Acid In Atherosclerosis Research Articles

Uric acid in atherosclerosis and cardiovascular diseases: innocent bystander or ruthless killer?

Medical attention to uric acid (UA) has been increasing in recent years, mainly because this molecule has been shown to be associated with increased cardiovascular risk, both in the general population and in the hypertensive patients. A growing body of clinical and experimental data supports this view and prompts reconsideration of the role of UA in the development of atherosclerosis and the genesis of cardiovascular disease. It is known that this substance, in certain plasma concentrations, induces increased oxidative stress, a chronic inflammatory state, and a whole series of other modifications that are potentially deleterious at the cardiovascular level leading to hypertension, atherosclerosis, atrial fibrillation (AF), and other metabolic changes such as diabetes, metabolic syndrome, non-alcoholic fatty liver disease and kidney failure. Despite this epidemiologic and mechanistic evidence, the current guidelines from international cardiology scientific societies do not give precise indications in this regard, and some of them only suggest UA evaluation as part of an initial screening of the hypertensive patient. The purpose of this review is to briefly describe the main clinical and epidemiological evidence supporting the role of hyperuricemia as a possible emerging cardiovascular risk factor and to analyze the potential pathophysiological mechanisms through which elevated UA levels may exert a detrimental effect on the cardiovascular system.

Purine-ifying uric acid by gut microbes

Elevated bloodstream levels of uric acid, a mammalian purine degradation product, are associated with several noncommunicable diseases. Recent studies by Kasahara etal. and Liu etal. define purine-degrading activities of the gut microbiota that lower bloodstream uric acid in atherosclerosis and gout disease models, establishing a novel microbial role in host health.

Sialic acids promote macrophage M1 polarization and atherosclerosis by upregulating ROS and autophagy blockage

Accumulating evidence suggests that sialic acids is closely related to atherosclerosis. However, the effects and underlying mechanisms of sialic acids in atherosclerosis have been not defined. Macrophages are one of the most important cells during plaque progression. In this study, we investigated the role of sialic acids in the M1 macrophage polarization and pathogenesis of atherosclerosis. Here we found that sialic acids can promote the polarization of RAW264.7 cells to the M1 phenotype, thereby promoting the expression of proinflammatory cytokines in vitro. The proinflammatory effect of sialic acids may result from the inhibition of LKB1-AMPK-Sirt3 signaling pathway to upregulate intracellular ROS and impairing autophagy-lysosome system to block autophagic flux. In the APOE−/− mice, sialic acids in plasma increased during the development of atherosclerosis. Moreover, exogenous supplement of sialic acids can promote plaque progression in aortic arch and aortic sinus being accompanied by the differentiation of macrophages into M1 type in peripheral tissues. These studies demonstrated that sialic acids can promote macrophage polarization toward the M1 phenotype to accentuate atherosclerosis via inducing mitochondrial ROS and blocking autophagy, thus providing clue to a novel therapeutic strategy for atherosclerosis.

Mechanism of action and therapeutic use of bempedoic acid in atherosclerosis and metabolic syndrome.

Bempedoic acid is a new cholesterol-lowering drug, which has recently received US FDA and EMA approval. This drug targets lipid and glucose metabolism as well as inflammation via downregulation of ATP-citrate lyase and upregulation of AMP-activated protein kinase (AMPK). The primary effect is the reduction of cholesterol synthesis in the liver and its administration is generally not associated to unwanted muscle effects. Suppression of hepatic fatty acid synthesis leads to decreased triglycerides and, possibly, improved non-alcoholic fatty liver disease. Bempedoic acid may decrease gluconeogenesis leading to improved insulin sensitivity, glucose metabolism, and metabolic syndrome. The anti-inflammatory action of bempedoic acid is mainly achieved via activation of AMPK pathway in the immune cells, leading to decreased plasma levels of C-reactive protein. Effects of bempedoic acid on atherosclerotic cardiovascular disease, type 2 diabetes and chronic liver disease have been assessed in randomized clinical trials but require further confirmation. Safety clinical trials in phase III indicate that bempedoic acid administration is generally well-tolerated in combination with statins, ezetimibe, or proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitors to achieve low-density lipoprotein cholesterol targets. The aim of this narrative review on bempedoic acid is to explore the underlying mechanisms of action and potential clinical targets, present existing evidence from clinical trials, and describe practical management of patients.

