Can HDL cholesterol be replaced by paraoxonase 1 activity in the prediction of severe coronary artery disease in patients with type 2 diabetes?

BACKGROUND AND AIMS: Novel biomarkers are required to improve cardiovascular disease prediction in patients with type 2 diabetes (T2D) as a high-risk population. This study was conducted to examine whether coronary artery disease (CAD) risk assessment can be improved by substituting high-density lipoprotein (HDL)-bound paraoxonase 1 (PON1) activity for HDL cholesterol (HDL-C) concentration in patients with T2D. METHODS AND RESULTS: In this study, we studied 139 patients with T2D (mean age 64.12 ± 8.17 years) who underwent coronary angiographic examination. The initial rate of substrate hydrolysis was spectrophotometrically assayed in kinetic mode for measuring PON1 activity. Receiver operating characteristic (ROC) graphs are created by plotting true positivity versus false positivity. In patients with HbA1c ≥ 7%, PON1 (AUC = 0.7, p = 0.029) and nonHDL-C/PON1 (AUC = 0.75, p = 0.013) were significantly more capable of differentiating patients with CAD from those without CAD compared to HDL-C and nonHDL-C/HDL-C. Also, the predictive power of PON1 (AUC = 0.64, p = 0.029) and nonHDL-C/PON1 (AUC = 0.71, p = 0.004) were significantly higher in comparison with HDL-C and nonHDL-C/HDL-C for CAD characterization in patients aged ≥50 years. Moreover, PON1 and nonHDL-C/PON1 are associated with the incidence of CAD with an AUC of 0.7 (p = 0.026) and AUC of 0.64 (p = 0.087), respectively, among subjects with low HDL-C. CONCLUSION: PON1 and the ratio of nonHDL-C/PON1 significantly improve the prediction of severe CAD in T2D patients and in patients with HbA1c ≥ 7%, age ≥50 years, or low HDL-C. PON1 activity and lipid ratios using this enzyme may be valuable as substitutes of HDL-C for increasing clinical efficacies in cardiovascular risk assessment.

Epigenetics of paraoxonases.

PURPOSE OF REVIEW: Studies have shown the three-member paraoxonase (PON) multigene family to be involved in the development of a large variety of diseases with an inflammatory component. Environmental factors such as lifestyle-related factors differ widely between populations and it is important to consider that their impacts may be exerted through the epigenetic mechanisms, which connect genes, the environment and disease development and are a potential therapeutic avenue. RECENT FINDINGS: In the review period, very little was published on epigenetics of PON2 or PON3, mostly on their diagnostic value in cancer by measuring methylation levels of these genes. However, the picture is more promising with PON1. Here, several studies have linked the epigenetic regulation of PON1 to various metabolic processes and particularly to the development of several diseases, including stroke, heart disease, aortic valve stenosis and chronic obstructive pulmonary disease. SUMMARY: Studies into the epigenetic regulation of the PON family are in their infancy. However, recent studies linking epigenetic regulation of PON1 to disease development will encourage further research and open up the possibility for new potential therapeutic interventions.

Phenotypes and concentration of PON1 in cardiovascular disease: The role of nutrient intake.

BACKGROUND AND AIMS: Paraoxonase 1 (PON1) is considered to play a crucial role as an anti-atherosclerotic factor. The PON1 activity is affected by genetic polymorphisms, environmental factors, age, sex, lifestyle, pharmaceutical drugs, and dietary factors. The aim of this study was to evaluate the association between macro- and micronutrients as well as PON1 concentration and activities in patients with cardiovascular diseases (CVD), cardiovascular risk factors but no CVD (CRF), and in healthy controls (control group). METHODS AND RESULTS: A case-control study was carried out with 356 volunteers from the Mexican Institute of Social Security, Mexico. Clinical parameters, lipid profile, PON1 activities (AREase, LACase, CMPAase and PONase), and PON1 concentration were evaluated. There was a differential intake of macro- and micronutrients among the study groups. The intake of proteins and carbohydrates was higher in the CVD group than in the CFR and control groups (p < 0.05). AREase, LACase, and CMPAase activities and PON1 concentration were lowest in the CVD group. CONCLUSION: LACase and CMPAase activities, as well as PON1 concentration, could be included in the battery of CVD predictive biomarkers in the Mexican population.

