Sustained reduction of hyperhomocysteinaemia with folic acid supplementation in predialysis patients

Effect of renal insufficiency and diabetes mellitus on in-hospital mortality after acute coronary syndromes treated with primary PCI. Results from the ALKK PCI Registry

BACKGROUND

It is known that patients with acute coronary syndromes (ACS) and diabetes mellitus (DM) are at higher risk for in-hospital adverse events. However, we hypothesized that the higher event rate is due to the patients' subgroup with renal failure (RF), a common sequel of DM.

METHODS AND RESULTS

We used data of the prospective ALKK-PCI registry including all consecutive percutaneous coronary interventions (PCI) for ACS of 48 hospitals between 2008 and 2013. We divided 69,651 patients in four groups according to their history of DM and RF (GFR < 60 ml/min). All-cause, in-hospital mortality of the following four groups: noDM/noRF, DM/noRF, DM/RF, RF/noDM, was: 3.5%, 6.6%, 21.9%, and 14.1% for STEMI and 1.5%, 2.1%, 7.2%, and 5.4% for NSTE-ACS. In a multivariate analysis we looked for independent mortality-predictors. Odds ratios with confidence intervals for the following variables: DM without RF, DM with RF, RF without DM were: 1.62 (1.37-1.90), 3.02 (2.43-3.76), and 2.13 (1.80-2.52) for STEMI and 1.20 (0.99-1.45), 2.72 (2.18-3.88), and 2.08 (1.69-2.56) for NSTE-ACS. We also calculated mortality in four groups (60-90, 45-60, 45-30, <30 ml/min) according to the estimated glomerular filtration rate (eGFR). Mortality rates were: 5.0%, 12.8%, 17.7%, and 31.5% for STEMI and 2.1%, 3.8%, 7.1%, and 12.0% for NSTE-ACS (p for trend <0.0001 for both).

CONCLUSIONS

In-hospital death after PCI in patients with ACS and DM is mainly observed in the subgroup with co-existing RF. In a multivariate analysis, DM without RF was a significant mortality-predictor in STEMI, but not in NSTE-ACS. RF, irrespective of co-existent DM, was a stronger predictor than DM alone for both ACS-types (OR > 3) and mortality increased with decreasing eGFR.

Design and statistical issues in the homocysteinemia in kidney and end stage renal disease (HOST) study

The Homocysteine Study (HOST) Veterans Affairs Cooperative Studies Program No. 453, is a prospective, randomized, two arm, double blind study of patients with end stage renal disease (ESRD) or advanced chronic kidney disease (ACKD, defined as an estimated creatinine clearance of 30 ml/min or less). Its primary objective is to determine whether administration of high doses of three vitamins, folic acid, vitamin B6 and vitamin B12, to lower the high plasma homocysteine levels, will reduce all cause mortality. The secondary objectives are to examine whether the treatment lowers the incidence of myocardial infarction, stroke, amputation of a lower extremity, a composite of death and the foregoing three events, the plasma homocysteine level, and, in ESRD patients undergoing hemodialysis, thrombosis of the vascular access. A unique feature of this trial is that after initial evaluation at enrollment and one return visit the follow up is exclusively by phone (or, if necessary, by mail). The subject is contacted every three months throughout the duration of the study from a central location. The study drug is shipped to the patient from a central location rather supplied locally. In a two year enrollment period, 2006 patients are to be enrolled. The duration of the observation period is four to six years. Data will be stored and analyzed at a coordinating center. The study design has the power to detect a reduction in all cause mortality rate of 17%. Issues related to the unique features of the design of this study are discussed.

Elevated serum homocysteine is a predictor of accelerated decline in renal function and chronic kidney disease: A historical prospective study

OBJECTIVE

To estimate the effect of elevated serum homocysteine level on renal function decline and on the incidence of chronic kidney disease (CKD) in the general population.

METHODS

A historical prospective study on 3602 subjects attending a screening center in Israel between the years 2000 and 2012. Only subjects with normal estimated glomerular filtration rate (eGFR) and without proteinuria were included. Subjects were divided to two groups according to mean total serum homocysteine level (≤ 15, >15μmol/l). Linear mixed effect model was used to estimate the annual eGRF decline in respect to homocysteine group. Cox proportional hazards models were used to estimate hazard ratios for CKD in the normal compared to the elevated homocysteine group.

RESULTS

Annual eGFR decline was 25% higher in subjects with elevated versus normal mean homocysteine level (0.90 ± 0.16 ml/min/1.37 m(2) vs. 0.72 ± 0.14 ml/min/1.37 m(2), p<0.001). In a median follow up of 7.75 years, 38 subjects developed CKD (1.05%). Elevated mean homocysteine level was highly associated with developing CKD (HR 4.85, 95% CI 2.48-9.49, p<0.001). In a multivariate analysis which adjusted for age, baseline kidney function, HDL cholesterol, BMI, vitamin B12 and folic acid levels, these relationships remained substantially unchanged.

CONCLUSIONS

Elevated mean serum homocysteine level is associated with an accelerated decline in renal function in both men and women, and is an independent risk factor for the development of CKD in the general population. Further prospective randomized clinical trials are needed to clarify whether the reduction in serum homocysteine concentrations will result in an improved renal prognosis.

Prevalence of hyperhomocysteinemia in healthy Indian doctors

Currently, hyperhomocysteinemia is a well-known risk factor for variety of vascular diseases. Prevalence of hyperhomocysteinemia increases with age. Hence, the present study was aimed to investigate the prevalence of hyperhomocysteinemia in healthy upper socio-economic class population in India. Total homocysteine (tHcy) concentration was determined in 1243 (906 men & 337 women) healthy Indian doctors with different age group. Using Third National Health and Nutrition Examination Survey (NHANES III) study criteria, the prevalence of hyperhomocysteinemia was 92.85% among men (>11.4 µmol/L) and 81.60% among women (>10.4 µmol/L). The prevalence of hyperhomocysteinemia was higher among men with mean tHcy concentration (21.96 ± 0.38 µmol/L) significantly higher (P<0.0001) than women (15.90 ± 0.39 µmol/L) (95% CI, 4.733- 7.376). Our study showed very high prevalence of hyperhomocysteinemia which may point to the future risk for various pathologies in the present subset of population. Further studies to look at the plasma levels of homocysteine lowering vitamins are warranted to prevent the future risk of vascular diseases.

