Plasma sulfur amino acids in relation to cardiovascular disease, nutritional status, and diabetes mellitus in patients with chronic renal failure at start of dialysis therapy

Association between homocysteinemia and mortality in CKD: A propensity-score matched analysis using NHANES-National Death Index

Hyperhomocysteinemia (HHcy) is considered a risk factor for cardiovascular disease (CVD), including chronic kidney disease (CKD). In this study, we investigated the association between levels of serum homocysteine (Hcy) and mortality, inferred from the presence of CKD. Our study included data of 9895 participants from the 1999 to 2016 National Health and Nutrition Examination Surveys (NHANES). Multivariable-adjusted Cox proportional hazard models using propensity-score, were used to examine dose-response associations between Hcy level and mortality. A total of 9895 participants, 1025 (10.3%) participants were diagnosed with CKD. In a multivariate Cox regression analysis including all participants, Hcy level was significantly associated with all-cause mortality in the nonCKD group, compared to the 1st quartile in the fully adjusted model (2nd quartile: hazard ratio (HR) 1.75, 95% confidence interval (CI) 1.348-2.274, P < .001; 3rd quartile: HR 2.22, 95% CI 1.726-2.855, P < .001; 4th quartile: HR 3.77, 95% CI 2.952-4.830, P < .001). However, this finding was not observed in the CKD group. The observed pattern was similar after propensity score matching. In the nonCKD group, overall mortality increased in proportion to Hcy concentration (2nd quartile: HR 2.19, 95% CI 1.299-3.709, P = .003; 3rd quartile: HR 2.60, 95% CI 1.570-4.332, P < .001; 4th quartile: HR 3.72, 95% CI 2.254-6.139, P < .001). However, the risk of all-cause mortality according to the quartile of Hcy level, did not increase in the CKD group. This study found a correlation between the Hcy level and mortality rate only in the nonCKD group. These altered risk factor patterns may be attributed to protein-energy wasting or chronic inflammation status, that is accompanied by CKD.

Copolymer-Based Fluorescence Nanosensor for In Situ Imaging of Homocysteine in the Liver and Kidney of Diabetic Mice

Homocysteine (Hcy) is one of the important biomarkers of clinical diagnosis, which is closely related to the occurrence and development of many diseases. Current analysis methods have difficulties in detecting Hcy in cells and living organisms. As a powerful technique, fluorescence methods combined the laser confocal imaging technology can achieve real-time visual tracking in cells and in vivo. Herein, we establish a conjugated copolymer-based fluorescence nanosensor (DPA-PFNP-Cu(II)) using the connected 2,7-dibromofluorene and 4,7-bis (2-bromothiophen-5-yl)-2-1-3-benzothiadiazole as the main chain. The competitive coordination between Hcy and Cu(II) allows the fluorescence of the polymer off to on. Finally, the nanosensor is applied for in situ imaging of Hcy levels in the kidney and liver of diabetic mice and is found that Hcy levels were positively correlated with the degree of diabetes. Notably, the depth of tissue penetration of the nanosensor enables Hcy detection of the liver and kidney through in vivo imaging without damage. Two-photon imaging and in vivo imaging achieve consistent results, which correct each other, improving the accuracy of the test result. The present works provide a new imaging technique for studying the occurrence and development of diabetes and screening of new drugs for treatment at the living level.

Sparse reduced-rank regression for integrating omics data

BACKGROUND

The problem of assessing associations between multiple omics data including genomics and metabolomics data to identify biomarkers potentially predictive of complex diseases has garnered considerable research interest nowadays. A popular epidemiology approach is to consider an association of each of the predictors with each of the response using a univariate linear regression model, and to select predictors that meet a priori specified significance level. Although this approach is simple and intuitive, it tends to require larger sample size which is costly. It also assumes variables for each data type are independent, and thus ignores correlations that exist between variables both within each data type and across the data types.

RESULTS

We consider a multivariate linear regression model that relates multiple predictors with multiple responses, and to identify multiple relevant predictors that are simultaneously associated with the responses. We assume the coefficient matrix of the responses on the predictors is both row-sparse and of low-rank, and propose a group Dantzig type formulation to estimate the coefficient matrix.

CONCLUSION

Extensive simulations demonstrate the competitive performance of our proposed method when compared to existing methods in terms of estimation, prediction, and variable selection. We use the proposed method to integrate genomics and metabolomics data to identify genetic variants that are potentially predictive of atherosclerosis cardiovascular disease (ASCVD) beyond well-established risk factors. Our analysis shows some genetic variants that increase prediction of ASCVD beyond some well-established factors of ASCVD, and also suggest a potential utility of the identified genetic variants in explaining possible association between certain metabolites and ASCVD.

