Innovative Treatments to Counteract Endothelial Dysfunction in Chronic Kidney Disease Patients.

In chronic kidney disease (CKD) patients, several risk factors contribute to the development of endothelial dysfunction (ED), which can be described as an alteration in the cell structure or in the function of the endothelium. Among the well-known CKD-related risk factors capable of altering the production of endothelium-derived relaxing factors, we include asymmetric dimethylarginine increase, reduced dimethylarginine dimethylamine hydrolase enzyme activity, low-grade chronic systemic inflammation, hyperhomocysteinemia, oxidative stress, insulin resistance, alteration of calcium phosphorus metabolism, and early aging. In this review, we also examined the most important techniques useful for studying ED in humans, which are divided into indirect and direct methods. The direct study of coronary endothelial function is considered the gold standard technique to evaluate if ED is present. In addition to the discussion of the main pharmacological treatments useful to counteract ED in CKD patients (namely sodium-glucose cotransporter 2 inhibitors and mineralocorticoid receptor antagonist), we elucidate innovative non-pharmacological treatments that are successful in accompanying the pharmacological ones. Among them, the most important are the consumption of extra virgin olive oil with high intake of minor polar compounds, adherence to a plant-dominant, low-protein diet (LPD), an adaptive physical activity program and, finally, ketoanalogue administration in combination with the LPD or the very low-protein diet.

Effects of fenoldopam on renal blood flow in hypertensive chronic kidney disease.

BACKGROUND AND AIM: The synthetic drug fenoldopam mesylate (FM) may have a renoprotective role, and a "renal dose" of 0.1 µg/kg/min intravenous (IV) infusion of FM has been reported as able to increase renal blood flow without affecting systemic blood pressure. But conclusive data are still lacking. We aimed to investigate by color-Doppler ultrasonography the effects of IV administration of FM at this dosage in hypertensive chronic kidney disease (CKD) patients, and verify whether it may induce any systemic hemodynamic alteration. METHODS: In 60 hypertensive CKD patients, we measured by duplex Doppler ultrasonography, at baseline and during infusion of 0.1 µg/kg/min of FM, the systolic and diastolic flow velocity (sampled at the renal hilum, intermediate section and origin of both renal arteries) and the intra-parenchymal renal resistive index (RRI) sampled on interlobular arteries of both kidneys. Patients were divided into four subgroups (I-IV) according to classification of National Kidney Foundation Kidney Disease Outcomes Quality Initiative (NKF-DOQI). RESULTS: Infusion of 0.1 µg/kg/min FM significantly decreased the RRI (0.73 ± 0.05 vs. 0.65 ± 0.06; p < 0.0001) and increased the systolic and diastolic flow velocities in all renal artery tracts examined. No single episode of systemic hypotension was observed. CONCLUSIONS: Very low-dose FM may significantly increase renal blood flow and exert a renal protective effect in hypertensive CKD patients. Infusion of FM at such low dosage appears also to be quite safe, even in CKD and hypertensive patients.

Plasma and erythrocyte membrane phospholipids and fatty acids in Italian general population and hemodialysis patients.

BACKGROUND: Dyslipidemia and abnormal phospholipid metabolism are frequent in uremic patients and increase their risk of cardiovascular disease (CVD): ω-3 polyunsaturated fatty acids (PUFAs) may reduce this risk in the general population. In this study we compared the plasma and erythrocyte cell membrane composition of PUFAs in a group of Caucasian hemodialysis (HD) patients and in a control group of healthy subjects and evaluated the erythrocyte/cell membrane fatty acid ratio as a marker of the dietary intake of phospholipids. The relationship between ω-3 and ω-6 fatty acids and the possible differences in PUFAs concentrations were also investigated. METHODS AND RESULTS: After obtaining a fully informed consent, a total of ninety-nine HD patients and 160 non uremic control subjects from "Tor Vergata" University Hospital were enrolled into the study. None of them took antioxidant drugs or dietary supplements for at least 90 days prior to the observation. Blood samples were analysed by gas-chromatographic coupled to a mass spectrometric detector.The daily intake of total calories, proteins, lipids and carbohydrates is significantly lower in HD patients than in controls (p < 0.001). Most plasma and erythrocyte PUFA were also reduced significantly in HD patients (p < 0.001). CONCLUSIONS: Our results suggest that many classes of PUFAs are lacking in HD patients, due to the removal of nutrients during the dialysis and to persistent malnutrition. A dietary treatment addressed to increase plasma ω-3 PUFAs and to optimize ω-6/ω-3 ratio may exert a protective action and reduce the risk of CVD in HD patient.

Obesity-related metabolic syndrome: mechanisms of sympathetic overactivity.

