Effect of exercise on cardiac tissue oxidative and inflammatory mediators in chronic kidney disease

Brazil nuts potential: effects on lipid peroxidation and heart health in nephrectomized rats

OBJECTIVES

To investigate the effects of a Brazil nut-enriched diet on the wall thickness and the left ventricular chamber diameter of the heart, and lipid peroxidation in a CKD-induced model.

METHODS

Male Wistar rats at 12 weeks of age were divided into two groups (n=16/group): the Nx group, which underwent 5/6 nephrectomy, and the Sham group, as a control. After 5 weeks, the groups were subdivided according to diet (n=8/group): the Nx and Sham groups received a control diet; the Nx5% and Sham5% groups received a diet enriched with 5 % Brazil nuts for 8 weeks. The left ventricular thickening and chamber diameter were determined. Plasma biochemical parameters were evaluated. Analysis of thiobarbituric acid reactive substances (TBARS) and antioxidant enzyme activity was performed in the plasma and the left ventricle (LV). LV mRNA expression of nuclear factor-kappa B (NF-κB) and nuclear factor erythroid 2-related factor 2 (Nrf2) was evaluated by reverse transcription-polymerase chain reaction.

RESULTS

The Nx5% group showed a remodeled LV wall with decreased thickness compared to the Nx group (p=0.016). Furthermore, LV TBARS concentration was reduced in the Nx5% group (p=0.0064). In addition, the Nx5% group showed an increase in plasma GPx activity (p=0.0431). No significant results were found concerning the LV mRNA expression of NF-κB and Nrf2 genes.

CONCLUSIONS

A Brazil nut-enriched diet decreased LV thickness and LV TBARS concentration and increased GPx activity in a 5/6 nephrectomy experimental model, making it a promising adjuvant therapy to improve antioxidant status and cardiovascular outcomes in chronic kidney disease.

The effect of epigenetic aging on neurodegenerative diseases: a Mendelian randomization study

Background

Aging has always been considered as a risk factor for neurodegenerative diseases, but there are individual differences and its mechanism is not yet clear. Epigenetics may unveil the relationship between aging and neurodegenerative diseases.

Methods

Our study employed a bidirectional two-sample Mendelian randomization (MR) design to assess the potential causal association between epigenetic aging and neurodegenerative diseases. We utilized publicly available summary datasets from several genome-wide association studies (GWAS). Our investigation focused on multiple measures of epigenetic age as potential exposures and outcomes, while the occurrence of neurodegenerative diseases served as potential exposures and outcomes. Sensitivity analyses confirmed the accuracy of the results.

Results

The results show a significant decrease in risk of Parkinson's disease with GrimAge (OR = 0.8862, 95% CI 0.7914-0.9924, p = 0.03638). Additionally, we identified that HannumAge was linked to an increased risk of Multiple Sclerosis (OR = 1.0707, 95% CI 1.0056-1.1401, p = 0.03295). Furthermore, we also found that estimated plasminogen activator inhibitor-1(PAI-1) levels demonstrated an increased risk for Alzheimer's disease (OR = 1.0001, 95% CI 1.0000-1.0002, p = 0.04425). Beyond that, we did not observe any causal associations between epigenetic age and neurodegenerative diseases risk.

Conclusion

The findings firstly provide evidence for causal association of epigenetic aging and neurodegenerative diseases. Exploring neurodegenerative diseases from an epigenetic perspective may contribute to diagnosis, prognosis, and treatment of neurodegenerative diseases.

Comparison of the Surgical Resection and Infarct 5/6 Nephrectomy Rat Models of Chronic Kidney Disease

The 5/6 nephrectomy rat remnant kidney model is commonly employed to study chronic kidney disease (CKD). This model requires removal of one whole kidney and two-thirds of the other. The two most common ways of producing the remnant kidney are surgical resection of poles, known as the polectomy (Pol) model, or ligation of upper and lower renal arterial branches, resulting in pole infarction (Inf). These models have much in common, but also major phenotypic differences, and thus respectively model unique aspects of human CKD. The purpose of this review is to summarize phenotypic similarities and differences between these two models and their relation to human CKD, while emphasizing their vascular phenotype. In this article we review studies that have evaluated arterial blood pressure, the renin-angiotensin-aldosterone-system (RAAS), autoregulation, nitric oxide, single nephron physiology, angiogenic and anti-angiogenic factors, and capillary rarefaction in these two models. Phenotypic similarities: both models spontaneously develop hallmarks of human CKD including uremia, fibrosis, capillary rarefaction, and progressive renal function decline. They both undergo whole-organ hypertrophy, hyperfiltration of functional nephrons, reduced renal expression of angiogenic factor VEGF, increased renal expression of the anti-angiogenic thrombospondin-1, impaired renal autoregulation, and abnormal vascular nitric oxide physiology. Key phenotypic differences: the Inf model develops rapid-onset, moderate-to-severe systemic hypertension, and the Pol model early normotension followed by mild-to-moderate hypertension. The Inf rat has a markedly more active renin-angiotensin-aldosterone-system. Comparison of these two models facilitates understanding of how they can be utilized for studying CKD pathophysiology (e.g., RAAS dependent or independent pathology).

