Paraoxonase 1 R/Q alleles are associated with differential accumulation of saturated versus 20:5n3 fatty acid in human adipose tissue

Associação do Genótipo e Fenótipo da Paraoxonase-1 com Angiografia Positiva para Doença Arterial Coronariana

Fundamento

Tem sido demonstrado que um aumento dos níveis séricos de PON1 é protetor contra vários distúrbios. Foi relatado que vários polimorfismos de nucleotídeo único (SNPs, single nucleotide polymorphisms ) do gene PON1 estão associados a níveis e atividade de proteínas enzimáticas séricas.

Objetivos

Investigar a associação de SNPs do PON1 e atividade da paraoxonase sérica com a doença arterial coronariana (DAC).

Métodos

Foram estudados 601 pacientes não relacionados submetidos à angiografia coronária, incluindo aqueles com estenose >50% (N=266) e aqueles com estenose <30% (N=335). Os SNPs rs662 e rs840560 do gene da paraoxonase foram determinados utilizando o método ARMS-PCR e o SNP rs705379 foi genotipado utilizando análise de PCR-RFLP. A atividade da paraoxonase sérica foi medida utilizando paraoxon como substrato. O valor de p<0,05 foi considerado significante.

Resultados

A atividade da paraoxonase sérica não foi significativamente diferente entre os grupos de estudo. Após ajuste para idade, sexo, hipertensão, diabetes mellitus e dislipidemia, o genótipo GG e o modelo codominante de rs662 foram positivamente associados a uma angiografia positiva (respectivamente, OR = 2,424, IC 95% [1,123-5,233], p <0,05, OR = 1,663, IC 95% [1,086-2,547]). A atividade da paraoxonase sérica foi significativamente maior no alelo G e variante GG do polimorfismo rs662, alelo A e variante AA de rs854560 e alelo C e variante CC de rs705379. A análise de haplótipos mostrou que o haplótipo ATC foi significativamente mais prevalente no grupo com angiografia negativa. A análise entre os grupos indicou que o alelo A de rs662 foi significativamente associado à menor atividade da paraoxonase no grupo com angiografia positiva (p=0,019).

Conclusões

A presença do alelo G do polimorfismo de nucleotídeo único rs662 está independentemente associada ao aumento do risco de DAC.

Application of metabolomics part II: Focus on fatty acids and their metabolites in healthy adults

Fatty acids (FAs) play critical roles in health and disease. The detection of FA imbalances through metabolomics can provide an overview of an individual’s health status, particularly as regards chronic inflammatory disorders. In this study, we aimed to establish sensitive reference value ranges for targeted plasma FAs in a well-defined population of healthy adults. Plasma samples were collected from 159 participants admitted as outpatients. A total of 24 FAs were analyzed using gas chromatography-mass spectrometry, and physiological values and 95% reference intervals were calculated using an approximate method of analysis. The differences among the age groups for the relative levels of stearic acid (P=0.005), the omega-6/omega-3 ratio (P=0.027), the arachidonic acid/eicosapentaenoic acid ratio (P<0.001) and the linoleic acid-produced dihomo-gamma-linolenic acid (P=0.046) were statistically significant. The majority of relative FA levels were higher in males than in females. The levels of myristic acid (P=0.0170) and docosahexaenoic acid (P=0.033) were signifi-cantly different between the sexes. The reference values for the FAs examined in this study represent a baseline for further studies examining the reproducibility of this methodology and sensitivities for nutrient deficiency detection and investigating the biochemical background of pathological conditions. The application of these values to clinical practice will allow for the discrimination between health and disease and contribute to early prevention and treatment.

Paraoxonase-1 genetic polymorphisms in organophosphate metabolism

Organophosphates (OPs) are a class of chemicals commonly used in agriculture as pesticides, that can often lead to severe toxicity in humans. Paraoxonase-1 (PON1) belongs to a family of A-esterases and hydrolyses several OPs while also serving other biological roles. Two main genetic polymorphisms have been shown to affect enzymatic ability; an A > G transition in the 192nd position (192 Q/R, rs662), and an A > T at codon 55 (55 M/L, rs854560). In this review, we searched PubMed for relevant articles published from its inception till June 2018 and included publications from 1996 to 2018. We aimed to address the distribution of the polymorphisms in various populations, the way they affect enzymatic activity and the possible use of PON1 as a biomarker. The polymorphisms present great heterogeneity between populations, with the data being clearer over 192 Q/R, and this heterogeneity is related to the phylogenetic origins of each population. Concerning enzymatic activity, the different genotypes react better or worse to different OP substrates, with studies presenting a variety of findings. Detecting the "paraoxonase status" of an individual -referring to PON1 function- seems to be important in predicting OP toxicity, as studies have shown that some specific-genotype individuals present symptoms of toxicity in higher rates than others. We are strongly convinced that in order for the scientific community to reach a consensus over which polymorphisms confer susceptibility to toxicity and whether PON1 can eventually be used as a biomarker, more studies need to be carried out, since the data thus far does not seem to reach a universal conclusion.