The prevalence of the metabolic syndrome has increased worldwide over the past few years. Sympathetic nervous system overactivity is a key mechanism leading to hypertension in patients with the metabolic syndrome. Sympathetic activation can be triggered by reflex mechanisms as arterial baroreceptor impairment, by metabolic factors as insulin resistance, and by dysregulated adipokine production and secretion from visceral fat with a mainly permissive role of leptin and antagonist role of adiponectin. Chronic sympathetic nervous system overactivity contributes to a further decline of insulin sensitivity and creates a vicious circle that may contribute to the development of hypertension and of the metabolic syndrome and favor cardiovascular and kidney disease. Selective renal denervation is an emerging area of interest in the clinical management of obesity-related hypertension. This review focuses on current understanding of some mechanisms through which sympathetic overactivity may be interlaced to the metabolic syndrome, with particular regard to the role of insulin resistance and of some adipokines.

Atherosclerosis, dyslipidemia, and inflammation: the significant role of polyunsaturated Fatty acids.

Phospholipids play an essential role in cell membrane structure and function. The length and number of double bonds of fatty acids in membrane phospholipids are main determinants of fluidity, transport systems, activity of membrane-bound enzymes, and susceptibility to lipid peroxidation. The fatty acid profile of serum lipids, especially the phospholipids, reflects the fatty acid composition of cell membranes. Moreover, long-chain n-3 polyunsatured fatty acids decrease very-low-density lipoprotein assembly and secretion reducing triacylglycerol production. N-6 and n-3 polyunsatured fatty acids are the precursors of signalling molecules, termed "eicosanoids," which play an important role in the regulation of inflammation. Eicosanoids derived from n-6 polyunsatured fatty acids have proinflammatory actions, while eicosanoids derived from n-3 polyunsatured fatty acids have anti-inflammatory ones. Previous studies showed that inflammation contributes to both the onset and progression of atherosclerosis: actually, atherosclerosis is predominantly a chronic low-grade inflammatory disease of the vessel wall. Several studies suggested the relationship between long-chain n-3 polyunsaturated fatty acids and inflammation, showing that fatty acids may decrease endothelial activation and affect eicosanoid metabolism.

Erythrocyte glutathione transferase: a potential new biomarker in chronic kidney diseases which correlates with plasma homocysteine.

The erythrocyte glutathione S-transferase (e-GST) is a member of a superfamily of inducible enzymes involved in cell detoxification that shows an increased expression in chronic kidney disease (CKD) patients. We propose a new automated analysis procedure for e-GST activity that has been validated in 72 CKD patients and 62 maintenance hemodialysis patients (MHD). Regression analysis was carried out to assess association between e-GST activity data, main clinical variables, and plasma homocysteine (Hcy), a modified sulfur amino acid known as potential risk factor for cardiovascular disease that is increased above normal levels in more than 90% of the uremic patients. An increased e-GST activity was confirmed in MHD patients (N=62; 10.2±0.4 U/gHb) compared with healthy subjects (N=80; 5.8±0.4 U/gHb), and as an original finding, a significant increase of e-GST activity was observed in pre-dialysis CKD patients with a positive correlation with disease severity weighted according to the four stages of "Kidney Disease Outcomes Quality Initiative" classification (7.4±0.5, 8±1, 9.5±0.6, 12±1 U/gHb, respectively). No correlation was found between e-GST activity and hemoglobin, transferrin, blood iron and the markers of systemic inflammation and renal function such as alpha-1 acid glycoprotein and high-sensitive C-Reactive Protein, beta-2 microglobulin and the index of malnutrition-inflammation PINI, while a significant correlation was observed for the first time between plasma Hcy and e-GST activity (r2=0.64, P<0.0001) in MHD patients. Hcy, however, was not identified as an inhibitor of e-GST enzyme. The results in this study suggest the potential for automated e-GST analysis as a valuable tool to further explore phase II-related uremic toxicity in CKD and MHD patients.

Cytokine removal under hemodiafiltration with endogenous reinfusion in acute kidney injury secondary to angioimmunoblastic T-cell lymphoma: a case report.

Angioimmunoblastic T-cell lymphoma shows a high release of cytokines. Different blood purification techniques are employed to control hypercytokinemia. Here we investigated the effects of intermittent supra-hemodiafiltration with endogenous reinfusion on cytokine removal in a patient presenting with acute kidney injury. After the first day of chemotherapy for angioimmunoblastic T-cell lymphoma, a 78-year-old male patient developed acute kidney injury and systemic inflammatory response syndrome due to massive release of inflammatory cytokines. Three sessions of supra-hemodiafiltration were performed. Blood samples for evaluation of renal function and inflammatory mediators were collected at the beginning and the end of each dialytic session. A marked improvement of clinical state and renal function was associated to a significant reduction of inflammatory markers. Our results suggest that renal replacement therapy with supra-hemodiafiltration may remove a wide spectrum of inflammatory mediators and uremic toxins involved in acute kidney injury and systemic inflammatory response syndrome.

Vitamin E-related inhibition of monocyte 5-lipoxygenase and cardiovascular outcome in maintenance hemodialysis patients.

