Serum paraoxonase activity in uremic predialysis and hemodialysis patients

BACKGROUND: Paraoxonase (PON1) is a high-density lipoprotein (HDL)-associated enzyme and has been shown to reduce the susceptibility of low-density lipoprotein (LDL) to lipid peroxidation. This study aimed to investigate the activity and phenotype distribution of serum paraoxonase in uremic patients, and to evaluate the correlations of uremia-associated substances (urea, creatinine (Cr) and uric acid) with paraoxonase activity. METHODS: Twenty-eight patients with chronic renal failure (CRF), 44 patients with CRF undergoing hemodialysis (HD) and 26 healthy controls were included in this study. Paraoxon or phenylacetate was used as a substrate for measuring paraoxonase and arylesterase activity, respectively. The double substrate method was used to assign phenotypes. Serum lipid parameters were determined by routine laboratory methods. RESULTS: Paraoxonase activity, HDL-cholesterol and apolipoprotein (apo) AI levels were found to be significantly lower in HD patients than in controls. However, HDL-standardized paraoxonase activity (PON activity/HDL) was not different in the HD patients compared to controls. Arylesterase activity was significantly lower in both CRF and HD patients than in controls. Paraoxonase phenotype distribution was not different among the groups according to the double substrate method. Serum paraoxonase and arylesterase activities correlated inversely with serum urea and Cr levels. CONCLUSION: Patients on long-term HD have reduced paraoxonase/arylesterase activities and this could be related to reduced HDL-cholesterol and apo AI levels, as well as increased urea and Cr levels in uremia.     

Serum antioxidant activity in uremic patients

Serum antioxidant activity (AOA) was examined in 35 healthy subjects and 111 patients with chronic renal failure (CRF), consisting of 13 patients in the predialysis stage, 11 requiring the start of regular dialysis therapy (RDT) and 87 undergoing RDT. Serum AOA was determined by assaying serum activity to inhibit malondialdehyde (MDA) generation. AOA levels were significantly lower in CRF patients, and the lowest levels were noticed in patients with uremic symptoms requiring the start of RDT. These levels were restored to a subnormal level during RDT. Defective serum AOA appears to be an endogenous metabolic consequence in uremia. Sera with low AOA tended to show high MDA levels, indicating that patients with low serum AOA were susceptible to cellular injury by lipid peroxidation. It is proposed that defective serum AOA may contribute to a certain uremic toxicity through peroxidative cell damage.     

Hormonal changes in haemodialysed and in kidney-transplanted patients

A total of 48 haemodialysed patients were studied by radioimmunoassay for the serum concentrations of parathormone, calcitonin, gastrin, insulin, prolactin, T₃, T₄, rT₃, TSH and cortisol. Residual urines were measured for cAMP and ultrafiltrates for iPTH and gastrin. The duration of the dialysis programme, the number of haemodialysis sessions per week, sex distribution, the dialysis alternatives (including haemofiltration, haemoperfusion) and successful kidney transplantations were correlated with the serum hormone levels. Significant increases in PTH gastrin and prolactin values were demonstrated in the dialysed patients. However, their calcitonin and insulin concentrations decreased, parallel with the time elapsed since the start of the haemodialysis programme (HDP). The number of dialysis sessions per week was found to affect the hormone concentrations diversely. In the course of hemofiltration and haemoperfusion some of the centrations diversely. In the course of haemofiltration and haemoperfusion some of the hormone levels (e.g. PTH, gastrin) decreased significantly. The patients were in general euthyroid. One of them, on HDP for several years, developed clinical and laboratory signs indicative of hyperthyroidism. In a considerable proportion of the cases the results of the hormone studies (increased PTH, CT, cAMP) were consistent with secondary hyperparathyroidism. Kidney transplantation was followed by a decline of the serum prolactin, parathormone, calcitonin and aldosterone levels.     