Association between exercise frequency with renal and cardiovascular outcomes in diabetic and non-diabetic individuals at high cardiovascular risk

BACKGROUND

Guidelines recommend physical activity to reduce cardiovascular (CV) events. The association between physical activity and progression of chronic kidney disease (CKD) with and without diabetes is unknown. We assessed the association of self-reported physical activity with renal and CV outcomes in high-risk patients aged ≥ 55 years over a median follow-up of 56 months in post-hoc analysis of a previously randomized trial program.

METHODS

Analyses were done with Cox regression analysis, mixed models for repeated measures, ANOVA and χ2-test. 31,312 patients, among them 19,664 with and 11,648 without diabetes were analyzed.

RESULTS

Physical activity was inversely associated with renal outcomes (doubling of creatinine, end-stage kidney disease (ESRD)) and CV outcomes (CV death, myocardial infarction, stroke, heart failure hospitalization). Moderate activity (at least 2 times/week to every day) was associated with lower risk of renal outcomes and lower incidence of new albuminuria (p < 0.0001 for both) compared to lower exercise levels. Similar results were observed for those with and without diabetes without interaction for renal outcomes (p = 0.097-0.27). Physical activity was associated with reduced eGFR decline with a moderate association between activity and diabetes status (p = 0.05).

CONCLUSIONS

Moderate physical activity was associated with improved kidney outcomes with a threshold at two sessions per week. The association of physical activity with renal outcomes did not meaningfully differ with or without diabetes but absolute benefit of activity was even greater in people with diabetes. Thus, risks were similar between those with diabetes undertaking high physical activity and those without diabetes but low physical activity.

CLINICAL TRIAL REGISTRATION

http://clinicaltrials.gov.uniqueidentifier :NCT00153101.

Risk factors of chronic kidney disease among type 2 diabetic patients with longer duration of diabetes

BACKGROUND

Chronic kidney disease (CKD) in patients with type 2 diabetes mellitus (T2DM) is the major cause of end stage renal disease, characterized by proteinuria with a subsequent decline in glomerular filtration rate. Although hyperglycemia is the major risk factor for the development and progression of kidney disease among diabetic patients, many other risk factors also contribute to structural and functional changes in the kidneys. As recommended by Kidney Disease Improving Global Outcomes (KDIGO), CKD classification based on cause and severity, links to risk of adverse outcomes including mortality and kidney outcomes.

OBJECTIVE

The aim of this study is to investigate the involvement of risk factors associated with the severity of CKD among participants with longer duration of diabetes. This study also aims to find whether number of risk factors vary among risk of CKD progression categories based on KDIGO classification.

MATERIAL AND METHODS

This cross-sectional study retrospectively selected 424 participants from type 2 diabetic cohort and categorized them based on the classifications for the diagnosis of kidney diseases in patients with diabetes, according to the KDIGO guidelines. Odds ratios and 95% CI of each risk factors according to severity of renal disease were determined.

RESULTS

Based on KDIGO classification, participants with type 2 diabetes (T2D) were categorized in to low risk (n=174); moderately increased risk (n=98); and high/very high risk (n=152). Type 2 diabetic participants with risk factors such as, hyperlipidemia, hypertension, DM duration ≥15 years and diabetic retinopathy showed a high/very high risk of CKD progression when compared with low-risk category. While T2D participants with risk factors such as, lack of exercise, hypertension, and diabetic retinopathy showed a moderately increased risk of CKD progression. In addition, participants with highest number of risk factors were significantly distributed among high/very high risk of CKD progression category.

CONCLUSION

This study findings conclude that patients with T2DM and duration of ≥15 years, hyperlipidemia, hypertension and diabetic retinopathy have an increased prevalence of advanced CKD. In addition to this, increased number of risk factors could be an indicator of the severity of CKD in T2D.

The Role of Obesity-Induced Perivascular Adipose Tissue (PVAT) Dysfunction in Vascular Homeostasis

Perivascular adipose tissue (PVAT) is an additional special type of adipose tissue surrounding blood vessels. Under physiological conditions, PVAT plays a significant role in regulation of vascular tone, intravascular thermoregulation, and vascular smooth muscle cell (VSMC) proliferation. PVAT is responsible for releasing adipocytes-derived relaxing factors (ADRF) and perivascular-derived relaxing factors (PDRF), which have anticontractile properties. Obesity induces increased oxidative stress, an inflammatory state, and hypoxia, which contribute to PVAT dysfunction. The exact mechanism of vascular dysfunction in obesity is still not well clarified; however, there are some pathways such as renin-angiotensin-aldosterone system (RAAS) disorders and PVAT-derived factor dysregulation, which are involved in hypertension and endothelial dysfunction development. Physical activity has a beneficial effect on PVAT function among obese patients by reducing the oxidative stress and inflammatory state. Diet, which is the second most beneficial non-invasive strategy in obesity treatment, may have a positive impact on PVAT-derived factors and may restore the balance in their concentration.

Role of Perivascular Adipose Tissue and Exercise on Arterial Function with Obesity

Adipose tissue and arterial dysfunction are common in the obese state. Perivascular adipose tissue (PVAT) plays an important role in mediating arterial health, and with obesity, the PVAT dysfunction negatively affects arterial health. Exercise training exerts direct and beneficial effects on PVAT, providing an additional and novel pathway by which exercise can improve arterial health in diseased populations.

