Circulating CD36 and oxLDL levels are associated with cardiovascular risk factors in young subjects

Air pollution and coronary atherosclerosis

The recently introduced concept of 'exposome' emphasizes the impact of non-traditional threats onto cardiovascular health. Among these, air pollutants - particularly fine particulate matter < 2.5 μm (PM2.5) - have emerged as significant environmental risk factors for cardiovascular disease and mortality. PM2.5 exposure has been shown to induce endothelial dysfunction, chronic low-grade inflammation, and cardiometabolic impairment, contributing to the development and destabilization of atherosclerotic plaques. Both short- and long-term exposure to air pollution considerably increase the incidence of ischemic heart disease (IHD)-related events, with clinical evidence linking pollution to higher mortality and adverse prognosis, especially in vulnerable populations. In this review, we explore the mechanistic pathways through which air pollutants exacerbate atherosclerotic cardiovascular disease (ASCVD) and discuss their clinical impact.Furthermore, special attention will be directed to the outcomes and prognosis of patients with pollution-aggravated coronary atherosclerosis, as well as the potential role of targeted public health interventions.

CD36-mediated podocyte lipotoxicity promotes foot process effacement

Background

Lipid metabolism disorders lead to lipotoxicity. The hyperlipidemia-induced early stage of renal injury mainly manifests as podocyte damage. CD36 mediates fatty acid uptake and the subsequent accumulation of toxic lipid metabolites, resulting in podocyte lipotoxicity.

Methods

Male Sprague-Dawley rats were divided into two groups: the normal control group and the high-fat diet group (HFD). Podocytes were cultured and treated with palmitic acid (PA) and sulfo-N-succinimidyl oleate (SSO). Protein expression was measured by immunofluorescence and western blot analysis. Boron-dipyrromethene staining and Oil Red O staining was used to analyze fatty acid accumulation.

Results

Podocyte foot process (FP) effacement and marked proteinuria occurred in the HFD group. CD36 protein expression was upregulated in the HFD group and in PA-treated podocytes. PA-treated podocytes showed increased fatty acid accumulation, reactive oxygen species (ROS) production, and actin cytoskeleton rearrangement. However, pretreatment with the CD36 inhibitor SSO decreased lipid accumulation and ROS production and alleviated actin cytoskeleton rearrangement in podocytes. The antioxidant N-acetylcysteine suppressed PA-induced podocyte FP effacement and ROS generation.

Conclusions

CD36 participated in fatty acid-induced FP effacement in podocytes via oxidative stress, and CD36 inhibitors may be helpful for early treatment of kidney injury.

Oral Supplement Containing Hydroxytyrosol and Punicalagin Improves Dyslipidemia in an Adult Population without Co-Adjuvant Treatment: A Randomized, Double-Blind, Controlled and Crossover Trial

Hydroxytyrosol (HT) and punicalagin (PC) exert cardioprotective and antiatherosclerotic effects. This study evaluated the effect of an oral supplement containing HT and PC (SAx) on dyslipidemia in an adult population. A randomized, double-blind, controlled, crossover trial was conducted over a 20-week period. SAx significantly reduced the plasma levels of triglycerides (TG) in subjects with hypertriglyceridemia (≥150 mg/dL) (from 200.67 ± 51.38 to 155.33 ± 42.44 mg/dL; p < 0.05), while no such effects were observed in these subjects after the placebo. SAx also significantly decreased the plasma levels of low-density lipoprotein cholesterol (LDL-C) in subjects with high plasma levels of LDL-C (≥160 mg/dL) (from 179.13 ± 16.18 to 162.93 ± 27.05 mg/dL; p < 0.01), while no such positive effect was observed with the placebo. In addition, the placebo significantly reduced the plasma levels of high-density lipoprotein cholesterol (HDL-C) in the total population (from 64.49 ± 12.65 to 62.55 ± 11.57 mg/dL; p < 0.05), while SAx significantly increased the plasma levels of HDL-C in subjects with low plasma levels of HDL-C (<50 mg/dL) (from 44.25 ± 3.99 to 48.00 ± 7.27 mg/dL; p < 0.05). In conclusion, the supplement containing HT and PC exerted antiatherosclerotic and cardio-protective effects by considerably improving dyslipidemia in an adult population, without co-adjuvant treatment or adverse effects.

Circulating CD36 is increased in hyperlipidemic mice: Cellular sources and triggers of release

CD36 is a multifunctional transmembrane glycoprotein abundantly expressed in several cell types. Recent studies have identified CD36 in circulation (cCD36) in several chronic inflammatory diseases, including type 2 diabetes and chronic kidney disease, and proposed cCD36 to be a biomarker of disease activity. Whether cCD36 is present in hyperlipidemia, a condition characterized by oxidative stress and low-grade inflammation, is not known. In addition, the cellular origin of cCD36 and triggers of CD36 release have not been elucidated. We now demonstrate that plasma cCD36 level is increased in hyperlipidemic ApoE^-/- and Ldlr^-/- mice. Using several cell-specific CD36 knockout mice, we showed that multiple cell types contribute to cCD36 generation in hyperlipidemic conditions, with a particularly strong contribution from endothelial cells. In vitro studies have demonstrated that oxidized phospholipids, ligands for CD36 (oxPC_CD36), which are known to accumulate in circulation in hyperlipidemia, induce a robust release of CD36 from several cell types. In vivo studies have demonstrated CD36 release into the circulation of WT mice in response to tail-vein injection of oxPC_CD36. These findings document the presence of cCD36 in hyperlipidemia and identify a link between cCD36 and oxidized phospholipids generated under oxidative stress and low-grade inflammation associated with hyperlipidemia.