Serum paraoxonase activity in patients with low glomerular filtration rates

Objective: Epidemiological and experimental studies indicate that kidney disease is associated with increased oxidative stress. Our aim was to determine whether paraoxonase 1 (PON1) activity is altered in patients with moderately decreased glomerular filtration rates (GFRs) compared to healthy controls. Material and methods: Forty-eight patients showing relatively low GFRs upon renal scintigraphy with ^99mTc-DTPA were compared to 40 age-matched healthy subjects. Serum PON1 activity was measured spectrophotometrically. Lipid hydroperoxide levels were measured via iodometric assay. Results: The mean ages of the patient and control groups were 32.09 ± 6.10 (range 23–50) and 31.30 ± 5.30 (range 20–46) years, respectively. Serum PON1 (p= 0.949) and high-density lipoprotein (p= 0.473) levels did not differ between groups. Significant differences were detected between groups in terms of mean triglyceride (p= 0.009), very-low-density lipoprotein (p = 0.010), lipid hydroperoxide (p = 0.026), urea (p = 0.012), and creatinine (p = 0.001) levels, whereas total cholesterol (p = 0.520) and low-density lipoprotein (p = 0.161) were similar between groups. Mean GFR was significantly lower in the low GFR group compared to the control (p = 0.000). Conclusion: Our results indicate that PON1 activity and high-density lipoprotein levels may not be determining factors in premature vascular aging in patients with moderately decreased GFRs. Instead, some other undetermined factor(s) may be involved in modulating enzymatic activity.     

Prospective study of changes in arterial stiffness among kidney-transplanted patients

Background

Chronic kidney disease is one of the main risk factors for cardiovascular disease. Changes in stiffness parameters can predict the higher risk of the development of cardiovascular disease.

Methods

Cadaveric donor kidney transplant patients (n = 184) were followed in a cross-sectional single-center study. Arterial stiffness parameters were measured by arteriography. We analyzed the correlation between stiffness parameters and immunosuppressive therapy, the main operation parameters, patient age, elapsed time since transplantation, carotid artery stenosis, and septual wall thickness. We enrolled 24 patients in a 3-year longitudinal study to analyze changes in stiffness parameters.

Results

Our cross-sectional study showed pulse wave velocity (PWV) to be significantly related to the age of the patient (P = .0001; r = 0.41). There was no significant correlation between the stiffness parameters and type or dosage of immunosuppressive drugs and number of transplantations. We noted significant correlations between pulse pressure (PP) and pulse wave velocity (PWV), and augmentation index (AI) (P = .01). Patients with abnormal PWV (>12 m/s) showed significantly higher systolic blood pressures, body mass indexes, PP, and AI (P < .01). Our 3-year longitudinal study revealed a significant elevation in PWV.

Conclusions

Improving endothelial function and prevention of atherosclerosis may help to reduce cardiovascular complications. Among chronic kidney disease patients, early transplantation is a possible way to prevent cardiovascular events. It is better to perform the transplantation at as early an age as possible.     

尿毒症血液透析患者乳酸脱氢酶水平变化

目的 探讨尿毒症血液透析患者乳酸脱氢酶变化及其临床意义.方法 纳入尿毒症未透析者、尿毒症透析者及正常健康人各15例,采用全自动生化分析仪分别检测血清血红蛋白、肌酐、尿素氮及乳酸脱氢酶水平.结果 尿毒症未透析患者血清乳酸脱氢酶水平较正常健康人明显升高(P＜0.05);尿毒症血液透析组患者透析后乳酸脱氢酶水平与透析前相比有升高,但差异无统计学意义(P＞0.05).结论 尿毒症未透析患者体内乳酸脱氢酶水平的升高无器官特异性,血液透析改变了尿毒症患者体内乳酸脱氢酶环境,乳酸脱氢酶有可能作为评价血液透析充分性的观察指标.     