Coincubation of PON1, APO A1, and LCAT increases the time HDL is able to prevent LDL oxidation.

The inhibition of low-density lipoprotein (LDL) oxidation by high-density lipoprotein (HDL) is a major antiatherogenic property of this lipoprotein. This activity is due, in part, to HDL associated proteins. However, whether these proteins interact in the antioxidant activity of HDL is unknown. LDL was incubated with apolipoprotein A1 (apo A1), lecithin:cholesterol acyltransferase (LCAT), and paraoxonase-1 (PON1) alone or in combination, in the presence or absence of HDL under oxidizing conditions. LDL lipid peroxide concentrations were determined. Apo A1, LCAT, and PON1 all inhibit LDL oxidation in the absence of HDL and enhance the ability of HDL to inhibit LDL oxidation. Their effect was additive rather than synergistic; the combination of these proteins significantly enhanced the length of time LDL was protected from oxidation. This seemed to be due to the ability of PON1 to prevent the oxidative inactivation of LCAT. Apo A1, LCAT, and PON1 can all contribute to the antioxidant activity of HDL in vitro. The combination of apo A1, LCAT, and PON1 prolongs the time that HDL can prevent LDL oxidation, due, at least in part, to the prevention LCAT inactivation.

Paraoxonase-1 (PON-1) Arylesterase Activity Levels in Patients with Coronary Artery Disease: A Meta-Analysis.

Aim: To review and compare the PON-1 arylesterase activity between coronary artery disease (CAD) and non-CAD patients. Methods: Data were obtained by searching MEDLINE and Scopus for all investigations published between January 1, 2000 and March 1, 2021 comparing PON-1 arylesterase activity between CAD and controls. Results: Twenty studies, based on 5417 patients, met the inclusion criteria and were included in the analysis. A random effect model revealed that PON-1 arylesterase activity was significantly lower in the CAD group compared to controls (SMD = -0.587, 95%CI = -0.776 to -0.339, p < 0.0001, I 2 = 92.3%). In CAD patients, the PON-1 arylesterase activity was significantly higher among CAD patients without diabetes mellitus (DM) compared to those with diabetes (SMD: 0.235, 95% CI: 0.014 to 0.456, p = 0.03, I 2 = 0%). Conclusions: PON-1 activity is significantly lower in CAD patients, and those without DM presented a significantly higher PON-1 arylesterase activity.

Cholesteryl-ester transfer protein enhances the ability of high-density lipoprotein to inhibit low-density lipoprotein oxidation.

Therapeutic strategies to increase high-density lipoprotein (HDL) to treat or prevent vascular disease include the use of cholesteryl-ester transfer protein (CETP) inhibitors. Here, we show, to the best of our knowledge for the first time, that addition of CETP to HDL enhances the ability of HDL to inhibit low-density lipoprotein oxidation by ∼ 30% for total HDL and HDL(2) (both P < 0.05) and 75% for HDL(3) (P < 0.01). Therefore, CETP inhibition may be detrimental to the antiatherosclerotic properties of HDL, and these findings may partly explain the failure of the CETP inhibitor, torcetrapib, treatment to retard vascular disease despite large increases in HDL, in addition to its "off target" toxicity, a property which appears not to be shared by other members of this class of CETP inhibitor currently under clinical trial. Further, detailed studies are urgently required.

Immunohistochemical analysis of paraoxonases-1 and 3 in human atheromatous plaques.

