Oxidative stress in the cardiorenal metabolic syndrome

Cardiovascular-Kidney-Metabolic (CKM) syndrome: A state-of-the-art review

The correlation between obesity, type 2 diabetes mellitus (DM), cardiovascular disease (CVD), and chronic kidney disease (CKD) is an escalating and widely acknowledged epidemic in industrialized nations. Recently, this complex web of interrelated health conditions has been collectively defined as the Cardiovascular-Kidney-Metabolic (CKM) syndrome by the American Heart Association (AHA). The molecular mechanisms underlying CKM disease contain a spectrum of interconnected factors, including hyperglycemia, insulin resistance, heightened activity of the renin-angiotensin-aldosterone system (RAAS), the generation of advanced glycation end-products, oxidative stress, lipotoxicity, endoplasmic reticulum stress, abnormalities in calcium handling, malfunctioning of mitochondria and impaired energy production, as well as persistent chronic inflammation. Addressing their prevention, management, and treatment is of paramount importance to promote better patient health outcomes. The objective of this review is to provide a comprehensive and critical examination of the current state-of-the-art regarding the recently defined CKM syndrome. This includes an exploration of epidemiological evidence establishing connections between cardio-renal-metabolic diseases, an examination of the underlying pathophysiological mechanisms, and a comprehensive overview of existing treatment modalities.

Endothelial Dysfunction in Obesity and Therapeutic Targets

Parallel to the increasing prevalence of obesity in the world, the mortality from cardiovascular disease has also increased. Low-grade chronic inflammation in obesity disrupts vascular homeostasis, and the dysregulation of adipocyte-derived endocrine and paracrine effects contributes to endothelial dysfunction. Besides the adipose tissue inflammation, decreased nitric oxide (NO)-bioavailability, insulin resistance (IR), and oxidized low-density lipoproteins (oxLDLs) are the main factors contributing to endothelial dysfunction in obesity and the development of cardiorenal metabolic syndrome. While normal healthy perivascular adipose tissue (PVAT) ensures the dilation of blood vessels, obesity-associated PVAT leads to a change in the profile of the released adipo-cytokines, resulting in a decreased vasorelaxing effect. Higher stiffness parameter β, increased oxidative stress, upregulation of pro-inflammatory cytokines, and nicotinamide adenine dinucleotide phosphate (NADP) oxidase in PVAT turn the macrophages into pro-atherogenic phenotypes by oxLDL-induced adipocyte-derived exosome-macrophage crosstalk and contribute to the endothelial dysfunction. In clinical practice, carotid ultrasound, higher leptin levels correlate with irisin over-secretion by human visceral and subcutaneous adipose tissues, and remnant cholesterol (RC) levels predict atherosclerotic disease in obesity. As a novel therapeutic strategy for cardiovascular protection, liraglutide improves vascular dysfunction by modulating a cyclic adenosine monophosphate (cAMP)-independent protein kinase A (PKA)-AMP-activated protein kinase (AMPK) pathway in PVAT in obese individuals. Because the renin-angiotensin-aldosterone system (RAAS) activity, hyperinsulinemia, and the resultant IR play key roles in the progression of cardiovascular disease in obesity, RAAS-targeted therapies contribute to improving endothelial dysfunction. By contrast, arginase reciprocally inhibits NO formation and promotes oxidative stress. Thus, targeting arginase activity as a key mediator in endothelial dysfunction has therapeutic potential in obesity-related vascular comorbidities. Obesity-related endothelial dysfunction plays a pivotal role in the progression of type 2 diabetes (T2D). The peroxisome proliferator-activated receptor gamma (PPARγ) agonist, rosiglitazone (thiazolidinedione), is a popular drug for treating diabetes; however, it leads to increased cardiovascular risk. Selective sodium-glucose co-transporter-2 (SGLT-2) inhibitor empagliflozin (EMPA) significantly improves endothelial dysfunction and mortality occurring through redox-dependent mechanisms. Although endothelial dysfunction and oxidative stress are alleviated by either metformin or EMPA, currently used drugs to treat obesity-related diabetes neither possess the same anti-inflammatory potential nor simultaneously target endothelial cell dysfunction and obesity equally. While therapeutic interventions with glucagon-like peptide-1 (GLP-1) receptor agonist liraglutide or bariatric surgery reverse regenerative cell exhaustion, support vascular repair mechanisms, and improve cardiometabolic risk in individuals with T2D and obesity, the GLP-1 analog exendin-4 attenuates endothelial endoplasmic reticulum stress.

Bergamot leaf extract treats cardiorenal metabolic syndrome and associated pathophysiological factors in rats fed with a high sugar fat diet

Bergamot citrus (Citrus bergamia Risso et Poiteau), have been used as a strategy to prevent or treat comorbidities associated with metabolic syndrome parameters, such as cardiorenal metabolic syndrome (CRMS). The aim was to test the effect of bergamot leaf extract on CRMS and associated pathophysiological factors in rats fed with a high sugar-fat diet. Animals were divided into two experimental groups with control diet (Control, n = 30) and high sugar-fat diet (HSF, n = 30) for 20 weeks. Once CRMS was detected, animals were redivided to begin the treatment with Bergamot Leaf Extract (BLE) by gavage (50 mg/kg) for 10 weeks: control diet + placebo (Control, n = 09), control diet + BLE (Control + BLE, n = 09), HSF diet + placebo (HSF, n = 09), HSF + BLE (n = 09). Evaluation included nutritional, metabolic and hormonal analysis; and renal and cardiac parameters. HSF groups presented obesity, dyslipidemia, hypertension, hyperglycemia, hyperinsulinemia, insulin resistance. BLE showed protection against effects on hypertriglyceridemia, insulin resistance, renal damage, and structural and functional alterations of the heart. Conclusion: Bergamot leaf extract shows potential as a therapeutic to treat CRMS in animals fed with a high sugar-fat diet.

Incorporation of Oxidized Phenylalanine Derivatives into Insulin Signaling Relevant Proteins May Link Oxidative Stress to Signaling Conditions Underlying Chronic Insulin Resistance

A link between oxidative stress and insulin resistance has been suggested. Hydroxyl free radicals are known to be able to convert phenylalanine (Phe) into the non-physiological tyrosine isoforms ortho- and meta-tyrosine (o-Tyr, m-Tyr). The aim of our study was to examine the role of o-Tyr and m-Tyr in the development of insulin resistance. We found that insulin-induced uptake of glucose was blunted in cultures of 3T3-L1 grown on media containing o- or m-Tyr. We show that these modified amino acids are incorporated into cellular proteins. We focused on insulin receptor substrate 1 (IRS-1), which plays a role in insulin signaling. The activating phosphorylation of IRS-1 was increased by insulin, the effect of which was abolished in cells grown in m-Tyr or o-Tyr media. We found that phosphorylation of m- or o-Tyr containing IRS-1 segments by insulin receptor (IR) kinase was greatly reduced, PTP-1B phosphatase was incapable of dephosphorylating phosphorylated m- or o-Tyr IRS-1 peptides, and the SH2 domains of phosphoinositide 3-kinase (PI3K) bound the o-Tyr IRS-1 peptides with greatly reduced affinity. According to our data, m- or o-Tyr incorporation into IRS-1 modifies its protein–protein interactions with regulating enzymes and effectors, thus IRS-1 eventually loses its capacity to play its role in insulin signaling, leading to insulin resistance.