The Critical Effect of Bile Acids in Atherosclerosis.

Atherosclerosis (AS) is one of the most common cardiovascular diseases and is the leading cause of arteriosclerotic cardiovascular disease. Bile acids are not only the products of cholesterol metabolism, but also an important class of signaling molecules. Bile acids exert their biological effects through the bile acid receptor signaling pathways. Bile acid receptors are widely distributed in human organs and tissues. The activation of transcriptional and signaling cascades controls bile acid metabolism and synthesis, lipid and carbohydrate metabolism, immune cell expression, and inflammatory responses. A large body of evidence indicates that bile acids play an important role in the initiation and development of AS, and are strongly associated with AS risk factors. The major bile acid receptors, nuclear receptor farnesoid X receptor (liver) and membrane receptor G protein-coupled receptor 5, exhibit anti-atherosclerotic effects. Other nuclear receptors exert different anti-atherosclerotic or pro-atherosclerotic effects. In this review, we summarize the current knowledge on the effects of bile acids and their receptors in AS and explore the pathway of bile acids involved in atherosclerotic lesions. The main research based on animal models or cell/tissue culture experiments is also discussed. This review provides new ideas for the development of novel therapeutic approaches for AS prevention and treatment.

Metformin intervention ameliorates AS in ApoE-/- mice through restoring gut dysbiosis and anti-inflammation.

Atherosclerosis (AS) is closely associated with chronic low-grade inflammation and gut dysbiosis. Metformin (MET) presents pleiotropic benefits in the control of chronic metabolic diseases, but the impacts of MET intervention on gut microbiota and inflammation in AS remain largely unclear. In this study, ApoE-/- mice with a high-fat diet (HFD) were adopted to assess the MET treatment. After 12 weeks of MET intervention (100mg·kg-1·d-1), relevant indications were investigated. As indicated by the pathological measurements, the atherosclerotic lesion was alleviated with MET intervention. Moreover, parameters in AS including body weights (BWs), low-density lipoprotein (LDL), triglyceride (TG), total cholesterol (TC) and malondialdehyde (MDA) were elevated; whereas high-density lipoprotein (HDL) and total superoxide dismutase (T-SOD) levels were decreased, which could be reversed by MET intervention. Elevated pro-inflammatory interleukin (IL)-1β, IL-6, tumor necrosis factor (TNF)-α and lipopolysaccaride (LPS) in AS were decreased after MET administration. However, anti-inflammatory IL-10 showed no significant difference between AS group and AS+MET group. Consistently, accumulated macrophages in the aorta of AS were conversely lowered with MET treatment. The results of 16S rRNA sequencing and analysis displayed that the overall community of gut microbiota in AS was notably changed with MET treatment mainly through decreasing Firmicutes, Proteobacteria, Romboutsia, Firmicutes/Bacteroidetes, as well as increasing Akkermansia, Bacteroidetes, Bifidobacterium. Additionally, we found that microbiota-derived short-chain fatty acids (SCFAs) including acetic acid, propionic acid, butyric acid and valeric acid in AS were decreased, which were significantly up-regulated with MET intervention. Consistent with the attenuation of MET on gut dysbiosis, decreased intestinal tight junction protein zonula occludens-1 (ZO)-1 in AS was restored after MET supplementation. Correlation analysis showed close relationships among gut bacteria, microbial metabolites SCFAs and inflammation. Collectively, MET intervention ameliorates AS in ApoE-/- mice through restoring gut dysbiosis and anti-inflammation, thus can potentially serve as an inexpensive and effective intervention for the control of the atherosclerotic cardiovascular disease.

