Immunohistochemical detection of oxidative stress biomarkers, dityrosine and N(epsilon)-(hexanoyl)lysine, and C-reactive protein in rabbit atherosclerotic lesions

The oral microbiome in the pathophysiology of cardiovascular disease

Despite advances in our understanding of the pathophysiology of many cardiovascular diseases (CVDs) and expansion of available therapies, the global burden of CVD-associated morbidity and mortality remains unacceptably high. Important gaps remain in our understanding of the mechanisms of CVD and determinants of disease progression. In the past decade, much research has been conducted on the human microbiome and its potential role in modulating CVD. With the advent of high-throughput technologies and multiomics analyses, the complex and dynamic relationship between the microbiota, their 'theatre of activity' and the host is gradually being elucidated. The relationship between the gut microbiome and CVD is well established. Much less is known about the role of disruption (dysbiosis) of the oral microbiome; however, interest in the field is growing, as is the body of literature from basic science and animal and human investigations. In this Review, we examine the link between the oral microbiome and CVD, specifically coronary artery disease, stroke, peripheral artery disease, heart failure, infective endocarditis and rheumatic heart disease. We discuss the various mechanisms by which oral dysbiosis contributes to CVD pathogenesis and potential strategies for prevention and treatment.

Reversible Oxidative Modifications in Myoglobin and Functional Implications

Myoglobin (Mb), an oxygen-binding heme protein highly expressed in heart and skeletal muscle, has been shown to undergo oxidative modifications on both an inter- and intramolecular level when exposed to hydrogen peroxide (H₂O₂) in vitro. Here, we show that exposure to H₂O₂ increases the peroxidase activity of Mb. Reaction of Mb with H₂O₂ causes covalent binding of heme to the Mb protein (Mb-X), corresponding to an increase in peroxidase activity when ascorbic acid is the reducing co-substrate. Treatment of H₂O₂-reacted Mb with ascorbic acid reverses the Mb-X crosslink. Reaction with H₂O₂ causes Mb to form dimers, trimers, and larger molecular weight Mb aggregates, and treatment with ascorbic acid regenerates Mb monomers. Reaction of Mb with H₂O₂ causes formation of dityrosine crosslinks, though the labile nature of the crosslinks broken by treatment with ascorbic acid suggests that the reversible aggregation of Mb is mediated by crosslinks other than dityrosine. Disappearance of a peptide containing a tryptophan residue when Mb is treated with H₂O₂ and the peptide’s reappearance after subsequent treatment with ascorbic acid suggest that tryptophan side chains might participate in the labile crosslinking. Taken together, these data suggest that while exposure to H₂O₂ causes Mb-X formation, increases Mb peroxidase activity, and causes Mb aggregation, these oxidative modifications are reversible by treatment with ascorbic acid. A caveat is that future studies should demonstrate that these and other in vitro findings regarding properties of Mb have relevance in the intracellular milieu, especially in regard to actual concentrations of metMb, H₂O₂, and ascorbate that would be found in vivo.

The effect of resveratrol supplementation on C-reactive protein (CRP) in type 2 diabetic patients: Results from a systematic review and meta-analysis of randomized controlled trials

OBJECTIVE

C-reactive protein (CRP) is considered to be an inflammatory marker in type 2 diabetes (T2D) and it is produced by liver cells. The evidence has suggested that resveratrol has anti-inflammatory effect. This study aimed to evaluate the effect of resveratrol supplementation on CRP level in patients with T2D using a systematic review and meta-analysis of randomized controlled trials.

METHODS

Electronic databases were completely searched using Medline, ISI Web of Science, EMBASE and Cochrane Library and Scopus until October 2019. Meta-analysis was performed using random-effects model and inverse variance method. Heterogeneity and publication bias were evaluated in selected studies. Sensitivity analyses and prespecified subgroup were conducted to evaluate potential heterogeneity. Meta-regression was performed to assess the effect of potential confounders on the estimated effect sizes.

RESULTS

Six trials comprising a total of 491 subjects were included in this meta-analysis. The results showed significant reduction in the level of CRP [SMD (-0.34 mg/l) (95 % CI, -0.52, to -0.16) p < 0.05] in participants with T2D following supplementation with resveratrol. No significant publication bias was observed in the meta-analysis. Subgroup and sensitivity analyses indicated that the pooled effects of resveratrol supplementation on CRP level in T2D patients were affected by resveratrol dose and duration of resveratrol. Random-effects meta-regression did not indicate any significant association of CRP level with potential confounders including resveratrol dose, duration of treatment, age and gender of type 2 diabetic patients.

CONCLUSION

We found a significant reduction in CRP level in patients with type 2 diabetes, who received resveratrol supplementation.

Investigation of hallmarks of carbonyl stress and formation of end products in feline chronic kidney disease as markers of uraemic toxins

OBJECTIVES

Cats are commonly affected by chronic kidney disease (CKD). Many reactive carbonyl intermediates and end products originating from the oxidative stress pathways are recognised as uraemic toxins and may play a role in CKD progression. The aim of the present study is to confirm whether carbonyl end-product formation is higher in cats affected by CKD and to assess whether an angiotensin-converting enzyme inhibitor (ACEi) might affect these hallmarks.

