Inverse correlation of serum paraoxonase and homocysteine thiolactonase activities and antioxidant capacity of high-density lipoprotein with the severity of cardiovascular disease in persons with type 2 diabetes mellitus

Associations between myeloperoxidase and paraoxonase-1 and type 2 diabetes in patients with ischemic heart disease

BACKGROUND

The phrase "dysfunctional high-density lipoprotein" has been developed in the literature to describe the particle which loses its basic role- anti-oxidative and anti-inflammatory activity. In this porcess, the significance of enzymes- pro-oxidant myeloperoxidase (MPO) and antioxidant paraoxonase-1 (PON-1) from the perspective of HDL-C function has been noted.

AIMS

The objective of this study was to analyze the associations between two enzymes -MPO and PON-1 and type 2 diabetes (T2DM) in patients with ischemic heart disease (IHD).

METHODS

An observational cross-sectional study including 70 patients with IHD of whom 35 had also T2DM, and 35 had no T2DM. Laboratory tests (MPO, PON-1, fasting glucose, glycated hemoglobin, total cholesterol, triglycerides, high-density lipoprotein, low-density lipoprotein, and high-sensitivity C-reactive protein) were performed.

RESULTS

The study revealed a significant difference in the serum concentration of the enzymes between patients with IHD with and without T2DM. Our results showed increased MPO concentration levels in diabetic patients. The analysis also revealed that T2DM is independently associated with an increase in MPO levels. Simultaneously, a decrease in PON-1 levels was observed in patients with T2DM. The study also revealed that T2DM is independently associated with a decrease in PON-1 levels.

CONCLUSIONS

In patients with type 2 diabetes the profile of enzymes involved in high-density lipoprotein metabolism in patients with IHD is worse than in patients without T2DM. The increase in the levels of MPO, an enzyme with oxidative and atherogenic properties and on a decrease in PON-1 levels, an enzyme with antioxidant and atheroprotective properties is observed.

Effect of Moxibustion on Hyperhomocysteinemia and Oxidative Stress Induced by High-Methionine Diet

Objective

The aim of this study was to assess the effects of moxibustion on the animal model of oxidative stress and cardiovascular injury induced by high-methionine diet (2% methionine and 3.5% fat on the basis of ordinary maintenance feed) during 12 weeks.

Methods

53 mice were divided into four groups: mice in the Control group (n = 8), mice in the Met group (n = 8), mice in the Met group (n = 8), mice in the Met group (n = 8), mice in the Met group (

Results

Compared with the Met group, our results indicated that through moxibustion intervention, the content of serum Hcy and its intermediate metabolite SAH can be reduced to a certain extent, and SOD, HO-1, and ox-LDL can be increased.

Conclusion

This study showed moxibustion's ability to enhance the body's antioxidation and protect vascular endothelial function, thus playing an early role in the prevention and treatment of atherosclerosis.

Importance of paraoxonase 1 (PON1) as an antioxidant and antiatherogenic enzyme in the cardiovascular complications of type 2 diabetes: Genotypic and phenotypic evaluation

Oxidant-antioxidant imbalance is involved in the etiology of different diseases, including cardiovascular diseases (CVDs), liver disorders, kidney diseases, cancers and diabetes mellitus. Antioxidant enzymes play a key role in striking an oxidant-antioxidant balance. Moreover, paraoxonase 1 (PON1) is an antioxidant enzyme that binds with high-density lipoprotein (HDL) in the circulation, and antioxidant and antiaterogenic properties of this lipoprotein are significantly associated with PON1. Research suggests PON1 contributes to the pathogenesis of certain human diseases such as type 2 diabetes (T2D). The association between PON1 and T2D appear to be reciprocal so that the disease significantly decreases PON1 levels and in turn, the genetics of PON1 may have a role the risk of susceptibility to T2D. Several factors that reduce the activity and concentration of PON1 in patients with T2D include increased glycation and loss-of-function polymorphisms. The genotypic and phenotypic evaluations of PON1 are therefore crucial for assessing the risk of cardiovascular complications in these patients, and strategies for increasing or restoring PON1 levels are useful for reducing or preventing their cardiovascular complications as their main cause of mortality. The present review aimed at discussing and emphasizing the key role of PON1 in T2D as a silent and dangerous disease.

Paraoxonase 1 gene (Q192R) polymorphism confers susceptibility to coronary artery disease in type 2 diabetes patients: Evidence from case-control studies

Numerous published studies have investigated the relationship between the paraoxonase 1 (PON1) gene Q192R (rs662) polymorphism and the risk of coronary artery disease (CAD) in type 2 diabetes mellitus (T2DM) patients. However, the results are still conflicting and inconclusive. Potentially eligible articles were searched for in related databases. Odds ratios (OR) with 95% confidence intervals (CI) were used to estimate the associations. Subgroup analysis was performed based on ethnicity. Ten case-control studies were included. A significant increase in the susceptibility for CAD in T2DM patients was found in the allelic model (OR = 1.49, p < 0.001), homozygote model (OR = 2.47, p < 0.001), heterozygote model (OR = 1.47, p < 0.001), dominant model (OR = 1.64, p < 0.001), and recessive model (OR = 1.74, p = 0.001). In subgroup analysis by ethnicity, a significant increase susceptibility was found in Asian populations in the allelic model (OR = 1.39, p = 0.001), homozygote model (OR = 2.15, p = 0.002), heterozygote model (OR = 1.37, p = 0.006), recessive model (OR = 1.65, p = 0.012), and dominant model (OR = 1.54, p < 0.001). A similar significant increase in susceptibility was found in Caucasian populations in the allelic model (OR = 1.75, p = 0.002), homozygote model (OR = 3.39, p = 0.002), recessive model (OR = 1.98, p = 0.030), heterozygote model (OR = 1.64, p = 0.001), and dominant model (OR = 1.83, p < 0.001). The results suggest that the PON1 Q192R polymorphism is associated with a significantly increased risk of CAD in T2DM patients in both Asian and Caucasian populations.

