Russell Caccavello

Serum paraoxonase 1 (PON1) lactonase activity is lower in end-stage renal disease patients than in healthy control subjects and increases after hemodialysis.

Abstract Background: The mechanism of paraoxonase 1 (PON1) atheroprotective remains elusive. The lactonizing/lactonase activity of PON1 is gaining favor as the most significant in physiology. Methods: We studied 42 end-stage renal disease (ESRD) patients undergoing hemodialysis (HD) and 49 control subjects. We measured PON1 lactonase, arylesterase and triesterase activities by kinetic methods. Results: Serum lactonase activity was 11% lower in ESRD patients (p<0.0001) and did not correlate with high-density lipoprotein (HDL) cholesterol when controlling for confounders. Lactonase activity was significantly higher after dialysis. Using a repeated measure-ANOVA adjusted for the confounders (age, gender, total cholesterol, triglyceride and HDL cholesterol) we show that the changes in lactonase after dialysis were significant (p<0.0001). HD increases lactonase activity to levels indistinguishable from those of control subjects. In simple linear regression analyses we showed a significant inverse correlation between changes in lactonase and those of creatinine by dialysis (r=–0.339, p=0.028). Conclusions: ESRD patients maybe more susceptible to lipid peroxidation and to protein homocysteinylation than healthy subjects due to the decreased activity of lactonase. A lower serum lactonase activity would be coupled with delayed catabolism of oxidized phospholipids in low-density lipoprotein and oxidized macrophages, and with greater protein homocysteinylation, accelerating atherogenesis. One mechanism for lower lactonase activity in ESRD patients may be inhibition by uremic toxins and oxidative stress. The pathophysiology of reduced lactonase activity in uremia and the beneficial effects of HD need further investigation.

Enzymatic assessment of paraoxonase 1 activity on HDL subclasses: a practical zymogram method to assess HDL function.

BACKGROUND We developed a practical method for analysis of PON-1 enzymatic activity in HDL subclasses. METHODS The assay uses 4-12% polyacrylamide gradient gels, phenylacetate as substrate coupled with densitometric phenol detection using 4-aminoantipyrine. The measurement PON-1 activity in situ across the HDL subclasses has a strong correlation with the kinetic microplate assay for total PON-1 activity, r=0.91, p<0.001. RESULTS The same HDL-C level, healthy subjects (n=33) display a large difference in the ratio of PON-1 activity in small vs. large HDL. Since PON-1 activity is larger in HDL(3) we propose that this difference has a potent predictive value for clinical risk assessment and therapeutic choice. Our method also offers the advantage of assessing the distribution of up to six different HDL apolipoproteins in the same gel after transfer. CONCLUSIONS We seek to further dissect the cause of a different distribution of PON-1 activity in HDL subclasses by employing this method that permits practical, inexpensive analysis of antioxidant function of HDL subclasses and has the potential for application in clinical chemistry and to shed some light on the importance of PON-1 distribution.

Influence of Physical Activity Intervention on Circulating Soluble Receptor for Advanced Glycation end Products in Elderly Subjects

Background Inflammation, often accompanied by oxidation, caused by advanced glycation end products (AGEs) may be quenched by the soluble receptor for AGEs (sRAGE). The present study aimed to investigate the influence of physical activity on circulating sRAGE, and the association between changes of circulating sRAGE and paraoxonase1 (PON1) activity (as an antioxidative enzyme) in a physical activity intervention study on an elderly subject cohort. Methods Serum sRAGE, PON1 activity and cardiometabolic variables were measured in 30 community-dwelling asymptomatic Japanese volunteers (15 men/15 women, mean age 65 years) in the pre- and post-phase of a 6-month interventional program designed to increase physical activity. Results The body mass index and sRAGE levels (1103 ± 496 to 1030 ± 437 ng/L, P < 0.05) were significantly reduced during the intervention period. In addition, the change of sRAGE was significantly and inversely correlated with that of PON1 activity, independent of the other cardiometabolic variables (β = - 0.511, P < 0.01). Conclusions This study showed a reduction of sRAGE levels, and an inverse correlation between sRAGE and PON1 activity, after the intervention study increasing physical activity on an elderly population. These findings represent a modest but significant modulation of sRAGE by this type of exercise intervention, which warranted future studies on the clinical relevance of sRAGE changes in physical activity. Keywords AGEs; RAGE; Paraoxonase1; Exercise; Atherosclerosis

Influence of ezetimibe monotherapy on ischemia-modified albumin levels in hypercholesterolemic patients.