BACKGROUND: The paraoxonase (PON) enzyme family comprising PON1, PON2 and PON3 are antioxidant enzymes that degrade bioactive oxidised lipids and are thus antiatherogenic. MATERIALS AND METHODS: We investigated the localisation of the PON proteins during the development of atherosclerosis by immunohistochemical analysis. RESULTS: In normal aortas, PON1 and PON3 were localised to smooth muscle cells (SMC) and endothelial cells. PON3 staining was stronger than that of PON1. During atherosclerosis development, SMC staining for PON1 and PON3 was greatly reduced, while macrophage staining for both proteins increased with PON1 predominating. Macrophage staining for PON1 and PON3 was significantly and positively related to the amount of aortic inflammation (both P<0·001). CONCLUSIONS: Our data add support to the growing body of evidence for a cellular protective effect of PON1 and PON3 against the proinflammatory/proatherosclerotic effects of lipid peroxidation.

Human tissue distribution of paraoxonases 1 and 2 mRNA.

We have studied the distribution of mRNA for paraoxonases (PON) 1 and 2 in 24 human tissues using Gene Expression Panels. PON1 mRNA was restricted to adult kidney, liver, and colon as well as fetal liver, whereas PON2 mRNA was more widely distributed in adult human brain, heart, kidney, spleen, liver, colon, lung, small intestine, muscle, stomach, testis, placenta, salivary, thyroid and adrenal glands, pancreas, skin, and bone marrow, as well as fetal brain and liver. PON2 mRNA was not found in ovary, uterus, or plasma leukocytes using the panels. However, using real time PCR, we found PON2 mRNA expression in human plasma leukocytes. There were differences between the tissue distribution of mRNAs found in this study and the immunohistochemical localization of the PON1 and PON2 proteins reported previously. In particular, PON1 protein is much more widely distributed than its mRNA, possibly indicating the delivery of PON1 to various tissues by HDL. In addition, differences between PON2 mRNA and protein distributions could be due to missence mutations in the PON2 gene, causing nontranslation of mRNA to protein in some tissues.

Anti-inflammatory properties of paraoxonase-1 in atherosclerosis.

Atherosclerosis is increasingly recognised as an inflammatory disease. The inflammatory process begins with the oxidation of low-density lipoprotein (LDL) in the artery wall. The ability of high-density lipoprotein (HDL) to inhibit the oxidation of LDL (and cell membranes) and promote macrophage cholesterol efflux through the action of several of its associated proteins, particularly paraoxonase-1 (PON1), reduces the inflammation associated with atherosclerosis. In vivo, in animal models, ablation of the PON1 gene is pro-inflammatory and pro-atherogenic, while overexpression of human PON1 is anti-inflammatory and anti-atherogenic. In subjects with diabetes mellitus, PON1 is dysfunctional due to glycation, reducing its ability to retard LDL and cell membrane oxidation and contributing to the inflammation typical of diabetes, leading to the excess atherosclerosis common in this disease.

PON1 lactonase activity and its association with cardiovascular disease.

BACKGROUND: Paraoxonase 1 (PON1) is important in the development of atherosclerosis, and it has become the subject of intensive research. Our aim was to evaluate the association of serum PON1 activity and polymorphisms with cardiovascular disease (CVD) using four different substrates. MATERIALS AND METHODS: Activity of PON1-related to arylesterase (AREase and 4-CMPAse), paraoxonase (PONase), and lactonase (LACase), and polymorphisms (A-162G, T-108C, L55M, and Q192R) were evaluated in subjects with CVD, cardiovascular risk factor (CFR), and controls. An ordered logistic-regression analysis of PON1 phenotypes was performed in the CVD group with respect to the control group. RESULTS AND CONCLUSIONS: Logistic-regression analysis showed that CC-108 genotype was associated with CRF and CVD. The CVD group had the lowest activities of PON1. The LACase might be a better biomarker for CVD (OR, 0.52; 95% CI, 0.44-0.61) followed by CMPAse (OR, 0.82; 95% CI, 0.77-0.86), AREase (OR, 0.98; 95% CI, 0.97-0.99) and PONase (OR, 0.99, 95% CI, 0.99-0.99). Logistic regression of PON1 phenotypes by haplotypes showed that LACase activity was not influenced by the polymorphisms and that it could be a new potential biomarker in the development of CVD. Larger scale longitudinal studies are required.