Royal Jelly Proteins Inhibit Macrophage Proliferation: Interactions with Native- and Oxidized-Low Density Lipoprotein

Macrophage proliferation is known to correlate with macrophage accumulation in atherosclerotic plaque, and therefore its inhibition and secondary reduction of plaque inflammation may have therapeutic beneficial effects on atherosclerosis. Recently, we reported that a peptide corresponding to positions 41-51 of royalisin (which consists of 51 amino acid residues), a potent antibacterial protein contained in royal jelly (RJ), can specifically bind to oxidized LDL (Ox-LDL), a major components of atherosclerotic lesions. Here, we investigated the interaction of RJ proteins including royalisin with LDL and Ox-LDL. Measurement of LDL oxidation by the production of thiobarbituric acid reactive substances and conjugated dienes, and by electrophoretic mobility on polyacrylamide gel electrophoresis showed that RJ proteins including royalisin and the degradation products of major RJ protein (MRJP) 1 and MRJP3 can induce oxidation of LDL and Ox-LDL. Surface plasmon resonance experiments showed that these RJ proteins can exhibit much higher binding affinity to LDL than Ox-LDL (the equilibrium dissociation constant, K_D = 8.35 and 49.65 μg proteins/mL for LDL and Ox-LDL, respectively). Experiments using cultured mouse J774A.1 macrophage cells proved that these RJ proteins can inhibit macrophage proliferation markedly and concentration-dependently, regardless of the absence or presence of LDL and Ox-LDL, but hardly affect lipid accumulation in macrophages. These results suggest that RJ proteins including royalisin and degradation products of MRJP1/MRJP3 may have therapeutic beneficial effects on atherosclerosis owing to the reduction of plaque inflammation. Further studies of these RJ proteins may lead to the discovery of novel anti-atherosclerotic drugs.

A Novel Combination Therapy Using Rosuvastatin and Lactobacillus Combats Dextran Sodium Sulfate-Induced Colitis in High-Fat Diet-Fed Rats by Targeting the TXNIP/NLRP3 Interaction and Influencing Gut Microbiome Composition

Inflammasome targeting and controlling dysbiosis are promising therapeutic approaches to control ulcerative colitis. This report is the first to investigate the mechanisms underlying the coloprotective effects of rosuvastatin and Lactobacillus and their combined therapy on dextran sodium sulfate (DSS)-induced colitis in high-fat diet (HFD)-fed rats. Our results demonstrate the aggravation of intestinal inflammation as a consequence of an HFD following DSS administration. An association between dyslipidemia, LDL oxidation, CD36 expression, ROS generation, thioredoxin-interacting protein (TXNIP) upregulation, and NLRP3 inflammasome activation was demonstrated by DSS exposure in HFD-fed rats. We demonstrated that rosuvastatin/Lactobacillus significantly suppressed the DSS/HFD-induced increase in colon weight/length ratio, DAI, MDI, and myeloperoxidase, as well as corrected dysbiosis and improved histological characteristics. Additionally, caspase-1 activity and IL-1β-driven pyroptotic activity was significantly reduced. Rosuvastatin/Lactobacillus showed prominent anti-inflammatory effects as revealed by the IL-10/IL-12 ratio and the levels of TNF-α and IL-6. These latter effects may be attributed to the inhibition of phosphorylation-induced activation of NF-κB and a concomitant reduction in the expression of NLRP3, pro-IL-1β, and pro-IL-18. Furthermore, rosuvastatin/Lactobacillus reduced Ox-LDL-induced TXNIP and attenuated the inflammatory response by inhibiting NLRP3 inflammasome assembly. To conclude, rosuvastatin/Lactobacillus offers a safe and effective strategy for the management of ulcerative colitis.

Association of cardiometabolic risk status with clinical activity and damage in systemic lupus erythematosus patients: A cross-sectional study

Cardiometabolic status is a key factor in mortality by cardiovascular disease (CVD) in systemic lupus erythematosus (SLE). This study evaluated the association of cardiometabolic risk status with clinical activity and damage in SLE patients. A cross-sectional study was conducted in 158 SLE patients and 123 healthy subjects (HS). Anthropometry, glucose, hs-CRP, lipid profile, oxLDL, sCD36, anti-oxLDL antibodies, and cardiometabolic indexes were evaluated. SLE patients had dyslipidemia, higher sCD36, anti-oxLDL antibodies, hs-CRP, and risk (OR > 2) to present Castelli score ≥ 4.5, HDL-C < 40 mg/dL and LDL-C ≥ 100 mg/dL. Disease evolution time was correlated with glucose and BMI, damage with TG, and clinical activity with TG, TG/HDL-C ratio, and Kannel index. Active SLE patients had risk (OR > 2) to present a Castelli score ≥ 4.5, Kannel score ≥ 3, TG/HDL-C ratio ≥ 3 and HDL-C < 40 mg/dL. In conclusion, SLE patients have high cardiometabolic risk to CVD related to disease evolution time, and clinical activity.