The Impact of Omega 3 Fatty Acids in Atherosclerosis and Arterial Stiffness: An Overview of their Actions

Fatty acids are common dietary nutrients particularly in economically developed countries. Research has revealed that omega-3fatty acids exert beneficial effects in the progression of atherosclerosis and cardiovascular disease. Moreover, eicosapentaenoic acid and docosahexaenoic acid possess a number of biological actions which improve cardio-metabolic health. Omega-3 fatty acids display remarkable anti-oxidant, anti-inflammatory, anti-thrombotic and anti-arrhythmogenic actions. Furthermore, they improve the levels of triglycerides, glucose metabolism and endothelial function. The aim of this review article is to present physical, biochemical and biological properties of omega-3 fatty acids and summarize the most important mechanisms of action on arterial wall properties and arterial stiffness in atherosclerosis. Omega-3 fatty acids may prevent the progression of atherosclerosis. Endothelial dysfunction and arterial stiffness can be regulated by the supplementation of omega-3 fatty acids. The mechanisms of action of omega-3 fatty acids on cardiovascular health and arterial stiffening have been established. However, further research is needed in order to translate the conflicting results among the studies and improve the therapeutic options of cardiovascular disease.

Specific Amino Acids Affect Cardiovascular Diseases and Atherogenesis via Protection against Macrophage Foam Cell Formation: Review Article.

The strong relationship between cardiovascular diseases (CVD), atherosclerosis, and endogenous or exogenous lipids has been recognized for decades, underestimating the contribution of other dietary components, such as amino acids, to the initiation of the underlying inflammatory disease. Recently, specific amino acids have been associated with incident cardiovascular disorders, suggesting their significant role in the pathogenesis of CVD. Special attention has been paid to the group of branched-chain amino acids (BCAA), leucine, isoleucine, and valine, since their plasma values are frequently found in high concentrations in individuals with CVD risk. Nevertheless, dietary BCAA, leucine in particular, have been associated with improved indicators of atherosclerosis. Therefore, their potential role in the process of atherogenesis and concomitant CVD development remains unclear. Macrophages play pivotal roles in the development of atherosclerosis. They can accumulate high amounts of circulating lipids, through a process known as macrophage foam cell formation, and initiate the atherogenesis process. We have recently screened for anti- or pro-atherogenic amino acids in the macrophage model system. Our study showed that glycine, cysteine, alanine, leucine, glutamate, and glutamine significantly affected macrophage atherogenicity mainly through modulation of the cellular triglyceride metabolism. The anti-atherogenic properties of glycine and leucine, and the pro-atherogenic effects of glutamine, were also confirmed in vivo. Further investigation is warranted to define the role of these amino acids in atherosclerosis and CVD, which may serve as a basis for the development of anti-atherogenic nutritional and therapeutic approaches.

Omega-3 fatty acids in atherosclerosis and coronary artery disease.

Omega-3 polyunsaturated fatty acids have emerged as possible protective factors associated with a decreased risk for myocardial infarction in populations with a high marine food intake, which may relate to effects on lipid metabolism, thrombosis and inflammation. Omega-3 fatty acids decrease triglyceride levels and also compete as substrates for enzymes involved in the biosynthesis of lipid mediators. The balance between omega-3-derived specialized proresolving mediators and pro-inflammatory lipid mediators from arachidonic acid metabolism can be measured as the resolvin-to-leukotriene ratio, which has been shown to predict subclinical atherosclerosis. The results of experimental, observational and randomized studies of omega-3 fatty acids are somewhat variable and should be interpreted in view of the models used and the populations studied.

Linoleic Acid: A Nutritional Quandary.

Over the course of the twentieth century, there was a 20-fold increase in consumption of vegetable oils resulting both from their increased availability and from recommendations to consume these oils as an aid to lower blood cholesterol levels. This dietary change markedly increased the consumption of linoleic acid to current levels of approximately 6% of total dietary energy. While considerable research has focused on the effects of dietary linoleic acid on cardiovascular health, questions about optimum dietary levels remain. For example, meta-analyses disagree about the role of dietary linoleic acid in atherosclerosis, and recent publications indicate that linoleic acid’s reduction of blood cholesterol levels does not predict its effect on the development of atherosclerosis. Further, there are also detrimental effects of elevated dietary linoleic acid on human health related to its role in inflammation and its activity as a promoter of cancer in animals. Current data do not allow determination of the level of dietary linoleic acid needed for optimum health. Studies of the effects of a wide range of linoleic acid consumption may help determine dietary recommendations that are optimal for human health.

