Paraoxonase 1 192 and 55 polymorphisms in nephrotic children

The association between PON1 gene polymorphisms (Q192R and L55M) and nephrotic syndrome in Iraqi children

Background: The role of paraoxonase 1 enzyme (PON1) and its single nucleotide polymorphisms (SNPs) in children with nephrotic syndrome (NS) has been reported previously in different ethnic and racial groups with divergent results. The human PON1 gene contains two coding region polymorphisms leading to two different PON1 isoforms. Objectives: The aim of the present study was to find out the association between the PON1 (Q192R and L55M) polymorphisms and their relation with serum PON1 activity as well as lipid profile tests (total cholesterol, TC; triglycerides, TG; high-density lipoprotein cholesterol, HDL-c; and low-density lipoprotein cholesterol, LDL-c) in children with NS. Methods: This study included a total of 80 participants (40 with NS in the age group of 2-14 years and 40 age and sex-matched healthy controls). The PON1 enzyme activity and lipid profile tests were measured in serum samples of all included participants. The PON1 genotype was determined by PCR-restriction enzyme fragment length polymorphism (PCR-RFLP) for both PON1 alleles (192 and 55) SNPs. Results: Our findings showed that the mean levels of lipid profile tests (TC, TG, LDL-c) were significantly increased in patients when compared with healthy controls (p<0.05), while the HDL-c concentration was significantly decreased in patients than that of controls. Also, the patients had significantly lower concentrations of PON1 when compared with the controls regardless of the genotype Q192R and L55M polymorphisms. Moreover, the homozygous RR genotype for PON1 SNP 192 and MM homozygous genotype for PON1 SNP 55 were significantly frequent in patients when compared with the controls. Conclusions: Our results support that the presence of the homozygous RR genotype for PON1 SNP 192 and MM homozygous genotype for PON1 SNP 55 were significantly higher in patients compared with the controls.

Paraoxonase Activity and Lipid Profile in Paediatric Nephrotic Syndrome: A Cross-sectional Study

INTRODUCTION

Dyslipidaemia of Nephrotic Syndrome (NS) is known to be linked to oxidative reactions and atherosclerosis. Paraoxonase (PON1) has been implicated in the prevention of Low Density Lipoprotein (LDL) lipid peroxidation and also degrades biologically active oxidised lipids in lipoprotein.

AIM

The present study was taken up to assess PON1 levels in paediatric nephrotic syndrome and also to see if any correlation exists between lipid parameters and PON1.

MATERIALS AND METHODS

This study consists of Group 1 with 40 cases of NS in the age group of 2-14 years and Group 2 with 40 age and sex matched healthy controls. Lipid profile and paraoxonase activity was measured in serum samples of both the groups.

RESULTS

Statistical analysis by student's t-test showed that the mean levels of Total Cholesterol, Trigylycerides, LDL, and VLDL were significantly increased in Group 1 when compared to Group 2 (p <0.001). The mean levels of HDL were similar in both groups. The levels of PON1 were significantly lowered in Group 1 when compared to Group 2. Correlation studies showed no significant correlation between lipid profile and PON1.

CONCLUSION

Cases have atherosclerotic dyslipidaemia and significantly decreased PON1 activity. Decreased PON1 may lead to increased oxidation of LDL accelerating the process of atherosclerosis.

Paraoxnase1 Gene Polymorphism in Childhood Idiopathic Nephrotic Syndrome

BACKGROUND

Paraoxonase1 (PON1) is a serum enzyme bound to high-density lipoproteins with antioxidant properties. Molecular studies of PON1 revealed 2 polymorphic sites at amino acids 55 and 192 resulting in 2 different allozymes, the L and M-genotype at residue 55 and A and B at site 192, respectively. We have studied the association between PON1 gene polymorphisms and the minimal change nephrotic syndrome/focal segmental glomerulosclerosis (MCNS/FSGS) types of idiopathic nephrotic syndrome (INS) in Kuwaiti Arab children.

METHODS

The PON1 gene, 55 and 192 polymorphisms were analyzed in 50 children with INS (32 MSCN, 18 FSGS) and compared to 50 controls. Serum creatinine, albumin and lipids were measured in all subjects.

RESULTS

The LL genotype was detected in 50% of the INS patients compared to 48% of controls (p = 0.84). The heterozygous LM genotype was detected in 42% of INS patients compared 36% of controls (p = 0.68). The MM-genotype was detected in 8% of INS patients and 16% of controls (p = 0.35). The L-allele frequency in its homozygous and heterozygous forms was found in 71% of INS patients compared to 66% controls (p = 0.54). The L-allele frequency (LM and LL) was significantly higher in FSGS compared to MCNS patients (p = 0.0001) and when compared to controls (p = 0.0007). All patients and controls had the AA form of the 192 PON1 gene polymorphism.

CONCLUSION

Our data demonstrate a strong association between the L-allele of PON1 gene 55 polymorphism with FSGS in Kuwaiti Arab children with INS. PON1 genotyping can help in the early prediction of FSGS, which might guide clinicians to a better therapeutic approach.

Evaluation of paraoxonase activity in children with nephrotic syndrome

Background

It has been proposed that reactive oxygen species (ROS) is involved in the pathogenesis of various diseases. Paraoxonase, a high-density lipoprotein associated enzyme, prevents low-density lipoproteins from oxidation.

Objectives

The aim of the present study was to investigate the serum activities of paraoxonase-1 (PON-1), and aryleterase (ARE) as well as total antioxidant capacity (TAC) in children with nephrotic syndrome in acute and remission phase.

Patients and Methods

The study consisted of 20 patients in acute and remission phases and 23 healthy controls. PON-1 and ARE activities were determined spectrophotometrically using paraoxone and phenyacetate as substrate, respectively. TAC was measured using ferric reducing ability of plasma (FRAP).

Results

The levels of PON, ARE, and TAC were significantly lower in acute phase of nephrotic syndrome compared with the remission phase. The levels of PON, ARE and TAC increased in remission phase.

Conclusions

Our results revealed that the determination of paraoxonase activity might be a biomarker for responses to nephrotic syndrome treatment, which needs to be fully clarified.

Polymorphisms of the MDR1 and MIF genes in children with nephrotic syndrome

Oral steroid treatment is the first line of therapy for childhood nephrotic syndrome (NS). Nonetheless, some patients are resistant to this treatment. Many efforts have been made to explain the differences in the response to steroid treatment in patients with NS based on the genetic background. We have investigated single nucleotide polymorphisms of the MDR1 [C1236T (rs1128503), G2677T/A (rs2032582), and C3435T (rs1045642)] and MIF (G-173C, rs755622) genes in 170 children with NS. Of these children, 69 (40.6%) were initial steroid non-responders, and 23 (13.5% of total) developed chronic kidney disease. Renal biopsy findings, which were available for 101 patients, showed that 35 patients had minimal change lesion and 66 had focal segmental glomerulosclerosis. The frequencies of the MDR1 1236 CC (18.8 vs 7.2%) or TC (53.5 vs 43.5%) genotype and C allele (45.5 vs 29.0%) were significantly higher in the initial steroid responders than in the non-responders. Analysis of MDR1 three-marker haplotypes revealed that the frequency of the TGC haplotype was significantly lower in the initial steroid responders than in the non-responders (15.8 vs 29.0%). There was no association between the MIF G-173C polymorphism and clinical parameters, renal histological findings, and steroid responsiveness. These data suggest that the initial steroid response in children with NS may be influenced by genetic variations in the MDR1 gene.

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.