Evaluation of Paraoxonase, Arylesterase, and Homocysteine Thiolactonase Activities in Patients with Diabetes and Incipient Diabetes Nephropathy

Background

The aim of this study is to examine the relationship among the changes in activities of paraoxonase (PON), arylesterase (ARE) and homocysteine thiolactonase (HTLase) enzyme having antioxidant properties and the development of diabetic nephropathy (DN), one of the most common complications of diabetes.

Methods

Normoalbuminuric type-2 diabetic patients (Group II, n=100), microalbuminuric type 2 diabetic patients (Group III, n=100) and the control group (Group I, n=100) were included in the study. The age and gender of the patient groups matched with the age and gender of the control group. HTLase, PON and ARE enzyme activities were measured by the spectrophotometric method using a g-thiobutyrinolactone, paraoxon, and phenylacetate substrates respectively. In this study, an autoanalyzer application was developed in order to measure HTLase enzyme activity for the first time.

Results

Serum HTLase, ARE and PON activities of Group III and Group II were significantly low compared to HTLase, ARE and PON results of Group I (p<0.05).

Conclusions

Based on our results, PON, ARE and HTLase enzyme activities were found to be decreased due to the increase in the degree of DN.

Vitamin E Improves Serum Paraoxonase-1 Activity and Some Metabolic Factors in Patients with Type 2 Diabetes: No Effects on Nitrite/Nitrate Levels

OBJECTIVE

It is known that markers of oxidative stress and nitrite/nitrate anion (NO_x) increase and activity of antioxidative enzyme paraoxonase-1 decline in type 2 diabetes mellitus (DM). The effects of vitamin E on paraoxonase-1 activity and NO_x in patients with type 2 diabetes are not known. The purpose of this study was to examine the hypothesis that vitamin E supplementation would affect paraoxonase-1 activity, metabolic factors, and NO_x in patients with DM.

METHODS

This double-blind, randomized, controlled clinical trial was conducted on 83 patients with DM aged 30-60 years. Forty-two of the subjects had taken 400 IU/day vitamin E and 41 were given placebo over 8 weeks. Fasting blood samples, anthropometric measurements, and dietary intake data were collected at the baseline and at the end of the trial.

RESULTS

Vitamin E significantly increased serum vitamin E level, paraoxonase-1 activity, and total antioxidant status (TAS) and decreased fasting blood sugar (FBS) compared to the control group (p < 0.05). Hemoglobin A1c, serum insulin, and insulin resistance significantly decreased in the vitamin E group compared to baseline values (p < 0.05). Alterations in serum levels of malondialdehyde and NO_x were not significant in any of groups (p > 0.05).

CONCLUSIONS

Vitamin E improved serum vitamin E level, paraoxonase-1 activity, TAS, and FBS in patients with type 2 diabetes. Longitudinal studies are warranted to assess the outcome of these results in reducing complications of diabetes in patients with type 2 diabetes.

Acute Phase Response: Implication in ST-segment Elevation Myocardial Infarction

We aimed to investigate the relation between serum inflammatory markers, 25OHvit-D3 and oxidative stress markers, namely paraoxonase1-arylesterase (PON1-ARE), total antioxidant status (TAS) and total oxidant status (TOS) in 30 male patients with ST-elevation myocardial infarction(STEMI) . There was negative correlation between tumor necrosis factor alpha and ARE; positive correlations between serum amyloid A(SAA) and oxidative stress index, SAA and TOS, 25OHvit-D3 and ARE. There was no statistically significant correlation between inflammation makers, oxidative stress markers and Gensini score. The main finding of our study was the tendency of inflammation markers, and oxidative stress markers, to change in relatively clear opposite directions in STEMI.

Decreased glutathione and elevated hair mercury levels are associated with nutritional deficiency-based autism in Oman

Genetic, nutrition, and environmental factors have each been implicated as sources of risk for autism. Oxidative stress, including low plasma levels of the antioxidant glutathione, has been reported by numerous autism studies, which can disrupt methylation-dependent epigenetic regulation of gene expression with neurodevelopmental consequences. We investigated the status of redox and methylation metabolites, as well as the level of protein homocysteinylation and hair mercury levels, in autistic and neurotypical control Omani children, who were previously shown to exhibit significant nutritional deficiencies in serum folate and vitamin B12. The serum level of glutathione in autistic subjects was significantly below control levels, while levels of homocysteine and S-adenosylhomocysteine were elevated, indicative of oxidative stress and decreased methionine synthase activity. Autistic males had lower glutathione and higher homocysteine levels than females, while homocysteinylation of serum proteins was increased in autistic males but not females. Mercury levels were markedly elevated in the hair of autistic subjects vs. control subjects, consistent with the importance of glutathione for its elimination. Thus, autism in Oman is associated with decreased antioxidant resources and decreased methylation capacity, in conjunction with elevated hair levels of mercury.

Effects of rosiglitazone on serum paraoxonase activity and metabolic parameters in patients with type 2 diabetes mellitus

Human serum paraoxonase contributes to the anti-atherogenic effect of high-density lipoprotein cholesterol (HDL-C) and has been shown to protect both low-density lipoprotein cholesterol (LDL-C) and HDL-C against lipid peroxidation. We investigated the effects of rosiglitazone on paraoxonase activity and metabolic parameters in patients with type 2 diabetes mellitus [50 patients (30 males, 20 females); mean±SD age: 58.7±9.2 years, body mass index: 28.2±4.1'kg/m²], in whom glucose control could not be achieved despite treatment with metformin, sulphonylurea, and/or insulin. The patients were given 4'mg/day rosiglitazone for 3 months in addition to their usual treatment. Serum paraoxonase activity, malondialdehyde, homocysteine, and lipid profile were measured at the time of initiation and at the end of therapy with rosiglitazone. After rosiglitazone therapy, serum levels of HDL-C, apolipoprotein A-1, and paraoxonase activity increased significantly (P<0.05) and malondialdehyde, homocysteine, lipoprotein(a), and glucose levels decreased significantly (P<0.05), but no significant changes in levels of total cholesterol and apolipoprotein B were observed. Triglyceride levels also increased significantly (P<0.05). Rosiglitazone treatment led to an improvement in glycemic control and to an increase in paraoxonase activity and HDL-C levels. Although rosiglitazone showed favorable effects on oxidant/antioxidant balance and lipid profile, further studies are needed to determine the effect of rosiglitazone on cardiovascular risk factors and cardiovascular morbidity and mortality.