Early Moderate Intensity Aerobic Exercise Intervention Prevents Doxorubicin-Caused Cardiac Dysfunction Through Inhibition of Cardiac Fibrosis and Inflammation

Doxorubicin (DOX) is known as an effective drug in the fight against various cancers. However, one of the greatest impediments is DOX-induced cardiomyopathy, which may potentially lead to heart failure. Accumulating evidence has shed light on the pathological mechanism of DOX-induced cardiotoxicity, but treatments to mitigate the cardiac damage are still required. In an attempt to address this issue, we evaluated whether exercise provides cardioprotective effects on the DOX-induced cardiotoxicity. We showed that treadmill exercise (3 times/week; 1-week of exercise acclimatization and 4-weeks of endurance exercise) during the DOX treatment successfully prevented the cardiac dysfunction. The DOX-stimulated expression of IκBα, NF-κB, COX-2, and IL-8 were all downregulated by exercise as well as the fibrosis factors (TGF-β1, phosphorylated ERK, Sp1, and CTGF). Moreover, we showed that treadmill exercise diminished the expression of several cardiac remodeling-associated factors, such as FGF2, uPA, MMP2, and MMP9. These results were in line with the finding that exercise intervention reduced cardiac fibrosis and restored cardiac function, with higher values of ejection fraction and fractional shortening compared to the DOX-treated group. Two commonly used indicators of cardiac injury, lactate dehydrogenase, and creatine kinase-MB, were also decreased in the exercise group. Collectively, our results suggested that it may be beneficial to prescribe treadmill exercise as an adjunct therapy to limit cardiac damage caused by DOX.

Association between calcitriol and paricalcitol with oxidative stress in patients with hemodialysis

Background: The pathophysiological basis of chronic kidney disease and its complications, including cardiovascular disease, are associated with chronic inflammation and oxidative stress. We investigated the effects of active vitamin D (calcitriol) and synthetic vitamin D analog (paricalcitol) on oxidative stress in hemodialysis patients. Methods: This cross-sectional study was composed of 83 patients with a minimum hemodialysis vintage of one year. Patients with a history of any infection, malignancy, and chronic inflammatory disease were excluded. Oxidative markers (total oxidant and antioxidant status) and inflammation markers (C-reactive protein and interleukin-6) were analyzed. Results: A total of 47% (39/83) patients were using active or analog vitamin D. Total antioxidant status was significantly higher in patients with using active or analog vitamin D than those who did not use (p = 0.006). Whereas, total oxidant status and oxidative stress index were significantly higher in patients with not using vitamin D when compared with the patients who were using vitamin D preparation (p = 0.005 and p = 0.004, respectively). On the other hand, total antioxidant status, total oxidant status, and oxidative stress index were similar between patients who used active vitamin D or vitamin D analog (p = 0.6; p = 0.4 and p = 0.7, respectively). Conclusion: The use of active or selective vitamin D analog in these patients decreases total oxidant status and increases total antioxidant status. Also, paricalcitol is as effective as calcitriol in decreasing total oxidant status and increasing total antioxidant status in patients with chronic kidney disease.

Voluntary Wheel Running Has Beneficial Effects in a Rat Model of CKD-Mineral Bone Disorder (CKD-MBD)

BACKGROUND

Reduced bone and muscle health in individuals with CKD contributes to their higher rates of morbidity and mortality.

METHODS

We tested the hypothesis that voluntary wheel running would improve musculoskeletal health in a CKD rat model. Rats with spontaneous progressive cystic kidney disease (Cy/+ _IU) and normal littermates (NL) were given access to a voluntary running wheel or standard cage conditions for 10 weeks starting at 25 weeks of age when the rats with kidney disease had reached stage 2-3 of CKD. We then measured the effects of wheel running on serum biochemistry, tissue weight, voluntary grip strength, maximal aerobic capacity (VO_2max), body composition and bone micro-CT and mechanics.

RESULTS

Wheel running improved serum biochemistry with decreased creatinine, phosphorous, and parathyroid hormone in the rats with CKD. It improved muscle strength, increased time-to-fatigue (for VO_2max), reduced cortical porosity and improved bone microarchitecture. The CKD rats with voluntary wheel access also had reduced kidney cystic weight and reduced left ventricular mass index.

CONCLUSIONS

Voluntary wheel running resulted in multiple beneficial systemic effects in rats with CKD and improved their physical function. Studies examining exercise interventions in patients with CKD are warranted.

Effects of ascorbic acid supplementation on oxidative stress markers in healthy women following a single bout of exercise

BACKGROUND

Ascorbic acid is a water-soluble chain breaking antioxidant. It scavenges free radicals and reactive oxygen species (ROS), which are produced during metabolic pathways. Exercise can produce an imbalance between ROS and antioxidants, leading to oxidative stress-related tissue damages. This study was designed to determine the effects of ascorbic acid supplementation on circulating biomarkers of oxidative stress and muscle damage following a single bout of exercise.