Parathyroid hormone and bone metabolism in kidney-transplanted patients

BACKGROUND: Decreases in bone mass and increased susceptibility to fractures are well-recognized complications in organ transplants. SUBJECTS AND METHODS: We performed a cross-sectional study on 60 patients (40 males, 20 females, mean age 43.2 +/- 1.06, SE range 22 - 70) who underwent kidney transplantation (KTX) 55.6 +/- 4.5 months before. Blood and 24-hour urine samples were analyzed for the main parameters of mineral metabolism, and also for osteocalcin (BGP), bone alkaline phosphatase (b-ALP, urine N-telopeptid (u-NTx) and urine galactosyl-hydroxylysine (u-Ghyl). DEXA scan of the lumbar spine (LS) and proximal femur (PF) and ultrasound determination of the heel (stiffness) was also performed. RESULTS: T-score values for bone density (BD) were 2.14 +/- 0.11 SD's for LS, -2.56 +/- 0.09 for PF and 2.49 +/- 0.15 for stiffness. There were 29 peripheral fractures in 16 patients. The rate of fractures before KTX were 0.0011 per patient/year and 0.0005 after transplantation (p < 0.02). When expressed as number of SD's with respect to normal controls, BGP (1.48 +/- 0.23), b-ALP (0.95 +/- 0.19), u-NTx excretion correlated negatively with BD at the femoral neck (p < 0.02) and trochanter (p < 0.03). Cumulative steroids intake were negatively correlated with b-ALP positively (p < 0.05). Current CsA was positively correlated with b-ALP (p < 0.001). Both cumulative steroid (p < 0.02) and CSA (p < 0.01) intakes were negatively correlated with BD at Wards triangle. CONCLUSIONS: Our data demonstrate an important bone depletion at each stage KTX. PTH plays a major role in the observed increase in bone turnover, exacerbating the negative effects on the bone on immunosuppressive treatment. Glucocorticosteroid therapy is an important risk factor for osteoporosis in this setting also.     

Hypochlorous acid and low serum paraoxonase activity in haemodialysis patients: an in vitro study.

BACKGROUND: Serum paraoxonase 1 (PON1) is an oxidant-sensitive enzyme associated with high-density lipoprotein (HDL) that inhibits the atherogenic oxidation of low-density lipoprotein (LDL). In haemodialysis patients, production of reactive oxygen species, such as hypochlorous acid (HOCl) and hydrogen peroxide, is increased and serum PON1 arylesterase is abnormally low. We have examined the effect of HOCl and the uraemic milieu on serum PON1 arylesterase activity and the ability of HDL to inhibit LDL oxidation in vitro. METHODS: Serum was incubated with HOCl, hydrogen peroxide and products of HOCl reaction with excess cysteine, lysine and taurine and then serum PON1 arylesterase and serum protein tryptophan fluorescence were measured. The ability of plasma HDL fractions isolated by a dextran-sulphate method, to protect LDL from mild oxidation in air, was determined by a fluorimetric method using oxidation of 2,7-dichlorofluorescein (DCFH). RESULTS: Incubation of healthy serum with HOCl in the range 6.5-32.9 mmol/l resulted in a linear decrease in serum PON1 arylesterase activity to 40% of that without HOCl and a parallel decrease in protein tryptophan fluorescence. The HOCl-induced decrease in serum PON1 activity was completely removed by reaction of HOCl with a 2.7-fold excess of alpha-amino acids but not taurine. In serum incubated for 1 week, the decrease in serum PON1 activity was significantly (P = 0.04) less while the increase in protein fluorescent advanced glycation end-products was significantly larger (P = 0.01) in haemodialysis patients compared with healthy subjects. The mean decrease in mild oxidation of LDL was not significantly different on addition of HDL-rich fractions from haemodialysis patients (100 +/- 6%, n = 7) and healthy subjects (95 +/- 6%, n = 7) or on addition of the HDL-rich fraction from plasma treated with 0.95 mmol/l HOCl (95%) and control HDL (96%). The fraction rich in HDL and other high molecular weight compounds from plasma that had been incubated with increasing HOCl concentrations up to 1.9 mmol/l significantly (P = 0.001) increased (471%) the oxidation of DCFH. CONCLUSIONS: These results suggest that high concentrations of HOCl that severely oxidize serum proteins and tryptophan residues in the active site of PON1 are required to decrease PON1 arylesterase activity in serum. In haemodialysis patients, overproduction of HOCl that leads to high concentrations of severely oxidized proteins and increased oxidants in plasma might also contribute to low serum PON1 arylesterase activity, but does not appear to impair the ability of an HDL molecule to protect LDL from mild oxidation.     

