Polymorphisms of pon1 and pon2 genes in hemodialyzed patients.

OBJECTIVES: Q192R, L55M and -108C>T polymorphisms of pon1 gene affect PON1 paraoxonase activity while S311C polymorphism of pon2 gene might be associated with coronary heart disease. The aims of this study were to determine the frequencies of Q192R, L55M, -108C>T and S311C polymorphisms in hemodialyzed patients and to examine the relationship between pon1 gene polymorphisms and PON1 paraoxonase activity in those patients. DESIGN AND METHODS: The study included 238 control subjects and 263 hemodialyzed patients. RESULTS: PON1 paraoxonase activity was lower in patients. Genotype frequencies were different between two compared groups only for L55M polymorphism, with control group having higher frequency of MM genotype. Polymorphisms of pon1 gene were associated with significant variation in PON1 paraoxonase activity in both study groups. CONCLUSION: Our results suggest that Q192R, L55M and -108C>T polymorphisms are not by itself the causal factors leading to the lower PON1 paraoxonase activity in hemodialyzed patients.

[Significance of participation in programs of external quality assessment in molecular diagnostic--our experience]. / Znacenje sudjelovanja u programima vanjske procjene kvalitete u molekularnoj dijagnostici--vlastita iskustva.

Harmonization of molecular diagnostic tests in laboratories in the Republic of Croatia has only just started. According to laboratory accreditation standard ISO 15189 participation in external quality assessment (EQA) schemes or programs is a prerequisite and support tool for clinical laboratory accreditation process. As there are no national quality assurance schemes yet, an European external quality assessment (EQA) scheme or program should be found. Because of variation in the molecular diagnostic test performance of clinical laboratories across Europe, EQA is recognized as a system whereby a set of reagents and techniques are assessed by an external provider making inter-laboratory performance comparability possible through already integrated recommendations and practice guidelines of molecular diagnostic test performance. Today, wide range of various EQA schemes and programs already in action have been available and most of them began within the last ten years. This paper is therefore intended to present and summarize the four-year EQA activities in the Institute of Clinical Chemistry, Merkur University Hospital, in three different international EQA schemes: United Kingdom National External Quality Assessment Scheme (UK NEQAS), the European Molecular Genetic Quality Network (EMQN) and Multi-National External Quality Assay program (EQUAL- qual)) and to point out their educational role in standardization of laboratory performance of any test intended for patient testing. from a laboratory point of view.

Effect of non-genetic factors on paraoxonase 1 activity in patients undergoing hemodialysis.

OBJECTIVES: Hemodialyzed patients have lower paraoxonase 1 (PON1) activity. Higher mortality risk from cardiovascular disease observed in these patients could be due to the low antiathetrogenic activity of PON1. Understanding the mechanism that causes lower PON1 activity could provide the possibility for modulation of enzyme activity in purpose of preventing and/or decreasing development of atherosclerosis. DESIGN AND METHODS: 87 healthy individuals and 71 hemodialyzed patients were enrolled in this study. RESULTS: Hemodialyzed patients had reduced PON1 paraoxonase and arylesterase activity, concentrations of HDL, HDL(3) and HDL(2) and concentrations of free thiol groups. Distribution of HDL subfractions and distribution of PON1 phenotypes as well as concentrations of MDA were not different between two study groups. In the in vitro experiment high concentrations of urea, creatinine, uric acid and addition of patient's sera ultrafiltrate did not significantly affect PON1 paraoxonase activity. CONCLUSION: Decreased HDL concentration as well as lower PON1 concentration (shown indirectly by the enzyme arylesterase activity) might contribute, at least partly, to the reduced PON1 activity observed in hemodialyzed patients. Decreased concentration of free thiol groups in sera suggest that free thiol group (Cys284) in PON1 might also be oxidized, which can affect PON1 activity.

Applicability of common reference intervals for serum creatinine concentrations to the Croatian population.