METHODS

Twenty-two cats were divided into three groups: a control group (CG), cats with CKD and cats with CKD treated with an ACEi. Serum levels of pentosidine, carboxymethyllysine, advanced oxidation protein products, malondialdehyde, methylglyoxal and hexanoyl-lysine were measured. In addition, biochemical parameters and systolic blood pressure were evaluated. After checking for normality, comparisons between groups were performed followed by multiple comparison tests. P values ⩽0.05 were considered significant. Correlations between concentrations of the considered biomarkers and of the other metabolic parameters were investigated.

RESULTS

Advanced oxidation protein products, malondialdehyde and hexanoyl-lysine concentrations were significantly higher in CKD and ACEi-treated groups compared with the CG ( P <0.05). Carboxymethyllysine increased in the ACEi-treated group when compared with the CG, whereas intermediate values of these biomarkers were found in the CKD group ( P <0.05). The ACEi-treated group showed the highest values of carboxymethyllysine, advanced oxidation protein products and hexanoyl-lysine. By contrast, the CKD group had the highest concentration of malondialdehyde. No statistically significant difference was found in the levels of pentosidine or methylglyoxal. End products correlated with creatinine and urea and with each other.

CONCLUSIONS AND RELEVANCE

Significantly high concentrations of both intermediate and end products of carbonyl/oxidative stress were detected in CKD cats. This is the first study to have concurrently taken into account several uraemic toxins and biochemical parameters in cats affected by CKD.

Association of C-Reactive Protein with Risk of Developing Type 2 Diabetes Mellitus, and Role of Obesity and Hypertension: A Large Population-Based Korean Cohort Study

This study was undertaken to assess the associations of C-reactive protein (CRP) with incident type-2 diabetes mellitus (T2DM) and to determine the joint effect of obesity and hypertension on them in the large-scale population-based Korean cohort of the Korean Genome and Epidemiology study (KoGES). We included 22,946 men and women from 11 rural communities at baseline (2005–2011). Epidemiological data and blood samples were collected. Incident physician-diagnosed T2DM cases (130 men and 148 women) were self-reported or based on fasting glucose ≥126 mg/dL or HbA1c level ≥6.5% during a median follow-up of 3.0 years (58,916 person-years) between 2007 and 2014. After multivariate adjustment for T2DM risk factors, the hazard ratios for developing T2DM in the highest CRP tertile (T3), compared with the lowest (T1), was 2.80 (1.73–4.52; p for trend <0.0001) in women and 1.67 (1.00–2.45; p for trend 0.02) in men. The associations between CRP and incident T2DM were more prominent among the older group (≥50 years). And CRP and its combination with obesity and hypertension were associated with increased risk of T2DM. In conclusion, we found positive associations between CRP and incident T2DM in a large population-based Korean cohort.

Comparison of oxidative stress on DNA, protein and lipids in patients with actinic keratosis, Bowen's disease and squamous cell carcinoma

Detailed mechanisms on the effect of oxidative stress (OS), an etiological factor involved in photocarcinogenesis, remain to be fully elucidated. We used immunohistochemical methods to study OS in the DNA, protein and lipids of patients with actinic keratosis (AK), Bowen's disease (BD) and squamous cell carcinoma (SCC). Between January 2009 and December 2014, we treated 230 patients; 79 had AK, 61 had (BD) and 90 had cutaneous SCC; 28 healthy subjects served as the normal controls. OS on DNA, protein and lipids was assessed by the expression of 8-hydroxydeoxyguanosine (8-OHdG), dityrosine (DT) and malondialdehyde (MDA), respectively. 8-OHdG was significantly overexpressed in AK and BD lesions compared with surrounding non-lesional tissue, SCC lesions and the healthy controls. DT was more highly expressed in AK, BD and SCC than in the controls. There was no significant difference among AK, BD and SCC. The expression of MDA was higher in AK, BD and SCC lesions than the controls; SCC showed the highest expression. Our observations suggest that DNA oxidation plays an important role in the early stage of carcinogenesis, that protein oxidation is involved in all stages of carcinogenesis and that lipid oxidation is strongly implicated in the late stages of carcinogenesis.

Development and application of oxidative stress biomarkers

Oxidative stress may cause a wide variety of free radical reactions to produce deleterious modifications in membranes, proteins, enzymes, and DNA. Reactive Oxygen Species (ROS) generated by myeloperoxidase (MPO) can induce lipid peroxidation and also play an important role in the generation of reactive chlorinating and brominating species. As the universal biomarkers, chemical, and immunochemical approach on oxidatively modified and halogenated tyrosines has been carried out. As amido-type adduct biomarkers, chemical, and immunochemical evaluation of hexanoyl- and propanoyl-lysines, hexanoyl- and propanoyl-dopamines and phospholipids were prepared and developed for application of evaluation of novel antioxidative functional food factors. We have also involved in application of oxidatively modified DNAs such as 8-hydroxy- and 8-halogenated deoxyguanosines as the useful biomarkers for age-related diseases using both in vitro and in vivo systems. Application of these oxidative stress biomarkers for novel type of functional food development and recent approach for development of novel evaluation systems are also discussed.