Folic acid therapy and cardiovascular disease in ESRD or advanced chronic kidney disease: a meta-analysis

BACKGROUND AND OBJECTIVES

The efficacy of folic acid therapy to lower homocysteine (Hcy) levels in an effort to reduce cardiovascular disease (CVD) risk in patients with ESRD or advanced chronic kidney disease (ACKD; creatinine clearance, <30 ml/min) remains inconclusive. We conducted a meta-analysis of relevant randomized trials to further examine this issue.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

This meta-analysis included 3886 patients with ESRD/ACKD from seven qualified randomized trials using folic acid therapy and with CVD reported as one of the end points.

RESULTS

When pooling the seven trials, folic acid therapy reduced the risk of CVD by 15% (RR, 0.85; 95% CI, 0.76 to 0.96; P = 0.009). A greater beneficial effect was observed among those trials with a treatment duration >24 months (RR, 0.84; 95% CI, 0.72 to 0.98; P = 0.02), a decrease in Hcy level >20% (RR, 0.83; 95% CI, 0.73 to 0.95; P = 0.007), and no or partial folic acid fortification (RR, 0.80; 95% CI, 0.65 to 0.99; P = 0.04). The beneficial effect also was seen when Hcy levels decreased >20%, even in the presence of folic acid fortification (RR, 0.85; 95% CI, 0.73 to 0.99; P = 0.04). In the corresponding comparison groups, the estimated RRs were attenuated and insignificant.

CONCLUSIONS

Folic acid therapy can reduce CVD risk in patients with ESRD/ACKD by 15%. A greater beneficial effect was observed among those trials with no or partial folic acid fortification or a decrease in Hcy level >20% regardless of folic acid fortification.

Impact of impaired renal function and diabetes on long-term prognosis in patients undergoing primary angioplasty for acute coronary syndrome

OBJECTIVE

We sought to determine the effect of impaired renal function (IRF) and diabetes on the long-term outcome in patients undergoing primary angioplasty for acute coronary syndrome (ACS). Background Diabetes and IRF occur frequently in patients presenting with ACS. However, the prognostic importance of IRF in comparison with diabetes after primary angioplasty has not been specifically studied.

METHODS

A total of 742 patients with ACS treated by primary angioplasty were evaluated. Study endpoints were major adverse cardiac events (MACE), a composite of all-cause mortality, ACS, and target vessel revascularization (TVR).

RESULTS

During an average follow-up period of 6.8 years, we documented 13 cardiovascular deaths, 27 non-cardiovascular deaths, 12 incidents of ACS, and 165 incidences of TVR. Six-year rates of MACE were significantly higher in diabetics with IRF (47.6%), nondiabetics with IRF (36.4%), and diabetics without IRF (36.0%) than in nondiabetics without IRF (28.4%, Log-rank test: p=0.0057). Nondiabetics with IRF, diabetics without IRF, and diabetics with IRF had a relative hazard ratio for MACE of 1.63 (95% confidence interval (CI) 1.04 to 2.54, p=0.033), 1.47 (95% CI, 1.03 to 2.11; p=0.036), and 1.97 (95% CI, 1.12 to 3.48; p=0.019), respectively, compared with nondiabetics without IRF.

CONCLUSIONS

IRF has an important association with MACE after primary angioplasty in patients with ACS and may be nearly as predictive of long-term outcome as is diabetes.

No effect of B vitamins on ADMA levels in patients at increased cardiovascular risk

OBJECTIVE

Asymmetric dimethylarginine (ADMA) is a recently identified potent cardiovascular risk factor. ADMA levels are increased in hyperhomocysteinaemia and the metabolism of ADMA is linked with that of homocysteine in several ways. Treatment with B vitamins effectively reduces homocysteine levels, but studies investigating the effect on ADMA levels are scarce and show conflicting results. In this study we evaluated the effect of treatment with B vitamins on ADMA levels in two high cardiovascular risk populations.

METHODS

In study I, 110 siblings of patients with clinical atherosclerotic disease and postmethionine hyperhomocysteinaemia were treated with 5 mg of folic acid and 250 mg of pyridoxine or placebo, and were analysed after 1 year. In study II, 41 patients with type 2 diabetes and mild hyperhomocysteinaemia were analysed after 6 months treatment with 5 mg of folic acid or placebo.

RESULTS

A correlation between baseline homocysteine and ADMA levels was found, which was partly due to confounding by renal function. Homocysteine levels decreased by 43% in study I and by 28% in study II. In both studies, treatment with B vitamins had no effect at all on ADMA, arginine/ADMA ratio and SDMA levels. This result was confirmed in multiple linear regression analyses with adjustment for baseline values and gender.

CONCLUSIONS

Our studies indicate that B vitamins, despite causing a substantial reduction in plasma homocysteine levels, have no beneficial effect on ADMA levels.

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.

Folic acid 5 or 15 mg/d similarly reduces plasma homocysteine in patients with moderate-advanced chronic renal failure

BACKGROUND

Hyperhomocysteinaemia is an independent risk factor for cardiovascular disease with a remarkable prevalence in patients with chronic renal failure (CRF). Low doses of folic acid (FA) with or without vitamin B6 and B12 has been shown to effectively reduce plasma homocysteine (Hcy). The aim of this study was to compare the short-term effects of two different oral doses of FA (5 vs 15 mg/d) on plasma Hcy levels in subjects suffering from moderate-severe CRF.

METHODS

A double-blind, double-dummy, comparative, two-stage randomised study was performed. Seventeen patients aged 45-71 years, with glomerular filtration rates between 15.4-50 mL/min 1.73/m2 were randomly assigned to receive FA 5 mg/d (FA-5, n: 8) or FA 15 mg/d (FA-15, n: 9) for 30 days. At the end of this 30-day double-blind period, all the participants were placed on FA 5 mg/d (open period), for 5 additional months. Both groups were also supplemented with vitamins B1, B6 and B12 throughout the trial. Blood samples were drawn at 0, 15, 30, 90 and 180 days to assess Hcy, complete blood count (CBC) and sequential multichannel analysis (SMA). Chest X-ray and a 12-lead electrocardiogram (ECG) were also performed.

RESULTS

Plasma Hcy (mean +/- SEM) decreased from 27.9 +/- 1.4 (baseline) to 15.1 +/- 0.6, 13.3 +/- 0.9, 14.1 +/- 0.5 and 13.8 +/- 0.5 micromol/L (FA-5) and from 28.8 +/- 2.7 to 15.6 +/- 1.2, 14.4 +/- 1.3, 13.0 +/- 0.7 and 13.1 +/- 0.6 micromol/L (FA-15) at days 15, 30, 90 and 180, respectively. (P < 0.01 from day 15 to 180 vs baseline for both groups with no differences between them). Renal function remained stable throughout the entire period of the study in all but one patient in whom it deteriorated to pre-end stage disease. No adverse cardiovascular events developed during the trial.