The effects of exercise training on lipid metabolism and coronary heart disease

Blood lipoproteins are formed by various amounts of cholesterol (C), triglycerides (TGs), phospholipids, and apolipoproteins (Apos). ApoA1 is the major structural protein of high-density lipoprotein (HDL), accounting for ~70% of HDL protein, and mediates many of the antiatherogenic functions of HDL. Conversely, ApoB is the predominant low-density lipoprotein (LDL) Apo and is an indicator of circulating LDL, associated with higher coronary heart disease (CHD) risk. Thus, the ratio of ApoB to ApoA1 (ApoB/ApoA1) is used as a surrogate marker of the risk of CHD related to lipoproteins. Elevated or abnormal levels of lipids and/or lipoproteins in the blood are a significant CHD risk factor, and several studies support the idea that aerobic exercise decreases CHD risk by partially lowering serum TG and LDL-cholesterol (LDL-C) levels and increasing HDL-C levels. Exercise also exerts an effect on HDL-C maturation and composition and on reverse C transport from peripheral cells to the liver to favor its catabolism and excretion. This process prevents atherosclerosis, and several studies showed that exercise training increases heart lipid metabolism and protects against cardiovascular disease. In these and other ways, it more and more appears that regular exercise, nutrition, and strategies to modulate lipid profile should be viewed as an integrated whole. The purpose of this review is to assess the effects of endurance training on the nontraditional lipid biomarkers, including ApoB, ApoA1, and ApoB/ApoA1, in CHD risk.

Oral fatty acid taste sensitivity in healthy young individuals of both sexes is related to body mass index and soluble CD36 serum levels

Introduction

Introduction: CD36 is a membrane protein that functions as a lingual receptor for lipids. The soluble CD36 fraction (sCD36) may correlate oral fatty acid fat taste sensitivity to body mass index (BMI) and adiposity. Objectives: to determine if the oral fatty acid taste sensitivity in healthy young individuals of both sexes is related to serum sCD36 levels, adiposity and BMI. Methods: a cross-sectional study was conducted in 72 healthy young individuals (18-25 years). Serum sCD36 was quantified for all subjects. Oral fatty acid taste sensitivity was determined using an ascending series of the three-alternate forced choice methodology. Additionally, BMI was calculated using anthropometry, and adiposity was determined by bioelectric impedance analysis. Results: there was a positive correlation between BMI and the oral fatty acid taste sensitivity threshold (r = 0.277, p < 0.05) and a negative correlation between BMI and serum sCD36 levels (r = -0.035, p < 0.01). Adiposity negatively correlated with the sCD36 levels only in women (r = -0.359, p < 0.05). The threshold for oral sensitivity to fatty acids in overweight individuals was 1.0 (IQR 1.16) mM vs 0.2 (IQR 0.29) mM in healthy weight individuals (p < 0.05), while sCD36 levels were 26.1 pg/ml (IQR 32.9) and 77.97 pg/ml (IQR 560.66) in overweight and normal weight individuals, respectively (p < 0.05). Conclusions: BMI positively correlates with the oral sensitivity threshold of fatty acids and negatively correlates with serum sCD36 levels. The threshold of oral sensitivity to fatty acids was significantly higher in overweight subjects, while sCD36 levels were significantly higher in the group of normal weight individuals.

BLTR1 and CD36 Expressing Microvesicles in Atherosclerotic Patients and Healthy Individuals

Aims: Monocytes/macrophages play a crucial role in the development, progression, and complication of atherosclerosis. In particular, foam cell formation driven by CD36 mediated internalization of oxLDL leads to activation of monocytes and subsequent release of microvesicles (MVs) derived from monocytes (MMVs). Further, pro-inflammatory leukotriene B4 (LTB4) derived from arachidonic acid promotes atherosclerosis through the high-affinity receptor BLTR1. Thus, we aimed to investigate the correlation between different MMV phenotypes (CD14⁺ MVs) on the one hand, and arachidonic acid and eicosapentaenoic acid contents in different compartments including atherosclerotic plaques, plasma, and granulocytes on the other.

Methods and Results: Samples from patients with femoral atherosclerosis and healthy controls were analyzed on an Apogee A60 Micro-PLUS flow cytometer. Platelet-poor plasma was labeled with lactadherin-FITC, anti-CD14-APC, anti-CD36-PE, and anti-BLTR1-AF700. Eicosapentaenoic acid and arachidonic acid content in different compartments in patients were analyzed using gas chromatography. Compared to controls, patients had lower levels of BLTR1⁺ MVs (p = 0.007), CD14⁺BLTR1⁺ MVs (p = 0.007), and CD14⁺BLTR1⁺CD36⁺ MVs (p = 0.001). Further, in patients CD14⁺ MVs and CD14⁺CD36⁺ MVs correlated inversely with arachidonic acid in granulocytes (r = −0.302, p = 0.039 and r = −0.322, p = 0.028, respectively). Moreover, CD14⁺CD36⁺ MVs correlated inversely with arachidonic acid in plasma phospholipids in patients (r = −0.315, p = 0.029), and positively with triglyceride in both patients (r = 0.33, p = 0.019) and controls (r = 0.46, p = 0.022).

Conclusion: This is the first study of its kind and thus the results are explorative and only indicative. BLTR1⁺ MVs and CD14⁺CD36⁺ MVs has potential as markers of atherosclerosis pathophysiology, but this needs further investigation.