A daily supplement of vitamin E is recommended for the secondary prevention of cardiovascular events in end-stage renal disease patients on maintenance hemodialysis. Vitamin E has been entrusted with therapeutic properties against cardiovascular disease for more than 60 years. Several epidemiological studies and intervention trials have been performed with vitamin E, and some of them showed that it prevents atherosclerosis. For a long time, vitamin E was assumed to act by decreasing the oxidation of low-density lipoproteins, a key step in atherosclerosis initiation. However, at the cellular level vitamin E interferes with smooth muscle cell proliferation, platelet aggregation, monocyte adhesion, and oxidized low-density lipoproteins uptake and cytokine production, all reactions implied in the progression of atherosclerosis. Recent research points out that these effects may be not only the result of the antioxidant activity of vitamin E but also of its distinct molecular actions. These biological properties of vitamin E may allow to design better strategies for primary and secondary prevention of cardiovascular disease, with a potential exploitation of vitamin E supplements in primary and secondary prevention of major adverse cardiovascular events in all uremic patients. In this review, we also outline relevant patents on vitamin E and lipoxygenase inhibitors.

Chronic treatment with statins increases the availability of selenium in the antioxidant defence systems of hemodialysis patients.

PROJECT: Oxidative stress (OS) is enhanced in hemodialysis (HD) patients. Lipid peroxidation and oxidative damage to glycids, proteins and nucleic acids are the main consequences of OS and are associated with increased cardiovascular risk. Vitamin E and glutathione peroxidase (GSH-Px) represent the main antioxidant systems in human cells. Selenium (Se), bound to the active sites of GSH-Pxs, plays a critical role in this antioxidant defence system. Statins are widely used and extensively investigated in the prevention of cardiovascular disease, notably in high-risk subjects. Several studies show antioxidant effects of statins not related to their lipid-lowering action. Our study aimed to compare serum Se concentration in ESRD patients on maintenance HD and in homogeneous healthy subjects and to investigate whether chronic treatment with statins may interfere with serum Se concentration in HD patients. PROCEDURE: A total of 103 HD patients and 69 healthy subjects were enrolled; HD patients were divided into patients who were not treated with statins (group A) and patients who assumed statins since 6 months at least (group B). Serum Se was determined by atomic absorption spectrometry. RESULTS: Serum Se was significantly lower in HD patients of group A compared with healthy subjects (81.65+/-19.66 Vs. 96.47+/-15.62 mcg/L, p<0.0040). However, in HD patients who assumed statins serum, Se was significantly higher than in HD patients who did not (111.83+/-18.82 vs. 81.65+/-19.66 mcg/L, p<0.0001). CONCLUSIONS: Our results suggest that in HD patients chronic treatment with statins is related to higher-serum Se concentration.

Acid-base balance and oxygen tension during dialysis in uremic patients with chronic obstructive pulmonary disease.

Recent reports on the effects of dialysis on acid-base balance and metabolic acidosis correction in end-stage renal disease (ESRD) patients with chronic obstructive pulmonary disease (COPD) are lacking. Here, we compared acid-base balance and blood gasses among 14 patients with established COPD (group A) and eight patients with normal respiratory function (group B). The two groups were homogeneous for age, time on dialysis, and male/female ratio. At the beginning of dialysis, acid-base balance and blood gasses were comparable between patients of groups A and B. A significant difference between groups was observed only in pCO(2) at 20 min, together with a delay in pH increase. Effective correction of acidosis was reported at the end of dialysis and is not significantly affected by COPD. Nevertheless, weight loss must be carefully monitored in these patients in order to prevent hyperhydration and worsening of respiratory function.

Arachidonate cascade, apoptosis, and vitamin E in peripheral blood mononuclear cells from hemodialysis patients.

BACKGROUND: Lipid peroxidation and oxidative stress are enhanced in peripheral blood mononuclear cells (PBMCs) from hemodialysis (HD) patients because of upregulation of the 5-lipoxygenase pathway of the arachidonate cascade. 5-Lipoxygenase activity is specifically inhibited by vitamin E both in vitro and in vivo regardless of its administration route. METHODS: The effect of arachidonate cascade enzymes and vitamin E on oxidative stress and apoptosis was investigated in PBMCs from 16 maintenance HD patients treated for at least 6 months with cuprammonium rayon membranes in a two-step crossover study: after a 4-week treatment with vitamin E-coated cuprammonium rayon membranes and again after a 4-week treatment with oral vitamin E. Control PBMCs were obtained from 16 healthy volunteers. RESULTS: Membrane lipoperoxidation, cellular luminescence, membrane fluidity, and leukotriene B(4) content were significantly greater in PBMCs from HD patients; lipoxygenase was upregulated, but prostaglandin H synthase (PHS) was not affected. Regardless of administration route, vitamin E partially controlled lipid peroxidation and oxidative stress through direct inhibition of 5-lipoxygenase. Cultured PBMCs from HD patients showed a significant increase in apoptotic cells compared with controls. Vitamin E markedly reduced cell luminescence, membrane fluidity, and apoptosis, whereas the PHS inhibitor indomethacin was ineffective. Similar results were obtained with control PBMCs induced to apoptosis by hydrogen peroxide. CONCLUSION: Reported data suggest that the 5-lipoxygenase branch of the arachidonate cascade is only responsible for membrane peroxidation, oxidative stress, and apoptosis of PBMCs of HD patients, and administration of vitamin E may be helpful in the control of oxidative stress-related disease in these subjects.