CONCLUSION

Both folic acid doses induced a significant and similar decrease in plasma Hcy in subjects with moderate-severe chronic renal failure. The possible dose-related effect of this approach in reducing the risk of accelerated sclerotic vascular disease and cardiovascular events in this especially vulnerable population should be a matter of further investigation.

Atherosclerosis and Vascular Calcification in Chronic Renal Failure

Cardiovascular complications are a major clinical problem in patients with chronic kidney disease and end-stage renal failure; cardiac death accounts for approximately 40-50% of all deaths in these patients. Death from cardiovascular causes is up to 20 times more common in uremic patients than in the general population with the risk being even higher than in patients with diabetes mellitus. A high rate of myocardial infarction and excessive cardiac mortality have repeatedly been documented in patients with kidney disease and renal failure. Not only is the prevalence of myocardial infarction high, but also the case fatality rate is significantly higher in uremic patients with and without diabetes, respectively, compared to nonuremic patients. This is of particular interest since the prevalence of coronary atheroma in uremic patients was shown to be approximately 30% by autopsy and coronary angiography studies. Thus, coronary factors, i.e. atherosclerosis, and non-coronary factors may play an important role in the genesis of cardiac complications in the renal patient. In addition, renal failure recently has also be identified as a predictor of mortality in different stages of peripheral vascular disease. In particular, marked differences in the pathogenesis, morphology and course of atherosclerosis and arteriosclerosis under the conditions of renal failure have been documented. Among others increased plaque formation and particularly higher proportion and intensity of vascular calcification have been found in clinical and autopsy studies. In addition to the so-called classical or traditional risk factors, an important role for nonclassical risk factors such as microinflammation, hyperphosphatemia and oxidative stress has been documented in patients with renal failure and is discussed in detail.

Impact of renal insufficiency on outcome after contemporary percutaneous coronary intervention

BACKGROUND

End-stage renal failure is associated with poor outcomes, including increased mortality, after percutaneous coronary intervention (PCI). The effect of milder degrees of renal insufficiency (RI) is less clear, especially with routine stenting and glycoprotein IIb/IIIa inhibitor therapy, which may be of particular benefit in patients with RI.

METHODS

Clinical, angiographic, procedural, and outcome variables of 7769 consecutive patients who underwent PCI between April 2000 and July 2004 were entered into a prospective database. Inhospital mortality and morbidity were calculated according to baseline creatinine clearance. Simple and multiple logistic regression analyses were performed to determine independent predictors of mortality.

RESULTS

Baseline creatinine clearance was available in 6840 patients. It was normal (> 80 mL/min) in 3474; 1670 had mild RI (61-80 mL/min), 1111 moderate RI (41-60 mL/min), and 585 severe RI (< or = 40 mL/min). Major adverse cardiac events (MACE) (death/myocardial infarction/revascularization) increased substantially with worsening renal function (2.4% vs 3.0% vs 4.8% vs 9.7%, P < .0001), as did mortality (0.3% vs 0.7% vs 1.5% vs 6.0%, P < .0001). Multiple logistic regression analysis identified moderate RI and severe RI as independent predictors of mortality (odds ratio [OR] 3.9, P < .001; OR 12.7, P < .0001, respectively) and morbidity (MACE) (OR 1.5, P < .05; OR 2.5, P < .0001, respectively). Mild RI trended to increase the risk of mortality but did not reach statistical significance as an independent predictor of inhospital death on multiple regression analysis (OR 2.1, P = .1) and did not increase the risk of MACE (OR 1.1, P = .6).

CONCLUSIONS

Despite routine stenting and glycoprotein IIb/IIIa inhibitor therapy, RI remains an independent predictor of increased morbidity, and particularly mortality, after PCI. However, the adverse effect of truly mild RI on outcome is limited.

Cardiovascular risk in patients with mild renal insufficiency: implications for the use of ACE inhibitors

We review the evidence linking mild renal insufficiency (MRI) with increased cardiovascular risk. MRI is associated with a number of cardiovascular risk factors, including nighttime hypertension, and increased levels of lipoprotein (a), homocysteine, asymmetric dimethyl-arginine, and inflammation and insulin resistance markers and mediators. Epidemiologic evidence associates coronary artery disease and nephrosclerosis, a frequent cause of early renal insufficiency in the elderly. In a middle-aged general population MRI was found in 8% of women and 9% of men, but was not associated with cardiovascular disease. Nonetheless, in a representative sample of middle-aged British men the risk of stroke was 60% higher for the sub-group with MRI: in people at high cardiovascular risk (mostly coronary disease), the HOPE study found a 2-fold (unadjusted) or 1.4-fold (adjusted) higher incidence of cardiovascular outcomes with MRI. The combined incidence of cardiovascular death, myocardial infarction and stroke increased with the level of serum creatinine. Several studies have examined the cardiovascular risk associated with MRI in hypertension. In HDFP, as in HOPE, cardiovascular mortality increased with serum creatinine (five-fold difference in cardiovascular mortality between the lowest and the highest creatinine strata). The risk associated with renal insufficiency was independent of other classic cardiovascular risk factors. Two trials of hypertensives with low risk (HOT and a small Italian trial) found that cardiovascular outcomes approximately doubled in subjects with MRI. Another study (MRFIT) found that it was not baseline creatinine, but its increase on follow-up that predicted future cardiovascular disease. These observational data suggest that regardless of etiology MRI is a strong predictor of cardiovascular disease and is found in 10% of populations at low cardiovascular risk and in up to 30% of those at high risk. No prospective therapeutic trials aimed at reducing the cardiovascular burden in people with MRI are available. Subgroup analyses of the HOPE study indicate that angiotensin-converting enzyme (ACE) inhibition with ramipril is beneficial and does not increase the risk of such side effects as acute renal failure or hyperkalemia. Thus the frequent practice of withholding ACE inhibitors from patients with mild renal insufficiency is unwarranted, especially since MRI identifies a group at high risk that appears to benefit most from treatment. Moreover, there is evidence that ACE inhibitors improve renal outcomes in renal insufficiency. Prospective studies should test the predictive power of early renal insufficiency for cardiovascular disease and prognosis with various therapeutic options.

Hyperhomocysteinemia in patients with mild chronic renal failure

BACKGROUND

The aim of this study was to evaluate the prevalence of high plasma levels of homocysteine in patients with mild renal failure.