Platelet Activation and Platelet-Leukocyte Aggregates in Type I Diabetes Mellitus

Hyperglycemia alone may not explain the increased risk of cardiovascular diseases (CVDs) in patients with type 1 diabetes (T1D) compared with type 2. This study emphases on the evaluation of some platelet activity markers in patients with T1D, with relevance to some metabolic disorders as hyperlipidemia and hyperglycemia. This study was performed on 35 patients with T1D and 20 healthy controls. All participants were subjected to full history taking, clinical examination and assay of glycated hemoglobin (HbA_1c), and lipid profile. The expression of CD62P and CD36 on platelets and the frequency of platelet–monocyte, and platelet–neutrophil aggregates were assessed by flow cytometry. Patients showed significantly higher expression of CD62P and CD36 than the control group. Platelets aggregates with monocytes were also higher among patients than the control group. Levels of CD36⁺ platelets, CD62P⁺ platelets, and platelet–monocyte aggregates revealed significant correlations with the levels of HbA_1c, total cholesterol, low-density lipoprotein, and triglycerides. Hyperlipidemia and hyperglycemia accompanying T1D have a stimulatory effect on platelet activation which probably makes those patients vulnerable to CVD than nondiabetics.

Silica nanoparticles promote oxLDL-induced macrophage lipid accumulation and apoptosis via endoplasmic reticulum stress signaling

Oxidized low-density lipoprotein (oxLDL), a marker of hyperlipidemia, plays a pivotal role in the development of atherosclerosis through the induction of macrophage-derived foam cell formation and thereafter apoptosis. Previous studies have indicated that silica nanoparticle (SiNPs) may exert a proatherogenic role, which could induce endothelial dysfunction, and monocytes infiltration. However, little is known about SiNPs' effects on macrophage-derived foam cell formation and apoptosis in the pathogenesis of atherosclerosis. In this study, we investigated the effects of SiNPs and oxLDL coexposure on macrophage-derived lipid metabolism, foam cell and apoptosis by using Raw264.7 cells. As a result, SiNPs enhanced cytotoxicity, apoptosis, and lipid accumulation upon oxLDL stimulation. Furthermore, quantitative determination of the expression levels of genes involved in cholesterol influx or efflux showed significantly up-regulated expressions of CD36 and SRA, whereas down-regulated expressions of ATP-binding cassette A1 (ABCA1), ABCG1, and SRB1 in oxLDL-treated macrophages, especially upon the co-exposure with SiNPs. It indicated that SiNPs promoted lipid accumulation in macrophage cells through not only facilitating cholesterol influx but also inhibiting cholesterol efflux. Endoplasmic reticulum (ER) is specialized for the production, modification, even trafficking of lipids. Interestingly, ER response was triggered upon oxLDL treatment, while SiNPs coexposure augmented the ER stress. Taken together, our results revealed that SiNPs promoted oxLDL-induced macrophage foam cell formation and apoptosis, which may be mediated by ER stress signaling. Thus we propose future researches needed for a better understanding of NPs' toxicity and their interactions with various pathophysiological conditions.

Chondroitin Sulphate Attenuates Atherosclerosis in ApoE Knockout Mice Involving Cellular Regulation of the Inflammatory Response

Chondroitin sulphate (CS) has long been used to treat osteoarthritis. Some investigations have also shown that the treatment with CS could reduce coronary events in patients with heart disease but no studies have identified the mechanistic role of these therapeutic effects. We aimed to investigate how the treatment with CS can interfere with the progress of atherosclerosis. The aortic arch, thoracic aorta and serum were obtained from apolipoprotein E (ApoE) knockout mice fed for 10 weeks with high-fat diet and then treated with CS (300 mg/kg, n = 15) or vehicle (n = 15) for 4 weeks. Atheromatous plaques were highlighted in aortas with Oil Red staining and analysed by microscopy. ApoE knockout mice treated with CS exhibited attenuated atheroma lesion size by 68% as compared with animals receiving vehicle. Serum lipids, glucose and C-reactive protein were not affected by treatment with CS. To investigate whether CS locally affects the inflamed endothelium or the formation of foam cells in plaques, human endothelial cells and monocytes were stimulated with tumour necrosis factor α or phorbol myristate acetate in the presence or absence of CS. CS reduced the expression of vascular cell adhesion molecule 1, intercellular adhesion molecule 1 and ephrin-B2 and improved the migration of inflamed endothelial cells. CS inhibited foam cell formation in vivo and concomitantly CD36 and CD146 expression and oxidized low-density lipoprotein uptake and accumulation in cultured activated human monocytes and macrophages. Reported cardioprotective effects of CS may arise from modulation of pro-inflammatory activation of endothelium and monocytes and foam cell formation.