Assessing Plasma Total Homocysteine in Patients with End-Stage Renal Disease

Elevated plasma total homocysteine (tHcy) is a risk factor for cardiovascular disease; however, in light of several recent randomized trials, the issue of causality has been cast into doubt. Patients with end-stage renal disease are particularly interesting as they consistently have elevated tHcy and their leading causes of morbidity and mortality are related to cardiovascular disease. In the present article, we review the early evidence for the homocysteine theory of atherosclerosis, homocysteine metabolism, mechanisms of toxicity, and pertinent available clinical investigations. Where appropriate, the sparse evidence of homocysteine in peritoneal dialysis is reviewed. We conclude by addressing the difficulties associated with lowering plasma tHcy in patients with end-stage renal disease and suggest some novel methods for lowering tHcy in this resistant population. Finally, to address the issue of causality, we recommend that clinicians and scientists await the results of the FAVORIT trial before abandoning homocysteine as a modifiable risk factor for cardiovascular disease, as this study has recruited patients from a population with consistently elevated plasma tHcy who are known to respond to vitamin therapy.

Assessment of Serum Folic Acid and Homocysteine in Thalassemia Major Patients Before and After Folic Acid Supplement Cessation

BACKGROUND

Thalassemic patients have ineffective erythropoiesis. In recent treatment protocols, there are little data on folic acid supplementation for patients with thalassemia because it is supposed that regular blood transfusions prevent bone marrow hyperfunctioning.

OBJECTIVE

Investigators aimed to assess serum folic acid and homocysteine (Hcy) in thalassemia major patients before and after folic acid supplement cessation.

PATIENTS AND METHODS

This study was a before-after controlled clinical trial conducted in 17th Shahrivar Hospital, Rasht, North of Iran, during May to October 2016. The patients enrolled in this study had thalassemia major on regular blood transfusion and older than 2 years of age. They had at least a 6-month history of folic acid supplement consumption before enrollment in the study (1 mg/daily). Complete blood count, serum folic acid, and serum Hcy were measured before discontinuation of folic acid supplement. Then, patients did not receive folic acid for a month and after 1 month of folic acid cessation, the measurements were repeated. All data were entered in SPSS version 20.0 and analyzed.

RESULTS

Among the 40 patients in this study, 25 (62.5%) were female. The mean age of the participants was 21.39±11.17 years old. The mean of body mass index was 21.38±3.32 kg/m. Most of the participants had used folic acid supplement >5 years (29, 72.5%). The serum Hcy level was significantly increased (5.24±2.35 vs. 5.93±2.56; P=0.008) and serum folic acid level was decreased significantly (14.74±4.20 vs. 8.80±4.16; P<0.0001) from baseline.

CONCLUSIONS

Cessation of folic acid supplementations in beta thalassemia major patients can lead to a significant decrease in serum folic acid and increase in Hcy levels. According to our findings and efficacy of folic acid in patients with beta thalassemia major, it is recommended to use the supplementation in all patients.

Effect of Eicosapentaenoic acid (EPA) supplementation on cardiovascular markers in patients with type 2 diabetes mellitus: A randomized, double-blind, placebo-controlled trial

AIMS

Cardiovascular complications are one of main cause of increased mortality and morbidity among Diabetes Mellitus (DM) patients. Altered metabolism of sulphur amino acids in diabetes reflected as increases in concentration of methionine and cysteine/cystine in the blood which known as a markers of Cardiovascular Diseases (CVD). The aim of present study was to determine the effect of Eicosapentaenoic acid (EPA) supplementation on sulfhydryl amino acids and Atherogenic Index of Plasma (AIP) in patients with type 2 DM (T2DM).

METHOD

A randomized, double-blind, placebo-controlled clinical trial was performed in 36 control and patients with DM. The subjects were randomly assigned to obtain 2 g/d EPA (n = 18) or placebo (n = 18) for 8 weeks. Fasting serum level of Cystein and Methionine were measured using HPLC method and atherogenic index of plasma (AIP) as a proxy measure of atherosclerosis was computed.

RESULTS

Eight weeks supplementation with EPA led to significant reductions in Met (p < 0.002) and Cys (p < 0.001) compared with the placebo (p < 0.06). In addition, compared to placebo a significant reduction in AIP were seen after taking EPA (p < 0.04).

CONCLUSION

EPA supplementation in patients with T2DM for eight weeks had beneficial effects on Met, Cys and AIP, which may attribute to the prevention of vascular complications in the T2DM patients.