Gender-dependent difference in serum paraoxonase 1 levels of Hanwoo, Korean native cattle, and a positive association with meat quality

OBJECTIVE

Paraoxonase 1 (PON1), a calcium-dependent serum enzyme, has been shown to be involved in lipid metabolism. In this study, we examined the putative correlation of the serum PON1 level of Hanwoo, Korean native cattle, with gender and meat quality grade.

METHODS

PON1 levels were estimated by determining the arylesterase and paraoxonase activities (AE and PO, respectively) in serum samples from Hanwoo individuals (n = 56). Serum PON1 levels were analyzed in different gender groups (female [n = 21], castrated male [n = 17], and male [n = 18]), and meat quality grades (≥1 [n = 23], 2 [n = 21], and 3 [n = 12]).

RESULTS

Serum PON1 levels were similar in female (AE = 120±55 U/mL, PO = 84±43 mU/mL) and castrated male (123±44 U/mL, PO = 89±30 mU/mL), while male showed a significantly lower level (AE = 65±43 U/mL, PO = 44±34 mU/mL). Furthermore, analysis of serum PON1 levels in three different grades of meat quality showed similar levels in the grades ≥1 (AE = 118±49 U/mL, PO = 84±37 mU/mL) and 2 (AE = 116±54 U/mL, PO = 82±43 mU/mL), while the level was significantly lower in the grade 3 (AE = 58±35 U/mL, PO = 39±27 mU/mL) of lower meat quality.

CONCLUSION

We discovered the gender-dependent differences in serum PON1 levels of Hanwoo and a positive association of the serum PON1 level with meat quality. Results in this study suggest that PON1 would be a useful serum marker for preliminary screening of Hanwoo individuals with high-quality meat and applicable for genetic improvement.

Evaluation of Association Between Q192R and L55M Genetic Polymorphisms of PON1 and Serum Paraoxonase-1 Activity in Healthy Individuals, a Meta-Analysis

Background and Aims: Several studies have reported the alteration of the paraoxonase 1 (PON1) enzyme activity in various diseases, including diabetes mellitus. The Q192R and L55M are two genetic variations in the coding region of PON1. To evaluate the relationship between these polymorphisms and the alteration in serum paraoxonase activity, the present meta-analysis was carried out. Material and Methods: Eligible studies published before October 2017 was identified in several databases. The paraoxonase activity in subjects with variant alleles of the study polymorphisms were normalized using the activity of the QQ or LL genotypes. The pooled mean effect of alterations in activity level and its 95% confidence intervals (95% CI) was calculated. Results: Thirty-two studies including 11532 healthy participants were used for the present meta-analysis. The paraoxonase activity was increased in the QR and RR genotypes. This elevation was greater among Caucasians than those among Asians and Africans. The activity in the LM and MM genotypes compared with the LL genotype were decreased, this reduction in Caucasians was greater than Africans. Conclusions: At least in part other PON1 polymorphisms and environmental factors may accounts for heterogeneity between studies.

Lipoprotein redox status evaluation as a marker of cardiovascular disease risk in patients with inflammatory disease