Untargeted metabolomics of colonic digests reveals kynurenine pathway metabolites, dityrosine and 3-dehydroxycarnitine as red versus white meat discriminating metabolites

Epidemiological research has demonstrated that the consumption of red meat is an important risk factor for the development of colorectal cancer (CRC), diabetes mellitus and cardiovascular diseases. However, there is no holistic insight in the (by-) products of meat digestion that may contribute to disease development. To address this hiatus, an untargeted mass spectrometry (MS)-based metabolomics approach was used to create red versus white meat associated metabolic fingerprints following in vitro colonic digestion using the fecal inocula of ten healthy volunteers. Twenty-two metabolites were unequivocally associated with simulated colonic digestion of red meat. Several of these metabolites could mechanistically be linked to red meat-associated pathways including N'-formylkynurenine, kynurenine and kynurenic acid (all involved in tryptophan metabolism), the oxidative stress marker dityrosine, and 3-dehydroxycarnitine. In conclusion, the used MS-based metabolomics platform proved to be a powerful platform for detection of specific metabolites that improve the understanding of the causal relationship between red meat consumption and associated diseases.

Effects of dietary oxidized tyrosine products on insulin secretion via the thyroid hormone T3-regulated TRβ1–Akt–mTOR pathway in the pancreas

Oxidized tyrosine products (OTPs) have been detected in commercial foods with high protein content.

Effect of dietary oxidized tyrosine products on insulin secretion via the oxidative stress-induced mitochondria damage in mice pancreas

The findings suggested that decreased insulin secretion triggered by OTPs may be mediated by oxidative stress and mitochondrial damage in pancreatic β cells.

A novel quinone derived from 5-hydroxyindoleacetic acid reacts with protein: Possible participation of oxidation of serotonin and its metabolite in the development of atherosclerosis

The modification of 5-hydroxyindoleacetic acid (5HIAA) by myeloperoxidase with a xanthine oxidase system was investigated by chromatographic analyses. Two major products were identified as a dimer and quinone (indoleacetate dione) of 5HIAA. The formation of a quinone moiety was also confirmed by chemical trapping with o-phenylenediamine. In the presence of N-acetyl-cysteine (NAC), a quinone-NAC adduct was formed. When glyceraldehyde 3-phosphate dehydrogenase was exposed to the myeloperoxidase system with 5HIAA, quinone adducts were formed on the protein molecule. A monoclonal antibody was prepared using a quinone-modified protein as an immunogen to immunochemically detect the quinone on a protein. The established antibody recognized the quinone-NAC adduct, quinone-modified poly-L-lysine, and quinone-modified low-density lipoprotein. Quinone-modified proteins in human atherosclerotic lesions were immunohistochemically observed using the established antibody to the quinone and also a monoclonal antibody to tryptamine dione-modified protein, suggesting an occurrence of in vivo oxidation of serotonin and 5HIAA, accompanied by covalent adduction to biomolecules.

Intraplaque Expression of C-Reactive Protein Predicts Cardiovascular Events in Patients with Severe Atherosclerotic Carotid Artery Stenosis

Serum c-reactive protein (CRP) was suggested for the assessment of intermediate cardiovascular (CV) risk. Here, systemic or intraplaque CRP levels were investigated as predictors of major adverse cardiovascular events (MACEs) in patients with severe carotid stenosis. CRP levels were assessed in the serum and within different portions (upstream and downstream) of carotid plaques of 217 patients undergoing endarterectomy. The association between CRP and intraplaque lipids, collagen, neutrophils, smooth muscle cells (SMC), and macrophage subsets was determined. No correlation between serum CRP and intraplaque biomarkers was observed. In upstream portions, CRP content was directly correlated with intraplaque neutrophils, total macrophages, and M1 macrophages and inversely correlated with SMC content. In downstream portions, intraplaque CRP correlated with M1 and M2 macrophages. According to the cut-off point (CRP > 2.9%) identified by ROC analysis in upstream portions, Kaplan-Meier analysis showed that patients with high CRP levels had a greater rate of MACEs. This risk of MACEs increased independently of age, male gender, serum CRP, and statin use. In conclusion, in patients with severe carotid artery stenosis, high CRP levels within upstream portions of carotid plaques directly and positively correlate with intraplaque inflammatory cells and predict MACEs at an 18-month follow-up period.

Accumulation of C-reactive protein in basal keratinocytes of normal skins

BACKGROUND

C-reactive protein (CRP) is a prototypic acute phase protein which increases dramatically in the blood during the first 48h of tissue inflammation and has been recognized as a risk factor for atherosclerosis. CRP interacts with a variety of proteins.

OBJECTIVE

To know the role of accumulated CRP in the skin.

METHODS

Interaction of CRP with basal keratinocytes was studied using immunohistochemical method and keratinocyte culture system.

RESULTS

We found an immunohistochemical deposition of CRP on the basal keratinocyte membrane in some normal human skins (23 out of 46 skins). When added to cultured keratinocytes, heat-denatured but not native CRP was found to adhere to keratinocyte cell membrane after 1h, then internalized into cytoplasm after 24h. The heat-denatured CRP recognized at least four keratinocyte polypeptides with the molecular weights of 56, 42, 32 and 24kDa. Ligand binding assays suggested that multiple populations of receptor-ligand interactions were involved in the binding between CRP and keratinocyte. Cultured dermal microvascular endothelial cells were found to express CRP of which expression was greatly induced by interleukin-1β (IL-1β) treatment, suggesting that the deposited CRP in the basal keratinocytes can be derived from local dermal microvasculatures as well as from systemic circulation (serum). Treatment of cultured keratinocytes with heat-denatured CRP induced interleukin-8 (IL-8) expression, a potent leukocyte chemotactic cytokine. CRP in the medium (liquid phase) and CRP-coated dishes (solid phase) both inhibited the adhesion of keratinocytes in culture.