High-density lipoprotein: why all the fuss?

The current search for new treatments to combat coronary heart disease (CHD) is centred on increasing HDL-cholesterol. The failure of the CETP inhibitor torcetrapib may force a rethink. This perspective briefly reviews the antiatherosclerotic properties of HDL and ways HDL-cholesterol concentration can be raised, but argues - in light of the fact that HDL-cholesterol concentration does not reflect the protective properties of HDL particles - that this approach is flawed and a different approach, targeting know antiatherosclerotic components of HDL, is required.

Unexpectedly higher diazoxon hydrolysis by serum paraoxonase-1 in coronary heart disease.

OBJECTIVES: Low serum PON1 activities (paraoxon, phenyl-acetate or lactone substrates) are associated with coronary heart disease (CHD). We investigated the rate of diazoxon hydrolysis by PON1 in a population with CHD. DESIGN & METHODS: Case- control study of 410 subjects with CHD and 274 controls. PON1 activity towards paraoxon and diazoxon, PON1 serum concentration and the PON1-55 and 192 polymorphisms were determined. RESULTS: There were no differences in the distribution of the PON1-55 or PON1-192 genotypes between the CHD and controls, however, PON1 activity towards diazoxon (DIAZ) was significantly (+160%) higher in CHD. In the control population, DIAZ was significantly different between the PON1-192 genotypes in the order QQ > QR > RR (P < .001). However, in CHD the order was QQ > QR = RR. In CHD DIAZ was significantly higher in all the PON1-192 and 55 genotypes compared to controls. In both populations DIAZ was significantly different between the PON1-55 genotypes in the order LL > LM > MM (P < .001). CONCLUSION: If this result can be replicated in other studies and/or with other PON1 substrates, there may be major diagnostic and mechanistic implications for the relationship of PON1 and CHD.

The epigenetic regulation of paraoxonase 1 (PON1) as an important enzyme in HDL function: The missing link between environmental and genetic regulation.

BACKGROUND: Paraoxonase 1 (PON1) is an important antiatherogenic and antioxidant enzyme in the circulation that has been associated with adverse health outcomes particularly cardiovascular disease (CVD) and other metabolic disorders. PON1 is a highly promiscuous enzyme and can hydrolyse a large variety of substrates, however, detailed structure/function studies have concluded that the natural substrates for PON1 are lipophilic lactones. The interindividual variability in PON1 activity has been mainly attributed to genetic determinants; however, it appears that the contribution of epigenetics has been ignored as a result of the lack of adequate research. CONTENT: Epigenetic processes, including the histone modifications in the PON1 gene, the methylation of CpG sites in the promoter region of the PON1 gene and the microRNA modulation of PON1 expression can be responsible for the under researched gap between the environmental and genetic regulation of PON1. Environmental factors, including diet, pollution and lifestyle-related factors widely differ between individuals and populations and can cause large differences in the distribution of PON1 and it is important to note that their effects may be exerted through the epigenetic processes. This review discusses and emphasizes the importance of the epigenetic regulation of PON1 as a less-studied subject to highlight future research landscapes. SUMMARY: Epigenetic regulation is known as an important contributor to the pathogenesis of human diseases, particularly multifactorial diseases such as CVD, which is life-threatening. Due to the importance of PON1 in the functionality of high-density lipoprotein (HDL) and its association with CVD, further explorations of its epigenetic regulation using advanced methods such as Methyl-Seq may lead to the identification of new epigenetic contributors that in turn may lead to targeted therapies.

PON1 concentration and high-density lipoprotein characteristics as cardiovascular biomarkers.