METHODS

In a crossover design with a 1 wk. wash-out period, 19 healthy women performed 30 min moderate-intensity cycling after ingesting 1000 mg of ascorbic acid (AA) or placebo. Blood samples were taken immediately before, immediately after and 30 min post-exercise to determine plasma albumin, total protein, glucose, oxidative stress and muscle damage markers.

RESULTS

Plasma albumin and total protein levels increased immediately after exercise in placebo alongside slight reductions in glucose (p = 0.001). These effects were absent in AA cohort. Ferric reducing ability of plasma and vitamin C levels in AA cohort significantly increased after exercise (p < 0.05). Superoxide dismutase activity was significantly elevated after exercise (p = 0.002) in placebo but not AA. Plasma malondialdehyde did not change after exercise in placebo but was significantly decreased in AA (p < 0.05). The exercise protocol promoted slight muscle damage, reflected in significant increases in total creatine kinase in all subjects after exercise. On the other hand, plasma C-reactive protein and lactate dehydrogenase remained unchanged.

CONCLUSION

Supplementation with ascorbic acid prior exercise improves antioxidant power but does not prevent muscle damage.

Mechanisms and Modulation of Oxidative/Nitrative Stress in Type 4 Cardio-Renal Syndrome and Renal Sarcopenia

Chronic kidney disease (CKD) is a public health problem and a recognized risk factor for cardiovascular diseases (CVD). CKD could amplify the progression of chronic heart failure leading to the development of type 4 cardio-renal syndrome (T4CRS). The severity and persistence of heart failure are strongly associated with mortality risk in T4CRS. CKD is also a catabolic state leading to renal sarcopenia which is characterized by the loss of skeletal muscle strength and physical function. Renal sarcopenia also promotes the development of CVD and increases the mortality in CKD patients. In turn, heart failure developed in T4CRS could result in chronic muscle hypoperfusion and metabolic disturbances leading to or aggravating the renal sarcopenia. The interplay of multiple factors (e.g., comorbidities, over-activated renin-angiotensin-aldosterone system [RAAS], sympathetic nervous system [SNS], oxidative/nitrative stress, inflammation, etc.) may result in the progression of T4CRS and renal sarcopenia. Among these factors, oxidative/nitrative stress plays a crucial role in the complex pathomechanism and interrelationship between T4CRS and renal sarcopenia. In the heart and skeletal muscle, mitochondria, nicotinamide adenine dinucleotide phosphate (NADPH) oxidases, uncoupled nitric oxide synthase (NOS) and xanthine oxidase are major ROS sources producing superoxide anion (O2^·−) and/or hydrogen peroxide (H₂O₂). O2^·− reacts with nitric oxide (NO) forming peroxynitrite (ONOO⁻) which is a highly reactive nitrogen species (RNS). High levels of ROS/RNS cause lipid peroxidation, DNA damage, interacts with both DNA repair enzymes and transcription factors, leads to the oxidation/nitration of key proteins involved in contractility, calcium handling, metabolism, antioxidant defense mechanisms, etc. It also activates the inflammatory response, stress signals inducing cardiac hypertrophy, fibrosis, or cell death via different mechanisms (e.g., apoptosis, necrosis) and dysregulates autophagy. Therefore, the thorough understanding of the mechanisms which lead to perturbations in oxidative/nitrative metabolism and its relationship with pro-inflammatory, hypertrophic, fibrotic, cell death and other pathways would help to develop strategies to counteract systemic and tissue oxidative/nitrative stress in T4CRS and renal sarcopenia. In this review, we also focus on the effects of some well-known and novel pharmaceuticals, nutraceuticals, and physical exercise on cardiac and skeletal muscle oxidative/nitrative stress in T4CRS and renal sarcopenia.

Effects of treadmill running in a rat model of chronic kidney disease

Chronic kidney disease (CKD) progression results in musculoskeletal dysfunction that is associated with a higher likelihood of hospitalization and is predictive of hospitalizations and mortality. Despite this, there is a lack of effective interventions to treat the musculoskeletal dysfunction. We studied treadmill running as an intervention to improve musculoskeletal health in a translational rat model that has slowly progressive CKD. CKD rats were subjected to treadmill exercise or no treadmill exercise for 10 weeks (n = 8 each group). Animals ran for 60 min, 5 times per week starting at a speed of 8 m/min and ending at 18 m/min (1 m/min increase/week). Treadmill training had no effect on muscle strength (assessed as maximally stimulated torque), half-relaxation time (time from peak torque to 50%) or muscle cross-sectional area. Overall, there were no biochemical improvements related to CKD progression. Skeletal muscle catabolism was higher than non-exercised animals without a concomitant change in muscle synthesis markers or regeneration transcription factors. These results suggest that aerobic exercise, achieved via treadmill running was not protective in CKD animals and actually produced potentially harmful effects (increased catabolism). Given the high prevalence and dramatic musculoskeletal mobility impairment in patients with CKD, there is a clear need to understand how to effectively prescribe exercise in order to benefit the musculoskeletal system.

