Cardiovascular disease on hemodialysis: Predictors of atherosclerosis and survival

The impacts of dietary antioxidants on cardiovascular events in hemodialysis patients: An update on the cellular and molecular mechanisms

Cardiovascular-related complications (CVCs) are the primary cause of death in patients undergoing hemodialysis (HD), accounting for greater than half of all deaths. Beyond traditional risk factors, chronic inflammation, extreme oxidative stress (OS), and endothelial dysfunction emerge as major contributors to accelerated CVCs in HD patients. Ample evidence shows that HD patients are constantly exposed to excessive OS, due to uremic toxins and pro-oxidant molecules that overwhelm the defense antioxidant mechanisms. The present study highlights the efficiency of natural antioxidant supplementation in managing HD-induced inflammation, OS, and consequently CVCs. Moreover, it discusses the underlying molecular mechanisms by which these antioxidants can decrease mitochondrial and endothelial dysfunction and ameliorate CVCs in HD patients. Given the complex nature of OS and its molecular pathways, the utilization of specific antioxidants as a polypharmacotherapy may be necessary for targeting each dysregulated signaling pathway and reducing the burden of CVCs.

Serum Folate and All-Cause Mortality is of Non-Linear Relationship Among Population with Chronic Kidney Disease: A Retrospective Cohort Study

AIM

A transition toward high serum folate concentrations has been noticed following the mandatory folate fortification. To explore this further, we studied the relationship between folate and health outcomes in population with chronic kidney disease (CKD).

METHODS

We retrospectively explored the relationships between serum folate and risk of all-cause death in this population. We analyzed data of 2142 subjects with CKD who participated in the National Health and Nutrition Examination Survey (NHANES) 1999-2006. Vital status was followed through December 31, 2006.

RESULTS

Cox regression was used to estimate hazard ratios (HRs) of mortality for individuals with serum folate in rest quintiles compared with individuals with the fourth quintile. After an average follow-up of 57.4 months with 157 deaths recorded, a reversed J-shaped association was revealed after conducting multivariable adjustment. The mortality rate in population with lower and higher folate levels were 8.29% and 12.67%, respectively, and the corresponding adjusted HRs were 2.41 (95% confidence interval, CI=1.32-4.40) and 2.10 (1.20-3.70). Kaplan-Meier curve showed survival benefits for the fourth quintile of serum folate as compared to the first and fifth quintile.

CONCLUSION

Serum folate concentrations may influence all-cause mortality in a non-linear pattern in the CKD population. It is reasonable to recommend periodic surveillance in the CKD population to maintain the serum folate concentration in an appropriate level.

Serum folate concentrations and all-cause, cardiovascular disease and cancer mortality: A cohort study based on 1999-2010 National Health and Nutrition Examination Survey (NHANES)

BACKGROUND

The relationships between serum folate levels and all-cause, cardiovascular disease (CVD), and cancer mortality are controversial.

METHODS

Utilizing 1999-2010 National Health and Nutrition Examination Survey (NHANES) and linked mortality data, we performed a cohort study with 28,845 participants and used Cox proportional hazards models and restricted cubic spline plots to elucidate the dose-response relationships between serum folate status and all-cause, CVD and cancer mortality.

RESULTS

During an average follow-up for 6.2years, 2821, 545 and 628 deaths were attributed to all-causes, CVD and cancer, respectively. Lower folate levels were associated with increased mortality, with hazards ratios of 1.30 (95% confidence interval [CI]: 1.16-1.47) for all-cause mortality, 1.33 (95% CI: 1.01-1.76) for CVD mortality, and 1.47 (95% CI: 1.16-1.87) for cancer mortality (first quartiles versus second quartiles). A reversed J-shaped pattern was apparently observed in males and younger participants when analyzing all-cause mortality and in younger participants when it comes to CVD and cancer mortality.

CONCLUSIONS

Lower folate levels, but not restricted to folate deficiency, are linked with higher rates of all-cause, CVD and cancer mortality. Adverse effects of excess folate as well as age and gender differences on mortality need further investigation.