INTRODUCTION: Serum paraoxonase 1 (PON1) is now known to be related to cardiovascular diseases (CVD). The aim of this study was to determine the relationship between PON1 concentration and high-density lipoprotein (HDL) subclasses in patients with proven CVD, cardiovascular risk factors but no CVD (CRF), and in healthy controls (control group). MATERIAL AND METHODS: A case-control study was carried out with 69 volunteers from the Mexican Institute of Social Security, Mexico. Clinical parameters, lipid profile, PON1 concentration, PON1 activities (AREase and CMPAase), and HDL subclasses were evaluated. RESULTS: Patients with CVD had significantly higher glucose and lower total cholesterol than the control group had (p < 0.01). AREase activity was not different between the control (122.57 ±30.72 U/ml), CRF (115.81 ±32.81 U/ml), and CVD (109.34 ±29.60 U/ml) groups. PON1 concentration was significantly lower in CVD patients than in CRF and control patients (p < 0.001); a positive correlation was observed between AREase activity and PON1 concentration in the CVD group (Rho = 0.58; p < 0.01). Logistic regression analysis showed that the decrease in PON1 level was associated with the CVD group (RRR = 0.20; 95% CI: 0.09-0.45) but not with the CRF group (RRR = 1.29; 95% CI: 0.89-1.90). Significant differences were observed in HDL 2a and HDL 3a concentrations between the control group and CRF and CVD groups (p < 0.05), but not between the CRF and CVD groups. CONCLUSIONS: Our data suggest that PON1 status and HDL characteristics could be early biomarkers that predict the potential for developing CVD.

Comparison of the ability of paraoxonases 1 and 3 to attenuate the in vitro oxidation of low-density lipoprotein and reduce macrophage oxidative stress.

In light of recent conflicting results regarding the antiatherogenic properties of the paraoxonase (PON) multigene family we have reexamined these properties in vitro. The abilities of recombinant human PON1 and PON3 to retard LDL oxidation, prevent macrophage oxidative stress, and promote macrophage cholesterol efflux were investigated. Both PON1 and PON3 retarded the oxidation of LDL; PON1 was significantly more efficient (50 and 100% at 20 microg PON3 and PON1, respectively (P<0.001)). Neither PON1 nor PON3 were able to prevent macrophage oxidative stress; however, both were able to retard macrophage-induced LDL oxidation (100 and 50% at 20 microg/ml respectively for PON1 and PON3, P<0.05). PON3 promoted macrophage cholesterol efflux (30% at 40 microg/ml, P<0.01); however, PON1 was found to be cytotoxic to the macrophages derived from the human monocyte THP-1 cell line. In conclusion using recombinant proteins we have been able to confirm some but not all of the antiatherosclerotic properties attributed to human PON1 and PON3 but have also discovered a novel cytotoxicity of PON1 toward macrophages derived from the human monocytic THP-1 cell line.

Defective metabolism of oxidized phospholipid by HDL from people with type 2 diabetes.

HDL protects against atherosclerosis development. Defective functioning of HDL in type 2 diabetes may be one cause of increased cardiovascular disease associated with type 2 diabetes. HDL modulates LDL oxidation through the action of paraoxonase-1 (PON1), which is one of the major mechanisms by which HDL is antiatherogenic. We have compared the ability of HDL from people with type 2 diabetes (n = 36) with no coronary heart disease (CHD) to metabolize oxidized palmitoyl arachidonyl phosphatidylcholine (ox-PAPC), a major product of LDL oxidation and a PON1 substrate, with that of HDL isolated from healthy control subjects (n = 19) and people with CHD but no diabetes (n = 37). HDL from people with type 2 diabetes metabolized 11% less ox-PAPC, and HDL from people with CHD metabolized 6% less, compared with HDL from control subjects (both P < 0.01). The ability of HDL from control and type 2 diabetic subjects containing the PON1-192RR alloform to metabolize ox-PAPC was significantly reduced compared with PON1-192QQ or QR genotypes (P < 0.05). The defective ability of HDL to metabolize ox-PAPC was reflected in a significant increase in circulating plasma oxidized LDL concentration in the two patient groups (37 +/- 5, 53 +/- 7, and 65 +/- 7 mmol/l for control, CHD, and type 2 diabetic subjects, respectively; P < 0.001), with PON1-192RR genotype carriers having the highest concentrations. In the control group, there was a significant negative correlation between serum PON1 activity and oxidized LDL concentration (r = 0.856, P < 0.001); however, this correlation was not evident in the patient groups. HDL from type 2 diabetic subjects without CHD had a decreased ability to metabolize oxidized phospholipids, which could lead to increased susceptibility to develop cardiovascular disease.