METHODS

Forty-six chronic renal failure patients (25 males and 21 females, mean age 55.6+/-14.4 years) were recruited for the study. Mean plasma creatinine was 2.1+/-1.0 mg/dl and mean creatinine clearance was 50.6+/-26.3 ml/min. Patients with severe renal failure were excluded. Patients were compared with a control group with normal renal function (n=35, 22 men and 13 women, mean age 50.0+/-11.5 years). Plasma homocysteine values were measured in both groups at baseline and after an oral overload of methionine.

RESULTS

Baseline homocysteine levels of patients were higher than those of controls (16.5+/-7.3 vs. 10.4+/-4.2 micromol/l, p<0.0001). Some 34 patients and 4 controls had increased plasma homocysteine levels at baseline. After the oral overload, 4 more patients had abnormally increased homocysteine levels, meaning that 83% of the patients with chronic renal failure had hyperhomocysteinemia.

CONCLUSIONS

Hyperhomocysteinemia is a very common finding among patients with mild renal failure. The need for vitamin supplementation should be evaluated in the first stage of chronic renal failure.

Folic acid supplementation to prevent adverse events in individuals with chronic kidney disease and end stage renal disease

PURPOSE OF REVIEW

This review summarizes our current understanding of the role of folate in the treatment of hyperhomocysteindemia and the prevention of cardiovascular disease in patients with chronic kidney disease and end stage renal disease. Relevant papers published between 2003 and 2004 are referenced.

RECENT FINDINGS

With the exception of one paper, recent therapeutic studies supported previous findings that folate therapy achieves only a modest reduction in plasma homocysteine and seldom normalizes homocysteine. Large prospective studies are under way to evaluate the causal relationship between homocysteine and cardiovascular risk. Recent work supports earlier data that suggested that homocysteine inflicts its damage by oxidative stress. A newly described consequence of hyperhomocysteindemia is DNA hypomethylation and alteration of gene expression. A recent study in the general population suggested that while folate may lower homocysteine it does not improve endothelial function in individuals without cardiovascular disease.

SUMMARY

The causes of hyperhomocysteindemia in renal failure remain obscure. The possibilities include impairment of both renal and extrarenal metabolic pathways by uraemia. Hyperhomocysteindemia is associated in some but not all studies with an increased risk for cardiovascular disease. A low homocysteine may reflect malnutrition and predict a poor outcome. Folate achieves modest reductions of homocysteine in some but not all studies. There are no data to support therapy with very high-dose folic acid. Hyperhomocysteindemia impairs endothelial function which is not adequately reversed by folate.

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.

Homocysteine in chronic kidney disease: Effect of low protein diet and repletion with B vitamins

BACKGROUND

Data are limited on the determinants of homocysteine (tHcy) and its relationship with nutritional indices, and dietary protein intake, in the earlier stages of chronic kidney disease (CKD).

METHODS

Levels of tHcy were assayed at baseline (N= 804) and 1 year postrandomization (N= 678) in the Modification of Diet in Renal Disease (MDRD) Study [study A, glomerular filtration rate (GFR) 25 to 55 mL/min/1.73 m(2) and study B GFR 13 to 24 mL/min/1.73 m(2)]. Participants were randomly assigned to different blood pressure targets and protein diets and all subjects received a multivitamin supplement containing 1 mg of folic acid, 10 mg pyridoxal 5'-phosphate (PLP) and 6 mug of vitamin B(12). Multivariable analyses were used to evaluate determinants of tHcy at baseline and 1 year.

RESULTS

The prevalence of hyperhomocysteinemia (tHcy >15 mumol/L) at baseline was 56% in study A and 85% in study B. Baseline tHcy was negatively correlated with measures of body fat and dietary protein intake. Folate, vitamin B(12), and GFR were the major determinants of tHcy levels. Of the patients with hyperhomocysteinemia at baseline, 49% and 24% reduced their tHcy levels at 1 year to < or =15 micromol/L in study A and study B, respectively. There was no association between dietary protein intake and odds of developing hyperhomocysteinemia at 1 year in study A (P= 0.94) or study B (P= 0.10).

CONCLUSION

Hyperhomocysteinemia is partly amenable to correction by vitamin supplementation in CKD stages 3 and 4. There is insufficient evidence to suggest that low tHcy is associated with poor nutritional status in the MDRD Study cohort. B vitamins and GFR, but not dietary protein, are the major determinants of tHcy in this patient population.

Angiotensin-converting enzyme inhibition and angiotensin II antagonism in nondiabetic chronic nephropathies

Angiotensin II (A II), the main effector of the renin angiotensin system (RAS), plays a central role in the hemodynamic and nonhemodynamic mechanisms of chronic renal disease and is currently the main target of interventions aimed to prevent the onset and progression of chronic nephropathies to end-stage renal disease (ESRD). In addition, to ameliorate glomerular hyperfiltration and size selectivity, reduce protein traffic and prevent glomerular and tubulointerstitial toxicity of ultrafiltered proteins, RAS inhibitors also limit the direct nephrotoxic effects of A II. Thus, both angiotension-converting enzyme (ACE) inhibitors (ACEi) and A II antagonists (ATA) exert a specific nephroprotective effect in both experimental and human chronic renal disease. This effect is time-dependent and is observed across degrees of renal insufficiency. Forced ACEi or ATA uptitration above doses recommended to control arterial hypertension and combined treatment with both agents allow optimization of A II inhibition and maximization of renoprotection. Multifactorial interventions combining RAS inhibition to treatments targeted also to non-RAS mechanisms could even achieve regression of glomerulosclerosis and chronic tubulointerstitial injury. Studies are needed to assess whether renal damage can be reverted to such a point that renal function could be fully prevented from worsening, and possibly improvement. The economic impact of even a partial improvement would be enormous. Moreover, chronic renal insufficiency is an independent risk factor for cardiovascular disease, and effective nephroprotection could also decrease the excess cardiovascular morbidity and mortality associated with chronic nephropathies. In patients with renal insufficiency, ACEi are even more cardioprotective than in those without and are well tolerated. Thus, RAS inhibitor therapy should be offered to all renal patients without specific contraindications, including those closer to renal replacement therapy.

Impact of renal insufficiency in patients undergoing primary angioplasty for acute myocardial infarction

BACKGROUND

The prognostic importance of renal insufficiency (RI) in patients undergoing primary percutaneous coronary intervention (PCI) for acute myocardial infarction (AMI) has not been well characterized.