LCZ696 (Sacubitril/Valsartan), an Angiotensin-Receptor Neprilysin Inhibitor, Attenuates Cardiac Hypertrophy, Fibrosis, and Vasculopathy in a Rat Model of Chronic Kidney Disease

BACKGROUND

Chronic kidney disease (CKD) is associated with cardiac hypertrophy, fibrosis, and increased risk of cardiovascular mortality. LCZ696 (sacubitril/valsartan) is a promising agent that has shown significant potential in treatment of heart failure. We hypothesized that LCZ696 is more effective than valsartan alone in the treatment of cardiovascular abnormalities associated with experimental CKD.

METHODS AND RESULTS

Male Sprague-Dawley rats underwent 5/6 nephrectomy and were subsequently randomized to no treatment (CKD), 30 mg/kg valsartan (VAL), or 60 mg/kg LCZ696 (LCZ). After 8 weeks, cardiovascular parameters, including markers of inflammation, oxidative stress, mitochondrial abundance/function, hypertrophy, and fibrosis, were measured. Treatment with LCZ resulted in significant improvements in the heart-body weight ratio and serum concentrations of N-terminal pro-B-type natriuretic peptide and fibroblast growth factor 23 along with improvement of kidney function. In addition, LCZ ameliorated aortic fibrosis and cardiac hypertrophy and fibrosis, reduced markers of cardiac oxidative stress and inflammation, and improved indicators of mitochondrial mass/function. Although VAL also improved some of these indices, treatment with LCZ was more effective than VAL alone.

CONCLUSIONS

CKD-associated cardiovascular abnormalities, including myocardial hypertrophy, fibrosis, inflammation, oxidative stress, and mitochondrial depletion/dysfunction, were more effectively attenuated by LCZ treatment than by VAL alone.

[Exercise as a protective cardiovascular and metabolic factor in end stage renal disease patients]

OBJECTIVE

The aim of the study was to test the effectiveness of Physical Activity (PA) during haemodialysis as a protective treatment against cardiovascular (CV) diseases.

METHODS

Eighty volunteer patients were included in this multicentric prospective study and followed for two years: 40 patients in the Exercise group (EX), 40 patients in the Control group (Ctrl). CV risk factors: Total Cholesterol, HDL Cholesterol (HDL-c), LDL cholesterol (LDL-c), Triglycerides (TG) and Hemoglobin (Hb), and Prealbumin, Albumin, Parathormon, 25-OH Vitamin D, were checked at Month 0 (M0) and Month 24 (M24). The number of antihypertensive treatments and the Erythropoietin Stimulating Agent (ESA) required doses were collected. We noted for each group during the follow-up the number of hospitalizations for CV reasons. After two years, we compared 31 patients in EX and 35 in Ctrl.

RESULTS

We observed a significant decrease of total cholesterol EX group: 1.86±0.49g/L at M0 versus 1.64±0.38g/L at M24 (P<0.05). HDLc and but LDL-c remained stable in both groups. TG decreased significantly in EX: 1.76±0.89g/L vs 1.44±0.69g/L (P<0.05). The number of antihypertensive drugs per patient decreased significantly (P<0.05) in the EX group between M0 and M24 (1.61±1.28 at M0 and 0.74±0.85 at M24). The EX patients were three times less frequently hospitalized for cardiovascular reasons. There were five hospital stays versus 14 for the Ctrl group.

CONCLUSION

Our study demonstrates that an intradialytic aerobic cycling training program promotes beneficial effects on cardiovascular protection. Physical activity reduced the number of CV events in our population during two years follow-up.

Role of Gut-derived Uremic Toxins on Oxidative Stress and Inflammation in Patients with Chronic Kidney Disease

Several cardiovascular disease (CVD) risk factors have been identified among patients with chronic kidney disease (CKD). Gut-derived uremic toxins (GDUT) are important modifiable contributors in this respect. There are very few Indian studies on GDUT changes in CKD. One hundred and twenty patients older than 18 years diagnosed with CKD were enrolled along with forty healthy subjects. The patients were classified into three groups of forty patients based on stage of CKD. Indoxyl sulfate (IS), para cresyl sulfate (p-CS), indole acetic acid (IAA), and phenol were estimated along with the assessment of oxidative stress (OS), inflammatory state, and bone mineral disturbance. All the GDUT increased across the three groups of CKD. All patients had higher levels of malondialdehyde (MDA), ferric reducing ability of plasma (FRAP), high-sensitivity C-reactive protein (hsCRP), and interleukin-6 (IL-6) as compared to controls. IS and IAA showed positive association with MDA/FRAP corrected for uric acid, whereas IS and p-CS showed positive association with IL-6. IS, IAA, and phenol showed a positive association with calcium × phosphorus product. GDUT increase OS and inflammatory state in CKD and may contribute to CVD risk.

Manganese superoxide dismutase, glutathione peroxidase and catalase gene polymorphisms and clinical outcomes in acute kidney injury

INTRODUCTION

The aim of this study was to evaluate the potential association of single gene polymorphisms of manganese superoxide dismutase (MnSOD), glutathione peroxidase 1 (GPX1) and catalase (CAT) with clinical outcomes of acute kidney injury (AKI).

MATERIALS AND METHODS

Ninety AKI patients and 101 healthy volunteers were included in the study. Determination of MnSOD rs4880, GPX1 rs1050450 and CAT rs769217 polymorphisms was performed using real-time polymerase chain reaction amplification. The duration of hospitalization of AKI patients, dialysis and intensive care requirements, sepsis, oliguria and in-hospital mortality rates were assessed.