BACKGROUND: In accordance with an ongoing activity for worldwide harmonization based on traceability in laboratory methods, the goal of this study was to validate the applicability of recommended "common" reference intervals for serum creatinine concentrations using a specific enzymatic method to the Croatian population. METHODS: The reference group consisted of 240 healthy subjects (120 males and 120 females), between 18 and 74 years of age (median 57 years), who were selected in accordance with the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) recommendations. Creatinine in serum was measured using the creatinine enzymatic assay (Olympus OSR61204) that was standardized to the isotopic dilution mass spectrometry (IDMS) method and National Institute of Standards and Technology (NIST) Standard Reference Material (SRM) 967. In addition, creatinine was measured using a kinetic Jaffe method (Olympus OSR6178) standardized to NIST SRM 909b level 2 standard. RESULTS: Method comparison between enzymatic creatinine (x) and the Jaffe kinetic method (y) gave the following P/B equation for the entire group (n=240): y=1.00x+17.00; r=0.968. Reference intervals for serum creatinine (central 95th percentiles) obtained using the enzymatic creatinine method ranged from 54 to 107 micromol/L for males and from 50 to 93 micromol/L for females. The IFCC recommended common reference intervals for global applications are 64-104 micromol/L and 49-90 micromol/L for males and females, respectively. CONCLUSIONS: Comparability of obtained results confirmed the applicability of recently recommended "common" reference intervals to the Croatian population for all laboratories measuring serum creatinine concentrations using enzymatic methods traceable to the IDMS method and NIST SRM 967.

Effect of splenectomy and autologous spleen transplantation on the serum platelet-activating factor acetylhydrolase (PAF-AH) activity and acute phase response (APR) in a porcine model.

The aim of this study was to evaluate the inflammatory response after total splenectomy and spleen autotransplantation in a porcine model by measuring serum platelet-activating factor acetylhydrolase activity, C-reactive protein and albumin concentrations. Nineteen piglets were used in the experiment. After induction of anesthesia, animals were randomly divided into three groups: sham-operation with spleens intact (n = 6), total splenectomy (n = 6), and splenic autotransplantation (n = 7) with small fragments of the spleen autotransplanted into the greater omentum. The blood samples were taken just before surgery and on day 1st, 5th, 12th, 26th and 40th postoperatively. PAF-AH activity, CRP and albumin concentrations were assayed in the sera. After total splenectomy, PAF-AH activity was significantly increased on day 5th, while there was no significant increase after spleen autotransplantation or the sham-operation. CRP was significantly increased after surgery in all experimental groups. Albumin was significantly decreased after surgery from day 5th until day 40th in splenectomized and autotransplanted pigs. Increased PAF-AH activity after splenectomy and spleen autotransplantation might be attributed to inflammatory conditions due to the loss of splenic tissue and trauma. Time-course increase of CRP, in all groups after surgery suggests post-injury inflammatory response due to tissue lesion during operation.

Toxicological assessment of P-9801091 plant mixture extract after chronic administration in CBA/HZg mice--a biochemical and histological study.

Acute, subchronic and chronic effects of the P-9801091 plant mixture extract at a dose of 20 mg/kg body mass were assessed in serum of healthy CBA/HZg mice at 24 hours, 7 days, 3 months and 6 months of treatment (experimental group), and compared with the values obtained in the control group of untreated healthy CBA/HZg mice. The P-9801091 plant mixture extract is an antihyperglycemic preparation containing Myrtilli folium (Vaccinium myrtillus L.), Taraxaci radix (Taraxacum officinale Web.), Cichorii radix (Cichorium intybus L.), Juniperi fructus (Juniperus communis L.), Centaurii herba (Centaurium umbellatum Gilib.), Phaseoli fructus sine semine (Phaseolus vulgaris L.), Millefolii herba (Achillea millefolium L.), Mori folium (Morus nigra L.), Valerianae radix (Valeriana officinalis L.) and Urticae herba et radix (Urtica dioica L). Toxic effect of the P-9801091 plant mixture extract was assessed by the following biochemical parameters: urea, creatinine, aspartate aminotransferase (AST), alanine aminotransferase (ALT) and cholesterol. Also, histopathological examination of the kidneys, liver, spleen, pancreas, testes and lungs was performed. Results of biochemical testing performed at specified time points generally showed no statistically significant differences from control values, with the only exception of the catalytic concentration of AST in the experimental group measured on day 7, which was significantly increased as compared with the control group (p<0.05). Pathohistological examination including characteristic organ and tissue structure, and parenchyma relationship to the adjacent blood vessels and connective tissue in the examined organs revealed no major pathologic changes.

Bovine platelet-activating factor acetylhydrolase (PAF-AH) activity related to fertility.