A fluorescently labeled undecapeptide derived from a protein in royal jelly of the honeybee-royalisin-for specific detection of oxidized low-density lipoprotein

The probes for detection of oxidized low-density lipoprotein (ox-LDL) in plasma and in atherosclerotic plaques are expected to facilitate the diagnosis, prevention, and treatment of atherosclerosis. Recently, we have reported that a heptapeptide (Lys-Trp-Tyr-Lys-Asp-Gly-Asp, KP6) coupled through the ε-amino group of N-terminal Lys to fluorescein isothiocyanate (FITC), (FITC)KP6, can be useful as a fluorescent probe for specific detection of ox-LDL. In the present study, to develop a novel fluorescent peptide for specific detection of ox-LDL, we investigated the interaction (with ox-LDL) of an undecapeptide corresponding to positions 41 to 51 of a potent antimicrobial protein (royalisin, which consists of 51 residues; from royal jelly of honeybees), conjugated at the N-terminus to FITC in the presence of 6-amino-n-caproic acid (AC) linker, (FITC-AC)-royalisin P11, which contains both sequences, Phe-Lys-Asp and Asp-Lys-Tyr, similar to Tyr-Lys-Asp in (FITC)KP6. The (FITC-AC)-royalisin P11 bound with high specificity to ox-LDL in a dose-dependent manner, through the binding to major lipid components in ox-LDL (lysophosphatidylcholine and oxidized phosphatidylcholine). In contrast, a (FITC-AC)-shuffled royalisin P11 peptide, in which sequences Phe-Lys-Asp and Asp-Lys-Tyr were modified to Lys-Phe-Asp and Asp-Tyr-Lys, respectively, hardly bound to LDL and ox-LDL. These findings strongly suggest that (FITC-AC)-royalisin P11 may be an effective fluorescent probe for specific detection of ox-LDL and that royalisin from the royal jelly of honeybees may play a role in the treatment of atherosclerosis through the specific binding of the region at positions 41 to 51 to ox-LDL.

Oxidized LDL triggers changes in oxidative stress and inflammatory biomarkers in human macrophages

Oxidized low-density lipoprotein (oxLDL) is a well-recognized proatherogenic particle that functions in atherosclerosis. In this study, we established conditions to generate human oxLDL, characterized according to the grade of lipid and protein oxidation, particle size and oxylipin content. The induction effect of the cellular proatherogenic response was assessed in foam cells by using an oxLDL-macrophage interaction model. Uptake of oxLDL, reactive oxygen species production and expression of oxLDL receptors (CD36, SR-A and LOX-1) were significantly increased in THP-1 macrophages. Analyses of 35 oxylipins revealed that isoprostanes (IsoP) and prostaglandins (PGs) derived from the oxidation of arachidonic, dihomo gamma-linolenic and eicosapentaenoic acids were strongly and significantly induced in macrophages stimulated with oxLDL. Importantly, the main metabolites responsible for the THP1-macrophage response to oxLDL exposure were the oxidative stress markers 5-epi-5-F_2t-IsoP, 15-E_1t-IsoP, 8-F_3t-IsoP and 15-keto-15-F_2t-IsoP as well as inflammatory markers PGDM, 17-trans-PGF_3α, and 11β-PGF_2α, all of which are reported here, for the first time, to function in the interaction of oxLDL with THP-1 macrophages. By contrast, a salvage pathway mediated by anti-inflammatory PGs (PGE₁ and 17-trans-PGF_3α) was also identified, suggesting a response to oxLDL-induced injury. In conclusion, when THP-1 macrophages were treated with oxLDL, a specific induction of biomarkers related to oxidative stress and inflammation was triggered. This work contributes to our understanding of initial atherogenic events mediated by oxLDL-macrophage interactions and helps to generate new approaches for their modulation.

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OxLDL has a potent impact on the oxylipin profiles in THP-1 human macrophages.

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OxLDL induces biomarkers of oxidation and inflammation in THP-1 human macrophages.

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Human Macrophages produce anti-inflammatory prostaglandins after oxLDL exposure.

Glycated albumin modifies platelet adhesion and aggregation responses

A diabetic vasculature is detrimental to cardiovascular health through the actions of advanced glycation end products (AGEs) on endothelial cells and platelets. Platelets activated by AGEs agonize endothelial responses promoting cardiovascular disease (CVD) development. While it has been established that AGEs can alter platelet functions, little is known about the specific platelet pathways that AGEs modify. Therefore, we evaluated the effects of AGEs on specific salient platelet pathways related to CVDs and whether the effects that AGEs elicit are dependent on glycation extent. To accomplish our objective, platelets were incubated with reversibly or irreversibly glycated albumin. A time course for adhesion and aggregation agonist receptor expression was assessed. Optical platelet aggregometry was used to confirm the functional activity of platelets after AGE exposure. In general, platelets subjected to glycated albumin had a significantly enhanced adhesion and aggregation potential. Furthermore, we observed an enhancement in dense body secretion and intracellular calcium concentration. This was especially prevalent for platelets exposed to irreversibly glycated albumin. Additionally, functional aggregation correlated well with receptor expression, suggesting that AGE-induced altered receptor sensitivity translated to altered platelet functions. Our findings indicate that under diabetic vascular conditions platelets become more susceptible to activation and aggregation due to an overall enhanced receptor expression, which may act to promote CVD development.

CD36 overexpression: a possible etiopathogenic mechanism of atherosclerosis in patients with prediabetes and diabetes

RATIONALE

CD36 is a scavenger receptor located on monocytes which is involved in foam cell transformation.

AIM

To evaluate CD36 expression under different glycemic states in both healthy subjects and in atherosclerotic patients.