Cardiovascular Risk Markers in Hemodialysis Patients

Cardiovascular events are the main cause of death in hemodialysis patients. Nevertheless, acute myocardial infarction may be misdiagnosed in uremic patients, because typical markers have a high rate of false positivity. A recent two-year prospective study showed that predialytic high serum concentrations of troponin T and CK-MB mass were associated with high mortality, cardiac mortality, myocardial infarction and unstable angina (MACEs). We studied 16 uremic patients (13 M; 3 W) on standard HD and 6 patients (4 M; 2 W) on on-line HDF, who had been taking folic acid for at least three months. Patients who suffered from acute or chronic cardiac ischemic disease were excluded. Anthropometric parameters, pre and post-dialytic pH, HCO3 and electrolytes did not differ between the two groups. Kt/V and URR % were lower in conventional HD vs on-line HDF (p<0.04; p<0.04). ORR % was strongly elevated in on-line HDF compared with HD (p<0.005). In conventional HD, ORR % was directly correlated with Kt/V and URR% (r = 0.49, p<0.04; r = 0.48, p<0.04, respectively). Even in on-line HDF ORR % was directly correlated with Kt/V and URR % (r = 0.79, p<0.04; r = 0.76, p<0.05, respectively). Troponin I and CK-MB mass were not significantly different in pre vs post-dialysis, both in standard HD and on-line HDF. Nevertheless, in standard HD postdialytic troponin I correlated with serum sodium concentration (r = 0.93, p < 0.000), potassium (r = 0.67, p < 0.004) and serum chlorine (r = 0.92, p < 0.92, p < 0.000). CK-MB mass showed a correlation with serum chlorine (r = 0.49, p < 0.05). Postdialytic CK-MB mass correlated with serum potassium in on-line HDF (r = 0.83, p < 0.03). Our data suggest that hemodialytic treatments, both standard HD and on-line HDF, do not modify serum troponin I and CK-MB mass. Consequently, we can use these parameters for the diagnostic approach in acute or chronic ischemic heart disease in hemodialysis patients.

Dietary Intake of Proteins and Calories Is Inversely Associated With The Oxidation State of Plasma Thiols in End-Stage Renal Disease Patients

OBJECTIVES

Oxidative stress contributes to the pathogenesis of protein-energy wasting in maintenance hemodialysis (MHD) patients, but knowledge of specific effectors and mechanisms remains fragmented. Aim of the study was to define whether and how food intake is involved in the causal relationship between oxidative stress and protein-energy wasting.

METHODS

Seventy-one adult MHD patients and 24 healthy subjects (control) were studied cross-sectionally with analyses of diet record and of oxidative stress, as measured by a battery of plasma thiols including the protein sulfhydryl (-SH) group (PSH) levels (a marker of total protein-SH reducing capacity), the protein thiolation index (PTI, the ratio between disulfide, i.e., oxidized and reduced -SH groups in proteins), low molecular mass (LMM) thiols, LMM disulfides, and mixed LMM-protein disulfides. In addition, interleukin-6 (IL-6), albumin, C-reactive protein, and neutrophil gelatinase-associated lipocalin (NGAL) were measured as markers of inflammation.

RESULTS

The patients showed low energy (22.0 ± 8.4 kcal/kg/day) and adequate protein (1.0 ± 0.4 g/kg/day) intakes, high levels of cystine (CySS; patients vs.

CONTROL

113.5 [90.9-132.8] vs. 68.2 [56.2-75.7] μM), cysteinylated proteins (CySSP; 216.0 [182.8-254.0] vs. 163.5 [150.0-195.5] μM), and high PTI (0.76 [0.61-0.88] vs. 0.43 [0.40-0.54]; P < .001 in all comparisons). In patients, variation of CySSP was explained by a standard regression model (R = 0.775; P = .00001) that included significant contributions of protein intake (β = -0.361), NGAL (β = 0.387), age (β = 0.295), and albumin (β = 0.457). In the same model, variation of PTI (R = 0.624; P = .01) was explained by protein intake (β = -0.384) and age (β = 0.326) and NGAL (β = 0.311). However, when PSH was entered as dependent variable (R = 0.730; P = .0001), only serum albumin (β = 0.495) and age (β = -0.280), but not dietary intake or NGAL, contributed to the model.

CONCLUSIONS

In MHD, markers of thiol oxidation including CySSP and PTI show independent association with dietary intake and NGAL, whereas PSH, a marker of thiol-reducing capacity, did not associate with these same variables. The mechanism(s) responsible for inverse association between oxidative stress and food intake in MHD remain undefined.

Bioanalytical LC separation techniques for quantitative analysis of free amino acids in human plasma

The quantitative analysis of free amino acids in human plasma has become an important and essential analysis parameter in different areas of life sciences. Free amino acid concentrations in human plasma samples are generally determined by means of GC or LC after chemical derivatization followed by UV, fluorescent or MS detection of the amino acid derivatives. Derivatization of free amino acids is done either pre- or post-column, and the amino acid derivatives obtained posess improved chromatographic behavior, increased detection sensitivity and selectivity compared with non-derivatized free amino acids. This work gives an overview of different chemical derivatization methods applied and their liquid separation techniques in bioanalytical assays for quantitative free amino acid analysis in human plasma samples. Important plasma preparation procedures, pre- and post-column derivatization, and different LC separation techniques are presented.

Malnutrition–Inflammation–Atherosclerosis (MIA) Syndrome Components in Hemodialysis and Peritoneal Dialysis Patients

BACKGROUND

Malnutrition, inflammation, and atherosclerosis (MIA syndrome) are common in end-stage renal disease (ESRD) patients. Each component of MIA syndrome is the predictor of outcomes in ESRD patients. In this cross-sectional study, we aimed to compare both dialysis modalities for MIA syndrome components.