Fish oil and cyclosporin A-induced renal hypoperfusion in kidney-transplanted patients

BACKGROUND.: Dietary supplementation with fish oil has been said to improverenal function in cyclosporin A (CsA)-treated subjects. METHODS.: Renal function and the acute renal haemo-dynamic and tubularresponse to an oral CsA-dose (3 mg/kg) were investigated beforeand after 12 weeks of fish oil supplementation (6 g/day) in12 low-dose CsA-treated kidney-transplanted patients (s-creatinine,124 ± 24 µmol/l, mean ± SD). After an overnightfast, ten 1-h renal clearance periods were performed, two periodsbefore and eight after CsA-ingestion. An additional controlclearance study without CsA intake was performed in six subjects. RESULTS.: Fish oil did not change baseline values of the effective renalplasma flow (ERPF) or the glomerular filtration rate (GFR).Compared to the control study, CsA decreased GFR and ERPF significantlyon aver-age 20 ± 3% (P<0.01) and 23 ± 3% (P<0.01)respectively, 4–6 h after peak CsA blood concentrationwith no additional effect of fish oil. CsA also significantlydecreased the renal clearance of lithium, used as an index ofproximal tubular outflow, with no impact of dietary fish oil. CONCLUSION.: Fish oil supplementation had no effect on baseline renal functionor CsA-induced hypoperfusion in stable renal transplant recipientstreated with a low maintenance dose of CsA.     

尿毒症患者心脏结构的改变与甲状旁腺素关系的探讨

目的 探讨尿毒症患者心脏结构的改变与全段甲状旁腺素之间的关系.方法 将119例尿毒症患者分为血液透析组61例、非血液透析组58例,比较2组室间隔厚度、左心室后壁厚度、射血分数、左心室心肌重量指数及全段甲状旁腺素水平.结果 血液透析组左心室肥厚48例,非血液透析组左心室肥厚39例,2组室间隔厚度、左心室后壁厚度明显增厚,无明显差异.血液透析组左心室收缩功能不全5例,非血液透析组左心室收缩功能不全1例.2组全段甲状旁腺素较正常人群（7～53 pg/ml）均明显升高,血液透析组高于非血液透析组.血液透析组左心室心肌重量指数高于非血液透析组.2组全段甲状旁腺素与室间隔厚度、左心室后壁厚度、左心室心肌重量指数呈正相关.结论 尿毒症患者血全段甲状旁腺素升高是影响左心室结构与功能的重要因素之一.     

Oxidative stress and TGFbeta in kidney-transplanted patients with cyclosporin-induced hypertension. Effect of carvedilol and nifedipine