CYP2E1, oxidative stress, post-translational modifications and lipid metabolism

Chronic alcohol-mediated down-regulation of hepatic ST6Gal1 gene leads to defective glycosylation of lipid-carrying apolipoproteins such as apo E and apo J, resulting in defective VLDL assembly and intracellular lipid and lipoprotein transport, which in turn is responsible for alcoholic hepatosteatosis and ALD. The mechanism of ethanol action involves thedepletion of a unique RNA binding protein that specifically interacts with its 3'-UTR region of ST6Gal1 mRNA resulting in its destabilization and consequent appearance of asialoconjugates as alcohol biomarkers. With respect to ETOH effects on Cardio-Vascular Diseases, we conclude that CYP2E1 and ETOH mediated oxidative stress significantly down regulates not only the hepatic PON1 gene expression, but also serum PON1 and HCTLase activities accompanied by depletion of hepatic GSH, the endogenous antioxidant. These results strongly implicate the susceptibility of PON1 to increased ROS production. In contrast, betaine seems to be both hepatoprotective and atheroprotective by reducing hepatosteatosis and restoring not only liver GSH that quenches free radicals, but also the antiatherogenic PON1 gene expression and activity.

Antidiabetic properties of germinated brown rice: a systematic review

Diet is an important variable in the course of type 2 diabetes, which has generated interest in dietary options like germinated brown rice (GBR) for effective management of the disease among rice-consuming populations. In vitro data and animal experiments show that GBR has potentials as a functional diet for managing this disease, and short-term clinical studies indicate encouraging results. Mechanisms for antidiabetic effects of GBR due to bioactive compounds like γ-aminobutyric acid (GABA), γ-oryzanol, dietary fibre, phenolics, vitamins, acylated steryl β-glucoside, and minerals include antihyperglycemia, low insulin index, antioxidative effect, antithrombosis, antihypertensive effect, hypocholesterolemia, and neuroprotective effects. The evidence so far suggests that there may be enormous benefits for diabetics in rice-consuming populations if white rice is replaced with GBR. However, long-term clinical studies are still needed to verify these findings on antidiabetic effects of GBR. Thus, we present a review on the antidiabetic properties of GBR from relevant preclinical and clinical studies, in order to provide detailed information on this subject for researchers to review the potential of GBR in combating this disease.

Pomegranate: a fruit that ameliorates metabolic syndrome

Pomegranate is an ancient fruit that is still part of the diet in the Mediterranean area, the Middle East, and India. Health-promoting effects have long been attributed to this fruit. Modern research corroborates the use of pomegranate as a folk remedy for diabetes and metabolic syndrome, and is responsible for a new evaluation of nutritional and pharmaceutical aspects of pomegranate in the general public. In the last decade, industry and agricultural production have been adapted to meet higher market demands for pomegranate. In vivo and in vitro studies have demonstrated that pomegranate exerts hypoglycaemic effects, including increased insulin sensitivity, inhibition of α-glucosidase, and impact on glucose transporter type 4 function, but is also responsible for a reduction of total cholesterol, and the improvement of blood lipid profiles, as well as anti-inflammatory effects through the modulation of peroxisome proliferator-activated receptor pathways. These effects may also explain how pomegranate-derived compounds function in the amelioration of adverse health effects caused by metabolic syndrome. Pomegranate contains polyphenols such as ellagitannins and anthocyanins, as well as phenolic acids, fatty acids and a variety of volatile compounds. Ellagitannins are some of the most prevalent compounds present in pomegranate, and may be responsible for certain benevolent characteristics associated with pomegranate. A brief overview of rising health problems due to obesity will be provided, followed by characterisation of the biological activity, bioavailability, and safety of pomegranate and pomegranate-derived compounds. Although the fruit is consumed in many countries, epidemiological and clinical studies are unavailable. Additional research is necessary to corroborate the promise of current in vivo and in vitro findings.

Is alcohol beneficial or harmful for cardioprotection?

While the effects of chronic ethanol consumption on liver have been well studied and documented, its effect on the cardiovascular system is bimodal. Thus, moderate drinking in many population studies is related to lower prevalence of coronary artery disease (CAD). In contrast, heavy drinking correlates with higher prevalence of CAD. In several other studies of cardiovascular mortalities, abstainers and heavy drinkers are at higher risk than light or moderate drinkers. The composite of this disparate relation in several population studies of cardiovascular mortality has been a "U-" or "J-"shaped curve. Apart from its ability to eliminate cholesterol from the intima of the arteries by reverse cholesterol transport, another major mechanism by which HDL may have this cardioprotective property is by virtue of the ability of its component enzyme paraoxonase1 (PON1) to inhibit LDL oxidation and/or inactivate OxLDL. Therefore, PON1 plays a central role in the disposal of OxLDL and thus is antiatherogenic. Furthermore, PON1 is a multifunctional antioxidant enzyme that can also detoxify the homocysteine metabolite, homocysteine thiolactone (HTL), which can pathologically cause protein damage by homocysteinylation of the lysine residues, thereby leading to atherosclerosis. We demonstrated that moderate alcohol up regulates liver PON1 gene expression and serum activity, whereas heavy alcohol consumption had the opposite effects in both animal models and in humans. The increase in PON1 activity in light drinkers was not due to preferential distribution of high PON1 genotype in this group. It is well known that wine consumption in several countries shows a remarkable inverse correlation to local rates of CAD mortality. Significantly, apart from its alcohol content, red wine also has polyphenols such as quercetin and resveratrol that are also known to have cardioprotective effects. We have shown that quercetin also up regulates PON1 gene in rats and in human liver cells. The action of quercetin seems to be mediated via the active form of the nuclear lipogenic transcription factor, sterol-regulatory element-binding protein 2 (SREBP2) that is translocated from endoplasmic reticulum to the nucleus. However, the mechanism of action of ethanol-mediated up-regulation of PON1 gene remains to be elucidated. We conclude that both moderate ethanol and quercetin, the two major components of red wine, exhibit cardioprotective properties via the up-regulation of the antiatherogenic gene PON1.