MATERIAL AND METHODS

Thirty hemodialysis (HD) (mean age 44 +/- 11 years, 14 male and 16 female, mean time on dialysis: 31.0 +/- 19.0 months) and 30 continuous ambulatory peritoneal dialysis (CAPD) patients (41 +/- 9 years, 12 male and 18 female, mean time on dialysis: 25.5 +/- 21.5 months) were included. In order to determine malnutrition in ESRD patients, serum albumin level and anthropometric measurements were used. For inflammation, serum C-reactive protein level, erythrocyte sedimentation rate, and fibrinogen levels were measured. Mean-carotid artery intima media thickness (m-CIMT), presence of carotid plaque and serum homocysteine level were used to determine atherosclerosis.

RESULTS

Five CAPD patients (16%) and one HD patient (3%) was hypoalbuminemic. HD and CAPD groups were similar for inflammation. Mean-CIMT and serum homocysteine level were higher in HD patients than CAPD patients. There was a positive correlation between homocysteine and m-CIMT.

CONCLUSION

Before choosing renal replacement therapy, malnutrition, inflammation, and atherosclerosis parameters must be investigated in ESRD patients. Hemodialysis seems to be more advantageous for malnutrition components than CAPD. Both dialysis modalities seem to be similar for inflammation, and CAPD modality has superiority for atherosclerosis. Before choosing the type of renal replacement therapy, assessment of MIA syndrome components could be useful for individualization of the decision on which dialytic modality is appropriate in ESRD patients.

Prevalence of methylenetetrahydrofolate gene (MTHFR) C677T polymorphism among chronic hemodialysis patients and its association with cardiovascular disease: a cross-sectional analysis

INTRODUCTION

Cardiovascular disease (CVD) remains the main cause of morbidity and mortality in end stage renal disease (ESDR) patients. A common C-T mutation at nucleotide position 677 (C677T) has been identified in the gene coding for methylenetetrahydrofolate reductase (MTHFR), which is involved in the remethylation of homocysteine (Hcy). The C677T mutation decreases MTHFR activity, tends to increase Hcy concentrations in individuals who are homozygous for the T/T genotype, and may predispose to CVD. Recent reports suggested that the T/T genotype may predispose type 2 diabetic and hypertensive patients to the development of progressive renal insufficiency. The aim of this cross-sectional study is to analyze the prevalence of the MTHFR C677T gene polymorphism among a group of chronic dialysis patients in comparison to age- and gender-matched controls. We also examined the possible association between CVD and MTHFR gene mutation in this group of patients.

PATIENTS AND METHODS

Fifty chronic hemodialysis patients were included in the study. They were 29 males and 21 females with a mean age of 41.57 +/- 11.76 years. Three patients (6%) were diabetic (type 2). Mean duration of dialysis was 6.4 +/- 3.2 years (range 1-15 years). CVD was defined as being present if there was a medical history of coronary artery disease, cerebrovascular stroke or transient ischemic attacks. MTHFR C677T gene polymorphism was analyzed by PCR in order to discriminate between homozygous (C/C and T/T) and heterozygous (C/T) genotypes. We also measured serum vitamin B(12), folate, total plasma Hcy (tHcy), lipid profile and serum albumin concentrations in the study group. Thirty healthy subjects (16 males and 14 females with mean age of 37.42 +/- 7.63 years) served as healthy controls.

RESULTS

Thirteen patients (26%) experienced at least one cardiovascular event: two (4%) had a history of ischemic cerebrovascular disease, 13 (26%) had coronary artery disease, and one patient (2%) had myocardial infarction. The C677T mutation of MTHFR was not found to be different in hemodialysis patients and healthy controls. Thirty dialysis patients (60%) and 19 healthy subjects (63.33%) had only the wild-type allele (C/C), 16 dialysis patients (32%) and nine healthy controls (30%) had one T allele (C/T), and four dialysis patients (8%) and two healthy controls (6.67%) had two copies (T/T) of the T allele. There were no differences between patients with the three different MTHFR genotypes (C/C, C/T, T/T) regarding cardiovascular events or cardiovascular risk factors. Age, gender, percentages of diabetic and hypertensive patients, serum folate, vitamin B(12), lipid profile, and tHcy levels were not significantly different between the three groups (P > 0.05). Hemodialysis patients with CVD were significantly older compared to those without CVD (P = 0.02). Diabetes status was significantly associated with cardiovascular events (P = 0.01).

CONCLUSIONS

In the dialysis population that we studied, MTHFR C677T gene polymorphism occurred in a pattern similar to that seen for age- and gender-matched healthy controls. No significant association was detected between the T/T genotype and CVD in dialysis patients. Plasma total homocysteine levels were not affected by mutation of the gene coding for MTHFR, and this may be explained by the normal serum folate and vitamin B(12) levels found in the study group.