Ischemia-modified albumin (IMA) is considered to be a novel biochemical marker for ischemic and atherosclerotic conditions. This study aimed to investigate the influence of ezetimibe monotherapy on circulating IMA levels in hypercholesterolemic patients. A total of 31 patients (mean age 65.7 years) received 10 mg of ezetimibe daily during a 12-week treatment period. The levels of low-density lipoprotein cholesterol and IMA were significantly reduced after ezetimibe treatment. The adjusted regression analyses revealed that the changes in the IMA levels were not significantly correlated with those of the other atherosclerotic risk markers, such as body mass index, blood pressure, glucose and lipid panels. The significant reduction of the IMA levels following ezetimibe treatment, which was independent of the reduction of low-density lipoprotein cholesterol levels, suggests that ezetimibe may improve the oxidative stress burden in hypercholesterolemic patients.

Low protective PON1 lactonase activity in an Arab population with high rates of coronary heart disease and diabetes

BACKGROUND Recent studies showing that high density lipoproteins (HDL) can effect plaque regression indicate that recent trial failures do not exclude an atheroprotective role of HDL. Instead, they highlight differences between HDL function and measured HDL-cholesterol (HDL-C). PON1 is one key functional activity of HDL. Urban Palestinians have lower HDL-C and a higher incidence and mortality of coronary heart disease than those of Israelis. We hypothesized that the cardioprotective PON1 lactonase and arylesterase activities and PON1 functional genotype may differ between Palestinians and Israelis. METHODS We measured PON1 activities in a cross-sectional population-based study of Palestinian (n=960) and Israeli (n=694) residents in Jerusalem, 1654 participants in all. RESULTS Palestinians had high prevalences of obesity and diabetes and low mean concentrations of HDL-cholesterol (0.97 mmol/l in men and 1.19 mmol/l in women). Lactonase and arylesterase activities were lower by 10.8% (p=1.2∗10(-14)) and 2.7% (p<0.0005), respectively, in Palestinians as compared to Israelis. The functional genotype distribution, demonstrated by plotting paraoxonase vs lactonase activities, showed a modest between-group difference (p=0.024), with 12.1% RR in Palestinian Arabs vs 8.4% in Israeli Jews, but no overall difference in allele frequencies. Lactonase correlated inversely with age (Spearmans rho=-.156), weakly with BMI (-.059), positively with HDL-C (.173) and non-HDL-C (.103), but was not associated with triglycerides or fasting glucose. Palestinians showed consistently lower lactonase activity in logistic regression models adjusted for multiple covariates and for functional genotype (odds ratios of 1.81 and 1.98, respectively, for the lower fifth vs the upper 4 fifths of lactonase activity p<0.0001). CONCLUSION We showed a lower physiologically-significant lactonase PON1 activity in an Arab population, a finding consistent with the high cardiovascular and diabetes risk of Palestinians.

Circulating soluble receptor for advanced glycation end products is inversely correlated to oxidized low-density lipoproteins in asymptomatic subjects.

Objective: There is growing evidence that circulating soluble receptor for advanced glycation end products (sRAGE) exerts antiatherogenic effects as a decoy receptor that abolishes RAGE signalling. A previous study reported that oxidized low-density lipoprotein (oxLDL) can be one of the RAGE ligands. The present cross-sectional study investigated the clinical association between sRAGE and oxLDL in humans. Methods: Serum levels of the conventional atherosclerotic risk factors, sRAGE and malondialdehyde-modified low-density lipoprotein (MDA-LDL) were analysed in asymptomatic subjects; MDA- LDL was measured as a biomarker of oxLDL. Results: Mean serum levels of sRAGE and MDA-LDL were 1101 ng/l and 57.6 IU/l, respectively, in 33 subjects of mean age 65 years. Simple linear regression analysis showed a significant inverse correlation between sRAGE and MDA-LDL. Stepwise multiple linear regression analysis confirmed MDA-LDL to be independently, significantly and inversely correlated with sRAGE. Conclusions: An independent, significant and inverse correlation was shown to exist between circulating levels of sRAGE and oxLDL (MDA-LDL), which suggests that part of the antiatherosclerotic effects of sRAGE may be related to oxLDL quenching.

Activation of paraoxonase 1 after hemodialysis is associated with HDL remodeling and its increase in the HDL2 fraction and VLDL.