Human paraoxonase-1 overexpression inhibits atherosclerosis in a mouse model of metabolic syndrome.

BACKGROUND: The metabolic syndrome is typified by obesity, dyslipidemia, diabetes, hypertension, increased oxidative stress, and accelerated atherosclerosis. Paraoxonase1 (PON1), a high-density lipoprotein (HDL)-associated antioxidant enzyme that prevents the oxidation of low-density lipoprotein (LDL), is low in the metabolic syndrome. METHODS AND RESULTS: We used adenovirus-mediated PON1 gene transfer (AdPON1) to overexpress human PON1 in mice with combined leptin and LDL receptor deficiency, a model of metabolic syndrome. PON1 activity, plasma lipids, the titer of autoantibodies against malondialdehyde (MDA)-modified LDL, and atherosclerosis in AdPON1 mice were compared with these in mice that received a control recombinant adenovirus (AdRR5). PON1 activity was increased 4.4-fold (P<0.001) in AdPON1 mice (N = 12), whereas in AdRR5 mice (N = 11) activity did not change. Expressing human PON1 significantly reduced the total plaque volume, the volume of plaque macrophages, and of plaque-associated oxidized LDL. It increased the percentage of smooth muscle cells in the plaques. Expressing human PON1 lowered the titer of autoantibodies against MDA-modified LDL, a proxy for oxidized LDL in mice. It had no overall effect on plasma total cholesterol and triglycerides, as evidenced by the similar area under the curves, and on the HDL distribution profile. CONCLUSIONS: Our data suggest that in this mouse model of metabolic syndrome, expressing human PON1 inhibited the development of atherosclerosis, probably by reducing the amount of oxidized LDL in plasma and in the plaque, thereby preventing its proatherogenic effects. Adenovirus-mediated gene transfer of human PON1 may be a potential and useful tool to prevent/retard atherosclerosis in humans.

Transcriptional regulation of human Paraoxonase 1 by nuclear receptors.

Paraoxonase 1 (PON1) is a calcium-dependent lactonase synthesized primarily in the liver and secreted into the plasma, where it is associates with high density lipoproteins (HDL). PON1 acts as antioxidant preventing low-density lipoprotein (LDL) oxidation, a process considered critical in the initiation and progression of atherosclerosis. Additionally, PON1 hydrolyzes and detoxifies some toxic metabolites of organophosphorus compounds (OPs). Thus, PON1 activity and expression levels are important for determining susceptibility to OPs intoxication and risk of developing diseases related to inflammation and oxidative stress. Increasing evidence has demonstrated the modulation of PON1 expression by many factors is due to interaction with nuclear receptors (NRs). Here, we briefly review the studies in this area and discuss the role of nuclear receptors in the regulation of PON1 expression, as well as how understanding these mechanisms may allow us to manipulate PON1 levels to improve drug efficacy and treat disease.

Increased low-density lipoprotein oxidation and impaired high-density lipoprotein antioxidant defense are associated with increased macrophage homing and atherosclerosis in dyslipidemic obese mice: LCAT gene transfer decreases atherosclerosis.