RESULTS

The MnSOD, GPX1 and CAT genotypes and allele frequencies of AKI patients did not differ significantly from those of healthy controls. In patients with a T allele in the ninth exon of the CAT gene, intensive care requirements were greater than those of patients with the CC genotype (p = 0.04). In addition, sepsis and in-hospital mortality were observed significantly more frequently in patients with a T allele in the ninth exon of the CAT gene (p = 0.03). Logistic regression analysis determined that bearing a T allele was the primary determinant of intensive care requirements and in-hospital mortality, independent of patient age, gender, presence of diabetes and dialysis requirements (OR 6.10, 95% CI 1.34-27.81, p = 0.02 and OR 10.25, 95% CI 1.13-92.80, p = 0.04, respectively).

CONCLUSION

Among AKI patients in the Turkish population, hospital morbidity and mortality were found to be more frequent in patients bearing a T allele of the rs769217 polymorphism of the CAT gene.

Arterial function in cardio-metabolic diseases: from the microcirculation to the large conduits

The metabolic syndrome (MetS) is characterized as a constellation of metabolic risk factors such as obesity, hypertension, dyslipidemia, and hyperglycemia that co-occur within a given individual. This consultation of risk factors exposes MetS to a 3-fold increased risk of cardiovascular disease and an even higher risk of developing type 2 diabetes compared to healthy individuals. The pathophysiological mechanisms underlying this increased cardiovascular risk are incompletely understood but likely include alterations to macro- and micro-vasculature. The vasculature plays an important role not only in delivery and adjusting the quantity of blood delivered to the tissues, but the dynamic changes in structure and compliance significantly alter the hemodynamic stress imposed on the heart and end-organs. This review will give an overview of the pathophysiological changes to the vasculature that accompany MetS in both human and animal models, as well as the possible mechanistic pathways.

The cardiovascular effect of the uremic solute indole-3 acetic acid

In CKD, uremic solutes may induce endothelial dysfunction, inflammation, and oxidative stress, leading to increased cardiovascular risk. We investigated whether the uremic solute indole-3 acetic acid (IAA) predicts clinical outcomes in patients with CKD and has prooxidant and proinflammatory effects. We studied 120 patients with CKD. During the median study period of 966 days, 29 patients died and 35 experienced a major cardiovascular event. Kaplan-Meier analysis revealed that mortality and cardiovascular events were significantly higher in the higher IAA group (IAA>3.73 µM) than in the lower IAA group (IAA<3.73 µM). Multivariate Cox regression analysis demonstrated that serum IAA was a significant predictor of mortality and cardiovascular events after adjustments for age and sex; cholesterol, systolic BP, and smoking; C-reactive protein, phosphate, body mass index, and albumin; diastolic BP and history of cardiovascular disease; and uremic toxins p-cresyl sulfate and indoxyl sulfate. Notably, IAA level remained predictive of mortality when adjusted for CKD stage. IAA levels were positively correlated with markers of inflammation and oxidative stress: C-reactive protein and malondialdehyde, respectively. In cultured human endothelial cells, IAA activated an inflammatory nongenomic aryl hydrocarbon receptor (AhR)/p38MAPK/NF-κB pathway that induced the proinflammatory enzyme cyclooxygenase-2. Additionally, IAA increased production of endothelial reactive oxygen species. In conclusion, serum IAA may be an independent predictor of mortality and cardiovascular events in patients with CKD. In vitro, IAA induces endothelial inflammation and oxidative stress and activates an inflammatory AhR/p38MAPK/NF-κB pathway.

Cardiac function and tolerance to ischemia-reperfusion injury in chronic kidney disease

BACKGROUND

Cardiac dysfunction is an independent risk factor of ischemic heart disease and mortality in chronic kidney disease (CKD) patients, yet the relationship between impaired cardiac function and tolerance to ischemia-reperfusion (IR) injury in experimental CKD remains unclear.

METHODS

Cardiac function was assessed in 5/6 ablation-infarction (AI) and sham male Sprague-Dawley rats at 20 weeks of age, 8 weeks post-surgery using an isolated working heart system. This included measures taken during manipulation of preload and afterload to produce left ventricular (LV) function curves as well as during reperfusion following a 15-min ischemic bout. In addition, LV tissue was used for biochemical tissue analysis.

RESULTS

Cardiac function was impaired in AI animals during preload and afterload manipulations. Cardiac functional impairments persisted post-ischemia in the AI animals, and 36% of AI animals did not recover sufficiently to achieve aortic overflow following ischemia (versus 0% of sham animals). However, for those animals able to withstand the ischemic perturbation, no difference was observed in percent recovery of post-ischemic cardiac function between groups. Urinary NOx (nitrite + nitrate) excretion was lower in AI animals and accompanied by reduced LV endothelial nitric oxide synthase and NOx. LV antioxidants superoxide dismutase-1 and -2 were reduced in AI animals, whereas glutathione peroxidase-1/2 as well as NADPH-oxidase-4 and H(2)O(2) were increased in these animals.