The human paraoxonase gene cluster as a target in the treatment of atherosclerosis

The paraoxonase (PON) gene cluster contains three adjacent gene members, PON1, PON2, and PON3. Originating from the same fungus lactonase precursor, all of the three PON genes share high sequence identity and a similar β propeller protein structure. PON1 and PON3 are primarily expressed in the liver and secreted into the serum upon expression, whereas PON2 is ubiquitously expressed and remains inside the cell. Each PON member has high catalytic activity toward corresponding artificial organophosphate, and all exhibit activities to lactones. Therefore, all three members of the family are regarded as lactonases. Under physiological conditions, they act to degrade metabolites of polyunsaturated fatty acids and homocysteine (Hcy) thiolactone, among other compounds. By detoxifying both oxidized low-density lipoprotein and Hcy thiolactone, PONs protect against atherosclerosis and coronary artery diseases, as has been illustrated by many types of in vitro and in vivo experimental evidence. Clinical observations focusing on gene polymorphisms also indicate that PON1, PON2, and PON3 are protective against coronary artery disease. Many other conditions, such as diabetes, metabolic syndrome, and aging, have been shown to relate to PONs. The abundance and/or activity of PONs can be regulated by lipoproteins and their metabolites, biological macromolecules, pharmacological treatments, dietary factors, and lifestyle. In conclusion, both previous results and ongoing studies provide evidence, making the PON cluster a prospective target for the treatment of atherosclerosis.

Butyrylcholinesterase genotype and gender influence Alzheimer's disease phenotype

Retrospective data are presented to support a spectrum of early Alzheimer's disease (AD) along a continuum defined by gender and genotype. The putative neurodegenerative mechanisms driving distinct phenotypes at each end of the spectrum are glial hypoactivity associated with early failure of synaptic cholinergic neurotransmission and glial overactivation associated with loss of neural network connectivity due to accelerated age-related breakdown of myelin. In early AD, male butyrylcholinesterase K-variant carriers with one or two apolipoprotein ɛ4 alleles have prominent medial temporal atrophy, synaptic failure, cognitive decline, and accumulation of aggregated beta-amyloid peptide. Increasing synaptic acetylcholine in damaged but still functional cholinergic synapses improves cognitive symptoms, whereas increasing the ability of glia to support synapses and to clear beta-amyloid peptide might be disease-modifying. Conversely, chronic glial overactivation can also drive degenerative processes and in butyrylcholinesterase K-variant negative females generalized glial overactivation may be the main driver from mild cognitive impairment to AD. Females are more likely than males to have accelerated age-related myelin breakdown, more widespread white matter loss, loss of neural network connectivity, whole brain atrophy, and functional decline. Increasing extracellular acetylcholine levels blocks glial activation, reduces myelin loss and damage to neural network connectivity, and is disease-modifying. Between extremes characterized by gender, genotype, and age, pathophysiology may be mixed and this spectrum may explain much of the heterogeneity of amnestic mild cognitive impairment. Preservation of the functional integrity of the neural network may be an important component of strengthening cognitive reserve and significantly delaying the onset and progression of dementia, particularly in females. Prospective confirmation of these hypotheses is required. Implications for future research and therapeutic opportunities are discussed.

Relationship between paraoxonase and homocysteine: crossroads of oxidative diseases

Homocysteine (Hcy) is an accepted independent risk factor for several major pathologies including cardiovascular disease, birth defects, osteoporosis, Alzheimer's disease, and renal failure. Interestingly, many of the pathologies associated with homocysteine are also linked to oxidative stress. The enzyme paraoxonase (PON1) - so named because of its ability to hydrolyse the toxic metabolite of parathion, paraoxon - was also shown early after its identification to manifest arylesterase activity. Although the preferred endogenous substrate of PON1 remains unknown, lactones comprise one possible candidate class. Homocysteine-thiolactone can be disposed of by enzymatic hydrolysis by the serum Hcy-thiolactonase/paraoxonase carried on high-density lipoprotein (HDL). In this review, Hcy and the PON1 enzyme family were scrutinized from different points of view in the literature and the recent articles on these subjects were examined to determine whether these two molecular groups are related to each other like a coin with two different sides, so close and yet so different and so opposite.

Decreased paraoxonase 1 (PON1) lactonase activity in hemodialyzed and renal transplanted patients. A novel cardiovascular biomarker in end-stage renal disease

BACKGROUND

Human paraoxonase-1 (PON1) has also been described as a lactonase. Decreased PON1 lactonase activity was found to be a predictor of cardiovascular disease. Homocysteine thiolactonase activity may prevent proteins from homocysteinylation and is thought to be a protective factor against the progression of atherosclerosis. Previous studies have demonstrated decreased PON1 paraoxonase activity in hemodialyzed (HD) and renal transplant (TRX) patients; however, lactonase activity has not been investigated. We aimed to determine the paraoxonase and lactonase activities and to clarify the relationship between lactonase activity and a set of cardiovascular risk factors, such as homocysteine, cystatin C and asymmetric dimethylarginine (ADMA) levels, in HD and TRX patients and in healthy controls.

METHODS

One hundred and eight HD and 78 TRX patients and 63 healthy controls were involved in the study. Paraoxonase and lactonase activities (paraoxon and gamma-thiobutyrolactone as substrates) were measured spectrophotometrically. ADMA level was determined with sandwich enzyme-linked immunosorbent assay.