Advanced glycation end products and oxidative stress as a basis for metabolic abnormalities in patients with type 1 diabetes after successful simultaneous pancreas-kidney transplantation

Aim. To compare advanced glycation end-products (AGE, RAGE) and 3-nitrotyrosine (3-HT) in patients with DM 1 after successful simultaneous pancreas-kidney transplantation (SPK) and kidney transplantation alone (KTA). To assess relationship between levels of AGE, RAGE, 3-HT and renal transplant (RT) function, carbohydrate and mineral metabolism. Materials and methods. The study included 58 patients who received kidney transplantation in end-stage renal disease (ESRD). 36 patients received SPK. There were performed routine laboratory, examination of AGE, RAGE, 3-NT, parathyroid hormone (PTH), 25(OH)vitamin D, calcium, phosphorus, FGF23, osteoprotegerin (OPG), and fetuin-A levels. Results. All patients after SPK reached normoglycemia (HbA1c 5.7 [5.3; 6.1] %; C-peptide 3.24 [2.29; 4.40] ng/ml) with the achievement of significant difference vs patients after KTA. Arterial hypertension (AH) was more frequent in recipients of SPK before transplantation than after (p=0.008). AH also persisted in greater number of cases in patients after KTA than after SPK. Patients after SPK had higher AGE (р=0.0003) and lower RAGE (р=0.000003) levels. OPG in patients after SPK was significantly higher (р=0.04). The correlation analysis revealed significant positive correlation between 3-HT and OPG (p0.05; r=0.30), RAGE and eGFR (r=-0.52), HbA1c (r=0.48), duration of AH (r=0.34), AGE with HbA1c (r=0.51). Conclusion. The results of the "metabolic memory" markers analysis may indicate their contribution to the persistence of the metabolic consequences of CKD and DM 1 after achievement of normoglycemia and renal function restoration and their possible participation in development of recurrent nephropathy, vascular calcification, and bone disorders.

Myo-inositol oxygenase accentuates renal tubular injury initiated by endoplasmic reticulum stress

Besides oxidant stress, endoplasmic reticulum (ER) stress has been implicated in the pathogenesis of various metabolic disorders affecting the kidney. These two forms of stresses are not mutually exclusive to each other and may operate by a feedback loop in worsening the cellular injury. To attest to this contention, studies were performed to assess whether in such a setting, there is worsening of tubulointerstitial injury. We employed tunicamycin as a model of ER stress and used tubular cells and mice overexpressing myo-inositol oxygenase (MIOX), an enzyme involved in glycolytic events with excessive generation of ROS. Concomitant treatment of tunicamycin and transfection of cells with MIOX-pcDNA led to a marked generation of ROS, which was reduced by MIOX-siRNA. Likewise, an accentuated expression of ER stress sensors, GRP78, XBP1, and CHOP, was observed, which was reduced with MIOX-siRNA. These sensors were markedly elevated in MIOX-TG mice compared with WT treated with tunicamycin. This was accompanied with marked deterioration of tubular morphology, along with impairment of renal functions. Interestingly, minimal damage and elevation of ER stressors was observed in MIOX-KO mice. Downstream events that were more adversely affected in MIOX-TG mice included accentuated expression of proapoptogenic proteins, proinflammatory cytokines, and extracellular matrix constituents, although expression of these molecules was unaffected in MIOX-KO mice. Also, their tunicamycin-induced accentuated expression in tubular cells was notably reduced with MIOX-siRNA. These studies suggest that the biology of MIOX-induced oxidant stress and tunicamycin-induced ER stress are interlinked, and both of the events may feed into each other to amplify the tubulointerstitial injury.

Angiotensin II Signal Transduction: An Update on Mechanisms of Physiology and Pathophysiology

The renin-angiotensin-aldosterone system plays crucial roles in cardiovascular physiology and pathophysiology. However, many of the signaling mechanisms have been unclear. The angiotensin II (ANG II) type 1 receptor (AT₁R) is believed to mediate most functions of ANG II in the system. AT₁R utilizes various signal transduction cascades causing hypertension, cardiovascular remodeling, and end organ damage. Moreover, functional cross-talk between AT₁R signaling pathways and other signaling pathways have been recognized. Accumulating evidence reveals the complexity of ANG II signal transduction in pathophysiology of the vasculature, heart, kidney, and brain, as well as several pathophysiological features, including inflammation, metabolic dysfunction, and aging. In this review, we provide a comprehensive update of the ANG II receptor signaling events and their functional significances for potential translation into therapeutic strategies. AT₁R remains central to the system in mediating physiological and pathophysiological functions of ANG II, and participation of specific signaling pathways becomes much clearer. There are still certain limitations and many controversies, and several noteworthy new concepts require further support. However, it is expected that rigorous translational research of the ANG II signaling pathways including those in large animals and humans will contribute to establishing effective new therapies against various diseases.

Protective effect of C-peptide on experimentally induced diabetic nephropathy and the possible link between C-peptide and nitric oxide

Diabetic nephropathy one of the major microvascular diabetic complications. Besides hyperglycemia, other factors contribute to the development of diabetic complications as the proinsulin connecting peptide, C-peptide. We described the role of C-peptide replacement therapy on experimentally induced diabetic nephropathy, and its potential mechanisms of action by studying the role of nitric oxide (NO) as a mediator of C-peptide effects by in vivo modulating its production by NG-nitro-l-arginine methyl ester (L-NAME). Renal injury markers measured were serum urea, creatinine, tumor necrosis factor alpha, and angiotensin II, and malondialdehyde, total antioxidant, Bcl-2, and NO in renal tissue. In conclusion, diabetic induction resulted in islet degenerations and decreased insulin secretion with its metabolic consequences and subsequent renal complications. C-Peptide deficiencies in diabetes might have contributed to the metabolic and renal error, since C-peptide treatment to the diabetic rats completely corrected these errors. The beneficial effects of C-peptide are partially antagonized by L-NAME coadministration, indicating that NO partially mediates C-peptide effects.

Effect of eplerenone in patients with heart failure and reduced ejection fraction: potential effect modification by abdominal obesity. Insight from the EMPHASIS-HF trial

AIMS

An excessive production of aldosterone influences outcome in patients with heart failure (HF) and in obese patients. Findings from laboratory studies suggest that chronic aldosterone blockade maybe more beneficial in abdominally obese HF-prone rats. In the current study, we investigated if the clinical response to a mineralocorticoid receptor antagonist in mildly symptomatic HF patients varied by abdominal obesity.