SUBJECTS AND METHODS

In order to evaluate the possible effects of hyperglycemia on CD36 expression in healthy subjects, an in vitro experiment was carried out using monocyte in three different conditions: extreme hyperglycemia (HG), euglycemia (EG) and in the absence of glucose. On the other hand, three groups of atherosclerotic patients were evaluated according to their glycemic conditions: normoglycemic (NG), prediabetic (preDM) and diabetic (DM) patients. CD36 expression (mRNA, non-glycated and glycated protein) was analyzed in monocytes.

RESULTS

CD36 mRNA expression in the in vitro experiment peaked at 4 and 24 h under HG conditions. No differences in mRNA levels were found in the EG and control group. The level of non-glycated proteins was higher in HG and EG conditions compared with control group. Glycated protein expression was inhibited by glucose in a sustained manner. In atherosclerotic patients, a significant association was observed when comparing glycated CD36 protein expression in DM with NG patients (p = 0.03). No significant differences were found in mRNA and non-glycated CD36 expression in these patients. Moreover, BMI, insulin, weight and treatment were shown to be related to CD36 expression (mRNA, non-glycated and glycated protein levels, depending of the case) in atherosclerotic patients.

CONCLUSIONS

Hyperglycemia is an important modulator of CD36 mRNA and non-glycated protein expression in vitro, increasing de novo synthesis in healthy subjects. In atherosclerotic patients, there are progressive increases in CD36 receptors, which may be due to a post-translational stimulus.

Association of six CpG-SNPs in the inflammation-related genes with coronary heart disease

Background

Chronic inflammation has been widely considered to be the major risk factor of coronary heart disease (CHD). The goal of our study was to explore the possible association with CHD for inflammation-related single nucleotide polymorphisms (SNPs) involved in cytosine-phosphate-guanine (CpG) dinucleotides. A total of 784 CHD patients and 739 non-CHD controls were recruited from Zhejiang Province, China. Using the Sequenom MassARRAY platform, we measured the genotypes of six inflammation-related CpG-SNPs, including IL1B rs16944, IL1R2 rs2071008, PLA2G7 rs9395208, FAM5C rs12732361, CD40 rs1800686, and CD36 rs2065666). Allele and genotype frequencies were compared between CHD and non-CHD individuals using the CLUMP22 software with 10,000 Monte Carlo simulations.

Results

Allelic tests showed that PLA2G7 rs9395208 and CD40 rs1800686 were significantly associated with CHD. Moreover, IL1B rs16944, PLA2G7 rs9395208, and CD40 rs1800686 were shown to be associated with CHD under the dominant model. Further gender-based subgroup tests showed that one SNP (CD40 rs1800686) and two SNPs (FAM5C rs12732361 and CD36 rs2065666) were associated with CHD in females and males, respectively. And the age-based subgroup tests indicated that PLA2G7 rs9395208, IL1B rs16944, and CD40 rs1800686 were associated with CHD among individuals younger than 55, younger than 65, and over 65, respectively.

Conclusions

In conclusion, all the six inflammation-related CpG-SNPs (rs16944, rs2071008, rs12732361, rs2065666, rs9395208, and rs1800686) were associated with CHD in the combined or subgroup tests, suggesting an important role of inflammation in the risk of CHD.

Soluble cluster of differentiation 36 concentrations are not associated with cardiovascular risk factors in middle-aged subjects

Cluster of differentiation 36 (CD36) is involved in the development of atherosclerosis by enhancing macrophage endocytosis of oxidized low-density lipoproteins and foam cell formation. Soluble CD36 (sCD36) was found to be elevated in type 2 diabetic patients and possibly acted as a marker of insulin resistance and atherosclerosis. In young subjects, sCD36 was associated with cardiovascular risk factors including obesity and hypertriglyceridemia. The present study was conducted to further investigate the association between plasma sCD36 and cardiovascular risk factors among middle-aged patients with metabolic syndrome (MetS) and healthy controls. sCD36 concentrations were determined by enzyme-linked immunosorbent assays (ELISA) for 41 patients with MetS and 36 healthy controls. Data for other variables were obtained from patient medical records. sCD36 concentrations were relatively low compared to the majority of other studies and were not significantly different between the MetS group and controls (P=0.17). sCD36 was also not correlated with age, body mass index, glucose, lipid profile, serum electrolytes and blood counts. sCD36 was not significantly different between subjects with obesity, hyperglycemia, dyslipidemia, hypertension or cardiovascular disease, and those without these abnormalities (P>0.05). The inconsistency between results reported in the present study and other studies may be unique to the study population or be a result of the lack of a reliable standardized method for determining absolute sCD36 concentrations. However, further investigations are required to assess CD36 tissue expression in the study population and to assess the accuracy of various commercially available sCD36 ELISA kits. Thus, the availability of a standardized simple sCD36 ELISA that could be performed in any basic laboratory would be more favorable to the specialized flow cytometry methods that detect CD36+ microparticles if it was to be used as a biomarker.