RESULTS

Both HD and TRX patients had significantly lower lactonase activities compared to the control group (P<0.05). Significantly lower paraoxonase activities were found in HD patients compared to the TRX group (P<0.05). Significant negative correlation was found between lactonase activity and ADMA level in the whole study population (P<0.001), while paraoxonase and lactonase activities showed significant positive correlation (P<0.001). Multiple regression analysis identified paraoxonase activity and homocysteine level as independent predictors of lactonase activity.

CONCLUSION

Lactonase activity is a potential new predictor of cardiovascular risk in renal failure. Measurement of lactonase activity is recommended in future studies on HD and TRX patients.

The effect of grape seed extracts on serum paraoxonase activities in streptozotocin-induced diabetic rats

Procyanidins, a group of flavonoids, are oligomeric forms of catechins that are abundant in red wine, grapes, cocoa, and apples. Paraoxonase acts as an antioxidant enzyme and protects low-density lipoprotein-cholesterol against oxidation. In our study we aimed to evaluate the effects of grape seed extract (GSE) on paraoxonase activities in streptozotocin-induced diabetic rats. Our study included four groups of rats: Group I (n = 8), control; Group II (n = 10), GSE-supplemented; Group III (n = 6), streptozotocin-induced diabetic; and Group IV (n = 7), GSE-supplemented diabetic rats. Serum paraoxonase activities were determined with a spectrophotometric method. Paraoxonase activities in Group III were significantly lower than in the other three groups (P < .001, P < .001, and P = .005 for Groups I, II, and IV, respectively), and Group IV showed increased paraoxonase activities compared to Group III (P = .005). This is the first study to show an association between paraoxonase status and GSE supplementation and demonstrated that GSE increased paraoxonase activities. This beneficial effect of GSE was more obvious in the diabetic group, which was more prone to atherosclerotic events compared to the healthy population.

Quercetin and ethanol attenuate the progression of atherosclerotic plaques with concomitant up regulation of paraoxonase1 (PON1) gene expression and PON1 activity in LDLR-/- mice

BACKGROUND

As moderate wine drinking is atheroprotective, it is clinically relevant to elucidate its possible mechanism/s of action/s. Our objective is to demonstrate the potential benefits of the wine components, quercetin and ethanol, on the development of aortic plaques with parallel changes in antiatherogenic factors.

METHODS AND RESULTS

The effects of quercetin and ethanol on the development of aortic atherosclerotic lesions, liver PON1 gene expression, and serum PON1 activity were measured in LDLR(-/-) mice on an atherogenic diet for 4 and 8 weeks. Depending on the duration and dosage of these modulators, 12.5 to 25 mg/dl quercetin (12.5Q to 25Q) and 18 to 25% ethanol, the magnitude of decreases in aortic lesions caused by moderate ethanol and quercetin ranged from 20 to 70% (p < 0.05 to p < 0.001) based on ultrasound biomicroscopy (UBM) analyses, and from 18 to 61% (p < 0.05 to p < 0.001) based on morphometric analyses. The composite plot of all the UBM and morphometric data showed significant correlation between these 2 methods (p = 0.0001, Pearson r = 0.79 for 4-week treatment; p = 0.000004, Pearson r = 0.84 for 8-week treatment). Concomitantly, 4-week treatments with 12.5Q and 18% ethanol up regulated liver PON1 mRNA by 41% (p < 0.05) and 37% (p < 0.05), respectively, accompanied by 92% (p < 0.001) and 61% (p < 0.001) increases in serum PON1 activity, respectively. The corresponding values after 8-week treatment with 12.5Q and 18% ethanol were 23% (p < 0.05) and 40% (p < 0.02) with respect to the up regulation of liver PON1 mRNA expression, while the stimulations of serum PON1 activity were 75% (p < 0.001) and 90% (p < 0.001), respectively.

CONCLUSIONS

Based on these findings, we conclude that quercetin and moderate ethanol significantly inhibit the progression of atherosclerosis by up regulating the hepatic expression of the antiatherogenic gene, PON1, with concomitant increased serum PON1 activity.

Betaine protects chronic alcohol and omega-3 PUFA-mediated down-regulations of PON1 gene, serum PON1 and homocysteine thiolactonase activities with restoration of liver GSH

BACKGROUND

Paraoxonase (PON1) is an antioxidant enzyme that prevents LDL oxidation as well as detoxifies homocysteine thiolactone (HCTL), both of which can cause atherosclerosis. Chronic alcohol (ETOH) and high omega-3 polyunsaturated fatty acids (omega-3 PUFA) consumption may affect PON1 status presumably via reactive oxygen species by depleting liver glutathione (GSH), whereas betaine may counter their effects. Therefore, we investigated the influence of ETOH, omega-3 PUFA, and betaine on liver GSH, PON1 expression, lipid score, as well as serum PON1 and HCTLase activities.

METHODS

Experimental rats belonging to various dietary groups were pair-fed with Lieber-DeCarli low (2.8% the dietary calories as omega3-fatty acids) and high (13.8% the dietary calories as omega3-fatty acids) menhaden fish alcohol-liquid diets with and without betaine (10 g/l diet) for 8 weeks after which liver PON1 mRNA, GSH, lipid score, and serum PON1, HCTLase, and ALT activities were measured.

RESULTS

High omega-3 PUFA decreased liver PON1 mRNA expression, serum PON1, and HCTLase activity by 23% (p < 0.01), 20% (p < 0.05), and 28% (p < 0.05), respectively compared to the low omega-3 PUFA group. ETOH decreased PON1 mRNA expression by 25 and 30% (p < 0.01) with concomitant 27% (p < 0.05) and 38% (p < 0.01), decrease in liver GSH levels in low and high omega-3 PUFA groups, respectively. Correspondingly, serum PON1 activity decreased by 23% (p < 0.05) and 58% (p < 0.01) while serum HCTLase activity decreased by 25% (p < 0.05) and 59% (p < 0.01) in the low and high omega-3 PUFA ETOH groups, respectively. Betaine restored liver PON1 mRNA expressions in low and high omega-3 PUFA ETOH groups with parallel restorations of PON1 activity and liver GSH. Concomitantly, betaine reduced hepatosteatosis accompanied by alleviation of liver injury caused by chronic alcohol and high omega-3 PUFA.