5-methyltetrahydrofolate administration is associated with prolonged survival and reduced inflammation in ESRD patients

BACKGROUND

Hemodialysis (HD) patients have a greatly increased risk of cardiovascular morbidity and mortality. For this reason, attempts are often made to normalize hyperhomocysteinemia. This randomized prospective study sought to determine which risk factors are predictors of mortality and whether high doses of folates or 5-methyltetrahydrofolate (5-MTHF) could improve hyperhomocysteinemia and survival in HD patients.

METHODS

341 patients were divided into two groups: group A was treated with 50 mg i.v. 5-MTHF, and group B was treated with 5 mg/day oral folic acid. Both groups received i.v. vitamin B(6) and B(12). By dividing patients into C-reactive protein (CRP) quartiles, group A had the highest survival for CRP <12 mg/l, whereas no survival difference was found for group B. CRP was the only predictive risk factor for death (RR 1.17, range 1.04-1.30, p = 0.02). Dialysis age, hyperhomocysteinemia, methylenetetrahydrofolate reductase polymorphism, albumin, lipoprotein (a) and folate did not influence mortality risk. Survival in group A was higher than that in group B, namely 36.2 +/- 20.9 vs. 26.1 +/- 22.2 months (p = 0.003).

RESULTS

Our results suggest that CRP, but not hyperhomocysteinemia, is the main risk factor for mortality in HD patients receiving vitamin supplements. Intravenous 5-MTHF seems to improve survival in HD patients independent from homocysteine lowering.

Red blood cells as a physiological source of glutathione for extracellular fluids

Plasma low molecular mass thiols are represented by glutathione, cysteine, cysteinylglycine and homocysteine. The physiological mechanisms responsible for maintaining the homeostasis of these compounds in the intracellular and extracellular spaces have not been fully clarified. Erythrocytes possess the enzymatic machinery to synthesize glutathione and an efflux of glutathione disulfide and glutathione conjugates from erythrocytes under various conditions occurs. In this study, the property of red blood cells (RBCs) to export low molecular mass thiols has been assessed. Plasma concentration of low molecular mass thiols has been measured in healthy volunteers by HPLC and a significant correlation with RBC number has been observed for glutathione and cysteinylglycine. A sustained export of reduced glutathione has been observed (about 21 nmol/h/ml RBCs) together with a lower, though significant, efflux of both cysteine and homocysteine. These results suggest that erythrocytes can contribute significantly to the extracellular pool of glutathione (GSH), thus cooperating with liver and other tissues to the dynamics of inter-organ GSH metabolism.

A simple and selective method for the measurement of leucine and isoleucine from plasma using electrospray ionization tandem mass spectrometry

An analytical method was developed for the rapid and accurate quantification of leucine (LEU) and isoleucine (ILE) from plasma using electrospray ionization tandem mass spectrometry (ESI-MS/MS). The two isomeric amino acids were selectively detected using fragment ions unique to each compound. As a result, the need for chromatographic separation was avoided allowing for faster analysis (3 min). The possibility of any considerable interference between the two transitions was closely monitored, with no significant interference being observed. The presence of interfering compounds in plasma was also evaluated and found to minimal. The method was evaluated based upon linearity, with r2>or=0.995 for both compounds, and accuracy, with no more than 8% deviation from the theoretical value.

Epidemiology of dialysis patients and heart failure patients

The epidemiology of maintenance dialysis patients and heart failure patients has striking similarities. Both groups have a high prevalence of comorbid conditions, a high hospitalization rate, a low self-reported quality of life, and an excessively high mortality risk, mostly because of cardiovascular causes. Observational studies in both dialysis and heart failure patients have indicated the lack of a significant association between the traditional cardiovascular risk factors and mortality, or the existence of a paradoxic or reverse association, in that obesity, hypercholesterolemia, and hypertension appear to confer survival advantages. The time discrepancy between the 2 sets of risk factors, that is, overnutrition (long-term killer) versus undernutrition (short-term killer) may explain the overwhelming role of malnutrition, inflammation, and cachexia in causing the reverse epidemiology, which may exist in more than 20 million Americans. We have reviewed the opposing views about the concept of reverse epidemiology in dialysis and heart failure patients, the recent Die Deutsche Diabetes Dialyze study findings, and the possible role of racial disparities. Contradictory findings on hyperhomocysteinemia in dialysis patients are reviewed in greater details as a possible example of publication bias. Additional findings related to intravenous iron and serum ferritin, calcium, and leptin levels in dialysis patients may enhance our understanding of the new paradigm. The association between obesity and increased death risk in kidney transplanted patients is reviewed as an example of the reversal of reverse epidemiology. Studying the epidemiology of dialysis patients as the archetypical population with such paradoxic associations may lead to the development of population-specific guidelines and treatment strategies beyond the current Framingham cardiovascular risk factor paradigm.