METHODS AND RESULTS

PCI was performed in 2082 AMI patients without shock presenting within 12 hours of symptom onset in a prospective, multicenter randomized trial. RI was defined as a calculated (Cockroft-Gault) creatinine clearance (CrCl) < or =60 mL/min. RI at baseline was present in 18% of patients. Compared with patients without RI, patients with RI were older and were more likely to be female; to have hypertension, peripheral vascular disease, or cerebrovascular disease; and to present in heart failure. Mortality was markedly increased in patients with versus without baseline RI both at 30 days (7.5% versus 0.8%, P<0.0001) and at 1 year (12.7% versus 2.4%, P<0.0001). Mortality rates increased incrementally for every 10-mL/min decrease in baseline CrCl. By multivariate analysis, reduced baseline CrCl was a powerful independent predictor of 30-day mortality (hazard ratio, 5.77; P<0.0001) and remained associated with reduced survival at 1 year (hazard ratio, 1.98; P=0.08). Hemorrhagic complications and transfusion requirements were also increased more than 2-fold in patients with RI, as were severe restenosis (diameter stenosis > or =70%; 20.6% versus 11.8%, P=0.024) and infarct artery reocclusion (14.7% versus 7.3%, P=0.02).

CONCLUSIONS

Baseline RI in patients with AMI undergoing primary PCI is associated with a markedly increased risk of mortality, as well as bleeding and restenosis. Novel approaches are needed to improve the otherwise poor prognosis of patients with RI and AMI.

Mild renal dysfunction and subclinical cardiovascular damage in primary hypertension

The presence of mild renal dysfunction is associated with high cardiovascular morbidity and mortality rates in patients with primary hypertension. The pathophysiological mechanisms underlying this association are currently unknown. We investigated the relation between mild renal dysfunction and subclinical cardiovascular organ damage in 358 never previously treated patients with primary hypertension. Mild renal dysfunction was defined as a creatinine clearance <60 mL/min and/or the presence of microalbuminuria. Left ventricular mass index and carotid intima-media thickness were assessed by ultrasound scan. The prevalence of mild renal dysfunction, left ventricular hypertrophy, and carotid plaque was 18%, 48%, and 28%, respectively. Mild renal dysfunction was related to the presence of several risk factors, such as older age, higher blood pressure levels and lipid status, and smoking habits. Patients with the highest left ventricular mass and carotid intima-media thickness (upper quartiles) showed a higher prevalence of mild renal dysfunction (P<0.0001). After adjusting for duration of hypertension, mean blood pressure, smoking habits, and age, we found that the risk of left ventricular hypertrophy and/or carotid atherosclerosis increased by 43% with each SD reduction in creatinine clearance, and by 89% with each SD increase in albuminuria. Mild renal dysfunction is associated with preclinical end-organ damage in patients with primary hypertension. These data may help explain the high cardiovascular mortality rates reported in patients with low glomerular filtration rate or with increased albuminuria. The evaluation of creatinine clearance and urinary albumin excretion could be useful for identifying subjects at higher cardiovascular risk.

Cardiovascular risk in patients with mild renal insufficiency

We reviewed the evidence linking mild renal insufficiency (MRI) to an increased cardiovascular risk. A number of cardiovascular risk factors become prevalent with MRI, including night-time hypertension, increase in lipoprotein(a), in homocysteine, in asymmetric dimethyl-arginine (ADMA), markers and mediators of inflammation, and insulin resistance. Also, an epidemiologic association between coronary artery disease and nephrosclerosis, a frequent cause of mild renal insufficiency in the elderly, is documented. In the middle-aged, general population MRI, found in 8% of women and 9% of men, was not associated with cardiovascular disease. However, in a representative sample of middle-aged British men, the risk of stroke was 60% higher for the subgroup of people with MRI; in people at high cardiovascular risk (mostly coronary disease), the HOPE study found a 2-fold (unadjusted), or 1.4-fold (adjusted), higher incidence of cardiovascular outcomes with MRI. The incidence of primary outcome increased with the level of serum creatinine. Several studies determined the cardiovascular risk associated with MRI in hypertension. In HDFP, as in HOPE, cardiovascular mortality increased with higher serum creatinine (five-fold difference in cardiovascular mortality between the lowest and the highest creatinine strata). The risk associated with renal insufficiency was independent from other classic cardiovascular risk factors. In hypertensives with low risk, the HOT, and a small Italian trial found about a doubling in cardiovascular outcomes in MRI. However, in MRFIT, increase in follow-up creatinine predicted future cardiovascular disease, not baseline creatinine. These observational data suggest that MRI, independent of etiology, is a strong predictor of cardiovascular disease, present in 10% of a population at low risk, and up to 30% at high cardiovascular risk. No prospective therapeutic trials, aimed at reducing the cardiovascular burden in people with MRI, are available. Subgroup analyses of the HOPE study indicate that ACE inhibition with ramipril is beneficial without an increased risk for side effects like acute renal failure or hyperkalemia. Thus, the frequent practice of withholding ACE inhibitors from patients with mild renal insufficiency is unwarranted, especially since this identifies a group at high risk that appears to benefit most from treatment. In addition, there is evidence that ACE inhibitors improve renal outcomes in renal insufficiency. Prospective studies should test the predictive power of MRI for cardiovascular disease and therapeutic options.

Diagnosis and therapy of coronary artery disease in renal failure, end-stage renal disease, and renal transplant populations

Even though cardiovascular disease is the leading cause of death in patients with CRF and end-stage renal disease (ESRD), ill-conceived notions have led to therapeutic nihilism as the predominant strategy in the management of cardiovascular disease in these populations. The recent data clearly support the application of proven interventions in the general population, such as angiotensin-converting enzyme inhibitors and statins to patients with CRF and ESRD. The advances in coronary stents and intracoronary irradiation have decreased the restenosis rates in renal failure patients. Coronary artery bypass with internal mammary graft might be the procedure of choice for coronary revascularization in these patients. The role of screening for asymptomatic coronary disease is established as a pretransplant procedure, but it is unclear whether this will be applicable to all patients with ESRD. Future studies need to focus on unraveling the mechanisms by which uremia leads to increased cardiovascular events to design optimal therapies targeted toward these mechanisms and improve cardiovascular outcomes.

Why is coronary heart disease of uraemic patients so frequent and so devastating?

On September 6, 2001, Professor Fernando Valderrabano (Hospital Gregorio Marañon, Madrid) died at the age of 59 years. He was a leading figure in Spanish nephrology, a full professor of Medicine/Nephrology at the University Complutense of Madrid, and an outstanding scientist who published more than 300 articles in medical journals. He was a very intelligent and cultured person, and a man of great style who enjoyed a wide range of hobbies and interests in addition to his medical work. All his colleagues and friends mourn his passing.