CONCLUSIONS

Based on these results, we conclude that dietary betaine not only atheroprotective by restoring liver GSH that quenches free radicals, but also may alleviate liver injury by reducing hepatosteatosis.

Relations of lysophosphatidylcholine in low-density lipoprotein with serum lipoprotein-associated phospholipase A2, paraoxonase and homocysteine thiolactonase activities in patients with type 2 diabetes mellitus

AIMS

We studied the relations of lysophosphatidylcholine (lyso-PC) in LDL with serum lipoprotein-associated phospholipase A(2) (Lp-PLA(2)), paraoxonase and homocysteine thiolactonase (HTLase) activities in patients with type 2 diabetes mellitus.

METHODS

Lyso-PC was measured by electrospray ionization-liquid chromatography/mass spectrometry. Paraoxonase and HTLase activities were measured with paraoxon and gamma-thiobutyrolactone as substrates, respectively.

RESULTS

Serum HTLase and paraoxonase activities were significantly suppressed in diabetic patients (n=96) compared with control (n=25), whereas serum Lp-PLA(2) did not differ in control and diabetic patients. Lyso-PC contents in LDL correlated with serum Lp-PLA(2) activity positively and with serum HTLase activity negatively. Stepwise regression analysis revealed that serum Lp-PLA(2) and HTLase activities independently contributed to lyso-PC contents in LDL. In patients with diabetic nephropathy, lyso-PC contents in LDL were increased with reduced serum HTLase and paraoxonase activities compared with control, while serum Lp-PLA(2) activity did not differ. On the other hand, 3-month treatment with simvastatin reduced both lyso-PC contents in LDL and serum Lp-PLA(2) activity in hypercholesterolemic diabetic patients, while serum HTLase or paraoxonase activities did not change.

CONCLUSIONS

Increased lyso-PC contents in LDL were associated with the suppressed HTLase activity, and serum Lp-PLA(2) and HTLase activities may be related to lyso-PC in type 2 diabetic patients.

Pomegranate juice polyphenols increase recombinant paraoxonase-1 binding to high-density lipoprotein: studies in vitro and in diabetic patients

OBJECTIVE

The high-density lipoprotein (HDL)-associated paraoxonase-1 (PON1)/free PON1 ratio is lower in diabetic patients in comparison with healthy controls. Because diabetes is associated with increased oxidative stress, we hypothesized that a labeled recombinant PON1 (rePON1) would detect differences in HDL capacity to bind PON1 under specific experimental conditions, such as oxidation, addition of polyphenols, or in vivo dosing of diabetic patients with polyphenols.

METHODS

In the present study we determined labeled rePON1 binding to HDL under various oxidative conditions by using polyacrylamide gel electrophoresis for the separation of free labeled rePON1 from HDL-bound labeled rePON1.

RESULTS

The HDL-rePON1/free rePON1 ratio gradually decreased as the extent of HDL oxidation increased, and the antioxidants vitamin E or pomegranate juice (PJ) inhibited the redistribution of rePON1. PJ or its purified polyphenols, punicalagin, gallic acid, or ellagic acid, increased rePON1 binding also to non-oxidized HDL. Further, rePON1 associated more efficiently with HDLs isolated from diabetic patients after PJ consumption versus HDLs isolated before PJ consumption.

CONCLUSIONS

We conclude that 1) oxidative stress impairs binding of fluorescein isothiocyanate-labeled rePON1 to HDL and 2) PJ polyphenols directly increase the HDL-rePON1 association beyond their antioxidative effect.

Low human paraoxonase predicts cardiovascular events in Japanese patients with type 2 diabetes

Human serum paraoxonase (PON1) is associated with HDL and inhibits oxidative modification of LDL. PON1 enzymatic activity has been shown to decrease in diabetic patients; however, the effect of PON1 status on long-term outcome has not been reported. In this study, we examined the association between baseline PON1 status and the development of cardiovascular disease (CVD) during 10 years of follow-up in 88 type 2 diabetic patients whose enzymatic activities, concentrations, and genetic polymorphisms of PON1 had been determined. A total of 20 CVD events were recorded during the follow-up period. Using Kaplan-Meier survival curves, we found a significantly increased incidence of CVD in patients with a lower concentration or paraoxonase activity of PON1 than each median value (log-rank 7.460; P < 0.01, and log-rank 4.187; P < 0.05, respectively). By Cox regression analysis, both concentration and paraoxonase activity were significantly associated with the development of CVD, even after correction for gender, age, and preexisting CVD (P < 0.05). Low concentration and enzymatic activity of PON1 may be an independent predictor of cardiovascular events in diabetic patients.

Loss of total and visceral adipose tissue mass predicts decreases in oxidative stress after weight-loss surgery

It is not known whether there are mechanisms linking adipose tissue mass and increased oxidative stress in obesity. This study investigated associations between decreasing general and abdominal fat depots and oxidative stress during weight loss. Subjects were severely obese women who were measured serially at baseline and at 1, 6 (n = 30), and 24 months (n = 18) after bariatric surgery. Total fat mass (FAT) and volumes of visceral (VAT) and subcutaneous abdominal adipose tissue (SAT) were related to plasma concentrations of derivatives of reactive oxidative metabolites (dROMS), a measure of lipid peroxides and oxidative stress. After intervention, BMI significantly decreased, from 47.7 +/- 0.8 kg/m(2) to 43.3 +/- 0.8 kg/m(2) (1 month), 35.2 +/- 0.8 kg/m(2) (6 months), and 30.2 +/- 1.2 kg/m(2) (24 months). Plasma dROMS also significantly deceased over time. At baseline, VAT (r = 0.46), FAT (r = 0.42), and BMI (r = 0.37) correlated with 6-month decreases in dROMS. Similarly, at 1 month, VAT (r = 0.43) and FAT (r = 0.41) correlated with 6-month decreases in dROMS. Multiple regression analysis showed that relationships between VAT and dROMS were significant after adjusting for FAT mass. Increased plasma dROMS at baseline were correlated with decreased concentrations of high-density lipoprotein (HDL) at 1 and 6 months after surgery (r = -0.38 and -0.42). This study found longitudinal associations between general, and more specifically intra-abdominal adiposity, and systemic lipid peroxides, suggesting that adipose tissue mass contributes to oxidative stress.