Homocysteine and its determinants in nondialyzed chronic kidney disease patients

This cross-sectional study aimed to investigate the prevalence of hyperhomocysteinemia, the determinants of plasma total homocysteine concentrations, and the relationship of total homocysteine with nutritional parameters in a sample of patients with chronic kidney disease (CKD) and not yet on dialysis. The study was done with outpatients from the Nephrology Division of the Federal University of São Paulo and Oswaldo Ramos Foundation. Sixty-six patients with CKD (70% male; age 58.6+/-15.6 years [mean+/-standard deviation]) with moderate to severe renal impairment (creatinine clearance=29.8+/-14.3 mL/min [0.5+/-0.24 mL/sec]), clinically stable, and older than 18 years were included. A group of 20 healthy subjects from the clinic staff was also studied for reference values for plasma homocysteine, folate, and vitamin B-12 concentration. Fasting blood samples were collected to determine plasma total homocysteine, folate, vitamin B-12, and creatinine. To calculate creatinine clearance, a 24-hour urine collection sample was obtained. The assessment of nutritional status included anthropometric parameters. Pearson correlation, Mann-Whitney test, and multiple linear regression analysis were used for statistical analyses. The main results showed that the concentration of total homocysteine in the patients was significantly increased compared with the healthy subjects (3.4+/-1.7 vs 1.41+/-0.42 mg/L [25.4+/-12.2 vs 10.4+/-3.1 micromol/L]; P<0.001). Plasma folate and plasma vitamin B-12 were in the normal range and did not differ between patients and healthy individuals. A high prevalence of hyperhomocysteinemia (total homocysteine >1.89 mg/L [14 micromol/L]) was found in the patients (89%). Plasma total homocysteine did not correlate with any of the nutritional parameters studied and did not differ between patients in terms of whether they were using or not using folic acid supplementation (3.07+/-1.09 vs 3.55+/-1.78 mg/L [22.7+/-8.1 vs 26.3+/-13.2 micromol/L]; P=0.47), although plasma folate was significantly higher in the supplemented group (12.6+/-3.0 vs 8.0+/-3.6 ng/mL [28.5+/-6.8 nmol/L vs 18.1+/-8.2 nmol/L]; P<0.001). According to the multiple regression analysis, the determinants of total homocysteine were only plasma folate, plasma vitamin B-12, and creatinine clearance (r2=0.20). In conclusion, a high prevalence of hyperhomocysteinemia was found in our sample of nondialyzed patients with CKD. The determinants of total homocysteine levels were plasma folate, plasma vitamin B-12, and creatinine clearance. No association between nutritional parameters and total homocysteine was observed.

Nutritional Parameters and Mortality in Incident Hemodialysis Patients

OBJECTIVE

To evaluate the impact of nutritional parameters at the time of initiation of hemodialysis (HD) on mortality.

DESIGN

Retrospective study.

SETTING

Dialysis Unit of the Federal University of Sao Paulo, Oswaldo Ramos Foundation.

PATIENTS

Three hundred forty-four incident HD patients (60.5% male, 26% diabetic) with the first nutritional evaluation performed before completing 3 months of onset of HD were included.

METHODS

The study consisted of baseline measurements of several nutritional parameters (triceps skinfold thickness [TSF], midarm muscle circumference [MAMC], body mass index [BMI], serum albumin, serum creatinine, and protein and energy intake assessed by 3-day food diary) and records of outcome (death) over a period of 10 years.

RESULTS

Muscle and/or fat depletion was observed in 51% of the studied patients, according to the percent standard of MAMC and TSF, respectively. Presence of diabetes, age over 60 years, serum albumin < 3.5 g/dL, MAMC adequacy < 90%, protein intake < 1.0 g/kg/d, and energy intake < 25 kcal/kg/d were associated with worse survival. When patients were analyzed according to tertiles of dialysis vintage, BMI > or = 25 (calculated as kg/m2) had a negative impact on survival only in the highest tertile (> 2.45 years). Patients with BMI < 25 and MAMC adequacy > or = 90% showed the best survival over the study period, and those with BMI > or = 25 but MAMC adequacy < 90% had the worst survival (P = .004). In the multivariate survival analysis adjusting for diabetes, advanced age, and hypoalbuminemia, the reduced MAMC (P = .008) and the low energy intake (P = .03) were independent predictors of death in incident HD patients.

CONCLUSIONS

Reduced MAMC and low energy intake at the beginning of chronic dialysis are risk factors for mortality. A negative effect of high BMI on survival was associated with reduced MAMC and longer dialysis vintage.

Homocysteine and vascular disease in diabetes: a double hit?

Cardiovascular disease is a major problem in diabetes, and risk factors presumably unrelated to diabetes, such as hyperhomocysteinaemia, may be related to the development of cardiovascular complications in diabetic individuals. Plasma homocysteine levels are usually normal in diabetes, although both lower and higher levels have been reported. Homocysteine levels in diabetes are modulated by hyperfiltration and renal dysfunction, as well as low folate status. Insulin resistance does not appear to be a major determinant of plasma homocysteine level. Hyperhomocysteinaemia has been associated with microalbuminuria and retinopathy in type 1 and type 2 diabetes. In patients with type 2 diabetes, plasma homocysteine concentration is a significant predictor of cardiovascular events and death. This relation seems to be stronger in subjects with diabetes than without. The underlying pathophysiological mechanism of this increased vascular risk remains unexplained, but may be related to worsening of endothelial dysfunction and/or structural vessel properties induced by oxidative stress. Because homocysteine and diabetes have apparent synergistic detrimental vascular effects, patients with diabetes are candidates for screening and treatment with folic acid until the results of ongoing clinical trials are available.