Homocystein as a risk factor for developing complications in chronic renal failure

Aim:

Cardiovascular diseases are leading cause of death in patients with chronic renal failure. The aim of our study was to establish connection between levels of homocysteine and traditional and nontraditional risk factors for developing cardiovascular diseases in dialysis and pre dialysis patients.

Methods:

We included 33 pre dialysis (23 in stage three and 10 in stage four of chronic kidney disease) and 43 patients receiving hemodialysis longer than six months. Besides standard laboratory parameters, levels of homocysteine and blood pressure were measured in all patients. Glomerular filtration rate was measured in pre dialysis patients and dialysis quality parameters in dialysis patients.

Results:

Homocysteine levels were elevated in all patients (19±5.42mmol/l). The connection between homocysteine levels and other cardiovascular diseases risk factors was not established in pre dialysis patients. In patients treated with hemodialysis we found negative correlation between homocysteine levels and patients’ age (p<0.05) and positive correlation between homocysteine levels and length of dialysis (p<0.01) as well as between homocysteine and anemia parameters (erythrocytes, hemoglobin), (p<0.01). Homocysteine and LDL (and total cholesterol) were in negative correlation (p<0.01).

Conclusion:

Homocysteine, as one of nontraditional cardiovascular diseases risk factors, is elevated in all patients with chronic renal failure and it’s positive correlation with some other risk factors was found.

Identification of a cytoplasmic linker protein as a potential target for neovascularization

OBJECTIVE

Atherosclerosis and other cardiovascular diseases are serious threats to human health and become the leading cause of death in the world. Emerging evidence reveals that inhibition of plaque neovascularization could be an effective approach for the treatment of atherosclerosis. This study was conducted to identify cytoplasmic linker protein 170 as a potential target for cardiovascular diseases through modulation of neovascularization.

METHODS AND RESULTS

Immunofluorescence microscopy revealed that cytoplasmic linker protein 170 was ubiquitously expressed in mouse kidney, liver, lung, normal non-atherosclerotic aorta, and atherosclerotic aorta and was partly localized in the vascular endothelium. siRNAs were introduced to human umbilical vein endothelial cells (HUVECs) and the effect of knockdown was confirmed by Western blotting. Vascularization study was assessed with matrigel-based capillary assembly, branching, and in vivo matrigel plug assays. The data showed that siRNA-mediated knockdown of the cytoplasmic linker protein remarkably compromised the assembly and branching of capillary-like blood vessels and neovascularization in vivo. Cell motility and polarity properties were then analyzed using scratch wound repair, boyden chamber, and immunofluorescence assays, and the results revealed that the cytoplasmic linker protein was critical for the motility abilities of HUVECs through its actions on cell polarity.

CONCLUSION

Both in vitro and in vivo studies demonstrate the significance of the cytoplasmic linker protein for blood vessel formation. Mechanistic investigation reveals that its effect on neovascularization is orchestrated through its regulation of vascular endothelial cell polarity and motility. These findings provide the basis for exploring effective approaches to regulate neovascularization in cardiovascular diseases.

Reduced plasma zinc levels, lipid peroxidation, and inflammation biomarkers levels in hemodialysis patients: implications to cardiovascular mortality