METHODS AND RESULTS

A total of 2587 NYHA class II, reduced ejection fraction HF (HFrEF) patients enrolled in the EMPHASIS-HF trial were randomly assigned to eplerenone and placebo. In this post hoc analysis, patients were categorized according to waist circumference (WC) (normal if WC < 102 cm in men and < 88 cm in women; abdominal obesity if WC ≥ 102 cm in men and ≥ 88 cm women). The potential statistical interaction between the treatment and WC was assessed on the primary endpoint of death from cardiovascular causes or hospitalization for HF and other secondary endpoints. Over a median follow-up of 21 months, a significant benefit of eplerenone for the primary outcome was noted in both normal [hazard ratio (HR) 0.77, 95% confidence interval (CI) 0.61-0.98, P = 0.03] and increased (HR 0.48, 95% CI 0.37-0.63, P < 0.0001) WC subgroups, but the latter patients appeared to receive greater benefit than patients with normal WC (P for interaction = 0.01). This suggests a significant quantitative (treatment effect varies in magnitude by subgroup, but is always in same direction) rather than a qualitative interaction (direction of the treatment effect varies by subgroup) between eplerenone and WC in the adjusted analysis. Mean doses of eplerenone, blood pressure and serum potassium changes and adverse events were similar between WC subgroups.

CONCLUSION

In EMPHASIS-HF, eplerenone improved outcomes in HFrEF patients with and without abdominal obesity, although the benefit appeared to be more pronounced among those with abdominal obesity. The findings are potentially hypothesis generating and need to be replicated in other HFrEF populations.

Biochemical effects of oleuropein in gentamicin-induced nephrotoxicity in rats

BACKGROUND

Oleuropein is a natural antioxidant and scavenging free radicals. In the present study, we examined effect of oleuropein on the paraoxonase 1 (PON1) activity, lipid peroxidation, lipid profile, atherogenic indexes, and relationship of PON1 activity by high-density lipoprotein-cholesterol (HDL-C) and atherogenic indices in gentamicin (GM)-induced nephrotoxicity in rats.

METHODS

This is a lab trial study in Khorramabad, Lorestan province of Iran (2013). 30 Sprague-Dawley rats were divided into three groups to receive saline; GM, 100 mg/kg/day; and GM plus oleuropein by 15 mg/kg intraperitoneal daily, respectively. After 12 days, animals were anesthetized, blood samples were also collected before killing to measure the levels of triglyceride (TG), total cholesterol (TC), low-density lipoprotein (LDL), and very LDL (VLDL), HDL-C, atherogenic index, lipid peroxidation, and the activities of PON1 of all groups were analyzed. Data were analyzed, and P < 0.050 was considered significant.

RESULTS

Oleuropein significantly decreased lipid peroxidation, TG, TC, LDL, VLDL, atherogenic index, atherogenic coefficient (AC), and cardiac risk ratio (CRR). HDL-C level was significantly increased when treated with oleuropein. The activity of PON1 in treated animals was (62.64 ± 8.68) that it was significantly higher than untreated animals (47.06 ± 4.10) (P = 0.047). The activity of PON1 in the untreated nephrotoxic rats was significantly lower than that of control animals (77.84 ± 9.43) (P = 0.030). Furthermore, the activity of PON1 correlated positively with HDL-C and negatively with AC, CRR 1, and CRR 2 in the treated group with oleuropein.

CONCLUSION

This study showed that oleuropein improves PON1 activity, lipid profile, and atherogenic index and can probably decrease the risk of cardiovascular death in nephrotoxic patients.

NADPH Oxidase/ROS-Dependent VCAM-1 Induction on TNF-α-Challenged Human Cardiac Fibroblasts Enhances Monocyte Adhesion

The inflammation-dependent adhesion molecule expressions are characterized in cardiovascular diseases and myocardial tissue infiltrations. Several pro-inflammatory cytokines are elevated in the acute myocardial injury and infarction. Tumor necrosis factor-α (TNF-α), a pro-inflammatory cytokine, is raised in the injury tissues and inflammatory regions and involved in the pathogenesis of cardiac injury, inflammation, and apoptosis. In fibroblasts, TNF-α-triggered expression of vascular cell adhesion molecule (VCAM)-1 aggravated the heart inflammation. However, the mechanisms underlying TNF-α-mediated VCAM-1 expression in cardiac fibroblasts remain unclear. Here, the primary cultured human cardiac fibroblasts (HCFs) were used to investigate the effects of TNF-α on VCAM-1 expression. The molecular evidence, including protein, mRNA, and promoter analyses, indicated that TNF-α-induced VCAM-1 gene expression is mediated through the TNFR-dependent manner. Activation of TNF-α/TNFR system triggered PKCα-dependent NADPH oxidase (Nox)/reactive oxygen species (ROS) signal linking to MAPK cascades, and then led to activation of the transcription factor, AP-1. Moreover, the results of mRNA and promoter assay demonstrated that c-Jun/AP-1 phosphorylated by TNF-α turns on VCAM-1 gene expression. Subsequently, up-regulated VCAM-1 on the cell surface of TNF-α-challenged HCFs increased the number of monocytes adhering to these cells. These results indicated that in HCFs, activation of AP-1 by PKCα-dependent Nox/ROS/MAPKs cascades is required for TNF-α-induced VCAM-1 expression. To clarify the mechanisms of TNF-α-induced VCAM-1 expression in HCFs may provide therapeutic strategies for heart injury and inflammatory diseases.

Reduction of a marker of oxidative stress with enhancement of iron utilization by erythropoiesis activation following epoetin beta pegol administration in iron-loaded db/db mice

Iron, an essential element for various biological processes, can induce oxidative stress. We hypothesized that iron utilization for erythropoiesis, stimulated by epoetin beta pegol (C.E.R.A.), a long-acting erythropoiesis-stimulating agent, contributes to the reduction of iron-induced oxidative stress. We first investigated the sensitivity of several biomarkers to detect oxidative stress in mice by altering the amount of total body iron; we then investigated whether C.E.R.A. ameliorated oxidative stress through enhanced iron utilization. We treated db/db mice with intravenous iron-dextran and evaluated several biomarkers of iron-induced oxidative stress. In mice loaded with 5 mg/head iron, hepatic iron content was elevated and the oxidative stress marker d-ROMs (serum derivatives of reactive oxygen metabolites) was increased, whereas urinary 8-hydroxy-2'-deoxyguanosine and serum malondialdehyde were not, indicating that d-ROMs is a sensitive marker of iron-induced oxidative stress. To investigate whether C.E.R.A. ameliorated oxidative stress, db/db mice were intravenously administered iron-dextran or dextran only, followed by C.E.R.A. Hemoglobin level increased, while hepatic iron content decreased after C.E.R.A.

TREATMENT

Serum d-ROMs decreased after C.E.R.A. treatment in the iron-dextran-treated group. Our results suggest that C.E.R.A. promotes iron utilization for erythropoiesis through mobilization of hepatic iron storage, leading to a decrease in serum oxidative stress markers in iron-loaded db/db mice.

Reactive oxygen species, nutrition, hypoxia and diseases: Problems solved?

Within the last twenty years the view on reactive oxygen species (ROS) has changed; they are no longer only considered to be harmful but also necessary for cellular communication and homeostasis in different organisms ranging from bacteria to mammals. In the latter, ROS were shown to modulate diverse physiological processes including the regulation of growth factor signaling, the hypoxic response, inflammation and the immune response. During the last 60–100 years the life style, at least in the Western world, has changed enormously. This became obvious with an increase in caloric intake, decreased energy expenditure as well as the appearance of alcoholism and smoking; These changes were shown to contribute to generation of ROS which are, at least in part, associated with the occurrence of several chronic diseases like adiposity, atherosclerosis, type II diabetes, and cancer. In this review we discuss aspects and problems on the role of intracellular ROS formation and nutrition with the link to diseases and their problematic therapeutical issues.