Hiperhomocisteinemia na insuficiência renal crônica

A homocisteína é um aminoácido sulfurado proveniente do metabolismo da metionina, cujo acúmulo anormal no plasma é um fator de risco para doenças vasculares, tanto na população em geral como nos pacientes com insuficiência renal crônica. Nestes, a prevalência de indivíduos com hiperhomocisteinemia é bastante elevada, mesmo na fase não dialítica da doença, em que a função renal está diminuída, mas ainda não é necessário tratamento dialítico. O principal fator que parece estar implicado na elevação dos níveis de homocisteína nestes pacientes com insuficiência renal crônica é a perda da massa renal, já que esta exerce uma importante função no metabolismo desse aminoácido. O tratamento da hiperhomocisteinemia na população em geral consiste na suplementação com as vitaminas envolvidas no seu metabolismo (folato, B6 e B12). Porém, em pacientes com insuficiência renal crônica, este tratamento não é completamente eficaz, pois apesar de promover a redução dos níveis de homocisteína, não alcança a normalização dos mesmos na maioria dos pacientes. Este estudo compreende uma revisão da etiologia da hiperhomocisteinemia na insuficiência renal crônica, sua relação com as doenças vasculares, seus principais determinantes e as formas de tratamento.

Creatine supplementation does not decrease total plasma homocysteine in chronic hemodialysis patients

BACKGROUND

Hyperhomocysteinemia is present in the majority of chronic hemodialysis patients. Treatment with folic acid, vitamin B12, and vitamin B6 cannot fully normalize plasma homocysteine concentrations (tHcy). Previously we have demonstrated the tHcy-lowering effect of creatine supplementation in an animal model of uremia (Kidney Int 64:1331-1337, 2003). The present study investigates the effects of creatine supplementation on tHcy in a vitamin-repleted chronic hemodialysis population.

METHODS

Forty-five hemodialysis patients receiving folic acid and vitamin B6 and B12 were included. Patients were treated with creatine (2 g/day) or placebo during 2 treatment periods of 4 weeks, separated by a washout of 4 weeks. Plasma tHcy, creatine, Kt/V(urea), folic acid, vitamin B12, and routine biochemistry were determined, as well as the prognostic inflammatory and nutritional index.

RESULTS

All patients had elevated tHcy concentrations (21.2 +/- 5.6 micromol/L). Creatine treatment resulted in increased plasma and red blood cell creatine levels, documenting uptake of creatine. Creatine did not affect tHcy concentrations. There was no relationship between plasma creatine concentrations and tHcy concentrations. No changes in body weight, routine biochemistry, nutritional status, folic acid, or vitamin B12 were observed during the study.

CONCLUSION

Creatine supplementation at a rate of 2 g/day does not further decrease tHcy concentrations in chronic dialysis patients already treated with high dose folic acid, vitamin B6, and B12 supplementation.

Serum concentrations of asymmetric (ADMA) and symmetric (SDMA) dimethylarginine in patients with chronic kidney diseases

BACKGROUND

NO synthesis is inhibited by the dimethylarginine (DMA) ADMA, which accumulates, similar to SDMA, in the plasma of patients suffering from chronic renal failure (CRF). ADMA and possibly SDMA contribute to hypertension and atherosclerosis in patients with chronic renal disease: ADMA inhibits directly eNOS, whereas SDMA competes with the NO precursor arginine for uptake into the cells.

METHODS

In 26 control persons and 221 patients with kidney diseases of different stage as were CRF, end stage renal disease (ESRD), and patients after renal transplantation (RT), the plasma concentrations of ADMA (c(ADMA)), SDMA (c(SDMA)) and 20 endogenous amino acids (AA) were measured by HPLC and correlated to blood pressure, cardiac events, endothelial dysfunction, and diabetes mellitus.

RESULTS

Both ADMA (1.04+/-0.04 vs. 0.66+/-0.04 microM) and SDMA (2.69+/-0.12 vs. 0.49+/-0.03 microM) were significantly (p<0.001) elevated in all patients compared to healthy controls, whereas arginine concentration (51.4+/-2.3 vs. 76.0+/-5.2 microM) was decreased in dependence on the degree of kidney disease. In RT patients, SDMA levels were significantly decreased, but c(ADMA) remained enhanced. A strong correlation was found between SDMA and both serum urea and creatinine in CRF and RT patients. A linear correlation was found between ADMA and cholesterol concentrations in RT patients. Hypertension in CRF was accompanied by a further increase in the concentration of DMAs. There was no relation between DMAs and the occurrence of peripheral arterial occlusive disease or cerebrovascular diseases. In patients with cardiac diseases, c(SDMA) was additionally increased only in the CRF group.