CONCLUSIONS

Impaired cardiac function appears to predispose AI rats to poor outcomes following short-duration ischemic insult. These findings could be, in part, mediated by increased oxidative stress via nitric oxide-dependent and -independent mechanisms.

Preconditioning protects the heart in a prolonged uremic condition

Metabolic diseases such as hyperlipidemia and diabetes attenuate the cardioprotective effect of ischemic preconditioning. In the present study, we examined whether another metabolic disease, prolonged uremia, affects ischemia/reperfusion injury and cardioprotection by ischemic preconditioning. Uremia was induced by partial nephrectomy in male Wistar rats. The development of uremia was verified 29 wk after surgery. Transthoracic echocardiography was performed to monitor cardiac function. At week 30, hearts of nephrectomized and sham-operated rats were isolated and subjected to a 30-min coronary occlusion followed by 120 min reperfusion with or without preceding preconditioning induced by three intermittent cycles of brief ischemia and reperfusion. In nephrectomized rats, plasma uric acid, carbamide, and creatinine as well as urine protein levels were increased as compared with sham-operated controls. Systolic anterior and septal wall thicknesses were increased in nephrectomized rats, suggesting the development of a minimal cardiac hypertrophy. Ejection fraction was decreased and isovolumic relaxation time was shortened in nephrectomized rats demonstrating a mild systolic and diastolic dysfunction. Infarct size was not affected significantly by nephrectomy itself. Ischemic preconditioning significantly decreased infarct size from 24.8 ± 5.2% to 6.6 ± 1.3% in the sham-operated group and also in the uremic group from 35.4 ± 9.5% to 11.9 ± 3.1% of the area at risk. Plasma ANG II and nitrotyrosine were significantly increased in the uremic rats. We conclude that although prolonged experimental uremia leads to severe metabolic changes and the development of a mild myocardial dysfunction, the cardioprotective effect of ischemic preconditioning is still preserved.

Establishment of a model of atrial fibrillation associated with chronic kidney disease in rats and the role of oxidative stress

BACKGROUND

An animal model of atrial fibrillation (AF) associated with chronic kidney disease (CKD) has not been available.

OBJECTIVE

The purpose of this study was to test the validity of 5/6 nephrectomy (5.6Nx) as an appropriate model of AF associated with CKD and to investigate the role of oxidative stress.

METHODS

Male Sprague-Dawley rats were subjected to 5.6Nx. A novel derivative of lipoic acid, sodium zinc dihydrolipoylhistidinate (DHLHZn), was subcutaneously infused. Four weeks later, hearts were isolated.

RESULTS

We observed 5 main findings. (1) 5.6Nx induced renal dysfunction with elevation of systolic blood pressure and impaired glucose tolerance. (2) In the left atrium (LA), expressions of α-smooth muscle action and collagen type I, the compositional proteins of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase, and malondialdehyde were increased by 5.6Nx, which was reversed by DHLHZn treatment. (3) In the LA, the tissue content of angiotensin II was elevated by 5.6Nx, which was also reversed by DHLHZn. (4) Masson trichrome staining revealed that heterogeneous LA interstitial fibrosis was induced by 5.6Nx, which was attenuated by DHLHZn. (5) In isolated perfused heart experiments, 5.6Nx caused slowing of interatrial conduction. In the hearts of rats of the 5.6Nxgroup, right atrial extrastimuli invariably induced AF (8/8 [100%]), which were suppressed by DHLHZn (3/8 [38%], P <.05).

CONCLUSION

We successfully established an appropriate model of AF associated with CKD in rats. Because the amount of NADPH oxidase was increased and the potent antioxidant agent DHLHZn was effective, oxidative stress may be involved in the pathogenesis of LA fibrosis and enhanced AF vulnerability in our model.

Inflammation, diabetes, and chronic kidney disease: role of aerobic capacity

The persistent inflammatory state is common in diabetes and chronic kidney disease (CKD). These patients present exercise intolerance and increased arterial stiffness. Long-term aerobic exercise has been associated with better arterial compliance, antidiabetic and antiinflammatory benefits. We assessed the hypothesis that in patients with diabetes and CKD, better aerobic capacity is associated with less inflammatory state and arterial stiffness. Thirty-nine CKD patients (17 in hemodialysis) were evaluated. According to CKD etiology two patient groups were obtained: group of diabetics (GD) was formed by 11 patients and nondiabetics (GND) formed by 28 patients. Central blood pressure and arterial stiffness were evaluated by Sphygmocor device. Carotida intima-media thickness (CA-IMT) was evaluated by ultrasonography. Aerobic capacity was measured by estimated VO₂max according to treadmill test by Bruce protocol. The GD showed a higher frequency of C-reactive protein above laboratory cutoff (P = 0.044), higher frequency of male gender, and a non significant higher value of VO₂max (P = 0.099). The CA-IMT was similar. Only better aerobic capacity was associated with lower frequency of high C-reactive protein when adjusted to diabetes and gender in a logistic regression model. In conclusion, aerobic capacity was associated with inflammatory state, in CKD patients, independently of diabetes presence.