CONCLUSION

Accumulation of CRP may regulate the skin inflammation and keratinocyte proliferation by modulating keratinocyte cytokine expression and adhesion to substrate.

24-Week Exposure to Oxidized Tyrosine Induces Hepatic Fibrosis Involving Activation of the MAPK/TGF-β1 Signaling Pathway in Sprague-Dawley Rats Model

SCOPE

Oxidized tyrosine (O-Tyr) has been widely detected in many consumer protein products. O-Tyr products such as dityrosine (Dityr) and 3-nitrotyrosine (3-NT) are universal biomarkers of protein oxidation and have been demonstrated to be associated with metabolic disorders in biological system. Evaluation of potential intracorporal effects of dietary O-Tyr is important since the mechanism of biological impacts induced by oral oxidized protein products (OPPs) is still limited although we have proved that some dietary OPPs would induce oxidative injury to liver and kidney.

METHODS AND RESULTS

The present study aimed to investigate the dose-dependent hepatic injury caused by oral O-Tyr in rats. 24-week feeding of O-Tyr enhanced aspartate aminotransferase (AST) and alanine aminotransferase (ALT) activities, increased total bilirubin (TBiL) content, and led to oxidative damage in rats liver. Besides, O-Tyr distinctly increased the phosphorylation of p38 and ERK2 MAPKs and enhanced fibrosis-related TGF-β1 and Smad2/3 levels. Higher extracellular matrix (ECM) indexes (ICTP, PIIINP) and histological examination (HE and Masson staining) also supported dose-dependent hepatic fibrosis caused by O-Tyr.

CONCLUSION

These findings reveal that O-Tyr may induce oxidative damage and hepatic fibrosis via MAPK/TGF-β1 signaling pathway, in which ROS together with malondialdehyde (MDA) and OPPs act as the pivotal mediators.

High-Sensitivity C-Reactive Protein Is Associated With Incident Type 2 Diabetes Among African Americans: The Jackson Heart Study

OBJECTIVE

Previous studies on the association between hs-CRP and incident type 2 diabetes among African Americans have been inconclusive. We examined the association between hs-CRP and incident diabetes in a large African American cohort (Jackson Heart Study).

RESEARCH DESIGN AND METHODS

hs-CRP was measured in 3,340 participants. Incident diabetes was defined by fasting glucose ≥126 mg/dL, physician diagnosis, use of diabetes drugs, or A1C ≥6.5% (48 mmol/mol) at follow-up. Cox regression was used to estimate hazard ratios (HRs) for incident diabetes, adjusting for age, sex, education, diabetes family history, alcohol, HDL, triglycerides, hypertension status, hypertension medications, physical activity, BMI, HOMA-insulin resistance (HOMAIR), and waist circumference.

RESULTS

Participants (63% women) were aged 53.3 ± 12.5 years. During a median follow-up of 7.5 years, 17.4% developed diabetes (23.1/1,000 person-years, 95% CI 21.3-25.1). After adjustment, the HR (hs-CRP third vs. first tertile) was 1.64 (95% CI 1.26-2.13). In separate models, further adjustment for BMI and waist circumference attenuated this association (HR 1.28 [95% CI 0.97-1.69] and 1.35 [95% CI 1.03-1.78, P < 0.05 for trend], respectively). Upon adding HOMAIR in the models, the association was no longer significant. In adjusted HOMAIR-stratified analysis, the hs-CRP-diabetes association appeared stronger in participants with HOMAIR <3.0 compared with HOMAIR ≥3.0 (P < 0.0001 for interaction). The association was also stronger among nonobese participants, although not significant when adjusted for HOMAIR.

CONCLUSIONS

Low-grade inflammation, as measured by hs-CRP level, may have an important role in the development of diabetes among African Americans with a lesser degree of insulin resistance.

Amide-adducts in atherosclerosis

Too many hypotheses in the etiology of atherosclerosis have been proposed. Classically, lipid insudation hypothesis by Virchow and thrombogenic hypothesis by Rokitansky are famous. However, in the recent progress in the area of atherosclerosis, the response-to-injury hypothesis by Ross (Ross R Glomset JA, N Engl J Med 295:369-377, 420-425, 1976; Ross R, Arteriosclerosis 1:293-311, 1981; Ross R, N Engl J Med 314:488-500, 1986; Ross R, Nature 362:801-809, 1993; Ross R, N Engl J Med 340:115-126, 1999) has been the leading one. In this review, however, the author focuses to the recent debate on the role of oxidative modification of atherogenic lipoproteins.