New circulating biomarkers for predicting cardiovascular death in healthy population

There is interest to analyse newer biomarkers to identify healthy individuals at risk to develop cardiovascular disease (CVD) incidents and death. To determine in healthy individuals new circulating protein biomarkers, whose systemic levels may be associated with the risk of future development of CVD incidents and death. The study was performed in 82 individuals from the Malmö Diet and Cancer study cohort, free from CVD of whom 41 developed CVD and 41 did not. Plasma proteins related to inflammation and thrombo-coagulating processes were analysed. α1-antitrypsin isotype 3 plasma levels were significantly higher while apolipoprotein J plasma levels were lower in participants that developed CVD incidents than those that did not develop acute cardiovascular episode. Of 82 participants, 17 died by CVD causes. There were proteins whose expression in plasma was significantly higher in participants suffering CVD death as compared with those that did not die by CVD. These proteins included: fibrinogen β-chain isotypes 1 and 3, fibrinogen-γ-chain isotype 2, vitamin D-binding protein isotypes 1, 2 and 3, α1-antitrypsin isotypes 3 and 6, haptoglobin isotypes 3,4,5 and 5, haemopexin isotypes 1 and 2, and Rho/Rac guanine nucleotide exchange factor 2. Moreover, apolipoprotein J plasma levels were found lower in participants that died by cardiovascular cause. Association between plasma levels of proteins and CVD death was independent of age, gender, conventional risk factors and plasma C-reactive protein levels. Several protein plasma levels and protein isotypes related to inflammation and thrombo-coagulating phenomena were independently associated with the risk of future CVD death.

Association of chemical constituents and pollution sources of ambient fine particulate air pollution and biomarkers of oxidative stress associated with atherosclerosis: A panel study among young adults in Beijing, China

Ambient particulate air pollution has been associated with increased oxidative stress and atherosclerosis, but the chemical constituents and pollution sources behind the association are unclear. We investigated the associations of various chemical constituents and pollution sources of ambient fine particles (PM2.5) with biomarkers of oxidative stress in a panel of 40 healthy university students. Study participants underwent repeated blood collections for 12 times before and after relocating from a suburban campus to an urban campus with high air pollution levels in Beijing, China. Air pollution data were obtained from central air-monitoring stations, and plasma levels of oxidized low-density lipoprotein (Ox-LDL) and soluble CD36 (sCD36) were determined in the laboratory (n=464). Linear mixed-effects models were used to estimate the changes in biomarkers in association with exposure variables. PM2.5 iron and nickel were positively associated with Ox-LDL (p<0.05). For each interquartile range increase in iron (1-day, 0.51 μg/m(3)) and nickel (2-day, 2.5 ng/m(3)), there were a 1.9% [95% confidence interval (CI): 0.2%, 3.7%] increase and a 1.8% (95% CI: 0.2%, 3.4%) increase in Ox-LDL, respectively. We also found that each interquartile range increase in calcium (1-day, 0.7 μg/m(3)) was associated with a 4.8% (95% CI: 0.7%, 9.1%) increase in sCD36. Among the pollution sources, PM2.5 from traffic emissions and coal combustion were suggestively and positively associated with Ox-LDL. Our findings suggest that a subset of metals in airborne particles may be the major air pollution components that contribute to the increased oxidative stress associated with atherosclerosis.

Nonalcoholic fatty liver disease and type 2 diabetes: common pathophysiologic mechanisms

Nonalcoholic fatty liver disease (NAFLD) is an independent risk factor for advanced liver disease, type 2 diabetes (T2DM), and cardiovascular diseases. The prevalence of NAFLD in the general population is around 30 %, but it is up to three times higher in those with T2DM. Among people with obesity and T2DM, the NAFLD epidemic also is worsening. Therefore, it is important to identify early metabolic alterations and to prevent these diseases and their progression. In this review, we analyze the pathophysiologic mechanisms leading to NAFLD, particularly, those common to T2DM, such as liver and muscle insulin resistance. However, it is mainly adipose tissue insulin resistance that results in increased hepatic de novo lipogenesis, inflammation, and lipotoxicity. Although genetics predispose to NAFLD, an unhealthy lifestyle, including high-fat/high-sugar diets and low physical activity, increases the risk. In addition, alterations in gut microbiota and environmental chemical agents, acting as endocrine disruptors, may play a role.

Targeting the adaptive immune system: new strategies in the treatment of atherosclerosis

Atherosclerosis is a lipid-driven chronic inflammatory disease of the arterial wall. Current treatment of atherosclerosis is focused on limiting its risk factors, such as hyperlipidemia or hypertension. However, treatments that target the inflammatory nature of atherosclerosis are still under development. Discovery of novel targets involved in the inflammation of the arterial wall creates opportunities to design new therapeutics that successfully modulate atherosclerosis. Here, we review drug targets that have proven to play pivotal roles in the adaptive immune system in atherosclerosis, and we discuss their potential as novel therapeutics.

Soluble CD36 in plasma and urine: a plausible prognostic marker for diabetic nephropathy

AIMS

This study was designed to analyze the level of soluble CD36 (sCD36) in both plasma and urine of type 2 diabetic patients with and without microalbuminuria/macroalbuminuria.

METHODS

Study subjects (n=20 each) comprised of those with normal glucose tolerance, type 2 diabetes (T2DM) with normoalbuminiria, T2DM with microalbuminuria and T2DM with macroalbuminuria. The biochemical parameters were analyzed using auto-analyzer, and the level of sCD36 was estimated using an in-house Sandwich ELISA.

RESULTS

The presence of sCD36 has been identified for the first time in the urine sample. Significant increase in the level of sCD36 was observed in both plasma and urine of diabetic patients with microalbuminuria (P<0.01) and macroalbuminuria (P<0.001). Positive correlation of sCD36 with the kidney markers such as urea, creatinine and eGFR confirmed the association of sCD36 with kidney damage in diabetic patients. Microalbuminuria, which is clinically used as a biomarker for nephropathy showed a strong positive correlation with urine sCD36 (r=0.642; P<0.001) and plasma sCD36 (r=0.498; P<0.001) in Pearson correlation analysis, which was further substantiated in stepwise multiple regression analysis.