Quercetin up-regulates paraoxonase 1 gene expression with concomitant protection against LDL oxidation

Paraoxonase 1 (PON1) protects the oxidative modification of low-density lipoprotein (LDL) and is a major anti-atherosclerotic protein component of high-density lipoprotein (HDL). Quercetin, a ubiquitous plant flavonoid, has been shown to have a number of bioactivities and may offer a variety of potential therapeutic uses. We explored the roles of quercetin in the regulation of PON1 expression, serum and liver activity and protective capacity of HDL against LDL oxidation in rats. Compared to the pair-fed control group, feeding quercetin (10 mg/L) in the liquid diet for 4 weeks increased (a) hepatic expression of PON1 by 35% (p<0.01), (b) serum and liver PON1 activities by 29% (p<0.05) and 57% (p<0.01), respectively, and (c) serum homocysteine thiolactonase (HCTL) activity by 23% (p<0.05). Correspondingly, the lag time of low-density lipoprotein (LDL) oxidation was increased by >3-fold (p<0.001) with plasma HDL from quercetin-fed group compared to the HDL from control group. Our data suggest that quercetin has antiatherogenic effect by up regulating PON1 gene expression and its protective capacity against LDL oxidation.

Oxidative inactivation of lactonase activity of purified human paraoxonase 1 (PON1)

Paraoxonase1 (PON1), one of HDL-associated antioxidant proteins, is known to lose its activity in vivo systems under oxidative stress. Here, we examined the effect of various oxidants on lactonase activity of PON1, and tried to protect the lactonase activity from oxidative inactivation. Among the oxidative systems tested, the ascorbate/Cu(2+) system was the most potent in inactivating the lactonase activity of purified PON1; in contrast to a limited role of Fe(2+), Cu(2+) (0.05-1.0 microM) remarkably enhanced the inactivation of PON1 in the presence of ascorbate (0.02-0.1 mM). Moreover, Cu(2+) alone inhibited the lactonase activity at concentrations as low as 1 microM. The ascorbate/Cu(2+)-mediated inactivation of PON1 lactonase activity was prevented by catalase, but not general hydroxyl radical scavengers, suggesting the implication of Cu(2+)-bound hydroxyl radicals in the oxidative inactivation. Compared to arylesterase activity, lactonase activity appears to be more sensitive to Cu(2+)-catalyzed oxidation. Separately, ascorbate/Cu(2+)-mediated inactivation of lactonase activity was prevented by oleic acid as well as phoshatidylcholine. Taken together, our data demonstrate that Cu(2+)-catalyzed oxidation may be a primary factor to cause the decrease of PON1 lactonase activity under oxidative stress and that lactonase activity of PON1 is most susceptible to ascorbate/Cu(2+) among PON1 activities. In addition, we have showed that radical-induced inactivation of lactonase activity is prevented by some lipids.

The antiatherogenic function of HDL is impaired in hyperhomocysteinemic subjects

High plasma homocysteine concentrations have been associated with increased risk of cardiovascular disease, whereas plasma HDL concentration is inversely correlated to such disorders. We hypothesized that hyperhomocysteinemic subjects may have dysfunctional HDL. We therefore investigated the ability of serum from hyperhomocysteinemic male and female subjects (n = 10) and control subjects (n = 10) to induce cholesterol efflux and to inhibit release of inflammatory mediators from human umbilical vein endothelial cell. We found that serum from hyperhomocysteinemic subjects had impaired ability to induce cholesterol efflux from lipid-loaded macrophages compared with healthy controls. HDL from those with markedly raised homocysteine concentrations had a reduced antiinflammatory effect in tumor necrosis factor-alpha-activated endothelial cells with an attenuated suppressive effect on interleukin-6 growth-related oncogene-alpha release. Also, the activity of paraoxonase in serum, a multifunctional enzyme with antioxidative effects in relation to the function of HDL, was significantly reduced in hyperhomocysteinemic subjects, in particular those with markedly raised homocysteine concentration. Our findings suggest that hyperhomocysteinemic individuals have dysfunctional HDL particles with attenuated antiatherogenic activity and may represent a novel explanation for the increased risk of cardiovascular events in these individuals.

Consumption of wonderful variety pomegranate juice and extract by diabetic patients increases paraoxonase 1 association with high-density lipoprotein and stimulates its catalytic activities

Association of paraoxonase 1 (PON1) with high-density lipoprotein (HDL) stabilizes the enzyme. In diabetic patients, PON1 dissociates from HDL and, as a consequence, is less biologically active. Our aim was to investigate the effects of Wonderful variety pomegranate juice (WPJ) and pomegranate polyphenol extract (WPOMxl) consumption on PON1 association with HDL in diabetic patients. Thirty patients with type 2 diabetes mellitus participated in the study. Ten male patients and 10 female patients received concentrated WPJ (50 mL/day for 4 weeks), while another group of 10 male patients received WPOMxl (5 mL/day for 6 weeks). There were no significant effects of WPJ or WPOMxl consumption on fasting blood glucose or hemoglobin A1c levels. After 4 weeks of WPJ consumption by male patients, basal serum oxidative stress was significantly decreased by 35%, whereas serum concentrations of thiol groups significantly increased by 25%. Moreover, HDL-associated PON1 arylesterase, paraoxonase, and lactonase activities increased significantly after WPJ consumption by 34-45%, as compared to the baseline levels. PON1 protein binding to HDL was significantly increased by 30% following WPJ consumption, and the enzyme became more stable. In male patients that consumed WPOMxl and in female patients that consumed PJ, a similar pattern was observed, although to a lesser extent. We conclude that WPJ as well as WPOMxl consumption by diabetic patients does not worsen their diabetic parameters. Furthermore, WPJ as well as WPOMxl consumption contribute to PON1 stabilization, increased association with HDL, and enhanced catalytic activities. These beneficial effects of pomegranate consumption on serum PON1 stability and activity could lead to retardation of atherosclerosis development in diabetic patients.