BACKGROUND Paraoxonase 1 (PON1) activity is lower in renal failure patients. We hypothesize that part of the salutatory effect of hemodialysis on PON1 activity that we have previously found is due to HDL remodeling and shift of PON1 among HDL particles. METHODS A total of 42 patients (18 females and 24 males, 63 ± 12 yr) on long-term HD, with a mean dialysis course of 6.4 yr (range 1-19 yr), were recruited. PON1 arylesterase and lactonase activities, PON1 and apolipoprotein distribution in HDL subclasses were measured by gel gradient electrophoresis and western blotting. RESULTS The 3 different activities of PON1 we measured were significantly lower in patients as compared to control subjects; lactonase by 11%, triesterase by 19% and arylesterase by 20%, p<0.01. HDL increased slightly by 4.6%. LDL increased by 13% and VLDL decreased by 30%. These data are compatible with enhanced lipolysis of VLDL that is transformed into LDL. VLDL-PON1 activity increases significantly by 60%. PON1 activity increases by 16% in HDL2 whereas by this approach we could determine a 10% increase in the total area under the curve corresponding to total HDL. Changes in total lactonase activity were associated with changes in VLDL-PON1 and HDL2. In parallel with PON1 activation and shifts among particles, there are significant changes in apoE which increases notably in HDL2, paralleling the changes in PON1. No significant changes in apoAI or apoA-II the main structural HDL apolipoproteins were apparent after dialysis. CONCLUSIONS HD produces an activation of PON1 that can be predicted in part (30%) by efficiency of dialysis and in part (25%) by PON1 shifts to HDL2or VLDL (p<0.01). The removal of inhibitors and the change in the environment of PON1 in the micro-heterogeneity of HDL subclasses optimizes PON1 activity.

Serum aspirin esterase is strongly associated with glucose and lipids in healthy subjects: different association patterns in subjects with type 2 diabetes mellitus

BackgroundAspirin esterase (AE) activity can account for part of aspirin pharmacokinetics in the circulation, possibly being associated with the impairment of aspirin effectiveness as an inhibitor of platelet aggregation.AimsThe study was aimed at investigating the correlations of serum AE activity with cholinesterase (ChE) and metabolic variables in healthy subjects in comparison to subjects with type 2 diabetes mellitus (T2DM).MethodsIn cardiovascular disease-free T2DM subjects and healthy controls, the AE activity levels and/or the correlation patterns between AE and the other variables were analyzed.ResultsNeither AE nor ChE activities were higher in the subjects with T2DM. Serum AE activity strongly correlated with ChE as well as glucose/lipids variables such as total cholesterol and triglyceride in healthy subjects, while the correlations between AE and glucose/lipids variables were not present in T2DM subjects.ConclusionsThese data may reflect the pathophysiological changes between healthy and T2DM subjects. Our data may thus provide the basis for future studies to unravel the mechanisms.

Correlation between Ischaemia-Modified Albumin and Intermediate-Density Lipoprotein in Haemodialysis Patients with End-Stage Renal Disease

This study investigated the association between ischaemia-modified albumin (IMA), a biomarker of cardiac ischaemia, and increases in the levels of intermediate-density lipoprotein (IDL), an atherogenic particle that can cause oxidative stress, in haemodialysis patients with end-stage renal disease (ESRD). Fasting levels of serum IMA and lipids/lipoproteins were analysed in 15 patients and 15 healthy control subjects. There was a close positive correlation between IMA and IDL levels in ESRD patients but no significant correlation between IMA and lipids/lipoproteins in control subjects. This suggests a possible link between the characteristic dyslipo-proteinaemia found in ESRD and levels of IMA and, if confirmed in studies with larger sample sizes, may lead to further studies on the potential of the relationship between IMA and IDL as a biomarker in haemodialysis patients with ESRD.

Paraoxonase 1 lactonase activity and distribution in the HDL subclasses in the cord blood

Abstract Objectives Paraoxonase 1 (PON1) is a lactonase with important antioxidant and immunoprotective properties. We hypothesized that PON1 lactonase activity, PON1, and high-density lipoprotein (HDL) subclasses distribution are different in neonates than in adults. Material and methods We studied 83 healthy term neonates (34 males and 49 females) who were born by spontaneous, uncomplicated vaginal delivery. The study also included 17 paired maternal blood samples as well as 20 non-pregnant women collected for comparison. Total and free PON1 lactonase and arylesterase activity, HDL subclasses, PON1, and apolipoprotein distribution in the subclasses were assayed. Results PON1 arylesterase activity in the cord blood represented 37% ± 4 of the maternal activity, whereas the PON1 lactonase activity amounted to only 23% ± 5 of the maternal activity. The free arylesterase and lactonase activities were higher in the cord blood by 16 and 36%, respectively. There is a 65% lower HDL2b PON1 in the cord blood than in the maternal serum. When the Lipoprint HDL subclasses were assayed, the neonates showed a larger content (52% higher) of very large HDL as well as a characteristic peak in the middle-sized HDL5 which is unremarkable in the mothers. Conclusion The novel findings of this study are that the neonates have lower PON1 lactonase activity, higher free PON1, different distributions of PON1 in the HDL subclasses as compared with their mother and adults as well as a distinctive HDL subclass lipid profile. Our data also suggest that the neonate HDL is enriched with an intermediate-sized (and/or less charged HDL) that is also rich in active PON1.