Suppressive effects of cacao polyphenols on the development of atherosclerosis in apolipoprotein E-deficient mice

Previous studies in humans have shown that the cacao polyphenols, (-)-epicatechin and its oligomers, prevent in vitro and ex vivo low-density lipoprotein oxidation mediated by free radical generators and metal ions and also reduce plasma LDL-cholesterol levels. The aim of this study was to examine the effects of cacao polyphenols on the development of atherosclerosis in apolipoprotein E-deficient (-/-) mice. Mice aged 8 weeks (n = 90) were randomized into three groups, and fed either normal mouse chow (controls) or chow supplemented with 0.25 or 0.40 % cacao polyphenols for 16 weeks. The mean plaque area in cross-sections of the brachiocephalic trunk was measured and found to be lower in the 0.25 % cacao polyphenol group than in the control group (p < 0.05). Pathological observations showed that accumulation of cholesterol crystals in the plaque area was greater in the control group compared with the 0.40 % cacao polyphenol group (p < 0.05). Immunochemical staining in the 0.25 and 0.40 % groups showed that expression of the cell adhesion molecules (VCAM-1 and ICAM-1) and production of oxidative stress markers (4-hydroxynonenal, hexanoyl-lysine, and dityrosine) were reduced in cross-sections of the brachiocephalic trunk. These results suggest that cacao polyphenols inhibit the development of atherosclerosis in apolipoprotein E-deficient (-/-) mice by reducing oxidative stress and inflammatory responses.

Lipid hydroperoxide-derived modification of proteins in gastrointestinal tract

Role of lipid peroxidation in the pathogenesis of gastrointestinal diseases has been evaluated by measuring the tissue levels of lipid peroxides as thiobarbituric acid-reactive substances in the animal models as well as human. Recently, N (ε)-(hexanoyl)lysine (HEL) and 4-hydroxy-2-nonenal (HNE) are recognized as reliable and sensitive biomarkers for the early phase and the late phase of lipid peroxidation, respectively. The presence of HNE- and HEL-modified proteins has been demonstrated in in vivo models of several gastrointestinal diseases. In the present review, we introduced HNE-modification of TRPV1 channel in esophageal epithelial cells, HEL-modification of tropomyosin 1 (TMP1) in gastric cancer cells, and HEL-modification of gastrokine 1 in the healing of gastric ulcer.

Immunochemical detection of lipid hydroperoxide- and aldehyde-modified proteins in diseases

Polyunsaturated fatty acid (PUFA) is easily peroxidized by free radicals and enzymes. When this occurs, it results in the compromised integrity of cellular membranes and leads to lipid hydroperoxide as a major reaction product, which is decomposed into aldehyde. Lipid hydroperoxide-modified lysine is known to be an early product of the lipid peroxidation process, suggesting that it might be a PUFA-oxidative stress marker during the initial stage of oxidative stress. Lipid hydroperoxides cause or enhance ROS-mediated DNA fragmentation. The α,β-unsaturated aldehydes are end products of PUFA peroxidation. They are highly reactive and readily attack and modify the protein amino acid residues into aldehyde-modified proteins. Lipid peroxidation-derived α,β-unsaturated aldehydes are capable of inducing cellular stress-responsive processes such as cell signaling and apoptosis. The lipid hydroperoxide- and aldehyde-modified proteins have been immunohistochemically detected in diverse pathological situations such as atherosclerosis, Alzheimer's disease, Parkinson's disease, and chemical material-induced liver injury and renal tubular injury in humans and experimental animals. These findings suggest that the expression of the lipid hydroperoxide- and aldehyde-modified proteins is closely associated with the pathogenesis of these diseases in humans and experimental animals.

Determination of HEL (Hexanoyl-lysine adduct): a novel biomarker for omega-6 PUFA oxidation

Published evidences indicate that reactive oxygen species (ROS) can induce lipid peroxidation, which plays important role in the pathophysiology of numerous diseases including atherosclerosis, diabetes, cancer and aging process. Monitoring of oxidative modification or oxidative damages of biomolecules may therefore be essential for the understanding of aging, and age-related diseases. N-epsilon-Hexanoyl-lysine (HEL) is a novel lipid peroxidation biomarker which is derived from the oxidation of omega-6 unsaturated fatty acid. In this chapter, development of HEL ELISA and its applications are reported. Assay range of HEL ELISA was 2-700 nmol/L, and showed good linearity and reproducibility. Accuracy of this assay was validated by recovery test and absorption test. HEL concentration in human urine was 22.9 ± 15.4 nmol/L and it was suggested that HEL exists as low molecular substances, in a free or in the peptide-attached form. In contrast with the urine sample, serum HEL was suggested to exist in the protein-attached form, and hydrolysis by protease might be essential for the accurate measurement of HEL in protein containing samples such as serum and cultured cells. By sample pretreatment with proteases, HEL was successfully detected in oxidized LDL, oxidized serum, and rat serum. In conclusion, HEL ELISA can be applied to measure urine, serum, and other biological samples independent of the animal species, and may be useful for the assessment of omega-6 PUFA oxidation in the living bodies.