Patients with chronic inflammatory disorders (ID) have an increased risk of developing cardiovascular disease, and routinely determined parameters do not reveal the real metabolic status of specific subgroups, such as patients with rheumatoid arthritis (RA). In this study, in order to evaluate state of the art markers for the assessment of cardiometabolic risk, abnormalities in lipoprotein levels in patients with a low-grade inflammatory status [diabetes mellitus (DM) subgroup] and in patients with a high systemic inflammatory burden (RA subgroup) was determined. The study group comprised patients with ID [DM (n=20) and RA (n=20)], with an aged-matched control group (n=17). Patient serum was used to determine routine biochemical parameters and to isolate low-density lipoprotein (LDL) and high-density lipoprotein (HDL). The heparin-citrate method was used for LDL precipitation and the phosphotungstic acid-MgCl₂ technique for the isolation of HDL. Further, Amplex Red and advanced oxidation protein product (AOPP) assays were applied to determine lipid peroxides and protein oxidation, respectively, while the levels of serum advanced glycation end products (AGEs) were also determined. Although the differences in the routinely determined lipidemic profile were notable between the DM and RA subgroups, markers of lipid peroxidation and of advanced protein oxidation/glycation did not differ significantly, indicating possible similar oxidative damage of serum lipoproteins. On the whole, as alterations in lipoprotein functionality can occur long before any changes in routinely measured biochemical parameters are observed, more sensitive markers for the assessment of cardiovascular risk are required. As AOPPs, AGEs, oxidized LDL (oxLDL) and especially oxidized HDL (oxHDL) are affected during the early stages of inflammatory disease, and due to their known link to coronary artery disease, it would be wise to include these markers in the routine cardiovascular evaluation of patients with chronic inflammatory disease, such as those with RA.

Serum Paraoxonase activity in relation to lipid profile in Age-related Macular Degeneration patients

Age-related Macular Degeneration (AMD) is a multifactorial disease causing visual impairment in old age. Oxidative stress is one of the main contributors for the disease progression. Paraoxonase (PON), a HDL-resident antioxidant enzyme which removes oxidized low density lipoprotein (oxLDL), which is not studied much in AMD. This study assesses the PON activities in relation to the lipid status and genetic variants in AMD patients. In this prospective case-control study, a total of 48 AMD patients and 30 unrelated healthy controls were recruited. The serum oxLDL and Plasma Homocysteine (Hcy) levels were estimated by ELISA. Plasma Homocysteine thiolactone (HCTL) was estimated by HPLC. Serum PON activities were estimated by spectrophotometry. PON gene expression was assessed by qPCR and protein expression by western blot, immunofluorescence and FACS analysis. Two known single nucleotide polymorphisms (SNPs) in the coding region of PON1, Q192R and L55M variants were checked in the AMD patients and controls and their association with PON activity and lipid levels were determined. Serum paraoxonase (PONase) and thiolactonase (PON-HCTLase) activities were significantly elevated in AMD patients than in controls apart from elevated serum levels of total cholesterol (TC), triglycerides (TG), oxLDL. While serum LDL levels in AMD patients correlate positively with PON HCTLase activity, the serum high density lipoprotein (HDL) correlates with both PONase and PON-HCTLase activities. However, multiple regression analysis showed that, amongst the parameters, only serum TG was a significant risk factor for AMD, after adjusting for demographic parameters as well as cataract. PON2 was significantly increased at the level of gene expression (p = 0.03) as seen in circulating peripheral blood mononuclear cells (PBMC) of AMD patients possibly mediated by the transcription factor SP1, that showed 2-fold increase. PON1 and 2 protein expressions also showed significant increase in the PBMC of AMD patients. At serum level, PON1 protein was significantly increased in AMD patients. Cholesterol transporters such as CD36, SR-B1 and ABCA1 gene expressions were also found to be higher (1.5, 1.9 and 2.4-fold respectively) in AMD, though not statistically significant. While the wet AMD (CNV) was found to be associated with increase in oxLDL and serum PONase activity, the dry AMD was associated with increased HDL and serum PON-HCTLase activity. The genotype and allele frequencies of Q192R & L55M were not significantly different between AMD patients and controls. However, altered lipid status and PON activities were associated with the genotype in AMD patients. A higher enzyme activity was observed for the RR genotype of Q192R in the cohort, irrespective of case and control. Thus the PON genotype and phenotype seem to play a role in the pathogenesis of AMD.