Despite the fact that low plasma zinc (Zn) levels play important roles in the oxidative stress, the relationships between lipid peroxidation and inflammation biomarkers with low plasma Zn levels have not been investigated in chronic kidney disease (CKD) patients. The aim of this study was to evaluate the Zn plasma levels, electronegative LDL [LDL(-)] levels, and inflammation markers as predictors of cardiovascular (CV) mortality in hemodialysis (HD) patients. Forty-five HD patients (28 men, 54.2 ± 12.7 years, 62.2 ± 51.4 months on dialysis and BMI 24.3 ± 4.1 kg/m(2)) were studied and compared to 20 healthy individuals (9 men, 51.6 ± 15.6 years, BMI 25.2 ± 3.9 kg/m(2)) and followed for 24 months to investigate the risks for CV mortality. LDL(-) levels were measured by ELISA, plasma Zn levels by atomic absorption spectrophotometry, C-reactive protein (CRP) level by immunoturbidimetric method, and tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), monocyte chemotactic protein-1 (MCP-1), and plasminogen activator inhibitor-1 (PAI-1) levels by a multiplex assay kit. HD patients presented low plasma Zn levels (54.9 ± 16.1 μg/dL) and high-LDL(-) (0.18 ± 0.12 U/L) and TNF-α (5.5 ± 2.2 pg/mL) levels when compared to healthy subjects (78.8 ± 9.4μ g/dL, 0.10 ± 0.08U/L, 2.4 ± 1.1 pg/mL, respectively, p < 0.05). Zn plasma levels were negatively correlated to TNF-α (r = -0.49; p = 0.0001) and LDL(-) (r = -0.33; p = 0.008). During the 2 years, 24.4% of the patients died, all due to CV disease. Analysis by the Cox model showed that high CRP, TNF-α, IL-6 levels, and long duration of HD were significant predictors of mortality. In conclusion, reduced Zn levels were associated with lipid peroxidation and inflammation, and we confirm here in a Brazilian cohort of HD patients that inflammation markers are strong predictors of CV death.

Acute effects of hemodialysis on nitrite and nitrate: potential cardiovascular implications in dialysis patients

Cardiovascular mortality in dialysis patients remains a serious problem. It is 10 to 20 times higher than in the general population. No molecular mechanism has been proven to explain this increased mortality, although nitric oxide (NO) has been implicated. The objective of our study was to determine the extent of the removal of the NO congeners nitrite and nitrate from plasma and saliva by hemodialysis, as this might disrupt physiological NO bioactivity and help explain the health disparity in dialysis patients. Blood and saliva were collected at baseline from patients on dialysis and blood was collected as it exited the dialysis unit. Blood and saliva were again collected after 4-5h of dialysis. In the 27 patients on dialysis, baseline plasma nitrite and nitrate by HPLC were 0.21±0.03 and 67.25±14.68 μM, respectively. Blood immediately upon exit from the dialysis unit had 57% less nitrite (0.09±0.03 μM; P=0.0008) and 84% less nitrate (11.04 μM; P=0.0003). After 4-5h of dialysis, new steady-state plasma levels of nitrite and nitrate were significantly lower than baseline, 0.09±0.01 μM (P=0.0002) and 16.72±2.27 μM (P=0.001), respectively. Dialysis also resulted in a significant reduction in salivary nitrite (232.58±75.65 to 25.77±10.88 μM; P=0.01) and nitrate (500.36±154.89 to 95.08±24.64 μM; P=0.01). Chronic and persistent depletion of plasma and salivary nitrite and nitrate probably reduces NO bioavailability and may explain in part the increased cardiovascular mortality in the dialysis patient.

Neither oxidized nor anti-oxidized low-density lipoprotein level is associated with atherosclerosis or mortality in hemodialysis patients

It is anticipated that oxidized low-density lipoprotein (oxLDL) and anti-oxLDL are associated with atherosclerosis and mortality. However, data on this issue are controversial and limited. We aimed to investigate the effect of these two markers on the extent and progression of atherosclerosis and mortality in a group of hemodialysis patients. In this prospective observational study with a follow-up of 36 months, 124 hemodialysis patients were studied. Ninety-five patients underwent carotid intima media thickness (CA-IMT) measurement by B-Mode ultrasonography both at baseline and at the end of the study. oxLDL and anti-oxLDL were measured by enzyme-linked immunosorbent assay. The extent and progression of CA-IMT, along with overall and cardiovascular mortality, were assessed. The mean age at baseline was 54.0 ± 14.8 years, 57.3% male and 20% diabetic. The mean oxLDL and anti-oxLDL levels were 8.11 ± 3.16 mU/L and 1.30 ± 0.31, respectively. Baseline mean CA-IMT was 0.82 ± 0.20 mm. Fifteen patients died during a follow-up period of 28.5 ± 6.6 months, 11 from cardiovascular causes. Only oxLDL, not anti-oxLDL, was correlated with the extent of atherosclerosis at baseline. However, both had no role in the progression of atherosclerosis. Also, in unadjusted and adjusted models, both parameters were not associated with overall or cardiovascular mortality. Neither oxLDL nor anti-oxLDL level is associated with the progression of atherosclerosis or mortality in hemodialysis patients.