The formation of lipid hydroperoxide-derived amide-type lysine adducts on proteins: a review of current knowledge

Lipid peroxidation is an important biological reaction. In particular, polyunsaturated fatty acid (PUFA) can be oxidized easily. Peroxidized lipids often react with other amines accompanied by the formation of various covalent adducts. Novel amide-type lipid-lysine adducts have been identified from an in vitro reaction mixture of lipid hydroperoxide with a protein, biological tissues exposed to conditions of oxidative stress and human urine from a healthy person. In this chapter, the current knowledge of amide type adducts is reviewed with a focus on the evaluation of functional foods and diseases with a history of discovery of hexanoyl-lysine (HEL). Although there is extensive research on HEL and other amide-type adducts, the mechanism of generation of the amide bond remains unclear. We have found that the decomposed aldehyde plus peroxide combined with a lysine moiety does not fully explain the formation of the amide-type lipid-lysine adduct that is generated by lipid hydroperoxide. Singlet oxygen or an excited state of the ketone generated from the lipid hydroperoxide may also contribute to the formation of the amide linkage. The amide-adducts may prove useful not only for the detection of oxidative stress induced by disease but also for the estimation of damage caused by an excess intake of PUFA.

C-reactive protein and reactive oxygen metabolites in subjects with metabolic syndrome

OBJECTIVE

This cross-sectional study investigated the correlation between diacron reactive oxygen metabolites (d-ROMs) and high-sensitivity C-reactive protein (hs-CRP) in subjects with or without metabolic syndrome.

METHODS

Cardiometabolic risk factors, d-ROMs and hs-CRP were determined in 457 women: 123 with metabolic syndrome and 334 without metabolic syndrome. The correlation between d-ROMs and hs-CRP levels was compared between the two groups.

RESULTS

The group with metabolic syndrome had significantly higher d-ROMs and hs-CRP levels than the group without metabolic syndrome. While the d-ROMs level was significantly and positively correlated with the hs-CRP level in both groups, the correlation level between the two groups was significantly different. Multiple linear regression analysis adjusted for other cardiometabolic risk factors also showed significant positive correlation between dROMs and hs-CRP levels in both groups.

CONCLUSION

Subjects with metabolic syndrome may have a closer relationship between inflammation and oxidative stress than subjects without metabolic syndrome, possibly reflecting their increased predisposition to atherosclerosis. Further studies are necessary to confirm the observed relationship.

Atherosclerosis-related functions of C-reactive protein

C-reactive protein (CRP) is secreted by hepatocytes as a pentameric molecule made up of identical monomers, circulates in the plasma as pentamers, and localizes in atherosclerotic lesions. In some cases, localized CRP was detected by using monoclonal antibodies that did not react with native pentameric CRP but were specific for isolated monomeric CRP. It has been reported that, once CRP is bound to certain ligands, the pentameric structure of CRP is altered so that it can dissociate into monomers. Accordingly, the monomeric CRP found in atherosclerotic lesions may be a stationary, ligand-bound, by-product of a ligand-binding function of CRP. CRP binds to modified forms of low-density lipoprotein (LDL). The binding of CRP to oxidized LDL requires acidic pH conditions; the binding at physiological pH is controversial. The binding of CRP to enzymatically-modified LDL occurs at physiological pH; however, the binding is enhanced at acidic pH. Using enzymatically-modified LDL, CRP has been shown to prevent the formation of enzymatically-modified LDL-loaded macrophage foam cells. CRP is neither pro-atherogenic nor atheroprotective in ApoE⁻(/)⁻ and ApoB¹⁰⁰(/)¹⁰⁰Ldlr ⁻(/)⁻ murine models of atherosclerosis, except in one study where CRP was found to be slightly atheroprotective in ApoB¹⁰⁰(/)¹⁰⁰Ldlr ⁻(/)⁻ mice. The reasons for the ineffectiveness of human CRP in murine models of atherosclerosis are not defined. It is possible that an inflammatory environment, such as those characterized by acidic pH, is needed for efficient interaction between CRP and atherogenic LDL during the development of atherosclerosis and to observe the possible atheroprotective function of CRP in animal models.

Anti-oxidant effects of kiwi fruit in vitro and in vivo

We previously reported that kiwi fruit is rich in polyphenols and has immunostimulatory activity. Polyphenols are widely known for having anti-oxidant effects. We also revealed potential anti-oxidant effects of kiwi fruit in vivo by oral administration to mice. Here, we compared the anti-oxidant effects of kiwi fruit with those of other fruits in vitro. Then, we examined the inhibitory effects of kiwi fruit on oxidation in the human body. There are two varieties of kiwi fruit, green kiwi and gold kiwi. We also examined variation between these varieties. Comparison of the anti-oxidant effects in vitro demonstrated that kiwi fruit had stronger anti-oxidant effects than orange and grapefruit, which are rich in vitamin C; gold kiwi had the strongest anti-oxidant effects. Kiwi fruit inhibited oxidation of biological substances in the human body. In particular, kiwi fruit may inhibit early lipid oxidation. In this study, kiwi fruit had strong anti-oxidant effects and may prevent the development and deterioration of diseases caused by oxidative stress.