Paraoxonase 1 (PON1) attenuates diabetes development in mice through its antioxidative properties

Paraoxonase 1 (PON1) is a lipo-lactonase which is associated with HDL and possesses antioxidative properties. Diabetes is characterized by increased oxidative stress and by decreased PON1 activity. We aimed to analyze whether oxidative status and PON1 levels in mouse sera and macrophages could affect streptozotocin (STZ)-induced diabetes development. We have used two models of mice under low oxidative stress: STZ-injected apolipoprotein E-deficient mice supplemented with the antioxidant vitamin E, and P47(phox) knockout mice. In both mice models the decreased serum basal oxidative stress, was associated with a decreased rate of diabetes development, compared with control STZ-injected apolipoprotein E-deficient mice or with C57BL mice respectively. These data suggest that oxidative stress accelerates diabetes development. Next, we analyzed the effect of PON1 on macrophage oxidative stress and on diabetes development in STZ-injected C57BL mice, PON1 knockout mice, and PON1 transgenic mice. PON1 overexpression was associated with decreased diabetes-induced macrophage oxidative stress, decreased diabetes development, and decreased mortality, in comparison to C57BL mice, and even more so when compared to PON1KO mice. We thus concluded that on increasing PON1 expression in mice, diabetes development is attenuated, a phenomenon which could be attributed to the antioxidative properties of PON1, as decrement of oxidative stress significantly attenuated STZ-induced diabetes development.

Redox regulation in the extracellular environment

The oxidizing nature of the extracellular environment is vastly different from the highly reducing nature of the intracellular compartment. The redox potential of the cytosolic compartment of the intracellular environment limits disulfide bond formation, whereas the oxidizing extracellular environment contains proteins rich in disulfide bonds. If not for an extracellular antioxidant system to eliminate reactive oxygen and nitrogen species, lipid peroxidation and protein oxidation would become excessive, resulting in cellular damage. Many reviews have focused on the role of intracellular antioxidants in the elimination of oxidative stress, but this one will focus on the coordinated action of both intracellular and extracellular antioxidants in limiting cellular oxidant stress.

Why is HDL functionally deficient in type 2 diabetes?

High-density lipoprotein (HDL) particles exert a spectrum of atheroprotective activities that can be deficient in type 2 diabetes. Key mechanisms leading to the formation of functionally deficient HDL involve 1) HDL enrichment in triglycerides and depletion in cholesteryl esters with conformational alterations of apolipoprotein A-I; 2) glycation of apolipoproteins and/or HDL-associated enzymes; and 3) oxidative modification of HDL lipids, apolipoproteins, and/or enzymes. Available data identify hypertriglyceridemia, with concomitant compositional modification of the HDL lipid core and conformational change of apolipoprotein A-I, as a driving force in functional alteration of HDL particles in type 2 diabetes. Therapeutic options for correcting HDL functional deficiency should target hypertriglyceridemia by normalizing circulating levels of triglyceride-rich lipoproteins.

Effect of pre-germinated brown rice intake on diabetic neuropathy in streptozotocin-induced diabetic rats

BACKGROUND

To study the effects of a pre-germinated brown rice diet (PR) on diabetic neuropathy in streptozotocin (STZ)-induced diabetic rats.

METHODS

The effects of a PR diet on diabetic neuropathy in STZ-induced diabetic rats were evaluated and compared with those fed brown rice (BR) or white rice (WR) diets with respect to the following parameters: blood-glucose level, motor-nerve conduction velocity (NCV), sciatic-nerve Na+/K+-ATPase activity, and serum homocysteine-thiolactonase (HTase) activity.

RESULTS

Compared with diabetic rats fed BR or WR diets, those fed a PR diet demonstrated significantly lower blood-glucose levels (p < 0.001), improved NCV (1.2- and 1.3-fold higher, respectively), and increased Na+/K+-ATPase activity (1.6- and 1.7-fold higher, respectively). The PR diet was also able to normalize decreased serum homocysteine levels normally seen in diabetic rats. The increased Na+/K+-ATPase activity observed in rats fed PR diets was associated with elevations in HTase activity (r = 0.913, p < 0.001). The in vitro effect of the total lipid extract from PR bran (TLp) on the Na+/K+-ATPase and HTase activity was also examined. Incubation of homocysteine thiolactone (HT) with low-density lipoprotein (LDL) in vitro resulted in generation of HT-modified LDL, which possessed high potency to inhibit Na+/K+-ATPase activity in the sciatic nerve membrane. The inhibitory effect of HT-modified LDL on Na+/K+-ATPase activity disappeared when TLp was added to the incubation mixture. Furthermore, TLp directly activated the HTase associated with high-density lipoprotein (HDL).

CONCLUSION

PR treatment shows efficacy for protecting diabetic deterioration and for improving physiological parameters of diabetic neuropathy in rats, as compared with a BR or WR diet. This effect may be induced by a mechanism whereby PR intake mitigates diabetic neuropathy by one or more factors in the total lipid fraction. The active lipid fraction is able to protect the Na+/K+-ATPase of the sciatic-nerve membrane from the toxicity of HT-modified LDL and to directly activate the HTase of HDL.