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Oxidative stress is linked to overnutrition, obesity and associated diseases or cancer.

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Reactive oxygen species (ROS) are crucially involved in modulation of signaling cascades.

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NOX proteins and hypoxia contribute to formation of ROS under different nutrient regimes.

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ROS are powerful post-transcriptional and epigenetic regulators.

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Treatment of obesity with antioxidants requires more, larger, and better monitored clinical trials.

Apocynin Attenuates Cardiac Injury in Type 4 Cardiorenal Syndrome via Suppressing Cardiac Fibroblast Growth Factor-2 With Oxidative Stress Inhibition

Background

Type 4 cardiorenal syndrome (CRS) refers to the cardiac injury induced by chronic kidney disease. We aimed to assess oxidative stress and cardiac injury in patients with type 4 CRS, determine whether the antioxidant apocynin attenuated cardiac injury in rats with type 4 CRS, and explore potential mechanisms.

Methods and Results

A cross-sectional study was conducted among patients with type 4 CRS (n=17) and controls (n=16). Compared with controls, patients with type 4 CRS showed elevated oxidative stress, which was significantly correlated with cardiac hypertrophy and decreased ejection fraction. In vivo study, male Sprague-Dawley rats underwent 5/6 subtotal nephrectomy and sham surgery, followed with apocynin or vehicle treatment for 8 weeks. Eight weeks after surgery, the 5/6 subtotal nephrectomy rats mimicked type 4 CRS, showing increased serum creatinine, cardiac hypertrophy and fibrosis, and decreased ejection fraction compared with sham-operated animals. Cardiac malondialdehyde, NADPH oxidase activity, fibroblast growth factor-2, and extracellular signal-regulated kinase 1/2 (ERK1/2) phosphorylation increased significantly in the 5/6 subtotal nephrectomy rats. These changes were significantly attenuated by apocynin. In vitro study showed that apocynin reduced angiotensin II–induced NADPH oxidase–dependent oxidative stress, upregulation of fibroblast growth factor-2 and fibrosis biomarkers, and ERK1/2 phosphorylation in cardiac fibroblasts. Importantly, the ERK1/2 inhibitor U0126 reduced the upregulation of fibroblast growth factor-2 and fibrosis biomarkers in angiotensin II–treated fibroblasts.

Conclusions

Oxidative stress is a candidate mediator for type 4 CRS. Apocynin attenuated cardiac injury in type 4 CRS rats via inhibiting NADPH oxidase–dependent oxidative stress-activated ERK1/2 pathway and subsequent fibroblast growth factor-2 upregulation. Our study added evidence to the beneficial effect of apocynin in type 4 CRS.

Crosstalk between adipose tissue and blood vessels in cardiometabolic syndrome: implication of steroid hormone receptors (MR/GR)

Crosstalk between adipose tissue and blood vessels is vital to vascular homeostasis and is disturbed in cardiovascular and metabolic diseases such as hypertension, diabetes and obesity. Cardiometabolic syndrome (CMS) refers to the clustering of obesity-related metabolic disorders such as insulin resistance, glucose and lipid profile alterations, hypertension and cardiovascular diseases. Mechanisms underlying these associations remain unclear. Adipose tissue associated with the vasculature [known as perivascular adipose tissue (PVAT)] has been shown to produce myriads of adipose tissue-derived substances called adipokines, including hormones, cytokines and reactive oxygen species (ROS), which actively participate in the regulation of vascular function and local inflammation by endocrine and/or paracrine mechanisms. As a result, the signaling from PVAT to the vasculature is emerging as a potential therapeutic target for obesity and diabetes-related vascular dysfunction. Accumulating evidence supports a shift in our understanding of the crucial role of elevated plasma levels of aldosterone in obesity, promoting insulin resistance and hypertension. In obesity, aldosterone/mineralocorticoid receptor (MR) signaling induces an abnormal secretion of adipokines, ROS production and systemic inflammation, which in turn contribute to impaired insulin signaling, reduced endothelial-mediated vasorelaxation, and associated cardiovascular abnormalities. Thus, aldosterone excess exerts detrimental metabolic and vascular effects that participate to the development of the CMS and its associated cardiovascular abnormalities. In this review, we focus on the physiopathological roles of corticosteroid receptors in the interplay between PVAT and the vasculature, which underlies their potential as key regulators of vascular function.

Biomarkers of Renal Disease and Progression in Patients with Diabetes

Diabetes prevalence is increasing worldwide, mainly due to the increase in type 2 diabetes. Diabetic nephropathy occurs in up to 40% of people with type 1 or type 2 diabetes. It is important to identify patients at risk of diabetic nephropathy and those who will progress to end stage renal disease. In clinical practice, most commonly used markers of renal disease and progression are serum creatinine, estimated glomerular filtration rate and proteinuria or albuminuria. Unfortunately, they are all insensitive. This review summarizes the evidence regarding the prognostic value and benefits of targeting some novel risk markers for development of diabetic nephropathy and its progression. It is focused mainly on tubular biomarkers (neutrophil-gelatinase associated lipocalin, kidney injury molecule 1, liver-fatty acid-binding protein, N-acetyl-beta-d-glucosaminidase), markers of inflammation (pro-inflammatory cytokines, tumour necrosis factor-α and tumour necrosis factor-α receptors, adhesion molecules, chemokines) and markers of oxidative stress. Despite the promise of some of these new biomarkers, further large, multicenter prospective studies are still needed before they can be used in everyday clinical practice.

Obesity and insulin resistance in resistant hypertension: implications for the kidney

There is recognition that the obesity epidemic contributes substantially to the increasing incidence of CKD and resistant hypertension (HTN). The mechanisms by which obesity promotes resistance are an area of active interest and intense investigation. It is thought that increases in visceral adiposity lead to a proinflammatory, pro-oxidative milieu that promote resistance to the metabolic actions of insulin. This resistance to insulin at the level of skeletal muscle tissue impairs glucose disposal/utilization through actions on the endothelium that include vascular rarefaction, reductions in vascular relaxation, and vascular remodeling. Insulin resistance derived from increased adipose tissue and obesity has system-wide implications for other tissue beds such as the kidney that affects blood pressure regulation. The additional autocrine and paracrine activities of adipose tissue contribute to inappropriate activation of the renin-angiotensin-aldosterone system and the sympathetic nervous system that promote kidney microvascular remodeling, stiffness, and sodium (Na(+)) retention that in turn promote HTN and in the CKD patient, resistance. In this review, we will summarize the important mechanisms that link obesity to CKD as they relate to resistant HTN.