Potential Pathways Involved in Elaidic Acid Induced Atherosclerosis in Human Umbilical Vein Endothelial Cells

Researches have demonstrated that trans-fatty acids are related to the progression of atherosclerosis, but the underlying mechanism is not clear till now. In the presented study, two-dimensional electrophoresis based proteomics was used to discover the role of elaidic acid in atherosclerosis. In human umbilical vein endothelial cells (HUVEC), twenty-two and twenty-three differentially expressed proteins were identified in low (50 μmol/L) and high (400 μmol/L) concentration elaidic acid simulated groups, respectively, comparing with the control group. The expressions of some selected proteins (PSME3, XRCC5, GSTP1, and GSTO1) were validated by qRT-PCR analysis. Western blotting analysis further confirmed that elaidic acid downregulated the expression of PSME3and XRCC5. Moreover, P53, the downstream protein of PSME3, was further investigated. Results demonstrated that a variety of proteins, many of which were related to oxidative stress, apoptosis, and DNA damage, were involved in the elaidic acid induced atherosclerosis. Furthermore, P53 was demonstrated to regulate the atherosclerosis through cell cycle arrest and apoptosis pathway.

Decreased urine uric acid excretion is an independent risk factor for chronic kidney disease but not for carotid atherosclerosis in hospital-based patients with type 2 diabetes: a cross-sectional study.

BackgroundThe associations between urine uric acid excretion (UUAE) and chronic kidney disease (CKD)/atherosclerosis have not been investigated. Our aims were to investigate the relationships between UUAE and CKD and carotid atherosclerotic lesions in hospitalized Chinese patients with type 2 diabetes.MethodsThis was a cross-sectional study that was conducted with 2627 Chinese inpatients with type 2 diabetes. UUAE was determined enzymatically using a single 24-h urine collection. The subjects were stratified into quartiles according to their UUAE levels. Carotid atherosclerotic lesions, including carotid intima-media thickness (CIMT), plaque and stenosis, were assessed by Doppler ultrasound. Both CKD and carotid atherosclerotic lesions were compared between the UUAE quartile groups.ResultsAfter adjustment for confounding factors, there was a significant decrease in the prevalence of CKD in the patients with type 2 diabetes across the UUAE quartiles (16.9%, 8.5%, 5.9%, and 4.9%; p < 0.001). Multiple logistic regression analyses revealed that the UUAE quartiles were significantly and inversely associated with the presence of CKD (p < 0.001). Compared with the diabetics in the highest UUAE quartile, those in the lowest quartile exhibited a nearly 4.2-fold increase in the risk of CKD (95% CI: 2.272-7.568; p < 0.001). The CIMT value (0.91 ± 0.22 mm for the diabetics with CKD and 0.82 ± 0.20 mm for the diabetics without CKD, p = 0.001) and the prevalence of carotid plaques (62.1% for the diabetics with CKD and 41.8% for the diabetics without CKD, p = 0.025) were significantly higher in the diabetics with CKD than in those without CKD. However, there was no obvious difference in carotid atherosclerotic lesions across the UUAE quartiles after controlling for the confounding factors.ConclusionsDecreased UUAE was closely associated with the presence of CKD but not with carotid atherosclerotic lesions in hospitalized Chinese patients with type 2 diabetes. Our results suggest that UUAE is an independent risk factor for CKD in type 2 diabetes. In selected populations, such as patient with type 2 diabetes, the role of uric acid in atherosclerosis might be the result of other concomitant atherosclerotic risk factors, such as CKD.

Serum uric acid levels are associated with hypertension and metabolic syndrome but not atherosclerosis in Chinese inpatients with type 2 diabetes.