Homocysteine and C-reactive protein levels in haemodialysis patients

BACKGROUND

Mild to moderate hyperhomocysteinemia is very common among patients undergoing haemodialysis. There is sufficient evidence that hyperhomocysteinemia is an independent risk factor for cardiovascular and or atheromatous disease in end stage renal failure patients. Vitamin supplementation such as vitamin B6, B12 or folate has been proposed to correct this metabolic disturbance and it is to be proved if this intervention benefit these patients, but there is no agreement whether oral folate supplementation is capable to normalize homocysteine levels in end stage renal failure patients.

METHODS

In 53 patients, undergoing haemodialysis, homocysteine levels (Hcy), folate, vitamin B12, ferritin and C-reactive protein (CRP) were estimated before and after dialysis, without folate supplementation. Thirty voluntary blood donors were used as controls to compare homocysteine levels. After four weeks of oral folate supplementation (10 mg/24 hours) the levels of homocysteine, serum folate and intra-erythrocyte folate were estimated again. Eighteen months later the survival rate of our patients was recorded and analyzed in relation to Hcy and CRP levels.

RESULTS

The results showed that haemodialysis patients exhibited, almost, fourfold higher homocysteine levels than controls (27.39 +/- 11.54 vs 7.38 +/- 3.5, t = -8.2, p = 0.000000). Folate levels, vitamin B12 and CRP increase significantly after haemodialysis where as homocysteine levels decrease (Hcy1 vs. Hcy2: z = 2.08, p = 0.03). Fourteen (14) patients suffered from coronary heart disease (CHD) and they exhibited the higher levels of homocysteine (Hcy1 vs. CHD: z = -3.4, p = 0.0006). All estimations performed revealed a negative correlation between homocysteine levels and plasma or intra-erythrocyte folate. No other variable exhibited any significant influence upon homocysteine levels. After folate supplementation homocysteine levels in the whole number of patients were unchanged (Hcy(before) vs. Hcy(after): 27.39 +/- 11.54 vs. 26.95 +/- 8.22, z = 0.3, p = 0.7, NS). When patients with homocysteine levels higher than 24 micromol/L were selected, a significant decrease was observed (34.77 +/- 9.32 vs. 30.0 +/- 8.05, z = 2.09, p = 0.02). Forty-two patients were treated with erythropoietin for their anemia and we found a positive correlation between C-reactive protein levels and rhu-Epo dose (CRP vs. Epo: r = 0.45, p = 0.002). Homocysteine levels did not exhibit any significant influence upon short-term survival (U = -0.37, p = 0.3, NS) where as CRP levels exhibit a significant influence upon short-term survival (U = 2.15, p = 0.005).

CONCLUSIONS

Homocysteine levels in haemodialysis patients are fourfold higher than healthy controls. Folate, vitamin B12 and CRP increases significantly after dialysis. Patients with coronary heart disease exhibit the highest levels of homocysteine. The homocysteine levels are inversely related with the folate levels. The exogenous folate supplementation increase the serum folate levels but decreases homocysteine only in patients with higher than mild hyperhomocysteinemia. Hcy doesn't exert any significant effect upon the short-term survival of the haemodialysis patients but CRP level is a god predictor of the short-term survival of these patients.

Does oral folic acid lower total homocysteine levels and improve endothelial function in children with chronic renal failure?

BACKGROUND

Accelerated vascular disease is common in chronic renal failure (CRF) and accounts for significant mortality and morbidity. Elevated homocysteine levels may contribute by an effect on endothelial function.

METHODS AND RESULTS

We performed a double-blind placebo-controlled randomized crossover trial of folic acid at 5 mg/m2 in 25 normotensive children 12+/-3 (7 to 17) years of age with CRF (glomerular filtration rate 26.8+/-13.2 mL/min per 1.73 m2) of noninflammatory etiology. Each subject underwent two 8-week periods of folic acid and placebo separated by an 8-week washout period. The effect of folic acid on homocysteine levels, LDL oxidation, and both endothelial-dependent and -independent vascular function were measured. After oral folic acid, serum folate levels rose from 11.7+/-4.25 to 635+/-519 microg/L (P=0.001), red cell folate levels rose from 364+/-195 to 2891+/-2623 microg/L (P<0.001), and total homocysteine levels fell from 10.28+/-4.16 to 8.62+/-2.32 micromol/L (P=0.03). In addition, there was a significant improvement in flow-mediated dilatation (FMD) (endothelial-dependent dilatation) from 7.21+/-2.8% to 8.47+/-3.01% (P=0.036) with no change in response to glyceryl trinitrate (endothelial-independent dilatation). There was no significant change in FMD or glyceryl trinitrate during the placebo phase. There was, however, no significant difference in final FMD after placebo or folic acid. Lag times for LDL oxidation were prolonged during the treatment phase (58.4+/-18.7 to 68.1+/-25.9 minutes, P=0.01).

CONCLUSION

Folic acid supplementation in children with CRF may improve endothelial function with an increased resistance of LDL to oxidation.

Moderate renal insufficiency and the risk of cardiovascular mortality: results from the NHANES I

BACKGROUND

Conflicting evidence exists concerning whether renal insufficiency is an independent risk factor for cardiovascular disease in the general population. The objective of this study was to determine whether moderate renal insufficiency was associated with total and cardiovascular mortality, independent of traditional cardiovascular risk factors, in a community sample representative of the U.S. general non-institutionalized population.

METHODS

Participants in the U.S. First National Health and Nutrition Examination Survey (NHANES I, 1974-1975) and NHANES I Epidemiologic Follow-up Study (NHEFS, 1992, 18 year follow-up) were evaluated. The primary analysis was limited to 2352 adults with complete data, and no baseline cardiovascular disease. A creatinine of 104 to 146 micromol/L in women, and 122 to 177 micromol/L in men (approximate glomerular filtration rate of 30 to 60 mL/min/1.73 m2) was defined as moderate renal insufficiency. Supplementary analyses included participants with marked renal impairment and baseline cardiovascular disease.

RESULTS

The unadjusted hazard ratio for moderate renal insufficiency compared to preserved renal function was significant for total mortality (hazard ratio 1.7; 95% confidence interval 1.3 to 2.2), and for cardiovascular mortality (2.2; 1.5 to 3.1). After adjustment for traditional cardiovascular risk factors, there was no independent association between moderate renal insufficiency and total mortality (1.0; 0.8 to 1.4), or cardiovascular mortality (1.2; 0.8 to 1.8). These results were consistent in supplementary analyses.

CONCLUSIONS

These results do not support moderate renal insufficiency as an independent risk factor for cardiovascular disease in the general population. The association between moderate renal insufficiency and cardiovascular disease, demonstrated in other epidemiologic studies, appears to be due to co-occurrence of renal insufficiency with traditional cardiovascular risk factors.