Cyclosporin is a powerful stimulator of oxidative stress signaling, leading to TGFbeta production, NO degradation, endothelial dysfunction, hypertension and post-transplant nephropathy. Carvedilol, alpha1-beta-blocker with strong antioxidant activity, may interfere with this chain of events. Therefore, we measured monocyte ecNOS, TGFbeta and heme oxygenase-1 (HO-1) mRNA level and plasma nitrite/nitrate, 3-nitrotyrosine, an estimate of peroxynitrite, and total plasma antioxidant power in kidney-transplanted patients with post-transplant hypertension, before and after treatment with carvedilol, 25 - 50 mg o.d. orally for 4 months (n = 15). The dihydropyridine calcium channel blocker nifedipine (n = 10) was used as comparator antihypertensive drug. Blood pressure fell to a similar extent with both drugs. Carvedilol increased plasma antioxidant power and HO-1 mRNA and reduced 3-nitrotyrosine and TGFbeta mRNA levels, while the same was not observed with nifedipine. Monocyte ec NOS mRNA levels and plasma nitrite/nitrate were higher in the patients than in a normotensive healthy control group and were unaffected by either treatment. In conclusion, carvedilol reduces the oxidative stress and corrects the altered cellular signaling mediated by oxidative stress in CsA-induced post-transplant hypertension. Therefore, it may prevent long-term complications, such as endothelial dysfunction, fibrogenesis and post-transplant nephropathy by decreasing NO degradation and production of TGFbeta, a key fibrogenic cytokine, and by activating HO-1 production.     

Impaired renal function is associated with mortality in kidney-transplanted patients

Introduction

To date, only a few, at times conflicting, reports suggested that renal function and mortality are associated in kidney-transplanted patients. In our prevalence cohort study, we tested the hypothesis that renal function is associated with mortality in transplanted patients.

Methods

Data from 985 transplanted patients were analyzed. Socio-demographic parameters, laboratory data, medical and transplant history, type of immunosuppression and estimated glomerular filtration rate were tabulated at baseline. Data on 5-year outcome were collected prospectively.

Results

In multivariate Cox proportional hazard models, the estimated glomerular filtration rate measured at baseline significantly predicted mortality [hazard ratio (HR)_{for each 10 ml/min decrease} = 1.271; 95% confidence interval (CI): 1.121–1.440] after adjustment for several covariables. Additionally, in multivariate Cox proportional hazard models, chronic kidney disease stage 4–5 (HR = 2.678; 95% CI: 1.494–4.802) significantly increased the mortality hazard compared to chronic kidney disease stage 1–2.

Conclusions

Renal function is significantly and independently associated with mortality over 5 years in kidney-transplanted patients among whom mycophenolate mofetil use was very prevalent.     

Reversible MRI changes in a patient with uremic encephalopathy.

A 19-year-old patient on chronic ambulatory peritoneal dialysis experienced severe neurologic disturbances caused by uremia. Increased signal intensity was seen bilaterally in the cortical and subcortical areas of the occipital and parietal lobe on cranial magnetic resonance imaging (MRI). Insufficient peritoneal dialysis efficacy was documented and the patient was switched from peritoneal to hemodialysis. Cranial MRI indicated a marked regression of the lesions to nearly normal, confirming the diagnosis of uremic encephalopathy.     

Serum guanidino compound levels and clearances in uremic patients treated with continuous ambulatory peritoneal dialysis

Guanidino compounds are increased in uremia and have been implicated as uremic toxins. The serum concentrations of 13 guanidino compounds and the clearances of 10 guanidino compounds were determined in 15 steady-state uremic patients treated with continuous ambulatory peritoneal dialysis. Guanidino compounds were determined using liquid cation-exchange chromatography with a sensitive fluorescence detection method. Standardized dialysis procedures were performed, including an overnight and a 3-hour dwell period. Guanidino compound levels did not significantly differ at the end of an overnight or a 3-hour exchange, indicating a steady-state blood chemistry for these substances in chronic ambulatory peritoneal dialysis. High levels were found for guanidinosuccinic acid, creatinine, guanidine and methylguanidine, while creatine and homoarginine levels were lower than in controls. Guanidinosuccinic acid, creatinine and methylguanidine reached levels associated with toxic effects in vitro. Significantly different clearances were found ranging from 4.02 +/- 1.08 ml/min for arginine to 7.94 +/- 2.76 ml/min for creatine during a 3-hour exchange.