Oxidative stress biomarkers and paraoxonase 1 polymorphism frequency in farmers occupationally exposed to pesticides

Previous evidence has demonstrated that chemical classes of pesticides, including organophosphates (OP), can induce oxidative stress in exposed workers. The resulting increase in free radicals causes damage to biological macromolecules, and promotes the formation of novel compounds, including advanced glycation end products (AGE) and advanced oxidation protein products (AOPP). The present study aimed to evaluate the common genetic polymorphisms of the paraoxonase 1 (PON1) gene in a group of 55 farmers exposed to pesticides, as well as the association between these polymorphisms and serum levels of AGE and AOPP. The 192Q wild‑type (WT) allele was present at a significantly higher frequency, compared with the 192R mutated allele (0.74 and 0.26, respectively). The WT allele was predominantly represented by the homozygote 192QQ genotype (51%). The mutated 192QR heterozygotic allele was prevalent, at a frequency of 45.4%, whereas the mutated homozygotes were present at a frequency of 3.6%. A significant decrease in the levels of AGE and AOPP was observed in farmers exhibiting the homozygotic 192RR mutated genotype (14,7221 AU/ml and 0.64 nmol/ml, respectively), compared with the WT genotype (16,1400 AU/ml and 1.76 nmol/ml, respectively), and 192QR genotype (15,2312 AU/ml and 1.60 nmol/ml, respectively). Therefore, due to the high catalytic activity of PON1, the 192RR genotype provides an important genetic predictor of the toxic effects associated with OP pesticide exposure. It determines a minor risk of developing oxidative damage following pesticide exposure, and measuring the levels of AOPP may provide a novel biomarker for oxidative damage in subjects exposed to OP.

γ-Glutamyl carboxylase in osteoblasts regulates glucose metabolism in mice

Vitamin K-dependent γ-glutamyl carboxylase (GGCX) is an enzyme that catalyzes the conversion of glutamic acid to gamma-carboxyglutamic acid in substrate proteins. Among GGCX target proteins, recent evidence indicates that osteocalcin regulates insulin sensitivity and secretion. However, the precise contribution of GGCX to glucose metabolism remains to be clarified. To address this question, we generated osteoblast-specific Ggcx-deficient (i.e., conditional knockout [cKO]) mice using collagen type 1 α1 (Col1)-Cre mice. Ggcx cKO mice exhibited altered metabolism compared with their controls; serum glucose levels could be maintained with low amounts of insulin, and the weight of white adipose tissue (WAT) significantly decreased in Ggcx cKO mice. Our findings suggest that GGCX expressed in osteoblasts is critical for the maintenance of blood glucose and WAT.

Paraoxonase 1 and homocysteine metabolism

Paraoxonase 1 (PON1), a component of high-density lipoprotein (HDL), is a calcium-dependent multifunctional enzyme that connects metabolisms of lipoproteins and homocysteine (Hcy). Both PON1 and Hcy have been implicated in human diseases, including atherosclerosis and neurodegeneration. The involvement of Hcy in disease could be mediated through its interactions with PON1. Due to its ability to reduce oxidative stress, PON1 contributes to atheroprotective functions of HDL in mice and humans. Although PON1 has the ability to hydrolyze a variety of substrates, only one of them-Hcy-thiolactone-is known to occur naturally. In humans and mice, Hcy-thiolactonase activity of PON1 protects against N-homocysteinylation, which is detrimental to protein structure and function. PON1 also protects against neurotoxicity associated with hyperhomocysteinemia in mouse models. The links between PON1 and Hcy in relation to pathological states such as coronary artery disease, stroke, diabetic mellitus, kidney failure and Alzheimer's disease that emerge from recent studies are the topics of this review.

Long term stability of paraoxonase-1 and high-density lipoprotein in human serum

BACKGROUND

Paraoxonase-1 (PON1) is an enzyme with numerous functions and receives an increasing interest in clinical and epidemiological studies. Sometimes samples are stored for longer periods at a certain temperature. Therefore the stability of PON1 activity must be checked and retained upon storage for longer periods.

RESULTS

In this study the stability of PON1 activity has been tested in human serum samples during storage up to 12 months at 3 commonly used temperatures, -20°C, -70°C and -196°C. It was found that the stability of the PON1 activity is constant during 12 months of storage at -70°C and -196°C. Storage at -20°C resulted in a small but statistically significant decrease after 6 months to about 94% of its original value. Nonetheless, the rank order between the samples at T = 0 and 12 months remained the same. The same temperature dependence was found for the associated high-density lipoprotein.

CONCLUSIONS

It can be concluded that -70°C is the right temperature for storage to maintain the PON1 activity for at least one year. Storage at a lower temperature in liquid nitrogen (-196°C) is not necessary.

Effect of dietary lipids on paraoxonase-1 activity and gene expression

AIMS

Aim of the paper was to summarize the literature about the effect of dietary lipids on activity of paraoxonase-1 (PON1), a multifunctional enzyme associated with high density lipoprotein (HDL). PON1 exerts a protective effect against oxidative damage of cells and lipoproteins and modulates the susceptibility of HDL and LDL to atherogenic modifications such as homocysteinylation.