Is folate a promising agent in the prevention and treatment of cardiovascular disease in patients with renal failure?

Management of the conventional cardiovascular risk factors is insufficient to prevent the dramatic increase in atherosclerotic cardiovascular morbidity and mortality in patients with renal failure. Folate recently received attention as a potential alternative treatment option to decrease the excess cardiovascular risk in the uremic population. Folate administration is the principal treatment modality for hyperhomocysteinemia. Hyperhomocysteinemia is prevalent in more than 85% of patients with end-stage renal disease (ESRD) and is independently associated with increased odds for atherosclerotic cardiovascular disease. Several attempts have been made to normalize homocysteine levels in uremic patients with folate-based vitamin regimens. Although supraphysiologic doses of folic acid afford greater reductions in homocysteine levels than standard doses, the response to treatment is generally only partial and the large majority of ESRD patients have residual hyperhomocysteinemia. Several defects in folate metabolism have been described in uremia, which may explain the relative folate resistance in patients with renal failure, but their clinical relevance remains uncertain. It appears unlikely that the hyperhomocysteinemia in ESRD can be cured solely with folic acid supplements, since folate does not affect the prolonged plasma elimination of homocysteine, which is the primary defect in homocysteine metabolism in uremia. Folate restores endothelial dysfunction, associated with hyperlipidemia, diabetes and hyperhomocysteinemia. The beneficial effect appears to be independent of its homocysteine-lowering capacity and is possibly related to an improved bioavailability of nitric oxide. However, folate has failed to improve endothelial dysfunction in uremic patients. In the ESRD population, multiple metabolic and hemodynamic abnormalities adversely affect endothelial function. In addition, irreversible structural vascular disease already may be present. Folate should, therefore, probably be an integral part of an "endothelial protective regimen," consisting of lipid-lowering agents, antihypertensives and antioxidant vitamins and started very early in patients with renal failure. Before large-scale folate administration can be recommended, effects on hard endpoints of cardiovascular disease need to be demonstrated in randomized trials. Such trials are currently underway in patients with normal renal function at high risk for cardiovascular disease, and one trial has recently been initiated in stable renal transplant recipients.

Cardiovascular risk in patients with early renal insufficiency: implications for the use of ACE inhibitors

Patients with end-stage renal disease die from cardiovascular disease at a much younger age than people in the general population do. Here, we review the evidence linking early renal insufficiency (ERI) to an increased cardiovascular risk. A number of cardiovascular risk factors become prevalent with ERI, including night-time hypertension, increase in serum levels of lipoprotein (a), homocysteine and asymmetric dimethyl-arginine, and insulin resistance. Also, an epidemiologic association between coronary artery disease (CAD) and nephrosclerosis, a frequent cause of ERI in the elderly, is documented. In the middle-aged, general population ERI, found in 8% of women and 9% of men, was not associated with cardiovascular disease. However, in a representative sample of middle-aged British men the risk of stroke was 60% higher for the subgroup of individuals with ERI. In people at high cardiovascular risk (mostly CAD), the Heart Outcomes Prevention Evaluation (HOPE) study found a 2-fold (unadjusted) or 1.4-fold (adjusted) higher incidence of cardiovascular outcomes with ERI. The incidence of primary outcome increased with the level of serum creatinine. At least four studies have determined the cardiovascular risk associated with ERI in hypertension. In Hypertension Detection and Follow-up Program, as in HOPE, cardiovascular mortality increased with higher serum creatinine levels (5-fold difference in cardiovascular mortality between the lowest and the highest creatinine strata). In patients with hypertension with low risk, the Hypertension Optimal Treatment and a small Italian trial found about a doubling in cardiovascular outcomes in ERI. However, in the Multiple Risk Factor Intervention Trial, not baseline serum creatinine level, but its increase on follow-up predicted future cardiovascular disease. These observational data suggest that ERI, independent of etiology, is a strong predictor of cardiovascular disease, present in 10% of a population at low, and up to 30% at high, cardiovascular risk. No prospective therapeutic trials aimed at reducing the cardiovascular burden in individuals with ERI are available. Subgroup analyses of the HOPE study indicate that ACE inhibition with ramipril is beneficial without an increased risk of adverse effects like acute renal failure or hyperkalemia. Thus the frequent practice of withholding ACE inhibitors from patients with mild renal insufficiency is unwarranted, especially since this identifies a group at high risk who appears to benefit most from treatment. In addition, there is evidence that ACE inhibitors improve renal outcomes in renal insufficiency. Prospective studies should test the predictive power of ERI for cardiovascular disease and therapeutic options.

Homocysteine-lowering treatment: an overview

Elevated fasting plasma concentrations of homocysteine have a high prevalence in subjects with cardiovascular disease and have also been associated with an increased risk of atherothrombosis in most, but not all, prospective studies. The most frequent causes of hyperhomocysteinaemia are genetic defects, such as cystathionine-beta-synthase (CBS) deficiency, deficiencies of folic acid and/or vitamin B12, renal failure and interference in homocysteine metabolism by drugs or metabolic alterations. In most cases, no underlying cause can be established. Subjects with CBS deficiency are treated with pyridoxine with additional folic acid and betaine if necessary. Folic acid and vitamin B12 deficiencies should be corrected by supplementation. Increases in folate intake by dietary changes or fortification can also lower plasma homocysteine in vitamin-replete subjects with normal plasma homocysteine levels. In renal failure, folic acid treatment (1-5 mg/day) ameliorates the plasma homocysteine level in most cases but hyperhomocysteinaemia persists in the majority of patients. Primary (fasting) hyperhomocysteinaemia can be treated with folic acid (0.5-5 mg/day). An abnormal methionine-loading test identifies additional patients at risk and postmethionine-loading hyperhomocysteinaemia should be treated with a combination of pyridoxine and folic acid. In the absence of dose-effect studies, a combination of pyridoxine (50 mg) and folic acid (5 mg) is advised. Large clinical trials are currently underway to establish the role of homocysteine-lowering therapy in the secondary prevention of atherothrombotic disease. In view of the effective, cheap and safe character of therapy with folic acid and pyridoxine, a policy can be accepted to screen and treat high-risk patients until these trials have been concluded.