CONCLUSIONS

In patients with chronic kidney disease, c(ADMA) and c(SDMA) are significantly increased but cardiovascular diseases are evidently not correlated to changes in DMA concentrations in this group of patients.

Nitric oxide, S-nitrosothiols and hemoglobin: is methodology the key?

Two main hypotheses describe the role of hemoglobin in the regulation of nitric oxide (NO) bioavailability. It has been suggested that hemoglobin interacts with circulating NO, forming Fe-nitrosyl hemoglobin and then S-nitrosothiols, which deliver NO extracellularly by an allosterically regulated mechanism. Alternatively, the existence of diffusional barriers that protect NO from hemoglobin-mediated degradation has been proposed. The reliability of each model in vivo is supported by the detection of physiological hematic levels of S-nitrosohemoglobin. However, the measured concentrations of S-nitrosohemoglobin are largely divergent between the two models. Moreover, recent reports suggest that circulating levels of S-nitrosohemoglobin in human blood could be significantly lower than assessed previously. We suggest that solving the methodological controversies that make the field of NO research a 'minefield', even for skilled analysts, is fundamental to understanding the role of S-nitrosothiols in the vasculature.

Increasing hematocrit reduces early posttransplant cardiovascular risk in diabetic transplant recipients1

BACKGROUND

Cardiovascular disease remains epidemic in transplant recipients, despite aggressive treatment of cardiovascular risk factors. Thus, novel risk factors could play a role in the genesis of cardiovascular events in this population.

METHODS

We evaluated the impact of early posttransplant anemia on cardiovascular events. We examined rolling average hematocrit values at 30-day intervals and determined the effect of increasing hematocrit on the risk for cardiovascular (CV) events in a single-center population of 404 type 1 diabetic end-stage renal disease patients who underwent either cadaveric kidney transplantation alone or simultaneous pancreas-kidney transplantation.

RESULTS

Greater than 60% of the individuals in the study cohort had hematocrit less than or equal to 30% at least once during the first 30 days posttransplant. Forty-two individuals (10.4% of the study population) had at least one 30-day rolling hematocrit less than or equal to 30% and a CV event (myocardial infarction, CV death, angina, congestive heart failure) during the first 26 weeks of the posttransplant course. Increasing hematocrit (>30%) led to a reduction in the risk ratio (RR) for a CV event compared with hematocrit less than or equal to 30% (RR, 0.237; P=0.015). The association between anemia and CV events remained statistically significant in a multivariate analysis (RR, 0.65; P=0.022) that also included age and a history of pretransplant ischemic heart disease.

CONCLUSIONS

These data suggest that anemia is an important risk factor for early posttransplant CV events in a high-risk population. Prospective studies of anemia management therapy in this setting are warranted to determine whether this will reduce early posttransplant CV risk.

Hyperhomocysteinemia and its relationship to cardiovascular disease in ESRD: influence of hypoalbuminemia, malnutrition, inflammation, and diabetes mellitus

BACKGROUND

In the general population, a mildly elevated plasma total homocysteine (tHcy) level is an independent and graded risk factor for cardiovascular disease (CVD). In patients with end-stage renal disease (ESRD), CVD is highly prevalent and a major cause of premature mortality, and plasma tHcy levels are as much as three to four times greater than in the general population. Several other risk factors, such as diabetes mellitus (DM), inflammation, and malnutrition, also are prevalent and contribute to CVD in patients with ESRD, and there are strong associations between inflammation, malnutrition, and hypoalbuminemia in these patients. Several investigations in patients with ESRD have shown the important role of vitamin status for plasma tHcy, but little attention has been given to the influence of nutritional status. However, it is obvious that hypoalbuminemia is of interest because a substantial fraction of tHcy (>70%) is protein bound, mainly to albumin.

RESULTS

In studies of patients with ESRD in whom the prevalence of hyperhomocysteinemia was very high (>90%), tHcy level was strongly related to serum albumin level, and patients with malnutrition had lower levels of both tHcy and serum albumin than those with normal nutritional status. Furthermore, inflammation, DM, and CVD are associated with hypoalbuminemia and therefore a lower degree of hyperhomocysteinemia. In our studies, in different groups of patients with ESRD, we showed that greater tHcy levels were associated with lower CVD mortality. However, this apparently paradoxical association between lower CVD mortality and lower plasma tHcy levels (although still abnormally high) does not refute the concept that hyperhomocysteinemia is a risk factor for CVD because almost all patients may have had long-standing elevated plasma tHcy levels within a range that makes them prone to develop atherosclerosis. Instead, a potentially detrimental effect of hyperhomocysteinemia on CVD in patients with ESRD may be obscured by the influence of hypoalbuminemia, whatever the cause, because hypoalbuminemia and its causes are strong predictors of mortality.

CONCLUSION

Our findings imply that nutritional status and serum albumin level, as well as the presence of inflammation and DM, should be taken into consideration when evaluating tHcy as a risk factor for CVD in patients with ESRD.