Evaluating periodontal risk for patients at risk of or suffering from atherosclerosis: recent biological hypotheses and therapeutic consequences

Cardiovascular disease, such as atherosclerosis, is the main cause of mortality in developed countries. Most atherosclerosis risk factors have been identified and are treated, improving patient cardiovascular status and reducing mortality, but some remain unknown. Periodontal disease is generally defined as inflammatory disease initiated by accumulation of dental bacterial plaque, leading to the destruction of tissues that support the teeth. Severe forms have a high prevalence (15% of the population) and are associated with the presence of virulent pathogens such as Porphyromonas gingivalis. Epidemiological studies have shown that severe periodontal disease negatively influences cardiovascular status. The aim of this paper was to present a synthesis of the most recent biological data related to the link between periodontal and cardiovascular disease. The potential biological mechanisms involved in these two inflammatory diseases (bacteriological theory, inflammatory theory, immune theory) were developed. According to the observed positive effects of periodontal treatment on systemic conditions, the benefit of a reinforced collaboration between dentists and cardiologists was discussed, especially for patients at risk for cardiovascular disease.

Detection of lipid-lysine amide-type adduct as a marker of PUFA oxidation and its applications

Research into lipid peroxidation-induced protein modification has been ongoing for many years. Recent studies on lipo-oxidation shows the occurrence of another type of protein modification, amide-type adduct formation by lipid hydroperoxide, as well as classical aldehyde-derived protein modifications. The amide-type modifications can be either classified as alkylamide and carboxyalkylamide according to the formed structures. As an alkylamide-type adduct, Nepsilon-(hexanoyl)lysine can be formed by the reaction of peroxidized n-6 fatty acid with lysine. Nepsilon-(propanoyl)lysine is considered to be generated from oxidation of n-3 fatty acid with lysine. The generation pattern of both might be useful for classification of which fatty acids are more involved in oxidation in vivo. Since the alkylamide type-adducts are relatively stable and detectable from biological specimens like urine, these adducts, especially Nepsilon-(hexanoyl)lysine, are used as reliable markers for not only oxidative stress evaluation but also development of functional food.

Association between insulin resistance and c-reactive protein among Peruvian adults

OBJECTIVE

Insulin resistance (IR), a reduced physiological response of peripheral tissues to the action of insulin, is one of the major causes of type 2 diabetes. We sought to evaluate the relationship between serum C-reactive protein (CRP), a marker of systemic inflammation, and prevalence of IR among Peruvian adults.

METHODS

This population based study of 1,525 individuals (569 men and 956 women; mean age 39 years old) was conducted among residents in Lima and Callao, Peru. Fasting plasma glucose, insulin, and CRP concentrations were measured using standard approaches. Insulin resistance was assessed using the homeostasis model (HOMA-IR). Categories of CRP were defined by the following tertiles: <0.81 mg/l, 0.81-2.53 mg/l, and >2.53 mg/l. Logistic regression procedures were employed to estimate odds ratios (OR) and 95% confidence intervals (CI).

RESULTS

Elevated CRP were significantly associated with increased mean fasting insulin and mean HOMA-IR concentrations (p < 0.001). Women with CRP concentration >2.53 mg/l (upper tertile) had a 2.18-fold increased risk of IR (OR = 2.18 95% CI 1.51-3.16) as compared with those in the lowest tertile (<0.81 mg/l). Among men, those in the upper tertile had a 2.54-fold increased risk of IR (OR = 2.54 95% CI 1.54-4.20) as compared with those in the lowest tertile.

CONCLUSION

Our observations among Peruvians suggest that chronic systemic inflammation, as evidenced by elevated CRP, may be of etiologic importance in insulin resistance and diabetes.

Serum C-reactive protein and thioredoxin levels in subjects with mildly reduced glomerular filtration rate

Background

Chronic kidney disease (CKD) is a newly recognized high-risk condition for cardiovascular disease (CVD), and previous studies reported the changes in inflammation and oxidative stress in advanced stages of CKD. We compared the levels of serum biomarkers for inflammation and oxidative stress between subjects with normal and mildly reduced glomerular filtration rate (GFR).

Methods

The subjects were 182 participants of a health check-up program including those with normal (≥ 90 mL/min/1.73 m², N = 79) and mildly reduced eGFR (60-89 mL/min/1.73 m², N = 103) which was calculated based on serum creatinine, age and sex. We excluded those with reduced eGFR < 60 mL/min/1.73 m². No one had proteinuria. We measured serum levels of C-reactive protein (CRP) and thioredoxin (TRX) as the markers of inflammation and oxidative stress, respectively.

Results

As compared with subjects with normal eGFR, those with mildly reduced eGFR had increased levels of both CRP and TRX. Also, eGFR was inversely correlated with these biomarkers. The associations of eGFR with these biomarkers remained significant after adjustment for age and sex. When adjustment was done for eight possible confounders, CRP showed significant association with systolic blood pressure, high density lipoprotein cholesterol (HDL-C) and non-HDL-C, whereas TRX was associated with sex significantly, and with eGFR and systolic blood pressure at borderline significance.

Conclusions

We showed the increased levels of CRP and TRX in subjects with mildly reduced eGFR. The eGFR-CRP link and the eGFR-TRX link appeared to be mediated, at least partly, by the alterations in blood pressure and plasma lipids in these subjects.