Experimental models of renal disease and the cardiovascular system

Cardiovascular disease is a leading cause of death among patients with end stage renal failure. Animal models have played a crucial role in teasing apart the complex pathological processes involved. This review discusses the principles of using animal models, the history of their use in the study of renal hypertension, the controversies arising from experimental models of non-hypertensive uraemic cardiomyopathy and the lessons learned from these models, and highlights important areas of future research in this field, including de novo cardiomyopathy secondary to renal transplantation.

Hypercholesterolemia and microvascular dysfunction: interventional strategies

Hypercholesterolemia is defined as excessively high plasma cholesterol levels, and is a strong risk factor for many negative cardiovascular events. Total cholesterol levels above 200 mg/dl have repeatedly been correlated as an independent risk factor for development of peripheral vascular (PVD) and coronary artery disease (CAD), and considerable attention has been directed toward evaluating mechanisms by which hypercholesterolemia may impact vascular outcomes; these include both results of direct cholesterol lowering therapies and alternative interventions for improving vascular function. With specific relevance to the microcirculation, it has been clearly demonstrated that evolution of hypercholesterolemia is associated with endothelial cell dysfunction, a near-complete abrogation in vascular nitric oxide bioavailability, elevated oxidant stress, and the creation of a strongly pro-inflammatory condition; symptoms which can culminate in profound impairments/alterations to vascular reactivity. Effective interventional treatments can be challenging as certain genetic risk factors simply cannot be ignored. However, some hypercholesterolemia treatment options that have become widely used, including pharmaceutical therapies which can decrease circulating cholesterol by preventing either its formation in the liver or its absorption in the intestine, also have pleiotropic effects with can directly improve peripheral vascular outcomes. While physical activity is known to decrease PVD/CAD risk factors, including obesity, psychological stress, impaired glycemic control, and hypertension, this will also increase circulating levels of high density lipoprotein and improving both cardiac and vascular function. This review will provide an overview of the mechanistic consequences of the predominant pharmaceutical interventions and chronic exercise to treat hypercholesterolemia through their impacts on chronic sub-acute inflammation, oxidative stress, and microvascular structure/function relationships.

Reactive oxygen species and vascular biology: implications in human hypertension

Increased vascular production of reactive oxygen species (ROS; termed oxidative stress) has been implicated in various chronic diseases, including hypertension. Oxidative stress is both a cause and a consequence of hypertension. Although oxidative injury may not be the sole etiology, it amplifies blood pressure elevation in the presence of other pro-hypertensive factors. Oxidative stress is a multisystem phenomenon in hypertension and involves the heart, kidneys, nervous system, vessels and possibly the immune system. Compelling experimental and clinical evidence indicates the importance of the vasculature in the pathophysiology of hypertension and as such much emphasis has been placed on the (patho)biology of ROS in the vascular system. A major source for cardiovascular, renal and neural ROS is a family of non-phagocytic nicotinamide adenine dinucleotide phosphate (NADPH) oxidases (Nox), including the prototypic Nox2 homolog-based NADPH oxidase, as well as other Noxes, such as Nox1 and Nox4. Nox-derived ROS is important in regulating endothelial function and vascular tone. Oxidative stress is implicated in endothelial dysfunction, inflammation, hypertrophy, apoptosis, migration, fibrosis, angiogenesis and rarefaction, important processes involved in vascular remodeling in hypertension. Despite a plethora of data implicating oxidative stress as a causative factor in experimental hypertension, findings in human hypertension are less conclusive. This review highlights the importance of ROS in vascular biology and focuses on the potential role of oxidative stress in human hypertension.

Effects of aerobic exercise and resistance training on lipid profiles and inflammation status in patients on maintenance hemodialysis

Physical function limitation is a common disorder in chronic hemodialysis (HD) patients, relating to increased morbidity and mortality. The aim of this study was to determine the effects of aerobic and resistance trainings on blood lipids and inflammation status in HD patients. Out of 30 volunteer males who had been undergoing conventional maintenance HD within an HD unit in Tehran, 21 subjects were enrolled. They were randomly assigned into aerobic exercise group - resistance training group undergoing an 8-week intradialytic exercise program (three times/week) and control group (n = 7, each). Training program consisted of 10-30 min stationary cycling at an intensity of 12-16 out of 20 at the rate of perceived exertion (RPE) of Borg scale in aerobic group and using ankle weights for knee extension, hip abduction and flexions at an intensity of 15-17 out of 20 at the RPE of Borg scale in resistance group. Fasting blood samples for serum biochemistry were drawn at baseline and 8 weeks. The age, HD duration, and physical activity score were 51.6±18.9yrs; 25.1±13.9 mo, and 19.2±7.6, respectively. Diabetes mellitus (43%), hypertension (28%), and obstructive uropathy (14%) were the most common underlying diseases. Aerobic and resistance exercises were correlated with serum creatinine (P< 0.0001 and P<0.001) and hs-CRP levels (P=0.005 and P=0.036) reduction so that aerobic exercise induced more reduction. These exercises had no influence on weight, Kt/V values, serum urea, albumin, hemoglobin, and lipid levels (P>0.05). Both intradialytic aerobic and resistance exercises showed beneficial effects on inflammation status without any influences on serum lipid levels probably due to short duration of the study which was not accompanied with body weight changes. Solute removal had no change during exercise programs. There is a need for more investigation on the role of exercise in HD patients.