Plasma platelet-activating factor acetylhydrolase (PAF-AH), the enzyme characterized by the association with plasma lipoproteins, degrades platelet-activating factor (PAF) as well as PAF-like oxidatively fragmented phospholipids produced during oxidative stress. Apart from pro-inflammatory properties, PAF is also related to reproductive processes and successful fertility. In order to get a better insight into the involvement of PAF-AH in the fertility of cows, the aim of the study was to determine the PAF-AH activity as well as the C-reactive protein, cholesterol and high density lipoprotein-cholesterol (HDL-C) in the serum of dairy cows throughout the pregnancy and lactation, as well as in infertile cows. The results showed that serum PAF-AH activity changes throughout pregnancy and lactation with a lower level during periparturient period. It is also found higher PAF-AH activity in lactating cows with reproductive disorders compared to high lactating cows without reproductive disorders. Strong correlation between PAF-AH activity and HDL-C concentration indicates that HDL could have considerable influence on PAF-AH activity in bovine plasma. CRP concentration was also lower during transition period suggesting that lactation might stimulate CRP synthesis in bovine. A higher CRP concentration in cows with reproductive disorders compared to fertile cows at the peak of lactation, demonstrates that milk production is not the only factor influencing CRP in cows. A significant correlation between PAF-AH activity and CRP level shows that both parameters could be influenced by reproductive status of dairy cows.

[Harmonization of laboratory medicine in Croatia]. / Harmonizacija laboratorijske medicine u Hrvatskoj.

In order to harmonize laboratory results in the field of general medical biochemistry at the national level, analytical methods and analytical quality goals based on biological criteria together with common reference intervals were recommended. The following parameters are included: general biochemical parameters (metabolites and substrates, enzymes, electrolytes, microelements, proteins, lipids), routine urine and stool analysis and laboratory haematology and coagulation. The main purpose of external quality control in medical biochemical laboratories is to ensure independent and objective evaluation of laboratory test results in order to promote harmonization and achieve a high degree of interlaboratory comparability. The recommended reference intervals were produced on a representative sample group of urban population in Croatia for school children, adolescents and adults. For pediatric population, reference intervals were recommended according to the literature data. The recommended laboratory methods and corresponding reference intervals in the field of general medical biochemistry have to be used in all medical biochemical laboratories in Croatia since January 1, 2005.

Paraoxonase/arylesterase in serum of patients with type II diabetes mellitus.

The aim of this study was to determine whether the paraoxonase (PON1) status, i.e. PON1 activities and phenotypes (AA, AB and BB), and its relationship with lipid status are different in patients with type II diabetes as compared to healthy population. Diabetic group comprised 175 patients with type II diabetes mellitus (94 men and 81 women) who came to their regular control examination and took the oral glucose tolerance test. Patients with type II diabetes mellitus diagnosis for 12 years on average were on peroral antidiabetics, or insulin or diet, and 3 patients had no therapy prescribed yet. Control group comprised 114 apparently healthy individuals (28 men and 86 women) who were not on any medication. The paraoxonase activity was measured with 2.0 mmol L(-1) paraoxon in the absence and in the presence of 1.0 mol L(-1) NaCl, and with 2.0 mmol L(-1) phenylacetate. Both activities were measured spectrophotometrically at 37 degrees C in 0.1 mol L(-1) Tris-HCl buffer, pH = 8.0, containing 2.0 mmol L(-1) CaCl(2). Sera of diabetic and control subjects were assigned to the paraoxonase phenotypes on the basis of the basal paraoxonase activity distribution. We assigned 45% sera of male and 49% sera of female diabetic patients, and 64% sera of both genders of the control group to the AA low activity phenotype. There were no differences in paraoxonase activities between the gender- and phenotype-matched diabetic and control groups. Enzyme activity against the phenylacetate was higher, and phenotype-dependent, only in diabetic patients. In contrast to AA phenotype individuals, total cholesterol and LDL-cholesterol in the female diabetic group and triglyceride concentration in the male diabetic group assigned to pooled AB and BB phenotypes were higher than in the corresponding controls. It follows from PON1 phenotype distribution that less antiatherogenic paraoxonase B allele is more frequent in type II diabetes mellitus than in the healthy population. Their lipid status is more atherogenic, which could indicate a risk of premature atherosclerosis.

Effect of acarbose on alanine aminotransferase and aspartate aminotransferase activities in the liver of control and diabetic CBA mice.

The purpose of this study was to examine the short-term effects of diet containing 0.1% (m/m) of acarbose in standard laboratory chow on specific liver enzyme activities: alanine aminotransferase (ALT) and aspartate aminotransferase (AST) in control and diabetic CBA mice. Diabetes was induced by intravenous injection of alloxan monohydrate in a dose of 75 mg kg(-1) mouse body mass seven days before the treatment with acarbose. There were four groups of CBA mice in the experiment: control (C) mice (n = 6) and diabetic (D) mice (n = 8) fed standard chow; control (C/A-100) mice (n = 8) and diabetic (D/A-100) mice (n = 8) fed standard chow containing 0.1% acarbose. Diabetes induced a decrease of the ALT catalytic activities to 69.6% of the control value. A similar level of decreased ALT catalytic activity was detected in the liver of control and diabetic mice fed chow containing 0.1% acarbose. No changes in the specific and total activities of AST in the liver of experimental groups were observed.

