, lipids were assessed using standard laboratory methods. Hepcidin and high-sensitivity CRP were measured using commercially available kits., Results: Serum iron, TIBC, TSAT, erythrocyte count, Hb, Ht, platelet count, albumin, and cholesterol were lower, whereas ferritin and hepcidin were higher in hemodialyzed patients over controls. Hepcidin correlated positively with triglycerides, albumin, aspartate aminotransferase, lymphocyte count, ferritin and erythropoietin dose and negatively with erythrocyte count, Hb, and Ht in hemodialyzed patients. In multiple regression analysis, triglycerides (beta value was 0.28, p = 0.02) and albumin (beta value was -0.31, p = 0.006) were correlates of hepcidin in hemodialyzed patients., Conclusions: Elevated hepcidin levels in hemodialyzed patients may be due to functional iron deficiency and anemia. Liver plays an important role in the synthesis of hepcidin. Low-grade inflammation, frequently found in hemodialyzed patients, might also contribute to elevated hepcidin concentration. Hypothesis that hepcidin might link anemia, inflammation and liver function in kidney disease should be further evaluated.

Background: Thrombin activatable fibrinolysis inhibitor (TAFI) is a regulator of endogenous fibrinolysis. Heparin is used routinely during dialysis sessions to prevent clot formation in the extracorporeal circuit; therefore the aim of the study was to assess whether unfractionated heparin or low-molecular-weight heparins affect TAFI concentration and activity in hemodialyzed patients., Methods: Dalteparin (n = 16) or enoxaparin (n = 25) were administered before the second hemodialysis session in the week in a single dose, whereas unfractionated heparin (n = 18) was given first as a bolus, then in a pump. We also evaluated thrombin activity (thrombin-antithrombin complexes, prothrombin fragments 1 + 2), TAFI activator, thrombomodulin, a catalyzer of TAFI activation and a marker of endothelial cell injury, and the degree of plasmin generation (plasmin-antiplasmin complexes)., Results: TAFI concentration, activity and markers of ongoing coagulation, i.e. prothrombin fragments 1 + 2 and thrombin-antithrombin complexes, were significantly higher in patients anticoagulated with unfractionated heparin when compared to both enoxaparin and dalteparin groups. Thrombin-antithrombin complexes, plasmin-antiplasmin complexes, prothrombin fragments 1 + 2, and thrombomodulin did not differ between patients anticoagulated with dalteparin and enoxaparin., Conclusions: Our results suggest that low-molecular-weight heparins influence TAFI and other hemostatic parameters in hemodialyzed patients to a lesser degree than unfractionated heparin. Increased TAFI is possibly due to thrombin appearance during hemodialysis with unfractionated heparin., (Copyright 2004 S. Karger AG, Basel)

Aims: Reactive oxygen species have been implicated in increased vascular endothelial growth factor (VEGF) and monocyte chemoattractant protein (MCP-1) levels in vascular cells, which may promote atherosclerosis progression., Methods: We studied the association between pre-dialysis plasma levels of VEGF and MCP-1 in 45 hemodialysis (HD) patients with and without cardiovascular disease (CVD) in conditions of increased oxidative stress (SOX)., Results: Compared to the controls, HD patients, especially those with CVD, showed a significant increase in plasma concentrations of Cu/Zn superoxide dismutase (Cu/Zn SOD), C-reactive protein (CRP), MCP-1 and VEGF. The levels of CRP, MCP-1 and VEGF were more increased in patients with CVD than in patients without CVD (all p < 0.01). VEGF strongly and positively correlated with MCP-1 only in HD patients with CVD. Additionally, both VEGF and MCP-1 were associated with Cu/Zn SOD in the whole HD group., Conclusion: For the first time our data indicate a correlation between VEGF and MCP-1 levels in HD patients with CVD in conditions of increased SOX. This interaction may reflect the new role of MCP-1 as an arteriogenic factor in HD patients with CVD., (Copyright 2004 S. Karger AG, Basel)

Background/aim: Recently emerging evidence suggests that oxidative stress (SOX) may participate in atherogenesis. The aim of the present study was to establish whether enhanced SOX, involving endothelial injury, activation of coagulation, and inflammatory reaction, could be implicated in atherosclerotic diseases in haemodialysis (HD) patients., Methods: Markers of SOX, endothelial injury, coagulation, and cytokines, were measured in the plasma of HD patients with and without cardiovascular disease (CVD), and of healthy controls by ELISA methods. Remodeling of the carotid arteries was assessed by measuring the intima-media thickness (IMT) as a surrogate of atherosclerotic disease in all groups., Results: Markers of SOX, endothelial injury, and extrinsic coagulation pathway activation and IMT values were significantly elevated in HD patients, especially in those with CVD when compared with the control group. The von Willebrand factor antigen (vWF:Ag) levels were more increased in the patients with CVD than in those without. Furthermore, the plasma levels of tumour necrosis factor alpha, monocyte chemo-attractant protein 1, and macrophage inflammatory protein 1 beta were significantly higher only in the HD group with CVD when compared with the controls. The IMT was strongly and directly correlated with Cu/Zn superoxide dismutase. Both IMT and Cu/Zn superoxide dismutase were positively correlated with age, thrombomodulin, vWF:Ag, tissue factor, tissue factor pathway inhibitor, prothrombin fragment F1 + 2, monocte chemo-attractant protein 1, macrophage inflammatory protein 1 beta, and tumour necrosis factor alpha levels. Multivariate analysis identified vWF:Ag as the only independent variable significantly associated with an increased IMT., Conclusions: The present study suggests that enhanced SOX, involved pro-atherogenic cytokine and chemokines levels, endothelial injury, and coagulation activation may constitute a pathway for accelerated atherosclerosis in HD patients. The significant, independent association between IMT and vWF:Ag should be assessed in future studies to determine whether vWF:Ag elevation is causative or a by-product of the increased IMT., (Copyright 2004 S. Karger AG, Basel)