Associations of homocysteine, C-reactive protein and cardiovascular disease in patients with renal disease

In the past year, evidence from epidemiological studies in patients with renal disease has confirmed associations between both elevated plasma total homocysteine concentrations and the inflammatory marker C-reactive protein with an increased risk of arteriosclerotic vascular disease. However, it remains to be determined whether lowering total homocysteine or reducing inflammation will prevent 'hard' clinical outcome events such as stroke, myocardial infarction, and vascular death. Randomized trials of homocysteine lowering are currently ongoing and should further clarify the nature of the observed association between elevated total homocysteine and cardiovascular risk in patients with or without renal disease, and whether it is causal and modifiable. There are currently no known therapeutic interventions that specifically lower C-reactive protein levels in individuals or the prevalence of elevated C-reactive protein in the population but randomized trials of anti-inflammatory therapy (e.g. using selective cyclo-oxygenase-2 inhibitors) aimed at preventing cardiovascular disease are currently being planned.

Chronic renal transplantation: a model for the hyperhomocysteinemia of renal insufficiency

Renal transplant recipients (RTR) are considered representative of patients with chronic renal insufficiency (CRI) in general with respect to both reduced, progressively declining renal function, and increased risk for cardiovascular disease (CVD). In accord with this argument, we hypothesized that total (t) plasma concentrations of the putatively atherothrombotic amino acid homocysteine (Hcy) would be equivalent in RTR and CRI patients with comparable renal function. We determined plasma tHcy, folate, pyridoxal 5'-phosphate, and B12 concentrations, in addition to serum creatinine and albumin concentrations, in 86 chronic, stable RTR, and 238 patients with CRI. Within comparable ranges of serum creatinine (i.e. RTR=0.6-4.2 mg/dl; CRI=0.7-4.1 mg/dl), tHcy concentrations did not differ between the two groups (RTR=15.0 micromol/l; CRI=14.9 micromol/l, P=0.899). ANCOVA revealed that renal function, gauged as a simple creatinine measurement, was the major independent determinant of plasma tHcy concentrations, accounting for approximately 80-90% of the total variability in tHcy predicted by the full model (i.e. full model R(2)) containing, in addition to creatinine, the seven other potential explanatory variables. If controlled trials confirm that tHcy-lowering treatment reduces CVD events rates in RTR, these results should be applicable to CRI patients in general.

Beneficial influence of recombinant human erythropoietin therapy on the rate of progression of chronic renal failure in predialysis patients

BACKGROUND

Partial correction of anaemia with recombinant human erythropoietin (rHuEpo) has been shown to markedly improve the general condition and quality of life of predialysis patients, but the effects of rHuEpo therapy on blood pressure and the rate of progression of chronic renal failure (CRF) are still disputed. In particular, no study evaluated the time duration until the start of maintenance dialysis in treated patients, compared to untreated predialysis patients.

METHODS

We retrospectively evaluated the rate of decline of creatinine clearance (Delta Ccr) and the duration of the predialysis period in 20 patients with advanced CRF treated with rHuEpo (Epo+ group), and in 43 patients with a similar degree of CRF but with less marked, asymptomatic anaemia, not requiring rHuEpo therapy (Epo- group). All patients were submitted to identical clinical and laboratory surveillance. All received similar oral supplementation with B(6), B(9), and B(12) vitamins and oral iron supplementation. Maintenance dose of subcutaneous epoetin was 54.3+/-16.5 U/kg/week (median dose 3300 U/week).

RESULTS

Initial and final haemoglobin (Hb) levels were 8.8+/-0.7 and 11.3+/-0.9 g/dl in the Epo+ group, vs 10.9+/-1.2 and 9.5+/-0.9 g/dl in the Epo- group. In the Epo+ group, Delta Ccr declined from 0.36+/-0.16 during the preceding 24 months to 0.26+/-0.15 ml/min/ 1.73 m(2)/month after the start of rHuEpo therapy (P<0.05). No significant variation was observed in the Epo- group. Time duration until the start of dialysis was 16.2+/-11.9 in the Epo+ group, compared to 10.6+/-6.1 months in the Epo- group (P<0.01). Slowing of progression was observed in 10 Epo+ patients, whereas no significant variation in Delta Ccr occurred in the other 10. There was no difference in previous Delta Ccr rate, nor in Hb or blood pressure levels while on rHuEpo therapy between the two subgroups.

CONCLUSIONS

Our study affords conclusive evidence that rHuEpo therapy did not result in accelerated progression of CRF in any treated predialysis patients, nor deleterious increase in blood pressure, but instead resulted in significant slowing of progression and substantial retardation of maintenance dialysis. Such encouraging results remain to be validated in a large prospective, randomized study.

Pathophysiology and Treatment of Hyperhomocysteinemia in End-Stage Renal Disease Patients

The pathophysiology of hyperhomocysteinemia in end-stage renal disease (ESRD) patients includes impaired remethylation of homocysteine (Hcy) to methionine, inhibition of extrarenal Hcy metabolism by uremic solutes, a block in decarboxylation of cysteinesulfinic acid, impaired [adenosylmethionine]/[adenosylhomocysteine] ratio, and a probable impairment of renal Hcy metabolism and excretion. Treatment of hyperhomocysteinemia in ESRD patients includes administration of folic acid (1 - 15 mg per day). No additional effects have been observed with higher folic acid doses, folinic acid, or 5-methyltetrahydrofolate. Oral supplementation with vitamin B ₆ and vitamin B ₁₂ has no effect, but some studies reported a decrease of plasma Hcy with high intravenous vitamin doses. Effective reduction of plasma total Hcy (tHcy) in patients treated with super-flux hemodialyzers suggests the removal of uremic toxins with inhibitory activities against enzymes involved in the extrarenal Hcy metabolism.

C-reactive protein, oxidative stress, homocysteine, and troponin as inflammatory and metabolic predictors of atherosclerosis in ESRD

Mortality in patients with end-stage renal disease remains high, with cardiovascular disease accounting for half of these deaths. Novel risk factors such as inflammation, oxidative stress, hyperhomocysteinemia, and high troponin levels are associated with cardiovascular risk in the general population. While there are substantial epidemiologic data confirming that these novel risk factors are associated with cardiovascular risk in end-stage renal disease patients, a causal relationship has not been established. Inflammation is readily identified by the presence of high levels of C-reactive protein, while studies of oxidative stress are hampered by the lack of a standardized test. The cause of both is unknown. Hyperhomocysteinemia results from decreased remethylation to methionine, although vitamin supplementation only partially corrects the defect, suggesting that uremic inhibition of the enzymatic process may be important. The most promising strategies for correcting oxidative stress and hyperhomocysteinemia are vitamin E and folinic acid therapy, respectively. Troponin I appears to be a more specific marker of myocardial injury than Troponin T, but troponin T retains its ability to predict cardiovascular mortality as well as all-cause mortality. Sorting out the role of each of these risk factors may be difficult since the factors may influence each other, may increase oxidative stress, and may mediate atherosclerosis through oxidative modification of lipids.