BACKGROUND: Obesity-associated dyslipidemia in humans is associated with increased low-density lipoprotein (LDL) oxidation. Mice with combined leptin and LDL receptor deficiency are obese and show severe dyslipidemia and insulin resistance. We investigated the association between oxidation of apolipoprotein B-containing lipoproteins, high-density lipoprotein (HDL) antioxidant defense, and atherosclerosis in these mice. METHODS AND RESULTS: LDL receptor knockout (LDLR-/-), leptin-deficient (ob/ob), double-mutant (LDLR-/-;ob/ob), and C57BL6 mice were fed standard chow. Double-mutant mice had higher levels of non-HDL (P<0.001) and HDL (P<0.01) cholesterol and of triglycerides (P<0.001). They also had higher oxidative stress, evidenced by higher titers of autoantibodies against malondialdehyde-modified LDL (P<0.001). C57BL6 and ob/ob mice had no detectable lesions. Lesions covered 20% of total area of the thoracic abdominal aorta in double-mutant mice compared with 3.5% in LDLR-/- mice (P<0.01). Higher macrophage homing and accumulation of oxidized apolipoprotein B-100-containing lipoproteins were associated with larger plaque volumes in the aortic root of double-mutant mice (P<0.01). The activity of the HDL-associated antioxidant enzymes paraoxonase and lecithin:cholesterol acyltransferase (LCAT) (ANOVA; P<0.0001 for both) was lower in double-mutant mice. Adenovirus-mediated LCAT gene transfer in double-mutant mice increased plasma LCAT activity by 64% (P<0.01) and reduced the titer of autoantibodies by 40% (P<0.01) and plaque volume in the aortic root by 42% (P<0.05) at 6 weeks. CONCLUSIONS: Dyslipidemia and insulin resistance in obese LDL receptor-deficient mice are associated with increased oxidative stress and impaired HDL-associated antioxidant defense, evidenced by decreased paraoxonase and LCAT activity. Transient LCAT overexpression was associated with a reduction of oxidative stress and atherosclerosis.

Weight-loss-associated induction of peroxisome proliferator-activated receptor-alpha and peroxisome proliferator-activated receptor-gamma correlate with reduced atherosclerosis and improved cardiovascular function in obese insulin-resistant mice.

BACKGROUND: Weight loss in obese insulin-resistant but not in insulin-sensitive persons reduces coronary heart disease risk. To what extent changes in gene expression are related to atherosclerosis and cardiovascular function is unknown. METHODS AND RESULTS: We studied the effect of diet restriction-induced weight loss on gene expression in the adipose tissue, the heart, and the aortic arch and on atherosclerosis and cardiovascular function in mice with combined leptin and LDL-receptor deficiency. Obesity, hypertriglyceridemia, and insulin resistance are associated with hypertension, impaired left ventricular function, and accelerated atherosclerosis in those mice. Compared with lean mice, peroxisome proliferator-activated receptors (PPAR)-alpha and PPAR-gamma expression was downregulated in obese double-knockout mice. Diet restriction caused a 45% weight loss, an upregulation of PPAR-alpha and PPAR-gamma, and a change in the expression of genes regulating glucose transport and insulin sensitivity, lipid metabolism, oxidative stress, and inflammation, most of which are under the transcriptional control of these PPARs. Changes in gene expression were associated with increased insulin sensitivity, decreased hypertriglyceridemia, reduced mean 24-hour blood pressure and heart rate, restored circadian variations of blood pressure and heart rate, increased ejection fraction, and reduced atherosclerosis. PPAR-alpha and PPAR-gamma expression was inversely related to plaque volume and to oxidized LDL content in the plaques. CONCLUSIONS: Induction of PPAR-alpha and PPAR-gamma in adipose tissue, heart, and aortic arch is a key mechanism for reducing atherosclerosis and improving cardiovascular function resulting from weight loss. Improved lipid metabolism and insulin signaling is associated with decreased tissue deposition of oxidized LDL that increases cardiovascular risk in persons with the metabolic syndrome.