Vascular incompetence in dialysis patients--protein-bound uremic toxins and endothelial dysfunction

Patients with chronic kidney disease (CKD) have a much higher risk of cardiovascular diseases than the general population. Endothelial dysfunction, which participates in accelerated atherosclerosis, is a hallmark of CKD. Patients with CKD display impaired endothelium-dependent vasodilatation, elevated soluble biomarkers of endothelial dysfunction, and increased oxidative stress. They also present an imbalance between circulating endothelial populations reflecting endothelial injury (endothelial microparticles and circulating endothelial cells) and repair (endothelial progenitor cells). Endothelial damage induced by a uremic environment suggests an involvement of uremia-specific factors. Several uremic toxins, mostly protein-bound, have been shown to have specific endothelial toxicity: ADMA, homocysteine, AGEs, and more recently, p-cresyl sulfate and indoxyl sulfate. These toxins, all poorly removed by hemodialysis therapies, share mechanisms of endothelial toxicity: they promote pro-oxidant and pro-inflammatory response and inhibit endothelial repair. This article (i) reviews the evidence for endothelial dysfunction in CKD, (ii) specifies the involvement of protein-bound uremic toxins in this dysfunction, and (iii) discusses therapeutic strategies for lowering uremic toxin concentrations or for countering the effects of uremic toxins on the endothelium.

Determination of uremic solutes in biological fluids of chronic kidney disease patients by HPLC assay

During chronic kidney disease (CKD), solutes called uremic solutes, accumulate in blood and tissues of patients. We developed an HPLC method for the simultaneous determination of several uremic solutes of clinical interest in biological fluids: phenol (Pol), indole-3-acetic acid (3-IAA), p-cresol (p-C), indoxyl sulfate (3-INDS) and p-cresol sulfate (p-CS). These solutes were separated by ion-pairing HPLC using an isocratic flow and quantified with a fluorescence detection. The mean serum concentrations of 3-IAA, 3-INDS and p-CS were 2.12, 1.03 and 13.03 μM respectively in healthy subjects, 3.21, 17.45 and 73.47 μM in non hemodialyzed stage 3-5 CKD patients and 5.9, 81.04 and 120.54 μM in hemodialyzed patients (stage 5D). We found no Pol and no p-C in any population. The limits of quantification for 3-IAA, 3-INDS, and p-CS were 0.83, 0.72, and 3.2 μM respectively. The within-day CVs were between 1.23 and 3.12% for 3-IAA, 0.98 and 2% for 3-INDS, and 1.25 and 3.01% for p-CS. The between-day CVs were between 1.78 and 5.48% for 3-IAA, 1.45 and 4.54% for 3-INDS, and 1.19 and 6.36% for p-CS. This HPLC method permits the simultaneous and quick quantification of several uremic solutes for daily analysis of large numbers of samples.

An inter-laboratory validation of methods of lipid peroxidation measurement in UVA-treated human plasma samples

Lipid peroxidation products like malondialdehyde, 4-hydroxynonenal and F(2)-isoprostanes are widely used as markers of oxidative stress in vitro and in vivo. This study reports the results of a multi-laboratory validation study by COST Action B35 to assess inter-laboratory and intra-laboratory variation in the measurement of lipid peroxidation. Human plasma samples were exposed to UVA irradiation at different doses (0, 15 J, 20 J), encoded and shipped to 15 laboratories, where analyses of malondialdehyde, 4-hydroxynonenal and isoprostanes were conducted. The results demonstrate a low within-day-variation and a good correlation of results observed on two different days. However, high coefficients of variation were observed between the laboratories. Malondialdehyde determined by HPLC was found to be the most sensitive and reproducible lipid peroxidation product in plasma upon UVA treatment. It is concluded that measurement of malondialdehyde by HPLC has good analytical validity for inter-laboratory studies on lipid peroxidation in human EDTA-plasma samples, although it is acknowledged that this may not translate to biological validity.