CONCLUSIONS

Our study implies a plausible prognostic/adjuvant biomarker role of soluble CD36 for diabetic nephropathy.

CD36 binds oxidized low density lipoprotein (LDL) in a mechanism dependent upon fatty acid binding

The association of unesterified fatty acid (FA) with the scavenger receptor CD36 has been actively researched, with focuses on FA and oxidized low density lipoprotein (oxLDL) uptake. CD36 has been shown to bind FA, but this interaction has been poorly characterized to date. To gain new insights into the physiological relevance of binding of FA to CD36, we characterized FA binding to the ectodomain of CD36 by the biophysical method surface plasmon resonance. Five structurally distinct FAs (saturated, monounsaturated (cis and trans), polyunsaturated, and oxidized) were pulsed across surface plasmon resonance channels, generating association and dissociation binding curves. Except for the oxidized FA HODE, all FAs bound to CD36, with rapid association and dissociation kinetics similar to HSA. Next, to elucidate the role that each FA might play in CD36-mediated oxLDL uptake, we used a fluorescent oxLDL (Dii-oxLDL) live cell assay with confocal microscopy imaging. CD36-mediated uptake in serum-free medium was very low but greatly increased when serum was present. The addition of exogenous FA in serum-free medium increased oxLDL binding and uptake to levels found with serum and affected CD36 plasma membrane distribution. Binding/uptake of oxLDL was dependent upon the FA dose, except for docosahexaenoic acid, which exhibited binding to CD36 but did not activate the uptake of oxLDL. HODE also did not affect oxLDL uptake. High affinity FA binding to CD36 and the effects of each FA on oxLDL uptake have important implications for protein conformation, binding of other ligands, functional properties of CD36, and high plasma FA levels in obesity and type 2 diabetes.

Efficacy of dipeptidyl peptidase-4 inhibitor linagliptin in patients with type 2 diabetes undergoing hemodialysis

BACKGROUND

Incretin therapy is feasible in patients with type 2 diabetes mellitus undergoing hemodialysis (HD). However, few studies have examined the safety and efficacy of this therapeutic approach in patients with diabetes and renal impairment. Here, we examined glycemic control and the anti-oxidative-stress effects of the dipeptidyl peptidase (DPP)-4 inhibitor linagliptin in patients with type 2 diabetes undergoing HD.

METHODS

Thirty-five patients with type 2 diabetes undergoing HD (including 13 insulin-treated patients) were switched from ongoing therapy to linagliptin (5 mg, once daily). Levels of fasting blood glucose, C-peptide immunoreactivity (CPR), glycated albumin, B-type natriuretic peptide, oxidized low-density lipoprotein (oxLDL), high-sensitivity C-reactive protein, 8-hydroxy-2'-deoxyguanosine (8OHdG), body mass index, blood pressure, and other biologic characteristics (liver function, renal function, lipid profile) were determined before and 3 months after linagliptin treatment. Patients were classified into insulin-treated and non-insulin groups.

RESULTS

With the exception of levels of total bilirubin, aspartate aminotransferase, and CPR, none of the patients exhibited changes in glucose metabolism after switching to linagliptin treatment. However, oxLDL levels were decreased significantly by linagliptin therapy in the non-insulin-treated group despite the absence of changes in glycemic control.

CONCLUSION

Linagliptin can decrease serum levels of oxLDL in patients with type 2 diabetes undergoing HD independent of its glucose-lowering effect.

Highly stable, fluorescence-labeled heptapeptides substituted with a D-amino acid for the specific detection of oxidized low-density lipoprotein in plasma

Probes that can detect oxidized low-density lipoprotein (ox-LDL) in plasma and in atherosclerotic plaques can be useful for the diagnosis, prevention, and treatment of atherosclerosis. Recently, we have reported that two heptapeptides (Lys-Trp-Tyr-Lys-Asp-Gly-Asp, KP6) coupled to fluorescein isothiocyanate (FITC) through the ε-amino group of N-terminus Lys in the absence/presence of 6-amino-n-caproic acid (AC) linker to FITC-(FITC)KP6 and (FITC-AC)KP6-can be useful as fluorescent probes for the specific detection of ox-LDL. In this study, to develop the fluorescent peptides with high plasma stability for the specific detection of ox-LDL, we investigated the interaction of (FITC)KP6 and (FITC-AC)KP6 substituted with D-Lys at the N-terminus-(FITC)dKP6 and (FITC-AC)dKP6-with ox-LDL, and the in vitro stability of these peptides in mouse plasma. (FITC)dKP6 and (FITC-AC)dKP6 bound with high specificity to ox-LDL in a dose-dependent manner, and also to ox-LDL in the mouse plasma. Furthermore, (FITC)dKP6 was more stable than (FITC)KP6 in mouse plasma (102.1% versus 69.0% remained after 1 h). These findings strongly suggest that (FITC)dKP6 and (FITC-AC)dKP6 may be effective fluorescent probes with higher plasma stability than (FITC)KP6 and (FITC-AC)KP6 for the specific detection of ox-LDL.