Nox and renal disease

Since the first demonstration of Nox enzyme expression in the kidney in the early 1990s and the subsequent identification of Nox4, or RENOX, a decade later, it has become apparent that the Nox family of reactive oxygen species (ROS) generating enzymes plays an integral role in the normal physiological function of the kidney. As our knowledge of Nox expression patterns and functions in various structures and specialized cell types within the kidney grows, so does the realization that Nox-derived oxidative stress contributes significantly to a wide variety of renal pathologies through their ability to modify lipids and proteins, damage DNA and activate transcriptional programmes. Diverse studies demonstrate key roles for Nox-derived ROS in kidney fibrosis, particularly in settings of chronic renal disease such as diabetic nephropathy. As the most abundant Nox family member in the kidney, much emphasis has been placed on the role of Nox4 in this setting. However, an ever growing body of work continues to uncover key roles for other Nox family members, not only in diabetic kidney disease, but in a diverse array of renal pathological conditions. The objective of the present review is to highlight the latest novel developments in renal Nox biology with an emphasis not only on diabetic nephropathy but many of the other renal disease contexts where oxidative stress is implicated.

Association of high-sensitivity cardiac troponin T and natriuretic peptide with incident ESRD: the Atherosclerosis Risk in Communities (ARIC) study

BACKGROUND

Epidemiologic data for cardiac abnormality predating decreased kidney function are sparse. We investigated the associations of high-sensitivity cardiac troponin T (hs-cTnT) and N-terminal pro-brain natriuretic peptide (NT-proBNP) with end-stage renal disease (ESRD) risk in a community-based cohort.

STUDY DESIGN

A prospective cohort study.

SETTING & PARTICIPANTS

10,749 white and black participants at the fourth visit (1996-1998) of the Atherosclerosis Risk in Communities (ARIC) Study with follow-up through 2010.

PREDICTOR

hs-cTnT (3, 6, 9, and 14ng/L) and NT-proBNP (41.6, 81.0, 142.5, and 272.5pg/mL) levels were divided into 5 categories at the same percentiles (32th, 57th, 77th, and 91th; corresponding to ordinary thresholds of hs-cTnT), with the lowest category as a reference.

OUTCOMES

Incident ESRD defined as initiation of dialysis therapy, transplantation, or death due to kidney disease.

MEASUREMENTS

Relative risk and risk prediction of ESRD according to hs-cTnT and NT-proBNP levels based on Cox proportional hazards models.

RESULTS

During a median follow-up of 13.1 years, 235 participants developed ESRD (1.8 cases/1,000 person-years). hs-cTnT and NT-proBNP levels were associated with ESRD risk independently of each other and of potential confounders, including kidney function and albuminuria (adjusted HRs for highest category, 4.43 [95% CI, 2.43-8.09] and 2.28 [95% CI, 1.44-3.60], respectively). For hs-cTnT level, the association was significant even at the third category (HR for 6-8ng/L of hs-cTnT, 2.74 [95% CI, 1.54-4.88]). Their associations were largely consistent even among persons without decreased kidney function or history of cardiovascular disease. hs-cTnT and NT-proBNP levels both significantly improved ESRD prediction (C statistic differences of 0.0084 [95% CI, 0.0005-0.0164] and 0.0045 [95% CI, 0.0004-0.0087], respectively, from 0.884 with conventional risk factors).

LIMITATIONS

Relatively small number of ESRD cases and single measurement of hs-cTnT and NT-proBNP.

CONCLUSIONS

hs-cTnT and NT-proBNP levels independently predicted ESRD risk in the general population, with more evident results for hs-cTnT. These results suggest the involvement of cardiac abnormality, particularly cardiac injury, in the progression of reduced kidney function and/or may reflect the useful property of hs-cTnT as an end-organ damage marker.

Losartan reduces oxidative damage to renal DNA and conserves plasma antioxidant capacity in diabetic rats

Increased reactive oxygen species (ROS) levels produced by hyperglycemia and angiotensin-II (AT-II) are considered among the pathogenic factors in the malignant transformation of diabetic renal cells. We aimed to investigate the potential role of AT-II in the increased cancer risk seen in diabetes; measuring oxidative damage to renal DNA and protective antioxidant defenses, including adiponectin (Adp) and plasma antioxidant capacity by the Ferric Reducing Ability of Plasma (FRAP) method. In the kidney of streptozotocin (STZ)-induced (55 mg/kg) diabetic rats either treated or not treated for 3 weeks with losartan, an AT-II type 1 receptor antagonist (20 mg/kg/day); we measured 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodGuo) levels, as an index of oxidative DNA damage, circulating Adp and FRAP. Diabetic rats showed significantly higher 8-oxodGuo levels in renal DNA (8.48 ± 0.98 × 10(-6) dG, mean ± SEM n = 11) than normoglycemic ones (1.18 ± 0.04 × 10(-6) dG, mean ± SEM, n=7) and lower plasma Adp and FRAP levels in comparison to normoglycemics. The treatment of diabetic rats with losartan significantly (P < 0.01) reduced 8-oxodGuo levels (5.4 ± 0.58 × 10(-6) dG, mean ± SEM n=9) in renal DNA and conserved FRAP values. Moreover, an inverse correlation was found between 8-oxodGuo in kidney DNA and circulating Adp levels in normoglycemic and diabetic rats. Losartan treatment preserves FRAP levels, reduces DNA oxidative injury and thus the carcinogenesis risk. Furthermore, our results indicate that Adp plasma levels are a further marker of oxidative injury to the kidney and confirm that it is an important part of the plasma antioxidant defense.

The efficacy and tolerability of azilsartan in obese insulin-resistant mice with left ventricular pressure overload

Angiotensin II receptor blockers (ARBs) are used widely for the treatment of heart failure. However, their use in obese and insulin-resistant patients remains controversial. To clarify their potential efficacy in these conditions, we administered azilsartan medoxomil (azilsartan), a prodrug of an angiotensin II receptor blocker to mice fed a high-fat diet (HFD) with left ventricular (LV) pressure overload (aortic banding). LV fibrosis (hydroxyproline), cardiac plasminogen activator inhibitor-1 (PAI-1; a marker of profibrosis), and creatine kinase (a marker of myocardial viability and energetics) were assessed. LV wall thickness and cardiac function were assessed echocardiographically. Mice given a HFD were obese and insulin resistant. Their LV hypertrophy was accompanied by greater LV PAI-1 and reduced LV creatine kinase compared with normal diet controls. Drug treatment reduced LV wall thickness, hypertrophy, and PAI-1 and increased cardiac output after aortic banding compared with results in HFD vehicle controls. Thus, azilsartan exerted favorable biological effects on the hearts of obese insulin-resistant mice subjected to LV pressure overload consistent with its potential utility in patients with analogous conditions.

Association between prehypertension, metabolic and inflammatory markers, decreased adiponectin and enhanced insulinemia in obese subjects

Background

Obesity is associated with development of the cardiorenal metabolic syndrome, which is a constellation of risk factors, such as insulin resistance, inflammatory response, dyslipidemia, and high blood pressure that predispose affected individuals to well-characterized medical conditions such as diabetes, cardiovascular and kidney chronic disease. The study was designed to establish relationship between metabolic and inflammatory disorder, renal sodium retention and enhanced blood pressure in a group of obese subjects compared with age-matched, lean volunteers.

Methods

The study was performed after 14 h overnight fast after and before OGTT in 13 lean (BMI 22.92 ± 2.03 kg/m²) and, 27 obese (BMI 36.15 ± 3.84 kg/m²) volunteers. Assessment of HOMA-IR and QUICKI index were calculated and circulating concentrations of TNF-α, IL-6 and C-reactive protein, measured by immunoassay.