Enzyme activity and AGE formation in a model of AST glycoxidation by D-fructose in vitro.

Non-enzymatic glycation as the chain reaction between reducing sugars and free amino groups of proteins has been shown to correlate with physiological ageing and severity of diabetes. The process involves oxidative steps (glycoxidation). In this paper, the effect of D-fructose as a reactive sugar on aspartate aminotransferase (AST) as a model protein was monitored by measurements of the enzyme activity and formation of fluorescent advanced glycation end products (AGEs). Change in the AST activity was considered as a measure of the overall protein damage caused by glycation, and total AGEs and pentosidine represent, at least partly, the formation of glycoxidation products. Catalytic activity of AST in an incubation mixture containing D-fructose (50 mmol L(-1)), decreased compared to control values to 42% (p < 0.05) and to 11% (p < 0.05) on the 5th and on 21st day of incubation, respectively. In the presence of fructose, total fluorescent AGEs concentration was significantly higher since 5th day of incubation (110%, p < 0.05) and the fluorescent pentosidine concentration from 15th day of incubation (117%, p < 0.05) compared to control values, respectively. Catalytic activity of AST clearly and quantitatively demonstrated functional changes in the enzyme molecule caused by structural modifications initiated by fructose, while the evaluation of AGE formation and especially that of pentosidine by fluorescence measurement was less reliable.

Paraoxonase activity and concentration of indicators of lipids status in the serum of cardiac patients.

In this research, we measured the activity of paraoxonase (basal and activated) enzyme, and components of lipid status components (total cholesterol, LDL cholesterol, HDL cholesterol and Apo A I) in the serum of patients, undergoing bypass surgery. We also tested how the applied EKC affected changes of defined indicators. Measuring of all the given parameters was conducted prior to the operation, 90 minutes, 1.5 hour, 6 hours, 24 hours and 72 hours, on 29 patients (11 of them did undergo myocardium revascularization with the application of EKC, while the rest of them did not). Activity of paraoxonase (both basal and activated) changes significantly during the postoperative period, in relation to pre-operative values, p < 0.05. Total cholesterol concentration is reduced in both examined groups, regardless of the application of EKC. This trend is also accompanied by LDL cholesterol concentration. On the other hand, HDL cholesterol concentration during post-operative period does not indicate any significant statistical change in relation to pre-operative values, while we noticed difference with regard to EKC application, 90 minutes after surgery. This change of lipid status indicator is partly due to heparin, a stimulator of lipoprotein lipase that was applied during the surgery. Our conclusion is that lipid profile changes significantly after the bypass surgery, mostly regardless of the application of EKC.

Effect of different dialysis membranes on erythrocyte antioxidant enzyme levels and scavenger systems related to free hemoglobin in serum of hemodialysis patients.

The main objective of the present study was to analyze some aspects of the function and structure of erythrocytes with respect to hemodialysis membrane biocompatibility throughout the erythrocyte and serum antioxidant levels. The study included 36 hemodialysis patients (14 female and 22 male, age 22-79 years, median 55) treated at the Department of Nephrology and Dialysis, Split Clinical Hospital in Split, and 30 control subjects matched for age and sex. Hemodialysis was performed three times a week for 4 hours with cellulose diacetate (n = 17; 6 females and 11 males) or polysulfone (n = 19; 8 females and 11 males) membranes. The aim of the study was to assess the level of oxidative stress in these patients by measuring catalytic concentrations of superoxide dismutase and glutathione peroxidase in erythrocyte lysate and scavenger systems related to free hemoglobin in serum (haptoglobin, hemopexin and bilirubin). In comparison with control values, the mean catalytic concentrations of superoxide dismutase were increased and catalytic concentrations of glutathione peroxidase decreased in patients before hemodialysis irrespective of the membrane used. Immediately after hemodialysis with either membrane, the mean catalytic concentrations of superoxide dismutase returned to the control range, while those of glutathione peroxidase were still decreased compared to control values, without any significant difference between the cellulose diacetate and polysulfone membranes. The predialysis and postdialysis values of haptoglobin, hemopexin and bilirubin in patient sera were within the range of control values. Comparison of the cellulose diacetate and polysulfone membranes showed no significant differences in the erythrocyte content of antioxidant enzymes and the scavenger system related to free hemoglobin in serum before and after hemodialysis.