Background: Increased oxidative stress (SOX) has been reported in hemodialyzed (HD) patients, but its influence on CC-chemokine levels remains unknown., Methods: The levels of 3 distinct SOX markers (Cu/Zn superoxide dismutase (Cu/Zn SOD), total lipid peroxide, and autoantibodies against oxidized LDL (OxLDL-Ab)), as well as those of 4 CC-chemokines (monocyte chemoattractant protein-1 (MCP-1), macrophage inflammatory proteins (MIP-1alpha, MIP-1beta), regulated upon activation, normal T cell expressed and secreted (RANTES), and tumor necrosis factor-alpha (TNF-alpha)) were measured pre- and post-HD session in 15 HD patients with cardiovascular disease (CVD) and 12 HD patients without CVD (pre- and post-HD session) and 17 controls., Results: Cu/Zn SOD levels were elevated in HD patients (both before and after HD) compared to controls (p < 0.001). Total lipid peroxide levels were similar in the controls in pre-dialysis samples, but were increased after a HD session (p < 0.001). Pre-dialysis OxLDL-Ab levels were increased only in the HD group with CVD compared to controls (p < 0.05). The pre-dialysis plasma levels of TNF-alpha (p < 0.001), MCP-1 (p < 0.001) and MIP-1beta (p < 0.01) were increased both in all HD patients and subgroups with CVD when compared to the controls, and remained significantly elevated when measured after HD. Dialysis increased MCP-1 (p < 0.05) and MIP-1beta (p < 0.001) levels as compared to the controls as well as in patients without CVD. Plasma RANTES was significantly lower before HD (p < 0.05) and after HD (p < 0.001) in patients with CVD. Patients without CVD and all HD patients also had lower RANTES before and after HD when compared to controls (all p < 0.001). A positive correlation was observed between plasma pre-dialysis Cu/Zn SOD levels and the other SOX markers (all p < 0.05), age (p < 0.05) and duration of hemodialysis (p < 0.001). A positive relationship existed between plasma Cu/Zn SOD levels and those of MCP-1, MIP-1beta and TNF-alpha (all p < 0.001). RANTES levels negatively correlated with Cu/Zn SOD (p < 0.0001).TNF-alpha positively correlated with age (p < 0.05), total lipid peroxide (p = 0.010), MCP-1 (p < 0.01) and MIP-1beta levels (p < 0.01). An identifiable association exists between MCP-1 and MIP-1beta levels (p < 0.01), whereas both MCP-1 and MIP-1beta were inversely correlated with RANTES (both p < 0.05)., Conclusion: Our data indicate for the first time a probable functional relationship between oxidative stress and CC-chemokine levels in hemodialyzed patients, particularly in those with cardiovascular disease. This relationship may represent one of the mechanisms involved in the progression of atherosclerosis in these patients., (Copyright 2004 S. Karger AG, Basel)