Results

The study shows that a hyperinsulinemic (HI: 10.85 ± 4.09 μg/ml) subgroup of well-characterized metabolic syndrome bearers-obese subjects show higher glycemic and elevated blood pressure levels when compared to lean and normoinsulinemic (NI: 5.51 ± 1.18 μg/ml, P < 0.027) subjects. Here, the combination of hyperinsulinemia, higher HOMA-IR (HI: 2.19 ± 0.70 (n = 12) vs. LS: 0.83 ± 0.23 (n = 12) and NI: 0.98 ± 0.22 (n = 15), P < 0.0001) associated with lower QUICKI in HI obese when compared with LS and NI volunteers (P < 0.0001), suggests the occurrence of insulin resistance and a defect in insulin-stimulated peripheral action. Otherwise, the adiponectin measured in basal period was significantly enhanced in NI subjects when compared to HI groups (P < 0.04). The report also showed a similar insulin-mediated reduction of post-proximal urinary sodium excretion in lean (LS: 9.41 ± 0.68% vs. 6.38 ± 0.92%, P = 0.086), and normoinsulinemic (NI: 8.41 ± 0.72% vs. 5.66 ± 0.53%, P = 0.0025) and hyperinsulinemic obese subjects (HI: 8.82 ± 0.98% vs. 6.32 ± 0.67%, P = 0.0264), after oral glucose load, despite elevated insulinemic levels in hyperinsulinemic obeses.

Conclusion

In conclusion, this study highlights the importance of adiponectin levels and dysfunctional inflammatory modulation associated with hyperinsulinemia and peripheral insulin resistance, high blood pressure, and renal dysfunction in a particular subgroup of obeses.

Impact of endovascular therapy on oxidative stress in patients with peripheral artery disease

BACKGROUND

Atherosclerosis is believed to be caused by oxidative stress. Endovascular therapy (EVT) is effective for claudication of patients with peripheral artery disease (PAD). However, its effect on oxidative stress in PAD patients is unknown. Here, the impact of EVT on oxidative stress in PAD patients is investigated.

METHODS AND RESULTS

Twenty-five PAD patients (Rutherford stage II or III) who underwent EVT were enrolled. The levels of diacron-reactive oxygen metabolite (d-ROM; an oxidative stress marker), ankle-brachial index (ABI), and maximum walking distance at baseline and at 3 months after EVT were measured. As compared with baseline values, the maximum walking distance and ABI improved significantly after EVT (109.9±104.2 vs. 313.7±271.8m, P<0.0001; 0.61±0.15 vs. 0.91±0.13m, P<0.0001, respectively). The improved exercise capacity and arterial flow induced a significant decrease in d-ROM levels (from 472.8±64.8 to 390.2±46.7U.CARR; P<0.0001). The decrease in d-ROM levels after EVT was more prominent in PAD patients with a high baseline d-ROM level. The increased ABI (r=0.524, P=0.0007) and maximum walking distance (r=-0.416, P=0.039) after EVT were significantly correlated with the decreased d-ROM levels.

CONCLUSIONS

The improved exercise capacity and peripheral blood flow induced by EVT decreases oxidative stress in PAD patients.

Arterial Stiffness: A Nexus between Cardiac and Renal Disease

Vascular disease is the leading cause of morbidity and mortality in the Western world, and vascular function is determined by structural and functional properties of the arterial vascular wall. Cardiorenal metabolic syndrome such as obesity, diabetes, hypertension, kidney disease, and aging are conditions that predispose to arterial stiffening, which is a pathological alteration of the vascular wall and ultimately results in target organ damage in heart and kidney. In this review, we provide new insights on the interactions between arterial stiffness, vascular resistance and pulse wave velocity as well as final end-organ damage in heart and kidney. Better understanding of the mechanisms of arterial functional and hemodynamic alteration may help in developing more refined therapeutic strategies aimed to reduce cardiovascular and chronic kidney diseases.

Detrimental role of humoral signalling in cardio-renal cross-talk

In critically ill patients, any acute organ injury is associated with a sudden change of circulating factors that may play a role in distant organ dysfunction through a complex cross-talk. In this issue, Virzì and colleagues discuss the relevance of humoral signalling between heart and kidney, focusing on type 1 and type 3 cardio-renal syndrome. We herein review the mechanisms of heart-kidney cross-talk, discussing the role of circulating detrimental mediators in the pathogenetic mechanisms of cardio-renal syndrome.

Serum paraoxonase 1 status and its association with atherogenic indexes in gentamicin-induced nephrotoxicity in rats treated with coenzyme Q10

Coenzyme Q10 is a natural antioxidant and scavenger of free radicals. In the present study, we examined the effect of coenzyme Q10 on paraoxonase 1 (PON1) activity, lipid profile, atherogenic indexes and relationship of PON 1 activity by high-density lipoprotein (HDL) and atherogenic indexes in gentamicin (GM)-induced nephrotoxicity rats. Thirty Sprague-Dawley rats were divided into three groups to receive saline; GM, 100 mg/kg/d; and GM plus coenzyme Q10 by 15 mg/kg i.p daily, respectively. After 12 days, animals were anaesthetized, blood samples were also collected before killing to measure the levels of triglyceride (TG), cholesterol (C), low-density lipoprotein (LDL), very low density lipoprotein (VLDL), HDL, atherogenic indexes and the activities of PON1 of all groups were analyzed. Data were analyzed by non-parametric Mann-Whitney test (using SPSS 13 software). Coenzyme Q10 significantly decreased TG, C, LDL, VLDL, atherogenic index, atherogenic coefficient and cardiac risk ratio. HDL level and PON1 activity were significantly increased when treated with coenzyme Q10. Also, the activity of PON 1 correlated positively with HDL and negatively with atherogenic coefficient, cardiac risk ratio 1 and cardiac risk ratio 2. This study showed that coenzyme Q10 exerts beneficial effects on PON1 activity, lipid profile, atherogenic index and correlation of PON 1 activity with HDL and atherogenic index in GM -induced nephrotoxicity rats.

Associations of job stress indicators with oxidative biomarkers in Japanese men and women

Some researchers have suggested that oxidative damage may be one of the mechanisms linking job stress with coronary heart disease. The aim of this study was to investigate the association between job stress indicators and oxidative biomarkers. The study included 567 subjects (272 men, 295 women) who answered questionnaires related to their work and underwent a medical examination. Job stress evaluated using the demands-control-support model was measured using the Job Content Questionnaire. Effort-reward imbalance was measured using the Effort-Reward Imbalance Questionnaire. Urinary hydrogen peroxide (H₂O₂) and 8-hydroxy-2'-deoxyguanosine (8-OHdG) were measured by the modified ferrous ion oxidation xylenol orange version-1 method and enzyme-linked immunosorbent assay, respectively. In men, the changes in the odds ratios for high urinary H₂O₂ associated with a 1-standard-deviation (SD) increase in worksite social support were 0.69 (95% confidence interval (CI) 0.53, 0.91) univariately and 0.68 (95%CI 0.51, 0.90) after adjustment for covariates. The change in the odds ratio for high urinary H₂O₂ associated with a 1-SD increase in effort-reward ratio was 1.35 (95% CI 1.03, 1.78) after adjustment for covariates. In women, there were no significant associations of the two job stress indicators with urinary H₂O₂ and 8-OHdG levels after adjustment for covariates (p > 0.05).