DATA SYNTHESIS

The present review shows evidence that the amount and the composition of dietary lipids are key factors in the modulation of PON1. The effect of dietary lipids is also modulated by PON1 polymorphisms. The molecular mechanisms involved include an effect on PON1 hepatic synthesis or secretion and/or modification of PON1 interactions with HDL. Changes of PON1 activity could also be related to dietary intake of oxidized lipids that behave as PON1 inhibitors.

CONCLUSION

Dietary fatty acids by the modulation of PON1 gene expression and activity could constitute an useful approach for the prevention of human diseases associated with oxidative damage.

Histological and transcriptome-wide level characteristics of fetal myofiber hyperplasia during the second half of gestation in Texel and Ujumqin sheep

BACKGROUND

Whether myofibers increase with a pulsed-wave mode at particular developmental stages or whether they augment evenly across developmental stages in large mammals is unclear. Additionally, the molecular mechanisms of myostatin in myofiber hyperplasia at the fetal stage in sheep remain unknown. Using the first specialized transcriptome-wide sheep oligo DNA microarray and histological methods, we investigated the gene expression profile and histological characteristics of developing fetal ovine longissimus muscle in Texel sheep (high muscle and low fat), as a myostatin model of natural mutation, and Ujumqin sheep (low muscle and high fat). Fetal skeletal muscles were sampled at 70, 85, 100, 120, and 135 d of gestation.

RESULTS

Myofiber number increased sharply with a pulsed-wave mode at certain developmental stages but was not augmented evenly across developmental stages in fetal sheep. The surges in myofiber hyperplasia occurred at 85 and 120 d in Texel sheep, whereas a unique proliferative surge appeared at 100 d in Ujumqin sheep. Analysis of the microarray demonstrated that immune and hematological systems' development and function, lipid metabolism, and cell communication were the biological functions that were most differentially expressed between Texel and Ujumqin sheep during muscle development. Pathways associated with myogenesis and the proliferation of myoblasts, such as calcium signaling, chemokine (C-X-C motif) receptor 4 signaling, and vascular endothelial growth factor signaling, were affected significantly at specific fetal stages, which underpinned fetal myofiber hyperplasia and postnatal muscle hypertrophy. Moreover, we identified some differentially expressed genes between the two breeds that could be potential myostatin targets for further investigation.

CONCLUSIONS

Proliferation of myofibers proceeded in a pulsed-wave mode at particular fetal stages in the sheep. The myostatin mutation changed the gene expression pattern in skeletal muscle at a transcriptome-wide level, resulting in variation in myofiber phenotype between Texel and Ujumqin sheep during the second half of gestation. Our findings provide a novel and dynamic description of the effect of myostatin on skeletal muscle development, which contributes to understanding the biology of muscle development in large mammals.

Role of paraoxonase 1 (PON1) in organophosphate metabolism: implications in neurodegenerative diseases

Organophosphate pesticides are a class of compounds that are widely used in agricultural and rural areas. Paraoxonase 1 (PON1) is a phase-I enzyme that is involved in the hydrolysis of organophosphate esters. Environmental poisoning by organophosphate compounds has been the main driving force of previous research on PON1 enzymes. Recent discoveries in animal models have revealed the important role of the enzyme in lipid metabolism. However although PON1 function is well established in experimental models, the contribution of PON1 in neurodegenerative diseases remains unclear. In this minireview we summarize the involvement of PON1 genotypes in the occurrence of Parkinson's disease, Alzheimer's disease and amyotrophic lateral sclerosis. A brief overview of latest epidemiological studies, regarding the two most important PON1 coding region polymorphisms PON1-L55M and PON1-Q192R is presented. Positive and negative associations of PON1 with disease occurrence are reported. Notably the MM and RR alleles contribute a risk enhancing effect for the development of some neurodegenerative diseases, which may be explained by the reduced lipoprotein free radical scavenging activity that may give rise to neuronal damage, through distinct mechanism. Conflicting findings that fail to support this postulate may represent the human population ethnic heterogeneity, different sample size and environmental parameters affecting PON1 status. We conclude that further epidemiological studies are required in order to address the exact contribution of PON1 genome in combination with organophosphate exposure in populations with neurodegenerative diseases.