Objective:Serum uric acid (SUA) is associated with many cardiovascular risk factors such as hypertension (HTN) and metabolic syndrome (MetS). However, the association of SUA with atherosclerosis remains controversial. Our aim was to investigate the relationships of SUA with HTN, MetS and atherosclerosis in Chinese inpatients with type 2 diabetes.Methods:This cross-sectional study was performed with a sample of 2388 hospitalized Chinese patients with type 2 diabetes. Both carotid and lower limb atherosclerotic lesions were assessed for intima–media thickness, plaque and stenosis by Doppler ultrasound. Atherosclerotic plaque and stenosis were defined as the presence of either carotid or lower limb plaques and stenoses, respectively.Results:There were significant increases in the prevalence of both HTN and MetS across the SUA quartiles (HTN: 43.4, 49.6, 56.1 and 66.3% for the first, second, third and fourth quartiles, respectively, P < 0.001; MetS: 59.9, 68.8, 74.7 and 84.9% for the first, second, third and fourth quartiles, respectively, P < 0.001). A fully adjusted multiple logistic regression analysis revealed that SUA quartile was independently associated with the presence of HTN (P = 0.001) and MetS (P = 0.006). The prevalence of atherosclerotic plaque and stenosis was obviously higher in the patients with either HTN or MetS than in those without HTN or MetS. However, there was no significant association of SUA quartile with the presence of atherosclerotic lesions.Conclusions:SUA levels were closely associated with HTN and MetS, but not with atherosclerosis in type 2 diabetes. Our findings strongly suggest that, in select populations such as those with type 2 diabetes, the role of uric acid in atherosclerosis might be attributable to other cardiovascular risk factors, such as HTN and MetS.

Effects of nicotinic acid on endothelial cells and platelets

Interactions between platelets and endothelial cells under inflammatory conditions lead to an increased expression of various activity markers of atherosclerosis in the vessel wall. The purpose of this study was to investigate possible protective effects of nicotinic acid in an in vitro endothelial cell model. After a 24-hour incubation period with nicotinic acid (1 mmol/l), human umbilical vein endothelial cells were stimulated for 1 h with lipopolysaccharide and were then incubated in direct contact with activated platelets. Following this incubation, the expression of CD40L and CD62P on platelets and the expression of intercellular adhesion molecule (ICAM)-1, vascular cell adhesion molecule (VCAM)-1, uPAR, and MT1-MMP on endothelial cells were measured by flow cytometry. Supernatants were analyzed by ELISA for soluble MCP-1 and MMP-1. The increased expression of VCAM-1 on endothelial cells by proinflammatory stimulation with activated platelets was significantly reduced through preincubation with nicotinic acid (P<.05). Furthermore, platelets in direct contact with preincubated endothelial cells showed a significant reduction in their CD62P and CD40L expression when compared to platelets incubated with untreated endothelial cells (P<.05). Treatment with nicotinic acid did not have a significant effect on ICAM-1, uPAR, and MT1-MMP expression on endothelial cells. Levels of soluble MCP-1 and MMP-1 in supernatants were lower after preincubation with nicotinic acid. Nicotinic acid inhibits platelet activation after platelets contacted nicotinic acid treated endothelial cells and inhibits VCAM-1 expression on human endothelial cells under inflammatory conditions. These findings suggest a possible pleiotropic therapeutic relevance of nicotinic acid in atherosclerosis.

Higher reactivity of apolipoprotein B-100 and α-tocopherol compared to sialic acid moiety of low-density lipoprotein (LDL) in radical reaction

Radical reaction of low-density lipoprotein (LDL) is a key step in atherogenesis and causes both a decrease in the sialic acid moiety and modification of apolipoprotein B-100 (apoB). Although apoB modification (cross-link and fragmentation) increases in atherosclerosis, the change in apoB-bound sialic acid in atherosclerosis is controversial. To elucidate the physiological implications of desialylation of LDL by radical reaction, the reactivity of sialic acid of LDL was compared with that of apoB, which underwent facile fragmentation in radical reactions. ApoB was determined by immunoblot analysis with anti-apoB antiserum, and the sialic acid moiety was measured by blot analysis with a biotin-bound lectin [biotin-SSA from Japanese elderberry (Sambucus sieboldiana)] specific to sialic acid. When human LDL was oxidized with Cu 2+ at 37 °C, apoB and apoB-attached sialic acid decreased simultaneously. Comparison of the staining bands with anti-apoB and with biotin-SSA shows that sialic acid moieties still remain on fragmented apoB proteins, indicating that the decrease in sialic acid is much slower than that of apoB fragmentation. In addition, human plasma was oxidized with 400 μM of Cu 2+ at 37 °C. Similar analysis indicates that the decrease in sialic acid attached to apoB also results from the fragmentation of apoB. This study indicates that the fragmentation of apoB proceeds at a much faster rate than the decrease in sialic acid content when a free radical reaction is induced in isolated LDL as well as in plasma LDL exposed to Cu 2+-induced oxidative stress. On the basis of these results, the modification of apoB is much more sensitive than the decrease in sialic acid as an indicator of oxidative stress.