Background/aims: Chronic inflammation is a common cause of severe anemia and hyporesponsiveness to recombinant erythropoietin (EPO) therapy in maintenance hemodialysis (HD) patients. We compared various acute-phase markers and ex vivo platelet aggregation tests in relation to clinical conditions in order to find factors predictive of hemoglobin (Hb) and endogenous EPO levels in a cross-section of clinically stable HD patients., Methods: In 100 subjects, pre-HD blood levels of C-reactive protein (CRP), alpha(1)-acid-glycoprotein (AGP), alpha(1)-antitrypsin (AT), immunoglobulin (Ig) M and G (by nephelometry), antigens of endothelial von Willebrand factor (vWF), type 1 plasminogen activator inhibitor and thrombomodulin, interleukin-6, lipoprotein(a) [Lp(a)] and EPO (by ELISA), and albumin, fibrinogen, iron metabolism indices, thyroid-stimulating hormone, phosphorus, parathormone, total cholesterol, triglycerides, viral hepatitis B/C markers, liver enzyme, and aluminium were determined. Platelet aggregations in response to ristocetin (RIPA), adenosine diphosphate, and collagen were measured in whole blood (electric impedance method) and platelet-rich plasma (optical aggregometry)., Results: Hb levels inversely correlated with IgM, Lp(a), soluble vWF antigen, phosphorus, and all platelet aggregations in whole blood, but not in platelet-rich plasma. HD duration and triglycerides were positive correlates of anemia. In a multivariable analysis, increased IgM, short HD duration, increased Lp(a) and enhanced whole blood RIPA (in descending order of significance) were independent predictors of low Hb levels. In 51 patients not treated with recombinant EPO, serum levels of this hormone inversely correlated with whole blood RIPA, AT, age, vWF antigen, AGP, and positively with viral hepatitis marker. Anemia and EPO levels were not affected by gender, body mass index, cause of renal failure, residual renal function, HD dose, protein catabolic rate, use of different heparins or dialysate buffers, ACE inhibitor therapy, and parathyroid or thyroid function. In additional 10 patients, single HD session resulted in an increase in IgM levels associated with a fall in total lymphocyte counts., Conclusion: Subclinical inflammation is an important determinant of anemia in maintenance HD patients. Increased serum IgM reflecting a microinflammatory effect of HD procedures, enhanced whole blood RIPA as a surrogate of vascular endothelial damage, and Lp(a) as its promoter could be markers of such impaired erythropoiesis., (Copyright 2002 S. Karger AG, Basel)

Von Willebrand factor (vWF) abnormalities are involved in the hemostatic disturbances of uremia. Studies of vWF in both anemic and recombinant erythropoietin (EPO)-treated maintenance hemodialysis (HD) patients have given inconsistent results that could be partially dependent on the methodology. Therefore, the reciprocal relationships between four different vWF assays were studied in HD patients in relation to EPO therapy. Plasma vWF activity measured by ELISA using monoclonal antibodies against platelet glycoprotein (GP) Ibalpha (vWF:Act), plasma vWF antigen concentration by ELISA employing polyclonal antihuman vWF antibodies (vWF:Ag), and functional vWF activity by ristocetin-induced platelet aggregation (RIPA) in both platelet-rich plasma (PRP) and whole blood were studied in 70 HD patients. In the whole group, no correlations between these assays were found. In the non-EPO patients (n = 32), vWF:Act was correlated with vWF:Ag (r = 0.504, p = 0.003) but not with vWF activity by RIPA in PRP. In the EPO-treated patients (n = 38), vWF:Act was higher than in the untreated ones (p = 0.001), and vWF:Ag was related to the whole-blood RIPA (r = 0.386, p = 0.016). In conclusion, the platelet GP Ibalpha-binding epitope of the vWF molecule assessed by vWF:Act ELISA is intact in HD patients. However, this assay does not reflect the functional vWF activity as measured by RIPA in PRP. In EPO-treated patients, the GP Ibalpha-binding domains of vWF are more available but the plasmatic vWF monomers are neither more numerous by vWF:Ag ELISA nor more hemostatically active by RIPA PRP. The whole blood RIPA test has some potential for the quantification of vWF monomers in EPO-treated HD patients., (Copyright 2001 S. Karger AG, Basel)

So far it is not clear how erythropoietin affects the anticoagulant properties of vascular endothelium in uremia. Since serotonin is also thought to play a role in the pathogenesis of thrombosis, the aim of the study was to evaluate major components of extrinsic coagulation pathway, markers of endothelial cell injury, lipoprotein (a) and peripheral serotonergic mechanisms during rHuEPO therapy in hemodialyzed patients. The study was performed on chronically hemodialyzed patients divided into two groups: with rHuEPO treatment and without rHuEPO therapy in relation to the control group. In uremic patients, thrombomodulin and von Willebrand factor, activity of factor VII, tissue factor pathway inhibitor (TFPI) activity, TFPI and tissue factor (TF) concentrations, lipoprotein (a) level were significantly higher when compared to healthy volunteers. Treatment with rHuEPO resulted in a further significant rise in markers of endothelial cell injury: thrombomodulin and von Willebrand factor and TFPI concentration. Extrinsic coagulation factors: activities of factor VII and X, TFPI activity and TF activity and concentration, lipoprotein (a) and vitronectin remained unchanged during rHuEPO therapy. Platelet serotonin content and whole blood serotonin were significantly lower in uremic patients relative to healthy volunteers and during rHuEPO treatment they increased significantly. Whole blood serotonin reached normal values. Plasma serotonin, significantly elevated in uremia, did not change during rHuEPO therapy. Serotonin uptake by uremic platelets was significantly impaired and remained unaltered during rHuEPO administration. Serotonin release by uremic platelets was also significantly depressed but a significant improvement was observed in rHuEPO-treated patients. Our data suggest that endothelial injury, TF pathway components and peripheral serotonergic system disturbances may predispose to thromboembolic complications and play a role in the pathogenesis of atherosclerosis in uremic patients, particularly treated with rHuEPO. Increase in TFPI may compensate the increase in TF in these patients., (Copyright 2000 S. Karger AG, Basel)