Acetaminophen attenuates doxorubicin-induced cardiac fibrosis via osteopontin and GATA4 regulation: reduction of oxidant levels

It is well documented in animal and human studies that therapy with the anti-cancer drug doxorubicin (DOX) induces fibrosis, cardiac dysfunction, and cell death. The most widely accepted mechanism of cardiac injury is through production of reactive oxygen species (ROS), which cause mitochondrial damage, sarcomere structural alterations, and altered gene expression in myocytes and fibroblasts. Here we investigated the effects of acetaminophen (APAP, N-acetyl-para-aminophenol) on DOX-induced cardiac injury and fibrosis in the presence or absence of osteopontin (OPN). H9c2 rat heart-derived embryonic myoblasts were exposed to increasing concentrations of DOX ± APAP; cell viability, oxidative stress, and OPN transcript levels were analyzed. We found a dose-dependent decrease in cell viability and a corresponding increase in intracellular oxidants at the tested concentrations of DOX. These effects were attenuated in the presence of APAP. RT-PCR analysis revealed a small increase in OPN transcript levels in response to DOX, which was suppressed by APAP. When male 10-12-week-old mice (OPN(+/+) or OPN(-/-)) were given weekly injections of DOX ± APAP for 4 weeks there was substantial cardiac fibrosis in OPN(+/+) and, to a lesser extent, in OPN(-/-) mice. In both groups, APAP decreased fibrosis to near baseline levels. Activity of the pro-survival GATA4 transcription factor was diminished by DOX in both mouse genotypes, but retained baseline activity in the presence of APAP. These effects were mediated, in part, by the ability of APAP, acting as an anti-inflammatory agent, to decrease intracellular ROS levels, consequently diminishing the injury-induced increase in OPN levels.

Maladaptive immune and inflammatory pathways lead to cardiovascular insulin resistance

Insulin resistance is a hallmark of obesity, the cardiorenal metabolic syndrome and type 2 diabetes mellitus (T2DM). The progression of insulin resistance increases the risk for cardiovascular disease (CVD). The significance of insulin resistance is underscored by the alarming rise in the prevalence of obesity and its associated comorbidities in the Unites States and worldwide over the last 40-50 years. The incidence of obesity is also on the rise in adolescents. Furthermore, premenopausal women have lower CVD risk compared to men, but this protection is lost in the setting of obesity and insulin resistance. Although systemic and cardiovascular insulin resistance is associated with impaired insulin metabolic signaling and cardiovascular dysfunction, the mechanisms underlying insulin resistance and cardiovascular dysfunction remain poorly understood. Recent studies show that insulin resistance in obesity and diabetes is linked to a metabolic inflammatory response, a state of systemic and tissue specific chronic low grade inflammation. Evidence is also emerging that there is polarization of macrophages and lymphocytes towards a pro-inflammatory phenotype that contributes to progression of insulin resistance in obesity, cardiorenal metabolic syndrome and diabetes. In this review, we provide new insights into factors, such as, the renin-angiotensin-aldosterone system, sympathetic activation and incretin modulators (e.g., DPP-4) and immune responses that mediate this inflammatory state in obesity and other conditions characterized by insulin resistance.

Adipose tissue dysfunction and the pathogenesis of metabolic syndrome

Metabolic syndrome is a growing research area. The underlying mechanisms of metabolic syndrome are still not very clear. Insulin resistance, obesity, inflammation and oxidative stress may play an important role in the pathogenesis of metabolic syndrome. The role of adipose tissue dysfunction is emphasized during the development of obesity. Adipose tissue is identified as a complex endocrine organ and its metabolic functions extend well beyond the classical actions of thermoregulation and of storage and release of fatty acids. Chronic low-grade inflammation activated by the immune system in adipose tissue is a key contributing factor to type 2 diabetes mellitus and cardiovascular diseases. Visceral obesity results in cell autonomous impairment in insulin signaling that leads to insulin resistance. Chronic inflammation in adipose tissue has gained acceptance as a lead promoter of insulin resistance in obesity. Furthermore, obesity creates oxidative stress conditions in adipose tissue that not only correlates with insulin resistance but is also causative in its development. Oxidative stress may be a mechanistic link between several components of metabolic syndrome and cardiovascular diseases, through its role in inflammation and its ability to disrupt insulin-signaling. The study around adipose tissue dysfunction will help to understand the pathogenesis of metabolic syndrome and may bring effective therapy in treatment of metabolic syndrome related diseases. Therefore, this review mainly focuses on the roles of adipose tissue dysfunction in inflammation, insulin resistance, and oxidative stress in the pathogenesis of metabolic syndrome.

Impact of aldosterone antagonists on the substrate for atrial fibrillation: aldosterone promotes oxidative stress and atrial structural/electrical remodeling

Atrial fibrillation (AF), the most common cardiac arrhythmia, is an electrocardiographic description of a condition with multiple and complex underlying mechanisms. Oxidative stress is an important driver of structural remodeling that creates a substrate for AF. Oxidant radicals may promote increase of atrial oxidative damage, electrical and structural remodeling, and atrial inflammation. AF and other cardiovascular morbidities activate angiotensin (Ang-II)-dependent and independent cascades. A key component of the renin-angiotensin-aldosterone system (RAAS) is the mineralocorticoid aldosterone. Recent studies provide evidence of myocardial aldosterone synthesis. Aldosterone promotes cardiac oxidative stress, inflammation and structural/electrical remodeling via multiple mechanisms. In HF patients, aldosterone production is enhanced. In patients and in experimental HF and AF models, aldosterone receptor antagonists have favorable influences on cardiac remodeling and oxidative stress. Therapeutic approaches that seek to reduce AF burden by modulating the aldosterone system are likely beneficial but underutilized.

Circulating nitrite and nitrate are associated with job-related fatigue in women, but not in men

A recent study indicated that serum nitrite and nitrate (NOx) is inversely associated with general fatigue. The purpose of this study was to confirm the negative association between nitric oxide (NO) and fatigue and to examine whether NO can prevent fatigue caused by job strain. The subjects, 570 workers (272 men and 298 women), answered self-administered questionnaires and underwent a medical examination. Job strain was measured using the Job Content Questionnaire. Fatigue was evaluated using the Profile of Mood States. Venous blood samples were collected after overnight fasting. Plasma NOx concentration was determined by the ozone-based chemiluminescence assay. Plasma NOx levels were significantly (p < 0.05) negatively associated with fatigue even after adjustment for job strain and potential confounders in women, but not in men. Significant (p < 0.05) interactions showed that, in women, as the level of the job strain worsened, fatigue was exacerbated, but the plasma NOx seemed to buffer the association, even after adjustment for potential confounders and the interaction between job strain and vegetable intake. In women, NO seemed to be inversely associated with fatigue and to buffer the association between job strain and fatigue, but not in men.