The role of fibric acids in atherosclerosis

The hypolipidemic fibric acid drugs are peroxisome proliferator-activated receptor a (PPAR alpha) ligands. PPAR alpha activated by fibric acids form heterodimers with the 9-cis retinoic acid receptor (RXR). The PPAR/RXR heterodimers bind to peroxisome proliferator response elements (PPRE), which are located in numerous gene promoters and increase the level of the expression of mRNAs encoded by PPAR alpha target genes. Fibric acids decrease triglyceride plasma levels through increases in the expression of genes involved in fatty acid-beta oxidation. Furthermore, they decrease triglycerides by increasing lipoprotein lipase gene expression and by decreasing apolipoprotein C-III gene expression. Fibric acids increase high-density lipoprotein (HDL) cholesterol partly by increasing apolipoprotein A-I and apolipoprotein A-II gene expression. Fibric acids also reduce vascular wall inflammation and the expression of genes involved in different vascular functions (ie, vasomotricity, thrombosis). Fibric acids are used to treat primary hypertriglyceridemia and mixed hyperlipidemia. Some fibric acid molecules are active in essential hypercholesterolemia. Clinical evidence shows that fibric acids reduce coronary atherosclerosis progression in dyslipidemic patients (eg, bezafibrate, gemfibrozil) and in type 2 diabetic patients (fenofibrate). Gemfibrozil decreases coronary morbidity and mortality in patients with low HDL cholesterol, normal triglycerides,and normal low-density lipoprotein (LDL) cholesterol plasma levels. Further clinical studies are necessary to investigate if fibric acids decrease cardiovascular mortality in type 2 diabetes and in primary prevention of hypertriglyceridemia and hypolipidemia.

The role of dietary fatty acids in lipoprotein oxidation and atherosclerosis.

Although it is well established that dietary saturated fatty acid intake is an important risk factor for coronary heart disease, there remains substantial controversy regarding whether these dietary fatty acids should be replaced with either carbohydrates, monounsaturated fatty acids, polyunsaturated fatty acids or a combination of these. This review highlights recent studies evaluating the role of dietary fatty acids in atherosclerosis, with a particular emphasis on their roles in lipoprotein oxidation and other potential proatherogenic processes.

Omega-6 and omega-3 essential fatty acids in atherosclerosis.

Omega-6 and omega-3 essential fatty acids in atherosclerosis.

Possible Role of Dietary Proteins and Amino Acids in Atherosclerosisa

Possible Role of Dietary Proteins and Amino Acids in Atherosclerosis^a

Carnitine palmitoyltransferase activity in mitochondrial fractions isolated from aortas of rabbits fed cholesterol-supplemented diets

β-Oxidation of long-chain fatty acids increases many-fold in atherosclerotic aortas; this may be due to an increase in the activity of the mitochondrial enzyme hexadecanoyl-CoA: carnitine O-hexadecanoyltransferase EC 2.3.1.23 (trivial name: carnitine palmitoyltransferase, CPT). To investigate this possibility, an assay for arterial CPT was developed and used to measure CPT activity in mitochondrial fractions isolated from aortas of rabbits fed high-fat (HF) or high-fat plus cholesterol (HFC) supplemented diets. The arterial CPT assay was linear with respect to mitochondrial protein between 0.03 and 0.30 mg and assay time between 3 and 12 min. Maximum CPT activity was observed at concentrations of palmitoyl-CoA between 5 and 25 μm, higher concentrations of palmitoyl-CoA inhibited CPT activity. CPT activity was measured in mitochondrial fractions isolated from aortas of rabbits fed the HFC-supplemented diet for up to 48 days. No visible lesions were observed in aortas of rabbits fed HFC-diet for 3, 9, or 21 days, however, by 48 days atheromatous lesions covered in excess of 60% of the intimal surface of the aorta. No lesions were visually observed in aortas of rabbits receiving the HF-diet. Despite the development of gross atherosclerotic lesions, there were no changes in CPT activity observed that could account for a dramatic increase in fatty acid oxidation. It is concluded that the increase in β-oxidation of long-chain fatty acids in atherosclerosis is not attributable to an increase in CPT activity.