AT1 blockade attenuates atherosclerotic plaque destabilization accompanied by the suppression of cathepsin S activity in apoE-deficient mice

Although it has been suggested that the renin-angiotensin (RA) system and cathepsins contribute to the development and vulnerability of atherosclerotic plaque, the interaction of the RA system and cathepsins is unclear. Thus, we investigated the effects of an angiotensin II type 1 receptor (AT1) antagonist, olmesartan, on the levels of cathepsins in brachiocephalic atherosclerotic plaque and plaque stabilization in apolipoprotein E (apoE)-deficient mice receiving a high-fat diet. Under a high fat diet, treatment with olmesartan (3 mg/kg per day) maintained collagen and elastin at high levels and attenuated the plaque development and cathepsin S (Cat S) level in the atherosclerotic plaque of apoE-deficient mice. The administration of olmesartan suppressed the accumulation of macrophages in plaque. Immunoreactivities of Cat S and AT1 were observed in macrophages. The amount of Cat S mRNA and the macrophage-mediated collagenolytic and elastolytic activities in cultured macrophages were increased by exposure to angiotensin II (Ang II), and these effects were diminished by olmesartan and the NADPH-oxidase inhibitor apocynin. These results suggested that Cat S derived from macrophages is involved in the mechanisms of atherosclerotic plaque vulnerability, and AT1 blocker maintained the plaque stabilization alongside the suppression of Cat S and macrophage activities.

Relations between serum reactive oxygen metabolites (ROMs) and various inflammatory and metabolic parameters in a Japanese population

AIM

Both oxidative stress and inflammation are known to play roles in the pathogenesis of cardiovascular disease. We investigated the relations between reactive oxygen metabolites (ROMs) and various inflammatory and metabolic parameters in a Japanese population.

METHODS

We analyzed 48 male and 69 female subjects, aged 25 to 65 years, who underwent an annual health checkup in our university. Serum ROM level was assayed using a free radical elective evaluator. We also measured serum concentrations of high-sensitivity C-reactive protein (hsCRP), insulin, and high molecular weight (HMW) adiponectin.

RESULTS

Although the serum ROM level in females (347+/-83 Carr U) was slightly higher than in males (333+/-53 Carr U), this was not statistically significant. In the 48 male subjects, the ROM level negatively correlated with age (r=-0.344, p=0.0161), and positively correlated with the hsCRP level (r=0.306, p=0.0338). In the 69 female subjects, the ROM level negatively correlated with serum creatinine (r=-0.293, p=0.0141), and positively correlated with insulin (r=0.278, p=0.0202), the insulin resistance index (r=0.286, p=0.0170) and hsCRP levels (r=0.487, p<0.0001). Stepwise multiple regression analysis revealed that serum hsCRP, creatinine, and age were independently correlated with the serum ROMs level (R2=0.365; F value highest for hsCRP). When the study subjects were divided into tertiles according to the ROM level, serum hsCRP was significantly different among the three groups: its level was highest in the highest tertile of ROMs (p<0.001).

CONCLUSION

These results suggest that the serum ROM level is closely associated with serum hsCRP in Japanese adult subjects.

High-sensitivity CRP reflects insulin resistance in smokers

AIM

The elevation of high-sensitivity C-reactive protein (hs-CRP) is a strong risk factor for cardio-vascular disease (CVD) and is associated with insulin resistance. The hs-CRP concentration also increases in smokers known to be at a high risk for CVD. We examined whether hs-CRP concentra-tion reflects insulin resistance in smokers.

METHODS

The hs-CRP levels were measured in 121 male subjects (54 nonsmokers and 67 smokers) with a normal glucose tolerance. The hs-CRP concentration was compared to the homeostasis model assessment of insulin resistance (HOMA-IR) and other clinical variables related to insulin resistance.

RESULTS

Smokers had a 64.5% higher hs-CRP concentration than nonsmokers (p<0.0001). In both nonsmokers and smokers, hs-CRP positively correlated with HOMA-IR (r=0.301, p<0.05 and r=0.312, p<0.01) and fasting insulin (r=0.281, p<0.05 and r=0.356, p<0.01). The correlation between hs-CRP and HOMA-IR or fasting insulin was stronger in smokers than in nonsmokers. In smokers, hs-CRP significantly correlated with BMI and HDL-cholesterol (r=0.386, p<0.01 and r=-0.307, p<0.05). Stepwise regression analysis revealed that BMI and HOMA-IR were significant predictors of hs-CRP in smokers (r=0.423, p<0.01).

CONCLUSIONS

The hs-CRP concentration reflects insulin resistance in smokers. It would be preferable to consider insulin resistance in evaluating hs-CRP concentrations, even in smokers.

Detection of a lipid-lysine adduct family with an amide bond as the linkage: novel markers for lipid-derived protein modifications

An amide-type adduct, hexanoyl-lysine (HEL) is generated from the reaction between n-6 fatty acid (FA)-derived lipid peroxide and lysine. Immunochemical and chemical methods can be used to detect the formation of HEL. For example, an ELISA kit using the monoclonal antibody to HEL is now commercially available. We recently identified propanoyl-lysine (propionyl-lysine, PRL) from the reaction of an n-3 FA and a lysine residue. The antibody to PRL has been prepared and characterized. Using these monoclonal antibodies, the localization of adducts in tissues has been confirmed. Moreover, both amide-type adducts, HEL and PRL, can be simultaneously measured using liquid chromatography mass spectrometry (LC/MS/MS) with isotope dilution methods. The LC/MS/MS analysis reveals the rigid amounts of the adducts in human urine. Both the chemical and immunochemical methods are useful for the estimation of amide-type adducts in vivo.