NADPH oxidase/ROS-dependent PYK2 activation is involved in TNF-α-induced matrix metalloproteinase-9 expression in rat heart-derived H9c2 cells

TNF-α plays a mediator role in the pathogenesis of chronic heart failure contributing to cardiac remodeling and peripheral vascular disturbances. The implication of TNF-α in inflammatory responses has been shown to be mediated through up-regulation of matrix metalloproteinase-9 (MMP-9). However, the detailed mechanisms of TNF-α-induced MMP-9 expression in rat embryonic-heart derived H9c2 cells are largely not defined. We demonstrated that in H9c2 cells, TNF-α induced MMP-9 mRNA and protein expression associated with an increase in the secretion of pro-MMP-9. TNF-α-mediated responses were attenuated by pretreatment with the inhibitor of ROS (N-acetyl-l-cysteine, NAC), NADPH oxidase [apocynin (APO) or diphenyleneiodonium chloride (DPI)], MEK1/2 (U0126), p38 MAPK (SB202190), JNK1/2 (SP600125), NF-κB (Bay11-7082), or PYK2 (PF-431396) and transfection with siRNA of TNFR1, p47(phox), p42, p38, JNK1, p65, or PYK2. Moreover, TNF-α markedly induced NADPH oxidase-derived ROS generation in these cells. TNF-α-enhanced p42/p44 MAPK, p38 MAPK, JNK1/2, and NF-κB (p65) phosphorylation and in vivo binding of p65 to the MMP-9 promoter were inhibited by U0126, SB202190, SP600125, NAC, DPI, or APO. In addition, TNF-α-mediated PYK2 phosphorylation was inhibited by NAC, DPI, or APO. PYK2 inhibition could reduce TNF-α-stimulated MAPKs and NF-κB activation. Thus, in H9c2 cells, we are the first to show that TNF-α-induced MMP-9 expression is mediated through a TNFR1/NADPH oxidase/ROS/PYK2/MAPKs/NF-κB cascade. We demonstrated that NADPH oxidase-derived ROS generation is involved in TNF-α-induced PYK2 activation in these cells. Understanding the regulation of MMP-9 expression and NADPH oxidase activation by TNF-α on H9c2 cells may provide potential therapeutic targets of chronic heart failure.

Obesity and Cardiac Function - The Role of Caloric Excess and its Reversal

Obesity is recognized as an independent and increasingly prevalent risk factor for cardiovascular morbidity and mortality. This stems in part from the contribution of obesity towards insulin resistance and diabetes, which associate with premature atherosclerosis, enhanced thrombogenicity and activation of systemic inflammatory programs with resultant cardiovascular dysfunction. This review will focus on the more direct mechanisms underpinning obesity-associated cardiac pathophysiology including the metabolic consequences of lipid accumulation in the myocardium and the consequences of direct systemic effects of lipid toxicity. Furthermore, there is growing recognition that metabolic intermediates, which may be perturbed with caloric excess, may play an important role in intracellular signal transduction and on the post-translational control of metabolic functioning within the heart. As strategies to reverse obesity appear to have ameliorative cardiac effects, surgical and therapeutic approaches to facilitate weight reduction this will also be discussed.

Obesity-associated oxidative stress: strategies finalized to improve redox state

Obesity represents a major risk factor for a plethora of severe diseases, including diabetes, cardiovascular disease, non-alcoholic fatty liver disease, and cancer. It is often accompanied by an increased risk of mortality and, in the case of non-fatal health problems, the quality of life is impaired because of associated conditions, including sleep apnea, respiratory problems, osteoarthritis, and infertility. Recent evidence suggests that oxidative stress may be the mechanistic link between obesity and related complications. In obese patients, antioxidant defenses are lower than normal weight counterparts and their levels inversely correlate with central adiposity; obesity is also characterized by enhanced levels of reactive oxygen or nitrogen species. Inadequacy of antioxidant defenses probably relies on different factors: obese individuals may have a lower intake of antioxidant- and phytochemical-rich foods, such as fruits, vegetables, and legumes; otherwise, consumption of antioxidant nutrients is normal, but obese individuals may have an increased utilization of these molecules, likewise to that reported in diabetic patients and smokers. Also inadequate physical activity may account for a decreased antioxidant state. In this review, we describe current concepts in the meaning of obesity as a state of chronic oxidative stress and the potential interventions to improve redox balance.

Direct renin inhibition prevents cardiac dysfunction in a diabetic mouse model: comparison with an angiotensin receptor antagonist and angiotensin-converting enzyme inhibitor

Hyperglycaemia up-regulates intracellular AngII (angiotensin II) production in cardiac myocytes, effects of which are blocked more effectively by renin inhibition than ARBs (angiotensin receptor blockers) or ACEis (angiotensin-converting enzyme inhibitors). In the present study, we determined whether renin inhibition is more effective at preventing diabetic cardiomyopathy than an ARB or ACEi. Diabetes was induced in adult mice for 10 weeks by STZ (streptozotocin). Diabetic mice were treated with insulin, aliskiren (a renin inhibitor), benazeprilat (an ACEi) or valsartan (an ARB) via subcutaneous mini-pumps. Significant impairment in diastolic and systolic cardiac functions was observed in diabetic mice, which was completely prevented by all three RAS (renin-angiotensin system) inhibitors. Hyperglycaemia significantly increased cardiac oxidative stress and circulating inflammatory cytokines, which were blocked by aliskiren and benazeprilat, whereas valsartan was partially effective. Diabetes increased cardiac PRR (prorenin receptor) expression and nuclear translocation of PLZF (promyelocytic zinc finger protein), which was completely prevented by aliskiren and valsartan, and partially by benazeprilat. Renin inhibition provided similar protection of cardiac function to ARBs and ACEis. Activation of PLZF by PRR represented a novel mechanism in diabetic cardiomyopathy. Differential effects of the three agents on oxidative stress, cytokines and PRR expression suggested subtle differences in their mechanisms of action.

New evidence for vascular interactions between aldosterone, angiotensin II and antioxidants in isolated smooth muscle cells of rats

Accumulating evidence suggests that the nongenomic cardiovascular actions of aldosterone are produced by varied cellular pathways and mediated by a multitude of messenger systems including the reactive oxygen and nitrogen species. Considering the involvement of the oxidative and nitrosative stress in the pathways leading to the activation of the angiotensin — aldosterone system, in the current study we tried to evaluate the functional interactions between aldosterone, angiotensin II and antioxidants in isolated vascular smooth muscle of aortic rings from rats. Our data provide additional arguments that the nongenomic actions of aldosterone on aortic smooth muscle cells of rats are a question of cross-talk and balance between its rapid vasoconstrictor and vasodilator effects, as result of the activation of reactive oxygen species in the first case and of nitrogen species in the second. In this way, it seems that at low ambient oxidative stress, aldosterone promotes nitric oxide (NO) production and vasodilatation, while in situations with increased oxidative stress the endothelial dysfunction and detrimental effects induced by vasoconstriction will prevail. Thus, aldosterone could be considered both “friend and foe”. This could be relevant for the ways in which aldosterone damages cardiovascular functions and could lead to significant therapeutic improvements.